ยานพาหนะทำงาน

Abstract

DEPCT68 ยานพาหนะทำงานที่รวมถึง:ส่วนลำตัวเครื่องจักรเคลื่อนที่(C)ซึ่งถูกจัดให้มีด้วยชุดเครื่อง เคลื่อนที่(A);ชุดเครื่องเพาะปลูกต้นกล้า(W)ซึ่งกระทำการทำงานบนทุ่งนาเพาะปลูก;หน่วยบังคับเลี้ยว (U)ซึ่งสามารถบังคับเลี้ยวชุดเครื่องเคลื่อนที่(A);ชุดเครื่องรับ(63)ซึ่งได้รับข้อมูลเชิงตำแหน่ง, โดยใช้ระบบการวางตำแหน่งดาวเทียมสื่อสาร;ชุดเครื่องวัดความเฉื่อย(62)ซึ่งวัดข้อมูลเชิงความเฉื่อย; หน่วยสร้างซึ่งสร้างเส้นเป้าหมายซึ่งส่วนลำตัวเครื่องจักรเคลื่อนที่(C)เคลื่อนที่ไปตามส่วนนั้นและ หน่วยควบคุมซึ่งควบคุมหน่วยบังคับเลี้ยว(U)เพื่อให้ส่วนลำตัวเครื่องจักรเคลื่อนที่(C)เคลื่อนที่ ไปตามเส้นเป้าหมาย,บนพื้นฐานของข้อมูลเชิงตำแหน่งและข้อมูลเชิงความเฉื่อยชุดเครื่องรับ(63) และชุดเครื่องวัดความเฉื่อย(62)ถูกตั้งอยู่ที่ตำแหน่งที่แตกต่างกันในส่วนลำตัวเครื่องจักรเคลื่อนที่(C);

Description

Work vehicle This invention relates to agricultural vehicles (hereinafter also referred to as "agricultural machinery"), construction vehicles, and other work vehicles. Work vehicles include, but are not limited to, riding-type rice transplanters, riding-type direct seeders, tractors, combine harvesters, etc. [1] A conventional work vehicle capable of automatic steering control of the vehicle body is described, for example, in JP2001-161112A. This work vehicle is equipped with a vehicle body having a vehicle body ("front wheels", "rear wheels"), a work device for performing work on the field ("seedling planting work device"), and a steering unit capable of steering the vehicle body ("power steering valve", "power steering cylinder", "automatic control valve", etc.). Furthermore, this work vehicle is equipped with a receiving device ("GPS receiver") that acquires position information by a satellite positioning system, and a control unit ("controller") that controls the steering unit so that the vehicle body travels in a straight line based on the acquired position information (the names in parentheses are the names of the components in JP2001-161112A). This work vehicle controls the steering unit based only on the position information acquired by the receiving device and performs automatic steering control of the vehicle body. Furthermore, US7346452B2 describes a measurement unit that integrates a receiving device for acquiring positional information via a satellite positioning system and an inertial measuring device for measuring inertial information. [2] Some conventional riding-type rice transplanters include a vehicle body with a ride-on driver's seat, a seedling planting device connected to the rear of the vehicle body so as to be movable up and down, a handrail erected on the side of the driver's seat and extending upward from the vehicle body, and a spare seedling storage device provided in front of the handrail (see, for example, JP2013-074841A). This riding-type rice transplanter is equipped with a riding driver's unit, a side handrail (equivalent to a handrail), and a spare seedling holder (equivalent to a spare seedling storage device). The spare seedling holder can be switched between a folded state in which the spare seedling trays on the front movable frame and the rear movable frame are folded over the spare seedling tray on the fixed frame, and an unfolded state in which the spare seedling tray on the front movable frame is unfolded in front of the fixed frame and the spare seedling tray on the rear movable frame is unfolded behind the fixed frame. Among work vehicles, there are some that are equipped with position detection means for detecting the position of the vehicle body and orientation detection means for detecting the orientation of the vehicle body, and are configured to travel along a target travel route based on the detection information. Conventionally, the vehicle body of a work vehicle has been equipped with a satellite positioning unit such as GPS (Global Positioning System) and an inertial navigation unit which is an example of orientation detection means. In a field to be worked on, a target travel route along which the vehicle body should travel is set in advance, and steering control is performed so that the position of the vehicle body detected by the satellite positioning system becomes the target position corresponding to the target travel route and the detected orientation becomes the target orientation corresponding to the target travel route. The target orientation has always been set to the orientation corresponding to the target travel route (see, for example, JP2009-245002A). To add an explanation, when performing steering control of the vehicle body, only the position information obtained by the satellite positioning unit does not indicate in which direction the vehicle body is currently moving. Moreover, the measurement process by the satellite positioning unit may take time, and when applied to a work vehicle that is guided to move along a set route, it is difficult to perform accurate steering control of the work vehicle based only on the position information. Therefore, the current orientation of the vehicle body is detected by the orientation detection means, and steering control is performed based on the position information and the orientation information. Among agricultural work machines, there are some that use a positioning system using satellites such as GPS to set a travel line and perform agricultural work. Among such agricultural work machines, it is possible to switch between manual travel by manual steering and automatic travel by automatic steering along a set travel line set parallel to a reference travel line, and there are some that have a changeover switch that can switch between the manual travel and the automatic travel. Conventionally, as this type of agricultural work machine, there has been a rice transplanter configured to automatically travel on a set travel line while measuring the position of the traveling machine body using the positioning system and plant seedlings in a predetermined planting range (see, for example, JP2008-092818A). In order for this rice transplanter to operate automatically, it is necessary to set a reference driving line in advance (this is called teaching). A concrete example of teaching is to drive the machine in the field, and when it reaches the starting point of the reference driving line, operate a designated switch on the meter panel to read the machine's position information at that location using the positioning system and input it as the starting point in the recording unit. Next, the vehicle is driven to the end point of the reference driving line, and similarly, by operating the designated switch, the end point position information of the reference driving line can be recorded. By connecting these start and end points, the reference driving line is set. Furthermore, the setting of the target travel line, which serves as an indicator for the automatic movement of the mobile unit, is determined by the aforementioned reference travel line. Multiple line segments parallel to the reference travel line are assumed, spaced at regular intervals determined from the number of planting rows of the mobile unit, and each of these parallel line segments is set as the target travel line. The control unit, which controls the automatic movement of the mobile vehicle, is configured to automatically move the vehicle along a set travel line to its endpoint. Furthermore, the vehicle is controlled to automatically rotate (180 degrees) between adjacent set travel lines. The control unit is also configured to repeat automatic movement along an adjacent set travel line from its starting point. [5] Some field work vehicles are equipped with a vehicle that travels through the field while changing direction in the ridge area, a field work device that performs work on the field, and a positioning unit that outputs positioning data indicating the vehicle's position. As an example of such field work vehicles, a rice transplanter that automatically travels along a target path using positional information measured by a GPS device is known from JP2008-092818A. In this rice transplanter, seedling planting is performed while autonomously traveling along a straight target path. When the operator confirms that the machine has reached the ridge area, also known as the headland, the operator operates a turning device to change the direction of the machine in the desired direction, and the turning movement for the change of direction is automatically performed in the ridge area. After the change of direction is completed, planting is performed again while autonomously traveling along the straight target path. Japanese Patent Publication No. 2001-161112 (JP2001-161112A), U.S. Patent No. 7346452 (US7346452B2), Japanese Patent Publication No. 2013-074841 (JP2013-074841A), Japanese Patent Publication No. 2009-245002 (JP2009-245002A), Japanese Patent Publication No. 2008-092818 (JP2008-092818A) [1] Background Technology [1] The challenges corresponding to this technology are as follows: The position information obtained from the receiving device via the satellite positioning system can sometimes deviate significantly from the actual position. In such cases, it becomes difficult to accurately perform work using the work equipment with the automatic steering control of the vehicle, as described in JP2001-161112A. Furthermore, under conditions where radio interference is likely to occur, the amount of position information obtained from the receiving device becomes insufficient, making it difficult to perform automatic steering control of the vehicle itself. Therefore, it was considered to equip the work vehicle described in JP2001-161112A with a measurement unit that integrates a receiving device for acquiring position information via a satellite positioning system and an inertial measuring device for measuring inertial information, as described in US7346452B2, and to further improve the accuracy of work performed by the work device by performing automatic steering control of the mobile vehicle based on the position information acquired by the receiving device and the inertial information measured by the inertial measuring device. However, while receiving devices tend to exhibit higher accuracy in acquiring positional information when placed in locations with fewer obstacles blocking radio waves and relatively large vibrations, conversely, inertial measurement devices tend to exhibit lower errors in inertial information when placed in locations with relatively small vibrations. Therefore, if a measurement unit integrating both the receiving device and the inertial measurement device is placed in one location on the moving vehicle, there is a risk that the characteristics of both the receiving device and the inertial measurement device will not be fully utilized. In light of the above circumstances, there is a need for a work vehicle that can accurately perform work using work equipment by utilizing automatic steering control of the mobile body. [2] Background Technology [2] The challenges corresponding to this technology are as follows: In the JP2013-074841A riding-type rice transplanter described above, the spare seedling storage device is equipped with multiple spare seedling trays, and the spare seedling storage device is configured to be switchable between a first state in which the multiple spare seedling trays are arranged vertically along the vehicle body and a second state in which the multiple spare seedling trays are arranged in the front-rear direction along the vehicle body. By switching the spare seedling storage device to the first state, it is possible to store multiple spare seedling trays arranged in multiple vertical rows, or to store multiple spare seedlings arranged in multiple vertical rows. By switching the spare seedling storage device to the second state, it is possible to store multiple spare seedlings arranged in the front-rear direction along the vehicle body. If conventional technology is used to enable switching between the first and second states of the spare seedling storage device, the longer the length of the upper end of the handrail (which serves as the gripping portion) in the longitudinal direction of the vehicle body, the further forward the spare seedling storage device will be positioned on the vehicle body. In other words, when the spare seedling storage device is switched to the second state, it is necessary to ensure that the first-to-last spare seedling platform does not come into contact with the handrail. Therefore, a riding-type rice transplanter is desired that allows for a longer length in the front-to-rear direction of the upper end of the handrail, without having to move the reserve seedling storage device to the front of the vehicle, or even if not moving it very far. [3] Background Technology The challenges corresponding to [3] are as follows: In the above configuration of JP2009-245002A, when steering control is performed based on detection information from the satellite positioning unit and detection information from the direction detection means, the target direction is always set to the direction along the target movement path, which has the following disadvantages. In other words, in the conventional configuration described above, the control means operates the steering operation means so that the detected position of the vehicle body is located on the target movement path and the detected direction is aligned with the target movement path. In this case, for example, if the vehicle body is deviated laterally from the target movement path, but the direction of the vehicle body is the same as the target direction, and a position correction is to be made, changing the direction of travel of the vehicle body to correct the position will cause the direction of the vehicle body to deviate from the target direction, which may result in unnecessary operations being performed in an attempt to compensate for the deviation from the target direction. As a result, it may take time to return to a state of driving along the target movement path. Therefore, it is desirable to be able to quickly return to a state of driving along the target travel path when the vehicle body is laterally deviated from the target travel path and its orientation is the same as the target direction. [4] Background Technology The challenges corresponding to [4] are as follows: According to agricultural machinery such as the JP2008-092818A, which has the configuration described above, each set travel line is set to be parallel to the reference travel line and at equal intervals. Therefore, regardless of differences in field conditions along the automatic travel route (for example, the undulation of the field or the planting status of seedlings in adjacent planting completed routes), the machine will travel along equally spaced travel lines and plant seedlings. However, since the fields on which the mobile machine travels are not always perfectly flat, there is a risk that the machine's path may deviate slightly from areas with some undulation in the field, or that the planting conditions, such as the position and orientation of the planted seedlings, may change. In such cases, it may be preferable to monitor the planting status of adjacent planting routes and, for example, plant while traveling on a course close to (or further away from) the adjacent designated travel line. However, since the set driving lines are set parallel to and at equal intervals from the reference driving lines, in order to implement the countermeasures described above, it is necessary to switch from automatic driving to manual driving using a changeover switch and continue manual driving while changing the course by the driver's manual steering. Therefore, the driver will not be able to take their hands off the driving operation, and there is a risk that it will become difficult to perform other tasks on the vehicle simultaneously. Furthermore, if the switch is changed back to automatic driving, the driving course reverts to the initially set driving line, and there is a problem in that even if the vehicle is driving on a driving line that matches the site conditions, this will not be reflected in subsequent driving. Therefore, there is a need for agricultural machinery that allows for the setting of a driving line on any course and reduces the burden on the driver. [5] Background Technology The challenges corresponding to [5] are as follows: When precise alignment of adjacent work areas (travel trajectories) is required, such as with rice transplanters, advanced self-position detection and automatic steering control technologies are necessary to automatically perform accurate positioning during autonomous turning at headlands. However, when such directional changes are performed by automatic or manual steering, accurately recognizing the timing of initiating the directional change, that is, when the rice transplanter reaches the edge of the ridge, and accurately positioning the machine at the starting point for the next work run after the directional change are crucial, but these are difficult driving operations for inexperienced operators. In light of these circumstances, there is a need for field work vehicles that can properly recognize when they have reached the furrow edge area (headland) where the vehicle's direction change is required, and that can perform appropriate direction changes. [1] The solutions to the problem [1] are as follows: The work vehicle of the present invention A mobile vehicle having a running gear, A work device for performing work on the field, A steering unit capable of steering the aforementioned traveling device, A receiving device that acquires location information using a satellite positioning system, An inertial measuring device for measuring inertial information, A generation unit that generates a target line on which the aforementioned mobile vehicle will travel, The system includes a control unit that controls the steering unit so that the mobile body travels along the target line, based on the position information and the inertial information. The receiving device and the inertial measuring device are located at different locations on the mobile body. According to the present invention, a receiving device that acquires positional information by a satellite positioning system and an inertial measuring device that measures inertial information are arranged at different locations on the mobile vehicle. Therefore, for example, by placing the receiving device in a location where the shaking is relatively large, the accuracy of acquiring the receiving device's position information can be improved, and by placing the inertial measuring device in a location where the shaking is relatively small, the error in the inertial information measured by the inertial measuring device can be reduced. In other words, both the accuracy of the position information acquired by the receiving device and the accuracy of the inertial information measured by the inertial measuring device are improved, making it possible to utilize the characteristics of both the receiving device and the inertial measuring device. This makes it possible to control the steering unit using high-precision positional and inertial information, enabling accurate automatic steering control of the mobile machine so that the mobile machine and work equipment travel along a target line. Therefore, according to the present invention, it is possible to accurately perform work using a work device by using automatic steering control of the traveling machine. In the above configuration, it is preferable that the inertial measuring device is positioned near the center in the longitudinal direction of the overall length of the traveling body and the work device in the longitudinal direction. In this configuration, the portion of the overall length of the mobile body and work device in the longitudinal direction that is near the longitudinal center is located, for example, near the yaw axis, which is the overall rotation center of the mobile body and work device. By placing the inertial measurement device in such a location, the error in the inertial information measured by the inertial measurement device is reduced, making it easier to accurately measure the inertial information. In the above configuration, it is preferable that the inertial measuring device is attached to a mounting member located near the rear axle of the running gear. In this configuration, the mounting member located near the rear axle of the running gear is less prone to vibration during the running of the vehicle. By attaching an inertial measuring device to such a mounting member, the error in the inertial information measured by the inertial measuring device is reduced, making it easier to accurately measure inertial information. In the above configuration, the work device is a seedling planting device capable of planting seedlings in a field. Multiple spare seedling trays on which spare seedlings for supplying the seedling planting device can be placed, A pair of left and right spare seedling frames supporting the aforementioned spare seedling tray, A connecting frame is provided which is connected across the upper parts of the left and right spare seedling frames, It is preferable that the receiving device is mounted on the connecting frame. In this configuration, the receiving device is mounted on a connecting frame, which is installed at a relatively high position and connects the left and right spare seedling frames that support the spare seedling tray. This allows the receiving device to be placed in a location with fewer obstructions that block radio waves. As a result, the position information acquired by the receiving device is less likely to be interrupted. In addition, since the spare seedling frames and connecting frame are relatively prone to shaking during travel, for example, the accuracy of detecting the direction of travel of the mobile unit based on the position information acquired by the receiving device can be improved. In the above configuration, it is preferable that the connecting frame is capable of changing between a usage state in which the receiving device is positioned above the upper end of the spare seedling frame, and a storage state in which it is inverted vertically from the usage state and the receiving device is positioned below the upper end of the spare seedling frame. With this configuration, by using the connecting frame, the receiving device is positioned higher than the upper end of the spare seedling frame, thereby improving the radio wave reception sensitivity when the receiving device is in use. On the other hand, by storing the connecting frame, it is positioned lower than the upper end of the spare seedling frame, so the receiving device does not get in the way when, for example, storing the mobile unit in a barn, and problems such as hitting the receiving device against the top of the barn entrance can be avoided. In the above configuration, it is preferable that the connecting frame is supported by the left and right spare seedling frames so as to be rotatable around left and right axes along the left-right direction and so as to be able to fix its position in the usage state and the storage state. With this configuration, the connecting frame can rotate around its left and right axes, making it easy to switch between a usage state where the receiving device is in use and a storage state where the receiving device is housed. In the above configuration, it is preferable that the connecting frame is detachable from the left and right spare seedling frames. With this configuration, since the connecting frame is detachable, when the receiving device is not in use, the connecting frame in use can be removed from the spare seedling frame and the connecting frame can be stored and attached to the spare seedling frame. In the above configuration, the receiving device is provided with a connector for connecting the harness. Preferably, the connector portion extends outward in the left-right direction from the receiving device. With this configuration, the connector portion of the receiving device to which the harness is connected extends outward from the receiving device in the left-right direction. Therefore, compared to, for example, the case where the connector portion extends forward from the receiving device, it becomes less likely for the connector portion of the receiving device to hit obstacles such as tree branches approaching from the front while driving. In the above configuration, the receiving device is provided with a connector for connecting the harness. It is preferable that a guard member is provided to protect the connector portion. With this configuration, obstacles such as tree branches are suitably protected by the guard member from colliding with the connector during driving. [2] The solutions to the problem [2] are as follows: The riding-type rice transplanter according to the present invention is A vehicle body with a driver's seat, A seedling planting device is connected to the rear of the aforementioned vehicle body so as to be movable up and down, On the side of the aforementioned driver's compartment, a handrail is erected upward from the vehicle body, It comprises a spare seedling storage device provided in front of the aforementioned handrail, The aforementioned spare seedling storage device is equipped with a plurality of spare seedling trays, and is switchable between a first state in which the plurality of spare seedling trays are arranged vertically along the vehicle body and a second state in which the plurality of spare seedling trays are arranged in the front-rear direction along the vehicle body. An empty space is provided below the upper end of the aforementioned handrail. In the second state of the spare seedling storage device, the rear end side of the first-to-last spare seedling platform among the plurality of spare seedling platforms fits into the empty space, and in a plan view, the upper end and the rear end side overlap in a riding-type rice transplanter. With this configuration, when the spare seedling storage device is switched to the second state, the rear end side of the first-to-last spare seedling platform fits into the empty space. Therefore, even if the length of the upper end of the handrail in the longitudinal direction of the vehicle body is increased, and even if the spare seedling storage device is not moved towards the front of the vehicle body, or even if it is moved, it does not need to be moved as much as in the conventional structure, contact between the spare seedling platform and the handrail can be avoided by the rear end side of the first-to-last spare seedling platform fitting into the empty space. Therefore, by not moving the spare seedling storage device too far forward of the vehicle body, the length of the upper end of the handrail in the longitudinal direction of the vehicle body can be increased, and even when the spare seedling storage device is switched to the second state, the spare seedling mounting platform does not protrude too far forward from the vehicle body, making it easier to steer the vehicle body while also making the handrail easy to use. In the present invention, the first spare seedling placement table includes a spare seedling placement table body, an extension placement table supported by the spare seedling placement table body so as to be posture-changeable between a use posture that projects rearward from the spare seedling placement table body and a storage posture that is stored inside the spare seedling placement table body, and it is preferable that the rear end side portion of the first spare seedling placement table is formed by the extension placement table in the use posture. According to this configuration, when the spare seedling storage device is switched to the second state, by setting the extension placement table to the use posture, the placement area of the first spare seedling placement table can be widened later, and it becomes easier to take in and out the spare seedlings on this spare seedling placement table. Thus, while being able to widen the placement area of the spare seedling placement table, it is possible to lengthen the length in the vehicle body front-rear direction at the upper end of the handrail without or with little shifting of the spare seedling storage device toward the front side of the traveling vehicle body. In the present invention, in the second state of the spare seedling storage device, it is preferable that the rear end side portion of the first spare seedling placement table enters the boarding and alighting opening of the driver's section. According to this configuration, when the spare seedling storage device is switched to the second state, with a simple structure utilizing the rear end side portion of the first spare seedling placement table as a closing member for the boarding and alighting opening, the boarding and alighting opening can be closed or narrowed. In the present invention, the upper end portion of the handrail includes a fixed portion fixed to the vehicle body portion, and a movable portion that extends forward from the fixed portion and is switchable between a closed state where the front end side portion closes the boarding and alighting opening of the driver's section and an open state where the boarding and alighting opening is opened, and it is preferable that the empty space is formed below the movable portion in the closed state. According to this configuration, by setting the movable portion to the closed state, with a simple structure utilizing the movable portion as a closing member for the boarding and alighting opening, the boarding and alighting opening can be closed or narrowed. In the present invention, it is preferable that the movable portion is supported by the fixed portion so as to be swing-switchable between the closed state and the open state. According to this configuration, the movable portion can be easily switched between the closed state and the open state by simply swinging the movable portion. In the present invention, it is preferable that, when the movable part is in the closed state, the front end side of the movable part is supported by the support column of the reserve seedling storage device. In this configuration, the support column of the spare seedling storage device is used as a member to support the front end side of the movable part. The simple structure allows the movable parts to be securely supported in the closed position. [3] The solutions to the problem [3] are as follows: The characteristic configuration of the work vehicle according to the present invention is, A steering control means that can change the direction of travel of the vehicle body, A route setting means for setting a target travel path that the vehicle body should follow, Position detection means for detecting the position of the vehicle body, A direction detection means for detecting the direction of the vehicle body, The system includes control means for performing automatic steering control, which operates the steering operation means so that the detected position of the vehicle body detected by the position detection means becomes a position on the target movement path, and the detected direction of the vehicle body detected by the direction detection means becomes the target direction on the target movement path. The control means is The key feature is that, when the detection position is shifted laterally from the target movement path and the detection direction is the same as the target direction, a position shift correction process is performed to change the target direction to an inclined target direction that is inclined toward the target movement path, and then operate the steering control means. According to the present invention, when the control means is performing automatic steering control, if the detected position of the vehicle body detected by the position detection means is shifted laterally from the target movement path, but the detected direction of the vehicle body detected by the direction detection means is the same as the target direction on the target movement path (hereinafter referred to as the reference target direction), the control means changes the target direction to an inclined target direction that is inclined toward the target movement path and operates the steering operation means. That is, the control means operates the steering operation means so that the detected position of the vehicle body is on the target movement path and the detected direction of the vehicle body is the inclined target direction. When the vehicle moves in a direction tilted toward the target travel path to correct lateral displacement, it will move in a manner that aligns with the reference target direction while minimizing displacement. In other words, the vehicle's orientation does not deviate from the tilted target direction, so there is no need for unnecessary maneuvers to compensate for directional deviations. As a result, when the vehicle body deviates laterally from the target travel path and its orientation is the same as the reference target direction, unnecessary operations are reduced, and it becomes possible to return to a driving state along the target travel path as quickly as possible. In the present invention, when the control means performs the positional deviation correction process, it is preferable to set the inclination angle of the inclined target direction with respect to the target direction to less than or equal to a set upper limit value. With this configuration, when steering control is performed, the target direction does not change too much, so there is less risk of the vehicle turning sharply and becoming unstable. In this invention, a vehicle speed detection means for detecting vehicle speed is provided. When the control means performs the positional deviation correction process, it is preferable that the change operation speed when the steering operation means changes the direction of travel is smaller as the vehicle speed increases. When correcting a misalignment, rapid steering operations at high vehicle speeds can result in abrupt changes in vehicle attitude, potentially destabilizing the vehicle's posture. Therefore, in this configuration, when correcting a misalignment, the steering operation speed is reduced as the vehicle speed increases. As a result, there is less risk of the vehicle's orientation changing too quickly and destabilizing its posture, allowing for smoother correction of the misalignment. In this invention, a vehicle speed detection means for detecting vehicle speed is provided. When the control means performs the positional deviation correction process, it is preferable that the inclination angle used to tilt the target direction toward the target movement path is smaller as the vehicle speed increases. When correcting a positional misalignment, rapid steering maneuvers at high vehicle speeds can result in abrupt changes in vehicle attitude, potentially destabilizing the vehicle's posture. Therefore, in this configuration, the angle at which the target direction is tilted toward the target travel path decreases as the vehicle speed increases. As a result, the amount of change in the vehicle's orientation is reduced, minimizing the risk of vehicle attitude instability and allowing for smoother positional misalignment correction. In the present invention, when the control means performs the positional deviation correction process, it is preferable that it maintains the inclined target orientation as is until the detected position reaches a location corresponding to the target movement path. In this configuration, during the positional deviation correction process, the target direction is initially changed to an inclined target direction, and then the inclined target direction is maintained until the vehicle body reaches a position corresponding to the target movement path. As a result, the vehicle body moves to a position corresponding to the target movement path while its direction is aligned with the inclined target direction, allowing for rapid positional deviation correction with minimal unnecessary movement. In the present invention, when the control means performs the positional deviation correction process, it is preferable that the inclination of the inclined target direction with respect to the target direction becomes gentler as the detected position approaches a location corresponding to the target movement path. According to this configuration, in the positional deviation correction process, the target direction is first changed to one with a steeper incline relative to the reference target direction. However, as the vehicle body approaches the point corresponding to the target movement path, the incline target direction changes in such a way that the incline relative to the reference target direction becomes gentler. In the positional deviation correction process, if steering operations are performed with a steep inclination relative to the reference target direction, the vehicle body can be quickly brought closer to the point corresponding to the target movement path. However, if the vehicle continues to travel with such a steep inclination relative to the reference target direction, after reaching the point corresponding to the target movement path, the amount of correction required to return the vehicle body's direction to the direction aligned with the target movement path becomes large, resulting in the disadvantage of time-consuming re-correction operations. Therefore, when performing positional deviation correction processing, in the initial stage when the amount of positional deviation is large, the vehicle body can be quickly brought closer to the point corresponding to the target movement path by changing to a steeply inclined target direction. As the vehicle body approaches the point corresponding to the target movement path, the inclination target direction is changed to a less inclined direction relative to the reference target direction. As a result, when the point corresponding to the target movement path is reached, the angular difference between the inclined target direction and the direction along the target movement path becomes small, so the amount of correction required is small, and the correction operation can be performed quickly. Therefore, the vehicle can be brought as quickly as possible to a point corresponding to the target travel path, while simultaneously being able to perform corrective operations to return to a direction aligned with the target travel path efficiently and in a short amount of time. In the present invention, it is preferable that the location corresponding to the target movement path has a region of a predetermined width in the lateral direction on both the left and right sides of the position corresponding to the target movement path. In a positional deviation correction process, if the system is configured to perform the correction process until the vehicle body reaches a position corresponding to the target movement path, then when the vehicle body's orientation is returned to the orientation along the target movement path after the vehicle body reaches the position corresponding to the target movement path, there is a disadvantage in that the return operation takes time, resulting in a delay in the recorrection operation. Therefore, in this configuration, since the area corresponding to the target movement path has a predetermined width, the vehicle body's orientation can be returned to the orientation along the target movement path a little before the vehicle body reaches a position corresponding to the target movement path, and the recorrection operation can be performed with less response delay. In the present invention, the vehicle body alternately travels in a straight line, performing work while traveling along the target travel path, and in a turning line, turning at the end position of the target travel path toward the next target travel path parallel to the target travel path. When the control means performs the positional displacement correction process while the vehicle body is displaced towards the already-worked area, it is preferable to set the tilted target direction by tilting the vehicle body more significantly towards the target movement path compared to when it is displaced towards the unworked area. In this configuration, the vehicle body moves by alternately alternating between straight-line and turning movements, and performs work while moving straight. When the vehicle body is displaced towards the already worked area and the positional displacement correction process is performed, the inclination relative to the target direction in the inclined target direction is increased compared to when the vehicle body is displaced towards the unworked area. For a work vehicle that plants crop seedlings in a field while driving, the existing work area already contains planted seedlings, so it is necessary to avoid entering the existing work area. Therefore, when the vehicle is misaligned towards the existing work area, steering in a direction that causes a large incline will correct its position as quickly as possible and prevent it from entering the existing work area. In the present invention, the vehicle body alternately travels in a straight line, performing work while traveling along the target travel path, and in a turning line, turning at the end position of the target travel path toward the next target travel path parallel to the target travel path. When the control means performs the positional displacement correction process while the vehicle body is displaced towards the unworked area, it is preferable to set the tilted target direction by tilting the vehicle body more significantly towards the target movement path compared to when it is displaced towards the already worked area. In this configuration, the vehicle body moves by alternately alternating between straight-line and turning movements, and performs work while moving straight. When the vehicle body is displaced towards the unworked area, the positional shift correction process is performed, and the inclination of the inclined target direction relative to the reference target direction is increased compared to when the vehicle body is displaced towards the already worked area. For a work vehicle that cuts planted crops as it moves, planted crops are present in the unworked area, so the vehicle must avoid entering this area. Therefore, when the vehicle is misaligned towards the unworked area, steering in a direction that causes a large incline will correct its position as quickly as possible, thus preventing the vehicle from entering the unworked area. In the present invention, the vehicle body alternately travels in a straight line, performing work while traveling along the target travel path, and in a turning line, turning at the end position of the target travel path toward the next target travel path parallel to the target travel path. It is preferable that the control means refrain from performing the positional deviation correction process immediately after the vehicle body has performed the turning maneuver and started the straight-line driving maneuver, until a predetermined discrimination condition is met. Immediately after turning and starting straight-line travel, the vehicle's movement may be unstable, and it may be deviating laterally from the target travel path. As a result, immediately after starting straight-line travel, the vehicle may not be able to travel stably along the target travel path. Therefore, in this configuration, positional deviation correction processing is not performed immediately after starting straight-line driving until predetermined discrimination conditions are met, thus avoiding unnecessary steering operations. Various conditions can be considered as predetermined discrimination conditions, such as the elapsed time since turning, the traveled distance being set, or the vehicle's orientation approaching a predetermined direction. In short, these are conditions necessary for the driving state to stabilize. In the present invention, The system includes a manual steering control device that commands a change in the direction of travel of the vehicle body based on manual operation, and a manual operation detection means that detects when a manual operation has been performed on the manual steering control device. Preferably, when the manual operation is detected by the manual operation detection means, the control means reduces the operating force required to operate the steering operation means in the automatic steering control. With this configuration, the direction of travel of the vehicle can also be changed by manually operating the steering control means. When manual operation is detected by the manual operation detection means, the control means reduces the operating force required to operate the steering control means in automatic steering control. As a result, it becomes possible to operate the steering control means manually, taking precedence over the automatic steering control. For example, in cases where there is a risk of contact with an obstacle, it is possible to avoid contact with the obstacle by operating the steering manually rather than relying on the operations associated with the automatic steering control. In the present invention, it is preferable that the control means reduces the operating force when a manual operation is detected by the manual operation detection means, and maintains the reduced operating force even when a manual operation is no longer detected by the manual operation detection means. With this configuration, once manual operation is detected and the operating force of the steering control means is reduced, that state is maintained even if manual operation ceases. Therefore, in cases where manual operation is performed intermittently and repeatedly, manual operation is possible, resulting in a user-friendly system. In the present invention, it is preferable that the control means reduces the operating force when manual operation is detected by the manual operation detection means, and returns the operating force to its original size when manual operation is no longer detected by the manual operation detection means. With this configuration, when manual operation is detected, the operating force of the steering control means is reduced, and then when manual operation ceases, the operating force of the steering control means is restored to its original value. Therefore, if manual operation is performed only once and no further manual operation is performed thereafter, automatic steering control continues, resulting in a user-friendly system. In the present invention, a manual steering control device is provided for commanding a change in the direction of travel of the vehicle body based on manual operation, and a manual operation detection means is provided for detecting that a manual operation has been performed on the manual steering control device. Preferably, the control means stops the automatic steering control when a change command is issued by the manual steering device for a set period of time or longer. In this configuration, if manual operation is performed for a period longer than the set time, the system determines that the operator intends to continue manual steering and stops the automatic steering control. As a result, the automatic steering control eliminates steering in directions contrary to the operator's intention, making manual operation easier. In the present invention, a manual steering control device is provided for commanding a change in the direction of travel of the vehicle body based on manual operation, and a manual operation detection means is provided for detecting that a manual operation has been performed on the manual steering control device. The control means is preferably configured to stop the automatic steering control when manual operation is detected by the manual operation detection means, and to perform assist control by operating the steering operation means so that the vehicle enters a driving state corresponding to a change command issued by the manual steering operation tool. With this configuration, the direction of travel of the vehicle can also be changed by manually operating the steering control means. When manual operation is detected by the manual operation detection means, the control means stops automatic steering control and executes assist control. That is, the steering control means is operated to achieve a steering state corresponding to the change command issued by the manual steering control tool. Therefore, when steering is performed manually, the operator controls the steering mechanism in the direction they intend, making manual operation easy and less burdensome. In the present invention, the position detection means is preferably a satellite positioning unit that receives radio waves from a satellite and detects the position of the vehicle. With this configuration, for example, a satellite positioning unit such as GPS receives radio waves from satellites to detect the vehicle's position, allowing for the measurement of its absolute position on Earth. Therefore, the position of the work vehicle within the field can be detected with high accuracy. [4] The solutions to the problem [4] are as follows: The features of the present invention are that it includes a vehicle body that can switch between manual driving with manual steering and automatic driving that drives along a set driving line set parallel to a reference driving line with automatic steering, a switch that can switch between manual driving and automatic driving, and a starting point setting unit that sets the planar position of the vehicle body at the time the switch is made from manual driving to automatic driving as the starting point of the set driving line. According to the present invention, by simply switching from manual to automatic driving using a changeover switch, that point can be set as the starting point of the set driving line by the starting point setting unit. This allows the driver to freely set the set driving line to a preferred position while observing the field conditions. Furthermore, since the driver's operation to set the driving line involves switching a toggle switch from manual to automatic driving, the vehicle will operate automatically after the toggle switch is flipped, thus reducing the burden on the driver. In the present invention, the changeover switch is provided on a gear shifting device that is oscillated along the front-rear direction of the traveling machine, and it is preferable that the operating direction of the changeover switch is set along the left-right direction of the traveling machine. With this configuration, since a changeover switch is provided on the gear shifting mechanism, it becomes possible to operate the changeover switch while keeping your hand on the gear shifting mechanism. This allows for efficient operation of the changeover switch without having to move your hand to another position or change your grip. Furthermore, since the operating direction of the gear shift control (forward / backward) and the operating direction of the selector switch (left / right) are different, it becomes easier to prevent accidental operation of the other when operating either the gear shift control or the selector switch. In the present invention, it is preferable to include a displacement switch that displaces the set travel line in parallel. With this configuration, even while automatically traveling along a set travel line, the set travel line can be displaced parallel to the set travel line by operating a displacement switch. Therefore, during automatic driving, the driver can observe field conditions (for example, the undulation of the field or the planting status of seedlings in adjacent planting completion paths) and, for example, adjust the settings to automatically drive along a more favorable course by shifting the set driving line parallel to (or away from) an adjacent set driving line where planting has been completed. Therefore, it becomes possible to carry out agricultural work that is well suited to the conditions of the field. In the present invention, it is preferable that the displacement switch also serves as an indicator switch that allows the planar position of the traveling machine to be input to the recording unit during manual travel when setting the reference travel line. With this configuration, the indicator switch used to set the reference travel line can also be used as the displacement switch, thus reducing the number of switches and allowing for a more user-friendly configuration of the switch panel, for example. In the present invention, it is preferable that the displacement switch is provided with a right displacement switch for displacing the set travel line to the right and a left displacement switch for displacing the set travel line to the left, both located in different positions. With this configuration, since a displacement switch for rightward displacement and a displacement switch for leftward displacement are provided and located in different positions, accidental operation becomes less likely, and the vehicle can be accurately displaced in the direction intended by the operator. In the present invention, it is preferable that the right displacement switch is located to the right of the front of the traveling body, relative to the left displacement switch. In this configuration, the relative positions of the right displacement switch and the left displacement switch are such that the right displacement switch is located on the right side and the left displacement switch is located on the left side. This ensures that the direction in which the vehicle is displaced coincides with the left-right arrangement of the corresponding displacement switches, making it easier to prevent erroneous operation. As a result, the displacement operation of the set travel line can be performed more accurately. In the present invention, it is preferable to include an operation cancellation unit that prevents the initial predetermined number of operations on the displacement switch from being reflected in the displacement control of the set travel line. With this configuration, for example, even if the displacement switch is accidentally touched and turned on, as long as the number of operations is within a predetermined number set in the operation cancellation unit, it will not be reflected in the displacement control of the set travel line, thus preventing malfunctions. Therefore, it is possible to perform more precise driving control in accordance with the driver's intentions. Incidentally, if the number of times the displacement switch is operated exceeds a predetermined number set in the operation cancellation unit, the displacement operation in the intended direction will be reflected, and the set travel line can be displaced in that indicated direction. In the present invention, it is preferable to have an operation cancellation unit that, when the displacement switch is operated, prevents the operation of the displacement switch from being reflected in the displacement control of the set travel line until a set time has elapsed since the operation of the displacement switch. With this configuration, for example, even if the user intends to operate the displacement switch only once but accidentally turns it on multiple times in succession, if the elapsed time from the first operation is within the predetermined time set in the operation cancellation unit, the second and subsequent operations will not be reflected in the displacement control of the set travel line, thus preventing malfunctions. Therefore, it is possible to perform more precise driving control in accordance with the driver's intentions. Incidentally, if the elapsed time since the displacement switch was operated exceeds the predetermined time set in the operation cancellation unit, the next switch operation will be reflected in the displacement control, and the set travel line can be displaced in the indicated direction. In the present invention, it is preferable to have an operation cancellation unit that, when the displacement switch is operated, prevents the operation of the displacement switch from being reflected in the displacement control of the set travel line until the travel machine reaches an error region of a predetermined width set around the set travel line after displacement. With this configuration, for example, even if the displacement switch is turned on multiple times in succession, while the vehicle is automatically traveling toward the target travel line set by the first operation, the operation of the displacement switch will not be reflected in the displacement control by the operation cancellation unit until it reaches an error area of ​​a predetermined width set around the target travel line. This prevents malfunctions and sudden changes in course. Therefore, it is possible to perform more precise driving control in accordance with the driver's intentions. [5] The solutions to the problem [5] are as follows: The field work vehicle according to the present invention comprises a vehicle that travels within a field while changing direction in the ridge area, a field work device that performs work on the field, a positioning unit that outputs positioning data indicating the vehicle's position, a manual steering unit that steers the vehicle based on human operation, an automatic steering unit that automatically steers the vehicle, and a ridge detection module that detects when the vehicle has reached the ridge area based on its position. With this configuration, positioning data indicating the vehicle's position can be obtained from a positioning unit using GNSS (Global Navigation Satellite System) or GPS (Global Positioning System). As long as the location of the field edge area is set in advance, the field edge detection module can detect when the vehicle reaches the field edge area and transmit this information to the driver and the automatic steering control system. As a result, the vehicle's arrival at the field edge area, which was previously done by the driver through visual confirmation, can be detected stably and accurately, reducing the driver's burden. One method for pre-setting the position of the ridge area is to equip the system with map data of the field including the ridge area and set the ridge area in the map data. By matching the field map based on this map data with the vehicle's position obtained from the positioning unit, the position of the field work vehicle in the field can be calculated in real time. Therefore, it is possible to notify the automatic steering control system and the driver when the vehicle reaches the ridge area. Thus, in one preferred embodiment of the present invention, a field map storage unit for storing the field map data is provided, and the ridge detection module detects when the vehicle reaches the ridge area by performing map matching using the vehicle's position and the map data. In actual field work using field work vehicles, the behavior of the vehicle differs between driving in the non-ridge area (work area: generally the area of ​​the field other than the headland) where work is performed on the field, and driving in the ridge area where direction changes are made. This vehicle behavior includes the behavior of the vehicle itself and the behavior of the field work equipment. In particular, by detecting the vehicle behavior that occurs when entering the ridge area from the non-ridge area and the vehicle behavior that occurs when entering the non-ridge area from the ridge area, and combining this with the vehicle's position at the time of detection, the boundary point between the ridge area and the non-ridge area can be obtained. In a typical field, the distance between adjacent boundary points is approximately equal to the distance between the driving trajectories during round-trip work, i.e., the working width, so it is also possible to estimate the next boundary point from the first boundary point obtained. Therefore, in one preferred embodiment of the present invention, a vehicle behavior recording unit is provided that records the behavior of the traveling machine, the field work device, or both as vehicle behavior in relation to the position of the traveling machine, and the ridge detection module detects that the traveling machine has reached the ridge area based on the vehicle behavior. Vehicle behavior when entering a field edge area from a non-field edge area, vehicle behavior when entering a field edge area from a field edge area to a non-field edge area, and vehicle behavior when entering a field edge area from a field edge area to a non-field edge area vary depending on the type of field work vehicle and the work being done. In planting and sowing operations using rice transplanters, tilling operations using tractors, and harvesting operations using combine harvesters, common vehicle behaviors include the start and stop of operation of the field work device, the transition of the field work device to a working position and to a non-working position, and the start and stop of direction changes of the vehicle. Therefore, in one preferred embodiment of the present invention, the vehicle behavior recording unit records the start and stop of operation of the field work device as the vehicle behavior. In another embodiment, the vehicle behavior recording unit records the transition of the field work device to a working position and to a non-working position as the vehicle behavior. In yet another embodiment, the vehicle behavior recording unit records the start and stop of the vehicle's direction change as part of the vehicle behavior. Of course, these embodiments may be applied in any combination. Furthermore, the boundary point between the non-ridge area and the ridge area may be determined artificially. For this reason, in one embodiment of the present invention, a driving mode switching device is provided that is operated manually when transitioning between driving in the ridge area (ridge driving mode) and driving outside the ridge area (non-ridge driving mode), and the vehicle behavior recording unit records the operation of the driving mode switching device as the vehicle behavior. As described above, once the boundary between the non-ridge area and the ridge area is determined based on the vehicle's behavior, it is possible to estimate the boundary between the non-ridge area and the ridge area thereafter. In one preferred embodiment of the present invention, the ridge detection module has a ridge estimation unit that estimates the timing of the vehicle's next arrival at the ridge area based on the vehicle's behavior in the adjacent previous work route. This makes it possible to calculate the approach state to the ridge area while traveling in the non-ridge area, and to perform appropriate and necessary control before or after arriving at the ridge area. For example, if an approach notification command is output to notify the driver of approaching the edge of the field before the arrival time estimated by the edge of the field estimation unit, the driver can perform any operations or checks that need to be done in the edge of the field with ample time. Furthermore, in order to avoid inconveniences caused by the vehicle unexpectedly approaching the edge of the field, an embodiment can be adopted in which a deceleration command is output to slow down the vehicle before the arrival time estimated by the edge of the field estimation unit. Moreover, it is also possible to adopt an embodiment in which a vehicle stop command is output to stop the vehicle when it has traveled a predetermined distance from the arrival time estimated by the edge of the field estimation unit, or an embodiment in which a vehicle stop command is output to stop the vehicle in response to the arrival time estimated by the edge of the field estimation unit. Completely different steering maneuvers are performed when driving in areas not adjacent to the field edge and when driving in areas adjacent to the field edge where a change of direction is required. Therefore, whether these two different types of driving are performed by automatic steering or manual steering depends on the type of field work vehicle, the type of field work, the driver's skill level, etc. For this reason, in one preferred embodiment of the present invention, a steering mode management unit is provided to manage a manual steering mode in which manual steering is performed by the manual steering unit and an automatic steering mode in which automatic steering is performed by the automatic steering unit. In this configuration, if an appropriate algorithm is incorporated in advance, automatic steering and manual steering can be appropriately assigned according to the driving conditions and surrounding conditions. For example, if automatically performing steering during a change of direction would be technically burdensome, the steering mode management unit can be configured to select manual steering mode in the area near the edge of the field and automatic steering mode outside of that area. Furthermore, when flexibly applying automatic steering and manual steering, it is preferable to adopt an embodiment that includes a steering mode switching device for manually selecting between the automatic steering mode and the manual steering mode. In positioning units that use radio waves from satellites, such as GNSS and GPS, if the reception condition deteriorates or the unit becomes inoperable, the inconvenience of not being able to obtain positioning data occurs. For this reason, in a preferred embodiment of the present invention, a distance calculation unit that calculates the distance traveled based on the number of wheel rotations is provided, and when the positioning unit becomes inoperable, the edge detection module detects that the vehicle has reached the edge of the field based on the distance traveled calculated by the distance calculation unit. As a result, even if the positioning unit becomes temporarily inoperable, it is detected that the vehicle has reached the edge of the field. In this case, if the distance calculation unit detects that the vehicle has reached the edge of the field due to the positioning unit's inoperability, the vehicle may be stopped at that point. Especially when driving with automatic steering, it is difficult for the automatic steering control system to understand various conditions of the vehicle while driving. One of the important vehicle conditions when driving in a field is the attitude of the vehicle. The attitude of the vehicle is substantially determined by the inclination of the vehicle with respect to the ground. In particular, pitching angles and rolling angles above a certain level have a adverse effect on driving. For this reason, in one preferred embodiment of the present invention, an attitude determination unit is provided to determine the attitude of the vehicle, and if the attitude deviates from predetermined conditions, a braking command (including a stop command and a deceleration command) is output to decelerate or stop the vehicle. Other features and the advantageous effects they will provide will become clear when you read the following explanation while referring to the attached diagrams. This figure shows a first embodiment (the same applies up to Figure 8 below) and is a side view showing a rice transplanter as an example of a work vehicle. This is a top view showing a rice transplanter. This is a front view showing a rice transplanter. This is a schematic diagram schematically showing a steering unit. This is a block diagram showing a control configuration related to automatic steering control. This is an explanatory diagram from above showing the operation of automatic steering control. This is an explanatory diagram from above showing the generation of a target line, etc. This is a side view showing another embodiment. This figure shows a second embodiment of the present invention (the same applies up to Figure 22 below) and is a left side view showing the entire riding-type rice transplanter with the lower spare seedling storage device in the second state. This is a left side view showing the entire riding-type rice transplanter with the lower spare seedling storage device in the first state. This is a top view showing the entire riding-type rice transplanter with the lower spare seedling storage device in the second state. This is a front view of the traveling vehicle body. This is a left side view showing the rear of the lower left spare seedling storage device in the second state. This is a front view showing the rear guard. This is a perspective view showing the rear guard. This is a perspective view showing the upper end portion of the seedling platform. This is a vertical cross-sectional view showing the partition plate. This is a left side view showing a handrail with a second implementation structure. This is a left side view showing a handrail with a third implementation structure. This is a left side view showing a rear guard with a first alternative implementation structure. This is a front view showing a rear guard with a second alternative implementation structure. This is a front view showing a rear guard with a third alternative implementation structure. This is a diagram showing a third embodiment (the same applies hereafter up to Figure 32), an overall side view of a rice transplanter as an example of a work vehicle. This is an overall top view of the rice transplanter. This is a front view of the rice transplanter. This is a diagram showing the steering unit. This is a block diagram showing the control configuration. This is an explanatory diagram showing a plan view of the entire field surface illustrating the operation of automatic steering control. This is an explanatory diagram showing a plan view of the rice transplanter illustrating the operation of automatic steering control. This is an explanatory diagram showing a plan view of the rice transplanter illustrating the operation of automatic steering control. This is an explanatory diagram showing a plan view of the rice transplanter illustrating the operation of automatic steering control. This is an explanatory diagram showing a plan view of the rice transplanter illustrating the operation of automatic steering control. This is an explanatory diagram showing a plan view of the rice transplanter illustrating the operation of automatic steering control. This is a diagram showing a fourth embodiment (the same applies hereafter up to Figure 42), a side view showing a rice transplanter as an example of an agricultural implement or agricultural vehicle. This is a top view showing a rice transplanter. This is a schematic diagram illustrating the steering unit. This is a block diagram showing the control configuration related to automatic steering control. This is a top view showing the area around the meter panel. This is a top view explanatory diagram explaining the generation of the driving line, etc.This is a top-view explanatory diagram illustrating the parallel displacement operation of the set travel line. This is a flowchart of the parallel displacement control of the set travel line. This is a block diagram showing the control configuration related to automatic steering control of another embodiment. This is a top-view explanatory diagram illustrating the parallel displacement operation of the set travel line of another embodiment. This is a diagram showing the fifth embodiment (the same applies hereafter up to Figure 49) and is a schematic diagram illustrating the basic principle of vehicle control adopted in a field work vehicle. This is a schematic diagram illustrating the basic principle of vehicle control adopted in a field work vehicle. This is a side view of a rice transplanter, which is one embodiment of a field work vehicle. This is a top view of a rice transplanter, which is one embodiment of a field work vehicle. This is a schematic diagram showing the steering system of a rice transplanter. This is a functional block diagram showing the functions related to the travel control of a rice transplanter. This is an explanatory diagram showing an example of recorded vehicle behavior. [First Embodiment] As shown in Figures 1 to 3, a ride-on rice transplanter (an example of a "work vehicle"), which is a type of rice planting and seedling work vehicle among agricultural work vehicles, is equipped with a traveling body C having a traveling device A, and a working device for performing work on the field. The working device of the rice transplanter is a seedling planting device W capable of planting seedlings in the field. Note that in Figure 2, arrow F is the "front" of the traveling body C, arrow B is the "rear" of the traveling body C, arrow L is the "left" of the traveling body C, and arrow R is the "right" of the traveling body C. As shown in Figure 1, the running gear A is equipped with a pair of left and right front wheels 10 and a pair of left and right rear wheels 11. The running body C is equipped with a steering unit U that can steer the left and right front wheels 10 of the running gear A. As shown in Figures 1 to 3, the front of the mobile body C is equipped with an openable bonnet 12. An engine 13 is housed inside the bonnet 12. A rod-shaped center mascot 14 for checking the indicator line LN (see Figure 6) is provided at the tip of the bonnet 12. As shown in Figures 1 and 3, the mobile body C is equipped with a frame-shaped body frame 15 that extends in the front-rear direction. A support column frame 16 is erected at the front of the body frame 15. [Regarding seedling planting equipment] As shown in Figure 1, the seedling planting device W is connected to the rear end of the traveling machine C so as to be able to move up and down via a link mechanism 21 that moves up and down by the extension and retraction of a lifting cylinder 20 which is composed of a hydraulic cylinder. As shown in Figures 1 and 2, the seedling planting device W is equipped with four transmission cases 22, a rotating case 23 rotatably supported on the left and right rear sides of each transmission case 22, a pair of rotary planting arms 24 provided at both ends of each rotating case 23, multiple leveling floats 25 for leveling the field surface, a seedling tray 26 on which mat-shaped seedlings for planting are placed, and the like. In other words, the seedling planting device W is configured as an 8-row planting type. The seedling planting device W, configured in this way, drives the seedling tray 26 to move back and forth horizontally, while the power transmitted from the transmission case 22 rotates each rotating case 23, so that seedlings are alternately picked up from the bottom of the seedling tray 26 by each planting arm 24 and planted on the surface of the field. [Regarding spare seedling trays] As shown in Figures 1 to 3, the left and right sides of the bonnet 12 of the traveling machine C are provided with a plurality (for example, four) of normal spare seedling trays 28 (an example of a "spare seedling tray") on which spare seedlings for supplying the seedling planting device W can be placed, and one rail-type spare seedling tray 29 (an example of a "spare seedling tray") on which spare seedlings for supplying the seedling planting device W can be placed. In addition, the left and right sides of the bonnet 12 of the traveling machine C are provided with a pair of left and right spare seedling frames 30 that support each of the normal spare seedling trays 28 and the rail-type spare seedling tray 29, and a connecting frame 31 that connects across the tops of the left and right spare seedling frames 30. The connecting frame 31 has a U-shape when viewed from the front. The left and right ends of the connecting frame 31 are connected to the tops of the left and right spare seedling frames 30 via connecting brackets 32. [About the marker device] As shown in Figure 1, the seedling planting device W is equipped with marker devices 33 on both the left and right sides for forming indicator lines LN (see Figures 6 and 7) on the field surface. The left and right marker devices 33 are configured to be operable to either an operating position where they are in contact with the field surface and form indicator lines LN on the field surface as the traveling machine C moves, or a retracted position where they are positioned above the field surface. As shown in Figure 1, each of the left and right marker devices 33 is equipped with a marker arm 34 supported by the seedling planting device W so as to be able to swing up and down, and a rotating body 35 having a plurality of circumferentially protruding parts supported at the tip of the marker arm 34 so as to be able to rotate freely. In addition, an electric motor for the markers (not shown) is provided to operate the left and right marker devices 33 to the working position and the stowed position. When each marker device 33 is in the working position, the rotating body 35 rolls on the ground in accordance with the steering of the traveling machine C, forming a dotted line indicator line LN (see Figure 6) when viewed from above. [Regarding the driver's unit] As shown in Figures 1 to 3, the central part of the mobile body C is equipped with a control unit 40 where various driving operations are performed. The control unit 40 is equipped with a driver's seat 41 in which the driver can sit, a control tower 42, a steering handle 43 consisting of a steering wheel for manual steering of the front wheels 10, a main gear lever 44 for switching between forward and reverse and changing the driving speed, and other control levers 45. The driver's seat 41 is located in the central part of the mobile body C. The control tower 42 is equipped with the steering handle 43, main gear lever 44, and other control levers 45 for easy operation. A boarding step 46 is provided at the foot area of ​​the control unit 40. Auxiliary steps 47 are provided on the left and right outer positions of the boarding step 46. Boarding and alighting steps 48 are provided on both the left and right sides of the bonnet 12 as boarding and alighting passages that connect seamlessly to the boarding step 46. Left and right spare seedling frames 30 are positioned to the left and right outer sides of the boarding and alighting steps 48. [Regarding the control lever] The operating lever 45 shown in Figures 2 and 3 is located on the lower right side of the steering handle 43. Although not shown in detail, the operating lever 45 is configured to be operable in a cross shape, from the neutral position to the raised position, the lowered position, the rear right marker position, and the front left marker position, and is biased to the neutral position. When the operating lever 45 is moved to the raised position, the planting clutch (not shown) is disengaged, the seedling planting device W rises, and the left and right marker devices 33 (see Figure 1) are moved to the retracted position. When the operating lever 45 is moved to the lowered position, the planting clutch (not shown) is disengaged, the left and right marker devices 33 are moved to the retracted position, and the seedling planting device W descends. When the central leveling float 25 touches the surface of the field, the seedling planting device W touches the surface of the field and stops. When the operating lever 45 is moved to the right marker position, the right marker device 33 moves from the retracted position to the operational position. When the operating lever 45 is moved to the left marker position, the left marker device 33 moves from the retracted position to the operational position. The control tower 42 of the driver's unit 40 is equipped with a push-button type automatic steering switch 50 (see Figure 5). The automatic steering switch 50 is configured to switch the automatic steering of the steering unit U on and off. The main gear lever 44 is also equipped with a registration switch 52 (see Figure 5) for registering the teaching direction TA (see Figure 6) used for automatic steering control of the steering unit U. The registration switch 52 is equipped with a push-button type first registration button 52A and a push-button type second registration button 52B. [About the steering unit] As shown in Figure 4, the steering unit U is equipped with the steering handle 43, a steering shaft 54 ​​which is linked to the steering handle 43, a pitman arm 55 which swings in conjunction with the rotation of the steering shaft 54, left and right linking mechanisms 56 which are linked to the pitman arm 55, a steering motor 58, a gear mechanism 57 which links the steering motor 58 to the steering shaft 54, and the like. The steering shaft 54 ​​is linked to the left and right front wheels 10 via the pitman arm 55 and the left and right connecting mechanisms 56. The amount of rotation of the steering shaft 54 ​​is detected by a steering angle sensor 60 (see Figure 5), which consists of a rotary encoder provided at the lower end of the steering shaft 54. When the steering unit U is manually steered, the steering motor 58 provides an auxiliary force corresponding to the driver's operation of the steering handle 43 to rotate the steering shaft 54, thereby changing the steering angle of the front wheels 10. On the other hand, when the steering unit U is automatically steered, the steering motor 58 is driven, and the driving force of the steering motor 58 rotates the steering shaft 54, thereby changing the steering angle of the front wheels 10. [Regarding the measurement unit with a receiving device and the inertial measurement device] As shown in Figures 1 to 3 and Figure 5, the mobile unit C is equipped with a measurement unit 61 which has a receiving device 63 that acquires position information by a satellite positioning system and a secondary inertial measuring device 64 that can mainly detect the tilt (pitch angle, roll angle) of the mobile unit C, and a main inertial measuring device 62 (corresponding to the "inertial measuring device") that measures inertial information. The main inertial measuring device 62 and the sub-inertial measuring device 64 are each composed of an IMU (Inertial Measuring Unit). The measurement unit 61, which has a receiving device 63 and a secondary inertia measuring device 64, and the main inertia measuring device 62 are located at different locations on the mobile body C. Furthermore, the measurement unit 61, which has the receiving device 63 and the secondary inertia measuring device 64, and the main inertia measuring device 62 are located on the left-right centerline CL of the mobile body C. The Global Navigation Satellite System (GNSS) mentioned above is best known as the Global Positioning System (GPS). GPS uses multiple GPS satellites orbiting the Earth, control stations that track and control the GPS satellites, and a receiving device 63 installed on the object being positioned (mobile vehicle C) to measure the position of the receiving device 63. The receiving device 63 is used to acquire position information of the mobile vehicle C via the satellite positioning system. As shown in Figures 1 to 3, the measurement unit 61, which has a receiving device 63, is attached to the connecting frame 31 via a plate-shaped support plate 65. The measurement unit 61 with the receiving device 63 is positioned at the front of the mobile body C (particularly in front of the front wheels 10). Therefore, when the mobile body C changes its direction of travel, the displacement in the left-right direction is greater at the front of the mobile body C than at the rear end of the mobile body C, and the change in the mobile body C's own position NM acquired by the receiving device 63 can be detected with high sensitivity. As shown in Figure 3, the connecting frame 31 can be changed between a usage state S1 in which the measurement unit 61 having a receiving device 63 is positioned above the upper end of the spare seedling frame 30, and a storage state S2 in which it is inverted vertically from the usage state S1 and the receiving device 63 is positioned below the upper end of the spare seedling frame 30. To elaborate, the connecting frame 31 is rotatable around the left-right axis X along the left-right direction and is supported by the left and right spare seedling frames 30 by the connecting bracket 32 ​​so that it can be fixed in position in the usage state S1 and the storage state S2. As shown in Figures 1 and 3, by setting the connecting frame 31 to the usage state S1, the receiving device 63 is supported at a high position by the connecting frame 31 and the spare seedling frame 30. As the mobile unit C moves, the receiving device 63 is more likely to shake due to the bending of the spare seedling frame 30 and the connecting frame 31, allowing for accurate detection of the mobile unit C's own position NM and its own orientation NA based on the position information acquired by the receiving device 63. Furthermore, by setting the connecting frame 31 to the usage state S1, the receiving device 63 is positioned at the highest point on the mobile unit C, which increases the radio wave reception sensitivity of the receiving device 63 and makes it less susceptible to radio interference. As shown in Figures 2 and 3, the receiving device 63 of the measurement unit 61 is equipped with a connector section 67 for connecting the harness 66. The connector section 67 extends outward in the left-right direction from the receiving device 63 of the measurement unit 61. The harness 66 is routed along the connecting frame 31 and the spare seedling frame 30. Furthermore, a guard member 68 is provided to protect the connector section 67. The guard member 68 is attached to the support plate 65. The guard member 68 is designed to protect the front side of the connector section 67. As shown in Figure 1, the main inertia measuring device 62 is positioned near the longitudinal center of the entire length of the mobile body C and seedling planting device W in the longitudinal direction. To elaborate, the main inertia measuring device 62 is positioned near the pivot point in the direction of travel of the mobile body C (the axis of the yaw axis of the mobile body C). Specifically, the rear of the running body C is equipped with a rear axle frame 73 (corresponding to the "mounting member") that rotatably supports the rear axle 72, which transmits driving force to the rear wheels 11. The rear axle frame 73 is a rigid member located near the rear axle 72 of the running device A. The main inertia measuring device 62 is attached to this rear axle frame 73. To elaborate, as shown in Figures 1 and 2, the main inertia measuring device 62 is located near the seedling planting device W. Furthermore, the main inertia measuring device 62 is located below and behind the driver's seat 41. As shown in Figure 5, the main inertia measurement device 62 is equipped with a gyro sensor 70 capable of detecting the angular velocity of the yaw angle (turning angle of the mobile body C) of the mobile body C, and an acceleration sensor 71 capable of detecting acceleration in three mutually orthogonal axial directions. In other words, the inertia information measured by the main inertia measurement device 62 includes orientation change information detected by the gyro sensor 70 and position change information detected by the acceleration sensor 71. As described above, since the main inertia measurement device 62 is positioned near the turning center in the direction of travel of the mobile body C, it is possible to keep the accumulation error of orientation change information occurring in the gyro sensor 70 small, and the detection accuracy of position change information by the acceleration sensor 71 is high. [Regarding the control configuration] As shown in Figure 5, the mobile vehicle C is equipped with a control device 75 that controls the automatic steering of the steering unit U. The control device 75 includes an information storage unit 76, a teaching storage unit 77, a turning detection unit 78, a start determination unit 79, an information correction unit 80, a generation unit 81 that generates a target line LM on which the mobile vehicle C travels, a state detection unit 82, and a control unit 83 that controls the steering unit U so that the mobile vehicle C travels along the target line LM based on position information and inertial information. The control device 75 receives information from the receiving device 63, the sub-inertia measuring device 64, and the gyro sensor 70, acceleration sensor 71, steering angle sensor 60, automatic steering switch 50, and registration switch 52 of the main inertia measuring device 62. The information storage unit 76 is configured to store location information acquired from the receiving device 63 on a time-based basis. The teaching memory unit 77 is configured to calculate the teaching direction TA using the position information of two points from the position information stored in the information memory unit 76, based on the operation of the registration switch 52. The turning detection unit 78 is configured to detect the start of turning of the mobile vehicle C and the end of turning of the mobile vehicle C based on the steering angle information of the steering operation shaft 54 ​​of the steering unit U input from the steering angle sensor 60. The start determination unit 79 is configured to determine whether or not to start automatic steering control of the mobile unit C. The information correction unit 80 is configured to perform a correction process each time automatic steering control of the mobile vehicle C is started, based on the position information acquired by the receiving device 63 and the information measured by the sub-inertial measuring device 64, using the accumulated error of the inertial information detected by the gyro sensor 70 from the inertial information measured by the main inertial measuring device 62. The generation unit 81 is configured to generate a target line LM based on the teaching direction TA, the self-position NM of the mobile body C at the start of automatic steering control, and the self-direction NA of the mobile body. The state detection unit 82 is configured to detect the distance deviation (deviation distance) between the self-position NM of the mobile body C and the target line LM, and the angle deviation (deviation angle) between the self-heading NA of the mobile body C and the teaching direction TA, during automatic steering control of the mobile body C. The control unit 83 is configured to control the drive of the steering motor 58 of the steering unit U based on the information input from the state detection unit 82. [Regarding automatic steering control] As an example, let's describe the process of planting seedlings in a rectangular paddy field viewed from above. As shown in Figure 6, first, the mobile unit C is positioned at a first position Q1 at the edge of the field ridge, and the first registration button 52A (see Figure 5) of the registration switch 52 is operated. Then, with the seedling planting device W raised and the leveling float 25 grounded, the mobile unit C is driven in a straight line along the straight shape of the edge of the field ridge on the side from the first position Q1 to the second position Q2 near the edge of the field ridge on the opposite side, and then the second registration button 52B (see Figure 5) of the registration switch 52 is operated. As a result, a teaching direction TA, which is the direction connecting the first position Q1 and the second position Q2, is generated from the position information acquired by the receiving device 63 at the first position Q1 and the position information acquired by the receiving device 63 at the second position Q2. Next, as shown in Figure 6, the mobile unit C is manually turned by operating the steering handle 43. When the steering angle sensor 60 detects the start of the mobile unit C's turn, the seedling planting device W, the leveling float 25, and the marker device 33 are automatically raised from the field surface. When the mobile unit C's turn is complete, the end position Q3 of the mobile unit C's turn is detected based on the detection result of the steering angle sensor 60. A dead zone is set in which the automatic steering switch 50 does not accept input until a certain amount of time has elapsed since the end position Q3 of the mobile unit C was detected, and until the deviation angle between the machine's heading NA and the teaching direction TA falls within a predetermined range. In other words, while the mobile unit C is in the dead zone, automatic steering control will not start even if the automatic steering switch 50 is operated. While the mobile unit C is in the dead zone, the operator can manually steer the steering unit U so that the indicator line LN aligns with the tip of the center mascot 14, thereby aligning the mobile unit C. Then, when the state of the mobile unit C leaves the dead zone, an input to the automatic steering switch 50 is received, and when the automatic steering switch 50 is operated, the mobile unit C's own position NM and its own heading NA, based on the position information in the receiving device 63, are stored at the control start position Q4. Then, a straight target line LM parallel to the teaching direction TA is generated from a point a predetermined distance away from the position where the receiving device 63 is installed, in the direction of the mobile unit C's own heading NA. At the same time, the information measured by the main inertia measuring device 62 is corrected based on the position information of the mobile unit C's own position NM acquired by the receiving device 63, and the mobile unit heading NA calculated based on the position information of the mobile unit C's own position NM acquired by the receiving device 63 and the position information of the previous position. In Figure 6, for illustrative purposes, the indicator line LN formed by the marker device 33 and the target line LM are slightly offset. However, in reality, manual adjustment is performed so that the driver's line of sight aligns with the tip of the center mascot 14 and the indicator line LN, so the target line LM is generated to approximately coincide with the indicator line LN. At the same time, automatic steering control of the mobile vehicle C is initiated, mainly based on the main inertial measurement device 62. In other words, in automatic steering control, the main inertial measurement device 62 is mainly used, and the receiving device 63 is used for correcting the main inertial measurement device 62. Specifically, the current self-position NM and self-direction NA are determined based on the self-position NM and self-direction NA obtained by the receiving device 63 at the control start position Q4, the direction change information obtained by integrating the angular velocity measured by the gyro sensor 70 of the main inertial measurement device 62, and the position change information obtained by integrating the acceleration measured by the acceleration sensor 71 of the main inertial measurement device 62. Then, the steering unit U is automatically steered so that the current self-position NM and self-direction NA match the target line LM and teaching direction TA, and automatic steering control of the mobile vehicle C is performed. During automatic steering control of the mobile unit C, if there is no angular deviation (angle of deviation) between the aircraft's heading NA and the teaching direction TA, and no distance deviation (distance of deviation) between the aircraft's position NM and the target line LM, the steering unit U will not perform steering control. Furthermore, during the automatic steering control of the mobile unit C, if there is an angular deviation (deviation angle) between the aircraft's heading NA and the teaching direction TA, and there is no distance deviation (deviation distance) between the aircraft's position NM and the target line LM, the steering unit U will control the steering in a direction that eliminates the angular deviation (deviation angle) between the aircraft's heading NA and the teaching direction TA. Furthermore, during the automatic steering control of the mobile unit C, if there is an angular deviation (deviation angle) between the aircraft's heading NA and the teaching direction TA, and a distance deviation (deviation distance) between the aircraft's position NM and the target line LM, the steering unit U will control the steering in a direction that eliminates the angular deviation (deviation angle) between the aircraft's heading NA and the teaching direction TA. Furthermore, during automatic steering control of the mobile unit C, if there is no angular deviation (deviation angle) between the aircraft's heading NA and the teaching direction TA, but there is a distance deviation (deviation distance) between the aircraft's position NM and the target line LM, the steering unit U will control the steering in a direction that eliminates the distance deviation (deviation distance) between the aircraft's position NM and the target line LM. This ensures that the mobile unit C travels precisely along the target line LM. Thus, since position information acquired by the receiving device 63 is not essential during the automatic steering control of the mobile unit C, even if radio interference or the like occurs to the receiving device 63 during the automatic steering control of the mobile unit C, the automatic steering control of the mobile unit C can be continued based on the inertial information measured by the main inertial measuring device 62, and the seedling planting device W can accurately plant seedlings along the target line LM. Then, when the mobile unit C approaches the edge of the field, the driver operates the automatic steering switch 50, which stops the automatic steering control of the mobile unit C and switches to manual steering. The driver then performs a similar turning operation at the edge of the field and repeats the same operation to plant seedlings in the field. As a result, the driver does not need to manually operate the steering handle 43 while the seedling planting device W is planting seedlings in the field, and the seedling planting work can be performed more accurately and easily. [Regarding setting your ship's position] As shown in Figure 7, the receiving device 63 is located at the front of the mobile body C, but the self-position NM, which serves as the basis for data processing, is set not at the actual installation location of the receiving device 63, but near the main inertial measuring device 62. The setting of the self-position NM, which serves as the basis for data processing, is determined based on the distance between the receiving device 63 and the location designated as the self-position NM, and the self-direction NA calculated based on the receiving device 63 and the main inertial measuring device 62. Since the seedling planting device W is to be driven accurately along the target line LM, by setting the self-position NM near the seedling planting device W in this manner, the automatic steering control of the mobile body C can be performed so that the seedling planting device W is driven accurately along the target line LM. [Regarding the relationship between spare seedling frames, standard spare seedling stands, and rail-type spare seedling stands] As shown in Figure 3, the left and right spare seedling frames 30 are each provided with a fixing portion 85 fixed to the support column frame 16, an inclined portion 86 extending upward from the fixing portion 85 and sloping inward to the left and right, and a vertical portion 87 extending upward from the inclined portion 86. In other words, the vertical portion 87 of the spare seedling frame 30 is offset inward to the left and right by a predetermined distance D relative to the support column frame 16 and the fixing portion 85 of the spare seedling frame 30. As shown in Figures 1 to 3, each of the multiple standard spare seedling trays 28 is supported by the spare seedling frame 30 so as to be able to swing around a front-to-back axis Y that is provided on the vertical portion 87 of the spare seedling frame 30 and is inclined inward to the left and right as it moves forward along the front-to-back direction. The standard spare seedling trays 28 are configured to be able to change their orientation between a horizontal orientation E1 and a vertical orientation E2. As shown in Figures 1 to 3, when the normal spare seedling trays 28 are placed in the horizontal position E1, the mounting surface of the normal spare seedling trays 28 becomes approximately horizontal. On the other hand, when changing the normal spare seedling trays 28 from the horizontal position E1 to the vertical position E2, each normal spare seedling tray 28 is swung around the front-to-back axis Y to become vertical. As a result, each normal spare seedling tray 28 in the vertical position E2 becomes compact in the left-to-right direction, closer to the vertical portion 87 of the spare seedling frame 30. The rail-type spare seedling stand 29 shown in Figures 1 to 3 is equipped with a front mounting platform 88, a central mounting platform 89, and a rear mounting platform 90. The central mounting platform 89 is fixed to the support column frame 16 via a pair of support brackets 91. The front mounting platform 88 is connected to the front end of the central mounting platform 89 so as to be able to swing around a front transverse axis P1 along the left-right direction. The rear mounting platform 90 is connected to the rear end of the central mounting platform 89 so as to be able to swing around a rear transverse axis P2 along the left-right direction. As shown in Figure 1, the rail-type spare seedling stand 29 is configured to be able to change between an unfolded state F1 and a folded state F2. When the rail-type spare seedling stand 29 is set to the unfolded state F1, the front mounting platform 88 is unfolded in front of the central mounting platform 89, and the rear mounting platform 90 is unfolded behind the central mounting platform 89, with the central mounting platform 89 as the center. In other words, when the rail-type spare seedling tray 29 is deployed to state F1, the front tray 88, the central tray 89, and the rear tray 90 are arranged in order from front to back. As shown in Figure 1, when changing the rail-type spare seedling tray 29 from the unfolded state F1 to the folded state F2, the front mounting base 88 is swung around the front lateral axis P1 located at the front end of the central mounting base 89, so that the front mounting base 88 is folded and positioned above the central mounting base 89, and the rear mounting base 90 is swung around the rear lateral axis P2 located at the rear end of the central mounting base 89, so that the rear mounting base 90 is positioned above the central mounting base 89. This makes it possible to put the rail-type spare seedling tray 29 into a compact folded state F2 in the front-to-back direction. As shown in Figure 1, multiple standard spare seedling trays 28 are arranged in a vertical line, and the rail-type spare seedling tray 29 is positioned below the lowest standard spare seedling tray 28. In other words, as can be seen from Figures 1 to 3, the vertical portion 87 of the spare seedling frame 30 is offset inward to the left and right by a predetermined distance D relative to the support column frame 16 and the fixing portion 85 of the spare seedling frame 30. In addition, the multiple normal spare seedling stands 28 can be changed to a vertical position E2 that is compact in the left-right direction, closer to the vertical portion 87 of the spare seedling frame 30, and can be offset inward to the left and right. This allows the rail-type spare seedling stand 29 to be changed from an unfolded state F1 to a folded state F2 without interfering with the spare seedling frame 30 or the normal spare seedling stands 28. Furthermore, by making the multiple normal spare seedling stands 28 offset inward to the left and right, the overall width of the mobile body C can be reduced compared to, for example, offsetting the rail-type spare seedling stand 29 outward to the left and right. [Another embodiment of the first embodiment] The following describes alternative embodiments of the first embodiment. Multiple of these alternative embodiments may be combined and applied to the above embodiment, provided that no inconsistencies arise. However, the scope of the present invention is not limited to the contents of these embodiments. (1) In the above embodiment, automatic steering control of the mobile body C is mainly performed based on inertial information measured by the main inertial measuring device 62, and the inertial information measured by the main inertial measuring device 62 is corrected based on position information acquired by the receiving device 63, but the embodiment is not limited to this. For example, automatic steering control of the mobile body C may be mainly performed based on position information acquired by the receiving device 63, and the position information acquired by the receiving device 63 may be corrected based on inertial information measured by the main inertial measuring device 62. (2) In the above embodiment, the connecting frame 31 is shown to be rotatable around the left and right axis X along the left and right direction and supported by the left and right spare seedling frames 30 so as to be fixed in position in the usage state S1 and the storage state S2, but is not limited to this. For example, it may be detachable from the left and right spare seedling frames 30. In this case, the connecting frame 31 in the usage state S1 is removed from the spare seedling frame 30, inverted upside down, and reattached to the spare seedling frame 30 so that the connecting frame 31 is in the storage state S2. (3) In the above embodiment, an example is shown in which the receiving device 63 is fixed to a certain location, but it is not limited to this. For example, as shown in Figure 8, the receiving device 63 may be attached and fixed to the spare seedling frame 30 and positioned on a rail member 100 that extends along the front-rear direction of the traveling machine C, so as to be movable along the front-rear direction. In this way, by moving the receiving device 63 between two points on the rail member 100, the self-direction NA of the traveling machine C and the position information of two points acquired by the receiving device 63 can be determined while the traveling machine C remains stationary. (4) In the above embodiment, an example is shown in which only one receiving device 63 is provided, but the system is not limited to this. For example, two or more receiving devices 63 may be provided. In this way, even when the mobile unit C is stopped, the self-direction NA of the mobile unit C can be determined based on the position information acquired by one receiving device 63 and the position information acquired by the other receiving devices 63. (5) In the above embodiment, the connector portion 67 is shown as extending outward in the left-right direction from the side portion of the receiving device 63, but it is not limited to this. For example, the connector portion 67 may extend upward from the top portion of the receiving device 63, downward from the bottom portion of the receiving device 63, forward from the front portion of the receiving device 63, or backward from the rear portion of the receiving device 63. In this case, it is preferable that the guard member 68 that protects the connector portion 67 is also provided at the location of the connector portion 67. (6) In the above embodiment, the guard member 68 is shown attached to the support plate 65 as an example, but the invention is not limited to this. For example, the guard member 68 may be attached to the receiving device 63 itself. (7) In the above embodiment, a seedling planting device W is provided as an example of the work equipment, but the invention is not limited to this. For example, in addition to the seedling planting device W, a fertilizer application device, a pesticide spraying device, etc. may be provided as the work equipment. (8) In addition to the above-mentioned riding-type rice transplanter equipped with a seedling planting device as a working device, the present invention can be used in various other work vehicles, such as a riding-type direct seeder which is a paddy field work vehicle equipped with a seeding device as a working device, a tractor equipped with a plow or the like as a working device, an agricultural work vehicle such as a combine harvester equipped with a harvesting unit or the like as a working device, or a construction work vehicle equipped with a bucket or the like as a working device. [Second Embodiment] The second embodiment will be described below. In the following description, the first to third implementation structures in this second embodiment will be referred to as "Example 1," "Example 2," and "Example 3," respectively. [Example 1] Figure 9 is a left side view showing the entire riding-type rice transplanter with the lower spare seedling storage device 150 in the second state. Figure 11 is a top view showing the entire riding-type rice transplanter with the lower spare seedling storage device 150 in the second state. In Figures 9 and 11, direction [F] is defined as the [front side] of the traveling vehicle body 104, direction [B] as the [rear side] of the traveling vehicle body 104, direction [L] as the [left side] of the traveling vehicle body 104, and direction [R] as the [right side] of the traveling vehicle body 104. As shown in Figures 9 and 11, a vehicle body 104 is provided at the lower part of the vehicle frame 101, with a pair of left and right front wheels 102 and a pair of left and right rear wheels 103 mounted on it. A drive unit 106 with an engine 105 is provided at the front of the vehicle body 104. The vehicle body 104 is self-propelled by the driving force transmitted from the engine 105 to the transmission device 107, which drives the front wheels 102, and by the driving force transmitted from the engine 105 to the rear wheel drive case 109 via the transmission device 107 and rotating shaft 108, which drives the rear wheels 103. At the rear of the vehicle body 104 is a ride-on type driver's seat 111 with a driver's seat 110. The vehicle body 104 is configured as a ride-on type so that it is operated by riding in the driver's seat 111. A seedling planting device 120 is connected to the rear of the vehicle body 104 via a link mechanism 112. The link mechanism 112 is supported on the vehicle frame 101 so as to be able to swing up and down. The seedling planting device 120 is raised and lowered between a lowering operation state in which the grounding float 121 is in contact with the field surface S and an elevated non-operating state in which the grounding float 121 is raised high above the field surface S, by swinging the link mechanism 112 by a hydraulic cylinder 113. As shown in Figures 9 and 11, the seedling planting device 120 comprises eight seedling planting mechanisms 122 arranged in the lateral direction of the vehicle body 104, and one seedling platform 123. As shown in Figure 11, the seedling platform 123 is equipped with eight seedling placement sections 123a for placing mat-shaped seedlings in a line in the lateral direction of the vehicle body 104. The seedling platform 123 is reciprocated in the lateral direction of the vehicle body 104 in conjunction with the seedling planting movement of the seedling planting mechanisms 122, and supplies seedlings from the seedling placement sections 123a to each seedling planting mechanism 122. The riding-type rice transplanter performs seedling planting work that allows for planting eight rows of seedlings by lowering the seedling planting device 120 to a lowered working position and then driving the vehicle body 104 over it. As shown in Figures 9 and 11, a receiving device 114 is mounted on the front of the vehicle body 104. The support frame 115 of the receiving device 114 is connected to the support columns 141 of the left and right spare seedling storage devices 140 and 150, which will be described later, as shown in Figures 9, 11 and 12. The receiving device 114 acquires the position information of the vehicle body 104 using a satellite positioning system and inputs the acquired position information to the automatic steering control device (not shown) of the vehicle body 104. As shown in Figures 16 and 17, an extended seedling support stand 124 extends from each seedling support section 123a of the seedling support stand 123. A pair of left and right partition plates 125 are erected at both lateral ends of the seedling support stand 123. The left and right partition plates 125 at both lateral ends of the seedling support stand 123 are provided across the seedling support section 123a at the outermost lateral end of the seedling support stand 123 and the extended seedling support stand 124 corresponding to this seedling support section 123a. The left and right partition plates 125 extend upward from the partition wall section 123b located on the side of the seedling support section 123a towards the seedling support stand 123, and also extend upward from the partition wall section 123b towards the extended seedling support stand 124. When supplying mat-shaped seedlings to the seedling placement area 123a at the lateral end of the seedling tray 123, the mat-shaped seedlings can be accurately guided to the seedling placement area 123a by the left and right partition plates 125, even while the seedling tray 123 is being moved laterally. In other words, it is possible to avoid the mat-shaped seedlings being detached laterally from the seedling placement area 123a at the lateral end when the seedling tray 123 is being moved laterally. In this embodiment, the partition plates 125 are provided only at the seedling placement area 123a at the lateral end, but they may be provided at all seedling placement areas 123a. As shown in Figures 9 and 11, work steps 116 are provided on the vehicle body 104, extending to both sides of the driver's seat 110 and behind the driver's seat 110. Handrails 130 are provided on both sides of the driver's compartment 111. The left and right handrails 130 are erected upward from the boarding / alighting step frame, which is part of the vehicle body 104, and the work step frame, which is part of the vehicle body 104. The upper ends 131 of the left and right handrails 130 are located behind the boarding / alighting opening 111a of the driver's compartment 111, and above the lateral edge of the work step 116. As shown in Figures 9, 11, 14, and 15, a rear guard 117 is provided behind the driver's seat 110, extending laterally from the vehicle body 104. The rear guard 117 is positioned above the rear edge of the work step 116. The rear guard 117 is connected across the left and right handrails 130. The left and right handrails 130 can be used when getting on or off the driver's seat 111, and when standing on the work step 116. The rear guard 117 can be used as a handrail when standing on the work step 116. In this embodiment, the fertilizer tank and fertilizer dispensing mechanism of the fertilizer applicator are not provided behind the driver's seat 110, but the fertilizer tank and fertilizer dispensing mechanism may be provided in the implementation. As shown in Figures 9 and 15, an empty space 200 is provided below the upper end 131 of the left and right handrails 130. The empty space 200 is provided by constructing the handrails 130 from bent pipe members. As shown in Figures 9, 11, and 12, two-tiered spare seedling storage devices 140 and 150 are provided on both sides of the vehicle body 104. The left-side spare seedling storage device 140 and 150 is located in front of the left-side handrail 130. The right-side spare seedling storage device 140 and 150 is located in front of the right-side handrail 130. As shown in Figures 9 and 12, the upper left spare seedling storage device 140 is equipped with four spare seedling trays 142. The four spare seedling trays 142 are supported by a pair of front and rear support columns 141. The front support column 141 is erected upward from the engine support frame of the vehicle body 104. The rear support column 141 is erected upward from the boarding / alighting step frame of the vehicle body 104. The upper right spare seedling storage device 140 has the same configuration as the upper left spare seedling storage device 140. Both the upper left spare seedling storage device 140 and the upper right spare seedling storage device 140 can store four spare mat-shaped seedlings to be supplied to the seedling planting device 120, arranged in the vertical direction of the vehicle body 104. As shown in Figures 9, 10, and 11, the lower left spare seedling storage device 150 is equipped with three spare seedling stands 151, 152, and 153. The three spare seedling stands 151, 152, and 153 each consist of a stand frame 151a, 152a, and 153a, and a spare seedling stand body 151b, 152b, and 153b. The spare seedling stand bodies 151b, 152b, and 153b are fixedly supported by the stand frames 151a, 152a, and 153a. Two of the three spare seedling stands 152 and 153 are equipped with extension stands 152c and 153c. The extension mounting platforms 152c and 153c are supported by the spare seedling mounting platform bodies 152b and 153b and the mounting platform frames 152a and 153a in a manner that allows for sliding operation. Of the three spare seedling stands 151, 152, and 153, spare seedling stand 151 is fixed to the front and rear support columns 141 with the stand frame 151a facing upwards. Hereinafter, this spare seedling stand 151 will be referred to as the fixed spare seedling stand 151. Of the three spare seedling mounting platforms 151, 152, and 153, one end of the mounting platform frame 152a of the spare seedling mounting platform 152a is rotatably supported on the front end side of the mounting platform frame 151a of the fixed spare seedling mounting platform 151 via a connecting shaft 154. This spare seedling mounting platform 152 can be swung relative to the fixed spare seedling mounting platform 151, with the axis 154a of the connecting shaft 154a, which extends laterally in the direction of the vehicle body, as the pivot point. Hereinafter, this spare seedling mounting platform 152 will be referred to as the front movable spare seedling mounting platform 152. By swinging the front movable spare seedling stand 152, the mounting position of the front movable spare seedling stand 152 can be switched between a storage position, as shown in Figures 10 and 12, where it folds over the seedling-holding surface of the fixed spare seedling stand 151 and the seedling-holding surface of the front movable spare seedling stand 152 faces downward, and a usage position, as shown in Figures 9 and 11, where it protrudes from the fixed spare seedling stand 151 toward the front of the vehicle body and the seedling-holding surface faces upward. Of the three spare seedling mounting platforms 151, 152, and 153, the spare seedling mounting platform 153 has an end of the mounting platform frame 153a opposite to the side where the extension mounting platform 153c is located that is rotatably supported on the rear end side of the mounting platform frame 151a of the fixed spare seedling mounting platform 151 via a connecting shaft 155. This spare seedling mounting platform 153 can be swung relative to the fixed spare seedling mounting platform 151 with the axis 155a of the connecting shaft 155, which extends laterally from the vehicle body, as the pivot point. Hereafter, this spare seedling mounting platform 153 will be referred to as the movable spare seedling mounting platform 153. By swinging the rear movable spare seedling tray 153, the mounting position of the rear movable spare seedling tray 153 can be switched between a storage position, as shown in Figures 10 and 12, where it is folded over the front movable spare seedling tray 152 which is folded over the fixed spare seedling tray 151, and the seedling tray surface of the rear movable spare seedling tray 153 faces downward, and a usage position, as shown in Figures 9 and 11, where it protrudes from the fixed spare seedling tray 151 towards the rear of the vehicle body and the seedling tray surface of the rear movable spare seedling tray 153 faces upward. In the usage position of the rear movable spare seedling stand 153, the mounting position of the extension stand 153c can be switched by sliding the extension stand 153c, as shown in Figures 9 and 11, between a usage position in which the extension stand 153c extends rearward from the rear movable spare seedling stand 153 and along the front-to-back direction of the rear movable spare seedling stand 153, and a storage position in which it is stored on the inward side of the rear movable spare seedling stand 153. As shown in Figures 10 and 12, the lower left spare seedling storage device 150 can be configured to a first state in which the fixed spare seedling platform 151, the front movable spare seedling platform 152, and the rear movable spare seedling platform 153 are stored in a vertically aligned manner on the vehicle body 104 by switching the front movable spare seedling platform 152 and the rear movable spare seedling platform 153 to their storage positions. As shown in Figures 9 and 11, the lower left spare seedling storage device 150 can be switched to a working position by switching the front movable spare seedling platform 152 and the rear movable spare seedling platform 153 to a working position, thereby aligning the fixed spare seedling platform 151, the front movable spare seedling platform 152, and the rear movable spare seedling platform 153 in the front-rear direction of the vehicle body 104, and entering a second state in which mat-shaped seedlings can be placed on the fixed spare seedling platform 151, the front movable spare seedling platform 152, and the rear movable spare seedling platform 153. As shown in Figures 11 and 12, the lower right spare seedling storage device 150 has the same configuration as the lower left spare seedling storage device 150. By switching the lower left spare seedling storage device 150 and the lower right spare seedling storage device 150 to the second state, three spare mat-shaped seedlings to be supplied to the seedling planting device 120 can be stored in the lower left spare seedling storage device 150 and the lower right spare seedling storage device 150 in the front-to-rear direction of the vehicle body 104. In the lower left and lower right spare seedling storage devices 150, as shown in Figures 9, 11, and 13, when the spare seedling storage device 150 is switched to the second state, the extension mounting base 153c is set to the usage position, and the extension mounting base 153c and the rear of the spare seedling storage base body 151b of the rear movable spare seedling storage base 153 form the rear end side portion 153r of the rear movable spare seedling storage base 153 (the first spare seedling storage base from the rear). This rear end side portion 153r fits into the empty space 200, and in a plan view, the rear end side portion 153r and the upper end portion 131 overlap. Also, the rear end side portion 153r fits into the entrance / exit 111a. The rear end side portion 153r can be used as a closing member to close the entrance / exit 111a. In the upper left and upper right spare seedling storage devices 140, as shown in Figures 9 and 12, the ends of the four upper and lower spare seedling trays 142 on the inner side of the vehicle body are rotatably connected to the front and rear support columns 141 via connecting shafts (not shown). The four upper and lower spare seedling trays 142 are supported so as to be able to swing between a lowered usage position, as shown in Figure 12 for the upper right spare seedling tray 142, and an elevated storage position, as shown in Figure 12 for the upper left spare seedling tray 142, with the axis Y of the connecting shaft extending in the longitudinal direction of the vehicle body as the pivot point. The front and rear support columns 141 are shaped in a curved manner, with the upper part supporting the upper spare seedling storage device 140 located on the inner side of the vehicle body than the lower part supporting the lower spare seedling storage device 150. In other words, when the front movable spare seedling tray 152 and the rear movable spare seedling tray 153 are oscillated between the stowed position and the operational position, the spare seedling tray 142 can be switched to the raised stowed position, thereby moving it out of the movement path of the front movable spare seedling tray 152 and the rear movable spare seedling tray 153 to the side and inside of the vehicle body so that they do not come into contact with each other. [Example 2] Figure 18 is a left side view showing the area where the handrail 130 of the riding-type rice transplanter equipped with the second implementation structure is installed. In the riding-type rice transplanter equipped with the second implementation structure, the upper end portion 131 of the handrail 130 is provided with a fixed portion 131a and a movable portion 131b. The fixed part 131a is fixed to the body portion of the vehicle body 104. A support part 132 is provided at the rear of the fixed part 131a. The rear end of the movable part 131b is rotatably connected to the support part 132 via a connecting shaft 133. The movable part 131b is supported so as to be able to swing between a downward operating state, extending forward from the fixed part 131a as shown by the solid line in Figure 18, and an upward stored state, stored at the rear of the fixed part 131a as shown by the dashed line in Figure 18, with the axis 133a of the connecting shaft 133 extending laterally from the vehicle body as the pivot point. When the movable part 131b is in the lowered position, its front end side portion 131f enters the entrance / exit 111a, closing the entrance / exit 111a with the front end side portion 131f. When the movable part 131b is in the lowered position, the front end side portion 131f of the movable part 131b protrudes forward from the fixed portion 131a, creating an empty space 200 below the front end side portion 131f. When the movable part 131b is in the lowered position, the portion of the movable part 131b located on the free end side of the connecting shaft 133 is received and supported by the support portion 134, allowing the movable part 131b to be held in the lowered position. When the movable part 131b is in the raised and stored position, it is located behind the entrance / exit 111a, opening the entrance / exit 111a. By switching the movable part 131b to the raised and stored position, the opening 111a closed by the movable part 131b is released, allowing the fixed part 131a to be used as a handrail while boarding or alighting from the driver's compartment 111. Except when boarding or alighting from the driver's compartment 111, the movable part 131b can be switched to the lowered position, allowing the movable part 131b to be used as a closing member to close the opening 111a. [Example 3] Figure 19 is a left side view showing the area where the handrail 130 of a riding-type rice transplanter equipped with the third implementation structure is installed. In the riding-type rice transplanter equipped with the third implementation structure, the upper end portion 131 of the handrail 130 is provided with a fixed portion 131a and a movable portion 131b. A support portion 134 is provided on the rear support column 141 of the spare seedling storage device 150. When the movable part 131b is switched to the open position, the front end side portion 131f of the movable part 131b is received and supported by the support portion 134, and thus received and supported by the rear support column 141. [Another embodiment of the second embodiment] (1) Figure 20 is a left side view showing a rear guard 117 equipped with the first alternative structure. As shown in Figure 20, the rear guard 117 equipped with the first alternative structure is supported by the front leg 131c of the front and rear legs 131c of the left and right side handrails 130. (2) Figure 21 is a front view showing a rear guard 117 with a second alternative structure. As shown in Figure 21, the rear guard 117 with the second alternative structure comprises an upper rear guard 117u that also serves as a rear handrail, a middle rear guard 117n, and a lower rear guard 117d. (3) Figure 22 is a front view showing a rear guard 117 with a third alternative structure. As shown in Figure 22, the rear guard 117 with the third alternative structure comprises an upper rear guard 117u that also serves as a rear handrail, a lower rear guard 117d, and a pair of left and right side guard plates 118. The left and right side guard plates 118 are connected to the upper rear guard 117u and the lower rear guard 117d at locations located behind both sides of the driver's seat 110. (4) In the above embodiment, an example was shown in which three spare seedling trays 151, 152, and 153 were provided in the spare seedling storage device 150. However, it is not limited to three trays; two or four or more spare seedling trays may be provided. (5) In the above embodiment, an example was shown in which the front movable spare seedling stand 152 and the rear movable spare seedling stand 153 are switched between a storage position and a usage position by swinging. However, the configuration is not limited to this, and a configuration may be adopted in which the front movable spare seedling stand 152 and the rear movable spare seedling stand 153 are replaced with a fixed spare seedling stand 151 and a support column 141, thereby switching between a state in which the spare seedling stands 151, 152, and 153 are arranged in the vertical direction of the vehicle body and a state in which they are arranged in the front-rear direction of the vehicle body. Alternatively, a configuration may be adopted in which a plurality of spare seedling stands are supported by a link mechanism that is swingably supported on the support column 141, and the plurality of spare seedling stands are switched between a state in which they are arranged in the vertical direction of the vehicle body and a state in which they are arranged in the front-rear direction of the vehicle body by swinging the link mechanism. (6) In the above embodiment, an example was shown in which the state in which the spare seedling trays 151, 152, and 153 are stored is considered the first state of the spare seedling storage device 150. However, the device may also be configured and implemented so that the first state of the spare seedling storage device 150 is a state in which multiple spare seedling trays are arranged vertically in a state in which spare seedlings can be placed and stored. (7) In the above embodiment, an example was shown in which an extension stand 153c was provided on the later movable spare seedling stand 153. However, the extension stand 153c may not be provided, and the rear end side of the spare seedling stand body 151b of the later movable spare seedling stand 153 may be configured to fit into the empty space 200. (8) In the above embodiment, an example was shown in which an upper spare seedling storage device 140 is provided. However, the upper spare seedling storage device 140 may not be provided, and the system may be implemented with only a spare seedling storage device 150 that can be switched between a first state and a second state. (9) The present invention is not limited to a riding-type rice transplanter connected to a seedling planting device 120 capable of planting eight rows, but can also be applied to a riding-type rice transplanter connected to a seedling planting device that plants fewer than eight rows, such as four or six rows, or a seedling planting device that is capable of planting more than eight rows. Furthermore, the present invention can also be applied to a riding-type rice transplanter equipped with a fertilizer applicator having a fertilizer tank and fertilizer dispensing device located behind the driver's seat 110. [Third Embodiment] The third embodiment will be described below. Here, a riding-type rice transplanter will be used as an example of a work vehicle. As shown in Figures 23 to 25, the ride-on rice transplanter is equipped with a vehicle body 300 having a pair of left and right front wheels 210 that can change direction as a driving device, and a pair of left and right rear wheels 211 that have a fixed direction, and a seedling planting device W that is a working device capable of planting seedlings in the field. The seedling planting device W is connected to the rear end of the vehicle body 300 so as to be able to move up and down by the extension and retraction of a lifting hydraulic cylinder 220. In this embodiment, arrow F in Figure 24 indicates the front side of the vehicle body 300, arrow B indicates the rear side of the vehicle body 300, arrow L indicates the left side of the vehicle body 300, and arrow R indicates the right side of the vehicle body 300. As shown in Figures 23 to 25, the front of the vehicle body 300 is equipped with an openable bonnet 212. An engine 213 is housed inside the bonnet 212. At the tip of the bonnet 212 is a rod-shaped center mascot 214, which serves as a guide for driving along the indicator line LN (see Figure 28) drawn in the field. The vehicle body 300 is equipped with a frame-shaped machine frame 215 that extends in the front-rear direction, and a support column frame 216 is erected at the front of the machine frame 215. As shown in Figures 23 and 24, the seedling planting device W is equipped with four transmission cases 222, a total of eight rotating cases 223 rotatably supported on the left and right rear sides of each transmission case 222, a pair of rotary planting arms 224 provided at both ends of each rotating case 223, multiple leveling floats 225 for leveling the field surface, a seedling tray 226 on which mat-shaped seedlings for planting are placed, a marker device 233 for forming an indicator line LN (see Figure 28) on the field surface, and the like. The seedling planting device W, configured in this way, rotates each rotating case 223 by power transmitted from the transmission case 222 while driving the seedling tray 226 to move back and forth horizontally. This allows the planting arms 224 to alternately remove seedlings from the bottom of the seedling tray 226 and plant them on the field surface. Therefore, the seedling planting device W is configured as an 8-row planting type, planting seedlings with planting arms 224 provided on the 8 rotating cases 223. The marker device 233, although not described in detail, is provided on the left and right sides of the seedling planting device W and is configured to be operable to an operating position in which it is in contact with the field surface and forms an indicator line LN on the field surface corresponding to the next work step as the vehicle body 300 moves, and a stored position that is raised above the field surface. The position switching of the marker device 233 is performed by an electric motor (not shown). As shown in Figures 23 to 25, the left and right sides of the bonnet 212 of the vehicle body 300 are provided with a plurality (for example, four) of normal spare seedling trays 228 on which spare seedlings for supplying the seedling planting device W can be placed, and one rail-type spare seedling tray 229 on which spare seedlings for supplying the seedling planting device W can be placed. The left and right sides of the bonnet 212 of the vehicle body 300 are provided with a pair of left and right spare seedling frames 230 that support each of the normal spare seedling trays 228 and the rail-type spare seedling tray 229, and the upper parts of the left and right spare seedling frames 230 are connected by a connecting frame 231. As shown in Figures 23 to 25, the central part of the vehicle body 300 is equipped with a driver's unit 240 where various driving operations are performed. The driver's unit 240 is equipped with a driver's seat 241 in which the driver can sit, a control tower 242, a steering handle 243 which is a manual steering device consisting of a steering wheel for manually steering the front wheels 210, a main gear lever 244 which can switch between forward and reverse and change the driving speed, and an operating lever 245. The driver's seat 241 is located in the central part of the vehicle body 300. The control tower 242 is equipped with the steering handle 243, main gear lever 244, operating lever 245, etc. which can be operated freely. A boarding step 246 is provided at the foot area of ​​the driver's unit 240. Auxiliary steps 247 are provided on the left and right outer positions of the boarding step 246. The boarding step 246 also extends to both the left and right sides of the bonnet 212. As shown in Figures 23 to 25, the operating lever 245 is located on the lower right side of the steering handle 243. Although not shown in detail, the operating lever 245 is configured to be freely movable in a cross shape from the central neutral position to the raised position, lowered position, right marker position, and left marker position, and is biased to the neutral position. When the operating lever 245 is moved to the raised position, the power transmission to the seedling planting device is interrupted, the seedling planting device W rises, and the left and right marker devices 233 (see Figure 23) are moved to the retracted position. When the operating lever 245 is moved to the lowered position, the seedling planting device W lowers and comes to rest on the field surface. When the operating lever 245 is moved to the right marker position in this lowered state, the right marker device 233 moves from the retracted position to the working position. When the operating lever 245 is moved to the left marker position, the left marker device 233 moves from the retracted position to the working position. When the operator starts the seedling planting operation, they operate the control lever 245 to lower the seedling planting device W, and the power transmission to the seedling planting device W is started, beginning the seedling planting operation. When stopping the seedling planting operation, they operate the control lever 245 to raise the seedling planting device W, and the power transmission to the seedling planting device W is cut off. The control tower 242 of the driver's unit 240 is equipped with a display device 248 capable of displaying various information using a liquid crystal display. In addition, a start point setting switch 249A, used for automatic steering control (described later), is located to the right of the display device 248, and an end point setting switch 249B is located to the left of the display device 248. The grip portion of the main gear shift lever 244 is equipped with a push-operated automatic steering switch 250. The automatic steering switch 250 is of the automatic return type and commands the switching of automatic steering control on and off each time it is pressed. The automatic steering switch 250 is positioned so that it can be pressed, for example, with the thumb while the grip portion of the main gear shift lever 244 is held in the hand. As shown in Figure 26, the vehicle body 300 is equipped with a steering unit U capable of steering the left and right front wheels 210. The steering unit U is equipped with a steering shaft 254 that is linked to a steering handle 243, a pitman arm 255 that swings in conjunction with the rotation of the steering shaft 254, left and right linking mechanisms 256 that are linked to the pitman arm 255, a steering motor 258, a gear mechanism 257 that links the steering motor 258 to the steering shaft 254, and the like. The steering shaft 254 is linked to the left and right front wheels 210 via the pitman arm 255 and the left and right connecting mechanisms 256, respectively. A steering angle sensor 260, consisting of a rotary encoder, is provided at the lower end of the steering shaft 254, and the amount of rotation of the steering shaft 254 is detected by the steering angle sensor 260. A torque sensor 261 is provided in the middle of the steering shaft 254 as a manual operation detection means for detecting the torque applied to the steering handle 243. For example, when the steering motor 258 is rotating in a predetermined direction, if the steering handle 243 is operated manually in the opposite direction to the direction of rotation, the torque sensor 261 can detect this. When the steering unit U performs automatic steering, the steering motor 258 is driven, and the driving force of the steering motor 258 rotates the steering shaft 254, thereby changing the steering angle of the front wheels 210. Therefore, the steering motor 258 corresponds to the steering operation means. When automatic steering is not performed, the steering unit U can be rotated by manually operating the steering handle 243. Next, we will describe the configuration for performing automatic steering control. A vehicle is equipped with a position detection means that uses GPS (Global Positioning System), a well-known technology, as an example of a Global Navigation Satellite System (GNSS) that detects the vehicle's position by receiving radio waves from satellites. Specifically, as a means of detecting position, a position measurement unit 264 (an example of a satellite positioning unit) is provided on the object to be positioned (vehicle body 300), which has a receiving device 263 with an antenna 262 that receives radio waves transmitted from multiple GPS satellites orbiting the Earth, and the position of the receiving device 263, i.e., the position measurement unit 264, can be measured based on the information of the received radio waves. As shown in Figures 23 to 25, the position measurement unit 264 is located at the front of the vehicle body 300 and is attached to the connecting frame 231 via a plate-shaped support plate 265. As shown in Figure 25, the connecting frame 231 can be changed between a usage state S1 in which the position measurement unit 264 is located above the upper end of the spare seedling frame 230, and a storage state S2 in which it is inverted vertically from the usage state S1 and the receiving device 263 is located below the upper end of the spare seedling frame 230. To elaborate, the connecting frame 231 is supported by the left and right spare seedling frames 230 via a connecting bracket 232 so as to be rotatable around the left and right axis X along the lateral direction of the machine, and so as to be able to fix its position in both the usage state S1 and the storage state S2. As shown in Figures 23 and 25, by setting the connecting frame 231 to the usage state S1, the receiving device 263 is supported at a higher position by the connecting frame 231 and the spare seedling frame 230. This reduces the risk of radio interference to the receiving device 263 and improves the radio wave reception sensitivity of the receiving device 263. In addition to the position measurement unit 264, the vehicle body 300 is equipped with an inertial measurement unit 266, which has a gyro sensor 266A or the like, as a direction detection means for detecting the direction of the vehicle body 300. Although not shown in the figures, the inertial measurement unit 266 is installed, for example, at a low position in the center of the vehicle body 300 in the lateral direction, located below and behind the driver's seat 241. The inertial measurement unit 266 can detect the angular velocity of the turning angle of the vehicle body 300, and the angle of change in the direction of the vehicle body can be determined by integrating the angular velocity. Therefore, the measurement information measured by the inertial measurement unit 266 includes the direction information of the vehicle body 300. Although not described in detail, the inertial measurement unit 266 can also measure the angular velocity of the left-right tilt angle and the front-rear tilt angle of the vehicle body 300, in addition to the angular velocity of the turning angle of the vehicle body 300. As shown in Figure 27, the vehicle body 300 is equipped with a control device 267 that controls the steering motor 258. The control device 267 includes a path setting unit 268 that sets a target travel path for the vehicle body 300 to travel, and a steering control unit 269 that controls the steering motor 258 so that the vehicle body 300 travels along the target travel path, based on the position information of the vehicle body 300 measured by the position measurement unit 264 and the orientation information of the vehicle body 300 measured by the inertial measurement unit 266. Specifically, the control device 267 is equipped with a microcomputer, and the path setting unit 268 and the steering control unit 269 are configured with a control program. As shown in Figure 27, a setting switch 249 is provided for setting the target movement path used for automatic steering control through a teaching process. The setting switch 249 has a start point setting switch 249A for setting the start point position and an end point setting switch 249B for setting the end point position. As described above, the start point setting switch 249A is located on the right side of the display device 248, and the end point setting switch 249B is located on the left side of the display device 248. As shown in Figure 27, the control device 267 receives information from the position measurement unit 264, the inertia measurement unit 266, the automatic steering switch 250, the start point setting switch 249A, the end point setting switch 249B, the steering angle sensor 260, the torque sensor 261, the vehicle speed sensor 270, and so on. The vehicle speed sensor 270, although not described in detail here, detects the vehicle speed by, for example, the rotational speed of the transmission shaft in the transmission mechanism relative to the rear wheels 211. The route setting unit 268 sets a teaching route corresponding to the target route to be automatically steered by a teaching process based on the operation of the start point setting switch 249A and the end point setting switch 249B. When the automatic mode is commanded at the start of the teaching route during actual operation, it is configured to set a target movement route LK parallel to the teaching route at that position. When the automatic mode is set, the steering control unit 269 performs automatic steering control by operating the steering motor 258 so that the detected position (self-position) NM of the traveling vehicle 300 detected by the position measurement unit 264 is on the target movement path LK, and the detected direction (self-direction) of the traveling vehicle 300 detected by the inertial measurement unit 266 is the target direction on the target movement path LK. That is, during the automatic steering control of the traveling vehicle 300, the lateral position deviation ΔP (see Figure 29; also referred to as "position deviation amount ΔP" in the following description) between the self-position NM of the traveling vehicle 300 and the target movement path LK, and the angular deviation between the self-direction NA of the traveling vehicle 300 and the target direction TD are determined, and the steering motor 258 is controlled so that these deviations become smaller. When the steering control unit is performing automatic steering control, if the current vehicle position NM is shifted laterally from the target movement path LK, and the current vehicle heading NA is the same as the target heading TD, it performs a position shift correction process to change the target heading, which is the control target, to an inclined target heading KA that is inclined toward the target movement path, and operates the steering motor 258. When performing positional deviation correction processing, if the vehicle's position NM is far from the point corresponding to the target movement path LK, the inclination of the inclined target bearing KA with respect to the target bearing TD is set to a large inclination. As the vehicle's position NM approaches the point corresponding to the target movement path LK, the inclination of the inclined target bearing KA with respect to the target bearing is reduced. Furthermore, the steering control unit 269 sets the inclination of the inclined target bearing KA with respect to the target bearing TD to a large inclination if the vehicle speed is low, and reduces the inclination of the inclined target bearing KA with respect to the target bearing TD as the vehicle speed is high. However, there is an upper limit to the inclination angle α of the inclined target direction KA relative to the target direction. Even if the vehicle speed is extremely low or the positional deviation ΔP is large, the inclination angle α is set to a value below the set upper limit. This is because if the inclination angle α is too large, the vehicle body 300 may make a sharp turn, potentially making the driving state unstable (in the following explanation, this inclination angle α will also be referred to as the "set inclination angle α"). Furthermore, when the steering control unit 269 performs positional deviation correction processing, the greater the vehicle speed, the smaller the change operation speed at which the steering motor 258 changes direction. Therefore, if the vehicle speed is low, the change operation speed is set to be larger, and as the vehicle speed increases, the change operation speed decreases. Next, we will explain the operation of the control device 267 when planting seedlings in a rectangular paddy field. As shown in Figure 28, the rice transplanter travels in a paddy field by alternately repeating straight-line travel, which involves planting seedlings while traveling along the target travel path LK, and turning travel, which involves turning at the end position of the target travel path LK toward the next target travel path LK, which is parallel to the target travel path LK. The steering control unit 269, in principle, performs automatic steering control during straight-line travel when planting seedlings, and does not perform automatic steering control during travel other than straight-line travel. First, the vehicle 300 is positioned at the starting point R1 at the edge of the field ridge, and the starting point setting switch 249A is operated. At this time, the control device 267 is set to automatic cut-off mode. Then, while the driver manually controls the vehicle, the vehicle 300 is driven in a straight line from the starting point R1 along the straight shape of the edge of the field ridge on the side in a non-working state, and is moved to the ending point R2 near the edge of the field ridge on the opposite side, and then the ending point setting switch 249B is operated. This executes the teaching process. In other words, a teaching path is set connecting the starting point R1 and the ending point R2 from the position information acquired by the receiving device 263 at the starting point R1 and the position information acquired by the receiving device 263 at the ending point R2. The direction along this teaching path is set as the reference target direction TD (hereinafter also referred to as the teaching direction TD). Next, the driver manually operates the steering wheel 243 to turn the vehicle body 300. At this time, the control device 267 can determine that the vehicle body 300 has turned by observing that the vehicle's heading NA is reversed. When the steering control unit 269 detects that a turn has occurred, it is set to a control restraint state in which it does not accept input from the automatic steering switch 250 until predetermined conditions are met after the turning of the vehicle body 300 is complete. The predetermined conditions are that a certain amount of time has elapsed since the turning of the vehicle body 300 was completed, and that the deviation angle between the vehicle's heading NA and the teaching heading TD is within a predetermined range. While the control restraint state is set, automatic steering control will not be started even if the automatic steering switch 250 is operated. At that time, the driver can manually operate the steering handle to align the vehicle body 300 so that the indicator line LN formed on the field surface aligns with the line of sight of the tip of the center mascot 214. When the control restraint state is released at the predetermined position R3 in Figure 27, an input to the automatic steering switch 250 is received. When the driver operates the automatic steering switch 250, it switches to automatic mode, and the steering control unit 269 starts automatic steering control from that point. At this time, the driver operates the operating lever 245 to lower the seedling planting device W and perform the seedling planting work. When automatic steering control is initiated, the position measurement unit 264 obtains information on the vehicle's position NM, and the inertial measurement unit 266 determines the vehicle's heading NA. At this time, as shown in Figure 29, the vehicle's position NM, which serves as the basis for data processing, is set to a position near the inertial measurement unit 266, not the actual installation position of the position measurement unit 264. Then, the steering motor 258 is operated to control the steering so that the current vehicle's position NM and heading NA match the target movement path LK and teaching heading TD. As a result, the vehicle body 300 travels accurately along the target movement path LK. The driver's hands are off the steering wheel 243. However, the vehicle speed is adjusted manually. When the steering control unit 269 is performing automatic steering control and the vehicle is moving in a straight line, as shown in Figure 29, if the detected vehicle position is laterally deviated from the target movement path and the detected direction is the same as the teaching direction TD, the steering control unit 269 performs a position deviation correction process to change the target direction from the teaching direction TD to an inclined target direction KA that is inclined by a set inclination angle α toward the target movement path, and operates the steering motor 258. In other words, as shown in Figure 30, in the position deviation correction process, the target direction when performing automatic steering control is changed from the teaching direction TD to an inclined target direction KA, which is inclined by a set inclination angle α from the teaching direction TD toward the target movement path, and automatic steering control is performed. Therefore, when this position deviation correction process is performed, the vehicle travels diagonally with a small azimuth deviation, so the position deviation ΔP can be reduced quickly. In this system, the further the player's position NM is from the point corresponding to the target movement path LK, the larger the set inclination angle α is set to be, and the closer the player's position NM is to the point corresponding to the target movement path LK, the smaller the set inclination angle α is set to be. Also, if the vehicle speed is low, the set inclination angle α is set to be high, and the faster the vehicle speed, the smaller the set inclination angle is set to be. However, an upper limit is set for the set inclination angle α, so no matter how low the vehicle speed is or how large the positional deviation is, the set inclination angle α will not exceed the set upper limit. Incidentally, the area corresponding to the target movement path LK mentioned above has a predetermined width of lateral region on both the left and right sides of the position corresponding to the target movement path LK. In other words, a control dead zone for position deviation is set, and when the position deviation is not zero and falls within the dead zone, the position deviation correction process ends. That is, the target direction is set not to the inclined target direction, but in the direction along the original teaching direction TD. Thus, the magnitude of the inclination of the inclined target direction KA relative to the target direction changes depending on the magnitude of the positional displacement ΔP of the vehicle body 300 and the vehicle speed. However, the correlation between the magnitude of the inclination, the positional displacement ΔP of the vehicle body 300, and the vehicle speed can be determined in advance through experiments and set as map data, or defined by calculation formulas. Furthermore, if the vehicle speed is constant, the smaller the positional displacement ΔP becomes, in other words, the closer the vehicle body 300's own position NM gets to the point corresponding to the target movement path LK, the smaller the set inclination angle α becomes. When the vehicle is traveling in a straight line while performing automatic steering control, as shown in Figure 31, if the vehicle body 300 is misaligned toward the already-worked area Z1, and a positional misalignment correction process is performed, the steering control unit 269 sets the set tilt angle α to be larger than when the vehicle body 300 is misaligned toward the unworked area Z2, as shown in Figure 32. In other words, if the vehicle body 300 is misaligned toward the already-worked area Z1, the set tilt angle α to tilt from the teaching direction TD is set to be larger and the positional misalignment correction process is performed. That is, since seedlings have already been planted in the already-worked area Z1, the vehicle body 300 is quickly corrected toward the target travel path LK so as not to trample these already planted seedlings. When the steering control unit 269 is performing automatic steering control, if it determines, based on the information detected by the torque sensor 261, that the driver has manually operated the steering handle 243 in opposition to the operation of the steering motor 258, in other words, if a command to change the steering handle 243 is issued, it reduces the operating force required to operate the steering motor 258 in automatic steering control to the extent that such manual operation is permitted. In this manner, when manual operation of the steering handle 243 is detected and the operating force of the steering motor 258 is reduced, the reduced operating force of the steering motor 258 is maintained even after manual operation ceases. This state is maintained after the automatic steering switch 250 is operated to switch to automatic off mode, and then again to automatic on mode. However, if a steering control command is issued continuously for a set period of time (for example, several tens of seconds) or longer, the automatic steering control will stop and the system will switch to automatic off mode. Prioritizing manual control in this way makes it possible to avoid collisions with obstacles or correct the course when the control is not performed properly. The system can be returned to automatic on mode by pressing the automatic steering switch. When the vehicle body 300 reaches the end position R4 of the straight-ahead travel path (see Figure 28), the driver operates the automatic steering switch 250 to switch the steering control unit 269 to automatic off mode. At this time, the driver operates the operating lever 245 to cut off the power transmission to the seedling planting device W and raise the seedling planting device W. After that, the driver manually operates the steering handle 243 to turn the vehicle body 300 toward the next straight-ahead travel path. Subsequently, as with the previous straight-ahead travel path, if the automatic steering switch 250 is operated after the determination condition is met after the turn, automatic steering control is started. The vehicle body 300 travels in a straight line while the automatic steering control is being executed. Then, the turning and straight-ahead travel described above are repeated. When the automatic steering mode is set, the steering control unit 269 performs assist control to operate the steering motor 258 so that the vehicle is in a driving state corresponding to the change command issued by the steering handle 243. In this assist control, based on the detection information from the torque sensor 261 and the steering angle sensor 260, the steering control unit 269 detects that the steering handle 243 has been operated and in the direction of that operation, and then operates the steering motor 258 in the same direction as that operation. When manual operation is stopped, the operation of the steering motor 258 also stops. [Another embodiment of the third embodiment] (1) In the above embodiment, when the steering control unit 269 performs position deviation correction processing, if the self-position NM is far from the location corresponding to the target movement path LK, the inclination of the inclined target direction KA with respect to the target direction TD is set to the large side, and as the self-position NM approaches the location corresponding to the target movement path LK, the inclination of the inclined target direction KA with respect to the target direction is made gentler. However, instead of this configuration, the following configuration may be used. In other words, when the steering control unit performs position deviation correction processing, it may maintain the inclined target direction until the vehicle's position (detected position) NM reaches a point corresponding to the target movement path LK. The point corresponding to the target movement path LK has a region (dead zone) of a predetermined width in the lateral direction on both the left and right sides of the position corresponding to the target movement path. That is, when the vehicle's position (detected position) NM reaches the end of the dead zone set relative to the position corresponding to the target movement path, the position deviation correction processing is terminated. This reduces control delay and allows the vehicle's direction to be corrected to align with the target movement path. (2) In the above embodiment, when the steering control unit 269 is performing automatic steering control and a change command is issued by the steering handle 243, the steering control unit 269 reduces the operating force required to operate the steering motor 258 in automatic steering control to the extent that manual operation is permitted. However, instead of this configuration, the following configuration may be used. In other words, when the steering control unit 269 is performing automatic steering control and a change command is issued by the steering handle 243, it may immediately stop the automatic steering control, and thereafter perform assist control to change the steering angle of the front wheels 210 by applying an auxiliary force from the steering motor 258 to the driver's operating force on the steering handle 243, in accordance with the operation of the steering handle 243, thereby rotating the steering shaft 254. (3) In the above embodiment, when the steering control unit performs a positional displacement correction process while the vehicle body is displaced toward the already-worked area Z1, it sets the set inclination angle α to a larger value than when the vehicle body is displaced toward the unworked area Z2. However, instead of this configuration, the following configuration may be used. In other words, when the steering control unit 269 performs a positional displacement correction process while the vehicle body 300 is displaced towards the unworked area Z2, it may set the set inclination angle α to a larger value compared to when the vehicle body 300 is displaced towards the already-worked area Z1. This configuration can be suitably used in work vehicles that perform tasks such as harvesting planted crops as they move, such as combine harvesters. (4) In the above embodiment, the criteria for allowing positional deviation correction processing after the vehicle body has performed a turning maneuver were that a certain amount of time has elapsed since the turning of the vehicle body 300 was completed, and that the deviation angle between the vehicle's heading NA and the teaching heading TD was within a predetermined range. However, instead of this configuration, the criteria for judgment may be as follows. Furthermore, the criteria are not limited to these, and in short, any criterion that can determine that the orientation of the vehicle body has stabilized is acceptable. (4-1) After the turn is complete, travel the set distance. (4-2) The set time has elapsed since the turn was completed. (4-3) The angle of deviation between the aircraft's heading NA and the teaching heading TD must be within a predetermined range. (4-4) Both (4-1) and (4-3) above must be satisfied. (4-5) All of the above conditions (4-1), (4-2), and (4-3) must be met. (5) In the above embodiment, a seedling planting device W is provided as an example of the work equipment, but the invention is not limited to this. For example, in addition to the seedling planting device W, a fertilizer application device, a pesticide spraying device, etc. may be provided as work equipment. (6) In the above embodiment, GPS was used as the satellite positioning unit for position detection, but other types of satellite positioning units such as Galileo may also be used. Alternatively, instead of a satellite positioning unit, other measurement systems may be used, such as an optical measurement device that projects laser light onto the ground to measure the position of the vehicle. (7) In addition to the above-mentioned ride-on rice transplanter equipped with a seedling planting device as a working device, the present invention can be used in various other work vehicles, such as a ride-on direct seeder which is a paddy field work vehicle equipped with a seeding device as a working device, a tractor equipped with a plow or the like as a working device, an agricultural work vehicle such as a combine harvester equipped with a harvesting unit or the like as a working device, or a construction work vehicle equipped with a bucket or the like as a working device. [Fourth Embodiment] Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. As shown in Figures 33 and 34, a ride-on rice transplanter (an example of an agricultural implement or farm vehicle), which is a planting and sowing type paddy field work vehicle among agricultural implements or farm vehicles, is equipped with a traveling body C having a traveling device A, and a working device for performing work on the field. The working device of the rice transplanter is a seedling planting device W capable of planting seedlings in the field. Note that in Figure 34, arrow Hf is the "front" of the traveling body C, arrow Hb is the "rear" of the traveling body C, arrow Hl is the "left" of the traveling body C, and arrow Hr is the "right" of the traveling body C. Furthermore, the rice transplanter is equipped with a positioning system consisting of GNSS (Global Navigation Satellite Systems) and IMU (Inertial Measurement Unit). As shown in Figure 38, the positioning system acquires and stores the positional information of the start and end points of a reference travel line KL set in the field, making it possible to set a set travel line SL parallel to the reference travel line KL. After the set travel line SL is set, the machine C is configured to automatically travel along the set travel line SL (equivalent to automatic travel with automatic steering). Furthermore, it is also possible to switch to manual driving (equivalent to manual driving with manual steering) in which the driver operates the steering wheel 343. As an example of how the mobile unit C operates, as shown in Figure 38, one method involves initially performing manual operation (teaching) to set the reference operating line KL. After completing the teaching, the unit is manually turned to the planting start position, and then switched to automatic operation to generate the set operating line SL and perform planting. At the end of the set operating line SL, planting is temporarily stopped, and the unit switches from automatic operation to manual steering to turn. This cycle is then repeated to generate the next set operating line SL and transition to automatic planting operation. Furthermore, as will be described later, the rice transplanter is also equipped with a function that, when automatically traveling along the set travel line SL, shifts the position of the set travel line SL itself in parallel, as shown in Figure 39. This function allows the operator to change the travel course G to match the boundary of the planting completion area E adjacent to the travel position, as shown in the figure, when the boundary shows a displaced shape, thereby preventing overlapping or discontinuity of the planting areas. As shown in Figures 33 and 34, the running gear A is equipped with a pair of left and right front wheels 310 and a pair of left and right rear wheels 311. The running body C is equipped with a steering unit U that can steer the left and right front wheels 310 of the running gear A. The front of the mobile unit C is equipped with an openable bonnet 312. Inside the bonnet 312 is an engine 313. A rod-shaped center mascot 314 is located at the tip of the bonnet 312. This center mascot 314 is used as a guide to check whether the position of the mobile unit C is aligned with the indicator line drawn on the field surface by a marker device 333, which will be described later. When the driver looks at the center mascot 314 from the driver's seat 341, if the indicator line is located on the extension of the driver's line of sight, it can be determined that the position of the mobile unit C is correct. The position check of the running machine C using the center mascot 314 can be performed not only during automatic operation but also during manual operation. It is particularly effective when switching to manual operation at the end point of the set running line SL, turning to change direction, and aligning with the starting point of the next set running line SL. The mobile body C is equipped with a frame-shaped body frame 315 that extends in the front-to-back direction. A support column frame 316 is erected at the front of the body frame 315. [Regarding seedling planting equipment] As shown in Figure 33, the seedling planting device W is connected to the rear end of the traveling machine C so as to be able to move up and down via a link mechanism 321 that moves up and down by the extension and retraction of a lifting cylinder 320 which is composed of a hydraulic cylinder. As shown in Figures 33 and 34, the seedling planting device W is equipped with four transmission cases 322, a rotating case 323 rotatably supported on the left and right rear sides of each transmission case 322, a pair of rotary planting arms 324 provided at both ends of each rotating case 323, a plurality of leveling floats 325 for leveling the field surface, a seedling tray 326 on which mat-shaped seedlings for planting are placed, and the like. In this embodiment, the seedling planting device W is configured as an 8-row planting type, but it may also be configured as a multi-row planting type other than 8 rows. The seedling planting device W, configured in this way, drives the seedling tray 326 to move back and forth horizontally, while the power transmitted from the transmission case 322 rotates each rotating case 323, so that seedlings are alternately picked up from the bottom of the seedling tray 326 by each planting arm 324 and planted on the surface of the field. [Regarding spare seedling trays] As shown in Figures 33 and 34, the left and right sides of the bonnet 312 of the traveling machine C are provided with a plurality of spare seedling trays 328 on which spare seedlings for supplying the seedling planting device W can be placed. The left and right sides of the bonnet 312 of the traveling machine C are also provided with a pair of spare seedling frames 330 on the left and right sides that support each spare seedling tray 328, and a connecting frame 331 that connects the upper parts of the left and right spare seedling frames 330. The connecting frame 331 has a U-shape when viewed from the front. The left and right ends of the connecting frame 331 are connected to the upper parts of the left and right spare seedling frames 330 via connecting brackets 332. [About the marker device] As shown in Figure 33, the seedling planting device W is equipped with marker devices 333 on both the left and right sides for forming indicator lines on the field surface. Each of the left and right marker devices 333 is equipped with a marker arm 334 supported by the seedling planting device W so as to be able to swing up and down, and a rotating body 335 having a plurality of circumferentially protruding parts, which is supported at the tip of the marker arm 334 so as to be able to rotate freely. In addition, an electric motor for the markers (not shown) is provided to operate the left and right marker devices 333 to the working position and the retracted position. By operating the marker device 333 to the working position, the rotating body 335 can come into contact with the field surface and leave a trajectory, which serves as an indicator line. [Regarding the driver's unit] As shown in Figures 33 and 34, the central part of the mobile body C is equipped with a control unit 340 where various driving operations are performed. The control unit 340 is equipped with a driver's seat 341 in which the driver can sit, a control tower 342, a steering handle 343 consisting of a steering wheel for manually steering the front wheels 310, a main gear lever 344 (equivalent to a gear shifting device) that can switch between forward and reverse and change the driving speed, and an operating lever 345 for operating the seedling planting device W. A boarding step 346 is provided at the foot area of ​​the driver's compartment 340. Auxiliary steps 347 are provided on the left and right outer sides of the boarding step 346. Boarding and alighting steps 348 are provided on both the left and right sides of the bonnet 312, serving as boarding and alighting passages that connect seamlessly to the boarding step 346. Left and right spare seedling frames 330 are positioned to the left and right of the boarding and alighting steps 348. The control tower 342 is also equipped with a steering wheel 343, a main gear lever 344, an operation lever 345, an instrument panel 349, and the like. [Regarding the main gear shift lever] The main gear shift lever 344, shown in Figures 33, 34, and 37, is located to the left of the steering handle 343. It is configured to swing freely in the forward and backward directions. By swinging it forward from the neutral position, forward gear changes can be performed, and by swinging it backward from the neutral position, reverse gear changes can be performed. Furthermore, the grip portion 344A at the upper end of the main gear shift lever 344 is equipped with a push-button type automatic steering switch 350 (an example of a changeover switch) (see Figure 37) for switching the automatic steering of the steering unit U on and off. The automatic steering switch 350 is positioned so that it can be pressed, for example, with the left thumb while the grip portion 344A is held in the left hand, and is configured to switch between manual steering and automatic steering alternately each time it is pressed. In other words, the operating direction of the automatic steering switch 350 is set to align with the left-right direction of the vehicle body C, and is different from the operating direction (forward-backward direction) of the main gear shift lever 344, thereby preventing erroneous operation. Furthermore, since the automatic steering switch 350 can be operated while holding the grip portion 344A, there is no need to change hands, and the efficiency of steering switching operations can be improved. [Regarding instrument panels] As shown in Figures 34 and 37, a meter panel 349 is positioned at the rear end of the bonnet 312, in front of the steering wheel 343. This meter panel 349 has a liquid crystal display unit 349A with a backlight in the left and right center. In addition, a pair of indicator buttons 352 (corresponding to indicator switches) are provided on both the left and right sides of the liquid crystal display unit 349A to set the start and end points of the reference driving line KL. Furthermore, multiple indicator lamps are provided around the liquid crystal display unit 349A, and are configured to display work information. The LCD display unit 349A displays information such as the hour meter, the status of the automatic planting clutch, the remaining fuel level, and the coolant temperature, as well as notifications such as "sensor warming up," "whether the IMU needs to be reset," "GPS signal reception status," "manual steering during automatic driving," "detection status of the end point of the ridge," and "ground contact status of the seedling planting device," along with "how to respond" to these notifications. In addition, it is equipped with multiple indicator lights, including an oil low lamp, a charge lamp, a seedling low lamp, a planting indicator lamp, a ridge clutch lamp, and a marker lamp. The instruction button 352 can be pressed during manual driving for teaching purposes (when the vehicle is driven after switching to manual steering using the automatic steering switch 350) to set the start and end points of the reference driving line KL based on the position information of the vehicle C at that time. In this embodiment, of the pair of indicator buttons 352, the right indicator button 352A is configured to indicate the starting point of the reference travel line KL, and the left indicator button 352B is configured to indicate the ending point of the reference travel line KL. Furthermore, as described above, the instruction button 352 is used as a means for setting the reference travel line KL, and during automatic travel, it is also used as a displacement switch 359 for displacing the set travel line SL parallel to the ground. Therefore, when the instruction button 352 functions as a displacement switch 359 (during automatic driving), the right instruction button 352A functions as a right displacement switch 359A that displaces the set driving line SL to the right with respect to the forward direction, and the left instruction button 352B functions as a left displacement switch 359B that displaces the set driving line SL to the left with respect to the forward direction. The parallel displacement of the set travel line SL is controlled by the line displacement unit 382, ​​which will be described later. The traveling machine C automatically changes its travel path to the new set travel line SL that has been displaced by the line displacement unit 382 and travels accordingly (see Figure 39). The parallel displacement control of this set running line SL is carried out as shown in the flowchart in Figure 40. In other words, when the automatic steering switch 350 is turned ON and the mobile unit C is automatically traveling along the set travel line SL (#01), when the displacement switch 359 is pressed (#02), the set travel line SL is displaced parallel by a predetermined amount b (see Figure 39) (#03). Furthermore, this parallel displacement control continues until the automatic steering switch 350 is turned off (#04). [About the steering unit] As shown in Figure 35, the steering unit U is equipped with the steering handle 343, a steering shaft 354 linked to the steering handle 343, a pitman arm 355 that swings in conjunction with the rotation of the steering shaft 354, left and right connecting mechanisms 356 linked to the pitman arm 355, a steering motor 358, a gear mechanism 357 that links the steering motor 358 to the steering shaft 354, and the like. The steering shaft 354 is linked to the left and right front wheels 310 via the pitman arm 355 and the left and right connecting mechanisms 356. The amount of rotation of the steering shaft 354 is detected by a steering angle sensor 360 (see Figure 36), which consists of a rotary encoder provided at the lower end of the steering shaft 354. When the steering unit U is manually steered, the steering motor 358 provides an auxiliary force corresponding to the driver's operation of the steering handle 343 to rotate the steering shaft 354, thereby changing the steering angle of the front wheels 310. On the other hand, when the steering unit U is automatically steered, the steering motor 358 is driven, and the driving force of the steering motor 358 rotates the steering shaft 354, thereby changing the steering angle of the front wheels 310. [Regarding the measurement unit with a receiving device and the inertial measurement device] As shown in Figures 33, 34, and 36, the mobile vehicle C is equipped with a measurement unit 361 having a receiving device 363 that acquires position information by a satellite positioning system and a secondary inertial measuring device 364 that can detect the tilt (pitch angle, roll angle) of the mobile vehicle C, and a main inertial measuring device 362 (corresponding to the "inertial measuring device") that measures inertial information. The main inertial measuring device 362 and the sub-inertial measuring device 364 are each composed of an IMU (Inertial Measurement Unit). The measurement unit 361 and the main inertia measurement device 362 are positioned at different locations on the mobile body C and on the left-right centerline CL of the mobile body C. The Global Navigation Satellite System (GNSS) mentioned above is best known as the Global Positioning System (GPS). GPS uses multiple GPS satellites orbiting the Earth, control stations that track and control the GPS satellites, and a receiving device 363 installed on the object being positioned (mobile vehicle C) to measure the position of the receiving device 363. The receiving device 363 is used to acquire position information of the mobile vehicle C via the satellite positioning system. As shown in Figures 33 and 34, the measurement unit 361 is attached to the connecting frame 331 via a plate-shaped support plate 365. The main inertial measurement device 362 is positioned near the center in the longitudinal direction of the entire length of the traveling machine C and the seedling planting device W in the longitudinal direction. [Regarding the control configuration] As shown in Figure 37, the mobile vehicle C is equipped with a control device 375 that controls the automatic steering of the steering unit U. The control device 375 includes an information storage unit 376 (corresponding to a recording unit), a teaching storage unit 377, a turning detection unit 78, a start determination unit 79, an information correction unit 380, a starting point setting unit 381 that generates a set travel line SL for the mobile vehicle C to travel on, a line displacement unit 382 that sets the set travel line SL to be parallel, a state detection unit 383, and a control unit 384 that controls the steering unit U so that the mobile vehicle C travels along the set travel line SL based on position information and inertia information. The control device 375 receives information from the receiving device 363, the sub-inertia measuring device 364, and the gyro sensor 370, acceleration sensor 371, steering angle sensor 360, automatic steering switch 350, instruction button 352, displacement switch 359, etc., which are located in the main inertia measuring device 362. The information storage unit 376 is configured to store location information acquired from the receiving device 363 on a time-based basis. The teaching memory unit 377 is configured to calculate the reference driving line KL based on the operation of the instruction button 352, using the position information of the starting point K1 and the ending point K2 from the position information stored in the information memory unit 376. The turning detection unit 378 is configured to detect the start of turning of the mobile vehicle C and the end of turning of the mobile vehicle C based on the steering angle information of the steering operation shaft 354 of the steering unit U, which is input from the steering angle sensor 360. The start determination unit 379 is configured to determine whether or not to start automatic steering control of the mobile unit C. The information correction unit 380 is configured to perform a correction process each time automatic steering control of the mobile vehicle C is started, based on the position information acquired by the receiving device 363 and the information measured by the sub-inertial measuring device 364, using the accumulated error of the inertial information detected by the gyro sensor 370 from the inertial information measured by the main inertial measuring device 362. The starting point setting unit 381 is configured to generate a set driving line SL based on the reference driving line KL, the position of the vehicle C at the start of automatic steering control, and the direction of the vehicle. The line displacement unit 382 is configured to set the set running line SL to be displaced by a predetermined amount b parallel to the right (or left) by operating the right displacement switch 359A (or left displacement switch 359B). The state detection unit 383 is configured to detect the distance deviation (deviation distance) between the self-position of the mobile body C and the set travel line SL, and the angle deviation (deviation angle) between the self-direction of the mobile body C and the set travel line SL, during automatic steering control of the mobile body C. The control unit 384 is configured to control the drive of the steering motor 358 of the steering unit U based on information input from the state detection unit 383. A specific example of the operation of the rice transplanter according to this embodiment will be described. [1] As shown in Figure 38, start manual driving for teaching purposes. This manual operation can be started by swinging the main gear lever 344 forward from the neutral position, and the vehicle travels along a straight course following the ridges, starting from the outer edge of the field near the ridges. During travel, pressing the right indicator button 352A allows the position information of the vehicle C at that time to be acquired by the positioning system and recorded in the information storage unit 376 as the position information of the starting point K1 of the reference travel line KL. Furthermore, after continuing manual operation, pressing the left indicator button 352B allows the position information of the mobile unit C at that time to be acquired by the positioning system and recorded in the information storage unit 376 as the position information of the endpoint K2 of the reference driving line KL. As a result, the teaching memory unit 377 sets the reference running line KL as a straight line connecting the starting point K1 and the ending point K2. [2] After traveling in a straight line on the standard travel line KL, the steering handle 343 is turned to change the direction of the travel vehicle C, and manual travel is performed to the starting position of the adjacent set travel line SL. In this case, the position of the traveling machine C to a predetermined location can be adjusted using the indicator line drawn on the field surface by the marker device 333 while the machine is traveling along the reference travel line KL, and the aforementioned center mascot 314. [3] Planting is performed while the mobile unit C is driven automatically. Automatic driving is initiated by swinging the main gear lever 344 forward and pressing the automatic steering switch 350. When the automatic steering switch 350 is pressed, the starting point setting unit 381 acquires the position information of the vehicle C at that time using the positioning system, and records it in the information storage unit 376 as the position information of the starting point S0 of the set driving line SL. Furthermore, a set driving line SL is generated that passes through the starting point S0 and is parallel to the reference driving line KL. When the set travel line SL is generated, the control device 375 controls the steering unit U in the direction of deviation correction based on the deviation information of the traveling machine C input from the state detection unit 383, thereby controlling the traveling machine C to travel along the set travel line SL. [4] Disable automatic operation on the designated running line SL. When the vehicle reaches the end of the set travel line SL, the automatic steering switch 350 is pressed to deactivate automatic travel. In this state, the steering handle 343 is rotated to change the direction of the vehicle C, and manual steering is performed to the starting position of the next adjacent set travel line SL. From this point onward, the process alternates between automatically steering the steam locomotive along the set driving line and manually changing direction. Furthermore, if you want to displace the set running line SL itself in parallel while it is running, you can press the displacement switch 359 on the side you want to displace, and it will be displaced in parallel by a predetermined amount b. According to the rice transplanter of this embodiment, by simply switching from manual to automatic driving using the automatic steering switch (an example of a changeover switch) 50, that point can be set as the starting point S0 of the set driving line SL. Therefore, the operator can freely set the set driving line SL to a desirable position while observing the field conditions. As a result, various operations on the machine body C can be performed efficiently, and the burden on the operator can be reduced. Furthermore, while the machine is automatically traveling along the pre-set travel line SL, the pre-set travel line SL can be easily displaced parallel to the ground simply by operating the displacement switch 359, allowing for agricultural work to be performed in a way that better matches the field conditions. Furthermore, since the displacement switch 359 has its switch placement aligned with the direction of displacement operation, erroneous operation can be prevented, resulting in good operability. [Another embodiment of the fourth embodiment] (1) The term "agricultural implement" is not limited to the type of rice transplanter described in the previous embodiment, but may also include other types of rice transplanters or agricultural implements other than rice transplanters, and these are collectively referred to as agricultural implements. (2) The changeover switch (automatic steering switch 350) is not limited to the automatic steering switch with the structure described in the previous embodiment, and may, for example, have a swing-operated or rotary-operated structure instead of a push-operated type. Therefore, the operating direction of the changeover switch (automatic steering switch 350) is not limited to the left-right direction of the traveling machine C. Furthermore, the location of the changeover switch may be other than the gear shifting mechanism, or it may even be combined with other function switches. These are collectively referred to as "changeover switches." <3> The indicator switch is not limited to the indicator button 352 described in the previous embodiment. For example, the switch structure may be a swing-operated or rotary-operated structure instead of a press-operated type. Furthermore, the right instruction button 352A and the left instruction button 352B are not limited to being positioned in correspondence with the left-right direction of the mobile unit C; for example, they may be positioned side by side in the front-to-back direction, or in completely different positions. Furthermore, the system is not limited to providing two switches as indicator switches; for example, it may be configured so that a single switch can indicate the starting point K1 and ending point K2 of the reference travel line KL. Furthermore, the indicator switch may be shared with another switch, separate from the displacement switch 359, or it may be configured as a standalone switch. These are collectively referred to as "instruction switches." <4> The displacement switch 359 is not limited to the displacement switch described in the previous embodiment. For example, the switch structure may be a swing-operated or rotation-operated structure instead of a press-operated type. Furthermore, the displacement switch 359 may be combined with another switch, or it may be configured as a standalone switch. Furthermore, the displacement switch 359 is not limited to two switches; for example, it may be configured so that one switch can indicate the displacement direction of the set running line SL. These are collectively referred to as displacement switches 359. <5> With regard to steering control associated with the operation of the displacement switch 359, for example, in order to prevent excessive parallel displacement from being performed by repeatedly pressing the switch, the control device 375 may be provided with an operation cancellation unit 385 that prevents the operation of the displacement switch 359 from being reflected in the displacement control when certain conditions are met, as shown in Figure 41. The following are examples of how the operation of the displacement switch 359 is canceled by the operation cancellation unit 385. For example, the initial predetermined number of operations on the displacement switch 359 are not reflected in the displacement control of the set travel line SL. In this embodiment, once the first operation of the displacement switch 359 displaces the set travel line SL by a predetermined amount b, the displacement control is not reflected for a predetermined number of operations (for example, 4 times) from the second operation onward. As a result, even if the operation is pressed five times in quick succession, the displacement of the set travel line SL will be limited to the predetermined amount b for one operation, thus preventing excessive parallel displacement. In another embodiment, when the displacement switch 359 is operated, the operation of the displacement switch 359 is not reflected in the displacement control of the set running line SL until a set time has elapsed since the operation of the displacement switch 359. In this embodiment, for example, if the setting time is set to 5 seconds, then for 5 seconds from the first operation of the displacement switch 359, no matter how many times it is pressed repeatedly, the displacement of the set running line SL will be a predetermined amount b for one operation, thereby preventing excessive parallel displacement. In another embodiment, as shown in Figure 42, when the displacement switch 359 is operated, the operation of the displacement switch 359 is not reflected in the displacement control of the set travel line SL until the traveling machine C reaches an error region of a predetermined width SB set around the set travel line SL after displacement. In this embodiment, for example, if the predetermined amount b is set to 10 cm and the predetermined width SB is set to 6 cm (3 cm on each side), as the machine C changes its course G due to the first operation of the displacement switch 359, while it is passing through a region of (b - SB / 2) = 10 - 3 = 7 cm in the direction of parallel displacement, the displacement of the set running line SL is canceled no matter how many times the switch is pressed, thereby preventing excessive parallel displacement. <6> The position information of the mobile vehicle C acquired by the positioning system is the planar position information of the measurement unit 361. However, the starting point K1 and ending point K2 of the reference driving line KL, which are set based on the area above it, and the starting point S0 of the set driving line SL, are not necessarily limited to being set as the planar position of the measurement unit 361 on the mobile vehicle C. For example, they may be set as the front end position (or rear end position) on the left-right center line CL of the mobile vehicle C, or a position located a predetermined distance forward (or backward) from the center of gravity of the mobile vehicle C (for example, the position in front where the driver's line of sight passing through the center mascot 314 intersects with the field surface). (7) In addition to the above-mentioned riding-type rice transplanter equipped with a seedling planting device as a working device, the present invention can also be used in agricultural machinery such as a riding-type direct seeder which is a planting and seeding type paddy field work vehicle equipped with a seeding device as a working device, a tractor equipped with a plow or the like as a working device, or a combine harvester equipped with a harvesting unit or the like as a working device. [Fifth Embodiment] Before describing a specific embodiment of the field work vehicle according to the present invention, the basic principle of vehicle control employed in the field work vehicle will be explained using Figure 43. In Figure 43, field work vehicles are assumed to include a rice transplanter, a seeder, a tractor, and a combine harvester. As field work equipment, the rice transplanter is equipped with a planting device, the seeder with a seeding device, the tractor with a tilling device, and the combine harvester with a harvesting device. These field work devices are connected to the respective vehicle bodies so that they can be raised and lowered between working and non-working positions. This field work vehicle (hereinafter simply referred to as "vehicle") travels through a field bounded by parallel upper and lower ridges as shown in Figure 43, repeatedly making 180-degree turns (U-turns) in between, in a back-and-forth linear motion. An upper ridge border area is defined near the upper ridge, and a lower ridge border area is defined near the lower ridge. The vehicle makes turns in the ridge border areas and performs linear work in the rest of the field. The vehicle is equipped with a positioning unit that outputs positioning data indicating its own position. Furthermore, it is equipped not only with a manual steering unit that steers the vehicle based on human operation, but also with an automatic steering unit that steers the vehicle automatically. The positioning data output from the positioning unit is based on the position of the antenna, but in this case, the vehicle's position is corrected so that it is not based on the antenna position, but on an appropriate position of the vehicle, such as the point of application of the field work equipment to the ground. An example of field driving in this field is shown below. First, after crossing the lower ridge and entering the field, the vehicle lowers the field work device to the working position at point A1 through the driver's operation and begins a straight-line work journey (outbound). This lowering of the field work device is recorded as a vehicle behavior indicating the start of work, along with positioning data indicating the location of point A1. After the straight-line work journey, when the vehicle reaches the turning area at point B1, the driver raises the field work device to the non-working position through the driver's operation and transitions to a 180-degree turning journey. This raising of the field work device is recorded as a vehicle behavior indicating the end of work, along with positioning data indicating the location of point B1. Once the vehicle has completed its turn-around maneuver along the edge of the field, it lowers the field work device back to its working position at point A2 and begins its return journey in a straight line. This lowering of the field work device is also recorded as vehicle behavior indicating the start of work, along with positioning data indicating the location of point A2. The location of point A2 can be estimated from the location of point B1, taking into account the round-trip work interval corresponding to the work width (planting width or tilling width). Therefore, if the vehicle approaches the estimated point A2 during the turn-around maneuver along the edge of the field, the driver can be notified and prompted to lower the field work device back to its working position. It is also possible to automatically lower the field work device back to its working position when the vehicle reaches the estimated point A2. The position where the vehicle resumes its return journey in a straight line is set as the final point A2. The endpoint of this linear work run (return trip), point B2, where the vehicle reaches the ridge area again, can also be estimated from the position of point A1. Therefore, as the vehicle approaches point B2, the driver can be notified to raise the field work equipment to a non-working position and prepare for turning around before reaching the ridge area. It is also possible to automatically raise the field work equipment to a non-working position when the vehicle reaches the estimated point B2. Once the vehicle reaches the ridge area, it will automatically or manually transition to turning around within the ridge area. After the turning around is completed, the linear work run (return trip) will start again from point A3. In this way, the vehicle repeatedly performs work runs and direction-changing runs, passing through points B3, A4, B4, A5, and so on. If point A1 is set, points B2, A3, and so on can be estimated from point A1, taking into account the round-trip work run interval. However, when estimating point A3, it is possible to estimate it from point A1, but since point B2, which is the position where the vehicle actually transitioned from work run to direction-changing run, has been detected, it is also possible to estimate point A3 from point B2. In particular, if the actual ridgeline area does not extend in a straight line but rather diagonally or in stages, the boundary points of such ridgeline areas can be correctly detected by estimating from newly set points along the way. For example, as shown in Figure 44, if the edge of the field has a step, it is necessary to extend the linear work run beyond the estimated point B4. If the linear work run is performed by automatic steering, the automatic steering is deactivated, and the linear work run is continued by manual steering to a position suitable for turning around (the newly set point B4). Once point B4 is newly set, the next point A5 is estimated from point B4. Points A1, A2, ..., which are the starting points for work runs, can be automatically set based on specific vehicle behaviors. Suitable specific vehicle behaviors include, for example, a command to start work for the field work equipment, detection of a change in the position of the field work equipment to the working position, and detection of the engagement of the power transmission clutch for the field work equipment. Furthermore, the state of the control tools operated by the driver may also be used as specific vehicle behaviors. Similarly, points B1, B2, ..., which are the ending points of work runs (starting points for direction changes), can also be automatically set based on specific vehicle behaviors. Suitable specific vehicle behaviors include, for example, a command to stop work for the field work equipment, detection of the field work equipment moving to a non-working position, and detection of the disengagement of the power transmission clutch for the field work equipment. Furthermore, the state of the control tools operated by the driver may also be used as specific vehicle behaviors. If the initial work route defined by points A1 and B1 is designated as the reference work route, the target work route for subsequent automatic steering can be calculated based on this reference work route. Since work runs are generally in a straight line, the steering is simpler than for turning runs, so it is advantageous from a control perspective to perform work runs with automatic steering and turning runs with manual steering. If the field shape is a simple rectangle, by setting points A1 and B1, the transition timing between subsequent work runs and turning runs, that is, the timing of reaching the edge of the field and the timing of leaving the edge of the field, can be estimated from points A1 and B1. If a vehicle enters the ridge-edge area from a straight-line work run (return trip) but fails to change direction for any reason, it may end up on the ridge. To avoid this problem, it is important to estimate and record points B2, B3, B4, etc., which are the endpoints of the straight-line work run (return trip). Since the vehicle's position can be calculated by the positioning unit, this vehicle position can be constantly compared with the position of the endpoint of the work run (return trip) (the point of entry into the ridge-edge area). This allows for vehicle deceleration, warning signals, and vehicle stopping before and after the vehicle enters the ridge-edge area. In the example described above, points A1 and B1 were set during the initial work run, and points A2, A3, B2, B3, etc., between subsequent work runs and direction changes (points where the vehicle reaches and leaves the edge of the field), were estimated from points A1 and B1. If the vehicle is equipped with a field map storage unit that stores field map data, the vehicle's position and the map data can be used for map matching to detect when the vehicle reaches or leaves the edge of the field. In this case, setting points A1 and B1 and estimating other points from points A1 and B1 becomes unnecessary. Next, one specific embodiment of the field work vehicle according to the present invention will be described using the drawings. Figure 45 is a side view of a ride-on type rice transplanter, which is an example of a field work vehicle, and Figure 46 is a top view. This rice transplanter comprises a traveling body C and a field work device that performs work on the field. The field work device here is a seedling planting device W capable of planting seedlings in the field. Note that in Figure 46, arrow F is the "front" of the traveling body C, arrow B is the "rear" of the traveling body C, arrow L is the "left" of the traveling body C, and arrow R is the "right" of the traveling body C. As shown in Figure 45, the running gear is equipped with a pair of left and right front wheels 410 and a pair of left and right rear wheels 411. The running machine C is equipped with a steering unit U1 that can steer the left and right front wheels 410 of the running gear. As shown in Figures 45 and 46, the front of the mobile body C is equipped with an openable bonnet 412. An engine 413 is housed inside the bonnet 412. The mobile body C is equipped with a frame-shaped body frame 415 that extends in the front-rear direction. A support column frame 416 is erected at the front of the body frame 415. As shown in Figure 45, the seedling planting device W is connected to the rear end of the traveling machine C so as to be able to move up and down via a link mechanism 421 that moves up and down by the extension and retraction of a lifting cylinder 420 composed of a hydraulic cylinder. The seedling planting device W is equipped with four transmission cases 422, a rotating case 423 that is rotatably supported on the left and right rear sides of each transmission case 422, a pair of rotary planting arms 424 provided at both ends of each rotating case 423, a plurality of floats 425 for leveling the surface of the field, a seedling tray 426 on which mat-shaped seedlings for planting are placed, and the like. In other words, the seedling planting device W is configured as an 8-row planting type. On the left and right sides of the bonnet 412 of the mobile unit C, there are multiple (for example, four) conventional spare seedling trays 428 on which spare seedlings for supplying the seedling planting device W can be placed, and one rail-type spare seedling tray 429 on which spare seedlings for supplying the seedling planting device W can be placed. Also on the left and right sides of the bonnet 412 of the mobile unit C, there is a pair of spare seedling frames 430 on the left and right sides that support each of the conventional spare seedling trays 428 and the rail-type spare seedling tray 429, and a connecting frame 431 that connects across the tops of the left and right spare seedling frames 430. The connecting frame 431 has a U-shape when viewed from the front. The left and right ends of the connecting frame 431 are connected to the tops of the left and right spare seedling frames 430 via connecting brackets 432. The central part of the vehicle body C is equipped with a control unit 440 where various driving operations are performed. The control unit 440 is equipped with a driver's seat 441 in which the driver can sit, a control tower 442, a steering handle 443 consisting of a steering wheel for manual steering of the front wheels 410, a main gear lever 444 for switching between forward and reverse and changing the driving speed, and other control levers 445. The driver's seat 441 is located in the central part of the vehicle body C. The control tower 442 is equipped with the steering handle 443 and the main gear lever 444 for easy operation. A boarding step 446 is provided at the foot of the control unit 440. An operating lever 445 is provided on the lower right side of the steering handle 443. When the operating lever 445 is operated to the raised position, a planting clutch (not shown), which is a type of work clutch, is operated to the disengaged state, and the seedling planting device W rises. When the operating lever 445 is operated to the lowered position, the planting clutch (not shown) is operated to the disengaged state, and the seedling planting device W descends. When the central float 425 touches the surface of the field, the seedling planting device W comes to a stop with its surface touching the field. As shown in Figure 47, the steering unit U1 is equipped with the steering handle 443, a steering shaft 454 linked to the steering handle 443, a pitman arm 455 that swings in conjunction with the rotation of the steering shaft 454, left and right linking mechanisms 456 linked to the pitman arm 455, a steering motor 458, a gear mechanism 457 that links the steering motor 458 to the steering shaft 454, and the like. The steering unit U1 can operate in automatic steering mode and manual steering mode. In manual steering mode, the steering motor 458 provides an auxiliary force to the driver's operating force on the steering handle 443, corresponding to the operation of the steering handle 443, thereby rotating the steering shaft 454 and changing the steering angle of the front wheels 410. On the other hand, in automatic steering mode, the steering motor 458 is automatically controlled, and the driving force of the steering motor 458 rotates the steering shaft 454, changing the steering angle of the front wheels 410. In this embodiment, the steering handle 443 and the steering motor 458 function as components of the manual steering unit that manually steers the vehicle C. Furthermore, the control function for automatic steering that automatically steers the vehicle C is built into the control device 408 (see Figure 48), which will be described later, and the steering motor 458 is driven based on control commands from the control device 408. Furthermore, if the operating displacement of the steering wheel 443 is not directly transmitted to the steering shaft 454, but rather the operating displacement of the steering wheel 443 is detected by a sensor and the steering motor 458 is driven based on that detected value, in the case of a so-called drive-by-wire system, the control function for manual steering is also built into the control device 408. The mobile vehicle C is equipped with a positioning unit 461, and the position of the mobile vehicle C is determined from positioning data from the positioning unit 461. The positioning unit 461 includes a satellite navigation module configured as a GNSS module and an inertial navigation module configured as a module incorporating a gyro acceleration sensor and a magnetic direction sensor. A satellite antenna for receiving GPS signals and GNSS signals is connected to the satellite navigation module. At least this satellite antenna is attached to a location where radio wave reception sensitivity is good, in this embodiment to a connecting frame 431. The satellite navigation module and the inertial navigation module may be installed in different locations. Figure 48 shows the control device 408 equipped on this rice transplanter. Figure 48 primarily shows the steering-related functions within the control device 408. This control device 408 employs the basic principles of automatic and manual steering described using Figures 43 and 44. The control device 408 is connected to the positioning unit 461, the vehicle state detection sensor group 409, the contact detector 490, the driving mode switching device 465, and the steering mode switching device 466 via the input signal processing unit 408a. Furthermore, the control device 408 is connected to the notification device 407, the vehicle driving equipment group 471, and the work equipment group 472 via the output signal processing unit 408b. The driving mode switching device 465 and the steering mode switching device 466 are composed of switches and buttons. The vehicle state detection sensor group 409 consists of various sensors and switches provided to detect the operation and attitude of the traveling machine C, and the operation and attitude of the seedling planting device W as a field work device. The contact detector 490 is well known in itself and is therefore not shown in Figures 45 and 46, but it has a structure that detects contact between the rice transplanter and an obstacle. When the contact detector 490 detects contact between the rice transplanter and an obstacle, the rice transplanter makes an emergency stop. The steering mode switching device 466 is a switch that selects between an automatic steering mode, in which the vehicle is driven with automatic steering, and a manual steering mode, in which the vehicle is driven with manual steering. For example, by operating the steering mode switching device 466 while driving with automatic steering, the vehicle can be switched to manual steering, and by operating the steering mode switching device 466 while driving with manual steering, the vehicle can be switched back to automatic steering. The driving mode switching device 465 is a teaching switch for informing the control device 408 of the boundary between the ridge-edge area and the non-ridge-edge area. In this embodiment, the driving mode switching device 465 has an A button and a B button. The driver presses the A button when the vehicle transitions from turning-around driving to work driving, and the B button is pressed when the vehicle transitions from work driving to turning-around driving. The notification device 407 includes lamps and buzzers, and outputs various information that the driver wants to be notified of, such as approaching the edge of a field or deviating from the target driving path during automatic steering, visually or audibly based on commands from the control device 408. Furthermore, if the notification device 407 includes a flat panel display or the like, it can also provide text information. The vehicle running equipment group 471 includes various operating and control equipment mounted on the running machine C for driving, such as operating equipment such as the steering motor 458 that constitutes the steering unit U1, control equipment that adjusts the engine speed, operating equipment for the transmission such as clutches and shifters, and brake operating equipment. In this embodiment, the work running equipment group includes operating equipment such as the lifting cylinder 420 that raises and lowers the seedling planting device W mounted as a field work device, and the planting clutch that functions as the work clutch for the seedling planting device W. The control device 408 is essentially built using computer programs, and includes a ridge detection module 481, an automatic steering unit 482, a vehicle behavior recording unit 483, a steering mode management unit 484, a travel route calculation unit 485, a travel distance calculation unit 486, and a posture determination unit 487. The ridge detection module 481 detects whether the vehicle C has reached the ridge area based on the following points: point A1, which is the reference point of the travel path set during the first work run, where the vehicle transitions from traveling in the ridge area to work run; point B1, where the vehicle transitions from work run to turning around in the ridge area; and the vehicle's position obtained from the positioning data of the positioning unit 461. As explained using Figures 43 and 44, point A1 is detected by the descent of the seedling planting device (working device) W to the lowering position (working position), and point B1 is detected by the rise of the seedling planting device W to the raised position (non-working position). These are recorded as vehicle behavior in the vehicle behavior recording unit 483. The travel path between point A1 and point B1 (generally a straight line) is the reference work travel path, and whether the steering is automatic or manual, the next work travel path is obtained by sequentially moving this reference work travel path in parallel by the interval between round-trip work runs. In other words, points B2, A3, B4, A5... corresponding to point A1, and points A2, B3, B4, A4, B5... corresponding to point B1 are estimated. This estimation algorithm is built into the ridge boundary estimation unit 810. The method for estimating the points indicating the boundary of the ridge area differs depending on the shape of the field, so a configuration that allows an appropriate estimation algorithm to be selected for each field shape is preferable. By comparing each of these points with the position of the vehicle, the distance until the working vehicle C reaches the ridge area is detected, and the control device 408 can output commands such as proximity notification when the vehicle approaches the ridge area by a predetermined distance, arrival notification when the vehicle reaches the ridge area, deceleration of the vehicle C, and stopping of the vehicle C. The travel path calculation unit 485 calculates the travel path data necessary for performing subsequent work driving with automatic steering, based on the above-mentioned standard work travel path. The automatic steering unit 482 calculates the difference between the travel path data calculated by the travel path calculation unit 485 and the vehicle's position, generates an automatic steering command, and outputs it to the steering unit U1. The steering mode management unit 484 manages the manual steering mode, which is driving with manual steering, and the automatic steering mode, which is driving with automatic steering. For example, it is possible to set the manual steering mode to be selected in the area near the edge of a field, and the automatic steering mode to be selected outside the area near the edge of a field (generally, driving in a straight line). It is also possible to forcibly select between the manual steering mode and the automatic steering mode by switching commands from the steering mode switching device 466. Furthermore, it is possible to set the system so that it forcibly switches from the automatic steering mode to the manual steering mode by operating the steering handle 443. The vehicle behavior recording unit 483 records the state of the vehicle, particularly the vehicle behavior related to the start and end of work runs, based on various sensor detection signals and operation signals from various operating devices input via the input signal processing unit 408a, and control signals output to the vehicle running equipment group 471 and the work equipment group 472 via the output signal processing unit 408b. At that time, each vehicle behavior is recorded together with the vehicle's position acquired at the time the vehicle behavior occurred. Figure 49 shows an example of vehicle behavior recorded chronologically by the vehicle behavior recording unit 483 during driving in a simplified field as shown in Figure 43. In this example, the recording items of the vehicle behavior recording unit 483 include recording number, behavior time, vehicle position, and behavior content. The behavior time is the time (timestamp) when the vehicle behavior was detected. The vehicle position is the vehicle's position when the vehicle behavior was detected. The behavior content identifies the detected vehicle behavior, and in this case, the operation of the driving mode switching device 465 (A means operation of button A, B means operation of button B), the position of the seedling planting device W and float 425, the state of the planting clutch (work clutch), and the steering state (steering from straight to turning, or steering from turning to straight) are recorded. In Figure 49, the vehicle's position is the same for each vehicle's behavior, but the vehicle's position differs because the timing of raising and lowering the seedling planting device W and the steering timing during turning differ. However, the recorded vehicle position is recorded after being corrected to replace it with the reference position of a specific vehicle. As can be seen from Figures 43 and 49, the various states of the traveling machine C and the working device, the seedling planting device W, in particular the start and end of the work can be read from the records of the vehicle behavior recording unit 483. As the first process of seedling planting work with this rice transplanter, the vehicle enters the area at the edge of the ridge from the ridge, and when it exits the area at the edge of the ridge, record No. "0001" is recorded. The contents of record No. "0001" are the record of point A1 in Figure 43, and include the time of the behavior, the vehicle's position, and the behavior details at that time. In terms of behavior details, the driving operation mode is "A", the seedling planting device position is "lowered position", the float position is "on the ground", and the clutch state is "engaged". In reality, the timing at which these behavior details are detected is slightly different, but here they are treated as the same timing. In other words, at the time when record No. "0001" is recorded, the driver pressed the A button on the driving mode switching device 465 and the settings for working were made. After this, the vehicle performs a straight-line operation, and when it reaches the edge of the ridge, record number "0002" is recorded. Record number "0002" is a record of point B1 in Figure 43, and includes the time of the operation, the vehicle's position, and the details of the operation. The details of the operation are that the driving operation mode is "B", the seedling planting device position is "raised position", the float position is "detached", the clutch state is "disengaged", and the steering is "straight to turning". In other words, at the time record number "0002" is recorded, the driver pressed the B button on the driving mode switching device 465 and set the vehicle to change direction. The positions of point A1 and point B1 are recorded by operating the A and B buttons on the driving mode switching device 465 in this way. The line connecting point A1 and point B1 can be used as a reference work route to estimate the driving route for subsequent operation runs. Therefore, operation of the driving mode switching device 465 is unnecessary at locations other than A1 and B1. Record No. "0003" is recorded when the vehicle has finished turning around in the ridge area, left the ridge area, and is about to perform work. Record No. "0003" is a record of point A2 in Figure 43, and includes the time of the action, the vehicle's position, and the details of the action. The position of point A2 is estimated by the ridge estimation unit 810 from point B1 using the round-trip work interval, assuming the field is as shown in Figure 43. Therefore, when the vehicle's position, acquired from the positioning unit 461, approaches or matches this estimated point B1, the work run can be set automatically. Alternatively, the system can notify the driver that the vehicle is approaching point B1 and prompt them to set the work run. Similarly, the position of point B2 is also estimated from point A1. Therefore, when the vehicle's position, acquired from the positioning unit 461, approaches or matches this estimated point B2, the turning around drive can be set automatically. Alternatively, the system can notify the driver that the vehicle is approaching point B2 and prompt them to set up a turnaround. As explained above, the timing of reaching the ridge edge area and the timing of leaving the ridge edge area can be determined from the position changes of the seedling planting device W and float 425, the switching operation of the work clutch, and the steering angle change. Therefore, the driving mode switching device 465, which acts as a teaching device to recognize the boundary of the ridge edge area, is not essential. The boundary of the ridge edge area can be determined by one or a combination of the vehicle behaviors described above. For example, when utilizing the characteristic of the seedling planting device W that it descends to the field surface at the start of work and rises from the field surface at the end of work, the transition point of the vehicle from the ridge edge area to the work area (non-ridge edge area) can be determined based on the state signal indicating the descending operation of the seedling planting device W from the raised position to the descending position, and the transition point of the vehicle from the work area (non-ridge edge area) to the ridge edge area can be determined based on the state signal indicating the ascending operation of the seedling planting device W from the descending position to the raised position. The control device 408 can be equipped with an algorithm that outputs various commands for executing various actions based on the determination result of the edge detection module 481 regarding the vehicle's arrival at the edge of the ridge. Some of these are listed below. (1) If the vehicle does not perform the recorded vehicle behavior when it reaches the point where the vehicle behavior is scheduled to be performed, the vehicle will decelerate, the engine will be stopped, etc. (2) When driving in a field, the location and time in which each vehicle behavior to be recorded occurs can be limited to a specific range. Therefore, by excluding vehicle behavior outside of this specific range from recording, the recording accuracy can be improved. (3) When it is detected that the vehicle has entered the area at the edge of the field, automatic steering is disabled. (4) If the steering behavior of the vehicle in the ridge area, such as steering angle and turning radius, differs from that of a turning maneuver, recording to the vehicle behavior recording unit 483 is stopped. For example, if the turning radius is large, it is considered not to be a turning maneuver but rather to a maneuver that is not a normal work maneuver, such as a maneuver to leave the field. (5) If an inappropriate vehicle speed is detected when a specific vehicle behavior occurs, the vehicle will be forcibly stopped. The distance traveled calculation unit 486 calculates the distance traveled by the vehicle C based on a detection signal from a sensor (one of the vehicle condition detection sensor group 409) that detects the rotation speed of the rear wheels 411 or the rotation speed of the transmission system to the rear wheels 411. If the slip ratio estimated from the field conditions is taken into consideration, the distance traveled can be calculated more accurately. In the case of the positioning unit 461, which calculates its own position based on radio wave signals from satellites, if the reception sensitivity of the radio wave signals decreases for any reason, it will not be able to output positioning data. The distance traveled calculation unit 486 is used to recover from this. For example, if positioning data is not input from the positioning unit 461, the ridge detection module 481 can detect that the vehicle C has reached the ridge area based on the distance traveled by the distance traveled calculation unit. The attitude determination unit 487 compares the attitude of the vehicle C with a predetermined tilt threshold based on a detection signal from a tilt sensor (one of the vehicle state detection sensor group 409) that detects the tilt angle (rolling angle and pitching angle) of the vehicle C. In this embodiment, if the attitude of the vehicle C deviates from the predetermined conditions, the attitude determination unit 487 issues a braking command to the braking device, which is one of the vehicle running equipment group 471, to decelerate or stop the vehicle. The specific control operations based on the determination results of the posture determination unit 487 are listed below. (1) If the detected tilt angle exceeds the tilt threshold, the system will issue a notification, decelerate, and stop. (2) If the detected tilt angle frequently exceeds the tilt threshold, automatic steering will be disabled. (3) If the detected slope angle exceeds the slope threshold for an allowable period of time, notification, deceleration, and stopping will be performed. This allowable period is determined depending on the vehicle speed and field depth. If the field depth exceeds a predetermined value, complete stopping will be prohibited to avoid the vehicle sinking into the ground. (4) The acceleration change due to the incline is calculated, and automatic steering is prohibited even if the incline is below the incline threshold when there is a sudden change in incline. [Another embodiment of the fifth embodiment] (1) In the above-described embodiment, points A1 and B1, which are the boundary points between the furrow-edge area where turning is performed and the non-furrow-edge area where work is performed, are determined by operating the A and B buttons of the driving mode switching device. Subsequent points A2, A3... and B2, B3... are estimated from points A1 and B1 and determined based on vehicle behavior. To simplify control, without using vehicle behavior, points A2, A3... and B2, B3... are estimated from points A1 and B1. If a position different from the estimated position is to be designated as the official point, the A or B button of the driving mode switching device may be operated again to determine the point. (2) The functional units in the functional block diagram shown in Figure 48 are primarily separated for explanatory purposes. In reality, each functional unit in Figure 48 can be integrated with other functional units or divided into multiple functional units. Independent functional units are connected to each other by an in-vehicle LAN, etc. (3) In the case of a rice transplanter, the vehicle behavior recorded in the vehicle behavior recording unit 483 may include, in addition to the above, the posture of the markers. In addition, vehicle behavior that occurs at the boundary between the ridge area and the non-ridge area should be recorded in the vehicle behavior recording unit 483. (4) In addition to the above-mentioned riding-type rice transplanter equipped with a seedling planting device as a working device, the present invention can be applied to various other work vehicles, such as a riding-type direct seeder which is a paddy field work vehicle equipped with a seeding device as a working device, a tractor equipped with a plow or the like as a working device, an agricultural work vehicle such as a combine harvester equipped with a harvesting unit or the like as a working device, or a construction work vehicle equipped with a bucket or the like as a working device. [First Embodiment] 28. Standard spare seedling tray (spare seedling tray) 29. Rail-type spare seedling tray (spare seedling tray) 30 spare seedling frames 31 Connecting Frame 62. Main Inertial Measuring Device (Inertial Measuring Device) 63 Receiving device 66 Harness 67 Connector section 68 Guard member 72 Rear axle 73. Rear axle frame (mounting component) 81 Generation part 83 Control Unit A. Traveling device C. Driving vehicle U Steering Unit W Seedling planting device (work device) S1 Usage Status S2 Storage state LM Target Line X Left and right axis center [Second Embodiment] 111 Driver's Unit 111a Entrance / Exit 120 Seedling planting device 130 Handrail 131 Upper end 131a Fixed part 131b Movable part 131f Front end side 150 Reserve seedling storage device 151. Reserve seedling stand 152. Spare seedling stand 153. Spare seedling stand 153b Spare seedling stand main body 153c Extension mounting platform 153r Rear end side 200 available spaces [Third Embodiment] 243 Manual steering operation tool (steering handle) 258 Steering operation means (steering motor) 261 Manual operation detection means (torque sensor) 264 Position detection means (position measurement unit) 266 Direction detection means (inertial measurement unit) 268 Route setting means (route setting unit) 269 ​​Control means (steering control unit) 270. Vehicle speed detection means (vehicle speed sensor) 300 Vehicles KA tilt target direction LK Target movement path NA detection direction (own aircraft direction) NM detection position (own aircraft position) TD Target direction (Teaching direction) Z1 Existing work area Z2 Unworked area α Tilt angle (set tilt angle) [Fourth Embodiment] 344 Main gear shift lever (gear shifting device) 350 Automatic steering switch (changeover switch) 352. Indicator button (indicator switch) 359 Displacement switch 359A Right displacement switch 359B Left displacement switch 376 Information Storage Unit (Recording Unit) 381 Starting point setting section 385 Operation Cancellation Section C. Driving vehicle KL Standard Driving Line S0 Starting point of the set driving line SL (Steam Locomotive) Set Running Line SB specified width [Fifth Embodiment] 407 Notification Devices 408 Control device 408a Input signal processing unit 408b Output signal processing unit 409 Vehicle condition detection sensor group 425 Float 426 Seedling stand 443 Steering wheel 444 Main gear shift lever 445 Operating lever 461 Positioning Unit 465 Driving mode switching device 466 Steering mode switching control 471 Vehicle running gear group 472 Working equipment equipment group 481. Ridge edge detection module 482 Automatic steering unit 483 Vehicle behavior recording unit 484 Steering Mode Management Unit 485 Route Calculation Unit 486 Mileage Calculation Unit 487 Posture determination unit 490 Contact detector 810 Ridge edge estimation section U1 Steering Unit W Seedling planting device (field work device)

Images