Method for controlling work vehicles, control program for work vehicles, control system for work vehicles, and work system

Abstract

To provide a control method of a work vehicle, a work vehicle control program, a work vehicle control system and a work system that enable appropriate determination of an override state.SOLUTION: A control method of a work vehicle 10 is a control method of a work vehicle 10 having an automatic steering mode for automatically steering a steered wheel using a motor 421. The control method includes, in the automatic steering mode, controlling the motor 421, determining whether the work vehicle is in an override state on the basis of a determination condition related to torque generated in the motor 421, and changing the determination condition.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a control method for a work vehicle having an automatic steering mode for automatically steering a steering wheel, a control program for a work vehicle, a control system for a work vehicle, and a work system.

Background Art

[0002] As a related art, an autonomous driving system for a work vehicle (tractor) that autonomously drives the work vehicle is known (see, for example, Patent Document 1). In the related art, autonomous driving control includes automatic steering control for automatically steering a steering wheel (left and right front wheels). This work vehicle is provided with a steering wheel that enables manual steering of the steering wheel via an electric power steering mechanism including, for example, an (electric) motor.

[0003] In automatic steering control, a steering angle setting unit obtains and sets a target steering angle of the steering wheel based on a target path and an output of a positioning unit, and outputs the set target steering angle to the power steering mechanism. Then, the power steering mechanism automatically steers the steering wheel based on the target steering angle and the output of a steering angle sensor so that the target steering angle is obtained as the steering angle of the steering wheel.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the configuration of the related technologies described above, during automatic steering, for example, when turning a work vehicle 90 degrees along a turning path, excessive torque may be generated in the power steering mechanism motor due to the sudden steering, potentially causing an override condition to be detected and automatic steering to be disengaged. Setting a higher torque threshold for determining an override condition would make it easier to avoid such problems, but in that case, the situation in which excessive torque is generated in the motor would last longer, potentially damaging the motor. Furthermore, a relatively large force would be required to operate the steering wheel to switch to manual steering, potentially reducing operator operability.

[0006] The object of the present invention is to provide a control method for a work vehicle, a control program for a work vehicle, a control system for a work vehicle, and a work system that enable the determination of an appropriate override state. [Means for solving the problem]

[0007] A control method for a work vehicle according to one aspect of the present invention is a control method for a work vehicle having an automatic steering mode in which the steering wheels are automatically steered using a motor, the method comprising: controlling the motor in the automatic steering mode; determining whether or not an override state is in place based on determination conditions relating to the torque generated in the motor; and changing the determination conditions.

[0008] A control program for a work vehicle according to one aspect of the present invention is a program that causes one or more processors to execute a control method for the work vehicle.

[0009] A control system for a work vehicle according to one aspect of the present invention is used in a work vehicle having an automatic steering mode in which the steering wheels are automatically steered using a motor, and comprises an automatic steering processing unit, an override determination processing unit, and a condition change processing unit. The automatic steering processing unit controls the motor in the automatic steering mode. The override determination processing unit determines whether or not an override state is in place based on determination conditions relating to the torque generated in the motor. The condition change processing unit changes the determination conditions.

[0010] A work system according to one aspect of the present invention comprises a control system for a work vehicle and the body of the work vehicle. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a control method for a work vehicle, a control program for a work vehicle, a control system for a work vehicle, and a work system that enable the determination of an appropriate override state. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a schematic side view showing the external appearance of a work vehicle according to Embodiment 1. [Figure 2] Figure 2 is a schematic block diagram of the work system according to Embodiment 1. [Figure 3] Figure 3 is a schematic diagram illustrating the operation of the steering wheel of a work vehicle according to Embodiment 1. [Figure 4] Figure 4 is a schematic diagram showing the configuration related to the steering device in the work system according to Embodiment 1. [Figure 5] Figure 5 is a schematic diagram illustrating the automated driving system in the work system according to Embodiment 1. [Figure 6] Figure 6 is a flowchart showing an example of a process related to steering angle determination processing in the control method for a work vehicle according to Embodiment 1. [Figure 7] Figure 7 is a graph showing an example of the change in motor torque due to the control method of the work vehicle according to Embodiment 1. [Figure 8] Figure 8 is a graph showing an example of the change in motor torque due to the control method of the work vehicle according to Embodiment 1. [Figure 9] Figure 9 is a graph showing an example of the relationship between the speed command value and the torque threshold in the control method for a work vehicle according to Embodiment 1. [Figure 10] Figure 10 is a graph showing an example of the change in motor torque due to the control method of the work vehicle according to Embodiment 1. [Figure 11] FIG. 11 is a schematic diagram showing an example of assignment of determination conditions in the control method of the work vehicle according to Embodiment 1. [Figure 12] FIG. 12 is a schematic diagram showing an example of assignment of determination conditions in the control method of the work vehicle according to Embodiment 1. [Figure 13] FIG. 13 is a flowchart showing an example of processing related to override determination processing in the control method of the work vehicle according to Embodiment 1. [Figure 14] FIG. 14 is a schematic diagram showing an example of assignment of determination conditions in the control method of the work vehicle according to Embodiment 1. [Figure 15] FIG. 15 is a schematic diagram showing an example of assignment of determination conditions in the control method of the work vehicle according to Embodiment 1. [Figure 16] FIG. 16 is a schematic explanatory diagram showing an example of the relationship between the pitch angle and the torque threshold value in the control method of the work vehicle according to Embodiment 2. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The following embodiments are an example of embodying the present invention and are not intended to limit the technical scope of the present invention.

[0014] (Embodiment 1) [1] Overall Configuration First, the overall configuration of the work system 100 according to the present embodiment will be described with reference to FIGS. 1 and 2. The work vehicle control system 1 (hereinafter, also simply referred to as "control system 1") according to the present embodiment constitutes the work system 100 together with the vehicle body 11 of the work vehicle 10. A work implement 12 is attached to the vehicle body 11. That is, the work system 100 includes the work vehicle control system 1 and the vehicle body 11 of the work vehicle 10 (to which the work implement 12 is attached).

[0015] In this embodiment, the control system 1 includes a control device 2 (see Figure 2) mounted on the body 11 of the work vehicle 10 and a terminal device 3. The work vehicle 10 and the terminal device 3 are able to communicate with each other. In this disclosure, "able to communicate" means that information can be exchanged directly or indirectly via a communication network or relay device, etc., by an appropriate communication method such as wired communication or wireless communication (communication using radio waves or light as a medium). The communication network includes, for example, the Internet, LAN (Local Area Network), WAN (Wide Area Network), public telephone lines, mobile phone networks, packet networks, or wireless LANs. The ability of the work vehicle 10 and the terminal device 3 to communicate with each other is not an essential configuration in the control system 1.

[0016] The work vehicle 10 moves through the target area F1 (see Figure 1) and performs some work within the target area F1 using the work implement 12. In this disclosure, "work" refers to the work performed by the work implement 12 on the target area F1, and includes various agricultural operations such as tilling, leveling, sowing, fertilizing, pesticide spraying, planting (rice planting), or harvesting, as well as various construction operations. In this embodiment, as an example, the work performed by the work vehicle 10 is tilling.

[0017] The implement 12 performs work within the target area F1 as the body 11 of the work vehicle 10 moves through the target area F1. In this embodiment, as an example, the implement 12 is a tiller such as a rotary tiller or plow that performs tilling work.

[0018] This type of implement 12 includes a directly mounted implement that is directly attached to a three-point linkage, and a towed implement that is towed by the machine body 11. In this embodiment, as an example, the implement 12 is a directly mounted rotary tiller that is detachably attached to the machine body 11 of the work vehicle 10. Here, the implement 12 is attached to the rear side of the machine body 11 (opposite the direction of forward movement of the machine body 11). In other words, the (directly mounted) implement 12 is connected to the rear side of the machine body 11 and performs work while moving forward with the machine body 11 when the machine body 11 moves forward. In this embodiment, the implement 12 is included as a component of the work vehicle 10, but since the implement 12 is detachable from the machine body 11, it does not have to be included as a component of the work vehicle 10.

[0019] In this disclosure, "work vehicle" means a vehicle that performs various tasks in a target area F1 such as a field, and as an example, agricultural machinery such as a tractor, seeder, rice transplanter, sprayer, sprayer, transplanter, and harvester. The work vehicle 10 may also be, for example, construction machinery. In this embodiment, unless otherwise specified, the explanation will be given using the example of a tractor equipped with a rotary tiller as the implement 12 as the work vehicle 10. In other words, the work vehicle 10 is constructed by connecting a (directly mounted) rotary tiller as the implement 12 to a tractor as the machine body 11. With this work vehicle 10, tilling work in the target area F1 such as a field becomes possible as the machine body 11 travels over the target area F1.

[0020] Thus, in this embodiment, the machine 11 is a type of vehicle that moves by traveling through the target area F1. Here, as shown in Figures 1 and 3, the machine 11 is equipped with steering wheels 111 consisting of a pair of left and right front wheels, and drive wheels 112 consisting of a pair of left and right rear wheels, and travels through the target area F1 using these four wheels (the pair of steering wheels 111 and the pair of drive wheels 112).

[0021] Furthermore, in this embodiment, as an example, the work vehicle 10 is an automated machine that can operate by automatic driving (autonomous driving, etc.) while also being capable of carrying a person (operator). However, it is not limited to this, and the work vehicle 10 may be an unmanned machine that drives automatically, or it may be operated by a person (operator) (including remote control).

[0022] In this disclosure, the "target area" refers to an area in which the work vehicle 10 performs various operations such as tilling, leveling, sowing, fertilizing, pesticide spraying, planting (rice planting), or harvesting while moving, and includes paddy fields, dry fields, orchards, and pastures. For example, if the target area F1 is a paddy field or dry field where crops (agricultural products) such as rice, wheat, soybeans, or buckwheat are grown, the crops grown in the target area F1 are agricultural products. Furthermore, if trees are grown in a nursery, the nursery becomes the target area F1, and if trees that will become timber are grown in a forest, as in forestry, the forest becomes the target area F1. In this case, the crops grown in the target area F1 are trees or shrubs. In this embodiment, unless otherwise specified, the work vehicle 10 is used for tilling work in a field (target area F1), and the explanation will be given using the example that the target area F1 is a paddy field for growing rice. Furthermore, the target area F1 is not limited to fields; for example, if the work vehicle 10 is a construction machine, then the site where the construction machine performs its work becomes the target area F1.

[0023] Furthermore, the work vehicle 10 can move automatically not only within the target area F1 (in this case, the field) but also on roads outside the target area F1, such as off-field routes. The work vehicle 10 is configured to automatically travel (move) along pre-set target routes (including off-field routes) both within and outside the target area F1, based on positional information of the work vehicle 10's current position, which is determined by the positioning device 15 (see Figure 2). Off-field routes are, for example, inter-field connecting roads that connect multiple target areas F1 (fields). Inter-field connecting roads may be farm roads, forest roads, public roads, private roads, or automobile roads, and may be roads exclusively for the work vehicle 10 or roads that are accessible to general vehicles (passenger cars, etc.).

[0024] Furthermore, the term "autonomous driving" as used in this disclosure includes "autonomous driving," in which the work vehicle 10 drives autonomously without operator intervention, and "semi-autonomous driving," in which only steering is automated, such as with straight-line assist.

[0025] "Autonomous driving" is a driving mode in which, for example, the steering wheels 111 are automatically steered, and the vehicle speed and other parameters are also automatically controlled, so that the work vehicle 10 travels along a target route. "Straight-line assist" is a driving mode in which, for example, the steering wheels 111 are automatically steered, and the vehicle speed and other parameters are controlled by the operator, so that the work vehicle 10 travels along a straight route parallel to a reference straight line (reference line). In other words, in "semi-autonomous driving," the work vehicle 10 cannot travel without operator input, but the burden of steering is reduced for the operator, and because it can travel along a target route such as a straight route, it leads to improved work efficiency. Furthermore, in both autonomous driving and semi-autonomous driving, the steering wheels 111 are automatically steered, so it can be said that this is a form of "automatic steering mode."

[0026] In automatic steering mode, the steering wheels 111 are automatically steered by the motor 421 (see Figure 4). In other words, instead of the operator operating the steering wheel 41 (see Figure 1), automatic steering is achieved by changing the direction of the steering wheels 111 with the output of the motor 421. In short, the work vehicle 10 according to this embodiment has an automatic steering mode in which the steering wheels are automatically steered using the motor 421.

[0027] [2] Composition of work vehicles Next, the configuration of the work vehicle 10 according to this embodiment will be described in detail with reference to Figures 1 to 3.

[0028] In this embodiment, for the sake of explanation, the vertical direction when the work vehicle 10 is in a usable state is defined as the up-down direction D1 (see Figure 1). The forward-backward direction D2 and left-right direction D3 (see Figure 3) are defined based on the direction as seen from the perspective of the person (operator) sitting in the machine body 11 (or its driver's unit 113) of the work vehicle 10. The left side of the left-right direction D3 refers to the left side when the machine body 11 is traveling forward (moving forward), and the right side of the left-right direction D3 refers to the right side when the machine body 11 is traveling forward (moving forward). However, these directions are not intended to limit the direction of use (direction during use) of the work vehicle 10.

[0029] As shown in Figure 2, the work vehicle 10 is equipped with a control device 2, a traveling device 13, a steering device 14, a positioning device 15, a detection device 16, a communication device 17, a power source 18, and an operating device 19, in addition to the main body 11 and the work machine 12. The control device 2, traveling device 13, steering device 14, positioning device 15, detection device 16, communication device 17, power source 18, and operating device 19 are all mounted on the main body 11.

[0030] The machine body 11 has a driver's compartment 113 (see Figure 1) on which a person (operator) can board. The driver's compartment 113 is equipped with a steering wheel 41 (see Figure 3), a gear shift lever, and an operating device 19, which are part of the steering system 14. The steering wheel 41, gear shift lever, and operating device 19 are operating parts that are operated by the operator. Therefore, the work vehicle 10 is configured to be able to be driven not only automatically but also manually by the operator. In addition, as described above, a work implement 12 is detachably connected to the rear of the machine body 11. It is also possible to connect a device other than the work implement 12 to the machine body 11.

[0031] In this embodiment, the implement 12 is a directly mounted rotary tiller, so tilling can be performed on the field, which is the target area F1, when the machine body 11 is moving forward. The implement 12 has a variable relative position (relative height) in the vertical direction D1 with respect to the machine body 11. As a result, the height of the implement 12 is variable when the field surface, which is the ground surface of the target area F1, is used as a reference. For example, by raising the implement 12 to a height away from the ground surface of the target area F1, the work vehicle 10 can also travel in a non-working state without performing work with the implement 12.

[0032] As shown in Figure 1, the running gear 13 is a device that drives the work vehicle 10 by driving the drive wheels 112, which consist of a pair of rear wheels (left and right). The running gear 13 includes a transmission and transmits the power generated by the power source 18 to the drive wheels 112 via the transmission, thereby moving the machine body 11 forward or backward. Furthermore, the running gear 13 includes a brake device and can also decelerate or stop the machine body 11. In this embodiment, the drive wheels 112 are ordinary wheels, but it is not limited to this, and for example, the machine body 11 may be a half-crawler type with crawler tracks (tracks) used for the drive wheels 112.

[0033] As shown in Figure 1, the steering device 14 is a device that steers the steering wheels 111, which consist of a pair of front wheels (left and right). The steering device 14 includes a steering wheel 41 and steers the steering wheels 111 in response to the operator's operation on the steering wheel 41. As shown in Figure 3, the pair of steering wheels 111 have a reference posture in a plan view where they are facing in the longitudinal direction D2, that is, a posture where the axis of rotation is aligned with the left-right direction D3, and the steering device 14 steers them so that they tilt to the left or right from the reference posture. In other words, the steering device 14 steers the steering wheels 111 by changing the orientation of the pair of steering wheels 111.

[0034] Figure 3 schematically illustrates the operation of the steering wheels 111 in response to the operation of the steering handle 41. That is, as shown in Figure 3, when the steering handle 41 is operated clockwise from the position of the pair of steering wheels 111 in a reference position, the steering device 14 steers the pair of steering wheels 111 (front ends) to the right, causing the aircraft 11 to turn to the right when moving forward. On the other hand, when the steering handle 41 is operated counterclockwise from the position of the pair of steering wheels 111 in a reference position, the steering device 14 steers the pair of steering wheels 111 (front ends) to the left, causing the aircraft 11 to turn to the left when moving forward. In this embodiment, the operator operates the steering handle 41 during manual steering, but it is not limited to this, and manual steering may be performed by the operator operating, for example, an operating lever.

[0035] With the running gear 13 and steering gear 14, the aircraft 11 can move within the target area F1 in the longitudinal direction D2 and the lateral direction D3. For example, when the driving wheels 112 are driven by the running gear 13 and the aircraft 11 is moving forward, if the angle of the steering wheels 111 is changed by the steering gear 14, the aircraft 11 will turn in the lateral direction D3 and the direction of travel of the aircraft 11 will be changed.

[0036] The positioning device 15 determines the current position (latitude, longitude, and altitude, etc.) of the aircraft 11. Specifically, the positioning device 15 is, for example, located on the roof of the control unit 113 and calculates the current position (latitude and longitude) of the aircraft 11 using a satellite positioning system such as GNSS (Global Navigation Satellite System). In other words, the positioning device 15 has a positioning antenna that receives positioning signals from multiple satellites 202 (see Figure 1) and calculates the current position based on the positioning signals. Furthermore, the positioning device 15 includes an inertial sensor and can also detect the attitude of the aircraft 11, such as its current bearing.

[0037] Furthermore, the positioning device 15 employs a relatively high-precision positioning method, such as RTK (Real Time Kinematic) positioning, which calculates the current position of the work vehicle 10 by utilizing correction information corresponding to a base station 201 (reference station) close to the work vehicle 10. The current position of the aircraft 11 may be the same as the positioning position (position of the positioning antenna), or it may be a position shifted from the positioning position, such as the center position of the aircraft 11 in a plan view. For example, a mobile phone terminal, smartphone, or tablet terminal may be used as the positioning device 15.

[0038] The detection device 16 detects obstacles in the detection area. The detection device 16 includes an obstacle sensor and a detection processing unit. The obstacle sensor may include various sensors such as a camera (image sensor), sonar sensor, human presence sensor, radar, or LiDAR (Light Detection and Ranging). The obstacle sensor may be a 3D sensor that measures the distance to an object (obstacle) using the TOF (Time Of Flight) method, which measures the distance to the distance measurement point based on the round-trip time it takes for light or sound to reach the distance measurement point and return. The detection processing unit detects obstacles based on the measurement information obtained from the obstacle sensor. Here, the detection processing unit may only detect the presence or absence of obstacles, or it may detect the position, shape, number, or attributes (including type, etc.) of the obstacles.

[0039] The detection results from the detection device 16 are output to the control device 2. When the detection device 16 detects an obstacle during the automatic driving of the work vehicle 10, the control device 2 outputs an alarm (including notification by sound and / or light) and performs obstacle avoidance processing (including detour, deceleration, or stopping) by controlling the driving device 13 and steering device 14. Furthermore, the control device 2 may output the location information of the obstacle and the execution history of the avoidance processing to the terminal device 3 and display it on the terminal device 3.

[0040] The communication device 17 is a communication interface for connecting the work vehicle 10 (control device 2 and positioning device 15, etc.) to an external device by wire or wireless connection and for performing data communication with the external device in accordance with a predetermined communication protocol. In this embodiment, the communication device 17 is capable of communicating with at least the terminal device 3, which is an external device. For example, a mobile phone terminal, smartphone, or tablet terminal may be used as the communication device 17.

[0041] The power source 18 is a drive source that supplies power to at least the running gear 13. The power source 18 has an engine, such as a diesel engine. Furthermore, the power source 18 drives a hydraulic pump and supplies hydraulic fluid from the hydraulic pump to the hydraulic cylinders of the power steering mechanism 43 (see Figure 4) of the steering gear 14. In other words, the power source 18 is configured to also supply power to the power steering mechanism 43.

[0042] The operating device 19 is a device that receives operator input. The operating device 19 can, for example, receive switching operations between an automatic steering mode in which the steering wheels 111 are automatically steered and a manual steering mode in which the steering wheels 111 are manually steered. The operating device 19 outputs a signal to the control device 2 corresponding to the received operation.

[0043] The control device 2 primarily consists of a computer system having one or more processors such as a CPU (Central Processing Unit) and one or more memories such as ROM (Read Only Memory) and RAM (Random Access Memory), and performs various processes (information processing). In this embodiment, since the control device 2 primarily consists of a computer system having one or more processors, the control device 2 is realized when one or more processors execute a control program for the work vehicle. In this embodiment, the control device 2 is an integrated controller that controls the entire work vehicle 10, and consists of, for example, an electronic control unit (ECU). However, the control device 2 may be provided separately from the integrated controller.

[0044] The control device 2 is configured to communicate with devices provided in various parts of the machine body 11. In other words, the control device 2 is electrically connected to the work equipment 12, the travel equipment 13, the steering equipment 14, the positioning device 15, the detection device 16, the communication device 17, the power source 18, and the operating device 19, etc. As a result, the control device 2 can control the work equipment 12, the travel equipment 13, the steering equipment 14, etc., and acquire the outputs of the positioning device 15, the detection device 16, and the operating device 19, etc. Here, the control device 2 may exchange various types of information (data) directly with each device, or it may do so indirectly via a relay or the like.

[0045] In this embodiment, the control device 2, as shown in Figure 2, includes a driving control unit 21, a steering control unit 22, a work control unit 23, and a storage unit 24.

[0046] The driving control unit 21 controls the driving device 13 and the power source 18. At least during autonomous driving, the driving control unit 21 controls the driving device 13 and the power source 18 to bring the vehicle speed, engine speed, etc., closer to target values, on behalf of the operator. The driving control unit 21 can also control the brake device of the driving device 13 to decelerate or stop the machine 11.

[0047] The steering control unit 22 controls the steering device 14. The steering control unit 22 has two operating modes: an automatic steering mode and a manual steering mode, and is configured to be switchable between the automatic steering mode and the manual steering mode. The manual steering mode is a mode in which the operator steers by operating the steering wheel 41. At least during autonomous or semi-autonomous driving, the steering control unit 22 operates in automatic steering mode and controls the steering device 14 to bring the steering angle of the steering wheels 111 closer to the target steering angle, on behalf of the operator.

[0048] In particular, during autonomous driving, the steering control unit 22, together with the driving control unit 21, controls the work vehicle 10 based on the current position of the vehicle 11 so that the vehicle 11 travels along the target path. The target path for autonomous driving of the work vehicle 10 is generated, for example, in the terminal device 3. That is, the work vehicle 10 obtains path data corresponding to the target path from the terminal device 3 and drives autonomously according to the target path. More details about the steering control unit 22 will be explained in the section "[4] Configuration related to the steering device".

[0049] The work control unit 23 controls the work machine 12. The driving control unit 21 controls the work machine 12 based on the current position of the vehicle 11 on the target path, at least during autonomous driving. Specifically, if the work vehicle 10 is traveling along a work path on the target path in which work is to be performed by the work machine 12, the work control unit 23 sets the work machine 12 to the work position and performs work with the work machine 12. On the other hand, if the work vehicle 10 is traveling along a non-work path on the target path in which work is not to be performed by the work machine 12, the work control unit 23 raises the work machine 12 to the non-work position and stops work with the work machine 12.

[0050] The memory unit 24 is a non-volatile memory that stores various data such as the control program for the work vehicle and target route information related to the target route. In other words, the driving control unit 21 and the steering control unit 22 can, for example, perform autonomous driving along the target route based on the target route information stored in the memory unit 24.

[0051] In addition to the above-described configuration, the work vehicle 10 is further equipped with a battery, fuel tank, display device, and various sensors. The battery supplies power for operation to various parts of the work vehicle 10, such as the control device 2. In particular, electronic devices such as the control device 2, steering device 14, positioning device 15, detection device 16, and communication device 17 can operate even when the power source 18 is stopped, as they are powered by the battery. The display device is a user interface for presenting information to the user (operator), such as a liquid crystal display or organic EL display that displays various types of information.

[0052] [3] Configuration of terminal device Next, the configuration of the terminal device 3 according to this embodiment will be described in detail with reference to Figures 1 and 2.

[0053] In this embodiment, the terminal device 3 is capable of communicating with the work vehicle 10 as described above, and together with the control device 2 of the work vehicle 10, constitutes the control system 1. In other words, the components of the control system 1 are distributed between at least the work vehicle 10 and the terminal device 3. However, the configuration is not limited to this, and for example, the functions of the terminal device 3 may be provided in the control device 2, in which case the components of the control system 1 will be realized by the control device 2 alone.

[0054] In this embodiment, as an example, the terminal device 3 is composed of a general-purpose terminal such as a tablet, smartphone, or laptop computer. As shown in Figure 1, the terminal device 3 is located in the operating unit 113 of the machine body 11. The terminal device 3, which consists of a general-purpose terminal, has dedicated application software (program) installed on it, and by starting this application software, the terminal device 3 functions as the terminal device 3 of the control system 1.

[0055] The terminal device 3 comprises a display unit 31 and an operation unit 32. The display unit 31 includes, for example, a liquid crystal display or an organic EL display. The operation unit 32 includes, for example, a touch panel, physical switches, a mouse, or a keyboard. In this embodiment, as an example, the display unit 31, which is a liquid crystal display, and the operation unit 32, which is a touch panel, are integrated to form a touch panel display. Therefore, when the operation unit 32 is operated while a display screen is shown on the display unit 31, the terminal device 3 can accept user input on the display screen.

[0056] Terminal device 3 is used to input various settings related to the operation of the work vehicle 10 and to output control signals related to the control of the work vehicle 10. Specifically, terminal device 3 has the function of setting (registering) various information related to the control of the work vehicle 10, such as a target route for the automatic driving of the work vehicle 10. In other words, the operator can set the target route, etc. by operating the operation unit 32 on the display screen displayed on the display unit 31. The information such as the target route set here is transmitted directly or indirectly to the work vehicle 10 and used for the automatic driving of the work vehicle 10. Furthermore, terminal device 3 is configured to enable the operation of the work vehicle 10 by outputting (transmitting) at least a control signal to the work vehicle 10 to stop the automatic driving of the work vehicle 10 in response to the operator's operation.

[0057] Furthermore, while the work vehicle 10 is automatically driving, the terminal device 3 can display various information related to the operation of the work vehicle 10, such as the current position, current direction, and (spraying) work status, on the display unit 31. For example, the terminal device 3 can display a monitoring screen on the display unit 31 that shows the current position of the work vehicle 10 along with the target route on a map that mimics the target area F1, making it easier for the operator to visually grasp the status of the work vehicle 10.

[0058] [4] Configuration related to the steering system Next, the configuration related to the steering device 14 will be described in detail with reference to Figures 3 and 4. Figure 4 schematically shows how the steering wheel 111 is steered by the configuration related to the steering device 14 (steering device 14, steering control unit 22, and memory unit 24).

[0059] As described above, the steering device 14 is a device for steering the steering wheels 111, which consist of a pair of left and right front wheels, and changes the direction of the steering wheels 111, i.e., the steering angle θ1, in response to the operator's operation on the steering handle 41. The steering angle θ1 is the angle of inclination of the steering wheels 111 with respect to the reference posture, as shown in Figure 3. In other words, when the steering wheels 111 are in the reference posture along the longitudinal direction D2 (the state shown in the center of Figure 3), the steering angle θ1 is 0 degrees.

[0060] In this state, when the steering wheel 41 is operated, the steering device 14 tilts the steering wheel 111 by a steering angle θ1 corresponding to the amount of operation of the steering wheel 41 in the direction of operation of the steering wheel 41. In short, in manual steering mode, the steering angle θ1 changes according to the operation of the steering wheel 41. In this embodiment, as an example, the steering angle θ1 when the steering wheel 111 is tilted to the right from the reference position (the state shown on the right side of Figure 3) is defined as "positive," and the steering angle θ1 when the steering wheel 111 is tilted to the left from the reference position (the state shown on the left side of Figure 3) is defined as "negative." Furthermore, in this embodiment, as an example, it is assumed that the steering angles θ1 of the left front wheel and the right front wheel, which are a pair of steering wheels 111, are the same.

[0061] In this embodiment, as shown in Figure 4, the steering device 14 further includes a steering operation unit 42, a power steering mechanism 43, a steering angle sensor 44, and a stopper mechanism 45 in addition to the steering wheel 41.

[0062] The power steering mechanism 43 is a mechanism that steers a pair of steering wheels 111 in conjunction with the operation of the steering wheel 41, at least in manual steering mode. In other words, when the operator operates the steering wheel 41, the power steering mechanism 43 amplifies this operating force, thereby actually steering the pair of steering wheels 111. In this embodiment, as an example, the power steering mechanism 43 is hydraulic, and the pair of steering wheels 111 are driven by a hydraulic actuator such as a hydraulic cylinder. Therefore, the amplification rate of the operating force by the power steering mechanism 43 changes according to the engine speed of the power source 18. Thus, for example, when the engine speed decreases, the amplification rate of the operating force by the power steering mechanism 43 also decreases, the force required to operate the steering wheel 41 increases, and the steering wheel 41 (feeling of operation) becomes heavier.

[0063] The steering control unit 42 is a device for steering a pair of steering wheels 111 in place of operating the steering wheel 41 in automatic steering mode. The steering control unit 42 includes a motor 421 and a motor driver 422.

[0064] Motor 421 is an electric motor that is driven by a drive signal (electrical signal) from the motor driver 422. The output of motor 421 is supplied to the power steering mechanism 43. Therefore, the steering operation unit 42 can steer the pair of steering wheels 111 by operating the power steering mechanism 43 with motor 421 instead of operating the steering wheel 41.

[0065] The motor driver 422 drives the motor 421 by outputting a drive signal to the motor 421. The motor driver 422 receives a command value from the steering control unit 22 (specifically the automatic steering processing unit 53) and drives the motor 421 according to that command value. Here, "command value" can be, for example, a speed command value related to the rotational speed of the motor 421, a current command value related to the drive current of the motor 421, a torque command value related to the torque of the motor 421, and a position command value related to the rotational position of the motor 421. For example, upon receiving a speed command value, the motor driver 422 controls the speed of the motor 421 so that its rotational speed approaches the speed command value.

[0066] Here, the motor driver 422 is capable of rotating the motor 421 in both directions and driving the motor 421 at any rotational speed. In this embodiment, as an example, when the motor 421 rotates in the forward direction, the steering angle θ1 of the steering wheel 111 changes to the positive direction (i.e., to the right), and when the motor 421 rotates in the reverse direction, the steering angle θ1 of the steering wheel 111 changes to the negative direction (i.e., to the left). Therefore, the steering operation unit 42 can steer the pair of steering wheels 111 to any steering angle θ1 via the power steering mechanism 43, similar to the operation of the steering wheel 41 by an operator.

[0067] The steering angle sensor 44 is a sensor that detects the current steering angle θ1 of a pair of steering wheels 111. The steering angle sensor 44 is configured using, for example, a potentiometer, and outputs a steering angle signal corresponding to the steering angle θ1 to the steering control unit 22 of the control device 2 periodically or irregularly. In this embodiment, as described above, the steering angles θ1 of the left front wheel and the right front wheel, which are a pair of steering wheels 111, are the same, so the steering angle sensor 44 detects the steering angle θ1 of either one of the pair of steering wheels 111.

[0068] The stopper mechanism 45 is a mechanism that limits the range of motion of the pair of steering wheels 111. In other words, the steering angle θ1 of the pair of steering wheels 111 cannot be changed indefinitely, and the pair of steering wheels 111 can only be steered up to the maximum steering angle. In this disclosure, "maximum steering angle" means how much angle the steering wheels 111 can be angled with respect to the longitudinal direction D2. When the (pair of) steering wheels 111 are turned (tilted) from the reference position to the maximum steering angle, they cannot be turned (tilted) any further, and the maximum steering angle is the physical upper limit of the steering angle θ1. In this disclosure, the state in which the steering wheels 111 are steered to the maximum steering angle is called the "end-steering state".

[0069] Since the steering wheel 111 can be steered in both the positive direction (i.e., to the right) and the negative direction (i.e., to the left) of the steering angle θ1 from the reference position, there are both positive and negative maximum steering angles. Therefore, the steering angle θ1 of the pair of steering wheels 111 can vary within the range from the maximum left steering angle (negative steering angle θ1) when the left wheel is fully turned to the left, to the maximum right steering angle (positive steering angle θ1) when the right wheel is fully turned to the right.

[0070] As an example, the stopper mechanism 45 has an adjustment bolt mounted near the axis of the steering wheel 111, and the maximum steering angle can be adjusted by changing the length of the adjustment bolt. With this stopper mechanism 45, a person can adjust the desired maximum steering angle by turning the adjustment bolt to adjust its length. Here, the stopper mechanism 45 has an adjustment bolt for adjusting the maximum steering angle on the left and an adjustment bolt for adjusting the maximum steering angle on the right, and these adjustment bolts can be adjusted individually. Therefore, the maximum steering angle can be set individually for the left and right sides.

[0071] Thus, in this embodiment, the maximum steering angle is defined by the stopper mechanism 45 that limits the range of motion of the steering wheel 111. Therefore, the stopper mechanism 45 can physically prevent the steering wheel 111 from being steered beyond its range of motion, thereby keeping the load on the steering device 14 low. In particular, as in this embodiment, since a person can adjust the maximum steering angle by operating the stopper mechanism 45, a desired maximum steering angle can be set according to the use of the work vehicle 10, the target area F1, etc.

[0072] Furthermore, the steering control unit 22 that controls the steering device 14, in this embodiment as shown in Figure 4, includes an acquisition processing unit 51, a mode switching processing unit 52, an automatic steering processing unit 53, an override determination processing unit 54, a condition change processing unit 55, a steering angle determination processing unit 56, and a maximum angle setting processing unit 57.

[0073] The acquisition processing unit 51 performs an acquisition process to acquire electrical signals (including data) from each device. In this embodiment, the acquisition processing unit 51 acquires at least a steering angle signal from the steering angle sensor 44. Furthermore, the acquisition processing unit 51 acquires information related to the driving state of the motor 421 from the steering operation unit 42, such as torque, rotational speed, and current.

[0074] The mode switching processing unit 52 performs a mode switching process to switch the operating mode (of the work vehicle 10) between manual steering mode and automatic steering mode. Basically, the mode switching processing unit 52 switches the operating mode from manual steering mode to automatic steering mode when automatic driving (including autonomous driving and semi-automatic driving) starts, and switches the operating mode from automatic steering mode to manual steering mode when automatic driving ends.

[0075] Furthermore, when the mode switching processing unit 52 determines that an override state, as described later, is in effect, it switches the operating mode of the work vehicle 10 from automatic steering mode to manual steering mode, in which the operator manually steers the vehicle. The override state is a state in which, while operating in automatic steering mode, input is provided to the power steering mechanism 43 from both the steering operation unit 42 and the steering wheel 41, for example, by operating the steering wheel 41. When such an override state occurs, even if automatic driving is continuing, the mode switching processing unit 52 forcibly switches from automatic steering mode to manual steering mode. Therefore, the operator can forcibly terminate the automatic steering mode simply by operating the steering wheel 41 while operating in automatic steering mode, improving operability.

[0076] The automatic steering processing unit 53 performs automatic steering processing to control the motor 421 in automatic steering mode. The automatic steering processing unit 53 controls the steering device 14 (motor 421) so that the steering angle θ1 of the steering wheel 111 approaches the target steering angle. In this embodiment, as an example, the automatic steering processing unit 53 outputs command values ​​such as speed command values ​​to the motor driver 422 of the steering operation unit 42, and controls the motor 421 by having the motor driver 422 drive the motor 421 according to the command values. Here, in automatic steering mode, the automatic steering processing unit 53 steers the pair of steering wheels 111 as needed and adjusts the steering angle θ1 as needed so that the work vehicle 10 travels along the target path.

[0077] The override determination processing unit 54 performs an override determination process to determine whether or not an override state is in place in automatic steering mode. Here, the override determination processing unit 54 determines whether or not an override state is in place based on determination conditions related to the torque generated in the motor 421. For example, if the motor 421 generates torque exceeding a threshold for a certain period of time, it is presumed that the steering wheel 41 is being operated by the operator. In such a case, the override determination processing unit 54 determines that the determination conditions are met and determines that an override state is in place.

[0078] The condition change processing unit 55 executes a condition change process to change the determination conditions. The "determination conditions" referred to here are the conditions used by the override determination processing unit 54 to determine whether or not an override state is in place. In other words, in this embodiment, the "determination conditions" used to determine the override state are not fixed, but can be changed by the condition change processing unit 55.

[0079] The steering angle determination processing unit 56 performs a steering angle determination process to determine whether or not the steering wheel is in the fully steered state in automatic steering mode. Here, the steering angle determination processing unit 56 determines whether or not the steering wheel 111 is in the fully steered state, where it has been steered to its maximum steering angle, based on the steering angle determination conditions. For example, if the steering angle θ1 is greater than or equal to a predetermined angle (the angle at which the stopper mechanism 45 can act), the steering angle θ1 hardly changes, a torque of a predetermined value or more is generated in the motor 421, and the direction of the torque matches the command value, and this state continues for a certain period of time, it can be inferred that the steering wheel 111 is steered to its maximum steering angle. In such a case, the steering angle determination processing unit 56 determines that the steering angle determination conditions are met and determines that the steering wheel is in the fully steered state. The "steering angle determination conditions" are different conditions from the "determination conditions" used to determine whether or not the system is in an override state, and in this embodiment, they are predetermined and fixed conditions.

[0080] The maximum angle setting processing unit 57 executes a maximum angle setting process to set the maximum steering angle in automatic steering. Here, the maximum angle setting processing unit 57 sets the maximum steering angle based on the steering angle θ1 of the steering wheel 111 when it is determined by the steering angle determination process that it is in a fully turned state. The "maximum steering angle" as used in this disclosure is the angle that is the maximum value of the target steering angle when the automatic steering processing unit 53 controls the steering device 14 (motor 421) in automatic steering mode. In other words, when automatic steering is performed, the steering angle θ1 is controlled within a range less than or equal to the maximum steering angle.

[0081] The maximum steering angle setting processing unit 57 sets the maximum steering angle by storing (writing) the value of the maximum steering angle in the storage unit 24 of the control device 2. The storage unit 24 has a left maximum steering angle storage area 241 and a right maximum steering angle storage area 242 that store the maximum steering angle set by the maximum steering angle setting processing unit 57. The left maximum steering angle storage area 241 stores the negative direction, i.e., the maximum steering angle to the left, set by the maximum steering angle setting processing unit 57. The right maximum steering angle storage area 242 stores the positive direction, i.e., the maximum steering angle to the right, set by the maximum steering angle setting processing unit 57.

[0082] Thus, in this embodiment, the maximum steering angle is set individually for each steering direction (left and right) of the steering wheel 111. This allows for the setting of an appropriate maximum steering angle based on the steering angle θ1 when the steering wheel is fully turned, compared to the case where the maximum steering angle is set uniformly regardless of the steering direction.

[0083] [5] Control method for work vehicles Referring to Figures 5 to 15, an example of a control method for the work vehicle 10, primarily performed by the control system 1 (hereinafter simply referred to as the "control method"), will be described.

[0084] The control method according to this embodiment is executed by a control system 1, which mainly consists of a computer system; in other words, it is implemented by a control program for work vehicles (hereinafter simply referred to as the "control program"). That is, the control program according to this embodiment is a computer program that causes one or more processors to execute each process related to the control method.

[0085] Here, the control system 1 executes the following various processes related to the control method when a specific pre-set start operation is performed to run the control program. The start operation is, for example, turning on the key switch to start the engine (power source 18), and / or starting the application program (control program for the work vehicle) on the terminal device 3. On the other hand, the control system 1 terminates the following various processes related to the control method when a specific pre-set end operation is performed. The end operation is, for example, turning off the key switch, and / or terminating the application program (control program for the work vehicle) on the terminal device 3.

[0086] [5.1] Automated driving method First, a method for automatically driving (including autonomous and semi-autonomous driving) the work vehicle 10 using the control system 1 according to this embodiment will be explained with reference to Figure 5. Figure 5 schematically shows the target path R1 and the work vehicle 10 generated for the target area F1 in a plan view. In Figure 5, the path along which the work vehicle 10 performs work (work path r11) is shown as a solid line, and the path along which the work vehicle 10 does not perform work (non-work path r12) is shown as a dotted line.

[0087] The left side of Figure 5 shows an example of autonomous driving in which the work vehicle 10 moves autonomously without operator intervention. In autonomous driving, the control system 1 automatically drives the work vehicle 10 along a target path R1 generated for a target area F1 consisting of a field. In the example in Figure 5, the target path R1 includes a plurality of straight work paths r11 and a non-work path r12 consisting of a turning path connecting adjacent work paths r11. In this case, the control system 1 controls the travel device 13, steering device 14, and power source 18 with the travel control unit 21 and steering control unit 22 to drive the work vehicle 10 along the target path R1. Furthermore, the control system 1 controls the implement 12 with the work control unit 23, and the implement 12 performs work only on the work path r11 of the target path R1.

[0088] In this example, when the work vehicle 10 travels along a non-work path r12 which consists of at least a turning path, the steering control unit 22 controls the steering device 14 to change the steering angle θ1 of the steering wheels 111 in order to make the work vehicle 10 turn along the non-work path r12.

[0089] The right side of Figure 5 shows an example of straight-line assist (semi-automatic driving) where only steering is automated. In straight-line assist, the control system 1 drives the work vehicle 10 along a target path R1 consisting of a straight path r13 parallel to a reference line in a target area F1 consisting of a field. In this case, the control system 1 controls the steering device 14 with the steering control unit 22 to maintain it on the straight path r13.

[0090] In this example, if the work vehicle 10 deviates from the straight path r13, the steering control unit 22 controls the steering device 14 to change the steering angle θ1 of the steering wheels 111 in order to return the work vehicle 10 to the straight path r13.

[0091] [5.2] Steering Angle Determination Process Next, the processes related to the steering angle determination process in the control method according to this embodiment will be described with reference to Figures 6 and 7.

[0092] As described above, in automatic steering mode, the steering angle determination processing unit 56 performs a steering angle determination process to determine whether or not the steering wheel is fully turned based on the steering angle determination conditions. In this embodiment, the maximum steering angle to the left and the maximum steering angle to the right are individually adjusted by the stopper mechanism 45, and the steering angle determination process determines the fully turned state to the left (referred to as the "left fully turned state") and the fully turned state to the right (referred to as the "right fully turned state").

[0093] In this embodiment, as an example, the steering angle determination conditions include a first requirement, a second requirement, a third requirement, a fourth requirement, and a fifth requirement, and the steering angle determination processing unit 56 determines that the vehicle is in a fully steered state only if all of these first to fifth requirements are met. In other words, if even one of the first to fifth requirements is not met, the steering angle determination processing unit 56 determines that the vehicle is not in a fully steered state.

[0094] The first requirement is that the absolute value of the steering angle θ1 detected by the steering angle sensor 44 is greater than or equal to a threshold angle. Specifically, the threshold angle in the first requirement is the angle at which the stopper mechanism 45 can act, and is, for example, "25 degrees". The second requirement is that the steering angle θ1 has hardly changed for a predetermined time. Specifically, the second requirement is that the amount of change in the output of the steering angle sensor 44 acquired by the acquisition processing unit 51 is less than or equal to a certain angle (for example, 0.5 degrees) at a predetermined number of sampling timings (timing of acquiring the steering angle signal).

[0095] The third requirement is that the motor 421 is generating a torque equal to or greater than a predetermined value. Specifically, the predetermined value in the third requirement is a torque value that does not occur in typical automatic steering, and is, for example, "8 Nm". The fourth requirement is that the direction of the torque generated in the motor 421 matches the command value. Specifically, the fourth requirement is that the sign (+ / -) of the torque generated in the motor 421 matches the forward / reverse rotation of the motor 421 in the command value (speed command value, etc.).

[0096] The fifth requirement is that the first, second, third, and fourth requirements are met for a certain period of time. The certain angle in the fifth requirement is, for example, "0.1 seconds". In short, the steering angle determination processing unit 56 determines that the steering is in a fully steered state when the state in which all of the above first to fourth requirements are met continues for a certain period of time (fifth requirement).

[0097] Figure 6 is a flowchart showing an example of the process related to the steering angle determination process. The control method according to this embodiment performs the process shown in Figure 6 each time the automatic steering mode is started.

[0098] In other words, when automatic driving (including autonomous driving and semi-automatic driving) is started, the mode switching processing unit 52 switches the operating mode from manual steering mode to automatic steering mode. When automatic steering mode is started, the automatic steering processing unit 53 starts the automatic steering process (S1). Then, the maximum angle setting processing unit 57 resets the set (stored in the memory unit 24) maximum steering angle (S2).

[0099] In the next step S3, the steering angle determination processing unit 56 determines whether the maximum left steering angle (referred to as the "maximum left steering angle") has been set. If the maximum left steering angle is stored in the maximum left steering angle storage area 241, the steering angle determination processing unit 56 determines that the maximum left steering angle has been set (S3: Yes), skips the processing related to determining the leftmost steering state (S4~S6), and proceeds to step S7. On the other hand, if the maximum left steering angle is not stored in the maximum left steering angle storage area 241, the steering angle determination processing unit 56 determines that the maximum left steering angle has not been set (S3: No), and proceeds to step S4.

[0100] In step S4, the steering angle determination processing unit 56 determines whether or not the vehicle is in a left-turn-to-left state based on the steering angle determination conditions. Here, when determining the left-turn-to-left state, the determination is limited to a negative steering angle θ1 in, for example, the first requirement of the steering angle determination conditions. That is, the predetermined angle in the first requirement is set to "-25 degrees", and the first requirement is satisfied when the steering angle θ1 is "-25 degrees" or less. If the steering angle determination conditions are met at this time, the steering angle determination processing unit 56 determines that the vehicle is in a left-turn-to-left state (S4: Yes), and proceeds to step S5. If the steering angle determination conditions are not met, the steering angle determination processing unit 56 determines that the vehicle is not in a left-turn-to-left state (S4: No), and proceeds to step S7.

[0101] In step S5, the automatic steering processing unit 53 executes a process to limit the torque of the motor 421 over the limiting period. Specifically, while the automatic steering processing unit 53 basically controls the speed of the motor 421 by the speed command value, during the limiting period it drives the motor 421 by current control with a current command value of "0A". The limiting period is a fixed time period (for example, 0.006 seconds) immediately after it is determined that the vehicle is in a left-hand-off state. As a result, for a fixed time immediately after it is determined that the vehicle is in a left-hand-off state, the motor 421 is driven by current control with a current command value of "0A", thus limiting the torque generated in the motor 421.

[0102] In the next step S6, the maximum angle setting processing unit 57 sets the maximum left steering angle based on the steering angle θ1 detected by the steering angle sensor 44 in step S4. In other words, the maximum angle setting processing unit 57 determines the maximum left steering angle based on the steering angle θ1 of the steering wheel 111 when it is determined that the steering wheel is turned all the way to the left, and sets the maximum left steering angle by storing it in the maximum left angle storage area 241 of the storage unit 24.

[0103] In the next step S7, the steering angle determination processing unit 56 determines whether the maximum steering angle to the right (referred to as the "maximum right steering angle") has been set. If the maximum right steering angle is stored in the maximum right steering angle storage area 242, the steering angle determination processing unit 56 determines that the maximum right steering angle has been set (S7: Yes), skips the processing related to determining the state of turning the steering wheel to the right (S8~S10), and proceeds to step S11. On the other hand, if the maximum right steering angle is not stored in the maximum right steering angle storage area 242, the steering angle determination processing unit 56 determines that the maximum right steering angle has not been set (S7: No), and proceeds to step S8.

[0104] In steps S8 to S10, the same processing performed in steps S4 to S6 for "left-hand steering state" and "maximum left steering angle" is performed for "right-hand steering state" and "maximum right steering angle". That is, for example, in step S8, the predetermined angle in the first requirement is set to "25 degrees", and the first requirement is satisfied when the steering angle θ1 is "25 degrees" or more. At this time, if the steering angle determination condition is met, the steering angle determination processing unit 56 determines that the vehicle is in the right-hand steering state (S8: Yes), and proceeds to step S9. If the steering angle determination condition is not met, the steering angle determination processing unit 56 determines that the vehicle is not in the right-hand steering state (S8: No), and proceeds to step S11.

[0105] In step S11, the steering angle determination processing unit 56 determines whether both the maximum left steering angle and the maximum right steering angle have been set. That is, if the maximum left steering angle is stored in the maximum left steering angle storage area 241 (S3: Yes) and the maximum right steering angle is stored in the maximum right steering angle storage area 242 (S7: Yes), the steering angle determination processing unit 56 determines that the maximum steering angle has been set (S11: Yes) and terminates the series of processes related to the steering angle determination process. On the other hand, if either the maximum left steering angle or the maximum right steering angle has not been set (S11: No), the steering angle determination processing unit 56 returns to step S3.

[0106] The control system 1 executes the processes in steps S1 to S11 above each time the automatic steering mode is started. However, the flowchart shown in Figure 6 is merely an example, and processes may be added or omitted as appropriate, or the order of processes may be changed as appropriate.

[0107] As described above, the control method according to this embodiment includes, in the automatic steering mode, executing a steering angle determination process to determine whether the steering wheel 111 is in a fully steered state, where it is steered to its maximum steering angle, based on a steering angle determination condition. Therefore, for example, if it is determined that the steering wheel is in a fully steered state, the automatic steering process is prevented from increasing the steering angle θ1 further, thereby suppressing the steering wheel 111 from being automatically steered beyond its fully steered state. Thus, it is less likely that problems will occur, such as excessive torque being generated in the motor 421 due to the steering wheel being automatically steered beyond its fully steered state, resulting in an override condition being determined and automatic steering being canceled. Furthermore, since there is no need to set a large torque threshold for determining an override condition in order to avoid such problems, it is also possible to eliminate problems such as the motor 421 being damaged due to prolonged situations of excessive torque being generated in it, or the need for a relatively large force to operate the steering wheel 41 to switch to manual steering.

[0108] Here, the steering angle determination conditions include torque conditions (third and fourth requirements) related to the torque of the motor 421. Therefore, compared to, for example, determining whether the steering wheel 111 is fully turned based only on the first and second requirements related to the steering angle θ1, it becomes less likely to make a false determination that the steering wheel 111 is fully turned.

[0109] Furthermore, the steering angle determination condition includes a rate of change condition (second requirement) relating to the rate of change of the steering angle θ1 of the steering wheel 111. Therefore, compared to, for example, determining whether the steering wheel 111 is fully turned based only on the third and fourth requirements relating to the torque of the motor 421, it becomes less likely to make a false determination that the steering wheel 111 is fully turned.

[0110] Furthermore, the steering angle determination condition includes the requirement that the absolute value of the steering angle θ1 of the steering wheel 111 is greater than or equal to a threshold angle (first requirement). Therefore, compared to, for example, determining whether the steering wheel 111 is fully turned based solely on the second requirement concerning the rate of change of the steering angle θ1, it becomes less likely that a misjudgment will occur that the steering wheel 111 is fully turned.

[0111] Furthermore, the steering angle determination process ends when the maximum steering angle is set (step S11). In particular, in this embodiment, the maximum steering angle is set individually for each steering direction (left and right) of the steering wheel 111, so the steering angle determination condition ends when both maximum steering angles (left maximum steering angle and right maximum steering angle) are set. As a result, the steering angle determination process is not performed after the maximum steering angle is set, thus reducing the processing load related to the steering angle determination process.

[0112] Furthermore, the steering angle determination process is executed each time the automatic steering mode is started. Therefore, for example, even if the maximum steering angle is set and the steering angle determination process is completed, if the automatic steering mode is terminated and then restarted, the steering angle determination process will be executed again. As a result, even if a person readjusts the stopper mechanism 45 after the automatic driving has ended, the steering angle determination process will be performed again for the next automatic driving session.

[0113] Furthermore, in the control method according to this embodiment, as in steps S5 and S9, if it is determined that the steering angle is at its limit, the torque of the motor 421 is limited during the limit period. That is, as illustrated in Figure 7, if it is determined that the steering angle is at its limit at time t1 by the steering angle determination process, the torque of the motor 421 will be limited during the limit period T1 immediately following. Figure 7 is a graph with the horizontal axis representing time and showing the change in the torque of the motor 421. In Figure 7, the dashed line shows a comparative example where no limit period T1 is provided and speed control is continued even after it is determined that the steering angle is at its limit.

[0114] In short, in the comparative example, after it is determined that the steering wheel is fully turned, the motor 421 is controlled to return the steering wheel 111 to the maximum steering angle. However, due to speed control, there is a large discrepancy between the measured rotational speed (velocity) of the motor 421 and the commanded value, and it takes time for the torque of the motor 421 to decrease. As a result, even after it is determined that the steering wheel is fully turned, a large torque is applied to the motor 421 for a relatively long time, which can lead to problems such as an override condition being incorrectly determined or an overload being placed on the motor 421, etc.

[0115] In contrast, in this embodiment, the automatic steering processing unit 53 basically controls the speed of the motor 421 by the speed command value, but during the limiting period T1 from time t2 to time t3 immediately following time t1, it switches to current control with a current command value of "0A". As a result, the torque of the motor 421 drops sharply from time t2, which is the starting point of the limiting period T1. Therefore, the time required for the torque of the motor 421 to fall below a certain value X1 can be shortened compared to the comparative example. Consequently, the time during which a large torque is applied to the motor 421 after it is determined to be in a fully steered state is shortened, thereby solving the problem of being mistakenly determined to be in an override state or of being overloaded by the motor 421, etc.

[0116] In this embodiment, the maximum steering angle in automatic steering is set to the value obtained by subtracting a margin from the steering angle θ1 of the steering wheel 111 when it is determined by the steering angle determination process to be in a fully turned state. In other words, in step S6, which sets the maximum left steering angle, the maximum angle setting processing unit 57 determines the maximum left steering angle as the value obtained by subtracting a predetermined margin from the steering angle θ1 detected by the steering angle sensor 44 at step S4. As an example, the margin is "0.5 degrees". For example, if the steering angle θ1 of the steering wheel 111 when it is determined to be in a fully turned left state is "-51 degrees", then the maximum left steering angle will be "-50.5 degrees", which is obtained by subtracting the margin from that value.

[0117] Similarly, in step S10, which sets the maximum right steering angle, the maximum angle setting processing unit 57 calculates the maximum right steering angle by subtracting a predetermined margin from the steering angle θ1 detected by the steering angle sensor 44 in step S8. For example, if the steering angle θ1 of the steering wheel 111 when it is determined to be in a fully right-turned state is "55 degrees", then the maximum right steering angle will be "54.5 degrees", which is obtained by subtracting the margin from that value.

[0118] In this way, by setting the maximum steering angle to a value obtained by subtracting a margin, it is possible to avoid steering the steering wheel 111 to the maximum steering angle by automatic steering. This prevents the stopper mechanism 45 from acting and generating excessive torque on the motor 421 in automatic steering mode, prevents the stopper mechanism 45 from mistakenly determining an override state, and keeps the load on the motor 421 and other components small.

[0119] However, such a margin is not mandatory. For example, the steering angle θ1 of the steering wheel 111 when it is determined to be in the fully turned state by the steering angle determination process may be taken as the maximum steering angle. In this case, when the steering angle θ1 is controlled to be near the maximum steering angle (for example, within 5 degrees) by the automatic steering process, it is preferable to limit the driving torque of the motor 421. This prevents the stopper mechanism 45 from acting and generating excessive torque on the motor 421 in automatic steering mode, prevents the stopper mechanism 45 from incorrectly determining an override state, and keeps the load on the motor 421 and other components small.

[0120] [5.3] Override Determination Process Next, the processes related to the override determination process in the control method according to this embodiment will be described with reference to Figures 8 to 15.

[0121] As described above, the override determination processing unit 54 performs an override determination process in automatic steering mode to determine whether or not an override state is in place based on the determination conditions. Here, the determination conditions are set to conditions related to the torque generated in the motor 421.

[0122] In this embodiment, the determination conditions include a plurality of individual conditions relating to the magnitude relationship of torque with respect to different thresholds, such as a first individual condition and a second individual condition. The override determination processing unit 54 determines that an override state exists if at least one of these plurality of individual conditions is met. In other words, the override determination processing unit 54 determines that an override state exists if at least one individual condition is met, and determines that an override state does not exist only if all of the plurality of individual conditions are not met.

[0123] As illustrated in Figure 8, we assume a case where the judgment conditions include a first individual condition that the torque of motor 421 is equal to or greater than the first threshold Th1, a second individual condition that the torque of motor 421 is equal to or greater than the second threshold Th2 (>Th1), and a third individual condition that the torque of motor 421 is equal to or greater than the third threshold Th3 (>Th2). Here, the first individual condition is that the state in which the torque is equal to or greater than the first threshold Th1 continues for one hour, the second individual condition is that the state in which the torque is equal to or greater than the second threshold Th2 continues for two hours (<first hour), and the third individual condition is that the state in which the torque is equal to or greater than the third threshold Th3 continues for three hours (<second hour). Figure 8 is a graph with the horizontal axis representing time, showing the change in the torque of motor 421.

[0124] In the example shown in Figure 8, the period T11 during which the torque of motor 421 is equal to or greater than the first threshold Th1 is less than 1 hour, while the period T12 during which the torque of motor 421 is equal to or greater than the second threshold Th2 is 2 hours or longer. In other words, although the first and third individual conditions are not met, the second individual condition is met, so the override determination processing unit 54 determines that the determination conditions are met and determines that the system is in an override state.

[0125] In this way, the override determination processing unit 54 can determine an override state if even one of several individual conditions is met, enabling the determination of a variety of override states. As a result, this leads to an improvement in the accuracy of override state determination.

[0126] Furthermore, the judgment criteria include time-related conditions. In short, the judgment criteria include time-related conditions, such as requiring not only the magnitude of the motor 421's torque, but also that the state in which the motor 421's torque is above a threshold for a certain period of time. Therefore, for example, in situations where an external force is applied to the steering wheel 111 for only a moment, such as when the steering wheel 111 goes over a step, even if the torque of the motor 421 increases for only a moment, it becomes less likely to be mistakenly determined to be an override state. As a result, this leads to an improvement in the accuracy of determining the override state.

[0127] By the way, in this embodiment, as described above, the "determination condition" used to determine the override state is not fixed, but can be changed by the condition change processing unit 55. In this embodiment, since the determination condition includes multiple individual conditions, the condition change processing unit 55 will change at least one of these multiple individual conditions.

[0128] Specifically, the determination conditions are changed according to the command values ​​used to control the motor 421. These command values ​​include speed command values, current command values, torque command values, and position command values. In this embodiment, as an example, the determination conditions are changed according to the speed command value related to the rotational speed of the motor 421.

[0129] For example, as illustrated in Figure 9, the threshold value in the judgment condition (here, the first threshold Th1) is not constant but changes according to the speed command value. Figure 9 is a graph showing the relationship between the (speed) command value and the threshold value, with the horizontal axis representing the speed command value and the vertical axis representing torque. In other words, in the example in Figure 9, the first threshold value Th1 used in the first individual condition, which is one of the first, second, and third individual conditions included in the judgment condition, is proportional to the speed command value that defines the rotational speed of the motor 421. That is, the larger the (speed) command value, the larger the threshold value for torque (first threshold Th1), and the stricter the judgment condition (first individual condition). Furthermore, in the example in Figure 9, a fourth threshold value Th4, which is proportional to the speed command value, is also set only in the intermediate region of the speed command value. In other words, the judgment condition includes a fourth individual condition that the torque remains above the fourth threshold value Th4 for four hours. The fourth threshold value Th4 is a constant value in the regions above and below the intermediate region of the speed command value.

[0130] When using the threshold shown in Figure 9, the first threshold Th1 changes as the speed command value changes, as illustrated in Figure 10. Figure 10 is a graph with the horizontal axis representing time, showing the change in torque of motor 421 in the upper section and the change in speed command value in the lower section.

[0131] In the example shown in Figure 10, the period T11 during which the torque of motor 421 is equal to or greater than the first threshold Th1 is 1 hour or longer. In other words, the first individual condition is met, so the override determination processing unit 54 determines that the determination condition is met and determines that the system is in an override state.

[0132] In this way, the judgment conditions are changed according to the command value for controlling the motor 421, so that, for example, the judgment conditions can be made stricter as the speed command value increases. Therefore, as an example, when turning the work vehicle 90 degrees along a turning path during automatic steering, even if excessive torque is generated in the motor 421 due to sudden steering, it becomes less likely to be determined as an override state. Conversely, in situations where sudden steering of the steering wheels 111 is unlikely to occur, such as during straight-line assist, it is more likely to be determined as an override state, so the force required for the operator to operate the steering wheel 41 to switch to manual steering becomes relatively small, improving operability.

[0133] Incidentally, in this embodiment, the determination condition is also changed by the steering angle θ1 of the steering wheel 111. However, with respect to the steering angle θ1, instead of continuously changing the determination condition, for example, as shown in Figure 11, the angular range of the steering angle θ1 is divided into multiple sub-regions A1, A2, and A3, and the determination condition to be applied to each sub-region A1, A2, and A3 is determined.

[0134] In Figure 11, as an example, the steering angle θ1 is defined as follows: sub-region A1 is the range greater than "-25 degrees" and less than "25 degrees"; sub-region A2 is the range greater than "-60 degrees" and greater than "-25 degrees"; and sub-region A3 is the range greater than "25 degrees" and less than or equal to "60 degrees". A "first determination condition" is assigned to sub-region A1, and a "second determination condition" is assigned to sub-regions A2 and A3. In other words, if the current steering angle θ1 of the steering wheel 111 is in sub-region A1 (-25° < θ1 < 25°), the override determination processing unit 54 uses the first determination condition to determine whether or not an override is occurring. On the other hand, if the current steering angle θ1 of the steering wheel 111 is in small region A2 or small region A3 (-60°≦θ1≦-25°, or 25°≦θ1≦60°), the override determination processing unit 54 uses the second determination condition to determine whether or not an override state is present.

[0135] Here, the first determination condition is less stringent than the second determination condition, meaning it is easier to determine that an override state has occurred. Specifically, as shown in Figure 11, the first determination condition includes the first to fourth individual conditions using the first to fourth thresholds Th1 to Th4, similar to those in Figure 10. On the other hand, the second determination condition includes the fifth individual condition using the fifth threshold Th5, and the sixth individual condition using the sixth threshold Th6. The fifth individual condition is that the torque remains at or above the fifth threshold Th5 for five hours, and the sixth individual condition is that the torque remains at or above the sixth threshold Th6 for six hours (<5 hours). The fifth threshold Th5 and the sixth threshold Th6 are constant regardless of the speed command value.

[0136] Furthermore, the first judgment condition has a relatively smaller torque threshold and / or a shorter judgment time compared to the second judgment condition. In other words, the thresholds for the first judgment condition (1st threshold Th1 to 4th threshold Th4) are set smaller than the thresholds for the second judgment condition (5th threshold Th5 and 6th threshold Th6). Alternatively, the judgment time for the first judgment condition (1st to 4th time) is set shorter than the thresholds for the second judgment condition (5th and 6th time).

[0137] Therefore, when the steering angle θ1 is in small region A1, the determination conditions become more lenient compared to when the steering angle θ1 is in small region A2 or small region A3, making it easier for the override determination processing unit 54 to determine that an override state has occurred.

[0138] As explained above, in this embodiment, when the angular range of the steering angle θ1 of the steering wheel 111 is divided into multiple sub-regions A1, A2, and A3, the determination condition is changed depending on which of the sub-regions A1, A2, and A3 the steering angle θ1 is in. Therefore, it is possible to apply an appropriate determination condition according to the steering angle θ1, thereby improving the accuracy of determining the override state.

[0139] In this embodiment, a relatively strict judgment condition (second judgment condition) is assigned to the small regions A2 and A3, which include the maximum steering angle, making it less likely for the system to misidentify the override state due to the fully turned steering position. On the other hand, a relatively lenient judgment condition (first judgment condition) is assigned to the small region A1, so the force required for the operator to operate the steering wheel 41 to switch to manual steering is relatively small, improving operability.

[0140] Furthermore, the assignment of judgment conditions to each sub-region A1, A2, and A3 as described above is not fixed, but is changed, for example, according to the judgment result of the steering angle determination process. In this embodiment in particular, since the left-end-off state and the right-end-off state are determined separately, the assignment of judgment conditions to each sub-region A1, A2, and A3 is changed in the case where it is determined to be in the left-end-off state and in the case where it is determined to be in the right-end-off state.

[0141] For example, if it is determined that the vehicle is in a state of right-hand steering, the assignment of judgment conditions to each sub-region A1, A2, and A3 changes from the state shown in Figure 11 to the state shown in Figure 12. That is, after it is determined that the vehicle is in a state of right-hand steering, the maximum steering angle to the right is set, so the vehicle will not be steered to the right-hand steering state in automatic steering mode. Therefore, as shown in Figure 12, the judgment condition assigned to sub-region A3, which includes the maximum steering angle to the right, is switched from the "second judgment condition" to the same "first judgment condition" as sub-region A1. Similarly, if it is determined that the vehicle is in a state of left-hand steering, the judgment condition assigned to sub-region A2, which includes the maximum steering angle to the left, is switched from the "second judgment condition" to the same "first judgment condition" as sub-region A1.

[0142] Thus, in this embodiment, the determination conditions are changed according to the determination result of the steering angle determination process. Therefore, for example, if the steering is not performed to the maximum steering angle in automatic steering mode after it has been determined that the steering is at its limit, the determination conditions for the small regions A2 and A3, which include the maximum steering angle, are loosened, making it easier to determine that the steering is in an override state. As a result, the force required for the operator to operate the steering wheel 41 to switch to manual steering becomes relatively small, improving operability.

[0143] The control method according to this embodiment executes the steering angle determination process and the override determination process in parallel. Therefore, the steering angle determination process and the override determination process do not interfere with each other, and the full steering state and the override state are determined individually. However, as described above, only the determination result of the steering angle determination process is used to change the determination conditions of the override determination process.

[0144] Furthermore, in this embodiment, the determination conditions are changed with a delay of a certain amount of time from the moment the steering wheel 111 is determined to be steered to its maximum steering angle by the steering angle determination process. That is, the process of changing the assignment of the determination conditions to the small regions A1, A2, and A3 as a result of the determination that the steering wheel is in the fully steered state described above is executed with a delay of a certain amount of time from the moment the fully steered state is determined. The delay time is, for example, "0.1 sec".

[0145] This configuration provides a delay time between the detection of a fully cut-off state and the change in the detection criteria. Therefore, for example, in a fully cut-off state where excessive torque is generated in motor 421, the detection criteria are relaxed before the torque drops completely, making it easier to avoid being mistakenly detected as being in an override state.

[0146] Figure 13 is a flowchart showing an example of the process related to override determination. The control method according to this embodiment performs the process shown in Figure 13 each time the automatic steering mode is started.

[0147] In other words, when automatic driving (including autonomous driving and semi-automatic driving) is started, the mode switching processing unit 52 switches the operating mode from manual steering mode to automatic steering mode. When automatic steering mode is started, the automatic steering processing unit 53 starts the automatic steering process (S21). Then, the condition change processing unit 55 changes the judgment conditions used in the override judgment process (S22). At this time, the condition change processing unit 55 changes the judgment conditions based on the command value (speed command value) for controlling the motor 421, the steering angle θ1 of the steering wheel 111, and the judgment result of the steering angle judgment process.

[0148] In the next step, S23, the override determination processing unit 54 determines whether or not the system is in an override state. At this time, if even one of the multiple individual conditions included in the determination condition is met, the override determination processing unit 54 determines that the system is in an override state (S23: Yes) and proceeds to step S24. On the other hand, if none of the individual conditions are met, the override determination processing unit 54 determines that the system is not in an override state (S23: No) and returns to step S22.

[0149] In step S24, the driving control unit 21 slows down or stops the work vehicle 10. If only the work vehicle 10 is slowed down, the work vehicle 10 will continue to move. In the next step S25, the mode switching processing unit 52 switches the operating mode from automatic steering mode to manual steering mode. As a result, the automatic steering processing unit 53 terminates the automatic steering process (S26), and the series of processes ends.

[0150] The control system 1 executes the processes in steps S21 to S26 above each time the automatic steering mode is started. However, the flowchart shown in Figure 13 is merely an example, and processes may be added or omitted as appropriate, or the order of processes may be changed as appropriate.

[0151] As described above, the control method according to this embodiment includes executing an override determination process in automatic steering mode to determine whether or not an override state is in place based on determination conditions relating to the torque generated in the motor 421. Here, the control method further includes changing the determination conditions. Therefore, it is possible to determine the override state using appropriate determination conditions at any given time, enabling appropriate determination of the override state. As a result, for example, when turning a work vehicle 90 degrees along a turning path during automatic steering, it is easier to avoid a problem in which excessive torque is generated in the motor of the power steering mechanism due to sudden steering, resulting in an override state being determined and automatic steering being canceled. Furthermore, since it is not necessary to constantly set a high torque threshold for determining an override state in order to avoid the aforementioned problem, it is also possible to eliminate problems such as damage to the motor 421 due to prolonged situations where excessive torque is generated in the motor 421, or the need for relatively large force to operate the steering handle 41 to switch to manual steering.

[0152] Furthermore, the control method according to this embodiment further includes, when it is determined that an override state is in place, switching the operating mode of the work vehicle 10 from automatic steering mode to manual steering mode in which the operator manually steers the vehicle (S25). Therefore, when an override state is determined, the steering of the steering wheels 111 can be automatically handed over to the operator, improving operability for the operator.

[0153] Furthermore, the control method according to this embodiment further includes (S24) decelerating or stopping the travel speed of the work vehicle 10 when it is determined that an override state is occurring. Therefore, after an override state is determined, for example, an operator can check the situation around the work vehicle 10 and then accelerate or start the work vehicle 10.

[0154] Incidentally, the above-mentioned modification of the judgment conditions is merely one example, and various other modification methods can be applied. For example, as shown in Figure 14, the angular range of the steering angle θ1 may be divided into more sub-regions A11 to A17, and judgment conditions to be applied to each sub-region A11 to A17 may be determined. This makes it possible to apply more appropriate judgment conditions according to, for example, the characteristics of the work vehicle 10.

[0155] Furthermore, if the steering angle determination process determines that the vehicle is in a fully steered state, as shown in Figure 15, not only can the determination conditions be assigned to the sub-regions A1, A2, and A3, but the sub-region divisions themselves may also be changed. In the example in Figure 15, before it is determined that the vehicle is in a fully steered state, the angle range of the steering angle θ1 is divided into three sub-regions A1, A2, and A3, whereas before it is determined that the vehicle is in a fully steered state, it is divided into six sub-regions A21 to A26. Moreover, the determination conditions assigned to each sub-region may be changed to completely different conditions. This makes it possible to apply more appropriate determination conditions according to, for example, the characteristics of the work vehicle 10.

[0156] Here, it is not mandatory for the determination conditions to be changed based on the command value (speed command value), steering angle θ1, and the determination result of the steering angle determination process; the determination conditions may be changed based on other parameters. For example, in this embodiment, the power steering mechanism 43 is hydraulic, and the amplification factor of the operating force by the power steering mechanism 43 changes according to the engine speed of the power source 18. Therefore, the determination conditions may be changed according to the engine speed. In this case, it is preferable that the determination conditions are relaxed, such as by making the threshold for torque smaller as the engine speed decreases.

[0157] The determination criteria only need to be changed based on at least one of the multiple parameters mentioned above (command value, steering angle θ1, determination result of steering angle determination process, and engine speed, etc.).

[0158] [6] Variant The following lists some modifications of Embodiment 1. The modifications described below can be combined and applied as appropriate.

[0159] The control system 1 in this disclosure includes a computer system. The computer system mainly consists of one or more processors and one or more memories as hardware. The functions of the control system 1 in this disclosure are realized when the processor executes a program (a control program for work vehicles) recorded in the memory of the computer system. The program may be pre-recorded in the memory of the computer system, provided via a telecommunications line, or provided on a non-temporary recording medium such as a memory card, optical disk, or hard disk drive that can be read by the computer system. Furthermore, some or all of the functional parts included in the control system 1 may be composed of electronic circuits.

[0160] Furthermore, it is not essential for control system 1 to have at least some of its functions integrated into a single enclosure; the components of control system 1 may be distributed across multiple devices (e.g., control device 2 and terminal device 3). Conversely, functions that are distributed across multiple devices in Embodiment 1 may be integrated into a single enclosure. Moreover, at least some of the functions of control system 1 may be implemented by the cloud (cloud computing) or the like.

[0161] Furthermore, the terminal device 3 is not limited to general-purpose terminals such as tablet terminals, smartphones, or laptop computers, but may also consist of dedicated terminals. Moreover, multiple terminal devices 3 may be associated with one work vehicle 10, in which case multiple terminal devices 3 can control one work vehicle 10. Conversely, one terminal device 3 may be associated with multiple work vehicles 10, in which case one terminal device 3 can control multiple work vehicles 10.

[0162] Furthermore, in Embodiment 1, the steering wheels 111 are a pair of left and right front wheels, but are not limited to this. For example, a pair of left and right rear wheels may constitute the steering wheels in addition to or instead of the pair of left and right front wheels. In this case, the rear wheels, as steering wheels, will also be steered by the steering device 14. Also, the drive wheels 112 are not limited to a pair of left and right rear wheels; for example, a pair of left and right front wheels may constitute the drive wheels in addition to or instead of the pair of left and right rear wheels. Moreover, the steering wheels 111 may consist of only one wheel or three or more wheels. Similarly, the drive wheels 112 may consist of only one wheel or three or more wheels. The same wheel may be used for both the steering wheels 111 and the drive wheels 112.

[0163] Furthermore, in Embodiment 1, the steering angles θ1 of the left front wheel and the right front wheel, which are a pair of steering wheels 111, are the same. However, the steering angles of the left front wheel and the right front wheel may be different, not limited to this example. In this case, for example, the average value of the steering angles of the left front wheel and the right front wheel becomes the steering angle θ1 of the pair of steering wheels 111.

[0164] Furthermore, the power steering mechanism 43 is not limited to a hydraulic type, but may also be electric, for example. In an electric power steering mechanism 43, the motor 421 of the steering operation unit 42 may be used for this purpose, and the steering wheels 111 may be directly steered by the output of the motor 421. In this case, it is preferable that the determination condition is not changed depending on the engine speed.

[0165] Furthermore, it is not necessary for the maximum steering angle to be reset each time the auto-steering mode is activated; the maximum steering angle that has been set may be used again in the next auto-steering mode.

[0166] (Embodiment 2) The control method for the work vehicle 10 according to this embodiment differs from that of Embodiment 1 in that the parameters for changing the determination conditions used in the override determination process are different. Hereinafter, components similar to those in Embodiment 1 will be denoted by common reference numerals and their descriptions will be omitted as appropriate.

[0167] In this embodiment, the determination condition is changed according to at least one of the pitch angle α1 and the roll angle of the work vehicle 10. That is, as shown in Figure 16, the determination condition is changed according to at least one of the pitch angle α1, which is the rotation (tilt) of the machine body 11 of the work vehicle 10 around a first axis Ax1 that passes through the center of the machine body 11 and extends in the left-right direction D3, and the roll angle, which is the rotation (tilt) of the machine body 11 around a second axis Ax2 that passes through the center of the machine body 11 and extends in the front-rear direction D2.

[0168] Here, as an example, we will assume that the judgment conditions are changed only according to the pitch angle α1, of the two roll angles. Specifically, as illustrated in Figure 16, the more the aircraft 11 tilts forward and the larger the pitch angle α1 becomes, the larger the torque threshold (first threshold Th1) becomes, and the stricter the judgment conditions (first individual conditions) become. That is, if the front wheels are the steering wheels 111, when the load is concentrated at the front of the aircraft 11, the force required to operate the steering wheel 41 increases, and the steering wheel 41 (feel) becomes heavier. Therefore, the larger the pitch angle α1 is in the forward-tilted position of the aircraft 11, the greater the torque generated in the motor 421 of the steering device 14 during automatic steering.

[0169] By changing the judgment criteria according to the pitch angle α1, such that the judgment criteria become stricter as the pitch angle α1 increases, it becomes less likely that an override state will be mistakenly determined even if the torque generated in the motor 421 increases due to such load unevenness. Similarly, when the judgment criteria are changed according to the roll angle, it is preferable that the judgment criteria be changed so that the judgment criteria become stricter as the roll angle increases.

[0170] Furthermore, the judgment conditions may be changed according to the working status of the work vehicle 10. For example, when the work vehicle 10 is traveling in a working state where the work implement 12 is performing work, the load on the steering wheels 111 is greater than when it is traveling in a non-working state where the work implement 12 is not performing work. For this reason, for example, when automatic steering is performed, it is preferable that the judgment conditions be changed depending on whether the work vehicle 10 is in a working state or a non-working state, so that the judgment conditions are more lenient when the work vehicle 10 is in a non-working state compared to when the work vehicle 10 is in a working state. This makes it less likely that an override state will be mistakenly determined even if the torque generated in the motor 421 increases due to a change in the working status of the work vehicle 10.

[0171] As a modification of Embodiment 2, the determination conditions may be changed based on any one or more parameters among the pitch angle α1, roll angle, and working conditions of the work vehicle 10. The configuration of Embodiment 2 (including modifications) can be used in appropriate combination with the various configurations (including modifications) described in Embodiment 1.

[0172] [Notes on the invention] The following is an overview of the invention extracted from the above-described embodiments. Note that each configuration and processing function described below can be selected and combined as desired.

[0173] <Note 1> A control method for a work vehicle having an automatic steering mode that uses a motor to automatically steer the steering wheels, In the aforementioned automatic steering mode, Controlling the aforementioned motor, The determination of whether or not an override state is occurring based on the determination conditions relating to the torque generated in the motor, The determination conditions are changed, A method for controlling work vehicles.

[0174] <Note 2> The aforementioned determination condition is changed according to the command value for controlling the motor. The control method for the work vehicle described in Appendix 1.

[0175] <Note 3> The determination condition is changed according to at least one of the pitch angle and roll angle of the work vehicle. A method for controlling the work vehicle as described in Appendix 1 or 2.

[0176] <Note 4> The aforementioned determination conditions are changed according to the work status of the work vehicle. A control method for the work vehicle described in any of the appendices 1 to 3.

[0177] <Note 5> When the angular range of the steering angle of the steering wheel is divided into multiple sub-regions, the determination condition is changed depending on which of the multiple sub-regions the steering angle falls within. A control method for the work vehicle described in any of the appendices 1 to 4.

[0178] <Note 6> The aforementioned determination conditions include conditions relating to time, A control method for the work vehicle described in any of the appendices 1 to 5.

[0179] <Note 7> The aforementioned determination conditions include a plurality of individual conditions relating to the magnitude relationship of the torque with respect to different thresholds, If any one of the aforementioned individual conditions is met, it is determined that the system is in the override state. A control method for the work vehicle described in any of the appendices 1 to 6.

[0180] <Note 8> If it is determined that the override state is occurring, the operating mode of the work vehicle is switched from the automatic steering mode to a manual steering mode in which the operator manually steers the vehicle. A control method for the work vehicle described in any of the appendices 1 to 7.

[0181] <Note 9> If it is determined that the aforementioned override condition is present, the operation of the work vehicle will be slowed down or stopped. A control method for the work vehicle described in any of the appendices 1 to 8.

[0182] <Note 10> The automatic steering mode further includes performing a steering angle determination process to determine whether or not the steering wheel is steered to its maximum steering angle. A control method for the work vehicle described in any of the appendices 1 to 9.

[0183] <Note 11> The aforementioned determination conditions are changed according to the determination result of the steering angle determination process. A method for controlling a work vehicle as described in any of Appendix 10.

[0184] <Note 12> From the point in time when the steering angle determination process determines that the steering wheel is steered to its maximum steering angle, the determination condition is changed after a delay of a certain amount of time. The control method for the work vehicle described in Appendix 11.

[0185] <Note 13> The control method for the work vehicle described in any of the appendices 1 to 12, A control program for a work vehicle to be executed by one or more processors. [Explanation of Symbols]

[0186] 1. Control system for work vehicles 10 Work Vehicles 11 aircraft 53 Automatic steering processing unit 54 Override Determination Processing Unit 55 Condition Change Processing Unit 100 work systems 111 Steering wheel 421 Motor A1~A3,A11~A17,A21~A26 small area α1 pitch angle θ1 Steering angle

Claims

1. A control method for a work vehicle having an automatic steering mode that uses a motor to automatically steer the steering wheels, In the aforementioned automatic steering mode, Controlling the aforementioned motor, The determination of whether or not an override state is occurring based on the determination conditions relating to the torque generated in the motor, The determination conditions are changed, The determination condition is changed according to at least one of the pitch angle and roll angle of the work vehicle. A method for controlling work vehicles.

2. The aforementioned determination condition is changed according to the command value for controlling the motor. A method for controlling a work vehicle according to claim 1.

3. The aforementioned determination conditions are changed according to the work status of the work vehicle. A method for controlling a work vehicle according to claim 1 or 2.

4. A control method for a work vehicle having an automatic steering mode for automatically steering the steering wheels using a motor, In the aforementioned automatic steering mode, Controlling the aforementioned motor, The determination of whether or not an override state is occurring based on the determination conditions relating to the torque generated in the motor, The determination conditions are changed, When the angular range of the steering angle of the steering wheel is divided into multiple sub-regions, the determination condition is changed depending on which of the multiple sub-regions the steering angle falls within. A method for controlling work vehicles.

5. The aforementioned determination conditions include conditions relating to time, A method for controlling a work vehicle according to claim 1 or 2.

6. A control method for a work vehicle having an automatic steering mode for automatically steering the steering wheels using a motor, In the aforementioned automatic steering mode, Controlling the aforementioned motor, The determination of whether or not an override state is occurring based on the determination conditions relating to the torque generated in the motor, The determination conditions are changed, The aforementioned determination conditions include a plurality of individual conditions relating to the magnitude relationship of the torque with respect to different thresholds, If any one of the aforementioned individual conditions is met, it is determined that the system is in the override state. A method for controlling work vehicles.

7. If it is determined that the override state is occurring, the operating mode of the work vehicle is further switched from the automatic steering mode to a manual steering mode in which the operator manually steers the vehicle. A method for controlling a work vehicle according to claim 1 or 2.

8. A control method for a work vehicle having an automatic steering mode for automatically steering the steering wheels using a motor, In the aforementioned automatic steering mode, Controlling the aforementioned motor, The determination of whether or not an override state is occurring based on the determination conditions relating to the torque generated in the motor, The determination conditions are changed, If it is determined that the aforementioned override condition is present, the operation of the work vehicle will be slowed down or stopped. A method for controlling work vehicles.

9. A control method for a work vehicle having an automatic steering mode for automatically steering the steering wheels using a motor, In the aforementioned automatic steering mode, Controlling the aforementioned motor, The determination of whether or not an override state is occurring based on the determination conditions relating to the torque generated in the motor, The determination conditions are changed, The automatic steering mode further includes performing a steering angle determination process to determine whether or not the steering wheel is steered to its maximum steering angle, The aforementioned determination conditions are changed according to the determination result of the steering angle determination process. A method for controlling work vehicles.

10. From the point in time when the steering angle determination process determines that the steering wheel is steered to its maximum steering angle, the determination condition is changed after a delay of a certain amount of time. A method for controlling a work vehicle according to claim 9.

11. A method for controlling a work vehicle according to claim 1 or 2, A control program for a work vehicle to be executed by one or more processors.

12. Used in work vehicles that have an automatic steering mode that uses a motor to automatically steer the steering wheels, An automatic steering processing unit that controls the motor in the automatic steering mode, An override determination processing unit that determines whether or not an override state is in place based on determination conditions relating to the torque generated in the motor, The system includes a condition change processing unit that changes the aforementioned determination conditions, The determination condition is changed according to at least one of the pitch angle and roll angle of the work vehicle. Control system for work vehicles.

13. A control system for a work vehicle according to claim 12, The above-mentioned work vehicle body comprises, Work system.

Images