Work vehicle and method for controlling work vehicle

Abstract

To enable automatic steering of a work vehicle even immediately after key-on operation of the work vehicle.SOLUTION: A work vehicle capable of performing automatic steering driving is disclosed. The work vehicle includes a positioning system for positioning the work vehicle, and a control device having a non-volatile memory. The control device estimates the orientation of the work vehicle on the basis of the time change in the position measured by the positioning system, performs automatic steering control of the work vehicle on the basis of the position and orientation of the work vehicle and a set target path, stores the orientation of the work vehicle in the non-volatile memory in response to key-off operation of the work vehicle, and starts the automatic steering control using the orientation stored in the non-volatile memory as the initial orientation of the work vehicle after key-on operation of the work vehicle is performed.SELECTED DRAWING: Figure 12

Description

Technical Field

[0001] The present disclosure relates to a work vehicle and a method for controlling the work vehicle.

Background Art

[0002] Research and development for automating work vehicles such as tractors used in fields is underway. For example, work vehicles that travel with automatic steering using a positioning system such as GNSS (Global Navigation Satellite System) capable of precise positioning have been put into practical use. Work vehicles that automatically perform speed control in addition to automatic steering have also been put into practical use.

[0003] Patent Document 1 discloses a work vehicle that can enable autonomous driving control even when the vehicle body is stopped. The work vehicle disclosed in Patent Document 1 includes a vehicle body, a positioning device that measures the self-position of the vehicle body, a control device that executes autonomous driving control, and an autonomous driving changeover switch that switches the autonomous driving control between enabled and disabled. The control device executes autonomous driving control to adjust the steering angle of the vehicle body so that the vehicle body travels along a set azimuth based on the self-position measured by the positioning device. When the vehicle body stops, the control device calculates the azimuth of the vehicle body from the travel locus at least one of a predetermined time before stopping and a predetermined travel distance before stopping, and when the autonomous driving changeover switch is switched to enable autonomous driving control while the vehicle body is stopped, the autonomous driving control is enabled on the condition that the difference between the calculated azimuth of the vehicle body and the set azimuth is within a first predetermined range.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] A work vehicle that travels under automatic steering is required to accurately detect the orientation of the vehicle body. The orientation of the vehicle body can be estimated based on time-series position data obtained from a positioning system such as GNSS, for example.

[0006] However, after the key-on operation of the work vehicle (i.e., the operation of turning on the key switch), until the driver performs an acceleration operation and the vehicle speed becomes high enough (for example, until it reaches 0.45 km / h or more), the orientation of the vehicle body cannot be accurately estimated based on the time-series position data obtained from the positioning system. Therefore, conventionally, it has not been possible to enable automatic steering in the extremely low-speed state immediately after the key-on operation of the work vehicle.

[0007] The present disclosure provides a work vehicle capable of enabling automatic steering even in an extremely low-speed state immediately after a key-on operation, and a control method for the work vehicle.

Means for Solving the Problems

[0008] A work vehicle according to an exemplary embodiment of the present disclosure is a work vehicle capable of automatic steering operation, and includes a positioning system that performs positioning of the work vehicle, and a control device having a non-volatile memory. The control device estimates the orientation of the work vehicle based on the temporal change in the position measured by the positioning system, performs automatic steering control of the work vehicle based on the position and the orientation of the work vehicle and a set target path, stores the orientation of the work vehicle in the non-volatile memory in response to a key-off operation of the work vehicle, and starts the automatic steering control using the orientation stored in the non-volatile memory as the initial orientation of the work vehicle after the key-on operation of the work vehicle is performed.

[0009] The comprehensive or specific aspects of the present disclosure can be implemented by an apparatus, a system, a method, an integrated circuit, a computer program, or a non-transitory computer-readable storage medium, or any combination thereof. The computer-readable storage medium may include a volatile storage medium or a non-volatile storage medium. The apparatus may be composed of a plurality of apparatuses. When the apparatus is composed of two or more apparatuses, the two or more apparatuses may be arranged within one device or may be separately arranged within two or more separate devices.

Advantages of the Invention

[0010] According to an embodiment of the present disclosure, it is possible to activate the automatic steering even in a very low-speed state immediately after the key-on operation.

Brief Description of the Drawings

[0011]

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Mode for Carrying Out the Invention

[0012] Embodiments of the present disclosure will be described below. However, detailed descriptions may be omitted where not necessary. For example, detailed descriptions of well-known matters and redundant descriptions regarding substantially the same configurations may be omitted. This is to avoid making the following description unnecessarily redundant and to facilitate the understanding of those skilled in the art. It should be noted that the inventors provide the accompanying drawings and the following description for those skilled in the art to fully understand the present disclosure, and do not intend to limit the subject matter described in the claims thereby. In the following description, components having the same or similar functions are denoted by the same reference numerals.

[0013] The following embodiments are examples, and the technology of the present disclosure is not limited to the following embodiments. For example, the numerical values, shapes, steps, the order of those steps, the layout of the display screen, etc. shown in the following embodiments are merely examples, and various modifications are possible as long as there is no technical contradiction. Also, as long as there is no technical contradiction, it is possible to combine one aspect with another aspect.

[0014] One example of the "control device" in the present disclosure is a computing device including at least one processor and at least one memory storing a computer program (code) defining a control process executed by the processor. Another example of the "control device" is a computing device including a hardware accelerator such as an FPGA (Field-Programmable Gate Array), an ASSP (Application Specific Standard Product), or an ASIC (Application-Specific Integrated Circuit) configured to execute a control process.

[0015] The "processor" in the present disclosure is a hardware electronic circuit such as a CPU (Central Processing Unit), GPU (Graphics Processing Unit), DSP (Digital Signal Processor), ISP (Image Signal Processor), or NPU (Neural Network Processing Unit). The "memory" is a hardware electronic circuit such as a ROM (Read Only Memory) or RAM (Random Access Memory). A part of the memory may be a storage medium connected to the processor by wiring or a network. These hardware electronic circuits can be implemented by one or more integrated circuits (ICs) or large-scale integrated circuits (LSIs). Each functional unit or block within the electronic circuit, and related components, may be manufactured individually as separate integrated circuit chips, or some or all of these functional units or blocks may be combined and manufactured as a single integrated circuit chip.

[0016] The program that defines the operation of the processor is designed such that the processor executes one or more functions, operations, steps, or processes in the embodiments of the present invention.

[0017] Hereinafter, an embodiment in which the technology of the present disclosure is applied to an agricultural tractor, which is an example of a work vehicle, will be described. The technology of the present disclosure can be applied not only to tractors but also to any work vehicle that travels with automatic steering. The work vehicle may be, for example, a rice transplanter, a combine harvester, a lawn mower, a harvester, a snowplow, or a construction work vehicle.

[0018] (Embodiment) A work vehicle in an exemplary embodiment of the present disclosure, and a method for controlling the operation of the work vehicle will be described.

[0019] The work vehicle in this embodiment includes a positioning system for positioning the work vehicle and a control device for performing control to realize automatic steering operation. The control device includes one or more processors and one or more memories. The one or more memories may include a non-volatile memory that stores a computer program executed by the processor and various data generated in the process of processing by the processor. The control device is not limited to a single computing device and may be an aggregate of a plurality of computing devices.

[0020] The control device can operate in both the automatic steering mode and the manual steering mode. The control device switches between the automatic steering mode and the manual steering mode, for example, in response to an operation by the driver. In the automatic steering mode, the control device controls the steering of the work vehicle so that the work vehicle travels along the target path based on the position and orientation of the work vehicle measured by the positioning system and the target path stored in the memory.

[0021] The positioning system is disposed inside or outside the work vehicle. The positioning system may include, for example, a GNSS unit that performs positioning using RTK (Real Time Kinematic)-GNSS. The GNSS unit identifies the position of the work vehicle based on signals from a plurality of GNSS satellites and outputs time-series position data.

[0022] The target path is a path that is set within the area where the work vehicle travels and serves as the target for travel. The target path is set before starting the automatic steering operation and is stored in a storage device such as a memory. The target path may be set, for example, within a farm field.

[0023] The work vehicle in this embodiment can be, for example, a tractor equipped with a work implement (implement) used for work such as digging up burdock. In the work of digging up burdock, the work vehicle travels at a very low speed (for example, about 0.1 to 0.2 km / h) over a relatively long distance. Therefore, it takes a long time to complete a series of operations. Such long-time-consuming work is labor-saving by utilizing the automatic steering function of the work vehicle. On the other hand, an operator who performs long-time work such as burdock harvesting using the automatic steering function of the work vehicle may take a break during the work (for example, for lunch). For example, the operator may turn off the engine by performing a key-off operation (that is, an operation to turn off the key switch) with the implement stuck in the ground during the work and then take a break. Such an operator restarts the work by turning on the key of the work vehicle again and starting the engine after the break. In order to resume the work with the automatic steering enabled again in such a case, in a conventional work vehicle, it was necessary to once increase the speed to a predetermined reference speed (for example, 0.45 km / h) or more and determine the orientation of the work vehicle based on the time-series position data from the positioning system. This is because in a low-speed range where the moving speed of the work vehicle (hereinafter, also referred to as "vehicle speed") is lower than, for example, 0.45 km / h, even if a high-precision positioning system such as RTK-GNSS is used, it is difficult to accurately estimate the orientation of the work vehicle due to the influence of the fluctuation of the position data.

[0024] However, it is difficult to increase the speed to 0.45 km / h or more with the implement stuck in the ground. Also, even though the operator wants to resume the work in an extremely low-speed range of about 0.1 to 0.2 km / h, if it is necessary to increase the speed to 0.45 km / h or more, the operator will perform unnecessary driving operations, which will reduce convenience. This problem occurs not only when the work vehicle performs burdock harvesting work, but also in any work that needs to be performed in an extremely low-speed range (for example, 0.2 km / h or less).

[0025] In order to solve such a problem, the control device in this embodiment is configured or programmed to execute the following operations. (S1) Estimate the orientation of the work vehicle based on the temporal change in the position measured by the positioning system. (S2) Perform automatic steering control of the work vehicle based on the position and orientation of the work vehicle and the set target path. (S3) In response to the key-off operation of the work vehicle, store the orientation of the work vehicle in the non-volatile memory. (S4) After the key-on operation of the work vehicle is performed, start the automatic steering control with the orientation stored in the non-volatile memory as the initial orientation of the work vehicle.

[0026] By the above steps S3 and S4, after the key-on operation is performed, without increasing the speed up to the reference speed (for example, 0.45 km / h), the automatic steering control can be restarted based on the orientation of the work vehicle at the previous key-off operation. Thereby, for example, even immediately after the key-on operation is performed with the implement stuck in the ground, it becomes possible to start the working travel by automatic steering, and the convenience can be greatly improved.

[0027] Hereinafter, the configuration and operation of the work vehicle of the present embodiment will be described in more detail.

[0028] <Configuration> FIG. 1 is a perspective view showing an example of the appearance of the work vehicle 100 in the present embodiment. FIG. 2 is a side view schematically showing an example of the work vehicle 100 and a work implement (implement) 300 connected to the work vehicle 100. The work vehicle in the present embodiment is a tractor used in a farm field. The technology in the present embodiment can also be applied to work vehicles other than tractors.

[0029] The work vehicle 100 in the present embodiment includes a GNSS unit 120 and one or more obstacle sensors 130. Although one obstacle sensor 130 is illustrated in FIG. 1, the obstacle sensors 130 may be provided at a plurality of locations on the work vehicle 100. Note that the obstacle sensors 130 are provided as needed. If not necessary, the work vehicle 100 may not include the obstacle sensors 130.

[0030] As shown in FIG. 2, the work vehicle 100 includes a vehicle body 101, a prime mover (engine) 102, and a transmission 103. The vehicle body 101 is provided with a wheel 104 with a tire and a cabin 105. The wheel 104 includes a pair of front wheels 104F and a pair of rear wheels 104R. Inside the cabin 105, a driver's seat 107, a steering device 106, a plurality of pedals 109, an operation terminal 200, and a switch group for operation are provided. The switch group includes a key switch 212 (ignition switch) for operating the start and stop of the engine. One or both of the front wheels 104F and the rear wheels 104R may be replaced with a plurality of wheels (crawlers) equipped with endless tracks instead of the wheels with tires.

[0031] The GNSS unit 120 in the present embodiment includes a GNSS receiver. The GNSS receiver may include an antenna that receives signals from GNSS satellites and a processor that determines the position of the work vehicle 100 based on the signals received by the antenna. The GNSS unit 120 receives GNSS signals transmitted from a plurality of GNSS satellites and performs positioning based on the GNSS signals. GNSS is a general term for satellite positioning systems such as GPS (Global Positioning System), QZSS (Quasi-Zenith Satellite System, for example, Michibiki), GLONASS, Galileo, and BeiDou. The GNSS unit 120 in the present embodiment is provided on the upper part of the cabin 105, but may be provided at other positions.

[0032] The GNSS unit 120 may include an inertial measurement unit (IMU). Alternatively, the IMU may be provided at a position different from that of the GNSS unit 120. The signals from the IMU can be used to complement the position data obtained by GNSS. The IMU can measure the inclination and minute movements of the work vehicle 100. By using the data obtained by the IMU to complement or correct the position data based on satellite signals, the positioning performance can be improved. In the present embodiment, the combination of the GNSS unit 120 and the IMU functions as a "positioning system" for measuring or estimating the position and orientation of the work vehicle 100.

[0033] The positioning system may include other types of devices such as a LiDAR sensor or a camera (including an image sensor). When there are features that function as feature points in the environment in which the work vehicle 100 travels, based on the data obtained by the LiDAR sensor or the camera and the environmental map previously recorded in the storage device 170, the position and orientation of the work vehicle 100 can be estimated with high accuracy. The LiDAR sensor or the camera may be used in combination with a GNSS receiver. By using the data obtained by the LiDAR sensor or the camera to correct or complement the position data based on the GNSS signal, the position of the work vehicle 100 can be specified with higher accuracy.

[0034] In the examples shown in FIGS. 1 and 2, an obstacle sensor 130 is provided at the rear part of the vehicle body 101. The obstacle sensor 130 can also be arranged at a part other than the rear part of the vehicle body 101. For example, one or a plurality of obstacle sensors 130 can be provided at any location on the side part, front part of the vehicle body 101, and the cabin 105. The obstacle sensor 130 detects an object existing around the work vehicle 100. The obstacle sensor 130 can include, for example, a laser scanner or an ultrasonic sonar. The obstacle sensor 130 outputs a signal indicating the presence of an obstacle when an object exists closer than a predetermined distance from the obstacle sensor 130. A plurality of obstacle sensors 130 may be provided at different positions on the vehicle body of the work vehicle 100. For example, a plurality of laser scanners and a plurality of ultrasonic sonars may be arranged at different positions on the vehicle body. By providing such a large number of obstacle sensors 130, the dead angle in monitoring obstacles around the work vehicle 100 can be reduced. Note that, as described above, the work vehicle 100 may not be provided with the obstacle sensor 130.

[0035] The prime mover 102 can be, for example, a diesel engine. An electric motor may be used instead of the diesel engine. The transmission 103 can change the propulsion force and moving speed of the work vehicle 100 by shifting gears. The transmission 103 can also switch between the forward and reverse movements of the work vehicle 100.

[0036] The steering device 106 includes a steering wheel, a steering shaft connected to the steering wheel, and a power steering device that assists the steering by the steering wheel. The front wheels 104F are steering wheels, and by changing their steering angle (also referred to as "steering angle"), the traveling direction of the work vehicle 100 can be changed. The steering angle of the front wheels 104F can be changed by operating the steering wheel. The power steering device includes a hydraulic device or an electric motor that supplies an assisting force for changing the steering angle of the front wheels 104F. When automatic steering is performed, the steering angle is automatically adjusted by the force of the hydraulic device or the electric motor under the control from a control device arranged inside the work vehicle 100.

[0037] The plurality of pedals 109 includes an accelerator pedal, a clutch pedal, and a brake pedal. Each pedal is provided with a sensor for detecting depression.

[0038] A coupling device 108 is provided at the rear of the vehicle body 101. The coupling device 108 includes, for example, a three-point support device (also referred to as a "three-point link" or "three-point hitch"), a PTO (Power Take Off) shaft, a universal joint, and a communication cable. The work implement 300 can be attached to and detached from the work vehicle 100 by the coupling device 108. The coupling device 108 can raise and lower the three-point link by, for example, a hydraulic device, and control the position or attitude of the work implement 300. Also, power can be transmitted from the work vehicle 100 to the work implement 300 via the universal joint. The work vehicle 100 can cause the work implement 300 to perform a predetermined operation while towing the work implement 300. The coupling device may be provided in front of the vehicle body 101. In that case, a work implement can be connected to the front of the work vehicle 100.

[0039] The work implement 300 shown in FIG. 2 is a rotary tiller, but the work implement 300 is not limited to a rotary tiller. For example, any work implement such as a mower, a seeder, a spreader, a rake, a baler, a harvester, a sprayer, or a plow can be connected to and used with the work vehicle 100.

[0040] FIG. 3 is a block diagram showing an example of the schematic configuration of the work vehicle 100 and the work implement 300. The work vehicle 100 and the work implement 300 can communicate with each other via the communication cable included in the coupling device 108.

[0041] In the example of FIG. 3, the work vehicle 100 includes a GNSS unit 120, an IMU 125, an obstacle sensor 130, a sensor group 150, an operation switch group 210, a control system 160, a drive device 140, an operation terminal 200, a buzzer 220, and a communication interface (I / F) 190. These components are communicably connected to each other via a bus such as CAN (Controller Area Network), for example. The GNSS unit 120 includes a GNSS receiver 121, an RTK receiver 122, and a processor 123. The sensor group 150 may include, for example, a steering wheel sensor 152, a cutting angle sensor 154, and a transmission (T / M) rotation sensor 156. The switch group 210 may include, for example, a key switch 212, a changeover switch 214 for switching between forward and reverse, and a switch 216 for switching between an automatic steering mode and a manual steering mode. The control system 160 includes a storage device 170 and a control device 180. The control device 180 includes a plurality of ECUs 182, 183, 184, 185. The work implement 300 includes a drive device 340, a control device 380, and a communication interface (I / F) 390. Note that FIG. 3 shows components that are relatively highly related to the automatic steering or automatic traveling operation of the work vehicle 100, and illustration of other components is omitted.

[0042] The GNSS receiver 121 in the GNSS unit 120 receives satellite signals transmitted from a plurality of GNSS satellites and generates GNSS data based on the satellite signals. The GNSS data is generated in a predetermined format such as the NMEA-0183 format, for example. The GNSS data may include, for example, values indicating the identification number, elevation angle, azimuth angle, and reception intensity of each satellite from which the satellite signal was received.

[0043] The GNSS unit 120 shown in FIG. 3 performs positioning of the work vehicle 100 using RTK (Real Time Kinematic)-GNSS. FIG. 4 is a conceptual diagram showing an example of a work vehicle 100 that performs positioning by RTK-GNSS. In positioning by RTK-GNSS, in addition to satellite signals transmitted from a plurality of GNSS satellites 50, a correction signal transmitted from a reference station 60 is used. The reference station 60 can be installed near the field where the work vehicle 100 performs work travel (for example, at a position within 10 km from the work vehicle 100). The reference station 60 generates a correction signal in, for example, the RTCM format based on the satellite signals received from the plurality of GNSS satellites 50 and transmits it to the GNSS unit 120. The RTK receiver 122 includes an antenna and a modem and receives the correction signal transmitted from the reference station 60. The processor 123 of the GNSS unit 120 corrects the positioning result by the GNSS receiver 121 based on the correction signal. By using RTK-GNSS, it is possible to perform positioning with an accuracy of, for example, several centimeters of error. Position information including latitude, longitude, and altitude information is obtained by high-precision positioning by RTK-GNSS. The GNSS unit 120 calculates the position of the work vehicle 100, for example, at a frequency of about once to ten times per second. The GNSS unit 120 outputs time-series position data including information on the calculated position (coordinates).

[0044] Note that the positioning method is not limited to RTK-GNSS, and any positioning method (such as an interferometric positioning method or a relative positioning method) that can obtain position information with the required accuracy can be used. For example, positioning using VRS (Virtual Reference Station) or DGPS (Differential Global Positioning System) may be performed. When position information with the required accuracy can be obtained without using the correction signal transmitted from the reference station 60, the position information may be generated without using the correction signal.

[0045] The IMU 125 includes a three-axis acceleration sensor and a three-axis gyroscope. The IMU 125 may include an orientation sensor such as a three-axis geomagnetic sensor. The IMU 125 functions as a motion sensor and can output signals indicating various quantities such as the acceleration, speed, displacement, and attitude of the work vehicle 100. In addition to the signal output from the GNSS unit 120, the ECU 183 for automatic steering control can estimate the position and orientation of the work vehicle 100 with higher accuracy based on the signal output from the IMU 125. The signal output from the IMU 125 can be used for correcting or complementing the position calculated based on the GNSS signal and the correction signal. The IMU 125 outputs signals at a higher frequency than the GNSS signal. Using the high-frequency signals, the position and orientation of the work vehicle 100 can be measured at a higher frequency (for example, 50 Hz or more). Instead of the IMU 125, a three-axis acceleration sensor and a three-axis gyroscope may be provided separately. The IMU 125 may be provided at a position away from the GNSS unit 120, or may be provided in the same housing as the GNSS unit 120.

[0046] In this embodiment, the combination of the GNSS unit 120 and the IMU 125 functions as a positioning system. The positioning system may further include other types of sensors such as a LiDAR sensor or an image sensor. When there are features that can serve as landmarks in the environment where the work vehicle 100 travels, the position and orientation of the work vehicle 100 can be estimated by matching the sensor data output from these sensors with the environmental map. In such a configuration, an external sensor such as a LiDAR sensor or an image sensor may be included in the positioning system.

[0047] The drive device 140 includes various devices necessary for the running of the work vehicle 100 and the driving of the work implement 300, such as the aforementioned prime mover 102, transmission 103, steering device 106, and coupling device 108. The prime mover 102 may include an internal combustion engine such as a diesel engine. The drive device 140 may include a traction electric motor instead of or together with the internal combustion engine.

[0048] The steering wheel sensor 152 measures the rotation angle of the steering wheel of the work vehicle 100. The steering angle sensor 154 measures the steering angle of the front wheels 104F which are the steered wheels.

[0049] The T / M rotation sensor 156 is a sensor for measuring the rotational speed of the axle connected to the wheel 104, that is, the number of rotations per unit time. The T / M rotation sensor 156 can be, for example, a sensor using a magnetoresistive element (MR), a Hall element, or an electromagnetic pickup. The T / M rotation sensor 156 outputs, for example, a pulse signal proportional to the rotational speed of the gear included in the transmission. The T / M rotation sensor 156 can be used to determine the vehicle speed and traveling direction of the work vehicle 100.

[0050] The measured values by the steering wheel sensor 152, the steering angle sensor 154, and the T / M rotation sensor 156 are used for the automatic steering control by the ECU 183.

[0051] The storage device 170 includes one or more storage media such as a flash memory or a magnetic disk. The storage device 170 stores each sensor and various data generated by the control device 180. The data stored in the storage device 170 may include map data of the environment in which the work vehicle 100 travels and data of the target route for automatic steering. The storage device 170 may also store a computer program for causing each ECU in the control device 180 to execute various operations described later. Such a computer program can be provided to the work vehicle 100 via a storage medium (for example, a semiconductor memory or an optical disk, etc.) or a telecommunication line (for example, the Internet).

[0052] The control device 180 includes an ECU 182 for travel control, an ECU 183 for automatic steering control, an ECU 184 for implement control, and an ECU 185 for display control. The ECU 182 controls the speed of the work vehicle 100 by controlling the prime mover 102, transmission 103, accelerator, and brake included in the drive device 140. The ECU 182 also controls the steering of the work vehicle 100 by controlling the hydraulic device or electric motor included in the steering device 106 based on the measured value of the steering wheel sensor 152. The ECU 183 performs calculations and controls for realizing automatic steering operation based on signals output from the GNSS unit 120, steering wheel sensor 152, cut angle sensor 154, T / M rotation sensor 156, etc. During automatic steering operation, the ECU 183 sends a command to change the steering angle to the ECU 182. The ECU 182 changes the steering angle by controlling the steering device 106 in response to the command. The ECU 184 controls the operation of the hitch 108 to cause the implement 300 to perform a desired operation. The ECU 184 also generates a signal for controlling the operation of the implement 300 and transmits the signal from the communication I / F 190 to the implement 300. The ECU 185 controls the display of the operation terminal 200. The ECU 185 causes, for example, various displays such as a map of the field, the position and target route of the work vehicle 100 in the map, a pop-up notification, and a setting screen to be realized on the display device of the operation terminal 200.

[0053] By the functions of these ECUs, driving by manual steering or automatic steering can be realized. During automatic steering operation, the control device 180 controls the drive device 140 based on the position of the work vehicle 100 measured or estimated by the GNSS unit 120 and the target route stored in the storage device 170. Thereby, the work vehicle 100 can be made to travel along the target route.

[0054] The plurality of ECUs included in the control device 180 can communicate with each other according to a vehicle bus standard such as CAN, for example. In FIG. 3, each of the ECUs 182, 183, 184, 185 is shown as an individual block, but each of their functions may be realized by a plurality of ECUs. Also, an in-vehicle computer integrating at least some of the functions of the ECUs 182, 183, 184, 185 may be provided. The control device 180 may include ECUs other than the ECUs 182, 183, 184, 185. Any number of ECUs can be provided according to the functions.

[0055] The communication I / F 190 is a circuit that communicates with the communication I / F 390 of the work implement 300. The communication I / F 190 performs transmission and reception of signals conforming to an ISOBUS standard such as ISOBUS-TIM, for example, with the communication I / F 390 of the work implement 300. Thereby, it is possible to cause the work implement 300 to execute a desired operation or to acquire information from the work implement 300. The communication I / F 190 may communicate with an external computer via a wired or wireless network. The external computer may be, for example, a server computer in a farm management support system that centrally manages information related to a farm on the cloud and utilizes the data on the cloud to support agriculture. The external computer may be a portable terminal device used by a user.

[0056] The operation terminal 200 is a display terminal for a user to perform operations related to the running of the work vehicle 100 and the operation of the work implement 300, and is also referred to as a virtual terminal (VT) or a terminal monitor. The operation terminal 200 is an example of a display terminal that provides a user interface for performing operations to start and stop the automatic steering control. The operation terminal 200 may include a display device such as a touch screen and / or one or more buttons. By operating the operation terminal 200, the user can perform various operations such as switching the on / off of the automatic steering mode, setting the initial position of the work vehicle 100, setting the target path, recording or editing the map, and switching the on / off of the work implement 300. At least a part of these operations can also be realized by operating the operation switch group 210. Fig. 3 shows, as an example of the operation switch group 210, a key switch 212, a forward / backward switching switch 214, and an automatic steering switching switch 216.

[0057] The buzzer 220 is an audio output device that emits a warning sound to notify the user of an abnormality. The buzzer 220 emits a warning sound, for example, when the work vehicle 100 deviates from the target path by a predetermined distance or more during automatic steering operation. The buzzer 220 may also emit a warning sound when the obstacle sensor 130 detects an obstacle. Instead of the buzzer 220, a similar function may be realized by the speaker of the operation terminal 200.

[0058] The drive device 340 in the work implement 300 performs operations necessary for the work implement 300 to execute a predetermined work. The drive device 340 includes a device according to the application of the work implement 300, such as a hydraulic device, an electric motor, or a pump. The control device 380 controls the operation of the drive device 340. The control device 380 causes the drive device 340 to perform various operations in response to a signal transmitted from the work vehicle 100 via the communication I / F 390. It can also transmit a signal corresponding to the state of the work implement 300 from the communication I / F 390 to the work vehicle 100.

[0059] FIG. 5 is a diagram showing an example of an operation terminal 200 and an operation switch group 210 provided inside the cabin 105. Inside the cabin 105, a switch group 210 including a plurality of switches operable by a user is arranged. The switch group 210 includes, for example, a key switch 212 for switching the start and stop of the engine, a changeover switch 214 (e.g., a shuttle lever or a shuttle switch) for switching forward and backward, a switch 216 for switching between an auto-steer mode and a manual-steer mode, a switch for selecting a gear position of a main transmission or a sub-transmission, and a switch for raising and lowering the work implement 300. The key switch 212 may have any structure, such as a toggle switch or a push-button switch. When the work vehicle 100 is driven by an internal combustion engine, the key switch 212 is also called an "ignition switch".

[0060] FIG. 6 is a block diagram showing an example of the hardware configuration of each ECU in the present embodiment. The ECU 530 includes, for example, one or more processors 531, an input I / F 532, an output I / F 533, a ROM 534, a RAM 535, a bus I / F 536, and a power supply circuit 537. Software (or firmware) for one or more processors to execute at least one process may be implemented in the ROM 534. Such software may be recorded on a computer-readable recording medium and provided via the recording medium or a network.

[0061] The processor 531 is a semiconductor integrated circuit and may include a central processing unit (CPU). The processor 531 may be realized, for example, by a microprocessor. The processor 531 may include a GPU. The processor 531 realizes a desired process by sequentially executing a computer program (or a program module) stored in the ROM 534.

[0062] In addition to, or instead of, the processor 531, the ECU may include, for example, an FPGA, an ASIC, an ASSP, or a combination of two or more circuits selected from these circuits.

[0063] The input I / F 532 is an input circuit to which digital signals or analog signals output from various sensors are input. The output I / F 533 is an output circuit that outputs signals for driving actuators and lamps in the work vehicle 100.

[0064] The ROM 534 is a non-volatile memory such as a writable memory (e.g., PROM or EPROM), a rewritable memory (e.g., flash memory), or a read-only memory. The ROM 534 stores a program for controlling the operation of the processor 531. The ROM 534 does not have to be a single recording medium and may be an aggregate of a plurality of recording media. A part of the plurality of recording media may be a removable memory.

[0065] The RAM 535 provides a working area for temporarily expanding the control program stored in the ROM 534 at boot time. The RAM 535 does not have to be a single recording medium and may be an aggregate of a plurality of recording media.

[0066] The bus I / F 536 can be, for example, a bus interface for connecting the ECU to a CAN bus.

[0067] The power supply circuit 537 is a circuit that steps down a relatively high external voltage to generate the relatively low voltages required by the processor 531, the ROM 534, and the RAM 535, respectively.

[0068] <Operation> Next, the operation of the work vehicle 100 will be described. The control device 180 in the present embodiment can switch between a manual steering mode and an automatic steering mode in response to an operation by a user (e.g., a driver) of the work vehicle 100. In the manual steering mode, the control device 180 controls steering by driving a power steering device in response to an operation of the steering wheel by the user. In the automatic steering mode, the control device 180 drives the power steering device based on the position and orientation (azimuth) of the work vehicle 100 estimated based on the data output from the GNSS unit 120 and the IMU 125, and a target path recorded in advance, thereby controlling steering. Even in the automatic steering mode, the speed is adjusted by the user's accelerator operation and brake operation.

[0069] Figures 7A to 7C are diagrams showing examples of the travel of the work vehicle 100 in the automatic steering mode. Figure 7A schematically shows the state in which the work vehicle 100 travels along a straight target path P. Figure 7B schematically shows the state in which the work vehicle 100 travels along a curved target path P. Figure 7C schematically shows the state in which the work vehicle 100 travels along a target path P including two adjacent straight paths and a curved path connecting them. The target path P is preset and recorded in the storage device 170. When the work vehicle 100 is traveling in the automatic steering mode, the control device 180 calculates the deviation between the position and orientation of the work vehicle 100 estimated based on the data output from the GNSS unit 120 and the IMU 125, and the target path P, and repeats the operation of controlling the steering device so as to reduce the deviation. Thereby, the work vehicle 100 is caused to travel along the target path P.

[0070] FIG. 8 is a diagram schematically showing an example of a target path of a work vehicle 100 that travels automatically in a field. In this example, the field includes a work area 70 where the work vehicle 100 and the working machine 300 perform work, and a headland 80 located near the outer peripheral edge of the field. Which area on the field map corresponds to the work area 70 and the headland 80 can be set in advance by an operation of the user using the operation terminal 200. The target path in this example includes a plurality of parallel main paths P1 and a plurality of turning paths P2 that connect the plurality of main paths P1. The main path P1 is located within the work area 70, and the turning path P2 is located in the headland 80. The dashed line in FIG. 8 represents the working width of the working machine 300. The working width is set in advance and recorded in the storage device 170. The working width can be set by the user operating the operation terminal 200 and recorded in the storage device 170. Alternatively, the working width may be automatically recognized when the working machine 300 is connected to the work vehicle 100 and recorded in the storage device 170. The interval between the plurality of main paths P1 is adjusted according to the working width. The target path can be determined based on the operation of the user before the automatic steering operation is started.

[0071] Next, an example of control during automatic steering by the control device 180 will be described.

[0072] FIG. 9 is a flowchart showing an example of the operation during automatic steering executed by the control device 180. While the work vehicle 100 is running, the control device 180 performs automatic steering operation by executing the operations of steps S101 to S105 shown in FIG. 9. First, the control device 180 estimates the position and orientation of the work vehicle 100 based on the data output from the GNSS unit 120 and the IMU 125 (step S101). For example, the control device 180 estimates the position and orientation of the work vehicle 100 based on the time-series data output from the GNSS unit 120 and the time-series data output from the IMU 125. This process is referred to as "self-position estimation process". Note that the orientation is represented by the angle of the direction in which the work vehicle 100 is facing with respect to the reference direction. For the estimation of the position and orientation, for example, an estimation algorithm using an extended Kalman filter can be used. The estimation of the position and orientation is not limited to the extended Kalman filter and can be executed using any estimation algorithm. Next, the control device 180 calculates the deviation between each of the position and orientation of the work vehicle 100 and the target path (step S102). The deviation of the position represents the distance between the position of the work vehicle 100 at that time and the target path. The deviation of the orientation represents the magnitude of the angle between the orientation of the work vehicle 100 at that time and the direction of the target path. The control device 180 determines whether the calculated deviation of the position exceeds a preset threshold value and whether the calculated deviation of the orientation exceeds another preset threshold value (step S103). When at least one of the deviation of the position and the deviation of the orientation exceeds each threshold value, the control device 180 changes the steering angle by changing the control parameter of the steering device included in the drive device 140 so that the deviation becomes smaller. The control parameter can be, for example, a control command value input to a hydraulic device or an electric motor that changes the steering angle of the front wheels. When neither the deviation of the position nor the deviation of the orientation exceeds each threshold value in step S103, the operation of step S104 is omitted. The control device 180 repeats the operations of steps S101 to S104 until a command to end the automatic steering is issued.The control device 180 can be configured to estimate the position and orientation of the work vehicle 100 at a frequency of about 100 times per second (100 Hz), for example, and determine control parameters for steering. The above operations are executed by the ECU 183 in the control device 180.

[0073] Hereinafter, with reference to FIGS. 10A to 10D, an example of steering control by the control device 180 will be described more specifically.

[0074] FIG. 10A is a diagram showing an example of a work vehicle 100 traveling along a target path P. FIG. 10B is a diagram showing an example of the work vehicle 100 at a position shifted to the right from the target path P. FIG. 10C is a diagram showing an example of the work vehicle 100 at a position shifted to the left from the target path P. FIG. 10D is a diagram showing an example of the work vehicle 100 facing in a direction inclined with respect to the target path P. In these figures, a pose indicating the position and orientation of the work vehicle 100 estimated based on the signals output from the GNSS unit 120 and the IMU 125 is represented as r(x, y, θ). (x, y) are coordinates representing the position of the reference point of the work vehicle 100 in the XY coordinate system, which is a two-dimensional coordinate system fixed to the earth. In the examples shown in FIGS. 10A to 10D, the reference point of the work vehicle 100 is at the position where the GNSS antenna on the cabin is installed, but the position of the reference point is arbitrary. θ is an angle representing the measured orientation of the work vehicle 100. In the illustrated example, the target path P is parallel to the Y-axis, but generally, the target path P is not necessarily parallel to the Y-axis.

[0075] As shown in FIG. 10A, when the position and orientation of the work vehicle 100 are not deviated from the target path P, the control device 180 maintains the steering angle and speed of the work vehicle 100 without changing them.

[0076] As shown in FIG. 10B, when the position of the work vehicle 100 has shifted to the right from the target path P, the control device 180 changes the rotation angle of the steering wheel included in the drive device 140 to change the steering angle so that the traveling direction of the work vehicle 100 inclines to the left and approaches the path P. At this time, in addition to the steering angle, the speed may also be changed. The magnitude of the steering angle can be adjusted according to, for example, the magnitude of the position deviation Δx.

[0077] As shown in FIG. 10C, when the position of the work vehicle 100 has shifted to the left from the target path P, the control device 180 changes the rotation angle of the steering wheel to change the steering angle so that the traveling direction of the work vehicle 100 inclines to the right and approaches the path P. Also in this case, in addition to the steering angle, the speed may also be changed. The amount of change in the steering angle can be adjusted according to, for example, the magnitude of the position deviation Δx.

[0078] As shown in FIG. 10D, when the position of the work vehicle 100 is not greatly deviated from the target path P but the orientation is different from the direction of the target path P, the control device 180 changes the steering angle so that the azimuth deviation Δθ becomes smaller. Also in this case, in addition to the steering angle, the speed may also be changed. The magnitude of the steering angle can be adjusted according to, for example, the magnitudes of the position deviation Δx and the azimuth deviation Δθ respectively. For example, the smaller the absolute value of the position deviation Δx, the larger the amount of change in the steering angle corresponding to the azimuth deviation Δθ may be made. When the absolute value of the position deviation Δx is large, the steering angle will be changed greatly to return to the path P, so inevitably the absolute value of the azimuth deviation Δθ will become large. Conversely, when the absolute value of the position deviation Δx is small, it is necessary to make the azimuth deviation Δθ approach zero. For this reason, it is reasonable to relatively increase the weight (i.e., control gain) of the azimuth deviation Δθ for determining the steering angle.

[0079] For the steering control and speed control of the work vehicle 100, control techniques such as PID control or MPC control (model predictive control) can be applied. By applying these control techniques, the control to bring the work vehicle 100 closer to the target path P can be made smooth.

[0080] In addition, when one or more obstacle sensors 130 detect an obstacle during travel, the control device 180 stops the work vehicle 100 or switches from the automatic steering mode to the manual steering mode. The control device 180 may control the drive device 140 to avoid the obstacle when the obstacle is detected.

[0081] <Automatic Steering Control at Extremely Low Speed Immediately after Key-On> Next, an example of an operation for enabling selection of the automatic steering mode at an extremely low speed (for example, a speed of 0.1 to 0.2 km / h) immediately after a key-on operation is performed to turn on the key switch 212 of the work vehicle 100 and the engine (or the drive electric motor) starts will be described.

[0082] FIG. 11 is a flowchart showing an example of an operation executed by the control device 180 after a key-on operation is performed by the user. The operation shown in FIG. 11 is executed by the ECU 183 in the control device 180. When the key-on operation is performed, the control device 180 executes the operations of steps S210 to S320 shown in FIG. 11. Hereinafter, the operations of each step will be described.

[0083] In step S210, the control device 180 calculates the gyro bias value of the IMU 125. The gyro bias value is the average value of the outputs of the three-axis gyroscope included in the IMU 125 at rest. The control device 180 calculates it by averaging the output values of the gyroscope of the IMU 125 for a predetermined time (for example, about 5 to 7 seconds) while the work vehicle 100 is stopped. This gyro bias value is used to correct the output value of the gyroscope of the IMU 125 in the self-position estimation process of step S280. The control device 180 stores the calculated gyro bias value in a memory (for example, the RAM 535 shown in FIG. 6). After step S210, the process proceeds to step S220.

[0084] In step S220, the control device 180 determines whether the initialization of the orientation is completed. The initialization of the orientation is a process of determining the initial value (i.e., the initial orientation) of the orientation of the work vehicle 100 required for the automatic steering control. If the initialization of the orientation has not been completed yet, the process proceeds to step S230. If the initialization of the orientation is completed, the process proceeds to step S250. Immediately after the key-on operation, since the initialization of the orientation has not been completed yet, the process proceeds to step S230.

[0085] In step S230, the control device 180 executes the orientation initialization process to determine the initial orientation. Details of the orientation initialization process will be described later. After step S230, the process proceeds to step S240.

[0086] In step S240, the control device 180 makes the automatic steering mode selectable. For example, the control device 180 changes an icon for selecting the automatic steering mode displayed on the display of the operation terminal 200 from a state where it cannot be selected to a state where it can be selected. Alternatively, the control device 180 changes from a state where it does not accept the operation of a switch for switching between the manual steering mode and the automatic steering mode to a state where it accepts the operation. In this way, after determining the initial orientation, the control device 180 enables the user to start the operation of the automatic steering control. After step S240, the process proceeds to step S290.

[0087] If it is determined in step S220 that the initialization of the orientation is completed, the processes after step S250 are executed.

[0088] In step S250, the control device 180 determines the traveling direction of the work vehicle 100. In this specification, the "traveling direction" refers to the forward direction or the backward direction. That is, the control device 180 determines whether the work vehicle 100 is moving forward, moving backward, or stopped. Since the operation amount of the automatic steering control differs depending on whether the work vehicle 100 is moving forward or backward, the traveling direction is determined in this step. The method of determining the traveling direction may differ depending on the vehicle speed. The control device 180 determines the traveling direction by, for example, the following method. · When the vehicle speed is less than 0.5 km / h, the traveling direction is determined based on the time-series position data output from the GNSS unit 120. · When the vehicle speed is 0.5 km / h or more, the traveling direction is determined based on the measured value of the T / M rotation sensor 156.

[0089] This determination method is adopted in consideration of the following circumstances. First, when the vehicle speed is 0.5 km / h or more, it is possible to easily determine whether the wheels are rotating forward or backward based on the measured value of the T / M rotation sensor 156. However, when the vehicle speed is less than 0.5 km / h, since the rotational speed of the axle is too low, it is impossible to accurately determine whether the axle is rotating forward or backward based on the measured value of the T / M rotation sensor 156. Therefore, in such a low-speed range, the traveling direction is determined based on the locus of the position of the work vehicle 100 indicated by the time-series position data (i.e., the time change of the position coordinates) output from the GNSS unit 120. Note that in an extremely low-speed range where the vehicle speed is, for example, less than 0.2 km / h, it may not be possible to accurately determine whether the work vehicle 100 is moving forward or backward due to the fluctuation of the position data from the GNSS unit 120. Therefore, in such an extremely low-speed range, in addition to the data output from the GNSS unit 120, the traveling direction can also be determined based on the state of the forward / backward switching switch 214 (e.g., a shuttle lever), i.e., any one of the states of forward, neutral, and backward. In the above manner, the traveling direction of the work vehicle 100, i.e., whether it is moving forward or backward, is determined. After step S250, the process proceeds to step S260.

[0090] In step S260, the control device 180 executes self-position estimation processing. This processing is the same as the processing of step S101 described with reference to FIG. 9. That is, the control device 180 estimates the position and orientation of the work vehicle 100 based on the time-series data output from the GNSS unit 120 and the time-series data output from the IMU 125. Here, when step S260 is first executed after the initial orientation is determined in step S230, the subsequent self-position estimation processing is performed using the determined initial orientation as the orientation of the work vehicle 100. In the self-position estimation processing, with respect to the output value of the gyroscope of the IMU 125, correction is performed by subtracting the gyro bias value calculated in step S210 from the actual output value, and then it is used in the calculation. For the estimation of the position and orientation, for example, an estimation algorithm using an extended Kalman filter can be used. The estimation of the position and orientation is not limited to the extended Kalman filter and can be executed using any estimation algorithm. After step S260, the process proceeds to step S270.

[0091] In step S270, the control device 180 determines whether the automatic steering mode is on (ON). If the automatic steering mode is turned on by the user, the process proceeds to step S280. If the automatic steering mode is off (OFF), that is, the manual steering mode is ON, the process proceeds to step S300. In the manual steering mode, steering is performed by the driver's own steering operation.

[0092] In step S280, the control device 180 determines whether the traveling speed (vehicle speed) of the work vehicle 100 is higher than a predetermined speed. The predetermined speed can be set to a very low speed such as 0.1 km / h, for example. In the present embodiment, after the operation to start the automatic steering control is performed, when the vehicle speed exceeds the predetermined speed, the automatic steering control is started. On the other hand, when the vehicle speed does not exceed the predetermined speed, the automatic steering control is not started and the vehicle enters a standby state. When the vehicle speed is higher than the predetermined speed, the process proceeds to step S290, and the automatic steering control is started. The automatic steering control includes the operations from step S102 to S104 shown in FIG. 9. By the operations from step S102 to S104, the control parameters for steering are adjusted so that the position and orientation of the work vehicle 100 approach the target path. On the other hand, when the vehicle speed is equal to or lower than the predetermined speed, the process proceeds to step S300, and the manual steering state is continued. After steps S290 and S300, the process proceeds to step S310.

[0093] In step S310, the control device 180 determines whether an operation to turn off the key switch 212 (key-off operation) has been performed. If the key-off operation has not been performed, the process proceeds to step S320. If the key-off operation has been performed, the process proceeds to step S330. Note that even if the key-off operation is performed while any of the above-described steps S210 to S300 is being executed, the process also transitions to step S330.

[0094] In step S320, the control device 180 determines whether the work vehicle 100 has been in a stopped state for a predetermined time (for example, 10 seconds) or more. If the work vehicle 100 is not stopped or if the predetermined time has not elapsed since it stopped, the process returns to step S250, and the processes related to the above-described self-position estimation and steering control are repeated. If the stopped state has continued for the predetermined time or more, the process returns to step S210, and the gyro bias value is calculated again. Thus, in the present embodiment, the gyro bias value is calculated and updated each time the work vehicle 100 stops for a predetermined time or more.

[0095] When the key-off operation is performed, the control device 180 determines, in step S330, whether a condition (hereinafter referred to as the "storage condition") for storing (i.e., memorizing) the position and orientation of the work vehicle 100 is satisfied. The storage condition is imposed to prevent a value of a position and orientation with low reliability from being memorized and an incorrect orientation from being determined as the initial orientation at the next key-on. The storage condition may include, for example, all or part of the following (a) to (d). (a) The GNSS positioning accuracy is "RTK". (b) The initialization of the orientation is completed. (c) The vehicle speed at key-off is less than a predetermined value (for example, 0.5 km / h). (d) The value of the orientation is within a normal range.

[0096] Regarding condition (a), when the GNSS positioning accuracy is lower than "RTK" (for example, in the case of "DGPS" or "GPS", etc.), the error of the estimated position and orientation is large, and it becomes difficult to perform highly accurate automatic steering. For this reason, the GNSS positioning accuracy being "RTK" can be imposed as one of the storage conditions. Note that the GNSS unit 120 in the present embodiment is configured to perform positioning in the high-accuracy RTK mode in an environment where radio waves from satellites are easily received, and to switch to a mode with lower positioning accuracy, such as the DGPS mode, in an environment where radio waves are difficult to receive (for example, an environment where radio waves are blocked by tall trees).

[0097] Regarding condition (b), when the initialization of the orientation is not completed, for example, when the key-off operation is performed before the completion of the orientation initialization process in step S230, or when the initialization of the orientation is not normally completed due to an error, the orientation to be stored is not determined. For this reason, the initialization of the orientation being completed can be imposed as one of the storage conditions.

[0098] Regarding condition (c), when the vehicle speed is, for example, 0.5 km / h or more at the time of the key-off operation, the work vehicle 100 may move by inertia even after the key-off, and the position and orientation may change significantly from the position and orientation at the time of key-off. Therefore, it may be imposed as one of the storage conditions that the vehicle speed is less than a predetermined value.

[0099] Regarding condition (d), when the value of the orientation is not within the normal range (for example, 0° to 360°), the value of the orientation is an abnormal value and cannot be trusted. Therefore, it may be imposed as one of the storage conditions that the value of the orientation is within the normal range. In addition to the value of the orientation, it may also be included in condition (d) that the value of the position is within the normal range. Further, it may also be included in condition (d) that the values of other parameters used for steering control other than the position and orientation are within the normal range.

[0100] When the storage conditions including all or part of the above (a), (b), (c), and (d) are satisfied, the process proceeds to step S340. When the storage conditions are not satisfied, the process ends without storing the position and orientation.

[0101] In step S340, the control device 180 stores the values of the position and orientation estimated at that time in a non-volatile memory (for example, ROM534). The stored values of the position and orientation can be used in the orientation initialization process of step S230 when the next key-on operation is performed.

[0102] Next, a specific example of the orientation initialization process of step S230 will be described.

[0103] FIG. 12 is a flowchart showing a specific example of the orientation initialization process of step S230. In this example, step S230 includes the processes from step S231 to S239. Hereinafter, the processes of each step will be described.

[0104] In step S231, the control device 180 determines whether the position and orientation (stored value) at the previous key-off are stored in the non-volatile memory. If there is a stored value, the process proceeds to step S232. If there is no stored value, the process proceeds to step S238.

[0105] In step S232, the control device 180 determines whether each stored value of the position and orientation is within the normal range. The normal range of the position can be preset, for example, as the range of coordinate values (such as latitude and longitude) of the area where the work vehicle 100 can be used. The normal range of the orientation can be preset, for example, as a range such as 0° to 360°. If both stored values of the position and orientation are within the normal range, the process proceeds to step S233. If at least one of the stored values of the position and orientation is outside the normal range, that is, an abnormal value, the process proceeds to step S237.

[0106] In step S233, the control device 180 determines whether the positioning accuracy of the GNSS unit 120 is "RTK". If the positioning accuracy is "RTK", the process proceeds to step S234. If the positioning accuracy is not "RTK" (for example, in the case of "DGPS" etc.), the process proceeds to step S237.

[0107] In step S234, the control device 180 calculates the difference between the stored value of the position and the value of the position currently measured by the GNSS unit 120, and determines whether the difference is smaller than the threshold value. The threshold value can be set, for example, within the range of 10 cm to 50 cm. When the position is expressed in latitude and longitude, it may also be determined whether the difference between at least one of the stored values of latitude and longitude and the measured value is smaller than the threshold value (such as 0.000003 degrees etc.). The threshold value may vary depending on the area where the work vehicle 100 is used. If the difference between the stored value of the position and the current measured value is smaller than the threshold value, the process proceeds to step S235. If the difference is greater than or equal to the threshold value, the process proceeds to step S237.

[0108] In step S235, the control device 180 sets the stored value of the orientation saved in the non-volatile memory as the initial orientation. This initial orientation is used as the initial value of the orientation in the self-position estimation process in subsequent step S260. After step S235, the process proceeds to step S236.

[0109] In step S236, the control device 180 discards (erases) the stored values of the position and orientation from the non-volatile memory. Then, the process proceeds to step S240 shown in FIG. 11, and the user can select the automatic steering mode.

[0110] In this embodiment, when the determination results in steps S231, S232, S233, and S234 are all "No", a process is executed to prompt the user to increase the speed of the work vehicle 100 in order to obtain the initial value of the orientation from the time-series data output from the GNSS unit 120. This is because the orientation at the previous key-off was not saved or the saved value is not reliable. Before that process, when it is determined as No in steps S232 to S234, the process of step S237 is performed.

[0111] In step S237, the control device 180 discards the stored values of the position and orientation from the non-volatile memory. Note that step S237 may be performed after step S238 or S239.

[0112] In step S238, the control device 180 causes the operation terminal 200 to display a message prompting the user to increase the traveling speed of the work vehicle 100 to a reference speed (for example, 0.45 km / h or 0.5 km / h, etc.). Hereinafter, an example in the case where the reference speed is 0.5 km / h will be described.

[0113] FIG. 13A and FIG. 13B are diagrams showing examples of messages displayed on the operation terminal 200. FIG. 13A shows an example of a message displayed when it is determined as "No" in step S231. In this example, since the azimuth at the time of the previous key-off is not saved, a message 92 "The azimuth is unknown. Please increase the speed to 0.5 km / h or more." is displayed. FIG. 13B shows an example of a message displayed when it is determined as "No" in any of steps S232, S233, and S234. In this example, since the previously saved azimuth has been discarded, a message 92 "The previous azimuth has been discarded. Please increase the speed to 0.5 km / h or more." is displayed. Note that the reference speed and the content of the message are not limited to these examples, and various modifications are possible.

[0114] When the user increases the speed of the work vehicle 100 to be equal to or higher than the reference speed according to the instruction content of the message 92 and a predetermined time (for example, 1 second) has elapsed, the process of step S239 is executed. The predetermined time can be 0.1 second or more and 3 seconds or less in one example, and can be 0.5 second or more and 2 seconds or less in another example.

[0115] In step S239, the control device 180 determines the initial azimuth based on the time-series position data from the GNSS unit 120 obtained while the work vehicle 100 travels at a speed exceeding the reference speed for a predetermined time. For example, when the GNSS unit 120 outputs the measured values (coordinate values) of the position at 10 Hz, the control device 180 determines the azimuth of the work vehicle 100 based on the change (i.e., the trajectory) of the 10 coordinate values output in 1 second. The control device 180 stores the determined azimuth in the memory as the initial azimuth. When the process of step S239 ends, the process proceeds to step S240 shown in FIG. 11, and the user can select the automatic steering mode.

[0116] FIG. 13C is a diagram showing an example of a display screen indicating that the automatic steering mode has become selectable. In this example, a message 92 saying "Azimuth initialization is complete. Automatic steering is possible." and an icon 86 for selecting the automatic steering mode are displayed on the operation terminal 200. The user can turn on the automatic steering mode by selecting (for example, tapping or clicking) the icon 86. Note that until the automatic steering mode becomes selectable in step S240, the icon 86 may not be displayed or may be displayed in a non-selectable manner.

[0117] As described above, the control device 180 in the present embodiment stores the azimuth of the work vehicle 100 in a non-volatile memory (ROM534) in response to the key-off operation of the work vehicle 100. Next, after the key-on operation of the work vehicle 100 is performed, the control device 180 starts the automatic steering control with the azimuth stored in the non-volatile memory as the initial azimuth of the work vehicle 100. For example, when the key-on operation is performed in a state where the azimuth at the previous key-off is stored in the non-volatile memory, the control device 180 enables an operation to start the automatic steering control (that is, an operation to turn on the automatic steering mode) in a state where the work vehicle 100 is stopped. After the operation to start the automatic steering control is performed, the control device 180 starts the automatic steering control with the azimuth stored in the non-volatile memory as the initial azimuth of the work vehicle 100.

[0118] By such an operation, after the key-on operation, the user can start the automatic steering control without increasing the speed of the work vehicle 100 to the reference speed (for example, 0.45 km / h, 0.5 km / h, etc.). Thereby, for example, even if the key-off operation is performed with the implement stuck in the ground and then the key-on operation is performed and the engine starts immediately thereafter, it becomes possible to start the working travel by automatic steering, and the convenience can be greatly improved.

[0119] After an operation to start automatic steering control is performed, when the traveling speed of the work vehicle exceeds a predetermined speed (for example, 0.1 km / h), the control device 180 in this embodiment starts automatic steering control (from step S270 to S290 in FIG. 11). Thus, according to this embodiment, automatic steering control can be started from a speed lower than the conventional speed (for example, 0.45 km / h).

[0120] In this embodiment, the control device 180 stores the position and orientation of the work vehicle 100 in a non-volatile memory in response to a key-off operation (step S340). Then, the control device 180 calculates the difference between the position stored in the non-volatile memory and the position measured by the positioning system (GNSS unit 120) in response to a key-on operation (step S234). When the difference is smaller than the threshold value, the control device 180 enables an operation to start automatic steering control with the orientation stored in the non-volatile memory as the initial orientation (steps S235, S240). Further, when the difference is equal to or greater than the threshold value, the control device 180 discards the position and orientation stored in the non-volatile memory (step 237) and invalidates an operation to start automatic steering control until the traveling speed of the work vehicle exceeds the reference speed (step S239). For example, when the difference is equal to or greater than the threshold value, the control device 180 discards the position and orientation stored in the non-volatile memory (step S237), causes a message prompting the user to increase the speed of the work vehicle 100 to be displayed on the display terminal (step S238), and enables an operation to start automatic steering control when the traveling speed exceeds the reference speed (steps S239, S240). When the control device 180 discards the position and orientation stored in the non-volatile memory, as shown in FIG. 13B, a message indicating that the position and / or orientation has been discarded may be displayed on the display device.

[0121] Thus, in this embodiment, the stored orientation is set as the initial position only when the position of the work vehicle 100 does not change significantly between when the key is turned off and when it is turned on again next time. This function can be implemented to handle cases where, after the key-off operation, the work vehicle 100 is transported to another location by another vehicle or the like, causing the position of the work vehicle 100 to change. When the position of the work vehicle 100 has changed significantly, the orientation should also have changed, so the stored orientation is not reliable. Therefore, in such a case, the previously stored orientation is discarded, and the initial position is determined by the method of step S239. This can avoid setting an unreliable orientation as the initial position.

[0122] In the example shown in FIG. 13C, the user interface displayed on the display terminal includes an icon 86 for instructing the start of automatic steering control. When the difference between the previously stored position and the position measured by the positioning system is greater than or equal to a threshold value, as shown in FIG. 13B, the control device 180 invalidates the operation of starting the automatic steering control by making the icon 86 inactive (including erasing) until the traveling speed of the work vehicle 100 exceeds the reference speed. When the difference is less than the threshold value, after setting the stored value of the orientation as the initial orientation, as shown in FIG. 13C, the control device 180 enables the operation of starting the automatic steering control by making the icon 86 active. Thereby, the user can determine whether the automatic steering control can be started based on whether the icon 86 is active or not.

[0123] Note that in this embodiment, in step S320 shown in FIG. 11, the position and orientation of the work vehicle 100 are stored, but only the orientation may be stored. In that case, the processes of steps S233 and S234 shown in FIG. 12 can be omitted.

[0124] When the traveling speed of the work vehicle 100 at the time of the key-off operation in step S310 is equal to or higher than a threshold value (for example, 0.5 km / h), the control device 180 may stop the operation of the work vehicle 100 without storing the azimuth at that time in the non-volatile memory or after storing the azimuth in the non-volatile memory in a manner that it will not be used next time. The "manner that it will not be used next time" includes, for example, a manner of adding a flag indicating that it is unusable to the information of the azimuth and storing it, or a manner of being discarded in the azimuth initialization process (step S230) after the next key-on.

[0125] As described above, the positioning system in the present embodiment includes a GNSS unit 120 that performs positioning using RTK-GNSS. When the positioning by RTK-GNSS cannot be performed when the key-off operation is performed, the control device 180 may stop the operation of the work vehicle 100 without storing the measured azimuth in the non-volatile memory or after storing the azimuth in the non-volatile memory in a manner that it will not be used next time. Thereby, it is possible to avoid performing azimuth initialization based on an azimuth based on a position with low reliability.

[0126] The positioning system in the present embodiment further includes an IMU 125. After starting the automatic steering control, the control device 180 estimates the position and azimuth of the work vehicle 100 based on the first time-series data output from the GNSS unit 120 and the second time-series data output from the IMU 125 (step S260), and performs automatic steering control based on the estimated position and azimuth and the target path (step S290). In the automatic steering control immediately after the key-on operation, the position and azimuth are estimated with the azimuth measured at the time of the previous key-off operation as the initial azimuth. Thereby, highly accurate automatic steering becomes possible from a state of extremely low speed such as 0.1 km / h.

[0127] After starting the automatic steering control, when the vehicle speed exceeds the reference speed, the control device 180 calculates the difference between the first azimuth estimated based on the first time-series data and the second azimuth estimated based on the first time-series data and the second time-series data. If the difference is greater than the threshold value, the automatic steering control may be stopped. This function is based on the fact that when the second azimuth estimated based on the second time-series data generated with the azimuth at the previous key-off as the initial azimuth is significantly deviated from the first azimuth estimated based on the first time-series data obtained from the GNSS unit 120, there is a high possibility that the azimuth at the previous key-off is incorrect. When the difference between the first azimuth and the second azimuth is greater than the threshold value, the control device 180 may stop the automatic steering control and cause the operation terminal 200 to display a warning. In this case, the control device 180 may stop the automatic steering control and perform the processes from step S237 to S239 shown in FIG. 12 to determine the initial azimuth. FIG. 13D shows an example of the warning message 92 displayed on the operation terminal 200 in this case. By implementing such a function, the reliability of the automatic steering control in the extremely low speed range can be improved.

[0128] In the above embodiment, the work vehicle 100 may be a work vehicle that performs automatic driving without a driver. In that case, components necessary only for manned driving, such as a cabin, a driver's seat, a steering wheel, and an operation terminal, may not be provided in the work vehicle 100. The driverless work vehicle may perform operations similar to those in the above-described embodiment by autonomous driving or remote operation by the user.

[0129] A control system that provides various functions in the above embodiment can also be retrofitted to a work vehicle that does not have those functions. Such a control system can be manufactured and sold independently of the work vehicle. A computer program used in such a control system can also be manufactured and sold independently of the work vehicle. The computer program can be provided, for example, stored in a computer-readable non-transitory storage medium. The computer program can also be provided by downloading via a telecommunication line (for example, the Internet).

[0130] As described above, the present disclosure includes a work vehicle, a control device, a control method, and a computer program described in the following items.

[0131] [Item 1] A work vehicle capable of automatic steering operation, A positioning system that performs positioning of the work vehicle, A control device having a non-volatile memory, and comprising The control device estimates the orientation of the work vehicle based on the temporal change in the position measured by the positioning system, performs automatic steering control of the work vehicle based on the position and the orientation of the work vehicle and a set target path, in response to a key-off operation of the work vehicle, stores the orientation of the work vehicle in the non-volatile memory, after a key-on operation of the work vehicle is performed, starts the automatic steering control with the orientation stored in the non-volatile memory as the initial orientation of the work vehicle. Work vehicle.

[0132] [Item 2] When the key-on operation is performed while the orientation is stored in the non-volatile memory, the control device enables an operation to start the automatic steering control in a state where the work vehicle is stopped, and after the operation is performed, starts the automatic steering control with the orientation stored in the non-volatile memory as the initial orientation of the work vehicle. The work vehicle according to Item 1.

[0133] [Item 3] When the running speed of the work vehicle exceeds a predetermined speed after the operation to start the automatic steering control is performed, the control device starts the automatic steering control. The work vehicle according to Item 2.

[0134] [Item 4] The control device In response to the key-off operation, store the position and orientation of the work vehicle in the non-volatile memory. In response to the key-on operation, calculate the difference between the position stored in the non-volatile memory and the position measured by the positioning system. When the difference is smaller than the threshold value, enable the operation of starting the automatic steering control with the orientation stored in the non-volatile memory as the initial orientation. The work vehicle according to any one of Items 1 to 3.

[0135] [Item 5] When the difference is greater than or equal to the threshold value, the control device discards the position and orientation stored in the non-volatile memory and invalidates the operation of starting the automatic steering control until the traveling speed of the work vehicle exceeds the reference speed. The work vehicle according to Item 4.

[0136] [Item 6] The work vehicle further includes a display terminal that provides a user interface for performing operations of starting and stopping the automatic steering control. The control device In response to the key-on operation, calculate the difference between the position stored in the non-volatile memory and the position measured by the positioning system. When the difference is greater than or equal to the threshold value, the control device discards the position and orientation stored in the non-volatile memory, causes the display terminal to display a message prompting the user to increase the speed of the work vehicle, and enables the operation of starting the automatic steering control when the traveling speed exceeds the reference speed. When the difference is smaller than the threshold value, enable the operation of starting the automatic steering control with the orientation stored in the non-volatile memory as the initial orientation. The work vehicle according to Item 5.

[0137] [Item 7] The work vehicle according to item 6, wherein when the control device discards the position and the orientation stored in the non-volatile memory, the control device causes the display device to display a message indicating that the position and / or the orientation has been discarded.

[0138] [Item 8] The user interface includes an icon for instructing the start of the automatic steering control. The control device When the difference is greater than or equal to the threshold value, the operation of starting the automatic steering control by deactivating the icon is invalidated until the traveling speed exceeds the reference speed. When the difference is less than the threshold value, the operation of starting the automatic steering control by activating the icon is enabled. The work vehicle according to item 6.

[0139] [Item 9] When the traveling speed of the work vehicle at the time of the key-off operation is greater than or equal to the threshold value, the control device stops the operation of the work vehicle without storing the orientation in the non-volatile memory or after storing the orientation in the non-volatile memory in a manner that will not be used next, according to any one of items 1 to 8.

[0140] [Item 10] The positioning system includes a GNSS unit that performs positioning using RTK-GNSS. When the positioning by the RTK-GNSS cannot be performed at the time of the key-off operation, the control device stops the operation of the work vehicle without storing the orientation in the non-volatile memory or after storing the orientation in the non-volatile memory in a manner that will not be used next, according to any one of items 1 to 9.

[0141] [Item 11] The positioning system further includes an inertial measurement unit. After starting the automatic steering control, the control device estimates the position and orientation of the work vehicle based on the first time-series data output from the GNSS unit and the second time-series data output from the inertial measurement unit, and performs the automatic steering control based on the estimated position and orientation and the target path. The work vehicle according to any one of Items 1 to 9.

[0142] [Item 12] The control device calculates the difference between the orientation estimated based on the first time-series data and the orientation estimated based on the first time-series data and the second time-series data after starting the automatic steering control, and stops the automatic steering control when the difference is greater than a threshold value. The work vehicle according to Item 11.

[0143] [Item 13] Further comprising a display terminal, After starting the automatic steering control, when the difference between the orientation estimated based on the first time-series data and the orientation estimated based on the first time-series data and the second time-series data is greater than the threshold value, the control device stops the automatic steering control and causes the display terminal to display a warning. The work vehicle according to Item 12.

[0144] [Item 14] A control device for a work vehicle capable of automatic steering operation, A non-volatile memory, One or more processors, Comprising, The one or more processors, Estimate the orientation of the work vehicle based on the time change of the position measured by the positioning system provided in the work vehicle, Perform automatic steering control of the work vehicle based on the position and orientation of the work vehicle and a set target path, In response to the key-off operation of the work vehicle, store the orientation of the work vehicle in the non-volatile memory, After the key-on operation of the work vehicle is performed, the automatic steering control is started using the orientation stored in the non-volatile memory as the initial orientation of the work vehicle. Control device.

[0145] [Item 15] A method executed by one or more computing devices that control the operation of a work vehicle capable of automatic steering operation, comprising: estimating the orientation of the work vehicle based on the change in position over time measured by a positioning system that positions the work vehicle; performing automatic steering control of the work vehicle based on the position and orientation of the work vehicle and a set target path; in response to a key-off operation of the work vehicle, storing the orientation of the work vehicle in a non-volatile memory; after the key-on operation of the work vehicle is performed, starting the automatic steering control using the orientation stored in the non-volatile memory as the initial orientation of the work vehicle; A method including the above.

[0146] [Item 16] A computer program executed by one or more computing devices that control the operation of a work vehicle capable of automatic steering operation, the computer program causing the one or more computing devices to: estimate the orientation of the work vehicle based on the change in position over time measured by a positioning system that positions the work vehicle; perform automatic steering control of the work vehicle based on the position and orientation of the work vehicle and a set target path; in response to a key-off operation of the work vehicle, store the orientation of the work vehicle in a non-volatile memory; after the key-on operation of the work vehicle is performed, start the automatic steering control using the orientation stored in the non-volatile memory as the initial orientation of the work vehicle; A computer program that causes the above to be executed.

Industrial Applicability

[0147] The technology of the present disclosure can be applied to work vehicles used for agricultural purposes, such as tractors, transplanters, or harvesters. The technology of the present disclosure can also be applied to work vehicles used for purposes other than agriculture, such as construction work vehicles or snow removal vehicles.

Description of Reference Numerals

[0148] 50... GNSS satellite, 60... reference station, 70... working area, 80... ground contact, 100... work vehicle, 101... vehicle body, 102... prime mover, 103... transmission, 104... wheels, 105... cabin, 106... steering device, 107... driver's seat, 108... coupling device, 109... pedal, 120... positioning system, 121... GNSS receiver, 122... RTK receiver, 123... processor, 125... inertial measurement unit (IMU), 130... obstacle sensor, 140... drive device, 150... sensor group, 152... steering wheel sensor, 154... cutting angle sensor, 156... T / M rotation sensor, 160... control system, 170... storage device, 180... control device, 182, 183, 184, 185... ECU, 190... communication interface, 200... operation terminal, 210... operation switch group, 212... key switch, 214... forward / backward switching switch, 216... automatic steering switching switch, 220... buzzer, 300... working machine, 340... drive device, 360... control device, 390... communication interface

Claims

1. A work vehicle capable of automatic steering operation, a positioning system for positioning the work vehicle, a control device having a non-volatile memory, comprising: the control device estimates the orientation of the work vehicle based on the temporal change of the position measured by the positioning system, performs automatic steering control of the work vehicle based on the position and the orientation of the work vehicle and a set target path, in response to a key-off operation of the work vehicle, stores the orientation of the work vehicle in the non-volatile memory, after a key-on operation of the work vehicle is performed, starts the automatic steering control with the orientation stored in the non-volatile memory as the initial orientation of the work vehicle. Work vehicle.

2. When the key-on operation is performed while the orientation is stored in the non-volatile memory, the control device enables an operation to start the automatic steering control with the work vehicle in a stopped state, and after the operation is performed, starts the automatic steering control with the orientation stored in the non-volatile memory as the initial orientation of the work vehicle. The work vehicle according to claim 1.

3. After the operation to start the automatic steering control is performed, when the traveling speed of the work vehicle exceeds a predetermined speed, the control device starts the automatic steering control. The work vehicle according to claim 2.

4. The control device in response to the key-off operation, stores the position and the orientation of the work vehicle in the non-volatile memory, in response to the key-on operation, calculates the difference between the position stored in the non-volatile memory and the position measured by the positioning system, when the difference is smaller than a threshold value, enables an operation to start the automatic steering control with the orientation stored in the non-volatile memory as the initial orientation. The work vehicle according to any one of claims 1 to 3.

5. When the difference is equal to or greater than the threshold value, the control device discards the position and the orientation stored in the non-volatile memory and invalidates an operation to start the automatic steering control until the traveling speed of the work vehicle exceeds a reference speed. The work vehicle according to claim 4.

6. further comprising a display terminal that provides a user interface for performing operations to start and stop the automatic steering control, the control device In response to the key-on operation, calculate the difference between the position stored in the non-volatile memory and the position measured by the positioning system. When the difference is equal to or greater than the threshold value, discard the position and the orientation stored in the non-volatile memory, display on the display terminal a message prompting the user to increase the speed of the work vehicle, and enable an operation to start the automatic steering control when the traveling speed exceeds the reference speed. When the difference is less than the threshold value, enable an operation to start the automatic steering control with the orientation stored in the non-volatile memory as the initial orientation. The work vehicle according to claim 5.

7. When the control device discards the position and the orientation stored in the non-volatile memory, the work vehicle according to claim 6, wherein the control device causes the display device to display a message indicating that the position and / or the orientation has been discarded.

8. The user interface includes an icon for instructing the start of the automatic steering control. The control device When the difference is equal to or greater than the threshold value, invalidate an operation to start the automatic steering control by deactivating the icon until the traveling speed exceeds the reference speed. When the difference is less than the threshold value, enable an operation to start the automatic steering control by activating the icon. The work vehicle according to claim 6.

9. When the traveling speed of the work vehicle when the key-off operation is performed is equal to or greater than a threshold value, the control device stops the operation of the work vehicle without storing the orientation in the non-volatile memory or after storing the orientation in the non-volatile memory in a manner that will not be used next time. The work vehicle according to any one of claims 1 to 3.

10. The positioning system includes a GNSS unit that performs positioning using RTK-GNSS. When the positioning by the RTK-GNSS cannot be performed when the key-off operation is performed, the control device stops the operation of the work vehicle without storing the orientation in the non-volatile memory or after storing the orientation in the non-volatile memory in a manner that will not be used next time. The work vehicle according to any one of claims 1 to 3.

11. The positioning system further includes an inertial measurement unit. After starting the automatic steering control, the control device estimates the position and orientation of the work vehicle based on the first time-series data output from the GNSS unit and the second time-series data output from the inertial measurement unit, and performs the automatic steering control based on the estimated position and orientation and the target path. The work vehicle according to any one of claims 1 to 3.

12. The control device calculates a difference between the orientation estimated based on the first time-series data and the orientation estimated based on the first time-series data and the second time-series data after starting the automatic steering control, and stops the automatic steering control when the difference is greater than a threshold value. The work vehicle according to claim 11.

13. Further comprising a display terminal After starting the automatic steering control, when the difference between the orientation estimated based on the first time-series data and the orientation estimated based on the first time-series data and the second time-series data is greater than the threshold value, the control device stops the automatic steering control and causes the display terminal to display a warning. The work vehicle according to claim 12.

14. A control device for a work vehicle capable of automatic steering operation, A non-volatile memory, One or more processors, Comprising The one or more processors Estimate the orientation of the work vehicle based on the time change of the position measured by the positioning system of the work vehicle, Perform automatic steering control of the work vehicle based on the position and orientation of the work vehicle and a set target path, In response to a key-off operation of the work vehicle, store the orientation of the work vehicle in the non-volatile memory, After a key-on operation of the work vehicle is performed, start the automatic steering control with the orientation stored in the non-volatile memory as the initial orientation of the work vehicle. Control device.

15. A method executed by one or more computing devices that control the operation of a work vehicle capable of automatic steering operation, Estimating the orientation of the work vehicle based on the time change of the position measured by a positioning system that performs positioning of the work vehicle, Performing automatic steering control of the work vehicle based on the position and orientation of the work vehicle and a set target path, In response to a key-off operation of the work vehicle, storing the orientation of the work vehicle in a non-volatile memory After the key-on operation of the work vehicle is performed, starting the automatic steering control with the orientation stored in the non-volatile memory as the initial orientation of the work vehicle; A method including this.

16. A computer program executed by one or more computing devices that control the operation of a work vehicle capable of automatic steering operation, to the one or more computing devices, estimating the orientation of the work vehicle based on the temporal change in the position measured by a positioning system that performs positioning of the work vehicle; performing automatic steering control of the work vehicle based on the position and the orientation of the work vehicle and a set target path; in response to a key-off operation of the work vehicle, storing the orientation of the work vehicle in a non-volatile memory; after the key-on operation of the work vehicle is performed, starting the automatic steering control with the orientation stored in the non-volatile memory as the initial orientation of the work vehicle; A computer program that causes this to be executed.

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