Work equipment

Abstract

To solve the problem in which: positioning alignment is performed before work by slip-moving a work machine in correspondence to positional deviation, a range in which work cannot be performed just after starting work is eliminated, and loads are not applied to a farm field and the work machine in positioning alignment is performed, when an inertia coordinate system detected by a reception section device and an inertia measurement device of a GPS is positionally deviated from an absolute coordinate system by latitude and longitude on the ground.SOLUTION: Positions in an inertia coordinate system calculated by a reception section device and an inertia measurement device of a GPS and in an absolute coordinate system detected by sensing imaging means and preliminarily registered latitude and longitude information on the ground are made to coincide with each other by an equation of motion by a coordinate conversion method in a rotary system. Rotational speed of single-wheel or two-wheels of four-wheels is made different from that of other wheels, and four-wheel steering is performed while slipping the wheels and a ground section. Thus, positional deviation is corresponded.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a working machine that enables highly accurate automatic driving in agriculture.

Background Art

[0002] An invention for improving detection accuracy in automatic driving and dealing with displacement of the detection position is described, but there is no description of the traveling mechanism and steering control of the working machine for dealing with the position displacement without work loss in a short time at the start of work. (Patent Document 1)

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above prior art, although there is a description of calculating the position deviation and the azimuth deviation as a countermeasure for the position deviation of the traveling vehicle, there is no particular description of a dedicated countermeasure for the steering method and the traveling mechanism of the traveling vehicle itself to deal with the elimination of the position deviation. In the present invention, it is possible to perform position deviation countermeasure control such as position deviation deviation in a short time with a short working travel distance by the traveling vehicle or to perform position deviation countermeasures before the working travel.

Means for Solving the Problems

[0005] The first invention is solved by the following technical means.

[0006] Equipped with a four-wheel drive and four-wheel steering drive unit, if there is a discrepancy between the position on the pre-set driving line in the direction of travel 600 and the vehicle's position calculated by the GPS receiver and inertial measurement device, the system automatically corrects the position discrepancy by setting the rotation speed of one or two of the four wheels to a different rotation speed from the other wheels, causing movement accompanied by slippage between the wheel and the ground contact area, thereby aligning the front and rear axles 610 with the direction of travel 600.

[0007] The second invention is solved by the following technical means.

[0008] After correcting the positional misalignment, if the direction of travel 600 and the front and rear axles 610 exceed predetermined values ​​and control is required to align the directions, the rotation speed of one or two of the four wheels is set to a different rotation speed from the other wheels, and while the wheels and the contact surface slip, four-wheel steering is performed to move the vehicle by slip. When the direction of travel 600 and the front and rear axles 610 fall within the predetermined values, directional control is automatically performed to return the rotation speeds of all four wheels to the same rotation speed.

[0009] The third invention is solved by the following technical means.

[0010] The coordinate system of the vehicle's position calculated from the GPS receiver and inertial measurement device, and the position of the coordinate system detected by the sensing imaging means and pre-registered ground latitude and longitude information are matched based on the equation of motion using the coordinate transformation method of the rotational system. While driving with this aligned position as a reference, the rotation speed of one or two of the four wheels is set to be different from that of the other wheels, and four-wheel steering is performed while the wheels and the contact surface slip. The system aligns the coordinate system of the vehicle's position, calculated from the GPS receiver and inertial measurement device, with the coordinate system detected by the sensing imaging device. After aligning the direction of travel (600) and the directions of the front and rear axles (610), it automatically switches to a driving mode that returns the rotation speed of all four wheels to the same rotation speed.

[0011] The fourth invention is solved by the following technical means.

[0012] The coordinate system of the vehicle's position calculated from the GPS receiver and inertial measurement device, and the position of the coordinate system detected by the sensing imaging means and pre-registered ground latitude and longitude information, are matched based on the equations of motion using the coordinate transformation method of the rotational system. While driving based on this aligned position, the vehicle uses two-wheel steering to prevent the driving speed from increasing beyond a predetermined speed until the coordinate system of the vehicle's position calculated from the GPS receiver and inertial measurement device matches the coordinate system detected by the sensing imaging means. The speed is then increased to the set speed when the direction of travel 600 and the direction of the front and rear axles 610 match.

[0013] The fifth invention is solved by the following technical means.

[0014] A low-voltage battery 120 is positioned at the front of the aircraft, and a high-voltage main battery 130 and an electric motor 140 are arranged in parallel in the front-to-rear direction behind it. An HST (Hydraulic Continuously Variable Transmission) 150 is installed on the rear side of the vehicle body of the electric motor 140. Power is input from the electric motor 140, and power is distributed from the output shaft of the HST 150 to the axles 190 of the running system and the hydraulic pump 200. A regenerative motor 550 is installed to regenerate excess power from the HST 150, and the regenerative motor 550 charges the low-voltage battery 120. [Effects of the Invention]

[0015] The first invention allows for lateral movement and rotational movement around the center of the vehicle body, making it possible to adjust the starting position with virtually no movement required.

[0016] The second invention allows for directional control if, despite the machine's initial positional alignment, misalignment is found again between the forward direction (600) and the front and rear axles (610) after work has begun. Similar to the first invention, lateral movement and rotational movement around the center of the machine body are also possible, enabling early correction of positional misalignment. Furthermore, once it is confirmed that there is no positional misalignment, the machine automatically terminates slip movement and enters automatic driving mode, thus reducing the load on the field and the implement.

[0017] In the third invention, when there is a deviation between the coordinate system of the vehicle position calculated from the GPS receiver and the inertial measurement unit and the position of the coordinate system detected by the imaging means for sensing, by matching the deviation relationship based on the equation of motion using the coordinate transformation method of the rotation system, alignment can be performed while considering the detection errors of the coordinate systems calculated by the respective methods.

[0018] In the fourth invention, when dealing with position deviation in the case of two-wheel drive, since lateral movement etc. is not possible, the distance traveled until the position deviation is eliminated becomes longer. By not increasing the traveling speed during this period, alignment can be achieved with a short traveling distance.

[0019] In the fifth invention, when the output to the HST decreases, power loss occurs. Therefore, when the output load from the HST is small, by connecting the output to the regeneration motor, energy can be recovered and power loss can be reduced. Charging the low-voltage battery is effective in protecting the control system because it is a robot working machine.

Brief Description of the Drawings

[0020] [Figure 1] Perspective view of the working machine with its exterior removed in an embodiment of the present invention [Figure 2] Enlarged perspective view of the working machine with its exterior removed in an embodiment of the present invention [Figure 3] Electrical system related diagram of the working machine in an embodiment of the present invention [Figure 4] Diagram for aligning the pre-operation position deviation of the present invention by slip lateral movement [Figure 5] Diagram for aligning the pre-operation position deviation of the present invention by slip lateral rearward movement [Figure 6] Diagram for aligning the pre-operation position deviation of the present invention by slip turning movement [Figure 7] Diagram for aligning the position deviation of the present invention by slip turning movement while traveling [Figure 8] Diagram for aligning the position deviation of the present invention by the spin turn of the slip turning movement [Figure 9]Diagram illustrating how misalignment in this invention is corrected using slip turning and braking. [Figure 10] Flowchart for correcting GPS location coordinates [Figure 11] Rotational motion diagrams in inertial and absolute coordinate systems. [Figure 12] Diagram of the relationship between space and time in inertial and absolute coordinate systems. [Figure 13] Equations of motion in space and time obtained by aligning inertial and absolute coordinate systems. [Figure 14] Steering peripheral diagram of the present invention [Figure 15] Operation diagram of the steering actuator of the present invention [Figure 16] Control diagram of the present invention [Figure 17] Engine mounting diagram of the present invention [Modes for carrying out the invention]

[0021] The present invention will be described below based on the embodiments shown in the drawings.

[0022] The implements shown in Figures 1 to 17 are examples of implements in this embodiment.

[0023] The power transmission flow of the present invention will be described below.

[0024] As shown in Figures 1 and 2, inside the hood 110 at the front of the machine, there is a low-voltage battery 120 running horizontally in front of the machine, a high-voltage main battery 130 running horizontally behind it, and an electric motor 140 running horizontally next to the main battery 130, which serves as a power source for operating the machine body and work equipment using the power from the main battery 130.

[0025] The low-voltage battery 120 powers the driver's seat display 330 and the controller 331 of the work equipment. It is a controller and auxiliary battery that controls driving and work, communicates with external devices, and registers data for each driving state, and is a low-voltage battery such as a 12V system. Normally, when a high-voltage battery is also provided, the low-voltage battery is charged by voltage conversion from the high-voltage battery. However, in this invention, as shown in Figure 3, the low-voltage battery 120 and the main battery 130 for high voltage are independent, and the low-voltage battery 120 is charged as regenerative electricity by the regenerative motor 550 from the surplus power of the HST 150. The main battery 130 for high voltage is voltage-controlled by the MDU 131 and controls the electric motor 140.

[0026] The electric motor 140 is equipped with an external fan 141 at its rear end, which is linked to the motor shaft. While the motor is operating, the fan 141 generates airflow that cools the motor, low-voltage battery 120, and main battery 130. The heated air is discharged to the outside through the mesh 111 of the grille at the front of the hood 110 or from the lower front of the hood. The hood 110 is also designed to completely cover the electric motor 140, low-voltage battery 120, and main battery 130, providing protection against rain and car washes, as well as adequate dust protection.

[0027] As shown in Figure 2, the electric motor 140 has its output shaft on the rear side in the longitudinal direction of the vehicle body and powers the HST 150 located behind it. The power transmission method may be by connecting pulleys on each shaft with a belt, or the electric motor 140 and the HST shaft may be directly connected. In the case of belt drive, the shafts of the electric motor 140 and the input and output shafts of the HST 150 are parallel to each other, and the power mechanism is in series and transmits power without bending, resulting in less loss and allowing for a compact arrangement.

[0028] Figure 17 shows a configuration in which the output shaft of the electric motor 140 is located at the rear of the vehicle body and connected to the HST 150, making it easily compatible with the engine 650 configuration. The heavy main battery 130 and electric motor 140 are placed in the hood 110, and the weight is made close to that of the engine 650, so that there is no difference in balance between the electric motor 140 specification and the engine specification. By removing the BMS and inverter 160 from the hood 110 and placing them behind the seat 170, maintenance and heat buildup can be addressed. In this configuration as well, the low-voltage battery 120 is charged as regenerative electricity by the regenerative motor 550 from the surplus power of the HST 150.

[0029] As shown in Figure 3, the BMS (Battery Management System) manages the high-voltage main battery 130 and performs voltage management and other operations according to the control based on commands from the control unit 180. The inverter, also called an MDU, located in the same position controls the rotation speed of the electric motor. In this proposal, the BMS and inverter 160 are integrated and located behind the seat for easy maintenance, and are also designed to withstand heat buildup and dust. Depending on the configuration, the BMS and inverter (MDU) may be located in separate positions.

[0030] With this configuration, the electric motor 140 can either rotate continuously at a fixed speed, or it can be controlled by an inverter that allows its rotation to vary according to the required power. In this embodiment of the present invention, the system controls the rotation speed of the electric motor 140 in response to commands from the control unit 180 of the machine, via the BMS and inverter 160, while managing the main battery 130 for high voltage. Because of this system, even when the machine stops moving and the work equipment is also stopped, the rotation of the electric motor 140 decreases to a range that can generate the standard hydraulic pressure of the HST 150.

[0031] The mechanism of the HST150 and later models of the present invention will be described below.

[0032] While directly receiving the rotation of the electric motor 140 would result in less power loss for the HST150, housing the electric motor 140 within the front hood 110 and using the external fan 141 attached to the electric motor 140 to exhaust heat requires positioning it in the central part of the hood 110 in terms of height. Furthermore, to prevent combustion buildup in the HST150, heat needs to be dissipated to the outside air. While a dedicated fan would be effective, to maintain a compact configuration, the HST150 is mounted below the main frame, open to the outside air.

[0033] Therefore, because there is a vertical misalignment between the electric motor 140 and the HST 150, power is transmitted via belt 141. However, since they are connected in series, power loss is minimal. Similarly, as shown in Figure 3, the axle 190 of the running system, the hydraulic pump 200, and the air compressor 210 are arranged in series, resulting in a configuration with minimal power loss, including the work equipment.

[0034] In this configuration, the power system consists of electric motors 140 and air compressors 210 arranged in series, and to prevent heat buildup, they are mounted on electric belts on all sides (up, down, left, and right). Furthermore, by positioning the air compressor 210 above the work machine 220, it is possible to prevent damage from dust during suction.

[0035] Let me explain the regenerative motor 550.

[0036] While the rotational speed of the electric motor 140 can be controlled by the BMS and inverter 160, the travel speed and PTO 230 rotational speed are changed by the HST, so the electric motor 140 is fixed at high rotation during operation. Therefore, if the travel speed is reduced or the output of the PTO 230 is decreased during operation, excess power is generated in the HST 150 because it is receiving the full power from the electric motor 140. In some cases, the HST 150 may use internal power relief to prevent the oil temperature from rising, but in this invention, if the output of the HST 150 to the travel system or the output of the PTO 230 decreases, the excess power to the HST is handled by transmitting power to the regenerative motor 550. The HST 150 has a power output shaft 151 to the regenerative motor 550, from which power is input to the regenerative motor 550. The regenerative motor 550 is a motor for generating low voltage, which generates DC 12V and charges the low-voltage battery 110.

[0037] In another embodiment, a system could be conceivable in which the regenerative motor 550 generates high voltage, and the regenerated electricity charges the main battery 130, which is a high-voltage battery. In this case, the voltage is stepped down by a converter and converted to a low voltage to charge the low-voltage battery 120.

[0038] The fifth invention, regenerative power recovery, involves generating surplus power using a low-voltage regenerative motor when the HST output decreases and excess power is generated, and directly charging the low-voltage battery 110. This not only eliminates the need for a converter from the high-voltage battery to the low-voltage battery, but also prevents energy loss by eliminating the need for voltage conversion by a converter from high voltage to low voltage and the exchange of electricity between batteries.

[0039] Thus, the fifth invention demonstrates the characteristics of a work machine that enables automatic operation. In slip movement, the load is large, and the HST, which is the power source of the drive system, must be configured to output power stably and immediately. For this reason, power input to the HST is required above a certain rotational speed. Although the electric motor receives rotational speed change commands from the BMS, it cannot respond immediately to the HST's speed changes, so it is often kept at a high rotational speed. In other words, in a mechanism that transmits power from the electric motor to the HST and hydraulic pump, it is difficult to finely control the rotational speed of the electric motor to prevent power loss, and a method of recovering excess power from the output of the HST and hydraulic pump is desirable.

[0040] When the output to the HST decreases in this way, power loss occurs. Therefore, when the output load from the HST is low, energy can be recovered and power loss can be reduced by connecting the output to the regenerative motor. In addition, charging the low-voltage battery is effective in protecting the control system, as it is a robotic work machine.

[0041] The hydraulic pump 200 of the present invention will now be described.

[0042] Rotational power is obtained from the output shaft of the HST150 to operate the hydraulic pump 200, which in turn operates the hydraulic actuator 260. The hydraulic actuator 260 is connected to the hydraulic actuator by hydraulic piping 270. In this invention, the system is operated by an electric motor 280, but a configuration using a small hydraulic motor is also possible. In this invention, the hydraulic pump is operated by receiving power from the output shaft of the HST, but in an alternative configuration, the hydraulic pump can receive power directly from an electric motor 140.

[0043] The air compressor 210 of the present invention will now be described.

[0044] An air compressor 210 is positioned under the seat 170 via the output of the HST150. By positioning it above each workpiece within the machine, it is possible to sort dust and debris by weight during suction. The compressed air generated by the air compressor 210 can be used for suction work using an air nozzle, or for operating the workpieces using an air cylinder.

[0045] This section describes the driver's seat display 330 control panel.

[0046] When driving manually, the battery capacity, vehicle speed, main and sub-transmission settings, GNSS sensitivity, the status of the vehicle's driving line and target line, and the fuel gauge (if using an engine) are displayed, and these settings can be adjusted on the display 330 using various levers and dials. The same functions can also be displayed and adjusted using the remote control.

[0047] The operation system control device 340 will now be described.

[0048] The implement can be operated using the control device 340 located to the right of the driver's seat. The control device 340 is equipped with a large display that shows images captured by imaging means A410, B411, C412, and D413, allowing for the operation and settings of the implement. Depending on the implement installed, the display settings screen and the functions of the control levers and switches are changed.

[0049] This section explains autonomous driving and manual driving.

[0050] This machine is a robotic work machine 100, capable of automatic operation based on pre-configured settings. It can also be remotely controlled via a remote control.

[0051] This vehicle is equipped with a ROPS 300 to counter tipping, positioned behind the seat 170. The ROPS 300 also has a GPS receiver 310 and an inertial measurement unit (IMU) 320 at its upper tip to confirm and correct the vehicle's position. By utilizing this receiver, the vehicle can accurately determine its own position, enabling autonomous driving.

[0052] The robotic work machine 100 can also be operated manually by riding on it. The machine is equipped with a seat 170 and a steering wheel 171 in the center so that a person can operate it, and when the driving control device 175 detects motion, the operation is switched, making it possible for a person to operate it while seated.

[0053] This section explains the basic positional error correction and automatic steering of the robotic work machine 100.

[0054] The GPS receiver 310 and the positioning unit, which is the positioning method, consist of positioning satellites and mobile stations located at base stations at known locations. This allows for the accurate determination of the mobile station's position, i.e., the position of the work machine, from the position information transmitted from the positioning satellites to the mobile station and the correction position information transmitted from the base stations to the mobile station.

[0055] The base station consists of a fixed communication device, a GPS receiver 310 that receives position information from positioning satellites, and a fixed data transmission antenna that transmits correction position information to the mobile station.

[0056] The mobile station consists of a mobile communication device, a mobile GPS receiver that receives position information from positioning satellites, and a mobile data transmission antenna that receives correction position information from a base station. The control unit 180 of the work machine is formed from a processing unit consisting of a CPU, a storage unit consisting of ROM, RAM, a hard disk drive, flash memory, etc., and a communication unit for data communication with the outside.

[0057] The GPS receiver 310 should use a method suitable for the work area, such as standalone positioning, DGPS (Dual GPS) or RTK (Real-Time Kinematics). However, if the ground clearance of the GPS receiver 310 fluctuates due to the tilt or vibration of the machine, a coordinate position different from the actual machine position will be measured, reducing reception accuracy and causing the machine to move in a direction deviating from a straight line. To prevent this, an inertial measurement unit (IMU) 320 is provided in addition to the GPS receiver 310. The inertial measurement unit (IMU) 320 corrects the position coordinates acquired by the GPS receiver 310 to the control unit 180 based on the difference between the height from the ground to the GPS receiver 310 when the robot work machine 100 is tilted and the height from the ground to the GPS receiver 310 when it is not tilted.

[0058] The height from the ground to the GPS receiver 310 is determined by measuring the tilt and other behaviors of the robot work machine 100 using the three-axis acceleration sensor and angular velocity sensor built into the inertial measurement unit (IMU) 320. In addition, a compass sensor 311 is provided to allow the control unit 180 to more reliably determine whether the direction of travel of the machine by the automatic straight-line system is correct. The correction of the position coordinates at this time is shown in SS1 to SS5 of Figure 10. As a result, the course of the machine can be determined by the measured direction, further improving the accuracy of straight-line travel.

[0059] The position information acquired by the GPS receiver 310 is corrected by the control unit 180 based on the information detected by the inertial measurement unit (IMU) 320 and the direction sensor 311. The control unit 180 then compares the current position information with previously acquired position information, and if the difference in position information exceeds an acceptable range, it steers the left front wheel 560 and the right front wheel 570 in the left and right directions in order to return the aircraft to a straight-ahead driving position.

[0060] To automate the steering of the left front wheel 560 and the right front wheel 570, an automatic steering device 172 is provided that rotates the steering 171 with a steering actuator 173. As shown in SS6 to SS9 of Figure 15, the automatic steering device 172 adjusts the amount of operation of the steering actuator 173 based on the difference between the X coordinate of the current position information calculated by the control unit 180 and the X coordinate of the previously acquired reference position information. This causes the steering 171 to turn left or right to direct the vehicle towards a straight-ahead driving position, and when the vehicle reaches a straight-ahead driving position, the steering actuator 173 is stopped, thereby stopping the automatic steering 172 of the steering 171.

[0061] The steering actuator 173 consists of an electric or hydraulic motor or a cylinder. With this configuration, the steering 171 is automatically steered according to the difference in the X coordinate of the calculated position information, and the machine can be automatically adjusted to a straight-line driving position. This prevents the working position of the work device from shifting laterally, making it less likely that there will be areas in the field where work has not been performed. As a result, there is no need to perform work manually in areas where work was not performed, and the workload of the operator is reduced.

[0062] This section explains the vehicle's position and inertial coordinates calculated from the GPS receiver and inertial measurement device.

[0063] In the robotic work machine 100, the coordinates of the GPS receiver 310 are superimposed on the X-axis, with east-west as the X-axis and north-south as the Y-axis, to determine the robot's own coordinate position. The coordinates of one side of the field, which is the starting point of the robotic work machine 100's automatic straight-line movement, and the other side of the field, which is the ending point of the automatic straight-line movement, are also acquired.

[0064] With the first reference point A601 acquired, the second reference point B602 is acquired, and this straight line becomes the direction of travel 600. If the front and rear axles 610 of the vehicle, the so-called direction line, are tilted relative to the travel line toward the direction of travel 600, the direction is changed as shown in Figure 6.

[0065] The first reference point A601 and the second reference point B602 are moved and set at predetermined positions at one end and the other end of the field, for example, at the position where the implement begins to turn after completing a straight run and at the position where it begins to run straight after completing a turn, and then the implement is run straight.

[0066] As described above, when a first reference point A601 and a second reference point B602 are newly acquired, the reference line connecting the Y coordinates of the first reference point A601 and the second reference point B602 becomes the guideline line for automatic straight driving that has been set to be moved. The system determines whether the X coordinate of the position coordinate of the moving machine matches the X coordinate of the guideline line for automatic straight driving. If they do not match, the automatic steering device 172 automatically steers the steering 171 in the direction that matches, thereby achieving automatic straight driving. The control unit 180 compares the Y coordinate of the position coordinate acquired by the GPS receiver 310 with the Y coordinate of the reference line, activates the steering actuator 173 to rotate the steering 171 left and right, and starts control to move the robot work machine 100 to the position where it should drive in a straight line. This automatic steering ends when the steering 171 is operated to an angle that turns the moving machine body within a predetermined time, or when the automatic straight driving setting member 207 is operated in the second direction. The steering angle of the steering wheel 171 is detected by the steering potentiometer 172. When the vehicle body 2 reaches a location that coincides with the Y coordinate of the first reference point A or the second reference point B, the automatic straight-line control may be terminated and the system may enter a turning control mode.

[0067] In this embodiment, the position information of the reference line is acquired for each work process, and the position information of the target line for the next work process is determined each time. This minimizes the deviation of the reference line, reduces the deviation of the target line in the next work process, and also enables alignment in the automatic rotation process.

[0068] As time passes, the reference line may shift, or it may shift due to the influence of clouds, etc. Therefore, by acquiring a new reference line for each work process as described above, the shift in the reference line can be minimized, the target line in the next planting work process can also be made less likely to shift, and row alignment can be performed in the automatic turning process.

[0069] This section explains four-wheel drive and four-wheel steering.

[0070] This work machine features four-wheel drive and four-wheel steering. It is equipped with a 560mm front left wheel, a 570mm front right wheel, a 580mm rear left wheel, and a 590mm rear right wheel. While all four wheels (560, 570, 580, and 590) are powered by the same HST150 motor, individual speed control is performed for each axle in the power transmission path. The rotational speed can be individually adjusted using planetary gears in the final drive case of each wheel. Furthermore, the brakes on each wheel can be individually applied via electronic control.

[0071] Each wheel is also steerable via an individual link. In this invention, individual electric gear motors are provided on each axle: front left motor 561, front right motor 571, rear left motor 581, and rear right motor 591, and their rotation is controlled by the control unit 180. Potentiometers 562, 572, 573, and 574 are provided on each axle to individually detect the steering angle. If the detected angle differs from the steering angle indicated by the control unit 180, each electric gear motor is activated.

[0072] Figures 4 to 9 show embodiments of the first invention.

[0073] As mentioned above, this invention allows for automatic operation, and the rotation speed of each of the four wheels can be changed, as can the direction of each wheel. Therefore, lateral movement and rotational movement around the center of the vehicle body are also possible. With a two-wheel steering mechanism, if a misalignment was detected, the vehicle had to be gradually adjusted while driving. However, if the misalignment exceeded 1 meter, there was an area where adjustment could not be performed while driving, so the vehicle had to be adjusted by switching between forward and reverse steering before starting work, which could damage the field. With this invention, since lateral movement and rotational movement around the center of the vehicle body are also possible, it is possible to adjust the misalignment at the starting position with almost no driving.

[0074] Let's explain how to drive. Obtain the first reference point A601 and the second reference point B602 as described above, and determine the driving line. The vehicle's position, calculated from the GPS receiver and inertial measurement device, is inertial coordinates.

[0075] In autonomous driving, the system adjusts the position detected by inertial coordinates, the position determined by the driving line obtained from the first reference point A601 and the second reference point B602, and the positional deviation of the vehicle's position calculated from the GPS receiver and inertial measurement device, while aligning the direction of travel 600 with the front and rear axles 610, thereby aligning the direction of travel and position.

[0076] Figure 4 shows a case where the direction of travel is the same as the direction of travel 600, but the vehicle's center position 611 is not on the travel line in the direction of travel 600 and is misaligned. In conventional technology, this misalignment is corrected while driving. Therefore, even though the direction is correct, a change in direction is permitted to correct the misalignment by changing the direction within a predetermined range, and the position is gradually brought into the travel line while driving. In this type of position correction, there will be parts where work has not been done until the vehicle is aligned with the travel path.

[0077] While a system that simply follows a designated path would suffice, this invention is a work machine, and if any part of the work is not completed, that part must be addressed again. To address this inconvenience, it would be ideal if the position could be adjusted by moving the machine without moving, rather than gradually adjusting the position while driving.

[0078] As shown in Figure 4, if the vehicle is misaligned to the left with respect to the direction of travel of 600, the front left wheel (560) and the front right wheel (570) should be steered to the left. The rear left wheel (580) and the rear right wheel (590) should be steered in the opposite direction to the front wheels. In this case, since the front wheels are on the left, the steering should be directed to the right. Then, the front left wheel (560) and the front right wheel (570) should rotate backward, and the rear left wheel (580) and the rear right wheel (590) should rotate forward.

[0079] In other words, the steering direction and direction of travel are set to point to the right from the center of the vehicle body. Through this steering and wheel rotation control, the vehicle body moves as if the front and rear wheels are pushing against each other, and while the wheels and contact points slip, it can move parallel to the right. This allows for positioning control through parallel movement without having to perform work runs or change direction to align something that is already aligned.

[0080] Figure 5 shows a situation where the direction is correct, but there is a positional misalignment, requiring lateral and backward movement. In this case, the vehicle can be moved diagonally by steering the front and rear wheels in the same direction. This diagonal movement method is good when the distance of the positional misalignment is long, but with small distances, it may overshoot, and switching steering at this point may damage the field. Therefore, the slip driving method shown in Figure 4 is used. The difference in the length of the arrows in the figure indicates the difference in wheel rotation speed. In this figure, the front left wheel rotates at 560 and the front right wheel rotates at 570 to the left, and the rotation speed is set to be fast for backward rotation. The rear left wheel rotates at 580 and the rear right wheel rotates at 590 to the right, and the rotation speed is set to be slow for forward rotation. As a result, the vehicle gradually moves diagonally backward in parallel. The rotation speed of the front and rear wheels is changed and controlled while observing the positional misalignment. For example, if it is determined during movement that the vehicle is not moving backward enough, the rotation speed of the rear left wheel at 580 and the rear right wheel at 590 can be further reduced to compensate.

[0081] Figure 6 shows how to handle a situation where both direction and position are misaligned. The vehicle is facing left relative to the direction of travel, and its position is judged to be shifted forward on the left. In this case, the same control as in Figure 5 is used, but the difference lies in the steering angles of the front and rear wheels. By making the leftward steering angle of the front wheels larger than the rightward steering angle of the rear wheels, the amount of movement at the front is increased, allowing for rotational movement. This makes it possible to align the direction of travel 600 with the front and rear axles 610, and to match both the coordinate positions while rotating backward.

[0082] Figure 7 illustrates a method of positioning while the vehicle is in motion. However, this method differs from conventional techniques because it is performed over short distances while the vehicle is slipping, rather than gradually. In Figure 7, the front and rear axles 610 are pointed to the left with respect to the direction of travel 600, and the vehicle's coordinate position is determined to be shifted to the left. All four wheels are turned to the right, but because this involves rotational movement, the steering angle of the front wheels is increased, and the rotation speed of the front wheels is also increased. In this case, because the positioning is performed while the vehicle is in motion, there will be some deviation in the position detection accuracy, so the steering of the front wheels is kept flexible for a while and does not enter into steering fixed control for straight-line driving.

[0083] Figure 8 shows spin control. While crawler-type combine harvesters can compensate by changing the direction of rotation of the left and right wheels, four-wheeled vehicles cannot slip and rotate in the field due to low ground pressure. Therefore, the steering of all four wheels is kept in the same direction, and the rotation speed of the front and rear wheels is changed to compensate, or the rotation speed of the left and right wheels is changed, or the rotation of one of the inner wheels that acts as the center of rotation is stopped or drastically reduced, so that the vehicle rotates around that wheel as the axis.

[0084] Figure 9 shows vehicle rotation control using fixed wheels. In this figure, the brake is applied to the right rear wheel 590, driving the left front wheel 560 and the left rear wheel 580. The front wheel 570 only rotates passively. This control enables directional change control with the right rear wheel 590 as the central axis.

[0085] Figures 4 through 9 show typical movements of slip driving. The basic principle is to induce slipping by changing the rotation speed of one or two of the four wheels. While this is difficult on asphalt in automobiles, slip driving is easy for implements working on soil in fields. By combining four-wheel drive and four-wheel steering, it is possible to perform positional changes without working, and by incorporating positional correction before work begins, it becomes possible to immediately start good automated driving control. Rather than adjusting while working, positioning can be done before starting work, so the robot can operate without missing any tasks.

[0086] The second invention explains that if the position deviation control reacts to even a minute difference, it must constantly perform slip driving, which can also lead to malfunctions. To address this, it is necessary to set a range for position deviation. A predetermined angle is set for the directional angle, and if the deviation falls within this range, position deviation detection continues and steering control is performed, but the rotation speed of all four wheels is set to the same speed, stopping slip driving caused by the difference in rotation speed of the drive wheels. This eliminates driving loss, enables stable straight-line driving, and also improves fuel efficiency. The implement itself is also less burdened, which is good in terms of consumable parts. Thus, while slip driving is highly effective, it also has risks, and by incorporating control that allows for early response and early release, the automatic driving control can be handled stably.

[0087] This invention describes a third invention that matches the coordinate system of the vehicle's position calculated from a GPS receiver and an inertial measurement device with the position of the coordinate system detected by a sensing imaging means and pre-registered ground latitude and longitude information, based on the equation of motion using a rotational coordinate transformation method.

[0088] This invention matches the inertial coordinate system calculated from a GPS receiver and an inertial measurement device with the absolute coordinate system position detected by a sensing imaging means and pre-registered ground latitude and longitude information, based on the equation of motion using a coordinate transformation method for a rotating system. It then adjusts the rotation speed of one or two wheels to be different from that of the other wheels, and performs four-wheel steering while causing slippage between the wheels and the ground contact area.

[0089] First, let's explain the inertial coordinate system. The GPS receiver 310 uses one of the following methods, such as standalone positioning, DGPS (Digital GPS) (Digital GPS), or RTK (Real-Time Keying), which is appropriate for the area where the work is being performed. However, regardless of the method used, when the Earth is used as the coordinate reference, there is an offset in the measured coordinates. To compensate for this offset, information from multiple satellites and position information from ground base stations are used to correct the offset.

[0090] Existing technologies include inventions that correct position information using an inertial measurement unit (IMU) 320, in addition to satellite information. However, the inertial measurement unit can only be calculated by measuring forces such as yaw rate caused by the movement of the robotic work machine 100. When stationary, it can only detect obstacles and does not fulfill its intended role of correcting position detection.

[0091] In this invention, positional deviation is corrected while the vehicle is stopped at the start of work. The inertial measurement device IMU320 is not functioning properly and is unable to adequately correct the coordinate system based on satellite data from the GPS receiver 310. However, the coordinate system of the vehicle's position calculated from the GPS receiver 310 and the inertial measurement device IMU320 is defined as the inertial coordinate.

[0092] Next, let's explain absolute coordinate systems. The robot work machine 100 has field location data 621 in the control unit 180, which has pre-registered coordinate systems for the field to be worked on and the starting position of work in that field. The absolute position on the Earth's surface is registered from latitude and longitude. As field data, the starting position of work and several reference positions have their absolute position coordinates registered as coordinate numerical data, and it is also possible to register and read the data as field map data. By selecting a target position on the map from the field location selection terminal 620, the absolute coordinates of the reference points of each field can be read.

[0093] The robotic work machine 100 is also equipped with imaging means B411, C412, and D413. These images are used to check crops in the field and obstacles in the surrounding area, and also have a function to determine direction. Images captured by imaging means B411, C412, and D413 at a predetermined work start position are registered. The control unit 180 has a function to calculate the directional deviation from the arrangement and area of ​​the structures in these pre-captured images. The robotic work machine 100 determines the amount of movement of the machine by comparing the images from imaging means B411, C412, and D413 with the pre-registered images.

[0094] In the absolute coordinate system, the initial offset amount of the absolute coordinate position is corrected using a coordinate reference for each field based on the Earth and a coordinate reference obtained by image alignment using an imaging device. This coordinate position is more accurate than the position calculated from the GPS receiver 310 and can be used as an absolute coordinate.

[0095] On the other hand, the position data from the GPS receiver 310 is made more accurate through correction by the inertial measurement unit (IMU) 320. Although there is a large error at the starting position of field work that does not involve driving, these coordinates are used as inertial coordinates to align with the absolute coordinates.

[0096] Thus, in terms of coordinate positions, there are absolute coordinates and inertial coordinates. Furthermore, the absolute coordinates in this proposal are pre-registered field positions, which are accurate at that point in time. However, once the work vehicle starts moving, even if absolute coordinates are set, it relies heavily on inertial coordinates. Taking these issues of conventional technology into account, if the absolute coordinates and inertial coordinates can be aligned at the start of work, any subsequent positional deviation will be limited to the offset amount inherent in the GPS receiver 310 and the position defined as absolute coordinates from the beginning, and a high level of accuracy in position calculation can be expected.

[0097] To address these challenges, the present invention involves moving the robotic workpiece 100 at the start of work to align the absolute coordinates and inertial coordinates at the start of work. As a means of aligning the absolute coordinates and inertial coordinates, the inertial coordinates are treated as virtual coordinates and controlled to align them with the absolute coordinate system. One approach is to have the robotic workpiece 100 align its coordinates while slipping.

[0098] In reality, the positional discrepancy between the inertial and absolute coordinates of a GPS receiver 310 is often only a few centimeters to tens of centimeters, and does not exceed a few meters, so it can be corrected by a slight lateral movement. In fact, the azimuth discrepancy is often larger. Taking this into consideration, a logic using a rotational coordinate system is applied that prioritizes azimuth alignment and allows for positional discrepancy correction. This logic aligns the starting points of the X and Y axes of the absolute and inertial coordinates and corrects their respective discrepancies.

[0099] In Figures 11 and 12, as a strategy for aligning absolute coordinates and inertial coordinates, control is performed based on the equations of motion using the coordinate transformation method for rotational systems. The coordinates of the GPS receiver 310 are superimposed on the absolute coordinate system, with east-west as the X-axis and north-south as the Y-axis. The axial displacement angle of the inertial coordinate system is calculated, and the amount of spatial movement in a predetermined time is estimated from the movement speed and slip ratio from the current position. The estimated time to reach the matching position and the movement speed of the robot workpiece 100 along the X and Y axes at that position are calculated to determine the steering direction and movement speed of the robot workpiece 100's initial movement.

[0100] This logic is applied because both absolute and inertial coordinates utilize positional information from satellites, and there is always some offset between them and ground coordinates. Therefore, the strategy involves resolving the offsets between the two while simultaneously correcting the positional discrepancies between them. Consequently, this is not a method of numerically calculating the difference between absolute and inertial coordinates and then adjusting the position by measuring the distance traveled by this difference. To put it simply, the robotic workpiece 100 receives rotational energy, causes a sideslip, and moves to the target position. This sideslip is described as having velocity in the X and Y axes, but also being affected by sliding friction between it and the ground. An equation of motion is then established based on this, and the steering direction and speed of the robotic workpiece 100's initial movement are determined, and it is assumed that they match in terms of spatial movement over time.

[0101] Figure 11 shows the equations of motion for the rotating system using the coordinate transformation method described above. The position indicated by X and Y in the coordinate system is the absolute coordinate system. The coordinates indicated by X' and Y' are the inertial coordinates.

[0102] Currently, the robot work machine 100 is detected at p(x, y), and a positional misalignment of ωt occurs between the absolute coordinate system and the inertial coordinate system. In this case, the rotational alignment of both the absolute coordinate system (X, Y) and the inertial coordinate system (X', Y') can be calculated using the respective transformation formulas (S1, S2).

[0103] Furthermore, the robotic work machine 100 at p(x,y) is considered to have a movement amount F acting on it as part of its movement for positioning, and it is defined that movement amounts Fx and Fy occur at each coordinate. To capture this movement amount as it changes over time and to manage and control the movement over time, a time-dependent equation of motion is defined. In this invention, the inertial coordinate system is aligned. (S3,S4) In this equation, m corresponds to the weight used when the robotic work machine 100 moves, and ω is the angular velocity in the X and Y axes. In other words, it means that it moves while slipping due to sliding friction on each axis.

[0104] Figure 12 shows the logic for estimating the trajectory of changes in spatial (distance) and temporal equivalents, assuming that absolute coordinates and inertial coordinates are coincided. S5, S6, S5a, S5b This logic compares the spatially equivalent (distance-based) and temporally equivalent changes with the original n, and then adjusts the change of n+1 to match.

[0105] Figure 13 defines S7 and S8 as equations for the change of a small change in Δt. By using these small changes as the directional components in Fx' and Fy', S9 and S10 can be calculated. Using these equations of motion, the time evolution of sideslip motion can be estimated.

[0106] The initial velocities in the X and Y directions due to slipping are added to the logical equations S9 and S10, and the slip ratio is taken into account to establish the equations of motion. Then, in the coordinate transformation equations S1 and S2, calculations are performed to make the absolute coordinates and the inertial coordinate system match by using methods such as the Runge-Kutta method.

[0107] Through computational analysis, the steering direction, wheel rotation speed, and travel time are calculated, allowing for positioning by moving in this direction for a predetermined time.

[0108] The coordinates that are matched through this control are re-registered as absolute coordinates, and in subsequent operation of the work machine, automatic operation is performed while correcting the position using the coordinate system of the vehicle's position calculated from the GPS receiver 310 and the inertial measuring device IMU 320, and the position of the coordinate system detected by the sensing imaging means.

[0109] Furthermore, when the inertial coordinate system of the vehicle's position calculated from the GPS receiver and inertial measurement device matches the absolute coordinate system detected by the sensing imaging means and pre-registered ground latitude and longitude information, and when the direction of travel 600 and the direction of the front and rear axles 610 also match, the system automatically changes to a driving mode that returns the rotation speed of all four wheels to the same rotation speed, thereby preventing malfunctions of the robotic work machine 100 or problems such as it deviating from the driving line again.

[0110] Furthermore, the present invention is not limited to four-wheel drive or four-wheel steering. As in the fourth invention, it can also be used with two-wheel drive or two-wheel steering. Although positioning during movement before work is difficult, positional deviations can be anticipated by comparing the coordinate system of the vehicle's position calculated from the GPS receiver and inertial measurement device with the position of the coordinate system detected by the sensing imaging means and pre-registered ground latitude and longitude information.

[0111] While driving with this alignment position as a reference, the system uses two-wheel steering to correct for positional misalignment until the coordinate system of the vehicle's position, calculated from the GPS receiver and inertial measurement device, matches the coordinate system detected by the sensing imaging device. Although this is not a control system that corrects for positional misalignment before the operation, the system reduces the driving speed and performs alignment control until the positional misalignment is corrected, allowing for more accurate alignment control than conventional technologies.

[0112] The system is designed to prevent the vehicle's speed from increasing beyond a predetermined speed, and then increases to the set speed only when the direction of travel (600) aligns with the direction of the front and rear axles (610). This allows for positional misalignment compensation, taking advantage of the characteristics of two-wheel steering. [Explanation of Symbols]

[0113] 100 robotic work machines 120 Low-Voltage Battery 130 High-voltage main battery 140 Electric Motors 141 Outside fan 150 HST 160 BMS and inverter 180 Control Unit 190 Running axles 200 Hydraulic pump 210 Air Compressor 220 Work equipment 310 GPS receiver 320 Inertial Measurement Unit (IMU) 410 Imaging means A 550 Regenerative Motor 560 Front left wheel 570 Front right 580 rear wheel left 590 rear wheel right 600 Direction of travel 601 1st reference point A 602 2nd reference point B 610 Front and rear axles

Claims

1. A work machine equipped with a four-wheel drive and four-wheel steering drive unit, which automatically corrects positional discrepancies between the position on a pre-set travel line (600) and the vehicle's position calculated by a GPS receiver and an inertial measurement device, by setting the rotation speed of one or two of the four wheels to a different rotation speed from the other wheels, causing movement accompanied by slippage between the wheel and the ground contact area, thereby aligning the front and rear axles (610) with the direction of travel (600).

2. The work machine according to claim 1, wherein, after correcting the positional misalignment, if the direction of travel (600) and the front and rear axles (610) exceed predetermined values ​​and control is performed to align the directions, the rotation speed of one or two of the four wheels is set to a different rotation speed from the rotation speed of the other wheels, and while the wheels and the ground contact area slip, four-wheel steering is performed while slipping movement is carried out, and when the direction of travel (600) and the front and rear axles (610) fall within predetermined values, directional control is automatically performed to return the rotation speeds of the four wheels to the same rotation speed.

3. The coordinate system of the vehicle's position calculated from the GPS receiver and inertial measurement device, and the coordinate system detected from the sensing imaging means and pre-registered ground latitude and longitude information are matched based on the equations of motion using the coordinate transformation method of the rotational system. While driving with this aligned position as a reference, the rotation speed of one or two of the four wheels is set to be different from that of the other wheels, and four-wheel steering is performed while the wheels and the contact surface slip. The work machine according to claim 1, which matches the coordinate system of the vehicle's position calculated from a GPS receiver and an inertial measuring device with the position of the coordinate system detected by a sensing imaging means, and after matching the direction of travel (600) and the direction of the front and rear axles (610), automatically changes to a driving mode in which the rotation speed of all four wheels returns to the same rotation speed.

4. The coordinate system of the vehicle's position calculated from the GPS receiver and inertial measurement device, and the coordinate system detected from the sensing imaging means and pre-registered ground latitude and longitude information, are matched based on the equations of motion using the coordinate transformation method of the rotational system. The work machine according to claim 1, which, while traveling based on the aligned position, uses two-wheel steering to prevent the travel speed from increasing above a predetermined speed until the coordinate system of the vehicle's position calculated from the GPS receiver and inertial measuring device matches the position of the coordinate system detected by the sensing imaging means, and increases to the set speed when the direction of travel (600) and the direction of the front and rear axles (610) match.

5. A low-voltage battery (120) is positioned at the front of the aircraft, and a high-voltage main battery (130) and an electric motor (140) are arranged in parallel in the front-to-rear direction behind it. The work machine according to claim 1, wherein an HST (Hydraulic Continuously Variable Transmission) (150) is provided on the rear side of the vehicle body of the electric motor (140), power is input from the electric motor (140), and power is distributed from the output shaft of the HST (150) to the axle (190) of the drive system and the hydraulic pump (200), and a regenerative motor (550) is provided to regenerate the surplus power of the HST (150), and the regenerative motor (550) charges the low voltage battery (120).

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