Work vehicle and work vehicle system

Abstract

A work vehicle 10 includes: a vehicle body 11; a plurality of wheels 12 positioned on both the left and right sides of the vehicle body 11; and a support mechanism 13 capable of changing the distance between the ground contact surface of the wheels 12 and the vehicle body 11. The work vehicle 10 acquires road surface information R on the basis of movement of the support mechanism 13 in a state where the wheels 12 are in contact with the road surface.

Description

Work vehicles and work vehicle systems

[0001] This application claims priority from Japanese Patent Application No. 2024-103502, filed on June 27, 2024, and incorporates by reference the entire contents of said Japanese application.

[0002] Patent Document 1 discloses a work vehicle that travels on uneven road surfaces (uneven terrain). The work vehicle has a vehicle body, four wheels, and four support mechanisms that support the wheels relative to the vehicle body. The support mechanisms have articulating link mechanisms that are operable to change the position of the wheels. The support mechanisms are articulated by actuators.

[0003] Japanese Patent Application Laid-Open No. 2020-1440

[0004] The work vehicle has a vehicle body, multiple wheels located on both the left and right sides of the vehicle body, and a support mechanism that can change the distance between the contact surface of the wheels and the vehicle body, and acquires road surface information based on the movement of the support mechanism when the wheels are in contact with the road surface.

[0005] The work vehicle system includes the work vehicle and an external device capable of communicating with the work vehicle. The external device acquires road surface information relating to the road surface position from the work vehicle, and generates map information showing the shape of the road surface based on the road surface information and position information of the work vehicle.

[0006] FIG. 1 is a side view of the work vehicle. FIG. 2 is a plan view of the work vehicle shown in FIG. 1. FIG. 3 is an explanatory diagram of a support mechanism at the right front. FIG. 4 is a control block diagram of the work vehicle. FIG. 5 is an explanatory diagram showing how the work vehicle travels. FIG. 6 is an explanatory diagram showing how the work vehicle travels. FIG. 7 is an explanatory diagram showing how the work vehicle travels. FIG. 8 is an explanatory diagram showing how the work vehicle travels. FIG. 9 is an explanatory diagram of the work vehicle traveling on a road surface with puddles. FIG. 10 is an explanatory diagram of the work vehicle traveling through grass.

[0007] <Problem to be solved> If a work vehicle has an external sensor such as a camera, it can detect the unevenness of the road surface and travel in accordance with the road surface. However, when the work vehicle travels on a road with puddles or through a grassy area, for example, it may be impossible to detect the unevenness of the road surface using a camera.

[0008] If it were possible to acquire road surface information relating to road surface positions, such as the unevenness of the road surface, without using external sensors such as cameras, it would be possible to improve the driving performance of a work vehicle and generate information (map information) showing the unevenness of the road surface. Therefore, the present disclosure provides a work vehicle that is capable of acquiring road surface information without using external sensors such as cameras, and a work vehicle system that includes such a work vehicle.

[0009] <Effects> According to the work vehicle and work vehicle system of the present disclosure, it is possible to acquire road surface information relating to the road surface position without using external sensors such as cameras.

[0010] <Outline of Embodiments of the Present Invention> The following is a list and description of outlines of embodiments of the present invention. (1) A work vehicle according to an embodiment has a vehicle body, a plurality of wheels located on both the left and right sides of the vehicle body, and a support mechanism that can change the distance between the ground contact surfaces of the wheels and the vehicle body, and acquires road surface information based on the movement of the support mechanism while the wheels are in contact with the road surface. The work vehicle acquires road surface information while traveling with the wheels in contact with the road surface. The work vehicle is able to acquire road surface information without using an external sensor such as a camera. Based on the road surface information, for example, it is possible to generate information (map information) that indicates the uneven shape of the road surface from road surface information related to the road surface position.

[0011] (2) The work vehicle of (1) has a detection device for detecting the movement of the support mechanism, and acquires the movement of the support mechanism based on a detection signal from the detection device. Road surface information is acquired based on the detection signal from the detection device when the wheels are in contact with the road surface.

[0012] (3) In the work vehicle of (2), the support mechanism has an operating unit to which the wheels are attached and which is operable to change the position of the wheels, and an actuator that drives the operating unit. The detection device detects the operation of the actuator. The operation of the actuator corresponds to the movement of the support mechanism. The detection device detects the operation of the actuator, thereby detecting the movement of the support mechanism.

[0013] (4) In the work vehicle of (2), the support mechanism has an operating unit to which the wheels are attached and which is operable to change the position of the wheels. The detection device detects the operation of the operating unit. The operation of the operating unit to which the wheels are attached corresponds to the movement of the support mechanism. The detection device detects the operation of the operating unit, thereby detecting the movement of the support mechanism.

[0014] (5) In any one of the work vehicles described in (1) to (4), the support mechanism is operated so that all of the wheels are in contact with the road surface while the work vehicle is traveling. In this case, the wheels trace (follow) the unevenness of the road surface while the work vehicle is traveling. For example, by obtaining information about the position of the wheels relative to the vehicle body based on the movement of the support mechanism and obtaining this as road surface information, it becomes possible to generate information indicating the uneven shape of the road surface, for example.

[0015] (6) In the work vehicle of (5), when the wheel goes over a bump on the road surface, the support mechanism operates so that the wheel going over the bump approaches the vehicle body. With this configuration, for example, the relative position of the vehicle body and the wheel coming over the bump while in contact with the bump on the road surface can be obtained based on the movement of the support mechanism. Road surface information relating to the road surface position can be obtained based on the relative position.

[0016] (7) Any one of the work vehicles described in (1) to (6) obtains the road surface information based on information relating to the position of the wheels in contact with the road surface. The work vehicle travels with the wheels tracing (following) the unevenness of the road surface. The work vehicle obtains information relating to the position of the wheels relative to the vehicle body, and this information can be used as road surface information relating to the road surface position.

[0017] (8) The work vehicle according to any one of (1) to (7) above has a control device that performs attitude control to maintain the vehicle body in a predetermined attitude, and acquires the road surface information based on the movement of the support mechanism while the wheels are in contact with the road surface while the attitude control is being performed. With this configuration, the work vehicle travels while maintaining the vehicle body in a predetermined attitude (for example, a horizontal attitude with the top surface of the work vehicle horizontal). While traveling, the work vehicle acquires information on the position of the wheels relative to the vehicle body, for example, and can generate information indicating the uneven shape of the road surface.

[0018] (9) The work vehicle of (8) acquires the road surface information based on the relative positions of the vehicle body maintained in the predetermined posture and the wheels that are in contact with the road surface. By acquiring information on the positions of the wheels relative to the vehicle body maintained in the predetermined posture, the work vehicle can generate information that indicates the uneven shape of the road surface.

[0019] (10) Any one of the work vehicles (1) to (9) obtains, as the road surface information, information on a change in the position of a wheel in contact with the road surface. When a wheel in contact with the road surface sinks, by obtaining information on the change in the position of the wheel, information on the degree of softness of the road surface can be obtained, for example.

[0020] (11) Any one of the work vehicles (1) to (10) has an accelerometer capable of detecting acceleration in the height direction, and acquires the road surface information based on the movement of the support mechanism when the wheels are in contact with the road surface and the detection signal of the accelerometer. It becomes possible to acquire information showing the uneven shape of the road surface, and further, when the wheels in contact with the road surface sink, information on the degree of softness of the road surface can be obtained based on the detection signal of the accelerometer.

[0021] (12) The work vehicle according to any one of (1) to (11) has a position acquisition unit that acquires position information of the travel position, and generates map information showing the shape of the road surface based on the road surface information and the position information. This makes it possible to generate map information that associates each position on the road surface while the work vehicle is traveling with the road surface shape at each position.

[0022] (13) The work vehicle according to any one of (1) to (12) has a communicator that transmits the road surface information to an external device. When the external device receives the road surface information transmitted from the work vehicle, it is able to generate map information that associates the position of the work vehicle with the road surface shape at that position.

[0023] (14) The work vehicle according to any one of (1) to (13) has an external sensor that acquires information about the surrounding environment, and acquires additional road surface information based on the road surface information and the external information based on the detection signal of the external sensor. For example, when the work vehicle travels on a road surface with a puddle and the external sensor detects the water surface of the puddle, it is possible to acquire, for example, the depth of the puddle as additional road surface information. When the work vehicle travels through a bush and the external sensor detects the approximate top surface of the bush, it is possible to acquire, for example, the height of the bush as additional road surface information.

[0024] (15) An embodiment of a work vehicle system includes a work vehicle according to any one of (1) to (14) above, and an external device capable of communicating with the work vehicle. The external device acquires road surface information relating to road surface position from the work vehicle, and generates map information indicating the shape of the road surface based on the road surface information and position information of the work vehicle. When the external device receives the road surface information transmitted from the work vehicle, it is able to generate map information that associates the position of the work vehicle with the road surface shape at that position. The position information of the work vehicle may be acquired from the work vehicle via communication, or may be acquired by the external device.

[0025] <Details of the Embodiments> Hereinafter, details of the embodiments of the present invention will be described with reference to the drawings. Note that at least some of the embodiments described below may be combined in any manner.

[0026] [Overall Configuration of Work Vehicle] Figure 1 is a side view of the work vehicle. Figure 2 is a plan view of the work vehicle shown in Figure 1. The work vehicle 10 shown in Figures 1 and 2 is a vehicle that can travel on uneven road surfaces (uneven terrain).

[0027] In the following description, the direction of the arrow FW shown in the figure is the "front" of the work vehicle 10, which is the straight-ahead direction of the work vehicle 10. The direction of the arrow BK is the "rear" of the work vehicle 10, which is opposite to the straight-ahead direction. The direction of the arrow RH is the "right" of the work vehicle 10 moving straight, and the direction of the arrow LH is the "left" of the work vehicle 10 moving straight. The direction of the arrow DW is the "down" of the work vehicle 10, which is the road surface side, and the direction of the arrow UP is the "up" of the work vehicle 10, which is the opposite side to the road surface.

[0028] The work vehicle 10 has a vehicle body 11, a plurality of wheels 12, a plurality of support mechanisms 13, and a control device 17. The work vehicle 10 of this embodiment has four wheels 12 and the same number (four) of support mechanisms 13 as the wheels 12. The support mechanisms 13 connect the vehicle body 11 and the wheels 12. The wheels 12 are located at the front and rear of both the left and right sides of the vehicle body 11.

[0029] The vehicle body 11 has a frame 21. The vehicle body 11 has a loading section 22 on top of the frame 21, on which cargo can be loaded. The loading section 22 has a flat loading surface 221 on its upper surface. The loading surface 221 has a substantially rectangular shape in a plan view (see FIG. 2 ). The loading surface 221 is provided so as to extend in the left-right and front-rear directions. The cargo to be loaded is, for example, agricultural equipment, agricultural materials such as fertilizer and chemicals, harvested crops, harvest baskets, or pallets on which these are placed.

[0030] The support mechanisms 13 are located at the left front, right front, left rear, and right rear of the vehicle body 11. The support mechanisms 13 are attached to the vehicle body 11 (part of the frame 21) and support the wheels 12 so that their positions can be changed relative to the vehicle body 11. The support mechanisms 13 have articulating link mechanisms 30 as operating parts that are operable to change the positions of the wheels 12. The wheels 12 are attached to the articulating link mechanisms 30. The support mechanisms 13 have actuators 14 that drive the articulating link mechanisms 30.

[0031] The actuator 14 operates the articulating link mechanism 30 to change the attitude of the articulating link mechanism 30. The actuator 14 is a fluid cylinder, and in this embodiment has a first hydraulic cylinder 36 and a second hydraulic cylinder 37. The specific configuration of the support mechanism 13 will be described later. The work vehicle 10 has multiple hydraulic motors 15. The hydraulic motors 15 are provided at the ends of the articulating link mechanism 30 together with the wheels 12. The hydraulic motors 15 are travel actuators that drive the wheels 12 to rotate.

[0032] The wheels 12 are driven wheels that are rotated by hydraulic motors 15. The rotation of the wheels 12 causes the work vehicle 10 to move. The work vehicle 10 has a plurality of training wheels 16. The training wheels 16 are attached midway along the articulating link mechanism 30. The training wheels 16 are attached to the connecting portions (joint portions) of a first link 31 and a second link 32, which will be described later and which make up the articulating link mechanism 30. The training wheels 16 are driven wheels that can rotate freely.

[0033] The work vehicle 10 has a hydraulic unit (hydraulic pressure supply source) 51, a battery 52, and an engine 53. The hydraulic unit 51 supplies hydraulic oil to the hydraulic motor 15, the first hydraulic cylinder 36, the second hydraulic cylinder 37, and a swing hydraulic cylinder 38 (described later). The hydraulic unit 51 has a hydraulic pump 54 driven by the engine 53, multiple hydraulic control valves 55, and a hydraulic oil tank 56.

[0034] A hydraulic control valve 55 is connected to each of the hydraulic motor 15 and the hydraulic cylinders 36, 37, and 38. The hydraulic control valve 55 is an electromagnetic valve and has the function of supplying, stopping the supply, and adjusting the supply flow rate of hydraulic oil from the hydraulic pump 54. The control device 17 controls the hydraulic control valve 55 to adjust the supply state (supply amount) of hydraulic oil from the hydraulic unit 51. In other words, the control device 17 controls the operation of the hydraulic motor 15 and the hydraulic cylinders 36, 37, and 38.

[0035] The hydraulic unit 51, battery 52, engine 53, and control device 17 are mounted on the vehicle body 11 (frame 21), and in this embodiment (see FIG. 1 ), are located below the loading section 22. The battery 52 supplies power to the control device 17, hydraulic unit 51, and multiple sensors, which will be described later. The work vehicle 10 has an operating handle 18 that is gripped by the worker. The operating handle 18 is attached to the frame 21.

[0036] [Support Mechanisms 13] The left front support mechanism 13 and the right front support mechanism 13 are "front support mechanisms 13f" located at the front of the vehicle body 11. The left rear support mechanism 13 and the right rear support mechanism 13 are "rear support mechanisms 13b" located at the rear of the vehicle body 11. The front support mechanisms 13f and rear support mechanisms 13b are attached in different directions on the left and right sides of the work vehicle 10, but have the same configuration. The front support mechanisms 13f and rear support mechanisms 13b are collectively referred to as "support mechanisms 13," and the specific configuration of the support mechanisms 13 will be described below.

[0037] The support mechanism 13 supports the wheels 12 so that they can be individually raised and lowered relative to the vehicle body 11. To this end, the support mechanism 13 has a bending link mechanism 30. Figure 3 is an explanatory diagram of the right front support mechanism 13 (front support mechanism 13f). The bending link mechanism 30 has a first link 31 and a second link 32. Each of the first link 31 and the second link 32 is a linear member.

[0038] A fixed bracket 23 is fixed to a part of the frame 21 of the vehicle body 11. A first end 311 of the first link 31, which faces the frame 21, is supported by the fixed bracket 23 so as to be swingable about a first horizontal axis X1 in the left-right direction. A first end 321 of the second link 32 is supported by a second end 312 of the first link 31 so as to be swingable about a second horizontal axis X2 in the left-right direction. A support bracket 33 is attached to a second end 322, which is the tip side of the second link 32. The wheel 12 is supported by the support bracket 33.

[0039] A set of actuators 14 is provided for one articulating link mechanism 30 having a first link 31 and a second link 32. Each set of actuators 14 has one first hydraulic cylinder 36 and one second hydraulic cylinder 37. The first hydraulic cylinder 36 extends and retracts to swing the first link 31 around the first horizontal axis X1. The first hydraulic cylinder 36 changes the swinging posture of the first link 31 relative to the vehicle body 11. The second hydraulic cylinder 37 extends and retracts to swing the second link 32 around the second horizontal axis X2. The second hydraulic cylinder 37 changes the swinging posture of the second link 32 relative to the first link 31.

[0040] The hydraulic control valve 55 connected to the first hydraulic cylinder 36 and the hydraulic control valve 55 connected to the second hydraulic cylinder 37 are separate valves (see FIG. 4), and the first hydraulic cylinder 36 and the second hydraulic cylinder 37 operate to extend and retract independently. FIG. 4 is a control block diagram of the work vehicle 10. The extension and retraction operations of the first hydraulic cylinder 36 and the second hydraulic cylinder 37 cause the articulating link mechanism 30 to bend and extend.

[0041] 3, for example, when the first hydraulic cylinder 36 extends and retracts while the second hydraulic cylinder 37 is stopped, the first link 31, the second link 32, and the wheel 12 swing together around the first horizontal axis X1 while maintaining a constant relative positional relationship. When the second hydraulic cylinder 37 extends and retracts while the first hydraulic cylinder 36 is stopped, the second link 32 and the wheel 12 swing together around the second horizontal axis X2 while maintaining a constant attitude of the first link 31 relative to the vehicle body 11.

[0042] A support bracket 33 that supports the wheel 12 is attached to the second link 32. The hydraulic motor 15 is mounted on the support bracket 33. The support bracket 33 is attached to the second end 322 of the second link 32 so as to be able to swing about the vertical axis Y in the up-down direction. The work vehicle 10 has a hydraulic cylinder 38 for swinging (hereinafter referred to as the swing cylinder 38) for changing the rolling direction of the wheel 12. The swing cylinder 38 is attached between a part of the second link 32 and the support bracket 33. When the swing cylinder 38 extends and retracts, the support bracket 33 and the wheel 12 swing about the vertical axis Y. The traveling direction of the work vehicle 10 is changed by the operation of the swing cylinder 38.

[0043] As described above, the work vehicle 10 of this embodiment has four support mechanisms 13, and each support mechanism 13 is provided with a set of actuators 14. The set of actuators 14 provided on one support mechanism 13 and the other set of actuators 14 provided on another support mechanism 13 are separate actuators, and each actuator 14 operates independently. This allows the four wheels 12 to move individually relative to the vehicle body 11. Furthermore, it is possible to vary the positions of the four wheels 12 relative to the vehicle body 11. The support mechanisms 13 allow the distance between the ground contact surfaces of the wheels 12 and the vehicle body 11 to be changed. This distance is, for example, the vertical distance between the lower surfaces (ground contact surfaces) of the wheels 12 and the loading surface 221 (the upper end of the loading section 22) of the vehicle body 11 (for example, distance L shown in FIGS. 6 to 8 ).

[0044] [Sensors] The vehicle 10 has multiple sensors. Figure 4 is a control block diagram of the vehicle 10, and mainly shows the configuration related to the left front support mechanism 13 (front support mechanism 13f). Although the configuration of the other support mechanisms 13 is omitted in Figure 4, they have the same configuration as the left front support mechanism 13.

[0045] A head-side pressure sensor S1 and a rod-side pressure sensor S2 are connected to the second hydraulic cylinder 37. The head-side pressure sensor S1 detects the internal pressure of an oil chamber on the head side of the second hydraulic cylinder 37. The rod-side pressure sensor S2 detects the internal pressure of an oil chamber on the rod side of the second hydraulic cylinder 37. The control device 17 acquires detection signals from the sensors S1 and S2.

[0046] A stroke sensor S3 that detects the amount of extension / contraction is provided in each of the first hydraulic cylinder 36 and the second hydraulic cylinder 37. The amount of extension / contraction of each of the first hydraulic cylinder 36 and the second hydraulic cylinder 37 is related to the swing position of each of the first link 31 and the second link 32. Therefore, the detection value of the stroke sensor S3 is correlated with the swing position of each of the first link 31 and the second link 32. The detection value of the stroke sensor S3 uniquely determines the position of the wheel 12 relative to the vehicle body 11. The control device 17 is able to acquire the detection signal of the stroke sensor S3 and detect the position of the wheel 12.

[0047] As described above, the work vehicle 10 has a head-side pressure sensor S1, a rod-side pressure sensor S2, and a stroke sensor S3 as detection devices for detecting the movement of the support mechanism 13 (articulated link mechanism 30). The operation of the actuator 14, which has the first hydraulic cylinder 36 and the second hydraulic cylinder 37, is detected by the stroke sensor S3 (detection device). The control device 17 can obtain the movement of the support mechanism 13 based on the detection signal of the stroke sensor S3.

[0048] The vehicle body 11 is provided with an inclination sensor S4 that detects the inclination state of the vehicle body 11. The inclination sensor S4 is configured using an inertial measurement unit (IMU), which is a well-known configuration. The IMU of this embodiment has a triaxial acceleration sensor and a gyro sensor, and detects changes in the attitude of the vehicle body 11, specifically, tilt in the front-rear and left-right directions. The control device 17 acquires the detection signal of the inclination sensor S4.

[0049] A rotation sensor S5 that detects the rotation speed of the wheel 12 is provided near the wheel 12. The control device 17 acquires a detection signal from the rotation sensor S5. Based on the detection value of the rotation sensor S5, the supply of hydraulic oil to the hydraulic motor 15 is controlled so that the rotation speed of the wheel 12 becomes a target value.

[0050] The vehicle 10 has a pressure sensor S6 that detects the pressure of hydraulic oil supplied to the hydraulic motor 15. The control device 17 acquires the detection signal from the pressure sensor S6. Based on the hydraulic oil pressure detected by the pressure sensor S6, the supply (pressure) of hydraulic oil to the hydraulic motor 15 is controlled so that the drive torque of the wheels 12 becomes a target value. Each of the four swing cylinders 38 is provided with a stroke sensor S7 that can detect the amount of extension and contraction. The control device 17 acquires the detection signal from the stroke sensor S7. This controls the traveling direction of the vehicle 10.

[0051] [Control device 17] The control device 17 has an ECU 171 (Electronic Control Unit) that functions as a main control unit that controls the operation of the work vehicle 10. The ECU 171 has a microcomputer and executes various controls according to control programs. The ECU 171 has a non-volatile memory that stores programs corresponding to the functional units that execute the various controls, and a CPU that executes the programs. The functions (controls) of each functional unit are realized by the CPU executing the programs.

[0052] The ECU 171 has an attitude control unit 172 as one of the functional units. The attitude control unit 172 executes horizontal control and center of gravity position control. The control device 17 (ECU 171) controls the actuator 14 to perform attitude control to maintain the vehicle body 11 in a predetermined attitude while traveling. Note that, in the following, the "predetermined attitude" will be described as an attitude in which the loading section 22 (loading surface 221) of the vehicle body 11 is horizontal (horizontal attitude), but it may also be an attitude other than horizontal.

[0053] (Horizontal Control) When the vehicle 10 is traveling, the posture control unit 172 performs horizontal control based on the detection signal from the inclination sensor S4. The horizontal control is a control that operates the left and right front support mechanisms 13f and rear support mechanisms 13b so that the loading unit 22 (loading surface 221) is in a horizontal position. Based on the detection signal from the inclination sensor S4, the posture control unit 172 determines the tilt angles in the front-to-rear direction and the left-to-right direction, with the vehicle body 11 (loading unit 22) in a reference position in which the vehicle body 11 is in a horizontal position. The posture control unit 172 controls the operation of the four first hydraulic cylinders 36 and the four second hydraulic cylinders 37 so that these tilt angles become values ​​corresponding to the horizontal position (i.e., the tilt angles are zero).

[0054] The horizontal control will be further described. The ECU 171 calculates the target actuation amounts of the four first hydraulic cylinders 36 and the four second hydraulic cylinders 37 required to bring the loading unit 22 to a horizontal position, based on the tilt attitude (tilt angle) of the loading unit 22 detected by the tilt sensor S4. The ECU 171 controls the actuation of the four first hydraulic cylinders 36 and the four second hydraulic cylinders 37 so that the actual actuation amounts detected by the stroke sensor S3 become the target actuation amounts.

[0055] (Center of gravity position control) The posture control unit 172 is capable of performing center of gravity position control, which determines the center of gravity position of the vehicle body 11 based on the detection information of the inclination sensor S4 and the stroke sensor S3, and controls the operation of the left and right front support mechanisms 13f and rear support mechanisms 13b so that the center of gravity position is located in the center of the multiple (four) wheels 12 in a planar view.

[0056] The center of gravity position control will be further explained. The tilt state of the vehicle body 11 is detected by the output of the tilt sensor S4. The posture control unit 172 determines the tilt angle in the front-to-rear direction and the left-to-right direction from the horizontal posture of the vehicle body 11 based on the detection signal of the tilt sensor S4. The state of the support mechanism 13 (the angle of the first link 31 relative to the vehicle body 11, and the angle of the second link 32 relative to the first link 31) is detected based on the detection results of the extension / contraction amounts of the first hydraulic cylinder 36 and the second hydraulic cylinder 37 detected by the multiple stroke sensors S3.

[0057] As a result, it is possible to obtain by calculation the overall attitude (inclination state) of the vehicle body 11 and the position of the center of gravity of the vehicle body 11 in relation to the ground contact positions of the four wheels 12. The attitude control unit 172 operates the first hydraulic cylinder 36 and the second hydraulic cylinder 37 so that the center of gravity thus obtained becomes the target attitude in which it is located in the center of the multiple (four) wheels 12 in a plan view.

[0058] In this way, center of gravity position control is control that adjusts the pressure (force) supporting the vehicle body 11 so that the center of gravity of the vehicle body 11 converges to the target center of gravity regardless of the unevenness of the road surface. As a variation of center of gravity position control, the attitude control unit 172 does not determine the center of gravity position of the vehicle body 11, but rather determines the ground contact pressure of multiple (four) wheels 12. The ground contact pressure is determined based on detection signals from pressure sensors S1 and S2. In this case, the attitude control unit 172 controls the operation of the support mechanism 13 so that the ground contact pressure of the wheel 12 located lower and the ground contact pressure of the wheel 12 located upper are equal.

[0059] The center of gravity position control makes it possible to generate driving forces in all of the wheels 12 in accordance with the unevenness of the road surface. By executing the horizontal control and center of gravity position control, the posture control unit 172 can operate the support mechanism 13 so that the placement surface 221 is in a horizontal position and so that all of the wheels 12 generate driving forces in accordance with the unevenness of the road surface.

[0060] The attitude control unit 172 controls the attitude of the vehicle 10 (controls the center of gravity position), and the support mechanism 13 operates, allowing the vehicle to travel with all of the four wheels 12 in contact with the road surface (see FIGS. 5 and 6). In other words, the actuator 14 operates the articulating link mechanism 30, allowing the vehicle to travel with all of the four wheels 12 in contact with the road surface. The vehicle 10 of this embodiment travels with all of the wheels 12 tracing (following) the unevenness of the road surface.

[0061] FIG. 5 is an explanatory diagram showing how the vehicle 10 travels while the attitude control unit 172 controls the attitude of the vehicle 10. FIG. 5 shows the state of one vehicle 10 traveling at multiple times. As described above, due to the attitude control by the attitude control unit 172, the vehicle 10 travels with all four wheels 12 in contact with the road surface. During this travel, when the wheels 12 go over a bump Q on the road surface, the support mechanism 13 (articulated link mechanism 30) operates so that the wheels 12 traveling over the bump Q approach the vehicle body 11. In other words, when the wheels 12 go over the bump Q on the road surface, the distance between the contact surface of the wheels 12 traveling over the bump Q and the vehicle body 11 becomes shorter (smaller). Furthermore, the vehicle 10 travels with all four wheels 12 in contact with the road surface without changing the height of the loading unit 22 and with the loading surface 221 horizontal.

[0062] [Obtaining Road Surface Information] The control device 17 of the work vehicle 10 has the function of acquiring road surface information about the road surface on which the vehicle is traveling. The control device 17 acquires road surface information based on the movement of the support mechanism 13 when the wheels 12 are in contact with the road surface. In this embodiment, the movement of the support mechanism 13 is acquired based on detection signals from a detection device including a stroke sensor S3 (see FIG. 4). In other words, road surface information is acquired based on detection signals from the detection device when the wheels 12 are in contact with the road surface. The lower diagram in FIG. 5 shows an example of road surface information R. Below, the road surface information R and the means for acquiring it will be described.

[0063] The control device 17 acquires road surface information R based on information relating to the position of the wheels 12 in contact with the road surface. In this embodiment, the ground contact position of the wheels 12 is used as the position of the wheels 12. As described above, the work vehicle 10 travels with the wheels 12 tracing (following) the unevenness of the road surface. The control device 17 can detect the position of the wheels 12 by acquiring detection signals from the stroke sensors S3 for the first hydraulic cylinder 36 and the second hydraulic cylinder 37.

[0064] Therefore, the control device 17 acquires information about the ground contact position of the wheel 12 relative to the vehicle body 11 based on the detection signal of the stroke sensor S3 (detection device). The control device 17 acquires height information about the ground contact position of the wheel 12 as road surface information R about the road surface position.

[0065] In the case of the work vehicle 10 of this embodiment, the first hydraulic cylinder 36 and the second hydraulic cylinder 37 are controlled so that the wheels 12 are in a ground contact state, and the work vehicle 10 travels with the wheels 12 tracing the unevenness of the road surface. For this reason, the control device 17 acquires information regarding the position (ground contact position) of the wheels 12 relative to the vehicle body 11 based on the detection signal of the stroke sensor S3. By acquiring the ground contact position information as road surface information R, it is possible to generate information indicating the uneven shape of the road surface.

[0066] Note that the support mechanism 13 that is operated to acquire the road surface information R does not have to be all of the front, rear, left, and right support mechanisms 13, but may be just one support mechanism 13. In the configuration shown in Fig. 5, the road surface information R is acquired based on the detection signal of the stroke sensor S3 in one front support mechanism 13f. In the configurations shown in Figs. 5 and 6, the relative positions of the vehicle body 11 and the wheel 12 that is in contact with and going over a protrusion Q on the road surface are obtained based on the detection signal of the stroke sensor S3 in the front support mechanism 13f. Based on this relative position, the road surface information R relating to the road surface position is acquired.

[0067] As shown in Figure 5, the vehicle 10 travels while maintaining the vehicle body 11 in a predetermined attitude (a horizontal attitude with the mounting surface 221 horizontal). While traveling, the vehicle 10 acquires information on the position of the wheels 12 relative to the vehicle body 11 based on the detection signal of the stroke sensor S3, and acquires information indicating the uneven shape of the road surface (road surface information R). In other words, while attitude control is being performed by the attitude control unit 172, the control device 17 acquires road surface information R based on the movement of the support mechanism 13 when the wheels 12 are in contact with the road surface (the detection signal of the stroke sensor S3).

[0068] As described above, the control device 17 acquires road surface information R based on the relative positions of the vehicle body 11, which is maintained in a predetermined position (a horizontal position in the case of FIG. 5), and the wheels 12, which are in contact with the road surface. The relative positions are obtained by calculation from the detection signal of the stroke sensor S3.

[0069] The state in which the wheel 12 is in the reference position (P1 in FIG. 5) is defined as the reference state. The work vehicle 10 starts traveling from this reference state. During this travel, the wheel 12 rolls along the road surface, and the control device 17 constantly acquires the position (height position) of the wheel 12. The control device 17 constantly compares the reference position (P1) with the position of the wheel 12 during travel (for example, P3 in FIG. 5). This comparison makes it possible to determine the position of the road surface (height position of the road surface) when the reference state is used as a reference, i.e., the convex portion Q.

[0070] The vehicle 10 (see FIG. 4) has a position acquisition unit 19 that acquires position information about the traveling position (vehicle position) of the vehicle 10. The position acquisition unit 19 is a positioning device that receives satellite signals transmitted from multiple GNSS satellites and performs positioning based on the satellite 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 (Russia), Galileo (Europe), and BeiDou (China).

[0071] The position acquisition unit 19 has a receiver 19a that receives satellite signals, and a processor (arithmetic processing unit) 19b. The receiver 19a has an antenna that receives signals from GNSS satellites. The processor 19b calculates and determines the position (coordinates) of the vehicle 10 based on the signals received by the antenna. The receiver 19a is provided, for example, on top of the vehicle body 11. Information indicating the position of the vehicle 10 is sent to the control device 17.

[0072] The position acquisition unit 19 acquires the position information every moment while the vehicle 10 is traveling and provides this position information to the control device 17. The control device 17 acquires road surface information R every moment as described above. The control device 17 associates the vehicle position indicated by the position information with the road surface information R at that vehicle position and saves this as map information. In other words, the control device 17 generates map information that associates each position on the road surface during travel with the road surface shape at each position.

[0073] In this way, the control device 17 generates map information indicating the shape of the road surface based on the acquired road surface information R and the position information. In the configuration shown in Fig. 5, the road surface information R is acquired based on the detection signal of the stroke sensor S3 in one front support mechanism 13f. Therefore, the map information generated based on the road surface information R and the acquisition position of the road surface information R becomes information on a map (elevation difference map) along a line in the traveling direction.

[0074] The road surface information R may be acquired based on the detection signals of the stroke sensors S3 in the two front support mechanisms 13f, one on the left and one on the right. In this case, it is possible to generate two-dimensional map information along the road surface in the front-rear and left-right directions. The rear support mechanism 13b may be used to generate the road surface information R, instead of the front support mechanism 13f.

[0075] In this embodiment, the work vehicle 10 travels with all four wheels 12 in contact with the road surface due to the operation of the support mechanism 13. Even when the work vehicle 10 is stopped (temporarily stopped), all four wheels 12 remain in contact with the road surface. As shown in FIGS. 7 and 8 , for example, if the road surface is soft and the wheel 12 in contact with the road surface sinks, the support mechanism 13 to which the sinking wheel 12 is attached extends. Based on the detection signal from the stroke sensor S3 in the support mechanism 13, the control device 17 can obtain, as road surface information R, information regarding the change in position of the wheel 12 in contact with the road surface. In this way, by obtaining information regarding the change in position of the wheel 12 when the wheel 12 in contact with the road surface sinks, the control device 17 can obtain information regarding the degree of softness of the road surface.

[0076] The vehicle 10 has an inertial measurement unit (IMU) as an inclination sensor S4 (see FIG. 4). The inertial measurement unit functions as an accelerometer that can detect acceleration in the vertical direction. When the road surface is soft and the wheels 12 in contact with the road surface sink, the inclination sensor S4 detects a change in the attitude of the vehicle body 11. The control device 17 can acquire road surface information R based on the movement of the support mechanism 13 (detection signal of the stroke sensor S3) when the wheels 12 are in contact with the road surface, and the detection signal of the inclination sensor S4.

[0077] This makes it possible to obtain information indicating the uneven shape of the road surface, and further, when the wheels 12 in contact with the road surface sink, information on the degree of softness of the road surface can be obtained based on the detection signal of the inclination sensor S4. The control device 17 can store the information on the degree of softness of the road surface in association with the map information.

[0078] The vehicle 10 has a communicator 20 that transmits the acquired road surface information R to an external device 80 (see FIG. 4). The communicator 20 transmits information wirelessly to the external device 80. The external device 80 is a device other than the vehicle 10, such as a computer device installed in a control room of a work site where the vehicle 10 travels.

[0079] The communicator 20 may also transmit the acquired position information of the vehicle's 10 travel position (vehicle position) in conjunction with transmitting the road surface information R. In this case, when the external device 80 receives the information transmitted from the vehicle 10, it will be able to generate map information that associates the position of the vehicle 10 with the road surface shape at that position (road surface information R). As described above, the map information may be generated by the vehicle 10 or the external device 80.

[0080] When the vehicle 10 has the communication device 20, a vehicle system S is formed that includes the vehicle 10 and an external device 80 that is capable of communicating with the vehicle 10. The external device 80 acquires road surface information R from the vehicle 10, and generates map information that shows the shape of the road surface based on the road surface information R and the position information of the vehicle 10. The position information of the vehicle 10 may be acquired from the vehicle 10 by communication, or may be acquired by the external device 80.

[0081] Figure 9 is an explanatory diagram of the vehicle 10 traveling on a road surface with puddles. Figure 10 is an explanatory diagram of the vehicle 10 traveling through a grassy area. The vehicle 10 has an external sensor 90 that acquires information about the surrounding environment. The external sensor 90 is, for example, a camera (CCD camera).

[0082] The control device 17 can use the detection information from the external sensor 90 to obtain, for example, the position of the water surface of a puddle relative to the reference position of the vehicle body 11. The control device 17 can also use the detection information from the external sensor 90 to obtain, for example, the position of the top surface of a patch of grass relative to the reference position of the vehicle body 11. The control device 17 obtains road surface information R relating to the road surface position as described above. Therefore, the control device 17 can obtain the water depth of a puddle based on the information on the position of the water surface of the puddle and the road surface information R, and can also obtain the height of the patch of grass from the road surface based on the information on the position of the top surface of the grass and the road surface information R.

[0083] In this way, the control device 17 acquires additional road surface information, such as the depth of puddles or the height of bushes, based on the external environment information derived from the detection signals of the external environment sensor 90 and the acquired road surface information R. Note that if, for example, only the position of the top surface of a bush is acquired using only the external environment sensor 90 and the position of that top surface is constant, there is a risk that the road surface will be recognized (mistakenly) as being flat. However, the work vehicle 10 of this embodiment acquires not only the position of the top surface of the bush but also the road surface information R, thereby preventing such misrecognition. This makes it possible to extract dangerous areas in the area in which the work vehicle 10 is traveling, enabling more advanced travel control of the work vehicle 10.

[0084] In the embodiment described above, the work vehicle 10 has a stroke sensor S3 provided on each of the first hydraulic cylinder 36 and the second hydraulic cylinder 37. The operation of the first hydraulic cylinder 36 and the second hydraulic cylinder 37 (actuator 14) corresponds to the movement of the support mechanism 13 (articulating link mechanism 30). Therefore, the stroke sensor S3 detects the operation of the first hydraulic cylinder 36 and the second hydraulic cylinder 37 (actuator 14), thereby indirectly detecting the movement of the support mechanism 13 (articulating link mechanism 30). In this way, the control device 17 obtains the movement of the support mechanism 13 (articulating link mechanism 30) based on the detection signal of the stroke sensor S3.

[0085] The movement of the support mechanism 13 (articulating link mechanism 30) may be acquired by a detection device other than the stroke sensor S3 that detects the first hydraulic cylinder 36 and the second hydraulic cylinder 37. Another means for detecting the movement of the support mechanism 13 (articulating link mechanism 30) will be described. The movement of the articulating link mechanism 30 to which the wheels 12 are attached corresponds to the movement of the support mechanism 13. The movement of the support mechanism 13 can be detected by a detection device detecting the movement of the articulating link mechanism 30. The detection device for this purpose is, for example, a sensor (rotation angle sensor) that detects the swing angle of the first link 31 (see FIG. 1 ) and a sensor (rotation angle sensor) that detects the swing angle of the second link 32. In this way, the movement of the articulating link mechanism 30, which is a moving part of the support mechanism 13, may be directly detected by a detection device (rotation angle sensor). The detection device may be a camera (CCD camera) in addition to the sensor (rotation angle sensor) described above. The movement of the articulating link mechanism 30 may be directly detected by the camera.

[0086] [Regarding the Work Vehicle 10] As described above, the work vehicle 10 has the vehicle body 11, multiple wheels 12, and multiple support mechanisms 13. The support mechanisms 13 support the wheels 12 relative to the vehicle body 11 and are operable to change the positions of the wheels 12. The support mechanisms 13 have operating units (articulating link mechanisms 30) to which the wheels 12 are attached and that are operable to change the positions of the wheels 12, and an actuator 14 that drives the operating units. The work vehicle 10 has a stroke sensor S3, a pressure sensor S1, and a pressure sensor S2 as detection devices. Alternatively, the work vehicle 10 may have the rotation angle sensor as the detection device. Alternatively, the work vehicle 10 may have a stroke sensor S3, a pressure sensor S1, a pressure sensor S2, and the rotation angle sensor as detection devices.

[0087] The detection device detects one or both of the operating state (stroke / pressure) of the actuator 14 and the operating position (e.g., the swing angle of the first link 31 and the second link 32) of the operating part (articulated link mechanism 30). The control device 17 acquires road surface information R based on the detection signal of the detection device when the wheel 12 is in contact with the road surface.

[0088] A vehicle 10 having this configuration acquires road surface information R while traveling with the wheels 12 in contact with the road surface. The vehicle 10 is able to acquire road surface information R without using external sensors such as cameras. Based on the road surface information R, it is possible to generate information (map information) showing the uneven shape of the road surface from the road surface information R relating to the road surface position.

[0089] The vehicle body 11 of this embodiment has a loading surface 221 on which an item can be placed. The control device 17 performs attitude control to maintain the vehicle body 11 in a predetermined attitude, by controlling the loading surface 221 to keep it horizontal. In other words, the control device 17 controls the actuator 14 so that the loading surface 221 remains horizontal. With this configuration, the work vehicle 10 travels while maintaining the loading surface 221 of the vehicle body 11 horizontal. While traveling in this manner, the work vehicle 10 acquires information on the position of the wheels 12 relative to the vehicle body 11 based on the detection signal of the detection device, and is able to generate information (road surface information R) that indicates the uneven shape of the road surface. The work vehicle 10 is able to travel using the acquired road surface information R.

[0090] [Others] The above-described embodiments are illustrative in all respects and are not limiting. The scope of the present invention is defined by the claims, not the above-described embodiments, and includes all modifications within the scope of equivalents to the configurations described in the claims.

[0091] REFERENCE SIGNS LIST 10 Work vehicle 11 Vehicle body 12 Wheel 13 Support mechanism 14 Actuator 17 Control device 19 Position acquisition unit 20 Communication device 30 Bending link mechanism (operating unit) 80 External device 90 External sensor R Road surface information S3 Stroke sensor (detection device) S4 Tilt sensor (accelerometer)

Claims

1. A work vehicle having a vehicle body, a plurality of wheels located on both the left and right sides of the vehicle body, and a support mechanism that can change the distance between the contact surfaces of the wheels and the vehicle body, and which acquires road surface information based on the movement of the support mechanism when the wheels are in contact with the road surface.

2. The work vehicle according to claim 1, further comprising a detection device for detecting the movement of the support mechanism, and the movement of the support mechanism is acquired based on a detection signal from the detection device.

3. A work vehicle as described in claim 2, wherein the support mechanism has an operating unit to which the wheel is attached and which is operable to change the position of the wheel, and an actuator that drives the operating unit, and the detection device detects the operation of the actuator.

4. The work vehicle according to claim 2, wherein the support mechanism has an operating part to which the wheel is attached and which is operable to change the position of the wheel, and the detection device detects the operation of the operating part.

5. A work vehicle as set forth in any one of claims 1 to 4, wherein the support mechanism is operated so that all of the plurality of wheels are in contact with the road surface while the work vehicle runs.

6. A work vehicle according to claim 5, wherein, when the wheel goes over a bump on the road surface, the support mechanism operates so that the wheel going over the bump approaches the vehicle body.

7. A work vehicle according to any one of claims 1 to 6, wherein the road surface information is acquired based on information relating to the position of the wheels in contact with the road surface.

8. A work vehicle as described in any one of claims 1 to 7, having a control device that performs attitude control to maintain the vehicle body in a predetermined attitude, and acquiring the road surface information based on the movement of the support mechanism when the wheels are in contact with the road surface while the attitude control is being performed.

9. The work vehicle according to claim 8, wherein the road surface information is acquired based on the relative positions of the vehicle body maintained in the predetermined attitude and the wheels in contact with the road surface.

10. A work vehicle according to any one of claims 1 to 9, wherein the road surface information obtained is information relating to changes in the position of wheels in contact with the road surface.

11. A work vehicle as described in any one of claims 1 to 10, having an accelerometer capable of detecting acceleration in the vertical direction, and acquiring road surface information based on the movement of the support mechanism when the wheels are in contact with the road surface and the detection signal of the accelerometer.

12. A work vehicle as described in any one of claims 1 to 11, having a position acquisition unit that acquires position information of the traveling position, and generates map information showing the shape of the road surface based on the road surface information and the position information.

13. A work vehicle according to any one of claims 1 to 12, further comprising a communication device for transmitting the road surface information to an external device.

14. A work vehicle as described in any one of claims 1 to 13, having an external sensor that acquires information about the surrounding environment, and acquiring additional road surface information based on the external information based on the detection signal of the external sensor and the road surface information.

15. A work vehicle system comprising a work vehicle as defined in any one of claims 1 to 14 and an external device capable of communicating with the work vehicle, wherein the external device acquires road surface information relating to road surface position from the work vehicle, and generates map information showing the shape of the road surface based on the road surface information and position information of the work vehicle.

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