Wheel loader

Abstract

To provide a wheel loader movable to a loading position with a limited traveling distance, by autonomous operation.SOLUTION: A wheel loader comprises a vehicle body with a front body and a rear body bendably connected, a work device having a lift arm and a bucket, a traveling device for making the vehicle body travel, a steering device for steering by varying a bent angle by bending the vehicle body, and a control device controlling the operation of the traveling device and the steering device. The control device calculates a relative position of a loading object in front of the vehicle body and the vehicle body, and on the basis of shape data of the loading object stored in a memory device and the relative position calculated, sets a via-point at a location farther away from the loading object than a distance between a center between front wheels, which is the center of the pair of right-left front wheels, and a tip of the bucket, to make the center between the front wheels coincide with the set via-point, by controlling the operation of the traveling device and the steering device.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to a wheel loader capable of traveling automatically. [Background technology]

[0002] There is known an articulated work vehicle, an articulated wheel loader, which has a vehicle body with a flexibly connected front body and a rear body and a working implement attached to the vehicle body. The wheel loader excavates earth and sand using the working implement, transports the excavated material to a loading position in front of a loading object such as a hopper, and then discharges the excavated material into the top opening of the hopper. As the wheel loader moves to the loading position, it is necessary to control the operation of each part of the wheel loader so that the working implement reaches the loading position without coming into contact with the loading object.

[0003] Patent Document 1 proposes a control device that aims to achieve smooth autonomous driving while maintaining the driving accuracy of an articulated work vehicle (vibration roller). Patent Document 1 describes an autonomous driving control device that "outputs a control signal to correct the traveling direction of the construction machine so that it approaches the traveling reference line when the distance from the traveling reference line to the construction machine is greater than a predetermined first threshold, and outputs a control signal to make the traveling direction of the construction machine parallel to the traveling reference line when the distance from the traveling reference line to the construction machine becomes smaller than a second threshold that is the same as or smaller than the first threshold." [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-204089 Summary of the Invention [Problem to be solved by the invention]

[0005] Wheel loaders may operate in narrow work sites. In narrow work sites, the space and travel distance for changing direction and correcting the direction of the wheel loader are limited, and changing direction and correcting direction reduce work efficiency. Furthermore, if a misalignment occurs between the vehicle body and the object being loaded, a steering operation is required to correct the direction, increasing the risk of contact between the vehicle body and the object being loaded. Therefore, it is desirable to be able to move the vehicle body toward the object being loaded without correcting the direction of the vehicle body as much as possible. There is a demand for a wheel loader that can move the vehicle body to an appropriate loading position within a limited travel distance, such as in a narrow work site. Patent Document 1 discloses a control method for correcting lateral deviation of the vehicle body from a travel reference line when performing compaction using a vibratory roller, but does not disclose a control method for moving the vehicle body to a predetermined position while avoiding contact with an object, such as an object being loaded.

[0006] An object of the present invention is to provide a wheel loader that can move to a loading position within a limited distance by autonomous driving. [Means for solving the problem]

[0007] The present invention 1st The wheel loader according to the present invention comprises a vehicle body having a front body having a pair of left and right front wheels and a rear body having a pair of left and right rear wheels which are flexibly connected to one another, a working device having a lift arm rotatably attached to the front body and a bucket rotatably attached to the lift arm, a traveling device that causes the vehicle body to travel, a steering device that changes the bending angle by bending the vehicle body to steer, and a control device that controls the operation of the traveling device and the steering device, and the wheel loader performs the work of loading excavated material excavated by the working device onto a loading object, and a storage device that stores shape data of the loading object. a bending angle sensor that detects the bending angle of the vehicle body; and an alarm device.The control device calculates the relative position between the vehicle body and the object to be loaded that is located in front of the vehicle body, and determines the distance between the front wheel center, which is the center between the pair of left and right front wheels, and the bucket from the object to be loaded based on the shape data of the object to be loaded stored in the storage device and the calculated relative position. Center of width A position farther away than the distance between the tip On a virtual straight line extending from the loading object and controls the operation of the traveling device and the steering device to align the center between the front wheels with the set waypoint. After aligning the center between the front wheels with the set waypoint, the operation of the steering device is controlled with the traveling device stopped to make the front body align with the imaginary straight line, and after making the front body align with the imaginary straight line, the operation of the traveling device and the steering device is controlled to make the front body move straight along the imaginary straight line, and the control device determines whether or not an approachable condition to the loading object is met based on the bending angle of the vehicle body detected by the bending angle sensor, the shape data of the loading object stored in the storage device, and the calculated relative position of the loading object and the vehicle body, and when the approachable condition is met When the approach condition is established, the steering device and the traveling device are operated so as to align the center of the front wheels with the waypoint, and when the approach condition is not established, the notification device is controlled to cause the notification device to notify that the approach condition is not established, and the approach condition includes that it is possible to align the center of the front wheels with the waypoint by operating the steering device and traveling forward by the traveling device, and that after the center of the front wheels is align with the waypoint, the orientation of the front body can be made to follow the imaginary straight line by operating the steering device while stopping the traveling device. A wheel loader according to a second aspect of the present invention comprises a vehicle body having a front body having a pair of left and right front wheels and a rear body having a pair of left and right rear wheels which are flexibly connected, a working device having a lift arm rotatably attached to the front body and a bucket rotatably attached to the lift arm, a traveling device which causes the vehicle body to travel, a steering device which changes the bending angle by bending the vehicle body for steering, and a control device which controls the operation of the traveling device and the steering device, and the wheel loader performs work of loading material excavated by the working device onto a loading object, the wheel loader also comprising a storage device which stores shape data of the loading object, the control device calculates the relative position between the vehicle body and the loading object which is located in front of the vehicle body, and based on the shape data of the loading object stored in the storage device and the calculated relative position, sets a waypoint on an imaginary line extending from the loading object at a position further from the loading object than the distance between the center between the front wheels which is the center between the pair of left and right front wheels and the center tip of the bucket in the width direction, and controls the operation of the traveling device and the steering device and aligns the center between the front wheels with the set waypoint, and after aligning the center between the front wheels with the set waypoint, controls the operation of the steering device with the traveling device stopped to make the front body align with the imaginary straight line, and after aligning the front body with the imaginary straight line, controls the operations of the traveling device and the steering device to make the front body move straight along the imaginary straight line, and the control device receives information indicating an angle between the imaginary straight line and the front body when the center between the front wheels is aligned with the waypoint, and a position of the front body when the center between the front wheels is aligned with the waypoint. a table that specifies the relationship between the position of the waypoint and the position of the front body that can be aligned with the virtual straight line without the bucket coming into contact with the object to be loaded from a state in which the center between the front wheels coincides with the waypoint; and the control device, before aligning the center between the front wheels with the waypoint, calculates the relationship between the angle formed when the center between the front wheels is positioned at an assumed point that is an assumed waypoint, based on the current position of the vehicle body and the position of the object to be loaded, and calculates the relationship between the calculated angle and the position of the assumed point;The waypoints are set based on the table. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a wheel loader that can move to a loading position within a limited travel distance through autonomous driving. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a side view of a wheel loader according to the first embodiment. [Figure 2] FIG. 2 is a system configuration diagram of a wheel loader. [Figure 3] FIG. 3 is a diagram illustrating the path following travel of the wheel loader. [Figure 4] FIG. 4 is a schematic plan view showing the positional relationship between the wheel loader and the hopper at the completion of path following traveling, at the completion of positioning operation, at the completion of orientation operation, and at the completion of front straight traveling operation. [Figure 5] FIG. 5 is a diagram illustrating a hardware configuration of the control device. [Figure 6] FIG. 6 is a functional block diagram of the control device according to the first embodiment. [Figure 7] FIG. 7 is a schematic plan view showing an example of the stopping position and posture of the wheel loader when the positioning operation is completed. [Figure 8]FIG. 8 is a diagram illustrating an example of a method for determining whether or not the conditions for enabling approach to the hopper are met. [Figure 9] FIG. 9 is a diagram illustrating an example of a method for setting a waypoint. [Figure 10] FIG. 10 is a flowchart illustrating an example of the flow of approaching operation control executed by the control device. [Figure 11] FIG. 11 is a side view showing the wheel loader according to the second embodiment approaching the hopper. [Figure 12] FIG. 12 is a functional block diagram of a control device according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, a wheel loader according to an embodiment of the present invention will be described with reference to the drawings.

[0011] First Embodiment - Overall configuration of the wheel loader - Figure 1 is a side view of an autonomously operable wheel loader 1 according to an embodiment of the present invention. As shown in Figure 1, the wheel loader (hereinafter also referred to as vehicle) 1 comprises an articulated vehicle body 16 and an articulated working device 17 attached to the front of the vehicle body 16. The vehicle body 16 comprises a front body 11 having a pair of left and right front wheels 4a (wheels 4), and a rear body 12 having a pair of left and right rear wheels 4b (wheels 4). The front body 11 and rear body 12 are connected by a center pin 13 so as to be able to bend in the left and right direction.

[0012] The wheel loader 1 is equipped with a steering device 19 that steers by bending the vehicle body 16 around a center pin 13 as the bending center, thereby changing the bending angle. The steering device 19 has a pair of left and right hydraulic cylinders (hereinafter also referred to as steering cylinders) 14 that connect the front body 11 and the rear body 12. The pair of steering cylinders 14 are provided on both the left and right sides of the center pin 13. The rear body 12 has a driver's cab 5 and an engine compartment 6.

[0013] The cab 5 is provided with a control device 100 that controls each section of the wheel loader 1, and an input device 76 that inputs input information to the control device 100 in response to operation by the operator. The input device 76 is, for example, a switch device having a plurality of switches. The input device 76 may also be a touch sensor device that is provided over the display screen of a display device such as a liquid crystal display device or an organic EL display device.

[0014] An alarm device 75 that notifies the operator of information such as warnings is provided in the operator's cab 5. The alarm device 75 is, for example, a display device such as a liquid crystal display device that notifies the operator of warnings by image, or an audio output device such as a speaker that notifies the operator of warnings by voice.

[0015] The working device 17 is attached to the front body 11. The working device 17 includes a lift arm 2 that is attached to the front body 11 so as to be rotatable in the vertical direction, a bucket 3 that is attached to the tip of the lift arm 2 so as to be rotatable in the vertical direction, a hydraulic cylinder (hereinafter also referred to as an arm cylinder) 7 that drives the lift arm 2, and a hydraulic cylinder (hereinafter also referred to as a bucket cylinder) 8 that drives the bucket 3. The lift arm 2 and the arm cylinder 7 are provided one on each side of the front body 11. The bucket 3 rotates by extension and contraction of the bucket cylinder 8 via a bell crank 9 and a bucket link 10, which causes the orientation of the bucket 3 to move up and down.

[0016] The arm cylinder 7 extends when pressure oil is supplied to the bottom chamber, causing the lift arm 2 to rotate upward (lift up), and retracts when pressure oil is supplied to the rod chamber, causing the lift arm 2 to rotate downward (lift down). The bucket cylinder 8 extends when pressure oil is supplied to the bottom chamber, causing the bucket 3 to rotate upward (tilt), and retracts when pressure oil is supplied to the rod chamber, causing the bucket 3 to rotate downward (dump).

[0017] The wheel loader 1 is steered by the relative rotation of the front body 11 and the rear body 12 caused by the extension and contraction of a pair of left and right steering cylinders 14. When the right steering cylinder 14 retracts and the left steering cylinder 14 extends, the vehicle body 16 bends to the right. When the left steering cylinder 14 retracts and the right steering cylinder 14 extends, the vehicle body 16 bends to the left. In this specification, the bending angle corresponds to the angle of rotation about the center pin 13. The bending angle is 0 (zero) degrees when the vehicle is not bent, that is, when the wheel loader 1 is in a posture in which it moves straight ahead. The bending angle takes a positive value when the vehicle body 16 is bent to the right, and takes a negative value when the vehicle body 16 is bent to the left.

[0018] An object detection sensor 73 that detects an object in front of the car body 16 is attached to the upper part of the cab 5. A bending angle sensor 72 that detects the bending angle of the car body 16 is attached to the center pin 13.

[0019] -Wheel loader system configuration- Figure 2 is a system configuration diagram of the wheel loader 1. As shown in Figure 2, the wheel loader 1 is equipped with a traveling device 28 that causes the vehicle body 16 to travel, a work device 17 that performs excavation work, a steering device 19 that steers the vehicle body 16, a braking device 18 that brakes the vehicle body 16 and prevents the vehicle body 16 from moving when it is stopped, an engine 50 that serves as a drive source for these devices, a control device 100 that controls each part of the wheel loader 1, and hydraulic pumps 60A, 60B, 60C that are mechanically connected to the engine 50. The braking device 18 constitutes part of the traveling device 28.

[0020] The working device 17 is driven by hydraulic oil discharged from the hydraulic pump 60A, the braking device 18 is driven by hydraulic oil discharged from the hydraulic pump 60B, and the steering device 19 is driven by hydraulic oil discharged from the hydraulic pump 60C.

[0021] The wheel loader 1 includes a front control unit 61 that controls the operation of the working device 17 , a brake control unit 62 that controls the operation of the braking device 18 , and a steering control unit 63 that controls the operation of the steering device 19 .

[0022] The work device 17 and the traveling device 28 are driven independently of each other by the power of the engine 50. The engine 50 is configured by an internal combustion engine such as a diesel engine. The wheel loader 1 is equipped with an engine control unit 65 that controls the operation of the engine 50. The engine control unit 65 controls the fuel injection amount so that the actual rotation speed detected by the engine rotation speed sensor approaches the target rotation speed calculated by the control device 100.

[0023] The arm cylinder 7 and the bucket cylinder 8 are extended and retracted by hydraulic oil (pressurized oil) discharged from a hydraulic pump 60A that is rotated by torque output by the engine 50.

[0024] The traveling device 28 has wheels 4 and a power transmission device that transmits power from the engine 50 to the wheels 4. The power transmission device includes a torque converter 51, a transmission 52, a propeller shaft 53, a differential device 54, an axle 55, etc.

[0025] An input shaft of a torque converter 51 is connected to the output shaft of the engine 50, and the output shaft of the torque converter 51 is connected to a transmission 52. The torque converter 51 is a well-known fluid clutch made up of an impeller, turbine, and stator, and the rotation of the engine 50 is transmitted to the transmission 52 via the torque converter 51. The transmission 52 has a clutch that changes its speed stages between first and fifth gears, and the rotation of the output shaft of the torque converter 51 is changed in speed by the transmission 52. The rotation after the speed change is transmitted to the wheels 4 via a propeller shaft 53, a differential device 54, and an axle 55, and the wheel loader 1 travels.

[0026] The wheel loader 1 is equipped with a transmission control unit 64 that controls the operation of the transmission 52. The transmission control unit 64 has solenoid valves that correspond to each of the first to fifth speed stages of the transmission 52. The transmission control unit 64 controls the transmission 52 by operating the solenoid valves in response to control signals from the control device 100.

[0027] The hydraulic pumps 60A, 60B, and 60C are mechanically connected to the engine 50. The hydraulic pumps 60A, 60B, and 60C are driven by the torque output by the engine 50 to discharge hydraulic oil.

[0028] The pressure, flow rate, and flow direction of hydraulic oil supplied from the hydraulic pump 60A to the arm cylinder 7 and the bucket cylinder 8 are controlled by the front control unit 61. As a result, excavation and loading operations are performed by the work implement 17. The pressure, flow rate, and flow direction of hydraulic oil supplied from the hydraulic pump 60B to the brake cylinder 18a and the parking brake cylinder 18b are controlled by the brake control unit 62. As a result, braking operations and stop-holding operations of the vehicle body 16 are performed by the brake device 18. The pressure, flow rate, and flow direction of hydraulic oil supplied from the hydraulic pump 60C to the pair of left and right steering cylinders 14 are controlled by the steering control unit 63. As a result, the vehicle body 16 is steered by the steering device 19.

[0029] 2, the wheel loader 1 is equipped with a position detection device 71 that detects the position of the vehicle itself and outputs a signal indicating the detection result to the control device 100. The position detection device 71 has, for example, antennas for multiple GNSS (Global Navigation Satellite Systems), and a positioning calculation device that calculates the position and orientation of the vehicle body 16 in a global coordinate system based on satellite signals (GNSS radio waves) from multiple positioning satellites received by the GNSS antenna.

[0030] The multiple GNSS antennas are provided, for example, in the driver's cab 5 of the rear body 12. In this case, the position detection device 71 calculates the position of a reference point of the rear body 12 (for example, the position of the center pin 13) and the orientation (direction) of the rear body 12.

[0031] The position detection device 71 is not limited to this, and may also be equipped with a wheel speed sensor and a gyro sensor that detects the rotational speed of the wheels 4. The positioning calculation device calculates the travel distance of the wheel loader 1 based on the detection results of the wheel speed sensor, and calculates the travel direction of the wheel loader 1 based on the detection results of the gyro sensor.

[0032] The wheel loader 1 is equipped with a bending angle sensor 72 and a vehicle speed sensor 74. The bending angle sensor 72 is, for example, a rotary encoder provided on the center pin 13, which detects the bending angle of the vehicle body 16 and outputs a signal representing the detection result to the control device 100. The bending angle is a physical quantity that represents the attitude of the vehicle body 16. In other words, the bending angle sensor 72 functions as an attitude sensor that detects the attitude of the vehicle body 16. Note that a stroke sensor that detects the stroke amount of the steering cylinder 14 may be used as the bending angle sensor 72 that detects the bending angle of the vehicle body 16. In this case, the control device 100 calculates the bending angle of the vehicle body 16 based on the stroke amount of the steering cylinder 14.

[0033] The vehicle speed sensor 74 detects the traveling speed of the vehicle (hereinafter also referred to as vehicle speed) and outputs a signal representing the detection result to the control device 100.

[0034] An example of work performed by the wheel loader 1 will be described below. The wheel loader 1 moves forward toward the natural ground, which is the object to be excavated, plunges the bucket 3 into the natural ground, and operates the bucket 3 and lift arm 2 to perform excavation work to excavate the natural ground. After completing the excavation work, the wheel loader 1 travels toward the object to be loaded and stops at a loading position in front of the object to be loaded. The wheel loader 1 then performs loading work, loading the load (excavated material) in the bucket 3 onto the object to be loaded. After completing the loading work, the wheel loader 1 travels again toward the object to be excavated.

[0035] The control device 100 generates a travel route based on the excavation position and loading position at the work site, and stores multiple nodes that define the travel route in non-volatile memory 102 (see FIG. 5). The control device 100 controls the traveling device 28 and steering device 19 so that the vehicle body 16 travels along the generated travel route. As a result, the wheel loader 1 automatically travels along the travel route to the target position (excavation position or loading position). Furthermore, the control device 100 controls the working device 17 at the excavation position, so that the working device 17 performs excavation work. Furthermore, the control device 100 controls the working device 17 at the loading position, so that the working device 17 performs loading work.

[0036] - Path-following driving - After the excavation work is completed, the wheel loader 1 performs path-following traveling by autonomous driving. FIG. 3 is a diagram illustrating path-following traveling of the wheel loader 1. In this embodiment, an example will be described in which the loading object is a hopper 20. As shown in FIG. 3, the control device 100 controls the operation of the traveling device 28 and the steering device 19 so that the vehicle body 16 travels along the traveling path 22. In the following, the control executed by the control device 100 to travel the vehicle body 16 along the traveling path 22 will also be referred to as path-following traveling control.

[0037] The travel route 22 is specified by a plurality of nodes 23 stored in the non-volatile memory 102 (see FIG. 5). The nodes 23 are data indicating coordinates on the travel route 22. The control device 100 may autonomously drive the vehicle body 16 so that the deviation between a reference point of the vehicle body 16 (for example, the center between the front wheels 4ac) and the travel route 22 is minimized, or may autonomously drive the vehicle body 16 so that the reference point of the vehicle body 16 (for example, the center between the front wheels 4ac) passes through the node 23.

[0038] The control device 100 generates control targets including a target vehicle speed and a target bending angle based on the position and orientation of the vehicle body 16 detected by the position detection device 71, the vehicle speed detected by the vehicle speed sensor 74, the bending angle of the vehicle body 16 detected by the bending angle sensor 72, and the nodes 23 stored in the non-volatile memory 102 (see FIG. 5). The control device 100 controls the traveling device 28 so that the vehicle speed detected by the vehicle speed sensor 74 becomes the target vehicle speed. The control device 100 also controls the steering device 19 so that the bending angle of the vehicle body 16 detected by the bending angle sensor 72 becomes the target bending angle.

[0039] The multiple nodes including the target position are expressed, for example, by coordinates in a global coordinate system. The target position may also be expressed by coordinates in a site coordinate system with a predetermined position on the work site as its origin. The reference direction is set, for example, to true north. Coordinate conversion is possible between the global coordinate system and the site coordinate system. Furthermore, the orientation of the rear body 12 detected by the position detection device 71 can be converted to the orientation of the front body 11 using the bending angle of the vehicle body 16 detected by the bending angle sensor 72.

[0040] -Approach action- After completing path-following traveling, the wheel loader 1 performs an approach operation to the hopper 20 by autonomous driving. The approach operation of the wheel loader 1 to the hopper 20 will be described with reference to Figure 4. The approach operation includes a positioning operation that is performed after completion of path-following traveling, an orientation adjustment operation that is performed after completion of the positioning operation, and a front straight movement operation that is performed after completion of the orientation adjustment operation. Figure 4 is a schematic plan view showing the positional relationship between the wheel loader 1 and the hopper 20 at the completion of path-following traveling, at the completion of the positioning operation, at the completion of the orientation adjustment operation, and at the completion of the front straight movement operation.

[0041] The hopper 20 is provided with side walls 20a to prevent the load from mixing with an adjacent hopper (not shown). For example, the hopper 20 is formed in the shape of a rectangular box with an open top, and has a rectangular bottom plate and four side walls 20a rising from each of the four sides of the bottom plate. During loading operations of the wheel loader 1, the side wall 20a directly facing the wheel loader 1 is referred to as the front side wall 20af. The wheel loader 1 must move to the loading position P2 and perform the loading operation without coming into contact with the side walls 20a of the hopper 20.

[0042] Because the wheel loader 1 is an articulated vehicle, when the body 16 is steered, the body 16 bends around the center pin 13. When the body 16 is steered and bends while the vehicle is stopped, the position of the center between the front wheels 4ac and the position of the center between the rear wheels 4bc hardly move, but the position of the center pin 13 moves significantly in the left-right direction.

[0043] The center between the front wheels 4ac refers to the center between the pair of left and right front wheels 4a, i.e., the midpoint of the line segment connecting the center of the left front wheel 4a and the center of the right front wheel 4a. The center between the rear wheels 4bc refers to the center between the pair of left and right rear wheels 4b, i.e., the midpoint of the line segment connecting the center of the left rear wheel 4b and the center of the right rear wheel 4b.

[0044] - Alignment operation - 4(a) shows the positional relationship between the wheel loader 1 and the hopper 20 at the time when the path-following travel of the wheel loader 1 under path-following travel control is completed. In path-following travel control, the control device 100 decelerates and stops the vehicle body 16 at a node (also referred to as the final node) 23a (see FIG. 3) that defines the end of the travel path 22, as the stopping target point. The final node 23a is set just before the loading position into the hopper 20.

[0045] When the completion condition for path following traveling is met, the control device 100 ends the path following traveling control, and executes approach operation control to bring the vehicle body 16 closer to the hopper 20. For example, the control device 100 determines that the completion condition for path following traveling is met when the distance between the final node 23a and a reference point of the wheel loader 1 (for example, the center 4ac between the front wheels) becomes equal to or less than a predetermined distance threshold and the vehicle body 16 comes to a stop.

[0046] The approaching operation control includes positioning control, heading control, and front straight ahead control. As shown in Fig. 4(a), when the completion condition for path following traveling is met, the control device 100 executes positioning control in the approaching operation control.

[0047] In the positioning control, the control device 100 calculates the relative position between the hopper 20 located in front of the vehicle body 16 and the vehicle body 16. The relative position between the hopper 20 and the vehicle body 16 includes a relative distance x1 between the hopper 20 and the vehicle body 16. Based on the shape data of the hopper 20 stored in the nonvolatile memory 102 (see FIG. 5) and the calculated relative position of the hopper 20 and the vehicle body 16, the control device 100 sets a waypoint (target point) P1 at a position farther away from the hopper 20 than the distance x0 between the center 4ac between the front wheels and the tip of the bucket 3. The shape data of the hopper 20 includes the positions of characteristic points such as the corners of the hopper 20. The control device 100 extracts a plurality of characteristic points of the hopper 20 based on the detection results of the object detection sensor 73 and stores the extracted plurality of characteristic points as shape data of the hopper 20 in the nonvolatile memory 102 (see FIG. 5).

[0048] The waypoint P1 is set on an imaginary line extending from the hopper 20. In this embodiment, the imaginary line on which the waypoint P1 is set is the center line CL of the hopper 20, which bisects the hopper 20 in the longitudinal direction.

[0049] The control device 100 controls the operation of the engine 50, the traveling device 28, and the steering device 19 to align the center line 4ac between the front wheels with the set waypoint P1.

[0050] - Orientation adjustment operation - FIG. 4(b) shows the positional relationship between the wheel loader 1 and the hopper 20 at the time when the positioning operation of the wheel loader 1 under positioning control is completed. When the positioning operation is completed by aligning the center line 4ac between the front wheels with the waypoint P1, the control device 100 ends the positioning control and executes orientation control. In orientation control, the control device 100 controls the operation of the steering device 19 with the traveling device 28 stopped, and aligns the direction (orientation) of the front body 11 with the center line CL of the hopper 20. As a result of the orientation adjustment operation, the center line of the front body 11, which extends in the fore-and-aft direction of the front body 11, becomes parallel to the center line CL of the hopper 20. In addition, the front body 11 faces the front side wall 20af of the hopper 20.

[0051] -Front straight movement- 4(c) shows the positional relationship between the wheel loader 1 and the hopper 20 at the time when the orientation adjustment operation of the wheel loader 1 using the orientation adjustment control is completed. When the orientation adjustment operation is completed by orienting the front body 11 along the center line CL of the hopper 20, the control device 100 ends the orientation adjustment control and executes the front straight running control.

[0052] In the front straight traveling control, the control device 100 controls the operation of the engine 50, the traveling device 28, and the steering device 19 to cause the front body 11 to travel along the center line CL of the hopper 20. During forward traveling, the orientation of the front body 11 is maintained, and the magnitude (absolute value) of the bending angle gradually decreases. In addition, in the front straight traveling control, the control device 100 performs a lifting operation of the lift arm 2 while causing the front body 11 to travel straight, thereby positioning the bucket 3 above the hopper 20 without interfering with the hopper 20. The control device 100 aligns the center 4ac between the front wheels with the loading position P2 and stops the vehicle body 16.

[0053] -Loading operation- FIG. 4(d) shows the positional relationship between the wheel loader 1 and the hopper 20 at the time when the front straight movement of the wheel loader 1 under the front straight movement control is completed. The control device 100 ends the front straight movement control when the front wheel center 4ac is aligned with the loading position and the front straight movement is completed. In other words, the control device 100 ends the approaching movement control. Note that when the approaching movement is completed, the control device 100 executes loading control. In the loading control, the control device 100 performs a dumping operation of the bucket 3 to release the excavated material in the bucket 3 into the hopper 20.

[0054] As described above, after completing the path following travel, the control device 100 executes approaching operation control for moving the wheel loader 1 to the loading position P2 via the waypoint P1. Details of this approaching operation control will be described later.

[0055] -Control device hardware configuration- FIG. 5 is a diagram showing the hardware configuration of the control device 100. As shown in FIG. 5, the control device 100 is configured by a computer including a processing device 101 such as a CPU (Central Processing Unit), an MPU (Micro Processing Unit), or a DSP (Digital Signal Processor), a non-volatile memory 102 such as a ROM (Read Only Memory), a flash memory, or a hard disk drive, a volatile memory 103 called a RAM (Random Access Memory), an input interface 104, an output interface 105, and other peripheral circuits. The control device 100 may be configured by one computer or multiple computers. The processing device 101 may be an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or the like.

[0056] The nonvolatile memory 102 stores programs capable of executing various calculations, and data such as thresholds used in the various calculations. In other words, the nonvolatile memory 102 is a storage device (storage medium) from which a program realizing the functions of this embodiment can be read. The processing device 101 is an arithmetic processing device that loads the program stored in the nonvolatile memory 102 into the volatile memory 103 and executes arithmetic processing. The processing device 101 performs predetermined arithmetic processing on signals received from the input interface 104, the nonvolatile memory 102, and the volatile memory 103 in accordance with the program.

[0057] The input interface 104 converts signals input from the position detection device 71, the bending angle sensor 72, the object detection sensor 73, the vehicle speed sensor 74, and the input device 76 into data that can be calculated by the processing device 101. In addition, the output interface 105 generates an output signal according to the calculation result in the processing device 101, and outputs the signal to the solenoid valve that controls the operation of hydraulic equipment (hydraulic pump, hydraulic actuator), the alarm device 75, etc.

[0058] The object detection sensor 73 is, for example, a LiDAR. Note that, instead of a LiDAR, a millimeter wave radar, a laser radar, a stereo camera, or the like may be adopted as the object detection sensor 73.

[0059] -Controller function- 6 is a functional block diagram of the control device 100. By executing programs stored in the nonvolatile memory 102, the control device 100 functions as a wheel-to-wheel center calculation unit 33, a hopper position calculation unit 34, a bucket position calculation unit 35, a waypoint calculation unit 37, a relative position calculation unit 38, a position alignment completion determination unit 40, a heading alignment completion determination unit 41, a front straight driving completion determination unit 42, a target value calculation unit 43, and a vehicle control unit 44.

[0060] -Position calculation section- The wheel-to-wheel center calculation unit 33, the hopper position calculation unit 34, and the bucket position calculation unit 35 function as a position calculation unit 31 that calculates the position of each part of the wheel loader 1.

[0061] The wheel center calculation unit 33 calculates the position of the front wheel center 4ac and the position of the rear wheel center 4bc based on the detection results of the bending angle sensor 72, the detection results of the object detection sensor 73, and input information (input data) from the input device 76. The position of the front wheel center 4ac is, for example, the relative position of the front wheel center 4ac with respect to the center pin 13. The position of the rear wheel center 4bc is, for example, the relative position of the rear wheel center 4bc with respect to the center pin 13.

[0062] In response to an operation by an operator, the input device 76 inputs the following information (input data) to the control device 100: the distance from the articulation center to the front wheel center 4ac as information on the relative position between the center pin 13 and the front wheel center 4ac; the distance from the articulation center to the rear wheel center 4bc as information on the relative position between the center pin 13 and the rear wheel center 4bc; and the position coordinates of the attachment position (installation position) of the object detection sensor 73 as information on the relative position between the center pin 13 and the object detection sensor 73. The relative positions (input information) input to the control device 100 are stored in the non-volatile memory 102. The input of the relative positions by the input device 76 is performed at the time of manufacture (shipment) and when a deviation in the position of each part occurs due to deterioration over time.

[0063] The hopper position calculation unit 34 extracts characteristic points of the hopper 20 based on the detection results of the object detection sensor 73 and input information from the input device 76, and calculates the positions of the extracted characteristic points of the hopper 20. The positions of the characteristic points of the hopper 20 are relative positions with respect to reference points of the vehicle body 16 (for example, the center pin 13, the center between the front wheels 4ac). The characteristic points of the hopper 20 are, for example, the intersection of the front side wall 20af and the center line CL of the hopper 20 (the entrance position of the hopper 20), the four corners of the top opening of the hopper 20, etc.

[0064] The bucket position calculation unit 35 extracts characteristic points of the bucket 3 based on the detection results of the object detection sensor 73 and input information from the input device 76, and calculates the positions of the extracted characteristic points of the bucket 3. The positions of the characteristic points of the bucket 3 are relative positions with respect to reference points of the vehicle body 16 (for example, the center pin 13, the center 4ac between the front wheels). The characteristic points of the bucket 3 are, for example, the tip end (toe) of the bucket 3, and the left and right ends of the bucket 3.

[0065] -Operation calculation section- The waypoint calculation unit 37, relative position calculation unit 38, alignment completion determination unit 40, orientation alignment completion determination unit 41, front straight driving completion determination unit 42, and target value calculation unit 43 function as an operation calculation unit 32 that calculates target values ​​for operating each part of the vehicle body 16 according to the procedure for approaching the vehicle body 16 to the hopper 20 based on the calculation results of the position calculation unit 31.

[0066] The waypoint calculation unit 37 uses the calculation results of the wheel-to-wheel center calculation unit 33, the hopper position calculation unit 34, and the bucket position calculation unit 35 to determine whether or not it is possible to approach the hopper 20 (i.e., whether or not the conditions for approaching the hopper 20 are met), and calculates the optimal waypoint P1 on the route from the position of the vehicle body 16 at the time of completion of path following driving (current position) to the loading position P2.

[0067] Prior to calculating the waypoint P1, the waypoint calculation unit 37 determines whether or not the conditions for approaching the hopper 20 are met when the route following travel is completed. The conditions for approaching the hopper 20 include the following (Condition 1) and (Condition 2). (Condition 1) By operating the steering device 19 and driving the vehicle forward using the traveling device 28, it is possible to align the center 4ac between the front wheels with the waypoint P1. (Condition 2) By stopping the running device 28 and operating the steering device 19 while aligning the center 4ac between the front wheels with the intermediate point P1, it is possible to align the direction of the front body 11 with the center line CL of the hopper 20.

[0068] The waypoint calculation unit 37 determines that the conditions for approaching the hopper 20 are met when both (Condition 1) and (Condition 2) are met, and determines that the conditions for approaching the hopper 20 are not met when at least one of (Condition 1) and (Condition 2) is not met.

[0069] In this way, the waypoint calculation unit 37 determines whether or not the front body 11 can be aligned with the waypoint P1 and the orientation of the front body 11 with respect to the center line CL of the hopper 20 can be aligned.

[0070] A method for calculating the waypoint P1 and a method for determining whether the approachable condition is met will be described in detail with reference to Figures 7 to 9. Figure 7 is a schematic plan view showing an example of the stopping position and posture of the wheel loader 1 when the positioning operation is complete. Figure 7 also shows the range A0 (hereinafter also referred to as the azimuth adjustment possible area) that the front wheel center 4ac, center pin 13, and rear wheel center 4bc can take, which allow azimuth adjustment from the state when positioning is complete. The azimuth adjustment possible area A0 is approximately pentagonal.

[0071] The orientation adjustment possible area A0 is an area surrounded by a line segment A1A2 connecting points A1 and A2, a line segment A2A3 connecting points A2 and A3, a line segment A1A5 connecting points A1 and A5, a line segment A5A4 connecting points A5 and A4, and an arc A3A4 connecting points A3 and A4. Point A1 corresponds to the position of the front wheel center 4ac that coincides with waypoint P1. Points A2 and A5 correspond to the positions of the center pin 13 when the bending angle α of the wheel loader 1 is the maximum bending angle αmax. Points A3 and A4 correspond to the position of the rear wheel center 4bc when the bending angle α of the wheel loader 1 is the maximum bending angle αmax.

[0072] The arc A3A4 corresponds to a set of possible points for the rear wheel center 4bc when the front wheel center 4ac is located at the waypoint P1 and the center pin 13 is located on the center line CL of the hopper 20. The lengths of the line segments A1A2 and A1A5 correspond to the length from the front wheel center 4ac to the center pin 13. The lengths of the line segments A2A3 and A5A4 and the radius of the arc A3A4 correspond to the length from the center pin 13 to the rear wheel center 4bc.

[0073] Points A2 and A3 are the positions of the center pin 13 and the rear wheel center 4bc when the vehicle body 16 is bent to the maximum in the leftward direction, and points A5 and A4 are the positions of the center pin 13 and the rear wheel center 4bc when the vehicle body 16 is bent to the maximum in the rightward direction. The orientation adjustment possible area A0 shown in Figure 7 is illustrated as an area that takes into account both the case where the center pin 13 is on the right side and the case where it is on the left side with respect to the hopper 20. For this reason, the orientation adjustment possible area A0 has an axisymmetric shape with the center line CL of the hopper 20 as the axis of symmetry.

[0074] Point A1 is located on waypoint P1, and line segments A2A3 and A5A4 are parallel to the center line CL of the hopper 20. The exterior angles at points A2 and A5 of the orientation adjustment possible area A0 are each equal to the maximum bending angle αmax of the car body 16. As described above, when the car body 16 is bent while stopped, the positions of the center between the front wheels 4ac and the center between the rear wheels 4bc remain almost unchanged, and the position of the center pin 13 moves left and right. For example, when the center between the front wheels 4ac, the center pin 13, and the center between the rear wheels 4bc are located at points A1, A2, and A3, respectively, the change in the position of the center pin 13 is as follows: When the car body 16 is bent from its maximum bending to the left to its maximum bending to the right, the center pin 13 is positioned on the center line CL of the hopper 20 (see point A2'). As a result, the center line of the front body 11 and the center line CL of the hopper 20 become parallel to each other, and the front body 11 and the front side wall 20af of the hopper 20 face each other.

[0075] 7, dashed lines indicate the lines connecting the front wheel center 4ac, the center pin 13, and the rear wheel center 4bc when the wheel loader 1 has completed its orientation adjustment operation, with the front wheel center 4ac, the center pin 13, and the rear wheel center 4bc positioned at points A1, A2, and A3. Although not shown, if the front wheel center 4ac, the center pin 13, and the rear wheel center 4bc are similarly positioned at points A1, A5, and A4, the center pin 13 can be positioned on the center line CL of the hopper 20 by bending the vehicle body 16 to the maximum extent to the left.

[0076] On the other hand, when the center pin 13 is located outside the orientation adjustment area A0, no matter how the vehicle body 16 is bent, the center pin 13 cannot be positioned on the center line CL of the hopper 20. In other words, the center line of the front body 11 cannot be made parallel to the center line CL of the hopper 20.

[0077] As described above, the orientation adjustment possible area A0 indicates the limit of the stopping position and posture of the vehicle body 16 where the orientation (orientation) of the front body 11 can be aligned to a direction parallel to the center line CL of the hopper 20 after the alignment operation is completed, i.e., where orientation adjustment is possible. In other words, when the alignment operation is completed and the front wheel center 4ac is located at point A1, if the rear wheel center 4bc is located between a line passing through points A2 and A3 and a line passing through points A5 and A4, and if the angle θ between the center line CL of the hopper 20 and the center line of the front body 11 is equal to or less than the maximum bending angle, then orientation adjustment can be performed. Note that the center line of the front body 11 is an imaginary line passing through the bending center (center pin 13) of the vehicle body 16 and the front wheel center 4ac.

[0078] An example of a method for determining whether or not the conditions for approaching the hopper 20 are met when path-following traveling has been completed will be described with reference to Fig. 8. Fig. 8 schematically shows the wheel loader 1 when path-following traveling has been completed. Fig. 8 also shows an orientation adjustment possible area A0 when a waypoint P1 is assumed when path-following traveling has been completed.

[0079] After path-following travel is complete, the travel path for aligning the center line 4ac between the front wheels of the wheel loader 1 with the assumed point (point A1), which is the assumed waypoint P1, is the arc C1 that passes through the assumed point (point A1), the center line 4ac between the front wheels, and the center line 4bc between the rear wheels. Because the wheel loader 1 is an articulated vehicle, the center line 4ac between the front wheels and the center line 4bc between the rear wheels pass on the arc C1. For this reason, the condition for enabling positioning is that "the radius of arc C1 is equal to or greater than the minimum turning radius of the vehicle," and the condition for enabling heading alignment is that "arc C1 intersects with arcs A3A4."

[0080] That is, if the radius of arc C1 is equal to or greater than the minimum turning radius of the vehicle, condition 1 is satisfied, but if the radius of arc C1 is less than the minimum turning radius of the vehicle, condition 1 is not satisfied. Also, if arc C1 intersects with arc A3A4, condition 2 is satisfied, but if arc C1 does not intersect with arc A3A4, condition 2 is not satisfied.

[0081] An example of a method for setting waypoint P1 will be described with reference to Figure 9. The horizontal axis of the graph in Figure 9 represents the angle θ between the center line CL of the hopper 20 and the front body 11 when alignment is complete. The vertical axis of the graph in Figure 9 represents the distance x from the hopper 20 to waypoint P1, i.e., the length from the front wall 20af of the hopper 20 on the center line CL to waypoint P1.

[0082] As shown in Figures 4(b) and 4(c), waypoint P1 needs to be set so that the right tip BR and left tip BL of the bucket 3 do not come into contact with the hopper 20 during the orientation adjustment operation. The shortest distance between waypoint P1, at which the bucket 3 does not come into contact with the hopper 20 during the orientation adjustment operation, and the hopper 20 varies depending on the position of the bucket 3 and the angle θ formed when the position adjustment operation is complete. Note that the positions of the right tip BR and left tip BL of the bucket 3 vary depending on the height of the bucket 3.

[0083] Contact prevention characteristic curve A shown in FIG. 9 indicates the relationship between the position of waypoint P1 (the distance from the hopper 20 to waypoint P1) at which the bucket 3 does not come into contact with the hopper 20 during the azimuth alignment operation when the position of the bucket 3 is constant, and the angle θ formed between the center line CL of the hopper 20 and the front body 11. Note that the position of the bucket 3 is the relative position of the bucket 3 with respect to the center pin 13 when viewed from above. In the figure, if the area is above contact prevention characteristic curve A, the hopper 20 and the bucket 3 will not come into contact during the azimuth alignment operation. A table of contact prevention characteristic curve A is calculated in advance for each position of the bucket 3 and stored in non-volatile memory 102. Note that the minimum value of the distance x defined by contact prevention characteristic curve A is set to a value that is at least greater than the distance x0 between the center 4ac between the front wheels and the tip of the bucket 3.

[0084] As described above, once path-following traveling is complete, a travel route (see arc C1 in FIG. 8) leading to the assumed point can be determined based on the center line 4ac between the front wheels, the center line 4bc between the rear wheels, and the assumed point that is the assumed way point P1. The direction of the tangent to this travel route (arc C1) at the assumed point (way point P1) corresponds to the orientation of the front body 11 once path-following traveling is complete. Therefore, by determining the travel route (arc C1), the angle θ between the center line CL of the hopper 20 and the center line of the front body 11 can be determined.

[0085] In this way, assuming the waypoint P1 makes it possible to find the angle θ between the center line CL of the hopper 20 and the front body 11. Therefore, once the positions of the center line 4ac between the front wheels and the center line 4bc between the rear wheels are determined at the initial position when the path following traveling is completed, the relationship between the distance x from the hopper 20 to the assumed point (waypoint P1) and the angle θ between the center line CL of the hopper 20 and the front body 11 is uniquely determined.

[0086] The waypoint calculation unit 37 calculates the distance x from the hopper 20 to the assumed waypoint P1 (assumed point) based on the center 4ac between the front wheels and the center 4bc between the rear wheels, the position of the hopper 20, and the center line CL of the hopper 20 at the position at the time of completion of path following driving (initial position), and the allowable bending angle line that defines the relationship between the angle θ between the center line CL of the hopper 20 and the front body 11 when the center 4ac between the front wheels coincides with the waypoint P1.

[0087] Lines A and C shown in Figure 9 are examples of allowable bending angle lines. Note that since the angle θ is equal to or less than the maximum bending angle, lines A and C are lines extending to the position where the angle θ is the maximum bending angle.

[0088] Line B intersects with Line A at Point D. Point D indicates the minimum value of distance x at which alignment and orientation can be performed without the hopper 20 and bucket 3 coming into contact. In contrast, Line C does not have a point at which it intersects with Line A. For this reason, once path following travel is complete, it is not possible to set waypoint P1 at which alignment and orientation operations can be performed without the hopper 20 and bucket 3 coming into contact.

[0089] When the path following traveling is completed, the waypoint calculation unit 37 reads out, from among the multiple contact prevention characteristic curves (see line A in FIG. 9), the contact prevention characteristic curve that corresponds to the current position of the bucket 3. The waypoint calculation unit 37 calculates the allowable bending angle line (see lines B and C in FIG. 9) based on the current positions of the front wheel center 4ac, the rear wheel center 4bc, and the hopper 20.

[0090] The waypoint calculation unit 37 determines whether the approach condition is met based on the read contact prevention characteristic curve and the calculated allowable bending angle line. If the contact prevention characteristic curve and the allowable bending angle line intersect, the waypoint calculation unit 37 determines that the approach condition is met and sets the position of the waypoint P1 based on the distance x at the intersection.

[0091] If the contact prevention characteristic curve and the allowable bending angle line do not intersect, the waypoint calculation unit 37 determines that the approachable condition is not met. If the approachable condition is not met, the waypoint calculation unit 37 controls the notification device 75 to issue a warning to the operator via the notification device 75. The warning is intended to inform the operator that the approachable condition is not met. The warning includes information to inform the operator that it is not possible to move to an appropriate loading position from the current position, and information to request operator assistance.

[0092] When the waypoint calculation unit 37 sets the waypoint P1, the target value calculation unit 43 shown in FIG. 6 cooperates with the vehicle control unit 44 to perform alignment control to align the center between the front wheels 4ac with the waypoint P1.

[0093] The relative position calculation unit 38 calculates the relative positions (relative distance and relative angle) of the hopper 20, the bucket 3, and the front wheel center 4ac based on the calculation results of the wheel center calculation unit 33, the hopper position calculation unit 34, and the bucket position calculation unit 35. The relative position calculation unit 38 also calculates the angle θ between the center line CL of the hopper 20 and the front body 11. The relative position calculation unit 38 also calculates the position (discharge position) at which the material excavated by the bucket 3 is discharged into the hopper 20. The discharge position corresponds to the target position of the control point of the bucket 3. The control point of the bucket 3 can be set to any position on the bucket 3, for example, to the position of the bucket pin that connects the lift arm 2 and the bucket 3.

[0094] When the position of waypoint P1 is calculated by waypoint calculation unit 37, alignment completion determination unit 40 determines whether or not the completion condition for the alignment operation is met based on the calculation results of waypoint calculation unit 37 and the calculation results of relative position calculation unit 38. For example, when the position of front wheel center 4ac coincides with the position of waypoint P1 calculated by waypoint calculation unit 37, alignment completion determination unit 40 determines that the completion condition for the alignment operation is met.

[0095] If the front wheel center 4ac is located within a predetermined range from the position of the waypoint P1, the alignment completion determination unit 40 determines that the position of the front wheel center 4ac coincides with the position of the waypoint P1. More specifically, the alignment completion determination unit 40 calculates a distance y from the waypoint P1 to the front wheel center 4ac. If the calculated distance y is equal to or less than a predetermined distance threshold y0, the alignment completion determination unit 40 determines that the position of the front wheel center 4ac coincides with the position of the waypoint P1, and the completion condition for the alignment operation is met. If the calculated distance y is greater than the distance threshold y0, the alignment completion determination unit 40 determines that the position of the front wheel center 4ac does not coincide with the position of the waypoint P1, and the completion condition for the alignment operation is not met.

[0096] When it is determined that the conditions for completing the alignment operation are met, the alignment completion determination unit 40 outputs a completion signal for the alignment operation to the target value calculation unit 43 and the azimuth alignment completion determination unit 41. Upon receiving the completion signal for the alignment operation, the target value calculation unit 43 completes the alignment control and starts azimuth alignment control in cooperation with the vehicle control unit 44.

[0097] When the azimuth alignment completion determination unit 41 receives the completion signal of the position alignment operation, it determines whether or not the completion condition for the azimuth alignment operation is met based on the calculation result of the relative position calculation unit 38. For example, the azimuth alignment completion determination unit 41 determines that the completion condition for the azimuth alignment operation is met when the angle θ between the center line CL of the hopper 20 and the front body 11 calculated by the relative position calculation unit 38 is equal to or smaller than the angle threshold value θ0. When the angle θ is larger than the predetermined angle threshold value θ0, the azimuth alignment completion determination unit 41 determines that the completion condition for the azimuth alignment operation is not met.

[0098] When it is determined that the conditions for completing the heading adjustment operation are met, the heading adjustment completion determination unit 41 outputs a completion signal for the heading adjustment operation to the target value calculation unit 43 and the front straight running completion determination unit 42. Upon receiving the completion signal for the heading adjustment operation, the target value calculation unit 43 completes the heading adjustment control and starts the front straight running control in cooperation with the vehicle control unit 44.

[0099] When the front straight traveling completion determination unit 42 receives the completion signal of the azimuth alignment operation, it determines whether or not the completion condition for the front straight traveling operation is met based on the calculation result of the relative position calculation unit 38. For example, when the bucket 3 is positioned above the hopper 20, the front straight traveling completion determination unit 42 determines that the completion condition for the front straight traveling operation is met.

[0100] If the control point of bucket 3 is located within a predetermined range of the discharge position relative to hopper 20, front straight traveling completion determination unit 42 determines that the completion condition for the front straight traveling operation is met. More specifically, front straight traveling completion determination unit 42 calculates distance z from the discharge position to the control point of bucket 3. If the calculated distance z is equal to or less than a predetermined distance threshold z0, front straight traveling completion determination unit 42 determines that bucket 3 is located above hopper 20 and the completion condition for the front straight traveling operation is met. If the calculated distance z is greater than distance threshold z0, front straight traveling completion determination unit 42 determines that bucket 3 is not located above hopper 20 and the completion condition for the front straight traveling operation is not met.

[0101] Note that the determination method used by front straight traveling completion determination unit 42 is not limited to this. For example, relative position calculation unit 38 calculates a loading position, which is a target position of center 4ac between the front wheels when releasing excavated material from bucket 3. Front straight traveling completion determination unit 42 may determine that the condition for completing the front straight traveling operation has been met when center 4ac between the front wheels coincides with the loading position calculated by relative position calculation unit 38.

[0102] When it is determined that the conditions for completing the front straight running operation are met, the front straight running completion determination unit 42 outputs a completion signal for the front straight running operation to the target value calculation unit 43. Upon receiving the completion signal for the front straight running operation, the target value calculation unit 43 completes the front straight running control and starts loading control in cooperation with the vehicle control unit 44.

[0103] When path following travel is completed and waypoint P1 is set, target value calculation unit 43 calculates a target value for performing a positioning operation. When target value calculation unit 43 receives a positioning completion signal from positioning completion determination unit 40, it calculates a target value for performing an azimuth alignment operation. When target value calculation unit 43 receives a completion signal for the azimuth alignment operation, it calculates a target value for performing a front straight ahead operation. When target value calculation unit 43 receives a completion signal for the front straight ahead operation, it calculates a target value for releasing the excavated material from bucket 3. The target values ​​include a target vehicle speed, a target bending angle, a target arm angle, and a target bucket angle.

[0104] The target value calculation unit 43 uses the position of waypoint P1 calculated by waypoint calculation unit 37 and the calculation result of relative position calculation unit 38 to calculate the target value. Vehicle control unit 44 controls various parts of the vehicle based on the target value calculated by target value calculation unit 43. For example, vehicle control unit 44 controls steering device 19 so that the bending angle detected by bending angle sensor 72 becomes the target bending angle calculated by target value calculation unit 43. Vehicle control unit 44 also controls engine 50 and traveling device 28 (including brake device 18) so that the vehicle speed detected by vehicle speed sensor 74 becomes the target vehicle speed calculated by target value calculation unit 43. Furthermore, vehicle control unit 44 controls working device 17 so that the arm angle and bucket angle detected by the arm angle sensor and bucket angle sensor become the target arm angle and target bucket angle.

[0105] An example of the flow of approach operation control executed by the control device 100 will be described with reference to the flowchart of Fig. 10. The process shown in the flowchart of Fig. 10 is started when a completion condition for path following traveling is met, and is repeatedly executed at a predetermined control period.

[0106] As shown in FIG. 10, in step S100, the position calculation unit 31 acquires information from the bending angle sensor 72, the object detection sensor 73, and the input device 76, and calculates the positions of the center between the front wheels 4ac, the center between the rear wheels 4bc, the hopper 20, and the bucket 3 based on the acquired information, and then proceeds to step S104.

[0107] In step S104, the waypoint calculation unit 37 determines whether or not the approach condition to the hopper 20 is met. If it is determined in step S104 that the approach condition to the hopper 20 is met, the process proceeds to step S112, and if it is determined that the approach condition to the hopper 20 is not met, the process proceeds to step S108.

[0108] In step S108, the control device 100 controls the alarm device 75 to issue a warning. The warning issued by the alarm device 75 includes information that the approachable condition has not been met and information requesting operator intervention. When the warning process (S108) is completed, the process returns to step S100.

[0109] In step S112, the waypoint calculation unit 37 calculates the position of the waypoint P1. When the calculation process for the waypoint P1 (step S112) is completed, the control device 100 starts alignment control (steps S116 to S136). In step S116, the alignment completion determination unit 40 determines whether the current position of the center between the front wheels 4ac calculated in step S100 matches the position of the waypoint P1 calculated in step S112.

[0110] If the alignment completion determination unit 40 determines in step S116 that the position of the front wheel center 4ac does not match the position of the waypoint P1, the process proceeds to step S120. In step S120, the target value calculation unit 43 calculates a target articulation angle, and the process proceeds to step S122. The target articulation angle is calculated based on the front wheel center 4ac and the rear wheel center 4bc calculated in step S100, and the arc C1 passing through the waypoint P1 calculated in step S112. In step S122, the vehicle control unit 44 acquires information about the current articulation angle detected by the articulation angle sensor 72, and the process proceeds to step S124. In step S124, the vehicle control unit 44 determines whether the current articulation angle matches the target articulation angle.

[0111] If it is determined in step S124 that the current bending angle does not match the target bending angle, the process proceeds to step S128. In step S128, the vehicle control unit 44 changes the bending angle by controlling the steering device 19 so that the current bending angle approaches the target bending angle, and the process returns to step S122.

[0112] If it is determined in step S124 that the current bending angle matches the target bending angle, the process proceeds to step S132. In step S132, the target value calculation unit 43 and the vehicle control unit 44 control the engine 50 and the traveling device 28 to move the vehicle body 16 forward at a predetermined vehicle speed V1, and the process proceeds to step S134.

[0113] In step S134, the position calculation unit 31 acquires information from the bending angle sensor 72, the object detection sensor 73, and the input device 76, calculates the center 4ac between the front wheels based on the acquired information, and the process proceeds to step S136.

[0114] In step S136, the alignment completion determination unit 40 determines whether the current position of the center 4ac between the front wheels calculated in step S134 matches the position of the waypoint P1 calculated in step S112. If it is determined in step S136 that the position of the center 4ac between the front wheels does not match the position of the waypoint P1, the process returns to step S132.

[0115] If it is determined in step S116 or step S136 that the position of the center 4ac between the front wheels coincides with the position of the waypoint P1, the control device 100 completes the alignment control and proceeds to step S138.

[0116] When the positioning control is completed, the control device 100 starts the orientation control (steps S138 to S144). In step S138, the relative position calculation unit 38 calculates the angle θ between the center line CL of the hopper 20 and the front body 11, and the process proceeds to step S140.

[0117] In step S140, the azimuth alignment completion determination unit 41 determines whether the formed angle θ calculated in step S138 is equal to or less than the angle threshold value θ0. If it is determined in step S140 that the formed angle θ is greater than the angle threshold value θ0, the process proceeds to step S144. In step S144, the vehicle control unit 44 changes the articulation angle by controlling the steering device 19 so that the formed angle θ approaches 0 (zero), and the process returns to step S138. If it is determined in step S140 that the formed angle θ is equal to or less than the angle threshold value θ0, the control device 100 completes the azimuth alignment control, and the process proceeds to step S148.

[0118] When the alignment control is completed, the control device 100 starts front straight-ahead control (steps S148 to S160). In step S148, the target value calculation unit 43 and the vehicle control unit 44 control the engine 50 and the traveling device 28 to move the vehicle body 16 forward at a predetermined vehicle speed V2, and proceed to step S150. At this time, the vehicle speed V2 is slower than the vehicle speed V1 during the forward travel in the alignment operation (V2 < V1). Thereby, the accuracy of the front straight-ahead operation can be improved.

[0119] In step S150, the relative position calculation unit 38 calculates the angle θ formed between the center line CL of the hopper 20 and the front body 11, and proceeds to step S152.

[0120] In step S152, the front straight-ahead completion determination unit 42 determines whether or not the angle θ calculated in step S150 is less than or equal to the angle threshold value θ0. If it is determined in step S152 that the angle θ is greater than the angle threshold value θ0, the process proceeds to step S156. In step S156, the vehicle control unit 44 changes the bending angle by controlling the steering device 19 so that the angle θ approaches 0 (zero), and returns the process to step S150. If it is determined in step S152 that the angle θ is less than or equal to the angle threshold value θ0, the control device 100 proceeds to step S158.

[0121] In step S158, the relative position calculation unit 38 calculates the position of the control point of the bucket 3 with respect to the discharge position of the hopper 20, and proceeds to step S160. In step S160, the front straight-ahead completion determination unit 42 determines whether or not the position of the control point of the bucket 3 calculated in step S158 coincides with the discharge position. If it is determined in step S160 that the position of the control point of the bucket 3 does not coincide with the discharge position, the process returns to step S148. If it is determined in step S160 that the position of the control point of the bucket 3 coincides with the discharge position, the control device 100 completes the front straight-ahead control and ends the process shown in the flowchart of FIG. 10.

[0122] According to the above-described embodiment, the following advantageous effects are achieved.

[0123] (1) The wheel loader 1 loads excavated material into a hopper (loading target) 20 using the work device 17. The control device 100 calculates the relative position of the vehicle body 16 and the hopper 20 located in front of the vehicle body 16 (S100 in FIG. 10). Based on the shape data of the hopper 20 stored in the nonvolatile memory (storage device) 102 and the calculated relative position, the control device 100 sets a waypoint P1 at a position farther from the hopper 20 than the distance between the front wheel center 4ac, which is the center between the pair of left and right front wheels, and the tip of the bucket 3 (S112 in FIG. 10). The control device 100 controls the operation of the traveling device 28 and the steering device 19 to align the front wheel center 4ac with the set waypoint P1 (S116 to S136 in FIG. 10).

[0124] This configuration makes it possible to provide a wheel loader 1 that can move to the loading position P2 through autonomous driving in a narrow work site over a limited travel distance that is shorter than conventional methods, without coming into contact with the hopper 20. For example, in this embodiment, if the lateral deviation of the hopper 20 from the center line CL at the time path-following travel is completed is approximately 0.5 m, an appropriate approach to the loading position P2 is possible with the relative distance between the center 4ac between the front wheels and the hopper 20 being one vehicle length or less.

[0125] (2) The control device 100 sets a waypoint P1 on the center line CL of the hopper 20, which is an imaginary line extending from the hopper 20 (see FIG. 4(a)). The control device 100 aligns the center line 4ac between the front wheels with the set waypoint P1 (see FIG. 4(b)), and then controls the operation of the steering device 19 while the traveling device 28 is stopped, so that the orientation of the front body 11 is aligned with the center line CL of the hopper 20 (see FIG. 4(c)). After aligning the orientation of the front body 11 with the center line CL of the hopper 20, the control device 100 controls the operation of the traveling device 28 and the steering device 19, so that the front body 11 travels along the center line CL of the hopper 20 (see FIG. 4(d)).

[0126] According to this configuration, the alignment and the front straight-ahead movement can be performed accurately, and the wheel loader 1 can be appropriately positioned at the loading position P2 on the center line CL of the hopper 20.

[0127] (3) The control device 100 makes the vehicle speed V2 when the front body 11 travels along the center line CL of the hopper 20 slower than the vehicle speed V1 when the center 4ac between the front wheels is made to coincide with the set via point P1 (V2 < V1). Thereby, the front straight-ahead and the alignment of the wheel loader 1 with respect to the loading position P2 can be accurately performed. Further, even when the lift arm 2 is raised during the front straight-ahead movement, the vehicle body 16 can be stably approached to the hopper 20.

[0128] (4) The control device 100 determines whether or not the condition for being able to approach the hopper 20 is satisfied based on the bending angle of the vehicle body 16 detected by the bending angle sensor 72, the shape data of the hopper 20 stored in the nonvolatile memory 102, and the calculated relative position between the hopper 20 and the vehicle body 16. When the condition for being able to approach is satisfied (Yes in S104 of FIG. 10), the control device 100 operates the steering device 19 and the traveling device 28 so that the center 4ac between the front wheels coincides with the via point P1 (S112 to S136 in FIG. 10). When the condition for being able to approach is not satisfied (No in S104 of FIG. 10), the control device 100 controls the notification device 75 to cause the notification device 75 to notify that the condition for being able to approach is not satisfied (S108 in FIG. 10). In this case, the control device 100 does not bend and travel the vehicle body 16 by autonomous driving and maintains the stopped state.

[0129] The condition for being able to approach includes that it is possible to make the center 4ac between the front wheels coincide with the via point P1 by the operation of the steering device 19 and the forward movement by the traveling device 28, and that it is possible to align the direction of the front body 11 along the center line CL of the hopper 20 by operating the steering device 19 while stopping the traveling device 28 in a state where the center 4ac between the front wheels coincides with the via point P1.

[0130] With this configuration, for example, when path following traveling is completed, the operator can know that approach to the hopper 20 is not possible. The operator manually operates the wheel loader 1, for example, to move the vehicle body 16 closer to the center line CL of the hopper 20, or to move the vehicle body 16 away from the hopper 20. After manually operating the wheel loader 1, the operator operates an autonomous driving return button (not shown). This causes the control device 100 to again execute the processing of steps S100 and S104 in FIG. 10, and if it is determined in step S104 that the approach possible condition is met, executes positioning control (S112 to S136), orientation alignment control (S138 to S140), and front straight running control (S148 to S160).

[0131] Therefore, even if it is not possible for the vehicle body 16 to approach the hopper 20 through autonomous driving when the path-following driving is completed, the operator can assist the vehicle body 16, which can then be driven autonomously to move to the loading position P2 and load the excavated material into the hopper 20.

[0132] (5) The control device 100 stores in advance a table of contact prevention characteristic curves that define the relationship between the angle θ formed between the center line CL of the hopper 20 and the front body 11 when the center line 4ac between the front wheels coincides with the waypoint P1, and the position of the waypoint P1 at which the orientation of the front body 11 can be aligned with the center line CL of the hopper 20 without causing the bucket 3 to come into contact with the hopper 20 from the state in which the center line 4ac between the front wheels coincides with the waypoint P1 (see line A in FIG. 9). Before aligning the center line 4ac between the front wheels with the waypoint P1, the control device 100 calculates the relationship (see line B in FIG. 9) between the angle θ formed when the center line 4ac between the front wheels is positioned at an assumed point, which is an assumed waypoint, and the position of the assumed point (in this embodiment, the distance from the hopper 20 to the assumed point) when the center line 4ac between the front wheels coincides with the waypoint P1. The control device 100 sets a waypoint P1 that aligns the center 4ac between the front wheels through a positioning operation based on the relationship between the calculated angle θ and the position of the assumed point (see line I in Figure 9) and the table of contact prevention characteristic curves (see line A in Figure 9).

[0133] In this configuration, a table of contact prevention characteristic curves is stored in advance, so there is no need to calculate the contact prevention characteristic curves each time. Therefore, according to this embodiment, the calculation load can be reduced compared to a configuration in which the contact prevention characteristic curves are calculated each time. In addition, the waypoint P1 can be set as close to the hopper 20 as possible, making it easy to perform the positioning operation.

[0134] (6) The wheel loader 1 is equipped with an object detection sensor 73 attached to the vehicle body 16 and detecting the hopper 20 in front of the vehicle body 16, and an input device 76 that inputs the distance from the bending center (center pin 13) of the front body 11 and the rear body 12 to the center 4ac between the front wheels, the distance from the bending center (center pin 13) of the front body 11 and the rear body 12 to the center 4bc between the rear wheels, and the mounting position (installation position) of the object detection sensor 73 as input information to the control device 100.

[0135] According to this configuration, when the mounting position of the object detection sensor 73 is changed, the operator operates the input device 76 to input the mounting position of the object detection sensor 73 to the control device 100. This allows the control device 100 to accurately perform an approach operation to the hopper 20 through autonomous operation based on the newly input mounting position of the object detection sensor 73.

[0136] Second Embodiment A wheel loader 1B according to a second embodiment of the present invention will be described with reference to Figures 11 and 12. Note that components that are the same as or equivalent to those described in the first embodiment will be given the same reference symbols, and differences will be mainly described.

[0137] 11 is a side view showing a wheel loader 1B according to a second embodiment of the present invention approaching a hopper 20B. In the first embodiment, the object detection sensor 73 was attached to the vehicle body 16 of the wheel loader 1. In contrast, in the second embodiment, the object detection sensor 73B is attached to the roof 20c of the hopper 20B.

[0138] The object detection sensor 73B is, for example, a LiDAR, and detects objects around the hopper 20B. In the state shown in Fig. 11, the object detection sensor 73B detects the position and shape of the bucket 3 and front body 11 of the wheel loader 1B. The object detection sensor 73B is equipped with a communication device that transmits the detection results to the control device 100 of the wheel loader 1 by wireless communication.

[0139] Fig. 12 is a functional block diagram of a control device 100B according to the second embodiment. As shown in Fig. 12, in the second embodiment, a wheel-to-wheel center calculation unit 33B and a bucket position calculation unit 35B function as a position calculation unit 31B that calculates the positions of each part of the wheel loader 1.

[0140] The wheel loader 1B is equipped with a communication device 79 that receives information transmitted from the object detection sensor 73B. The communication device 79 is a wireless communication device that can directly communicate wirelessly with the communication device of the object detection sensor 73B, and has a communication interface that includes a communication antenna with a sensitivity band of, for example, the 2.4 GHz band. The control device 100B according to the second embodiment acquires the detection results of the object detection sensor 73B via the communication device 79.

[0141] In response to an operation by the operator, the input device 76 inputs the distance from the bending center (center pin 13) of the vehicle body 16 to the center 4ac between the front wheels, the distance from the bending center (center pin 13) of the vehicle body 16 to the center 4bc between the rear wheels, and the relative position of the object detection sensor 73 relative to the entrance position of the hopper 20 to the control device 100B as the mounting position (installation position) of the object detection sensor 73B. Note that the nonvolatile memory 102 of the control device 100B stores relative position data of each part (such as the four corners of the top opening of the hopper 20) based on the entrance position of the hopper 20 as shape data of the hopper 20.

[0142] The bucket position calculation unit 35B calculates the relative positions of the hopper 20 and the bucket 3 using the detection results of the object detection sensor 73B and input information from the input device 76. In addition, the bucket position calculation unit 35B extracts the right tip BR and left tip BL of the bucket 3 to calculate the angle (angle θ) of the front body 11 with respect to the center line CL of the hopper 20.

[0143] The wheel center calculation unit 33B calculates the relative positions of the hopper 20 and the front wheel center 4ac and the hopper 20 and the rear wheel center 4bc using the detection results of the object detection sensor 73B, the detection results of the bending angle sensor 72, and input information from the input device 76.

[0144] Other functions of the control device 100B according to the second embodiment are similar to those of the control device 100 according to the first embodiment, and therefore description thereof will be omitted.

[0145] As described above, in the second embodiment, the communication device 79 functions as a relative position acquisition device that acquires relative position information between the hopper 20 and the bucket 3. In the first embodiment, the object detection sensor 73 is attached to the wheel loader 1 as a relative position acquisition device, and therefore the object detection sensor 73 may malfunction due to vibrations while the wheel loader 1 is traveling or working. In contrast, in the second embodiment, the object detection sensor 73B is attached to the hopper 20, which is a fixed object, and therefore the risk of the object detection sensor 73B malfunctioning due to vibrations can be reduced.

[0146] The following modified examples are also within the scope of the present invention, and it is possible to combine the configuration shown in the modified example with the configuration described in the above embodiment, to combine the configurations described in the different embodiments above, or to combine the configurations described in the different modified examples below.

[0147] <Variation 1> In the above embodiment, an example has been described in which the control device 100 calculates the position of the bucket 3 relative to a reference point of the vehicle body 16 (for example, the center pin 13 or the center between the front wheels 4ac) based on the detection results of the object detection sensor 73. That is, in the above embodiment, an example has been described in which the object detection sensor 73 functions as a bucket position acquisition device that acquires the position of the bucket 3. However, the present invention is not limited to this. The control device 100 may calculate the position of the bucket 3 relative to a reference point of the vehicle body 16 based on the angle of the lift arm 2 with respect to the vehicle body 16 detected by the arm angle sensor, the angle of the bucket 3 with respect to the lift arm 2 detected by the bucket angle sensor, and the bending angle detected by the bending angle sensor 72. In this case, the arm angle sensor, the bucket angle sensor, and the bending angle sensor 72 function as a bucket position acquisition device that acquires the position of the bucket 3.

[0148] <Variation 2> In the above embodiment, an example has been described in which the control device 100 calculates the relative position of the vehicle body 16 and the hopper 20 based on the detection results of the object detection sensor 73. That is, in the above embodiment, an example has been described in which the object detection sensor 73 functions as a relative position information acquisition device that acquires relative position information of the hopper 20 with respect to the vehicle body 16. However, the present invention is not limited to this. The control device 100 may calculate the relative position of the vehicle body 16 and the hopper 20 based on the position and orientation (heading) of the vehicle body 16 detected by the position detection device 71 and the position and orientation of the hopper 20 and shape data of the hopper 20 stored in advance in the non-volatile memory 102 by the input device 76. In this case, the input device 76 functions as a relative position information acquisition device that acquires relative position information of the hopper 20 with respect to the vehicle body 16.

[0149] <Variation 3> The method for determining whether the approach condition is met is not limited to the method described in the above embodiment. Alternatively, multiple candidate waypoints may be calculated within a predetermined range on the center line CL of the hopper 20, and an arc C1 may be calculated for each of the candidate waypoints. If the calculated arcs C1 include an arc C1 whose radius is equal to or greater than the minimum turning radius of the vehicle and intersects with arc A3A4, it may be determined that the approach condition is met. The minimum turning radius is stored in non-volatile memory 102.

[0150] <Variation 4> In the first embodiment, an example has been described in which the object detection sensor 73 is provided on the wheel loader 1, and in the second embodiment, the object detection sensor 73B is provided on the hopper 20, but the present invention is not limited to this. The object detection sensor 73B may also be provided at a position a predetermined distance away from the hopper 20. When the object detection sensor 73B is provided external to the wheel loader 1, as in the second embodiment and this modified example, the control device of the wheel loader 1 acquires the detection results of the object detection sensor 73B by wireless communication via the communication device 79, and calculates the relative position of the vehicle body 16 of the wheel loader 1 and the hopper 20 based on the detection results of the object detection sensor 73B. By providing the object detection sensor 73B external to the wheel loader 1, it is possible to reduce the risk of the object detection sensor 73B failing due to vibration.

[0151] <Variation 5> The configuration of the wheel loaders 1, 1B is not limited to the examples described in the above embodiments. The wheel loaders 1, 1B may be configured to include, for example, a generator motor mechanically connected to the engine 50, and a traveling motor that is rotationally driven by the electricity generated by the generator motor and operates the traveling device. In other words, the wheel loaders 1, 1B may be equipped with a hybrid power transmission mechanism that converts the power of the engine 50 into electricity and transmits it to the wheels 4. The wheel loader may also be equipped with an HST (Hydro Static Transmission) power transmission mechanism that converts the power of the engine 50 into hydraulic power and transmits it to the wheels 4.

[0152] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments. [Explanation of symbols]

[0153] 1,1B...wheel loader, 2...lift arm, 3...bucket, 4a...front wheel, 4ac...center between front wheels, 4b...rear wheel, 4bc...center between rear wheels, 7...arm cylinder (hydraulic cylinder), 8...bucket cylinder (hydraulic cylinder), 11...front body, 12...rear body, 13...center pin, 14...steering cylinder (hydraulic cylinder), 16...vehicle body, 17...working device, 18...brake device, 19...steering device, 20,20B...hopper (loading object), 20a...side wall, 20af...front side wall, 20c...roof, 22...travel path, 23...node, 28...traveling device, 31,31B...position calculation unit, 32...motion calculation unit, 33,33B...wheel center calculation unit, 34...hopper position calculation unit, 3 5, 35B...Bucket position calculation unit, 37...Way point calculation unit, 38...Relative position calculation unit, 40...Position alignment completion determination unit, 41...Orientation alignment completion determination unit, 42...Front straight driving completion determination unit, 43...Target value calculation unit, 44...Vehicle control unit, 50...Engine, 60A, 60B, 60C...Hydraulic pump, 61...Front control unit, 62...Brake control unit, 63...Steering control unit, 64...Transmission control unit, 65...Engine control unit, 71...Position detection device, 72...Bending angle sensor, 73, 73B...Object detection sensor, 74...Vehicle speed sensor, 75...Alarm device, 76...Input device, 79...Communication device, 100, 100B...Control unit, 101...Processing unit, 102...Non-volatile memory, 103...Volatile memory

Claims

1. a vehicle body in which a front body having a pair of left and right front wheels and a rear body having a pair of left and right rear wheels are bendably connected; a working device having a lift arm rotatably provided on the front body and a bucket rotatably provided on the lift arm; a traveling device that causes the vehicle body to travel; a steering device that changes the bending angle by bending the vehicle body and steers the vehicle; a control device that controls the operation of the traveling device and the steering device, In a wheel loader that performs work of loading excavated material excavated by the working device onto a loading object, a storage device that stores shape data of the loading object; a bending angle sensor for detecting a bending angle of the vehicle body; an alarm device, The control device Calculating a relative position between the loading object located in front of the vehicle body and the vehicle body; based on the shape data of the loading object stored in the storage device and the calculated relative position, set a waypoint on a virtual straight line extending from the loading object, at a position farther away from the loading object than the distance between the center between the pair of left and right front wheels and the tip end of the center in the width direction of the bucket; Controlling the operation of the traveling device and the steering device to align the center between the front wheels with the set waypoint; After aligning the center between the front wheels with the set waypoint, the operation of the steering device is controlled with the traveling device stopped to make the direction of the front body follow the virtual straight line; After aligning the direction of the front body along the imaginary straight line, controlling the operations of the traveling device and the steering device to move the front body straight along the imaginary straight line; The control device determining whether or not a condition for enabling access to the loading object is established based on the bending angle of the vehicle body detected by the bending angle sensor, the shape data of the loading object stored in the storage device, and the calculated relative position of the loading object and the vehicle body; When the approachable condition is satisfied, the steering device and the traveling device are operated so that the center between the front wheels is aligned with the waypoint; If the approachable condition is not satisfied, the notification device is controlled to notify the fact that the approachable condition is not satisfied by the notification device; The accessibility condition is: The center of the front wheels can be aligned with the waypoint by the operation of the steering device and the forward travel of the traveling device; and After the center between the front wheels is aligned with the waypoint, the steering device is operated while the traveling device is stopped, thereby making it possible to make the direction of the front body follow the virtual straight line. A wheel loader characterized by:

2. a vehicle body in which a front body having a pair of left and right front wheels and a rear body having a pair of left and right rear wheels are bendably connected; a working device having a lift arm rotatably provided on the front body and a bucket rotatably provided on the lift arm; a traveling device that causes the vehicle body to travel; a steering device that changes the bending angle by bending the vehicle body and steers the vehicle; a control device that controls the operation of the traveling device and the steering device, In a wheel loader that performs work of loading excavated material excavated by the working device onto a loading object, a storage device that stores shape data of the loading object; The control device Calculating a relative position between the loading object located in front of the vehicle body and the vehicle body; based on the shape data of the loading object stored in the storage device and the calculated relative position, set a waypoint on a virtual straight line extending from the loading object, at a position farther away from the loading object than the distance between the center between the pair of left and right front wheels and the tip end of the center in the width direction of the bucket; Controlling the operation of the traveling device and the steering device to align the center between the front wheels with the set waypoint; After aligning the center between the front wheels with the set waypoint, the operation of the steering device is controlled with the traveling device stopped to make the direction of the front body follow the virtual straight line; After aligning the direction of the front body along the imaginary straight line, controlling the operations of the traveling device and the steering device to move the front body straight along the imaginary straight line; the control device has stored in advance a table that defines a relationship between an angle formed by the virtual line and the front body when the center between the front wheels coincides with the waypoint, and a position of the waypoint at which the orientation of the front body can be aligned with the virtual line without causing the bucket to come into contact with the object to be loaded from a state in which the center between the front wheels coincides with the waypoint, The control device before aligning the center between the front wheels with the waypoint, calculating a relationship between the angle formed when the center between the front wheels is positioned at a hypothetical point that is a hypothetical waypoint and the position of the hypothetical point based on the current position of the vehicle body and the position of the loading object, The waypoint is set based on the relationship between the calculated angle and the position of the assumed point and the table. A wheel loader characterized by:

3. The wheel loader according to claim 1 or 2, The control device calculates the relative position based on the detection result of an object detection sensor provided on the wheel loader or the detection result of an object detection sensor provided outside the wheel loader. A wheel loader characterized by:

4. The wheel loader according to claim 2, a bending angle sensor for detecting a bending angle of the vehicle body; an alarm device, The control device determining whether or not a condition for enabling access to the loading object is established based on the bending angle of the vehicle body detected by the bending angle sensor, the shape data of the loading object stored in the storage device, and the calculated relative position of the loading object and the vehicle body; When the approachable condition is satisfied, the steering device and the traveling device are operated so that the center between the front wheels is aligned with the waypoint; If the approachable condition is not satisfied, the notification device is controlled to notify the fact that the approachable condition is not satisfied by the notification device; The accessibility condition is: The center of the front wheels can be aligned with the waypoint by the operation of the steering device and the forward travel of the traveling device; and After the center between the front wheels is aligned with the waypoint, the steering device is operated while the traveling device is stopped, thereby making it possible to make the direction of the front body follow the virtual straight line. A wheel loader characterized by:

5. The wheel loader according to claim 1 or 2, The control device slows down the vehicle speed when the front body travels along the virtual straight line compared to the vehicle speed when the center between the front wheels is aligned with the set waypoint. A wheel loader characterized by:

6. The wheel loader according to claim 1, the control device has stored in advance a table that defines a relationship between an angle formed by the virtual line and the front body when the center between the front wheels coincides with the waypoint, and a position of the waypoint at which the orientation of the front body can be aligned with the virtual line without causing the bucket to come into contact with the object to be loaded from a state in which the center between the front wheels coincides with the waypoint, The control device before aligning the center between the front wheels with the waypoint, calculating a relationship between the angle formed when the center between the front wheels is positioned at a hypothetical point that is a hypothetical waypoint and the position of the hypothetical point based on the current position of the vehicle body and the position of the loading object, The waypoint is set based on the relationship between the calculated angle and the position of the assumed point and the table. A wheel loader characterized by:

7. The wheel loader according to claim 3, an input device that inputs, as input information to the control device, the distance from the bending center of the front body and the rear body to the center between the front wheels, the distance from the bending center to the center between the pair of left and right rear wheels, and the installation position of the object detection sensor. A wheel loader characterized by:

Images