JP7798703B2 - Wheel loader - Google Patents

Description

The present invention relates to a wheel loader that can travel automatically.

Autonomously traveling wheel loaders are known articulated work vehicles that have a vehicle body with a flexibly connected front and rear body and a working device attached to the vehicle body. Wheel loaders excavate soil and sand using the working device, transport the excavated material to a loading position in front of a loading object such as a hopper, and then release the excavated material into the top opening of the hopper, which is the loading object. As the wheel loader moves to the loading position, the operation of each part of the wheel loader must be controlled so that the working device reaches the loading position without coming into contact with the loading object.

Patent Document 1 proposes a control device that aims to achieve smooth autonomous driving while maintaining the driving accuracy of an articulated work vehicle (vibratory 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."

Japanese Patent Application Laid-Open No. 2017-204089

Meanwhile, wheel loaders sometimes operate in narrow work sites. In narrow work sites, the space and travel distance for changing direction and correcting the wheel loader's direction are limited, and changes in direction and corrections reduce work efficiency. Furthermore, if a misalignment occurs between the vehicle body and the object being loaded, a steering operation is required to correct 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 wheel loaders that can move the vehicle body to an appropriate loading position within a limited travel distance, such as in narrow work sites. Patent Document 1 discloses control details for correcting lateral deviation of the vehicle body from the travel reference line when performing compaction using a vibrating roller, but does not disclose control details for moving the vehicle body to a predetermined position while avoiding contact with objects such as the object being loaded.

The object of the present invention is to provide a wheel loader that can travel to a loading position within a limited distance through autonomous driving.

A wheel loader according to a first 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 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 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 stores shape data of the loading object. The control device is provided with a storage device, a bending angle sensor that detects the bending angle of the vehicle body, and an alarm device , and the control device calculates a relative position between the vehicle body and the object to be loaded that is located in front of the vehicle body, and based on shape data of the object to be loaded stored in the storage device and the calculated relative position, sets a waypoint on an imaginary line extending from the object to be loaded that is at a position farther away from the object to be loaded 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 tip end of the center in the width direction of the bucket, and controls the operation of the traveling device and the steering device to align the center between the front wheels with the set waypoint , and aligns the front wheel center with the set waypoint. After the inter-wheel centers are aligned, the operation of the steering device is controlled with the traveling device stopped to orient the front body along the imaginary straight line, and after orienting the front body along the imaginary straight line, the operation of the traveling device and the steering device is controlled to move the front body 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 if the approachable condition is met, The steering device and the traveling device are operated so as to align the center between the front wheels with the waypoint, and if the approachable condition is not met, the notification device is controlled to cause the notification device to notify that the approachable condition is not met, and the approachable condition includes that the center between the front wheels can be aligned with the waypoint by operating the steering device and traveling forward with the traveling device, and that after the center between the front wheels is aligned with the waypoint, the steering device can be operated while the traveling device is stopped to make the direction of the front body follow the virtual straight line.
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 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 to steer, and a control device that controls the operation of the traveling device and the steering device, and is a wheel loader that performs work of loading material excavated by the working device onto a loading object. The wheel loader is provided with a storage device that stores shape data of the object to be loaded, and the control device calculates a relative position between the object to be loaded, which is located in front of the vehicle body, and the vehicle body, and sets a waypoint on an imaginary line extending from the object to be loaded, at a position farther away from the object to be loaded 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, based on the shape data of the object to be loaded stored in the storage device and the calculated relative position, and controls the operation of the traveling device and the steering device to move the object to the set waypoint and after aligning the center between the front wheels with the set waypoint, controlling the operation of the steering device while the traveling device is stopped to make the front body align with the imaginary straight line, and after aligning the front body with the imaginary straight line, controlling 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 stores information on an angle between the imaginary straight line and the front body in a state where the center between the front wheels is aligned with the waypoint, and a time when the center between the front wheels is aligned with the waypoint. A table specifying the relationship between the position of the waypoint and the position of the waypoint at which the orientation of the front body can be aligned with the virtual straight line without the bucket coming into contact with the object to be loaded from the state where the bucket is in the waypoint is stored in advance, and the control device calculates, based on the current position of the vehicle body and the position of the object to be loaded, the relationship between the angle formed when the center of the front wheels is positioned at an assumed point that is an assumed waypoint and the position of the assumed point, before aligning the center of the front wheels with the waypoint, and sets the waypoint based on the calculated relationship between the angle and the position of the assumed point and the table.

The present invention provides a wheel loader that can travel to a loading position within a limited distance through autonomous driving.

FIG. 1 is a side view of a wheel loader according to the first embodiment. FIG. 2 is a system configuration diagram of a wheel loader. FIG. 3 is a diagram illustrating the path following travel of the wheel loader. 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. FIG. 5 is a diagram illustrating the hardware configuration of the control device. FIG. 6 is a functional block diagram of the control device according to the first embodiment. 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. FIG. 8 is a diagram illustrating an example of a method for determining whether or not the conditions for allowing access to the hopper are met. FIG. 9 is a diagram illustrating an example of a method for setting a waypoint. FIG. 10 is a flowchart illustrating an example of the flow of approaching operation control executed by the control device. FIG. 11 is a side view showing the wheel loader according to the second embodiment approaching the hopper. FIG. 12 is a functional block diagram of a control device according to the second embodiment.

The following describes a wheel loader according to an embodiment of the present invention, with reference to the drawings.

First Embodiment
- Overall configuration of 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 the rear body 12 are connected by a center pin 13 so as to be able to bend in the left-right direction.

The wheel loader 1 is equipped with a steering device 19 that steers by bending the vehicle body 16 around the center pin 13 to change 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 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.

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

An alarm device 75 is provided in the driver's cab 5 to notify the operator of warnings and other information. The alarm device 75 is, for example, a display device such as a liquid crystal display device that notifies warnings using images, or an audio output device such as a speaker that notifies warnings using audio.

The working device 17 is attached to the front body 11. The working device 17 includes a lift arm 2 mounted on the front body 11 so as to be rotatable in the vertical direction, a bucket 3 mounted on 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 arm cylinder 7 are mounted one on each side of the front body 11. The bucket 3 rotates as the bucket cylinder 8 expands and contracts via a bell crank 9 and a bucket link 10, thereby raising and lowering the orientation of the bucket 3.

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

The wheel loader 1 is steered by the relative rotation of the front body 11 and rear body 12 caused by the extension and retraction 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. Note that in this specification, the bending angle corresponds to the angle of rotation around the center pin 13. The bending angle is 0 (zero) degrees when the vehicle is not bent, i.e., when the wheel loader 1 is in a straight-ahead position. The bending angle takes a positive value when the vehicle body 16 is bent to the right, and a negative value when the vehicle body 16 is bent to the left.

An object detection sensor 73 that detects objects in front of the vehicle body 16 is attached to the top of the driver's cab 5. A bending angle sensor 72 that detects the bending angle of the vehicle body 16 is attached to the center pin 13.

- 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 the 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.

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.

The wheel loader 1 is equipped with a front control unit 61 that controls the operation of the work implement 17, a brake control unit 62 that controls the operation of the brake device 18, and a steering control unit 63 that controls the operation of the steering device 19.

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, for example, 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 amount of fuel injection so that the actual rotational speed detected by the engine rotational speed sensor approaches the target rotational speed calculated by the control device 100.

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

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.

The input shaft of the 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 the transmission 52. The torque converter 51 is a well-known fluid clutch consisting 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 shifts its speed 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. After the change in speed, the rotation is transmitted to the wheels 4 via the propeller shaft 53, differential device 54, and axles 55, allowing the wheel loader 1 to travel.

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.

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

The pressure, flow rate, and flow direction of hydraulic oil supplied from the hydraulic pump 60A to the arm cylinder 7 and bucket cylinder 8 are controlled by the front control unit 61. This allows the work device 17 to perform excavation and loading operations. The pressure, flow rate, and flow direction of hydraulic oil supplied from the hydraulic pump 60B to the brake cylinder 18a and parking brake cylinder 18b are controlled by the brake control unit 62. This allows the brake device 18 to brake and stop the vehicle body 16. 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. This allows the steering device 19 to steer the vehicle body 16.

As shown in FIG. 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 representing the detection result to the control device 100. The position detection device 71 includes, 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 the global coordinate system based on satellite signals (GNSS radio waves) from multiple positioning satellites received by the GNSS antenna.

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 on the rear body 12 (for example, the position of the center pin 13) and the orientation (direction) of the rear body 12.

However, the position detection device 71 is not limited to this, and may also be equipped with a wheel speed sensor that detects the rotational speed of the wheels 4 and a gyro sensor. 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.

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 attached to the center pin 13. It 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 the bending angle sensor 72 that detects the bending angle of the vehicle body 16 may also be a stroke sensor that detects the stroke amount of the steering cylinder 14. 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.

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

An example of work performed by the wheel loader 1 will be described below. The wheel loader 1 moves forward toward the natural ground that is the object to be excavated, plunges the bucket 3 into the ground, and operates the bucket 3 and lift arm 2 to perform excavation work by excavating 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 cargo (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.

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 Figure 5). The control device 100 controls the travel 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). At the excavation position, the control device 100 controls the working device 17, causing the working device 17 to perform excavation work. At the loading position, the control device 100 controls the working device 17, causing the working device 17 to perform loading work.

- Path-following driving -
After the excavation work is completed, the wheel loader 1 performs path-following travel by autonomous driving. Figure 3 is a diagram illustrating path-following travel 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 Figure 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 travel path 22. In the following, the control executed by the control device 100 to travel the vehicle body 16 along the travel path 22 will also be referred to as path-following travel control.

The driving route 22 is specified by a plurality of nodes 23 stored in the non-volatile memory 102 (see Figure 5). The nodes 23 are data indicating coordinates on the driving route 22. The control device 100 may cause the vehicle body 16 to autonomously drive so as to minimize the deviation between a reference point of the vehicle body 16 (e.g., the center between the front wheels 4ac) and the driving route 22, or may cause the vehicle body 16 to autonomously drive so that the reference point of the vehicle body 16 (e.g., the center between the front wheels 4ac) passes through a node 23.

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 Figure 5). The control device 100 controls the driving 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.

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 whose origin is a predetermined position on the work site. 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.

- Approaching 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, the completion of the positioning operation, the completion of the orientation adjustment operation, and the completion of the front straight movement operation.

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. When loading 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 loading position P2 and perform loading operations without coming into contact with the side walls 20a of the hopper 20.

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

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.

- Alignment operation -
Figure 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 Figure 3) that defines the end of the travel path 22, which is set as the stopping target point. The final node 23a is set just before the loading position into the hopper 20.

When the completion condition for path-following travel is met, the control device 100 terminates the path-following travel 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 travel is met when the distance between the final node 23a and the reference point of the wheel loader 1 (e.g., the center between the front wheels 4ac) is equal to or less than a predetermined distance threshold and the vehicle body 16 is stopped.

Approach operation control includes position alignment control, heading alignment control, and front straight ahead control. As shown in Figure 4(a), when the completion condition for path following driving is met, the control device 100 executes position alignment control in the approach operation control.

During alignment 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 the relative distance x1 between the hopper 20 and the vehicle body 16. Based on the shape data of the hopper 20 stored in the non-volatile memory 102 (see Figure 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 away from the hopper 20 that is greater than the distance x0 between the center between the front wheels 4ac 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. Based on the detection results of the object detection sensor 73, the control device 100 extracts multiple characteristic points of the hopper 20 and stores the extracted multiple characteristic points as shape data of the hopper 20 in the non-volatile memory 102 (see Figure 5).

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.

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

- Orientation adjustment operation -
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 between the front wheels 4ac with the waypoint P1, the control device 100 ends the positioning control and executes orientation alignment control. In orientation alignment 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 alignment 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.

- 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 front straight running control.

In front straight traveling control, the control device 100 controls the operation of the engine 50, the travel 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 front straight traveling control, the control device 100 also raises 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.

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

As described above, after completing path-following travel, the control device 100 executes approach operation control to move the wheel loader 1 via waypoint P1 to loading position P2. Details of this approach operation control will be described later.

- Hardware configuration of the control device -
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 as a computer including a processing device 101 such as a central processing unit (CPU), a micro processing unit (MPU), or a digital signal processor (DSP), a non-volatile memory 102 such as a read-only memory (ROM), a flash memory, or a hard disk drive, a volatile memory 103 called a random access memory (RAM), an input interface 104, an output interface 105, and other peripheral circuits. The control device 100 may be configured as a single 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.

The non-volatile memory 102 stores programs capable of executing various calculations, as well as data such as thresholds used in the calculations. In other words, the non-volatile memory 102 is a storage device (storage medium) that can read programs that implement the functions of this embodiment. The processing device 101 is an arithmetic processing device that loads the programs stored in the non-volatile 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 non-volatile memory 102, and the volatile memory 103 in accordance with the programs.

The input interface 104 converts signals input from the position detection device 71, bending angle sensor 72, object detection sensor 73, vehicle speed sensor 74, and input device 76 into data that can be calculated by the processing device 101. The output interface 105 also generates output signals based on the calculation results of the processing device 101, and outputs these signals to solenoid valves that control the operation of hydraulic equipment (hydraulic pumps, hydraulic actuators), alarm devices 75, etc.

The object detection sensor 73 is, for example, a LiDAR. Instead of a LiDAR, millimeter-wave radar, laser radar, a stereo camera, etc. may also be used as the object detection sensor 73.

-Control device functions-
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.

-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 positions of the various parts of the wheel loader 1 .

The wheel center calculation unit 33 calculates the position of the front wheel center 4ac and 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.

In response to operator operation, the input device 76 inputs the following information (input data) to the control device 100: the distance from the bending 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 bending 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 mounting 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 non-volatile memory 102. The input of relative positions using the input device 76 is performed at the time of manufacture (shipment) and when a misalignment occurs in the positions of various parts due to deterioration over time.

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 (e.g., 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), and the four corners of the top opening of the hopper 20.

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 (e.g., the center pin 13, the center between the front wheels 4ac). The characteristic points of the bucket 3 are, for example, the tip (toe) of the bucket 3, and the left and right ends of the bucket 3.

-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.

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 approach to the hopper 20 is possible (i.e., whether 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 travel (current position) to the loading position P2.

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) It is possible to align the center 4ac between the front wheels with the waypoint P1 by operating the steering device 19 and driving forward using the driving device 28.
(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.

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

In this way, the waypoint calculation unit 37 determines whether it is possible to align the front body 11 with the waypoint P1 and whether it is possible to align the orientation of the front body 11 with the center line CL of the hopper 20.

Referring to Figures 7 to 9, the method for calculating waypoint P1 and the method for determining whether the approach conditions are met will be described in detail. Figure 7 is a schematic plan view showing an example of the stopping position and posture of the wheel loader 1 after the alignment operation is complete. Figure 7 also shows the range A0 (hereinafter also referred to as the azimuth alignment area) that the front wheel center 4ac, center pin 13, and rear wheel center 4bc can take, allowing for azimuth alignment after the alignment is complete. The azimuth alignment area A0 is approximately pentagonal.

The orientation adjustment possible area A0 is the area surrounded by the line segment A1A2 connecting points A1 and A2, the line segment A2A3 connecting points A2 and A3, the line segment A1A5 connecting points A1 and A5, the line segment A5A4 connecting points A5 and A4, and the arc A3A4 connecting points A3 and A4. Point A1 corresponds to the position of the center between the front wheels 4ac, which 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 center between the rear wheels 4bc when the bending angle α of the wheel loader 1 is the maximum bending angle αmax.

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

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 extent to the left, 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 extent to the right. The orientation adjustment area A0 shown in Figure 7 is illustrated as an area that takes into account both the cases where the center pin 13 is on the right side and the left side of the hopper 20. For this reason, the orientation adjustment area A0 has an axisymmetric shape with the center line CL of the hopper 20 as the axis of symmetry.

Point A1 is located on waypoint P1, and line segments A2A3 and A5A4 are parallel to the center line CL of the hopper 20. Furthermore, the exterior angles at points A2 and A5 of the orientation adjustment area A0 are each equal to the maximum bending angle αmax of the vehicle body 16. As mentioned above, when the vehicle body 16 is bent while stopped, the positions of the front wheel center 4ac and the rear wheel center 4bc remain almost constant, while the position of the center pin 13 moves left and right. For example, when the front wheel center 4ac, center pin 13, and rear wheel center 4bc are located at points A1, A2, and A3, respectively, the position of the center pin 13 changes as follows: When the vehicle 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, and the front body 11 and the front wall 20af of the hopper 20 face each other directly.

In Figure 7, dashed lines indicate the lines connecting the front wheel center 4ac, center pin 13, and rear wheel center 4bc when the wheel loader 1 has completed its orientation operation, with the front wheel center 4ac, center pin 13, and rear wheel center 4bc located at points A1, A2, and A3. Although not shown, if the front wheel center 4ac, center pin 13, and rear wheel center 4bc are similarly located 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.

In contrast, 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.

As described above, the orientation adjustment possible area A0 indicates the limit of the vehicle body 16's stopping position and posture where the orientation (azimuth) of the front body 11 can be aligned parallel to the center line CL of the hopper 20 after the alignment operation is complete, i.e., where orientation adjustment is possible. In other words, when the alignment operation is complete and the front wheel center 4ac is located at point A1, if the rear wheel center 4bc is located between the line passing through points A2 and A3 and the 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 less than the maximum bending angle, then orientation adjustment can be said to be possible. 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.

With reference to Figure 8, an example of a method for determining whether the conditions for approaching the hopper 20 are met when path-following travel is complete will be described. Figure 8 schematically shows a wheel loader 1 when path-following travel has been completed. Figure 8 also shows the orientation adjustment area A0 when path-following travel is complete, assuming waypoint P1.

After path-following travel is complete, the travel path for aligning the wheel loader 1's front wheel center 4ac 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 front wheel center 4ac, and the rear wheel center 4bc. Because the wheel loader 1 is an articulated vehicle, the front wheel center 4ac and the rear wheel center 4bc pass on arc C1. For this reason, the condition for positioning is that "the radius of arc C1 is greater than or equal to the vehicle's minimum turning radius," and the condition for orientation is that "arc C1 intersects with arcs A3A4."

In other words, if the radius of arc C1 is equal to or greater than the vehicle's minimum turning radius (condition 1) is met, and if the radius of arc C1 is less than the vehicle's minimum turning radius (condition 1) is not met. Furthermore, if arc C1 intersects with arc A3A4 (condition 2) is met, and if arc C1 does not intersect with arc A3A4 (condition 2) is not met.

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.

As shown in Figures 4(b) and 4(c), waypoint P1 must 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 and the hopper 20, at which the bucket 3 does not come into contact with the hopper 20 during the orientation adjustment operation, varies depending on the position of the bucket 3 and the angle θ formed when the alignment 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.

Contact prevention characteristic curve A shown in Figure 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 bucket 3 position is constant, and the angle θ 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 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 bucket 3 position and stored in non-volatile memory 102. Note that the minimum value of distance x defined by contact prevention characteristic curve A is set to a value at least greater than the distance x0 between the center 4ac between the front wheels and the tip of the bucket 3.

As described above, once path-following travel is complete, a travel route (see arc C1 in Figure 8) leading to the assumed point can be determined based on the center between the front wheels 4ac, the center between the rear wheels 4bc, and the assumed waypoint P1. The direction of the tangent to this travel route (arc C1) at the assumed point (waypoint P1) corresponds to the orientation of the front body 11 once path-following travel 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.

In this way, assuming waypoint P1, the angle θ between the center line CL of the hopper 20 and the front body 11 can be determined. Therefore, once the positions of the front wheel center 4ac and the rear wheel center 4bc are determined at the initial position when path-following driving 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.

The waypoint calculation unit 37 calculates the distance x from the hopper 20 to the assumed waypoint P1 (assumed point) based on the center between the front wheels 4ac and the center between the rear wheels 4bc, the position of the hopper 20, and the center line CL of the hopper 20 at the position at the end 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 between the front wheels 4ac coincides with the waypoint P1.

Lines A and C in Figure 9 show examples of allowable bending angle lines. Note that since the angle θ is less than the maximum bending angle, lines A and C extend to the position where the angle θ is the maximum bending angle.

Line B intersects with Line A at Point D. Point D indicates the minimum 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.

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

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 waypoint P1 based on the distance x at that intersection.

If the contact prevention characteristic curve and the allowable bending angle line do not intersect, the waypoint calculation unit 37 determines that the approach condition is not met. If the approach 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 approach 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.

When the waypoint calculation unit 37 sets waypoint P1, the target value calculation unit 43 shown in Figure 6 works in cooperation with the vehicle control unit 44 to perform alignment control to align the center between the front wheels 4ac with waypoint P1.

The relative position calculation unit 38 calculates the relative positions (relative distance and relative angle) of the hopper 20, bucket 3, and front wheel center 4ac based on the calculation results of the wheel center calculation unit 33, hopper position calculation unit 34, and 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 excavated material in 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 bucket 3.

When the position of waypoint P1 is calculated by waypoint calculation unit 37, alignment completion determination unit 40 determines whether the conditions for completing the alignment operation are 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 matches the position of waypoint P1 calculated by waypoint calculation unit 37, alignment completion determination unit 40 determines that the conditions for completing the alignment operation are met.

If the front wheel center 4ac is located within a predetermined range from 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 the distance y from the waypoint P1 to the front wheel center 4ac. If the calculated distance y is less than or equal to 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.

When it is determined that the conditions for completing the alignment operation are met, the alignment completion determination unit 40 outputs a signal indicating completion of the alignment operation to the target value calculation unit 43 and the azimuth alignment completion determination unit 41. Upon receiving the signal indicating completion of 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.

When the azimuth alignment completion determination unit 41 receives the alignment operation completion signal, it determines whether the conditions for completing the azimuth alignment operation are met based on the calculation results of the relative position calculation unit 38. For example, the azimuth alignment completion determination unit 41 determines that the conditions for completing the azimuth alignment operation are 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 less than the angle threshold θ0. If the angle θ is greater than the predetermined angle threshold θ0, the azimuth alignment completion determination unit 41 determines that the conditions for completing the azimuth alignment operation are not met.

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 driving 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 front straight driving control in cooperation with the vehicle control unit 44.

When the front straight ahead movement completion determination unit 42 receives the azimuth alignment operation completion signal, it determines whether the conditions for completing the front straight ahead movement have been met based on the calculation results of the relative position calculation unit 38. For example, the front straight ahead movement completion determination unit 42 determines that the conditions for completing the front straight ahead movement have been met when the bucket 3 is positioned above the hopper 20.

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

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

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

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

The target value calculation unit 43 calculates the target value using the position of waypoint P1 calculated by waypoint calculation unit 37 and the calculation results of the relative position calculation unit 38. The vehicle control unit 44 controls various parts of the vehicle based on the target values calculated by the target value calculation unit 43. For example, the vehicle control unit 44 controls the steering device 19 so that the bending angle detected by the bending angle sensor 72 becomes the target bending angle calculated by the target value calculation unit 43. The vehicle control unit 44 also controls the engine 50 and the traveling device 28 (including the brake device 18) so that the vehicle speed detected by the vehicle speed sensor 74 becomes the target vehicle speed calculated by the target value calculation unit 43. The vehicle control unit 44 also controls the 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.

An example of the flow of approach operation control executed by the control device 100 will be described with reference to the flowchart in Figure 10. The processing shown in the flowchart in Figure 10 is started when the completion condition for path following driving is met, and is executed repeatedly at a predetermined control cycle.

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.

In step S104, the waypoint calculation unit 37 determines whether the conditions for approaching the hopper 20 are met. If it is determined in step S104 that the conditions for approaching the hopper 20 are met, processing proceeds to step S112; if it is determined that the conditions for approaching the hopper 20 are not met, processing proceeds to step S108.

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 indicating that the approach conditions have not been met and a request for operator intervention. When the warning process (S108) is completed, the process returns to step S100.

In step S112, the waypoint calculation unit 37 calculates the position of waypoint P1. When the calculation process for 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 waypoint P1 calculated in step S112.

In step S116, if the alignment completion determination unit 40 determines that the position of the front wheel center 4ac does not match the position of waypoint P1, the process proceeds to step S120. In step S120, the target value calculation unit 43 calculates the 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 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.

If it is determined in step S124 that the current bending angle does not match the target bending angle, processing 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 processing returns to step S122.

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

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 between the front wheels 4ac based on the acquired information, and proceeds to step S136.

In step S136, the alignment completion determination unit 40 determines whether the current position of the center between the front wheels 4ac 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 between the front wheels 4ac does not match the position of the waypoint P1, the process returns to step S132.

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

Once the positioning control is complete, 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 then proceeds to step S140.

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

Once the heading alignment control is complete, the control device 100 initiates front straight ahead control (steps S148 to S160). In step S148, the target value calculation unit 43 and vehicle control unit 44 control the engine 50 and driving device 28 to move the vehicle body 16 forward at a predetermined vehicle speed V2, and the process proceeds to step S150. Note that the vehicle speed V2 at this time is slower than the vehicle speed V1 during forward driving in the position alignment operation (V2 < V1). This improves the accuracy of the front straight ahead operation.

In step S150, 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 then proceeds to step S152.

In step S152, the front straight driving completion determination unit 42 determines whether the angle θ calculated in step S150 is less than or equal to the angle threshold θ0. If it is determined in step S152 that the angle θ is greater than the angle threshold θ0, the process proceeds to step S156. In step S156, the vehicle control unit 44 changes the curvature angle by controlling the steering device 19 so that the angle θ approaches 0 (zero), and the process returns to step S150. If it is determined in step S152 that the angle θ is less than or equal to the angle threshold θ0, the control device 100 proceeds to step S158.

In step S158, the relative position calculation unit 38 calculates the position of the control point of the bucket 3 relative to the discharge position of the hopper 20, and the process proceeds to step S160. In step S160, the front straight traveling completion determination unit 42 determines whether the position of the control point of the bucket 3 calculated in step S158 matches the discharge position. If it is determined in step S160 that the position of the control point of the bucket 3 does not match 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 matches the discharge position, the control device 100 completes the front straight traveling control and ends the process shown in the flowchart in FIG. 10.

The above-described embodiment provides the following advantages:

(1) The wheel loader 1 loads excavated material into a hopper (loading object) 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 non-volatile 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).

This configuration makes it possible to provide a wheel loader 1 that can autonomously drive in a narrow work site, traveling a shorter, more limited distance than conventional methods, to the loading position P2 without coming into contact with the hopper 20. For example, in this embodiment, if the lateral deviation from the center line CL of the hopper 20 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 of the front wheels and the hopper 20 being one vehicle length or less.

(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 between the front wheels 4ac with the set waypoint P1 (see FIG. 4(b)). Then, with the traveling device 28 stopped, the control device 100 controls the operation of the steering device 19 to orient the front body 11 along the center line CL of the hopper 20 (see FIG. 4(c)). After orienting the front body 11 along 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 to cause the front body 11 to travel along the center line CL of the hopper 20 (see FIG. 4(d)).

This configuration allows for accurate orientation and front straight-ahead movement, allowing the wheel loader 1 to be appropriately positioned at loading position P2 on the center line CL of the hopper 20.

(3) The control device 100 slows the vehicle speed V2 when the front body 11 travels along the center line CL of the hopper 20 compared to the vehicle speed V1 when aligning the center between the front wheels 4ac with the set waypoint P1 (V2<V1). This allows for accurate alignment of the wheel loader 1 with respect to the front straight ahead and loading position P2. Furthermore, even when the lift arm 2 is raised during front straight ahead travel, the vehicle body 16 can be brought stably closer to the hopper 20.

(4) The control device 100 determines whether the approach conditions to the hopper 20 are met 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 non-volatile memory 102, and the calculated relative position of the hopper 20 and the vehicle body 16. If the approach conditions are met (Yes in S104 of FIG. 10), the control device 100 operates the steering device 19 and the traveling device 28 to align the center between the front wheels 4ac with the waypoint P1 (S112 to S136 of FIG. 10). If the approach conditions are not met (No in S104 of FIG. 10), the control device 100 controls the notification device 75 to notify the user that the approach conditions are not met (S108 of FIG. 10). In this case, the control device 100 does not bend or travel the vehicle body 16 through autonomous driving, and maintains the stopped state.

The approachable conditions include the ability to align the center line 4ac between the front wheels with the waypoint P1 by operating the steering device 19 and driving forward using the traveling device 28, and the ability to align the direction of the front body 11 with the center line CL of the hopper 20 by operating the steering device 19 while stopping the traveling device 28 with the center line 4ac between the front wheels aligned with the waypoint P1.

With this configuration, for example, once path-following travel is complete, 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 the 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, it executes positioning control (S112 to S136), orientation control (S138 to S140), and front straight ahead control (S148 to S160).

Therefore, even if autonomous driving is not possible to approach the hopper 20 when path-following travel is complete, the operator can provide assistance, allowing the vehicle body 16 to move to loading position P2 using subsequent autonomous driving and load the excavated material into the hopper 20.

(5) The control device 100 pre-stores a table of contact prevention characteristic curves that define the relationship between the angle θ between the center line CL of the hopper 20 and the front body 11 when the center line 4ac between the front wheels is aligned 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 contact the hopper 20 from a state in which the center line 4ac between the front wheels is aligned with the waypoint P1 (see line A in Figure 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 Figure 9) between the angle θ when the center line 4ac between the front wheels is positioned at the hypothetical point, which is a hypothetical waypoint, and the position of the hypothetical point (in this embodiment, the distance from the hopper 20 to the hypothetical point) when the center line 4ac between the front wheels is positioned at the hypothetical point, which is a hypothetical waypoint, based on the current position of the vehicle body 16 and the position of the hopper 20. The control device 100 sets a waypoint P1 that will align the center between the front wheels 4ac through a positioning operation based on the relationship between the calculated angle θ and the position of the assumed point (see line B in Figure 9) and the table of contact prevention characteristic curves (see line A in Figure 9).

In this configuration, a table of contact prevention characteristic curves is stored in advance, eliminating the need to calculate the contact prevention characteristic curves each time. Therefore, this embodiment reduces the computational load compared to a configuration in which the contact prevention characteristic curves are calculated each time. Furthermore, waypoint P1 can be set as close to hopper 20 as possible, making it easier to perform alignment operations.

(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 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 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.

With 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 into the control device 100. This allows the control device 100 to accurately perform autonomous operation to approach the hopper 20 based on the newly input mounting position of the object detection sensor 73.

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.

Figure 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.

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 via wireless communication.

Figure 12 is a functional block diagram of a control device 100B according to the second embodiment. As shown in Figure 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.

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.

In response to operator operation, the input device 76 inputs the distance from the bending center (center pin 13) of the vehicle body 16 to the center between the front wheels 4ac, the distance from the bending center (center pin 13) of the vehicle body 16 to the center between the rear wheels 4bc, 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 non-volatile 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.

The bucket position calculation unit 35B calculates the relative position 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. The bucket position calculation unit 35B also calculates the angle (angle θ) of the front body 11 with respect to the center line CL of the hopper 20 by extracting the right tip BR and left tip BL of the bucket 3.

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.

Other functions of the control device 100B according to the second embodiment are the same as those of the control device 100 according to the first embodiment, and therefore will not be described here.

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 operating. 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.

The following modifications are also within the scope of the present invention, and it is possible to combine the configurations shown in the modifications with the configurations described in the above-mentioned embodiments, to combine the configurations described in the different embodiments above, or to combine the configurations described in the different modifications below.

<Modification 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 (e.g., 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.

<Modification 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 (azimuth) 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 that have been 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.

<Modification 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 the non-volatile memory 102.

<Modification 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, the risk of failure of the object detection sensor 73B due to vibration can be reduced.

<Modification 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.

The above describes embodiments of the present invention, but these embodiments merely illustrate some of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

1, 1B...wheel loader, 2...lift arm, 3...bucket, 4a...front wheels, 4ac...center between front wheels, 4b...rear wheels, 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...Waypoint 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 (7)

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 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: 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: The wheel loader according to claim 1 or 2 ,
a wheel loader, wherein the control device calculates the relative position based on the detection result of an object detection sensor provided in the wheel loader or the detection result of an object detection sensor provided outside the wheel loader. 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 aligning the center between the front wheels with the waypoint, the steering device is operated while the traveling device is stopped, thereby making it possible to align the direction of the front body with the virtual straight line. The wheel loader according to claim 1 or 2,
the control device slows down the vehicle speed when the front body travels along the imaginary straight line compared to the vehicle speed when the center between the front wheels is aligned with the set waypoint. 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,
a wheel loader, wherein the waypoint is set based on the relationship between the calculated angle and the position of the assumed point, and based on the table. The wheel loader according to claim 3,
an input device that inputs to the control device as input information 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 an installation position of the object detection sensor.