Wheel loader

Abstract

To provide a wheel loader capable of performing stable automatic travel along a travel path.SOLUTION: A wheel loader includes: a vehicle body in which a front body and a rear body are connected in a bendable manner; a lift arm which is provided at the front body in a rotatable manner; a bucket which is provided at the lift arm in a rotatable manner; a traveling device which makes the vehicle body travel; a steering device which changes a bent angle by bending the vehicle body and steers; and a control device which generates a traveling path based on a drilling position and a loading position, and controls the traveling device and the steering device so that the vehicle body travels along the travel path. The control device calculates a target bent angle, a target lift arm height, and a target vehicle speed on the traveling path based on the traveling path, calculates a position of the center of gravity of the wheel loader based on the target bent angle and the target lift arm height, determines the travel stability of the vehicle body based on the target bent angle, the target vehicle speed, and the position of the center of gravity, and controls the traveling device and the steering device.SELECTED DRAWING: Figure 10

Description

Technical Field

[0001] The present invention relates to a wheel loader capable of generating a travel route and automatically traveling along the travel route.

Background Art

[0002] When performing excavation work and loading work with a wheel loader, the excavation position and the loading position change as the work progresses. Therefore, when performing excavation work and loading work by automatic driving of the wheel loader, the wheel loader needs to automatically generate a travel route according to changes in the excavation position and the loading position.

[0003] Patent Document 1 discloses a method for automatically generating a travel route of an unmanned vehicle such as a dump truck. As a method for generating an optimal travel route that satisfies the lowest constraint conditions under which the vehicle can travel, further reduces the load on the tires and the vehicle body, shortens the required time for travel, and enables travel with low fuel consumption, thereby minimizing the cost associated with travel.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In a wheel loader, when loading an excavation target onto a transport vehicle such as a dump truck after excavation work, an operation (rise run) of traveling while raising the lift arm is performed. When such an operation is performed, the wheel loader has a higher center of gravity due to the upward movement of the lift arm, and furthermore, since it decelerates in front of the transport vehicle, the vehicle body becomes unstable. In Patent Document 1, the stability during the travel of the unmanned vehicle is not considered, and if an attempt is made to run the wheel loader along the generated travel route, there is a risk that stable autonomous driving cannot be achieved.

[0006] An object of the present invention is to provide a wheel loader capable of stable autonomous driving along a generated travel route.

Means for Solving the Problems

[0007] A wheel loader according to an aspect of the present invention includes a vehicle body in which a front body having front wheels and a rear body having rear wheels are connected so as to be bendable, a lift arm rotatably provided on the front body, a bucket rotatably provided on the lift arm, a traveling device for traveling the vehicle body, a steering device for changing the bending angle and steering by bending the vehicle body, generating a travel route based on an excavation position and a loading position at a work site, While raising the lift arm from a predetermined travel start position on the travel route toward the loading position so that the height of the lift arm at the loading position becomes the loading height and a control device for controlling the traveling device 、the lift arm and the steering device so that the vehicle body travels along the travel route. The control device calculates the center of gravity position of the wheel loader based on the generated travel route, the target bending angle at a plurality of positions on the travel route is calculated, the target vehicle speed at a plurality of positions on the travel route is set to a predetermined initial vehicle speed value, the target lift arm height at a plurality of positions on the travel route is set to a predetermined initial height value, and the target bending angle and and the target lift arm height, and determines the traveling stability of the vehicle body based on the target bending angle while the target bending angle while the target vehicle speed while and the center of gravity position. at each of the plurality of positions on the travel route 、when it is determined that the state of the vehicle body is unstable, until it is determined that the state of the vehicle body is stable, the target vehicle speed and the target lift arm height are repeatedly corrected to be lowered, and travel plan information associating the plurality of positions on the travel route with the target bending angle, the target lift arm height, and the target vehicle speed at the plurality of positions is stored in a storage device. Based on the travel plan information stored in the storage device, the steering device, the lift arm, and the travel device are controlled.

Effects of the Invention

[0008] According to the present invention, a wheel loader can be stably automatically driven along a generated travel route.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

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

[0011] FIG. 1 is a side view of a wheel loader 1 capable of autonomous driving according to an embodiment of the present invention. The wheel loader 1 includes an articulated vehicle body 16 and an articulated working device 17 attached in front of the vehicle body 16. The vehicle body 16 includes a front body 11 equipped with front wheels 4a (wheels 4) on the left and right, and a rear body 12 equipped with rear wheels 4b (wheels 4) on the left and right. The front body 11 and the rear body 12 are connected by a center pin 13 so as to be bendable in the left-right direction.

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

[0013] The working device 17 is attached to the front body 11. The working device 17 includes a lift arm 2 rotatably attached to the front body 11 in the vertical direction, a bucket 3 rotatably attached to the tip of the lift arm 2 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. Note that one lift arm 2 and one arm cylinder 7 are provided on each of the left and right sides of the front body 11. The bucket 3 rotates by the expansion and contraction of the bucket cylinder 8 via a bell crank 9 and a bucket link 10, whereby the orientation of the bucket 3 is raised and lowered.

[0014] When pressure oil is supplied to the bottom chamber, the arm cylinder 7 extends and rotates the lift arm 2 upward (lifting up), and when pressure oil is supplied to the rod chamber, the arm cylinder 7 retracts and rotates the lift arm 2 downward (lifting down). When pressure oil is supplied to the bottom chamber, the bucket cylinder 8 extends and rotates the bucket 3 upward (tilting), and when pressure oil is supplied to the rod chamber, the bucket cylinder 8 retracts and rotates the bucket 3 downward (dumping).

[0015] The wheel loader 1 is steered by the relative rotation of the front body 11 and the rear body 12 due to the extension and contraction of a pair of left and right steering cylinders 14. When the right steering cylinder 14 contracts and the left steering cylinder 14 extends, the vehicle body 16 bends to the right. When the left steering cylinder 14 contracts and the right steering cylinder 14 extends, the vehicle body 16 bends to the left. In this specification, the bending angle corresponds to the rotation angle around the center pin 13. The bending angle is 0 (zero) ° when in a non-bent state, that is, when the wheel loader 1 is in a straight-ahead posture. The bending angle shall take a positive value when the vehicle body 16 is in a posture bent to the right and a negative value when the vehicle body 16 is in a posture bent to the left.

[0016] <System Configuration> FIG. 2 is a system configuration diagram of the wheel loader 1. As shown in FIG. 2, the wheel loader 1 includes a traveling device 28 for traveling the vehicle body 16, a working device 17 for performing excavation work, a steering device 19 for steering the vehicle body 16, a braking device 18 for braking the vehicle body 16 or suppressing the operation of the stopped vehicle body 16, an engine 40 serving as a drive source for these devices, a control device 100 for controlling each part of the wheel loader (hereinafter also referred to as a vehicle) 1, and hydraulic pumps 60A, 60B, 60C mechanically connected to the engine 40.

[0017] The working device 17 is driven by the hydraulic oil discharged from the hydraulic pump 60A, the braking device 18 is driven by the hydraulic oil discharged from the hydraulic pump 60B, and the steering device 19 is driven by the hydraulic oil discharged from the hydraulic pump 60C.

[0018] The wheel loader 1 includes a front control unit 61 for controlling the operation of the working device 17, a brake control unit 62 for controlling the operation of the braking device 18, and a steering control unit 63 for controlling the operation of the steering device 19.

[0019] The working device 17 and the traveling device 28 are driven independently of each other by the power of the engine 40. The engine 40 is constituted by, for example, an internal combustion engine such as a diesel engine. The wheel loader 1 includes an engine control unit 65 that controls the operation of the engine 40. The engine control unit 65 controls the fuel injection amount so that the actual rotational speed detected by the engine rotational speed sensor approaches the target rotational speed calculated by the control device 100.

[0020] The arm cylinder 7 and the bucket cylinder 8 are expanded and contracted by the hydraulic oil (pressure oil) discharged from the hydraulic pump 60A that rotates by the torque output from the engine 40.

[0021] The traveling device 28 has wheels 4 and a power transmission device that transmits the power from the engine 40 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, and the like.

[0022] The input shaft of the torque converter 51 is connected to the output shaft of the engine 40, and the output shaft of the torque converter 51 is connected to the transmission 52. The torque converter 51 is a fluid clutch composed of a well-known impeller, turbine, and stator, and the rotation of the engine 40 is transmitted to the transmission 52 via the torque converter 51. The transmission 52 has a clutch for switching its speed range from the first speed to the fifth speed, and the rotation of the output shaft of the torque converter 51 is shifted by the transmission 52. The rotated speed after shifting is transmitted to the wheels 4 via the propeller shaft 53, the differential device 54, and the axle 55, and the wheel loader 1 travels.

[0023] The wheel loader 1 is provided with a transmission control unit 64 that controls the operation of the transmission 52. The transmission control unit 64 has solenoid valves corresponding to the first to fifth speed ranges of the transmission 52. The transmission control unit 64 controls the transmission 52 by operating the solenoid valves according to a control signal from the control device 100.

[0024] The hydraulic pumps 60A, 60B, and 60C are mechanically connected to the engine 40. The hydraulic pumps 60A, 60B, and 60C are driven by the torque output from the engine 40 to discharge hydraulic oil.

[0025] The hydraulic oil supplied from the hydraulic pump 60A to the arm cylinder 7 and the bucket cylinder 8 is controlled in terms of its pressure, flow rate, and flow direction by the front control unit 61. Thereby, excavation operations and loading operations by the work device 17 are performed. The hydraulic oil supplied from the hydraulic pump 60B to the brake cylinder 18a and the parking brake cylinder 18b is controlled in terms of its pressure, flow rate, and flow direction by the brake control unit 62. Thereby, braking operations and stop holding operations of the vehicle body 16 by the brake device 18 are performed. The hydraulic oil supplied from the hydraulic pump 60C to the pair of left and right steering cylinders 14 is controlled in terms of its pressure, flow rate, and flow direction by the steering control unit 63. Thereby, steering of the vehicle body 16 by the steering device 19 is performed.

[0026] As shown in FIG. 1, a plurality of imaging devices 15 for photographing the periphery of the vehicle body 16 are installed above the driver's cab 5. The imaging device 15 is, for example, a wide-angle video camera equipped with an imaging element such as a CCD or CMOS with excellent durability and weather resistance and a wide-angle lens. The data of the video photographed by the imaging device 15 is output to the control device 100.

[0027] As shown in FIG. 2, the wheel loader 1 includes an arm angle sensor 41 provided on a connecting shaft that connects the vehicle body 16 and the lift arm 2, and a bucket angle sensor 42 provided on a connecting shaft that connects the lift arm 2 and the bucket 3. The arm angle sensor 41 detects the rotation angle (arm angle) of the lift arm 2 with respect to the front body 11, and outputs a signal representing the detection result to the control device 100. The bucket angle sensor 42 detects the rotation angle (bucket angle) of the bucket 3 with respect to the lift arm 2, and outputs a signal representing the detection result to the control device 100. The arm angle and the bucket angle are physical quantities representing the posture of the working device 17. Therefore, the arm angle sensor 41 and the bucket angle sensor 42 function as posture sensors that detect the posture of the working device 17. Note that, as the posture sensor, instead of the arm angle sensor 41, a stroke sensor that detects the stroke amount of the arm cylinder 7 may be provided. Similarly, as the posture sensor, instead of the bucket angle sensor 42, a stroke sensor that detects the stroke amount of the bucket cylinder 8 may be provided.

[0028] The wheel loader 1 is provided with a plurality of pressure sensors. Among the plurality of pressure sensors, the pressure sensor 43 that detects the pressure in the bottom chamber, which is the oil chamber on the side that supports the load, in the arm cylinder 7 and outputs a signal representing the detection result to the control device 100 is included.

[0029] The wheel loader 1 is provided with a bending angle sensor 44 that detects the bending angle. The bending angle sensor 44 is provided on the center pin 13, detects the bending angle, and outputs a signal representing the detection result to the control device 100. The bending angle is a physical quantity representing the posture of the vehicle body 16. That is, the bending angle sensor 44 functions as a posture sensor that detects the posture of the vehicle body 16. Note that, as the posture sensor that detects the posture of the vehicle body 16, instead of the bending angle sensor 44, a stroke sensor that detects the stroke amount of the steering cylinder 14 may be provided.

[0030] The wheel loader 1 is equipped with a vehicle speed sensor 45 that detects the traveling speed of the own vehicle (hereinafter also referred to as the vehicle speed). The vehicle speed sensor 45 is connected to the control device 100. The vehicle speed sensor 45 detects the vehicle speed and outputs a signal representing the detection result to the control device 100.

[0031] The control device 100 generates a traveling route based on the excavation position and the loading position at the work site, and controls the traveling device 28 and the steering device 19 so that the vehicle body 16 travels along the generated traveling route. Thereby, the wheel loader 1 automatically travels to the excavation position and the loading position, and performs excavation work and loading work.

[0032] With reference to FIG. 3, an example of the work performed by the wheel loader 1 will be described. As shown in FIG. 3, the wheel loader 1 (first operation) advances toward the natural ground 91 that is the excavation target, (second operation) inserts the bucket 3 into the natural ground 91, and operates the bucket 3 and the lift arm 2 to perform an excavation operation of excavating the natural ground 91. After the completion of the excavation work, the wheel loader 1 (third operation) reverses to a predetermined position and stops. Thereafter, the wheel loader 1 (fourth operation) advances toward the dump truck 92 while raising the lift arm 2 (rise and run), and stops at the loading position in front of the dump truck 92. Then, (fifth operation) a loading operation of discharging the load (excavated material) in the bucket 3 onto the loading platform of the dump truck 92 is performed. After the completion of the loading work, the wheel loader 1 (sixth operation) reverses to a predetermined position. The wheel loader 1 repeatedly performs a series of operations from (first operation) to (sixth operation) while drawing a V-shaped locus as described above. In this specification, a series of operations from (first operation) to (sixth operation) is also referred to as loader work.

[0033] In the fourth operation (rise and run), the center of gravity position of the wheel loader 1 is raised by the upward movement of the lift arm 2. Further, the wheel loader 1 will decelerate in the deceleration area DA in front of the dump truck 92. For this reason, in the deceleration area DA, the state of the wheel loader 1 is particularly likely to become unstable. In the present embodiment, before the automatic driving is performed, it is determined whether the wheel loader 1 can travel stably along the travel route. Details of the generation process of the travel route used during the automatic driving of the wheel loader 1, the determination process of the travel stability on the travel route performed before the start of the automatic driving, and the control of the automatic driving will be described later.

[0034] As shown in FIG. 2, the wheel loader 1 includes an input device 38, a display device 39, and a communication device 46 provided in the cab 5. The communication device 46 is a wireless communication device capable of wireless communication with a wireless base station constituting a part of the communication line 90, and has a communication interface including a communication antenna having a band such as the 2.1 GHz band as a sensing band. The communication device 46 exchanges information with the remote control device 70 via the communication line 90. The communication line 90 is a mobile communication network (mobile communication network) deployed by a mobile phone carrier or the like, a wide area network such as the Internet.

[0035] The display device 39 is, for example, a liquid crystal display device or an organic EL display device. The display device 39 is an output device that outputs information as an image. The input device 38 is, for example, a switch device having a plurality of switches or a touch sensor device provided on top of the display screen of the display device 39. The input device 38 is operated by an operator and inputs an instruction according to the operation to the control device 100. When an instruction to start automatic driving is input to the control device 100 from the input device 38, the control device 100 executes control to start the automatic driving of the wheel loader 1. Note that the control device 100 similarly executes control to start the automatic driving of the wheel loader 1 when it acquires an automatic driving start command transmitted from the remote control device 70 described later.

[0036] The control device 100 according to this embodiment has a plurality of controllers C1, C2, C3, and C4. Note that since the plurality of controllers C1, C2, C3, and C4 that make up the control device 100 and the controller C5 of the remote operation device 70 described later have the same configuration, they may be collectively referred to as the controller C below.

[0037] The remote operation device 70 exchanges information with the control device 100 of the wheel loader 1 via the communication line 90. The remote operation device 70 includes a remote operation controller C5, a communication device 71 for communicating with the wheel loader 1, an input device 72 for inputting an operator's instruction to the remote operation controller C5, and a display device 73 for displaying a display image on the display screen based on a control signal from the remote operation controller C5.

[0038] The display device 73 is, for example, a liquid crystal display device or an organic EL display device. The display device 73 is an output device that outputs information as an image. The input device 72 is, for example, a keyboard, a mouse, or a touch sensor device provided over the display screen of the display device 73.

[0039] The remote operation controller C5 causes the vehicle body data (including image data) transmitted from the wheel loader 1 to be displayed on the display screen. The input device 72 is operated by the operator and inputs an instruction corresponding to the operation to the remote operation controller C5. When an instruction to start automatic driving is input to the remote operation controller C5 from the input device 72, the remote operation controller C5 transmits an automatic driving start command to the wheel loader 1 via the communication device 71.

[0040] FIG. 4 is a diagram showing the hardware configuration of the controller C. As shown in FIG. 4, the controller C is composed of a computer including a processing device 101 such as a CPU (Central Processing Unit), an MPU (Micro Processing Unit), and a DSP (Digital Signal Processor), a non-volatile memory 102 such as a ROM (Read Only Memory), a flash memory, and a hard disk drive, a volatile memory 103 called a so-called RAM (Random Access Memory), an input interface 104, an output interface 105, and other peripheral circuits. Note that the controller C may be composed of one computer or a plurality of computers. Further, as the processing device 101, an ASIC (application specific integrated circuit), an FPGA (Field Programmable Gate Array), or the like may be adopted.

[0041] A program capable of executing various operations is stored in the non-volatile memory 102. That is, the non-volatile memory 102 is a storage device (storage medium) capable of reading a program for realizing the functions of the present embodiment. The processing device 101 is an arithmetic processing device that expands the program 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 the signals taken in from the input interface 104, the non-volatile memory 102, and the volatile memory 103 according to the program.

[0042] The input interface 104 converts the signals input from various devices such as a photographing device, a sensor, and other controllers so that they can be arithmetically processed by the processing device 101. Further, the output interface 105 generates an output signal corresponding to the arithmetic result in the processing device 101 and outputs the signal to various devices such as a solenoid valve that controls hydraulic equipment.

[0043] The plurality of imaging devices 15 are connected to the position setting controller C2, and the arm angle sensor 41, bucket angle sensor 42, pressure sensor 43, bending angle sensor 44, and vehicle speed sensor 45 are connected to the vehicle control controller C4. The plurality of controllers C are communicably connected to each other via an in-vehicle network 106 called a Controller Area Network (CAN). Note that the in-vehicle network 106 may use a communication standard other than CAN, for example, Ethernet (registered trademark). As a result, information (data) such as the detection results of the sensors and the calculation results of the controller C is exchanged between the plurality of controllers C.

[0044] Among the plurality of controllers C, there are a position setting controller C2 that sets the target position of the movement of the wheel loader 1 based on the data of the video captured by the imaging device 15, and a load calculation controller C3 that calculates the load of the load (excavated material) loaded in the bucket 3 based on the detection results of the angle sensors 41 and 42 and the pressure sensor 43 (hereinafter also referred to as the in-bucket load), and a travel plan controller C1 that generates the travel plan information of the wheel loader 1 based on the target position set by the position setting controller C2 and the in-bucket load calculated by the load calculation controller C3, and a vehicle control controller C4 that controls the travel device 28, the steering device 19, and the work device 17 based on the travel plan information generated by the travel plan controller C1.

[0045] The position setting controller C2 detects the ground 91 and the dump truck 92 shown in FIG. 3 based on the data of the video captured by the imaging device 15. That is, the imaging device 15 and the position setting controller C2 constitute an object detection device 56 that detects objects around the vehicle body 16. Note that, for example, a well-known object detection method using a neural network can be adopted as the detection method of the ground 91 and the dump truck 92.

[0046] Based on the detected boundary line B1 between the natural ground 91 and the ground, the position setting controller C2 sets the target position (hereinafter also referred to as the target excavation position) P1 of the vehicle body 16 when performing excavation work at the work site. At the target excavation position P1, the position setting controller C2 sets the target azimuth angle A1 representing the target azimuth, with the direction orthogonal to the boundary line B1 between the natural ground 91 and the ground as the target azimuth of the vehicle body 16.

[0047] Based on the detected boundary line B2 between the dump truck 92 and the ground, the position setting controller C2 sets the target position (hereinafter also referred to as the target loading position) P2 of the vehicle body 16 when performing loading work at the work site. At the target loading position P2, the position setting controller C2 sets the target azimuth angle A2 representing the target azimuth, with the direction orthogonal to the boundary line B2 between the dump truck 92 and the ground as the target azimuth of the vehicle body 16.

[0048] The target azimuth angles A1 and A2 are represented by the angles formed between the reference azimuth and the traveling direction of the vehicle body 16. The target azimuth angles A1 and A2 are set with the reference azimuth as 0°, taking positive values in the clockwise direction in the figure with respect to the reference azimuth, and negative values in the counterclockwise direction in the figure with respect to the reference azimuth. That is, the target azimuth angles A1 and A2 are set in the range from -180° to +180°. Note that the target azimuth angles A1 and A2 may be set in the range from 0° to 360° in the clockwise direction in the figure with the reference azimuth as 0°.

[0049] The target position is represented by coordinates in, for example, a global coordinate system. Note that the target position may be represented by coordinates in a site coordinate system with a predetermined position at the work site as the origin. The reference azimuth is set to, for example, true north. The global coordinate system and the site coordinate system are capable of coordinate transformation. Note that the position setting controller C2 may also identify the target position using a vehicle reference coordinate system with the current position of the host vehicle as the origin and the forward direction of the host vehicle as the reference azimuth when shooting the surroundings of the vehicle body 16 by the imaging device 15 and generating the travel routes R1 to R4.

[0050] The wheel loader 1 is equipped with a position detection device 47 that detects the position of the own vehicle and outputs a signal representing the detection result to the position setting controller C2. The position detection device 47 includes, for example, a plurality of antennas for GNSS (Global Navigation Satellite System), and a positioning calculation device that calculates the position and orientation of the wheel loader 1 in the global coordinate system based on satellite signals (GNSS radio waves) from a plurality of positioning satellites received by the GNSS antennas.

[0051] Note that the position detection device 47 is not limited to this, and may be provided with a wheel speed sensor that detects the rotational speed of the wheel 4 and a gyro sensor. The positioning calculation device calculates the moving distance of the wheel loader 1 based on the detection result of the wheel speed sensor, and calculates the moving direction of the wheel loader 1 based on the detection result of the gyro sensor.

[0052] In the non-volatile memory 102 of the load calculation controller C3 shown in FIG. 4, a mathematical formula or a data table used to calculate the load in the bucket from the arm angle, the bucket angle, and the pressure in the bottom chamber of the arm cylinder 7 is stored. The load calculation controller C3 calculates the load in the bucket based on the mathematical formula or data table stored in the non-volatile memory 102 and the detection results of the arm angle sensor 41, the bucket angle sensor 42, and the pressure sensor 43. In this way, the load calculation controller C3, the arm angle sensor 41, the bucket angle sensor 42, and the pressure sensor 43 constitute a load detection device 50 that detects the load of the load loaded in the bucket 3 (load in the bucket). Note that the method for detecting the load in the bucket is not limited to this. The load detection device 50 may be constituted by a load sensor provided in the bucket 3 and a controller that calculates the load in the bucket based on the detection result of the load sensor.

[0053] The travel plan controller C1 calculates target values for the travel route R, the bending angle on the travel route R, the vehicle speed, and the height of the lift arm 2 based on the target excavation position P1, the target azimuth angle A1 at the target excavation position P1, the target loading position P2, and the target azimuth angle A2 at the target loading position P2, and generates operation commands such as acceleration, deceleration, steering, and lift of the vehicle based on the calculation results. Details of the functions of the travel plan controller C1 will be described later.

[0054] The vehicle control controller C4 controls each part of the wheel loader 1 based on the operation commands generated by the travel plan controller C1.

[0055] For example, as shown in FIG. 2, the vehicle control controller C4 controls the operation of the working device 17 as follows by controlling the front control unit 61 based on the operation command. The front control unit 61 includes an arm flow control valve that controls the flow rate and direction of the hydraulic oil from the hydraulic pump 60A to the arm cylinder 7, an arm control solenoid valve that outputs a command pressure to the arm flow control valve, a bucket flow control valve that controls the flow rate and direction of the hydraulic oil from the hydraulic pump 60A to the bucket cylinder 8, and a bucket control solenoid valve that outputs a command pressure to the bucket flow control valve.

[0056] The vehicle control controller C4 outputs a control signal to the arm control solenoid valve based on the operation command generated by the travel plan controller C1, and generates a command pressure by the arm control solenoid valve. The command pressure generated by the arm control solenoid valve is led to the pressure receiving chamber of the arm flow control valve. The arm flow control valve operates according to the command pressure acting on the pressure receiving chamber. The arm flow control valve controls the flow rate and the direction of the hydraulic oil supplied from the hydraulic pump 60A to the arm cylinder 7 according to the command pressure acting on the pressure receiving chamber. Similarly, the vehicle control controller C4 outputs a control signal to the bucket control solenoid valve for controlling the bucket flow control valve based on the operation command generated by the travel plan controller C1. When the working device 17 operates, the arm angle and the bucket angle change. Note that when the arm angle changes, the height from the traveling surface to the center position of the bucket pin provided at the tip of the lift arm 2 (hereinafter also referred to as the lift arm height) changes.

[0057] The operation command includes a steering control command calculated based on the target bending angle which is the target value of the bending angle, a travel control command (an accelerator command and a brake command) calculated based on the target vehicle speed which is the target value of the vehicle speed, and an arm control command calculated based on the target lift arm height which is the target value of the lift arm height.

[0058] The vehicle control controller C4 controls the front control unit 61 based on the arm control command included in the operation command from the travel plan controller C1. Thereby, the operation of the lift arm 2 is controlled so that the height of the actual lift arm 2 becomes the target lift arm height. That is, the travel plan controller C1 and the vehicle control controller C4 operate the lift arm 2 so that the actual arm angle detected by the arm angle sensor 41 becomes the target arm angle corresponding to the target lift arm height.

[0059] In addition, the vehicle control controller C4 controls the steering control unit 63 based on the steering control command included in the operation command from the travel plan controller C1. Thereby, the operation of the steering device 19 is controlled so that the actual bending angle becomes the target bending angle. That is, the travel plan controller C1 and the vehicle control controller C4 operate the steering device 19 so that the actual bending angle detected by the bending angle sensor 44 becomes the target bending angle.

[0060] Furthermore, the vehicle control controller C4 controls the engine control unit 65, the transmission control unit 64, and the brake control unit 62 based on the travel control command included in the operation command from the travel plan controller C1. Thereby, the operation of the travel device 28 is controlled so that the actual vehicle speed becomes the target vehicle speed. That is, the travel plan controller C1 and the vehicle control controller C4 operate the travel device 28 so that the actual vehicle speed detected by the vehicle speed sensor 45 becomes the target vehicle speed.

[0061] In the present embodiment, an example in which the travel plan controller C1, the position setting controller C2, the load calculation controller C3, and the vehicle control controller C4 are provided separately will be described. However, the present invention is not limited to this. Some or all of the functions of the controller C may be provided by other controllers C. Further, one controller C may have all of the functions of the above-described controllers C1 to C4.

[0062] FIG. 5 is a functional block diagram of the travel plan controller C1. The travel plan controller C1 functions as a switching position setting unit 21, a route generation unit 22, a stable travel plan unit 23, an operation command unit 24, and a feedback unit 25 by executing a program stored in the nonvolatile memory 102.

[0063] Incidentally, as described above, when the wheel loader 1 repeatedly travels back and forth between the excavation position and the loading position, after the excavation work or the loading work, it first reverses and then stops, switches to forward movement, and heads towards the target position. Hereinafter, in the loader operation, the position where the switch is made from reverse to forward is referred to as the turning-back position P0 (see FIG. 3). In this embodiment, a case where the turning-back position when moving towards the loading position after the excavation work and the turning-back position when moving towards the excavation position after the loading work are the same will be described, but the two may be set at different positions.

[0064] As shown in FIG. 3, based on the target excavation position P1 set by the position setting controller C2 and the target azimuth angle A1 at that position, and the target loading position P2 set by the position setting controller C2 and the target azimuth angle A2 at that position, the turning-back position setting unit 21 sets the target turning-back position P0 and the target azimuth angle A0 at that position. The target turning-back position P0 is the target position at which the traveling direction of the vehicle is switched from the reverse direction to the forward direction and the forward travel is started. An example of the method for setting the target turning-back position P0 and the target azimuth angle A0 is as follows.

[0065] In the non-volatile memory 102 of the travel plan controller C1, a data table (hereinafter also referred to as a position table) representing the turning-back positions corresponding to the excavation position and the loading position is stored. The position table is determined based on actual machine tests and the like performed by the wheel loader 1 operated by the operator. The turning-back position setting unit 21 refers to the position table and sets the target turning-back position P0 based on the target positions P1 and P2.

[0066] The turning-back position setting unit 21 determines the azimuth intermediate between the azimuth from the target turning-back position P0 to the target excavation position P1 and the azimuth from the target turning-back position P0 to the target loading position P2 as the target azimuth of the target turning-back position P0. The turning-back position setting unit 21 determines the angle formed by the determined target azimuth and the reference azimuth as the target azimuth angle A0.

[0067] The path generation unit 22 (see FIG. 5) generates a travel path R1 for excavation work from the target turning position P0 to the target excavation position P1, a first return travel path R2 from the target excavation position P1 to the target turning position P0, a travel path R3 for loading work from the target turning position P0 to the target loading position P2, and a second return travel path R4 from the target loading position P2 to the target turning position P0.

[0068] In the travel path R1, the target turning position P0 is the travel start position, and the target excavation position P1 is the travel end position. In the travel path R2, the target excavation position P1 is the travel start position, and the target turning position P0 is the travel end position. In the travel path R3, the target turning position P0 is the travel start position, and the target loading position P2 is the travel end position. In the travel path R4, the target loading position P2 is the travel start position, and the target turning position P0 is the travel end position. For the sake of convenience in explanation, hereinafter, the travel paths R1 to R4 are collectively referred to as the travel path R.

[0069] The path generation unit 22 generates a travel path R such that no forced steering occurs by connecting the coordinates of the travel start position and the coordinates of the travel end position with a gentle curve in consideration of the target azimuth angle at the travel start position and the target azimuth angle at the travel end position.

[0070] The running stability of the vehicle increases as the curvature of the travel path R decreases. The shorter the path length of the travel path R, the more energy consumption can be suppressed. However, the shorter the path length of the travel path R, the more likely the curvature is to increase. Therefore, the turning position setting unit 21 and the path generation unit 22 preferably set an evaluation function using the total length of the calculated travel path R, the change amount of the curvature of the travel path R, etc., and determine the turning position P0 and the travel path R such that the evaluation function is minimized by machine learning. Thereby, a travel path R that is easy to ensure running stability and suppresses energy consumption is generated.

[0071] The stable travel planning unit 23 shown in Fig. 5 is a processing unit that plans the stable travel of the wheel loader 1 on the generated travel route R. Based on the generated travel route R, the stable travel planning unit 23 calculates the target bending angle, the target lift arm height, and the target vehicle speed on the travel route R. The stable travel planning unit 23 calculates the center of gravity position of the wheel loader 1 based on the calculated target bending angle and the calculated target lift arm height. The stable travel planning unit 23 determines the travel stability of the vehicle body 16 based on the calculated target bending angle, the calculated target vehicle speed, and the calculated center of gravity position.

[0072] Hereinafter, with reference to Figs. 6 to 10, the details of the functions of the stable travel planning unit 23 will be described. Fig. 6 is a diagram for explaining the details of the functions of the stable travel planning unit 23. As shown in Fig. 6, the stable travel planning unit 23 functions as a bending angle calculation unit 30, a support polygon calculation unit 33, a stable region setting unit 34, a height calculation unit 35, a vehicle speed calculation unit 37, a center of gravity calculation unit 31, a ZMP calculation unit 32, and a travel stability determination unit 36.

[0073] The bending angle calculation unit 30 calculates the target bending angle of the vehicle body 16 at each position on the travel route R in order to make the wheel loader 1 travel along the travel route R generated by the route generation unit 22. A plurality of nodes representing positions on the travel route R are set on the travel route R. The plurality of nodes are set by the route generation unit 22. The bending angle calculation unit 30 calculates the target bending angle of the vehicle body 16 when the wheel loader 1 is located at each node. The bending angle calculation unit 30 stores the travel plan information associating the plurality of nodes on the travel route R with the target bending angles at the plurality of nodes in the non-volatile memory 102.

[0074] The support polygon calculation unit 33 calculates the support polygon SP of the vehicle based on the target bending angle calculated by the bending angle calculation unit 30. Fig. 7 is a schematic diagram of the wheel loader 1 viewed from above, showing the support polygon SP. As shown in Fig. 7, the support polygon SP is a convex polygon region formed by the sides connecting the ground contact points Pt1 to Pt4 of the wheels 4 of the wheel loader 1.

[0075] Specifically, the support polygon calculation unit 33 calculates the position coordinates of the contact points Pt1 and Pt2 of the pair of left and right front wheels 4a and the contact points Pt3 and Pt4 of the pair of left and right rear wheels 4b at each node based on the relative position data representing the relative positions of the respective wheels 4 with respect to the center pin 13 and the target bending angles at the respective nodes of the travel route R. The relative position data is stored in the non-volatile memory 102 of the travel plan controller C1. The support polygon calculation unit 33 calculates a rectangular support polygon SP formed by a line segment connecting the contact point Pt1 and the contact point Pt2 of the vehicle body 16, a line segment connecting the contact point Pt2 and the contact point Pt4, a line segment connecting the contact point Pt4 and the contact point Pt3, and a line segment connecting the contact point Pt3 and the contact point Pt1. The support polygon SP is rectangular when the vehicle body 16 is not bent, but trapezoidal when the vehicle body 16 is bent, and its shape changes depending on the target bending angle.

[0076] The stable region setting unit 34 sets a stable region SA smaller than the support polygon SP inside the support polygon SP calculated by the support polygon calculation unit 33. The stable region setting unit 34 sets, for example, a region surrounded by a plurality of lines obtained by offsetting each side constituting the support polygon SP by a predetermined distance inside the support polygon SP as the stable region SA.

[0077] The stable region SA is set in consideration of the fact that the running stability decreases due to unevenness of the ground or the like. Therefore, it is preferable to set the stable region SA small at a work site with large ground unevenness and to set the stable region SA large at a work site with small ground unevenness.

[0078] The center of gravity calculation unit 31 shown in FIG. 6 calculates the center of gravity position G of the entire wheel loader (vehicle) at each node based on the load in the bucket detected by the load detection device 50, the target bending angles at the respective nodes calculated by the bending angle calculation unit 30, the target lift arm height at the respective nodes calculated by a height calculation unit 35 described later, and the weight data of the wheel loader 1.

[0079] The weight data of the wheel loader 1 is stored in the non-volatile memory 102 of the travel plan controller C1. The weight data of the wheel loader 1 includes the weight and the center of gravity position of the front body 11, the weight and the center of gravity position of the rear body 12, the weight and the center of gravity position of the bucket 3 in the unloaded state, and the weight and the center of gravity position of the lift arm 2. The center of gravity position of each part is specified by the coordinate position in the vehicle body reference coordinate system with a predetermined position of the wheel loader 1 as the origin.

[0080] The ZMP calculation unit 32 calculates the vector of the force acting on the center of gravity position G based on the center of gravity position G calculated by the center of gravity calculation unit 31, the travel route R generated by the route generation unit 22, and the target vehicle speed calculated by the vehicle speed calculation unit 37 described later at each node of the travel route R. Further, the ZMP calculation unit 32 calculates the ZMP (Zero Moment Point), which is the point where the calculated force vector and the travel surface intersect, at each node of the travel route R.

[0081] With reference to FIGS. 7 and 8, a specific calculation method of the ZMP at a predetermined node will be described. FIG. 7 is a schematic view of the wheel loader 1 viewed from above, showing the support polygon SP and the ZMP. FIG. 8 is a schematic view of the wheel loader 1 viewed from the side, showing the support polygon SP and the ZMP.

[0082] As shown in FIGS. 7 and 8, the ZMP calculation unit 32 calculates the vector of the vertically downward gravity F1 acting on the center of gravity position G based on the total weight of the wheel loader 1 including the weight in the bucket and the gravitational acceleration. The ZMP calculation unit 32 calculates the vector of the centrifugal force F2 acting on the center of gravity position G based on the curvature of the travel route R, the target vehicle speed, and the total weight of the wheel loader 1.

[0083] The ZMP calculation unit 32 calculates the time change rate of the target vehicle speed at each node based on the target vehicle speed at each node. The time change rate of the target vehicle speed at a predetermined node can be calculated based on, for example, the target vehicle speed of the predetermined node, the target vehicle speed of the node adjacent to the predetermined node, and the distance between the predetermined node and the adjacent node. The ZMP calculation unit 32 calculates the vector of the inertial force F3 acting on the center of gravity position G based on the total weight of the wheel loader 1 and the time change rate of the target vehicle speed.

[0084] The ZMP calculation unit 32 calculates the vector of the resultant force F0 of the gravitational force F1, the centrifugal force F2, and the inertial force F3 acting on the center of gravity position G. The ZMP calculation unit 32 calculates the point where the extension line L0 of the vector of the resultant force F0 intersects the ground (the traveling surface of the wheel loader 1) as the ZMP.

[0085] As will be described later, the traveling device 28 of the wheel loader 1 is controlled based on the target vehicle speed set for each node of the traveling route R. However, due to the ground conditions such as the unevenness of the ground at the work site, there may be a difference between the target vehicle speed and the actual vehicle speed. For this reason, the ZMP calculation unit 32 according to the present embodiment performs feedback based on the difference between the actual vehicle speed and the target vehicle speed detected in the past.

[0086] The feedback unit 25 shown in FIGS. 5 and 6 stores, in association with the node and the position coordinates of the work site, data representing the difference between the actual vehicle speed detected by the vehicle speed sensor 45 and the target vehicle speed calculated by the stable traveling plan unit 23 at each node while the wheel loader 1 is automatically traveling along the traveling route R. The data table in which the data representing the difference between the actual vehicle speed and the target vehicle speed is associated with the position coordinates of the work site is stored in the non-volatile memory 102 of the traveling plan controller C1.

[0087] Data representing the difference between the actual vehicle speed and the target vehicle speed is, for example, the ratio of the actual vehicle speed to the target vehicle speed (hereinafter also referred to as the vehicle speed ratio). The feedback unit 25 obtains the vehicle speed ratio by dividing the actual vehicle speed by the target vehicle speed at each node. The vehicle speed ratio associated with the position coordinates of the work site may be the average value of past data or the most recent data.

[0088] The ZMP calculation unit 32 calculates the ZMP in consideration of the data representing the difference between the actual vehicle speed and the target vehicle speed stored in the non-volatile memory 102 of the travel plan controller C1. Specifically, the ZMP calculation unit 32 multiplies the target vehicle speed by the vehicle speed ratio and then calculates the centrifugal force F2 and the inertial force F3 acting on the center of gravity position G.

[0089] As shown in FIG. 6, the running stability determination unit 36 determines the running stability of the vehicle body 16 based on the positional relationship between the support polygon SP calculated by the support polygon calculation unit 33 and the ZMP calculated by the ZMP calculation unit 32. Specifically, the running stability determination unit 36 determines whether the state of the vehicle body 16 is stable or unstable based on whether the ZMP calculated by the ZMP calculation unit 32 is within the stable region SA set by the stable region setting unit 34. When the ZMP is within the stable region SA, the running stability determination unit 36 determines that the running stability is high, that is, the state of the vehicle body 16 is stable. When there is no ZMP within the stable region SA, the running stability determination unit 36 determines that the running stability is low, that is, the state of the vehicle body 16 is unstable.

[0090] The vehicle speed calculation unit 37 calculates the target vehicle speed based on the determination result of the running stability at each position on the travel route R. The height calculation unit 35 calculates the target lift arm height based on the determination result of the running stability at each position on the travel route R. Hereinafter, the calculation methods of the target vehicle speed and the target lift arm height will be described in detail. The calculated target vehicle speed and target lift arm height may be corrected depending on the determination result of the running stability. That is, the target vehicle speed and the target lift arm height, which are the calculation results before the running stability determination process is performed, can be said to be provisional target values.

[0091] The vehicle speed calculation unit 37 sets the target vehicle speed at each position on the travel route R to a predetermined initial vehicle speed value. The initial vehicle speed value is determined based on, for example, the maximum vehicle speed when a wheel loader operated by an operator travels along the travel route R in loader work. In a wheel loader, when traveling toward the loading position, usually, the speed stage is set to the second speed. The maximum vehicle speed when the speed stage is set to the second speed is about 12 km / h. Therefore, the maximum vehicle speed of 12 km / h is set as the initial vehicle speed value of the target vehicle speed at each node except the final node of the travel route R3. In this embodiment, the target vehicle speed of the final node is set to 0 (zero).

[0092] When the running stability determination unit 36 determines that the state of the vehicle body 16 is stable, the vehicle speed calculation unit 37 determines the temporary target vehicle speed used for the determination as the target vehicle speed for operation commands. When the running stability determination unit 36 determines that the state of the vehicle body 16 is unstable, the vehicle speed calculation unit 37 determines a value obtained by subtracting a predetermined value from the target vehicle speed used for the determination as the new target vehicle speed. Each time the running stability determination unit 36 determines that the state of the vehicle body 16 is unstable, the vehicle speed calculation unit 37 calculates a new target vehicle speed that is lower than the current target vehicle speed by a predetermined value. The vehicle speed calculation unit 37 repeatedly corrects the target vehicle speed to be lower until the state of the vehicle body 16 is determined to be stable. That is, when the running stability is low, the vehicle speed calculation unit 37 corrects the target vehicle speed in the downward direction.

[0093] The vehicle speed calculation unit 37 stores in the non-volatile memory 102 the travel plan information that associates a plurality of nodes on the travel route R with the target vehicle speeds at the plurality of nodes.

[0094] The height calculation unit 35 sets the target lift arm height at each position on the travel route R to a predetermined initial height value. The initial height value is calculated based on, for example, an initial height value table determined by actual machine tests or the like and the travel route R generated by the route generation unit 22.

[0095] The height initial value table is a data table in which each position of the reference travel route is associated with the lift arm height. For example, when the wheel loader 1 heads towards the loading position, an operation (rise run) of raising the lift arm while traveling is performed so that the loading operation can be started immediately after arriving at the loading position. Therefore, the height initial value table used for calculating the lift arm height on the travel route R3 is composed of data in which the lift arm height gradually increases from the travel start position to the travel end position of the reference travel route, and the lift arm height becomes the loading height at the travel end position. As will be described later, when it is determined that the state of the vehicle body 16 is unstable, the target lift arm height is corrected to a low value. For this reason, it is preferable to set the height initial value of the height initial value table to a value larger than the value measured by the actual machine test. Instead of the height initial value table, the initial value of the target lift arm height at each position of the travel route R may be set to the loading height (constant value), but by using the initial value table obtained from the actual machine test, the calculation load can be reduced.

[0096] Similarly, for the height initial values of the target lift arm heights at each position of the other travel routes R1, R2, and R4, they are set based on the corresponding height initial value tables or initial values (constant values). For example, the height initial value of the lift arm height at each position of the travel route R1 for excavation work is set to a height such that the tip of the lift arm 2 is located below the central axis of the wheel 4, as shown in FIG. 1.

[0097] When the route length of the reference travel route of the height initial value table is different from the route length of the travel route R generated by the route generation unit 22, the height initial value of the target lift arm height at each position of the travel route R is set in consideration of the ratio of the route length of the reference travel route to the route length of the travel route R.

[0098] When the running stability determination unit 36 shown in FIG. 6 determines that the state of the vehicle body 16 is stable, the height calculation unit 35 determines the temporary target lift arm height used for the determination as the target lift arm height for operation commands. When the running stability determination unit 36 determines that the state of the vehicle body 16 is unstable, the height calculation unit 35 determines, as the new target lift arm height, a value obtained by subtracting a predetermined value from the target lift arm height used for the determination. Each time the running stability determination unit 36 determines that the state of the vehicle body 16 is unstable, the height calculation unit 35 calculates a new target lift arm height that is lower than the current target lift arm height by a predetermined value. The height calculation unit 35 repeatedly performs the correction of lowering the target lift arm height until the state of the vehicle body 16 is determined to be stable. That is, when the running stability is low, the height calculation unit 35 corrects the target lift arm height in the downward direction.

[0099] The height calculation unit 35 stores in the non-volatile memory 102 travel plan information associating a plurality of nodes on the travel route R with the target lift arm heights at the plurality of nodes.

[0100] When the target vehicle speed and the target lift arm height are updated, the center-of-gravity calculation unit 31 calculates the center-of-gravity position G using the updated target lift arm height. As a result, the center-of-gravity position G is updated. When the center-of-gravity position G is updated, the ZMP calculation unit 32 calculates the ZMP based on the updated center-of-gravity position G and the updated target vehicle speed. As a result, the ZMP is updated. When the ZMP is updated, the running stability determination unit 36 determines the running stability based on the positional relationship between the updated ZMP and the stable region SA.

[0101] As described above, the stable driving plan unit 23 stores, in the non-volatile memory 102, driving plan information associating a plurality of positions on the generated driving route R with the target bending angle, the target lift arm height, and the target vehicle speed at the plurality of positions. The driving plan information is stored in the non-volatile memory 102 as, for example, a data table. When it is determined that the state of the vehicle body 16 is unstable, the stable driving plan unit 23 corrects the target vehicle speed and the target lift arm height used for the determination, re-calculates the center of gravity position G and the ZMP based on the correction result, and performs the determination of driving stability again. When it is determined that the state of the vehicle body 16 is stable, the stable driving plan unit 23 does not correct the target vehicle speed and the target lift arm height used for the determination. As a result, the provisional target vehicle speed and the provisional target lift arm height used for the determination of driving stability are determined as the target vehicle speed and the target lift arm height for operation commands.

[0102] When the number of calculation times m of the target vehicle speed and the target lift arm height at the same node (the same position) reaches the predetermined maximum number of calculation times M, the stable driving plan unit 23 determines that driving stability cannot be maintained on the current driving route and decides to correct the driving route R, and ends various calculations for the currently set driving route. The maximum number of calculation times M is stored in the non-volatile memory 102 of the driving plan controller C1.

[0103] When it is determined by the stable driving plan unit 23 that the driving route R needs to be corrected, the switching position setting unit 21 shown in FIG. 5 sets a position farther from the current switching position P0 than the target excavation position P1 and the target loading position P2 as the new switching position P0. When the new switching position P0 is set by the switching position setting unit 21, the route generation unit 22 generates a new driving route R. When the driving route R is updated, the stable driving plan unit 23 calculates the target bending angle, the target vehicle speed, and the target lift arm height again based on the updated driving route R.

[0104] Based on the travel plan information stored in the non-volatile memory 102, the operation instruction unit 24 calculates a steering control instruction, a travel control instruction (an accelerator instruction and a brake instruction), and an arm control instruction as operation instructions, and outputs the calculation results to the vehicle control controller C4. Based on the steering control instruction, the travel control instruction, and the arm control instruction output from the operation instruction unit 24, the vehicle control controller C4 controls the steering device 19, the travel device 28, and the lift arm 2.

[0105] Here, with reference to FIG. 9, the relationship between the deceleration (vehicle speed reduction rate), the lift arm height, and the bending angle of the vehicle body 16 and the running stability will be described. Note that the bending angle can also be replaced with the curvature of the travel route R. The deceleration (vehicle speed reduction rate) corresponds to the absolute value of the time change rate of the vehicle speed when the time change rate of the vehicle speed is negative. As shown in FIG. 9, when the stable region and the unstable region are distinguished by the deceleration, the lift arm height, and the bending angle, the boundary line between the stable region and the unstable region is represented as shown in the figure. The region to the upper right of the illustrated boundary line is an unstable region with low running stability, and the region to the lower left of the boundary line is a stable region with high running stability. As shown in the figure, for the wheel loader 1, the larger the deceleration, the higher the lift arm height, and the larger the bending angle (the larger the curvature of the travel route R), the larger the unstable region becomes.

[0106] With reference to the flowchart of FIG. 10, an example of the flow of the stable travel plan process executed by the stable travel plan unit 23 according to the embodiment of the present invention will be described. Note that the processes shown in the flowchart of FIG. 10 are executed for each of the travel routes R1 with the switching position P0 as the travel start position and the target excavation position P1 as the travel end position, the travel route R2 with the target excavation position P1 as the travel start position and the switching position P0 as the travel end position, the travel route R3 with the switching position P0 as the travel start position and the target loading position P2 as the travel end position, and the travel route R4 with the target loading position P2 as the travel start position and the switching position P0 as the travel end position.

[0107] The process shown in the flowchart of FIG. 10 starts when the execution condition of the stable driving plan process is satisfied and is repeatedly executed at a predetermined control cycle. The execution condition of the stable driving plan process includes that the automatic driving mode is set by the control device 100. When an automatic driving start command is input to the control device 100 by an operation on the input devices 38 and 72 of the operator, the control device 100 sets the automatic driving mode.

[0108] The execution conditions of the stable driving plan process are set for each of the driving routes R1 to R4. For example, the execution condition of the stable driving plan process for the driving route R3 is satisfied when the automatic driving mode is set and the wheel loader 1 automatically travels along the driving route R2 and the wheel loader 1 reaches the target switching position P0.

[0109] As shown in FIG. 10, in step S1, the stable driving plan unit 23 acquires the driving route R generated by the route generation unit 22 and proceeds to step S2. The number of nodes set in the driving route R is N. In step S2, the centroid calculation unit 31 acquires the load in the bucket calculated by the load calculation controller C3 and proceeds to step S3.

[0110] In step S3, the stable driving plan unit 23 sets the node number n to N + 1. N is the number of nodes as described above. The node number n is a variable representing the number of the node. The node number n of the driving start position is 1, and the node number n of the driving end position is N. When the setting process of the node number n in step S3 is completed, the process proceeds to step S4.

[0111] In step S4, the stable driving plan unit 23 subtracts 1 from the currently set node number n, sets the node number n of the node to be calculated, and proceeds to step S5. In step S5, the stable driving plan unit 23 calculates the target bending angle at the node set as the calculation target in step S4 and proceeds to step S6.

[0112] In step S6, the support polygon calculation unit 33 calculates a support polygon SP based on the target bending angle calculated in step S6. In step S6, the stable region setting unit 34 sets a stable region SA based on the support polygon SP calculated by the support polygon calculation unit 33. When the region calculation process in step S6 ends, the process proceeds to step S7.

[0113] In step S7, the stable travel plan unit 23 determines whether the node number n of the node currently set as the calculation target matches N. In step S7, if it is determined that the node number n of the node currently set as the calculation target matches the number of nodes N, that is, the node to be calculated is the node at the travel end position (the final node), the process proceeds to step S8. In step S7, if it is determined that the node number n of the node currently set as the calculation target does not match the number of nodes N, that is, the node to be calculated is not the node at the travel end position (the final node), the process proceeds to step S9.

[0114] In step S8, the vehicle speed calculation unit 37 sets the target vehicle speed to 0 (zero). Also, in step S8, the height calculation unit 35 sets the target lift arm height to the target height at the predetermined travel end position. When the process in step S8 ends, the process returns to step S4. Here, the target height at the travel end position corresponds to the loading height onto the dump truck 92 when the travel route R3 toward the loading position is the calculation target, and in the case of the other travel routes R1, R2, and R4, it corresponds to the height in the normal travel posture.

[0115] That is, the process in step S8 is a process in which the vehicle body 16 stops at the final node and the lift arm height becomes the target height at the travel end position. For example, when the travel route R3 for transporting the excavated material to the dump truck 92 is the calculation target, the process in step S8 is executed for the purpose of enabling the wheel loader 1 to reach the final node with the lift arm 2 raised to the loading height.

[0116] In step S9, the stable travel planning unit 23 sets the number of calculations m to 0 (zero) and proceeds to step S10. The number of calculations m is a variable representing the number of repetitions of the calculation of the target vehicle speed and the target lift arm height for one node. In step S10, the travel stability determination unit 36 adds 1 to the number of calculations m and proceeds to step S11.

[0117] In step S11, the vehicle speed calculation unit 37 calculates the target vehicle speed, and the height calculation unit 35 calculates the target lift arm height. When the number of calculations m is 1, the vehicle speed calculation unit 37 sets the vehicle speed initial value to the target vehicle speed, and the height calculation unit 35 sets the height initial value to the target lift arm height. When the number of calculations m is not 1, the vehicle speed calculation unit 37 sets a value obtained by subtracting a predetermined value from the current target vehicle speed as the new target vehicle speed, and the height calculation unit 35 sets a value obtained by subtracting a predetermined value from the current target lift arm height as the new target lift arm height. When the process of step S11 is completed, the process proceeds to step S12.

[0118] In step S12, the center of gravity calculation unit 31 calculates the center of gravity position G of the wheel loader (vehicle) 1 based on the load in the bucket acquired in step S2, the target bending angle calculated in step S5, and the lift arm height calculated in step S11, and proceeds to step S13.

[0119] In step S13, the ZMP calculation unit 32 calculates the ZMP based on the target flexion angle calculated in step S5, the target vehicle speed calculated in step S11, the center of gravity position G calculated in step S12, and the vehicle speed ratio stored in the non-volatile memory 102, and proceeds to step S14. In step S14, the running stability determination unit 36 determines whether the ZMP calculated in step S13 is within the stable region SA. In step S14, when the running stability determination unit 36 determines that the ZMP is within the stable region SA, it sets a flag indicating that the state of the vehicle body 16 at the node is stable, and proceeds to step S17. In step S14, when the running stability determination unit 36 determines that the ZMP is not within the stable region SA, it sets a flag indicating that the state of the vehicle body 16 at the node is unstable, and proceeds to step S15.

[0120] In step S15, the stable running plan unit 23 determines whether the number of calculation times m matches the maximum number of calculation times M. In step S15, when it is determined that the number of calculation times m does not match the maximum number of calculation times M, the process returns to step S10. In step S15, when it is determined that the number of calculation times m matches the maximum number of calculation times M, the process proceeds to step S16. That is, in step S15, when it is determined that the number of calculation times m of the target vehicle speed and the target height at the nth node has reached the maximum number of calculation times M, the process proceeds to step S16.

[0121] In step S16, the stable running plan unit 23 determines the modification (recalculation) of the running route R and ends the process shown in the flowchart of FIG. 10. In step S16, when the modification (recalculation) of the running route R is determined, the switching position setting unit 21 moves the switching position P0 by a predetermined distance in a direction away from the target excavation position P1 and the target loading position P2 and sets it as a new switching position P0. Further, the route generation unit 22 performs a recalculation of the running route R based on the target excavation position P1 and the target loading position P2, and the new switching position P0 calculated by the switching position setting unit 21.

[0122] In step S17, the running stability determination unit 36 determines whether the node number n matches 1. In the present embodiment, the target bending angle, the target vehicle speed, and the target lift arm height are sequentially calculated from the node number n = N to the node number n = 1. That is, the process of step S17 corresponds to a process of determining whether the calculation of the target bending angle, the target vehicle speed, and the target lift arm height for all nodes on the travel route R has been completed.

[0123] If it is determined in step S17 that the node number n does not match 1, that is, if it is determined that the calculation of the target bending angle, the target vehicle speed, and the target lift arm height for all nodes on the travel route R has not been completed, the process proceeds to step S4. In step S4, the node to be calculated is changed to an adjacent node, and in the subsequent process, the process of calculating the target bending angle, the target height, and the target lift arm height at that node is executed.

[0124] If it is determined in step S17 that the node number n matches 1, that is, if it is determined that the calculation of the target bending angle, the target vehicle speed, and the target lift arm height for all nodes on the travel route R has been completed, the process shown in the flowchart of FIG. 10 ends.

[0125] When it is determined in the process of step S17 that the node number n matches 1, the operation command unit 24 generates an operation command based on the travel plan information constituted by the target bending angle, the target vehicle speed, and the target lift arm height at each node on the travel route R calculated in the stable travel plan process shown in FIG. 10, and outputs it to the vehicle control controller C4. Thereby, the automatic running of the wheel loader 1 is started. That is, the determination process of step S17 corresponds to a process of determining whether the condition for starting the automatic running of the wheel loader 1 (hereinafter, also referred to as the running start condition) is satisfied.

[0126] An example of the calculation content of the control device 100 according to this embodiment is as follows. As shown in FIG. 3, the wheel loader 1 repeats loader operations. When the vehicle is located at the switching position P0, the control device 100 sets the target excavation position P1 and the target azimuth angle A1 at that position, the target loading position P2 and the target azimuth angle A2 at that position, as well as the target switching position P0 and the target azimuth angle A0 at that position based on the data of the video captured by the imaging device 15, and generates travel routes R1 to R4 based on the set information.

[0127] The control device 100 calculates travel plan information including the target vehicle speed, the target lift arm height, and the target bend angle at each node where travel is possible while ensuring travel stability on the travel route R1, and generates an operation command based on the calculated travel plan information. The control device 100 controls each part based on the generated operation command and runs the vehicle along the travel route R1. When the vehicle reaches the target excavation position P1, the excavation work is automatically performed. When the excavation work is completed, the control device 100 calculates travel plan information including the target vehicle speed, the target lift arm height, and the target bend angle at each node where travel is possible while ensuring travel stability on the travel route R2, and generates an operation command based on the calculated travel plan information. The control device 100 controls each part based on the generated operation command and runs the vehicle along the travel route R2. When the vehicle reaches the target switching position P0, the control device 100 calculates travel plan information including the target vehicle speed, the target lift arm height, and the target bend angle at each node where travel is possible while ensuring travel stability on the travel route R3, and generates an operation command based on the calculated travel plan information. The control device 100 controls each part based on the generated operation command and runs the vehicle along the travel route R3. When the vehicle reaches the target loading position P2, the loading work is automatically performed. When the loading work is completed, the control device 100 calculates travel plan information including the target vehicle speed, the target lift arm height, and the target bend angle at each node where travel is possible while ensuring travel stability on the travel route R4, and generates an operation command based on the calculated travel plan information.

[0128] Before calculating the target vehicle speed, target lift arm height, and target bending angle at each node of the travel route R, the control device 100 calculates the load in the bucket. The control device 100 calculates the target vehicle speed and target lift arm height at the final node of each travel route R (steps S5, S8).

[0129] After that, the control device 100 sequentially calculates the target bending angle, target vehicle speed, and target lift arm height at nodes other than the final node (steps S5, S11). The control device 100 determines whether the state of the vehicle body 16 at the node being calculated is stable or unstable based on the calculated target bending angle, target vehicle speed, and target lift arm height (steps S12, S13, S14).

[0130] If it is determined that the state of the vehicle body 16 at the node being calculated is unstable, the target vehicle speed and target lift arm height are corrected (No in step S14, No in step S15, S10, S11). The control device 100 determines whether the state of the vehicle body 16 at the node being calculated is stable or unstable based on the target bending angle, the corrected target vehicle speed, and the target lift arm height (steps S12, S13, S14).

[0131] When it is determined that the state of the vehicle body 16 at the node being calculated is stable (Yes in step S14), the target vehicle speed and target lift arm height used for that determination become the target values used in the calculation of the operation command. After that, the control device 100 executes the same process with the next node as the calculation target.

[0132] That is, the control device 100 repeatedly performs the processes of steps S5 to S7, S9 to S14, and S17. As a result, the target bending angle, target vehicle speed, and target lift arm height at each node are calculated in order from the node at the travel end position (final node) to the node at the travel start position.

[0133] Note that when the control device 100 repeatedly performs a series of arithmetic operations including the calculation of the target vehicle speed and the target lift arm height and the determination process of the running stability up to the maximum number of arithmetic operations M, and the state of the vehicle body 16 does not become stable, the control device 100 determines to correct (recalculate) the travel route R (Yes in step S15, S16).

[0134] As described above, in the present embodiment, the control device 100 evaluates the running stability of the wheel loader (vehicle) 1 based on the target bending angle, the target vehicle speed, and the target lift arm height, and corrects the target bending angle, the target vehicle speed, and the target lift arm height when the running stability is low (unstable). For example, on the travel route R3, in the deceleration region DA in front of the target loading position (travel end position), the vehicle body 16 decelerates with the lift arm height being high, so the running stability tends to be low. In the present embodiment, the control device 100 first determines the target vehicle speed and the target lift arm height at the travel end position (target loading position), and calculates the target vehicle speed and the target lift arm height that can maintain the running stability on the travel route from the travel end position to the travel start position. Therefore, according to the present embodiment, compared with the case where the calculations are performed in order from the node at the travel start position (target switching position) to the node at the travel end position (target loading position), the calculation time (calculation load) can be reduced.

[0135] In the determination process of step S17, when it is determined that the calculation process of the target bending angle, the target vehicle speed, and the target lift arm height at the travel start position is completed and the stable travel plan process shown in FIG. 10 is completed, the vehicle control controller C4 determines that the travel start condition is satisfied. Then, based on the travel route R and the target bending angle, the target vehicle speed, and the target lift arm height set for each node of the travel route R, the vehicle control controller C4 starts the automatic travel of the wheel loader 1.

[0136] According to the above-described embodiment, the following operational effects can be obtained.

[0137] (1) The wheel loader 1 includes a vehicle body 16 in which a front body 11 having front wheels 4a and a rear body 12 having rear wheels 4b are flexibly connected, a lift arm 2 rotatably provided on the front body 11, a bucket 3 rotatably provided on the lift arm 2, a traveling device 28 for traveling the vehicle body 16, a steering device 19 for changing the bending angle and steering by bending the vehicle body 16, and a control device 100 for generating a traveling route R based on an excavation position and a loading position at a work site and controlling the traveling device 28 and the steering device 19 so that the vehicle body 16 travels along the generated traveling route R.

[0138] Based on the generated traveling route R1, the control device 100 calculates a target bending angle, a target lift arm height, and a target vehicle speed on the traveling route R1. The control device 100 calculates the center of gravity position G of the wheel loader 1 based on the calculated target bending angle and the calculated target lift arm height. The control device 100 determines the traveling stability of the vehicle body 16 based on the calculated target bending angle, the calculated target vehicle speed, and the calculated center of gravity position, and controls the traveling device 28 and the steering device 19.

[0139] With this configuration, it is possible to appropriately determine whether stable automatic traveling is possible on the traveling route R. In the present embodiment, the wheel loader 1 does not start traveling until traveling stability is determined to be stable at all nodes on the traveling route R. For this reason, it is possible to prevent the wheel loader 1 from assuming an unstable posture during automatic driving. That is, according to the present embodiment, the wheel loader 1 can be stably automatically traveled along the generated traveling route R1.

[0140] (2) The control device 100 stores in the storage device (non-volatile memory 102) a travel plan information (data table) that associates a plurality of positions (nodes) on the generated travel route R with the target bending angle, the target lift arm height, and the target vehicle speed at the plurality of positions. When it is determined that the state of the vehicle body 16 is unstable, the control device 100 corrects the target vehicle speed and the target lift arm height. When it is determined that the state of the vehicle body 16 is stable, the control device 100 does not correct the target vehicle speed and the target lift arm height. The control device 100 controls the steering device 19, the traveling device 28, and the lift arm 2 based on the travel plan information (data table) stored in the storage device (non-volatile memory 102).

[0141] In this configuration, the target vehicle speed and the target lift arm height are corrected when it is determined that the state of the vehicle body 16 is unstable by the running stability determination process. As a result of the correction of the target vehicle speed and the target lift arm height, when it is determined that the state of the vehicle body 16 is stable, the target vehicle speed and the target lift arm height used for the determination are stored and held in association with the positions on the travel route R as target values for operation commands. That is, in this configuration, the target vehicle speed and the target lift arm height are corrected at a plurality of positions on the travel route R until it is determined that the state of the vehicle body 16 is stable. As a result, the wheel loader 1 can be stably automatically traveled along the travel route R.

[0142] (3) The wheel loader 1 is provided with a load weight detection device 50 that detects the load weight (load within the bucket) of the load loaded in the bucket 3. The control device 100 calculates the support polygon SP based on the calculated target bending angle. The control device 100 calculates the center of gravity position G based on the load weight (load within the bucket) of the load detected by the load weight detection device 50, the calculated target lift arm height, and the calculated target bending angle. The control device 100 calculates the vector of the force F0 (the resultant force of the gravitational force F1, the centrifugal force F2, and the inertial force F3) acting on the center of gravity position G based on the calculated center of gravity position G and the calculated target vehicle speed. The control device 100 calculates the ZMP, which is the point where the vector of the calculated force F0 intersects the running surface. The control device 100 determines the running stability of the vehicle body 16 based on the positional relationship between the calculated support polygon SP and the calculated ZMP.

[0143] In this configuration, based on the load within the bucket detected before the start of autonomous driving, the center of gravity position G of the wheel loader 1 at each position on the travel route R can be accurately calculated. Therefore, the running stability of the vehicle body 16 at each position on the travel route R can be more appropriately determined. As a result, high running stability can be ensured during autonomous driving.

[0144] (4) The control device 100 sets a stability region SA smaller than the calculated support polygon SP inside the calculated support polygon SP. When the calculated ZMP is within the set stability region SA, the control device 100 determines that the state of the vehicle body 16 is stable. When the calculated ZMP is not within the set stability region SA, the control device 100 determines that the state of the vehicle body 16 is unstable.

[0145] In this configuration, the running stability of the vehicle body 16 at each position on the travel route R at the work site where the ground is uneven can be appropriately determined. As a result, even when the running surface (ground) at the work site is uneven, high running stability can be ensured during autonomous driving.

[0146] (5) The wheel loader 1 is provided with a vehicle speed sensor 45 that detects the actual vehicle speed of the wheel loader 1 traveling along the generated travel route R. The control device 100 stores, in association with each other in a storage device (non-volatile memory 102), data representing the difference between the position on the generated travel route R, the actual vehicle speed detected by the vehicle speed sensor 45 at that position, and the calculated target vehicle speed. The control device 100 calculates the ZMP taking into account the data representing the difference between the actual vehicle speed stored in the storage device (non-volatile memory 102) and the calculated target vehicle speed.

[0147] In this configuration, since the data representing the difference between the target vehicle speed and the actual vehicle speed is taken into account and the ZMP is calculated, the running stability can be accurately determined. As a result, even in a case where a difference occurs between the target vehicle speed and the actual vehicle speed due to the ground conditions at the work site, individual differences of the wheel loader 1, etc., the running stability of the vehicle body 16 at each position on the travel route R can be appropriately judged. Thereby, high running stability can be ensured during automatic driving.

[0148] (6) The wheel loader 1 is provided with an object detection device 56 that detects objects around the vehicle body 16. The control device 100 sets a target excavation position P1 and a target loading position P2 at the work site based on the detection result of the object detection device 56. The control device 100 sets a target turning position P0 based on the set target excavation position P1 and the set target loading position P2. The control device 100 generates a travel route R1 for excavation work from the set target turning position P0 to the set target excavation position P1, a first return travel route R2 from the set target excavation position P1 to the set target turning position P0, a travel route R3 for loading work from the set target turning position P0 to the set target loading position P2, and a second return travel route R4 from the set target loading position P2 to the set target turning position P0.

[0149] In this configuration, even when the situation around the vehicle body 16 changes, such as the shape of the ground 91 changing or the dump truck 92 being replaced, due to the loader operation being repeatedly performed by automatic driving, the target excavation position P1, the target loading position P2, and each travel route R1 to R4 are appropriately set. Thereby, the working efficiency of the wheel loader 1 can be improved.

[0150] (7) When the control device 100 determines that the state of the vehicle body 16 is unstable, it performs a correction to lower the target vehicle speed and the target lift arm height. Thereby, the target vehicle speed and the target lift arm height at which the state of the vehicle body 16 is determined to be stable can be appropriately calculated.

[0151] (8) The control device 100 corrects the target vehicle speed and the target lift arm height at the same position on the generated travel route R a predetermined number of times (M - 1 times). When the state of the vehicle body 16 is not determined to be stable, it corrects the travel route R.

[0152] In this configuration, it is determined by the control device 100 that high running stability cannot be ensured only by correcting the target vehicle speed and the target lift arm height, and the travel route R is corrected (recalculated). Thereby, even when it is determined that high running stability cannot be ensured in the travel route R that is the calculation target, the control device 100 can appropriately determine whether stable automatic driving is possible again in the corrected travel route R.

[0153] Note that the present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. The following modifications are also within the scope of the present invention, and it is also possible to combine the configurations shown in the modifications with the configurations described in the above-described embodiments, or to combine the configurations described in the following different modifications with each other.

[0154] <Modification Example 1> In the above-described embodiment, an example has been described in which, in each of the travel routes R1 to R4, the region surrounded by a plurality of lines obtained by offsetting each side constituting the support polygon SP by a predetermined distance inside the support polygon SP is set as the stable region SA. However, the present invention is not limited to this. In the loader operation, before the excavation position in the travel route R1, before the turning point in the travel routes R2 and R4, and before the loading position in the travel route R3, since the vehicle is decelerating, the vehicle is likely to become unstable. In particular, before the loading position in the travel route R3, since the lifting operation is being performed, the vehicle is likely to become unstable. Therefore, the stable region SA used for determining the running stability in the travel route R3 may be set smaller than the stable region SA used for determining the running stability in the travel routes R1, R2, and R4. Thereby, when the operation of raising the lift arm (rise run) is performed while traveling by automatic driving, the vehicle can be made to travel with higher stability.

[0155] Furthermore, even for the same travel route, the size of the stable region SA may be changed according to the position. For example, in the travel route R3, deceleration is performed in a state where the lift arm height is high before the loading position.

[0156] Therefore, the control device 100 may set the stable region SA to be smaller as it approaches the set target loading position P2 in the travel route R3 for the loading operation. For example, the control device 100 sets the size of the stable region SA in the deceleration region DA of the travel route R3 shown in FIG. 3 to be smaller than the size of the stable region SA outside the deceleration region DA of the travel route R3.

[0157] According to this configuration, the vehicle can be made to travel with higher stability before the loading position in the travel route R3.

[0158] <Modification 2> In the above-described embodiment, an example in which the stable region SA is set inside the support polygon SP has been described. However, the present invention is not limited to this. When there is a ZMP within the support polygon SP without setting the stable region SA, the control device 100 may determine that the state of the vehicle body 16 is stable, and when there is no ZMP within the support polygon SP, the control device 100 may determine that the state of the vehicle body 16 is unstable.

[0159] <Modification Example 3> In the above-described embodiment, an example in which the control device 100 makes a correction to lower both the target vehicle speed and the target lift arm height used for the determination when it is determined that the state of the vehicle body 16 is unstable has been described. However, the present invention is not limited to this. When it is determined that the state of the vehicle body 16 is unstable, the control device 100 may make a correction to lower only one of the target vehicle speed and the target lift arm height used for the determination.

[0160] When it is determined that the state of the vehicle body 16 is unstable, the control device 100 can appropriately calculate the target vehicle speed and the target lift arm height at which the state of the vehicle body 16 is determined to be stable by making a correction to lower at least one of the target vehicle speed and the target lift arm height.

[0161] <Modification Example 4> The control device 100 may be configured to include a lift arm priority mode, a vehicle speed priority mode, and a normal mode, and one calculation mode may be set according to the operator's operation from among the lift arm priority mode, the vehicle speed priority mode, and the normal mode. The control device 100 sets the calculation mode according to a mode selection signal from the input device 38 as a mode selection operation unit provided in the driver's cab 5. Further, the control device 100 sets the calculation mode according to a mode selection signal acquired via the communication device 46 from the input device 72 as a mode selection operation unit provided in the remote operation device 70.

[0162] The lift arm priority mode is an operation mode in which, when it is determined that the state of the vehicle body 16 is unstable, the target vehicle speed is corrected and the target lift arm height is not corrected. The vehicle speed priority mode is an operation mode in which, when it is determined that the state of the vehicle body 16 is unstable, the target lift arm height is corrected and the target vehicle speed is not corrected. The normal mode is an operation mode in which, when it is determined that the state of the vehicle body 16 is unstable, both the target vehicle speed and the target lift arm height are corrected. The operator can select one operation mode from the lift arm priority mode, the vehicle speed priority mode, and the normal mode by operating the mode selection operation unit (input devices 38, 72). That is, the operator can freely select the method of correcting the target value when it is determined that the state of the vehicle body 16 is unstable.

[0163] <Modification Example 5> In the above embodiment, an example in which the wheel loader 1 includes the object detection device 56 that detects objects such as the ground 91 and the dump truck 92 based on the data of the video captured by the imaging device 15 has been described, but the present invention is not limited thereto. The object detection device 56 may be a device that detects an object based on the detection results of an ultrasonic sensor, a millimeter wave sensor, a lidar sensor, an infrared sensor, or the like.

[0164] <Modification Example 6> In the above embodiment, an example of obtaining the load in the bucket calculated by the load detection device 50 when determining the running stability on each running route R1 to R4 (see step S2 in FIG. 10) has been described, but the present invention is not limited thereto. The load in the bucket may be a predetermined load W stored in advance in the non-volatile memory 102. For example, the predetermined loads W1 and W4 used for determining the running stability of the running routes R1 and R4 are 0 (zero), and the predetermined loads W2 and W3 used for determining the running stability of the running routes R2 and R3 are values greater than 0 (zero). The predetermined loads W2 and W3 can be determined, for example, by discharging the earth and sand loaded in the bucket 3 in the loader work to a load measuring device provided outside the wheel loader 1 by actual machine tests and measuring the load.

[0165] <Modification Example 7> In the above-described embodiment, the control device 100 has been described as an example of setting the target excavation position P1 and the target loading position P2 at the work site based on the detection result of the object detection device 56. However, the present invention is not limited to this. For example, the control device 100 may set the target excavation position P1 and the target loading position P2 at the work site based on the coordinates input from the input device 38 according to the operation of the operator. The control device 100 may set the target excavation position P1 and the target loading position P2 at the work site based on the coordinates transmitted from the remote operation device 70.

[0166] <Modification Example 8> The control device 100 may display the determination result of the running stability on the display device 39 in the driver's cab 5. Further, the control device 100 may transmit the determination result of the running stability to the remote operation device 70 via the communication device 46. The remote operation controller C5 of the remote operation device 70 causes the display device 73 to display the determination result of the running stability. According to this configuration, by looking at the images displayed on the display devices 39 and 73, the operator can determine whether to automatically operate the wheel loader 1 in the current situation around the vehicle body 16.

[0167] <Modification Example 9> The configuration of the wheel loader 1 is not limited to the example described in the above embodiment. The wheel loader 1 may have a configuration including, for example, a power generation motor mechanically connected to the engine 40 and a traveling motor that is rotationally driven by the electric power generated by the power generation motor to operate the traveling device. That is, the wheel loader 1 may be provided with a hybrid type power transmission mechanism that converts the power of the engine 40 into electricity and transmits it to the wheels 4. Further, the wheel loader may be provided with an HST (Hydro Static Transmission) type power transmission mechanism that converts the power of the engine 40 into hydraulic pressure and transmits it to the wheels 4.

[0168] As described above, embodiments of the present invention have been explained. However, the above embodiments merely show some 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.

Explanation of Signs

[0169] 1…Wheel loader (vehicle), 2…Lift arm, 3…Bucket, 4…Wheel, 4a…Front wheel, 4b…Rear wheel, 7…Arm cylinder (hydraulic cylinder), 8…Bucket cylinder (hydraulic cylinder), 11…Front body, 12…Rear body, 13…Center pin, 14…Steering cylinder (hydraulic cylinder), 15…Imaging device, 16…Vehicle body, 17…Working device, 18…Brake device, 19…Steering device, 21…Switching position setting unit, 22…Path generation unit, 23…Stable travel planning unit, 24…Operation command unit, 25…Feedback unit, 28…Travel device, 30…Bending angle calculation unit, 31…Center of gravity calculation unit, 32…ZMP calculation unit, 33…Support polygon calculation unit, 34…Stable region setting unit, 35…Height calculation unit, 36…Travel stability determination unit, 37…Vehicle speed calculation unit, 38…Input device, 39…Display device, 40…Engine, 41…Arm angle sensor, 42…Bucket angle sensor, 43…Pressure sensor, 44…Bending angle sensor, 45…Vehicle speed sensor, 46…Communication device, 47…Position detection device, 50…Load weight detection device, 56…Object detection device, 60A, 60B, 60C…Hydraulic pumps, 61…Front control unit, 62…Brake control unit, 63…Steering control unit, 64…Transmission control unit, 65…Engine control unit, 70…Remote operation device, 71…Communication device, 72…Input device, 73…Display device, 91…Ground (excavation target), 92…Dump truck (transport vehicle), 100…Control device, 101…Processing device, 102…Non-volatile memory (storage device), C…Controller, C1…Travel planning controller, C2…Position setting controller, C3…Load calculation controller, C4…Vehicle control controller, C5…Remote operation controller, DA…Deceleration region, F0…Force acting on the center of gravity position G (resultant force of gravity F1, centrifugal force F2, and inertial force F3), P0…Target switching position, P1…Target excavation position, P2…Target loading position, Pt1, Pt2, Pt3, Pt4…Contact points, R…Travel route, SA…Stable region, SP…Support polygon

Claims

1. A vehicle body in which a front body having front wheels and a rear body having rear wheels are flexibly connected, A lift arm rotatably provided on the front body, A bucket rotatably provided on the lift arm, A traveling device for traveling the vehicle body, A steering device that changes the bending angle by bending the vehicle body and steers, Based on the excavation position and the loading position at the work site, a travel route is generated, and the lift arm is raised from a predetermined travel start position on the travel route toward the loading position so that the height of the lift arm at the loading position becomes the loading height. A control device that controls the traveling device, the lift arm, and the steering device so that the vehicle body travels along the traveling route, in a wheel loader provided with: The control device is Based on the generated travel route, calculates target bending angles at a plurality of positions on the travel route, Sets target vehicle speeds at a plurality of positions on the travel route to a predetermined initial vehicle speed value, Sets target lift arm heights at a plurality of positions on the travel route to a predetermined initial height value, Calculates the center of gravity position of the wheel loader based on the target bending angle and the target lift arm height, Determines the running stability of the vehicle body at each of a plurality of positions on the travel route based on the target bending angle, the target vehicle speed, and the center of gravity position, When it is determined that the state of the vehicle body is unstable, repeatedly corrects the target vehicle speed and the target lift arm height to be lowered until it is determined that the state of the vehicle body is stable, Stores in a storage device travel plan information associating a plurality of positions on the travel route with the target bending angle, the target lift arm height, and the target vehicle speed at the plurality of positions, Controls the steering device, the lift arm, and the traveling device based on the travel plan information stored in the storage device A wheel loader characterized by the above.

2. In the wheel loader according to claim 1, It is provided with a load weight detection device that detects the weight of the load loaded on the bucket, The control device is Based on the calculated target bending angle, calculates a support polygon, Calculates the center of gravity position based on the weight of the load detected by the load weight detection device, the target lift arm height, and the target bending angle, Based on the center-of-gravity position and the target vehicle speed, calculate the vector of the force acting on the center-of-gravity position. Calculate the ZMP, which is the point where the calculated vector of the force intersects the running surface. Determine the running stability of the vehicle body based on the positional relationship between the calculated support polygon and the calculated ZMP. A wheel loader characterized by the above.

3. In the wheel loader according to claim 2, The control device, Set a stable region smaller than the calculated support polygon inside the calculated support polygon. If the calculated ZMP is within the set stable region, determine that the state of the vehicle body is stable; if the calculated ZMP is not within the set stable region, determine that the state of the vehicle body is unstable. A wheel loader characterized by the above.

4. In the wheel loader according to claim 3, Equipped with a vehicle speed sensor that detects the actual vehicle speed of the wheel loader traveling along the generated travel route. The control device, Associate the position on the generated travel route, the data representing the difference between the actual vehicle speed detected by the vehicle speed sensor at that position and the target vehicle speed, and store them in the storage device. Calculate the ZMP taking into account the data representing the difference between the actual vehicle speed and the target vehicle speed stored in the storage device. A wheel loader characterized by the above.

5. In the wheel loader according to claim 3, Equipped with an object detection device that detects objects around the vehicle body. The control device, Based on the detection result of the object detection device, set a target excavation position and a target loading position at the work site. Based on the set target excavation position and the set target loading position, set a target turning position. Generate the travel route for excavation work from the set target turning position to the set target excavation position, the travel route for the first return from the set target excavation position to the set target turning position, the travel route for loading work from the set target turning position to the set target loading position, and the travel route for the second return from the set target loading position to the set target turning position. A wheel loader characterized by the above.

6. In the wheel loader according to claim 5, The control device, In the travel route for the loading operation, as it approaches the set target loading position, the stable region is set to be smaller. A wheel loader characterized by this.

7. In the wheel loader according to Claim 1, the control device corrects the target vehicle speed and the target lift arm height at the same position on the generated travel route a predetermined number of times, and if the state of the vehicle body is not determined to be stable, corrects the travel route. A wheel loader characterized by this.

8. In the wheel loader according to Claim 1, the control device has a lift arm priority mode in which, when the state of the vehicle body is determined to be unstable, the target vehicle speed is corrected and the target lift arm height is not corrected, and a vehicle speed priority mode in which, when the state of the vehicle body is determined to be unstable, the target lift arm height is corrected and the target vehicle speed is not corrected, and a normal mode in which, when the state of the vehicle body is determined to be unstable, both the target vehicle speed and the target lift arm height are corrected. One mode is configured to be set according to the operator's operation from among the lift arm priority mode, the vehicle speed priority mode, and the normal mode. A wheel loader characterized by this.

Images