JP7712239B2 - Wheel Loader - Google Patents

Description

The present invention relates to a wheel loader that can generate a travel route and automatically travel along the travel route.

When performing excavation and loading work with a wheel loader, the excavation position and loading position change as the work progresses. Therefore, when performing excavation and loading work using automatic driving of a wheel loader, the wheel loader needs to automatically generate a travel path in response to changes in the excavation position and loading position.

Patent Document 1 discloses a method for automatically generating driving routes for unmanned vehicles such as dump trucks, which aims to solve the problem of minimizing costs associated with driving by generating an optimal driving route that satisfies the minimum constraints under which the vehicle can travel, while also minimizing the load on the tires and vehicle body, shortening the time required for travel, and allowing the vehicle to travel with low fuel consumption.

JP 2010-73080 A

After excavation work, a wheel loader performs an operation of running with the lift arm raised (rise run) when loading the excavated material onto a transport vehicle such as a dump truck. When such an operation is performed, the wheel loader's center of gravity becomes higher due to the lift arm raising operation, and furthermore, the vehicle body becomes unstable because it decelerates in front of the transport vehicle. In Patent Document 1, the stability of the unmanned vehicle while it is running is not taken into consideration, and there is a risk that stable automatic running will not be possible if the wheel loader is tried to run along the generated running path.

The present invention aims to provide a wheel loader that can automatically travel stably along a generated travel route.

A wheel loader according to one aspect of the present invention comprises a vehicle body having a front body having front wheels and a rear body having rear wheels which are flexibly connected, a lift arm rotatably attached to the front body, a bucket rotatably attached to the lift arm, a traveling device which travels the vehicle body, a steering device which steers the vehicle body by bending the vehicle body to change the bending angle, and a control device which generates a traveling path based on an excavation position and a loading position at a work site , and controls the traveling device, the lift arm, and the steering device so that the vehicle body travels along the traveling path while raising the lift arm from a predetermined traveling start position on the traveling path toward the loading position so that the height of the lift arm at the loading position becomes the loading height. the control device calculates target bending angles at a plurality of positions on the travel path based on the generated travel path , sets target vehicle speeds at the plurality of positions on the travel path to predetermined initial vehicle speed values, sets target lift arm heights at the plurality of positions on the travel path to predetermined initial height values, calculates a center of gravity position of the wheel loader based on the target bending angle and the target lift arm height, determines the traveling stability of the vehicle body at each of the plurality of positions on the travel path based on the target bending angle, the target vehicle speed and the center of gravity position , and if 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 lower until it is determined that the state of the vehicle body is stable, stores in a storage device travel plan information that associates the plurality of positions on the travel path with the target bending angles, the target lift arm heights and the target vehicle speeds at the plurality of positions, and controls the steering device, the lift arm and the travel device based on the travel plan information stored in the storage device.

According to the present invention, the wheel loader can be automatically driven stably along the generated driving route.

FIG. 1 is a side view of an automatically operable wheel loader according to an embodiment of the present invention. FIG. 2 is a system configuration diagram of the wheel loader. FIG. 3 is a diagram showing an example of work performed by a wheel loader. FIG. 4 is a diagram showing a hardware configuration of the controller. FIG. 5 is a functional block diagram of the driving plan controller. FIG. 6 is a diagram for explaining the details of the function of the stable driving plan unit. FIG. 7 is a schematic diagram of the wheel loader as viewed from above, showing the support polygon SP and ZMP. FIG. 8 is a schematic diagram of the wheel loader as seen from the side, showing the support polygon SP and ZMP. FIG. 9 is a diagram showing the relationship between the deceleration, the lift arm height, the bending angle of the vehicle body, and the running stability. FIG. 10 is a flowchart showing an example of the flow of a stable driving planning process executed by the stable driving planning unit according to the embodiment of the present invention.

Below, we will explain a wheel loader according to an embodiment of the present invention with reference to the drawings.

Figure 1 is a side view of an automatically operable wheel loader 1 according to an embodiment of the present invention. The wheel loader 1 comprises an articulated vehicle body 16 and an articulated working device 17 attached to the front of the vehicle body 16. The vehicle body 16 comprises a front body 11 with front wheels 4a (wheels 4) attached to the left and right, and a rear body 12 with rear wheels 4b (wheels 4) attached to the left and right. The front body 11 and rear body 12 are connected by a center pin 13 so that they can be bent in the left-right direction.

The wheel loader 1 is equipped with a steering device 19 that changes the bending angle by bending the vehicle body 16 to steer. 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.

The working device 17 is attached to the front body 11. The working device 17 includes a lift arm 2 attached to the front body 11 so as to be rotatable in the vertical direction, a bucket 3 attached to the tip of the lift arm 2 so as to be rotatable in the vertical direction, a hydraulic cylinder (hereinafter also referred to as an arm cylinder) 7 that drives the lift arm 2, and a hydraulic cylinder (hereinafter also referred to as a bucket cylinder) 8 that drives the bucket 3. The lift arm 2 and the arm cylinder 7 are provided on each side 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, which causes the orientation of the bucket 3 to move up and down.

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

The wheel loader 1 is steered by the relative rotation of the front body 11 and rear body 12 caused by the extension and retraction of a pair of left and right steering cylinders 14. When the right steering cylinder 14 retracts and the left steering cylinder 14 extends, the vehicle body 16 bends to the right. When the left steering cylinder 14 retracts and the right steering cylinder 14 extends, the vehicle body 16 bends to the left. In this specification, the bending angle corresponds to the rotation angle around the center pin 13. The bending angle is 0 (zero)° when the vehicle is not bent, that is, when the wheel loader 1 is in a straight-ahead position. The bending angle is a positive value when the vehicle body 16 is bent to the right, and a negative value when the vehicle body 16 is bent to the left.

<System Configuration>
Figure 2 is a system configuration diagram of the wheel loader 1. As shown in Figure 2, the wheel loader 1 comprises a traveling device 28 that travels the vehicle body 16, a working device 17 that performs excavation work, a steering device 19 that steers the vehicle body 16, a braking device 18 that brakes the vehicle body 16 and inhibits the vehicle body 16 from moving when stopped, an engine 40 that serves as a drive source for these devices, a control device 100 that controls each part of the wheel loader (hereinafter also referred to as vehicle) 1, and hydraulic pumps 60A, 60B, 60C that are mechanically connected to the engine 40.

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

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

The 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, for example, an internal combustion engine such as a diesel engine. The wheel loader 1 is equipped with an engine control unit 65 that controls the operation of the engine 40. The engine control unit 65 controls the amount of fuel injection so that the actual rotation speed detected by the engine rotation speed sensor approaches the target rotation speed calculated by the control device 100.

The arm cylinder 7 and bucket cylinder 8 are extended and retracted by hydraulic oil (pressurized oil) discharged from the hydraulic pump 60A, which rotates due to the torque output by the engine 40.

The traveling device 28 has wheels 4 and a power transmission device that transmits 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, etc.

The input shaft of a 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 a transmission 52. The torque converter 51 is a well-known fluid clutch consisting of an impeller, turbine, and stator, and the rotation of the engine 40 is transmitted to the transmission 52 via the torque converter 51. The transmission 52 has a clutch that switches its speed stages between 1st and 5th gears, and the rotation of the output shaft of the torque converter 51 is changed by the transmission 52. After the change in speed, the rotation is transmitted to the wheels 4 via a propeller shaft 53, a differential device 54, and an axle 55, and the wheel loader 1 travels.

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

Hydraulic pumps 60A, 60B, and 60C are mechanically connected to the engine 40. Hydraulic pumps 60A, 60B, and 60C are driven by the torque output by the engine 40 to discharge hydraulic oil.

The hydraulic oil supplied from the hydraulic pump 60A to the arm cylinder 7 and bucket cylinder 8 has its pressure, flow rate, and flow direction controlled by the front control unit 61. This allows the work device 17 to perform excavation and loading operations. The hydraulic oil supplied from the hydraulic pump 60B to the brake cylinder 18a and parking brake cylinder 18b has its pressure, flow rate, and flow direction controlled by the brake control unit 62. This allows the brake device 18 to brake and stop the vehicle body 16. The hydraulic oil supplied from the hydraulic pump 60C to the pair of left and right steering cylinders 14 has its pressure, flow rate, and flow direction controlled by the steering control unit 63. This allows the steering device 19 to steer the vehicle body 16.

As shown in FIG. 1, a number of imaging devices 15 are installed above the cab 5 to capture images of the area around the vehicle body 16. The imaging devices 15 are, for example, wide-angle video cameras equipped with imaging elements such as CCDs and CMOSs that are highly durable and weather resistant, and wide-angle lenses. Data of the images captured by the imaging devices 15 is output to the control device 100.

2, the wheel loader 1 includes an arm angle sensor 41 provided on a connecting shaft connecting the vehicle body 16 and the lift arm 2, and a bucket angle sensor 42 provided on a connecting shaft connecting the lift arm 2 and the bucket 3. The arm angle sensor 41 detects the rotation angle (arm angle) of the lift arm 2 relative 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 relative to the lift arm 2, and outputs a signal representing the detection result to the control device 100. The arm angle and 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, instead of the arm angle sensor 41, a stroke sensor that detects the stroke amount of the arm cylinder 7 may be provided as a posture sensor. Similarly, instead of the bucket angle sensor 42, a stroke sensor that detects the stroke amount of the bucket cylinder 8 may be provided as a posture sensor.

The wheel loader 1 is equipped with multiple pressure sensors. The multiple pressure sensors include a pressure sensor 43 that detects the pressure in the bottom chamber, which is the oil chamber that supports the load, in the arm cylinder 7 and outputs a signal representing the detection result to the control device 100.

The wheel loader 1 is equipped 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 indicating the detection result to the control device 100. The bending angle is a physical quantity that indicates the posture of the vehicle body 16. In other words, the bending angle sensor 44 functions as a posture sensor that detects the posture of the vehicle body 16. Note that instead of the bending angle sensor 44, a stroke sensor that detects the stroke amount of the steering cylinder 14 may be provided as a posture sensor that detects the posture of the vehicle body 16.

The wheel loader 1 is equipped with a vehicle speed sensor 45 that detects the traveling speed of the vehicle (hereinafter also referred to as 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.

The control device 100 generates a travel route based on the excavation position and loading position at the work site, and controls the travel device 28 and steering device 19 so that the vehicle body 16 travels along the generated travel route. This allows the wheel loader 1 to automatically travel to the excavation position and loading position and perform excavation and loading operations.

An example of the work performed by the wheel loader 1 will be described with reference to FIG. 3. As shown in FIG. 3, the wheel loader 1 advances toward the natural ground 91, which is the object to be excavated (first operation), and performs excavation work to excavate the natural ground 91 by inserting the bucket 3 into the natural ground 91 and operating the bucket 3 and the lift arm 2 (second operation). After the excavation work is completed, the wheel loader 1 moves backward to a predetermined position and stops (third operation). After that, the wheel loader 1 advances toward the dump truck 92 while raising the lift arm 2 (fourth operation) (rise run) and stops at a loading position in front of the dump truck 92. Then, (fifth operation) a loading work is performed to dump the load (excavated material) in the bucket 3 onto the bed of the dump truck 92. After the loading work is completed, the wheel loader 1 moves backward to a predetermined position (sixth operation). The wheel loader 1 repeats a series of operations (first operation) to (sixth operation) while tracing a V-shaped trajectory as described above. In this specification, the series of operations from (1st operation) to (6th operation) is also referred to as the loader operation.

In the fourth operation (rise run), the lifting operation of the lift arm 2 raises the center of gravity of the wheel loader 1. The wheel loader 1 also decelerates 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, particularly the vehicle body 16, is likely to become unstable. In this embodiment, before automatic driving is performed, it is determined whether the wheel loader 1 can travel stably along the travel route. The process of generating the travel route used during automatic driving of the wheel loader 1, the process of determining the travel stability on the travel route performed before the start of automatic driving, and the control of automatic driving will be described in detail later.

As shown in FIG. 2, the wheel loader 1 is equipped with an input device 38, a display device 39, and a communication device 46, which are provided in the driver's cab 5. The communication device 46 is a wireless communication device capable of wireless communication with a wireless base station that constitutes part of the communication line 90, and has a communication interface including a communication antenna that has a sensitivity band of, for example, the 2.1 GHz band. The communication device 46 transmits and receives information to and from the remote control device 70 via the communication line 90. The communication line 90 is a wide area network such as a mobile phone communication network (mobile communication network) deployed by a mobile phone operator or the like, or the Internet.

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 that is overlaid on the display screen of the display device 39. The input device 38 is operated by an operator, and inputs instructions corresponding to the operation to the control device 100. When an instruction to start automatic driving is input from the input device 38 to the control device 100, the control device 100 executes control to start automatic driving of the wheel loader 1. Note that the control device 100 also executes control to start automatic driving of the wheel loader 1 when it acquires an automatic driving start command transmitted from the remote control device 70 described later.

The control device 100 according to this embodiment has multiple controllers C1, C2, C3, and C4. Note that the multiple controllers C1, C2, C3, and C4 constituting the control device 100 and the controller C5 of the remote control device 70 described below have the same configuration, and therefore may be collectively referred to as controller C below.

The remote control device 70 transmits and receives information to and from the control device 100 of the wheel loader 1 via a communication line 90. The remote control device 70 includes a remote control controller C5, a communication device 71 for communicating with the wheel loader 1, an input device 72 for inputting operator instructions to the remote control controller C5, and a display device 73 for displaying images on a display screen based on control signals from the remote control controller C5.

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 that is superimposed on the display screen of the display device 73.

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

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

The non-volatile memory 102 stores programs capable of executing various calculations. In other words, the non-volatile memory 102 is a storage device (storage medium) capable of reading programs that realize the functions of this embodiment. The processing device 101 is an arithmetic processing device that expands the programs stored in the non-volatile memory 102 into the volatile memory 103 and executes arithmetic processing. The processing device 101 performs predetermined arithmetic processing on signals received from the input interface 104, the non-volatile memory 102, and the volatile memory 103 in accordance with the programs.

The input interface 104 converts signals input from various devices such as an imaging device, a sensor, and other controllers so that they can be calculated by the processing device 101. The output interface 105 generates an output signal according to the calculation results in the processing device 101, and outputs the signal to various devices such as solenoid valves that control hydraulic equipment.

The multiple image capture devices 15 are connected to a 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 a vehicle control controller C4. The multiple controllers C are connected to each other so that they can communicate with each other via an in-vehicle network 106 called CAN (Controller Area Network). Note that the in-vehicle network 106 may use a communication standard other than CAN, such as Ethernet (registered trademark). This allows the multiple controllers C to exchange information (data) such as sensor detection results and calculation results of the controllers C.

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

The position setting controller C2 detects the pile of natural ground 91 and the dump truck 92 shown in FIG. 3 based on the image data captured by the camera device 15. In other words, the camera device 15 and the position setting controller C2 constitute an object detection device 56 that detects objects around the vehicle body 16. Note that the method for detecting the pile of natural ground 91 and the dump truck 92 can be, for example, a well-known object detection method using a neural network.

The position setting controller C2 sets a 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 based on the detected boundary line B1 between the natural ground 91 and the ground. At the target excavation position P1, the position setting controller C2 sets a target azimuth angle A1 that represents the target orientation of the vehicle body 16, which is a direction perpendicular to the boundary line B1 between the natural ground 91 and the ground.

The position setting controller C2 sets a target position (hereinafter also referred to as a target loading position) P2 of the vehicle body 16 when performing loading work at the work site based on the detected boundary line B2 between the dump truck 92 and the ground. At the target loading position P2, the position setting controller C2 sets a target azimuth angle A2 that represents the target orientation of the vehicle body 16, which is a direction perpendicular to the boundary line B2 between the dump truck 92 and the ground.

The target azimuth angles A1 and A2 are expressed as the angle between the reference azimuth and the traveling direction of the vehicle body 16. The reference azimuth is set to 0°, and the target azimuth angles A1 and A2 take positive values in the illustrated clockwise direction with respect to the reference azimuth, and negative values in the illustrated counterclockwise direction with respect to the reference azimuth. In other words, the target azimuth angles A1 and A2 are set in the range of -180° to +180°. Note that the target azimuth angles A1 and A2 may also be set in the range of 0° to 360° in the illustrated clockwise direction with the reference azimuth being 0°.

The target position is expressed, for example, in coordinates of a global coordinate system. The target position may also be expressed in coordinates of a site coordinate system with a specific position on the work site as its origin. The reference direction is set, for example, to true north. Coordinate conversion is possible between the global coordinate system and the site coordinate system. The position setting controller C2 may capture images of the surroundings of the vehicle body 16 using the imaging device 15, and identify the target position using a vehicle reference coordinate system with the current position of the vehicle as the origin when generating the travel routes R1 to R4, and the forward direction of the vehicle as the reference direction.

The wheel loader 1 is equipped with a position detection device 47 that detects the position of the vehicle itself and outputs a signal representing the detection result to the position setting controller C2. The position detection device 47 has, for example, an antenna for multiple GNSS (Global Navigation Satellite Systems) 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 multiple positioning satellites received by the GNSS antenna.

The position detection device 47 is not limited to this, and may also include a wheel speed sensor and a gyro sensor that detects the rotational speed of the wheels 4. The positioning calculation device calculates the travel distance of the wheel loader 1 based on the detection results of the wheel speed sensor, and calculates the travel direction of the wheel loader 1 based on the detection results of the gyro sensor.

The non-volatile memory 102 of the load calculation controller C3 shown in FIG. 4 stores a formula or a data table used to calculate the load in the bucket from the arm angle, bucket angle, and pressure in the bottom chamber of the arm cylinder 7. The load calculation controller C3 calculates the load in the bucket based on the formula or data table stored in the non-volatile memory 102 and the detection results of the arm angle sensor 41, bucket angle sensor 42, and 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 cargo load detection device 50 that detects the load of the cargo (bucket load) loaded in the bucket 3. Note that the method of detecting the load in the bucket is not limited to this. The cargo load detection device 50 may be composed of 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.

The driving plan controller C1 calculates the driving route R and the target values of the bending angle on the driving 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 vehicle acceleration, deceleration, steering, and lift up based on the calculation results. The functions of the driving plan controller C1 will be described in detail later.

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

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 has an arm flow control valve that controls the flow rate and flow direction of 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 flow direction of 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.

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 flow 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. The arm angle and bucket angle change as the working device 17 operates. Note that the height from the travel 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 as the arm angle changes.

The operation commands include a steering control command calculated based on a target bending angle, which is a target value for the bending angle, a driving control command (accelerator command and brake command) calculated based on a target vehicle speed, which is a target value for the vehicle speed, and an arm control command calculated based on a target lift arm height, which is a target value for the lift arm height.

The vehicle control controller C4 controls the front control unit 61 based on the arm control command included in the operation command from the driving plan controller C1. This controls the operation of the lift arm 2 so that the actual height of the lift arm 2 becomes the target lift arm height. In other words, the driving 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.

The vehicle control controller C4 also controls the steering control unit 63 based on the steering control command included in the operation command from the driving plan controller C1. This controls the operation of the steering device 19 so that the actual bending angle becomes the target bending angle. In other words, the driving 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.

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 driving control command included in the operation command from the driving plan controller C1. This controls the operation of the driving device 28 so that the actual vehicle speed becomes the target vehicle speed. In other words, the driving plan controller C1 and the vehicle control controller C4 operate the driving device 28 so that the actual vehicle speed detected by the vehicle speed sensor 45 becomes the target vehicle speed.

In this 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, but 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. Also, one controller C may have all of the functions of the controllers C1 to C4.

Figure 5 is a functional block diagram of the driving plan controller C1. The driving plan controller C1 functions as a turning position setting unit 21, a route generating unit 22, a stable driving plan unit 23, an operation command unit 24, and a feedback unit 25 by executing a program stored in the non-volatile memory 102.

As described above, when the wheel loader 1 repeatedly travels between the excavation position and the loading position, after an excavation or loading operation, it moves backward once, stops, switches to forward movement, and heads toward the destination position. Hereinafter, the position at which the loader switches from reverse to forward movement during loading operation is referred to as the turning position P0 (see FIG. 3). In this embodiment, a case will be described in which the turning position when heading toward the loading position after an excavation operation is the same as the turning position when heading toward the excavation position after a loading operation, but the two may be set to different positions.

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

A data table (hereinafter also referred to as a position table) showing turning positions according to the excavation position and the loading position is stored in the non-volatile memory 102 of the travel plan controller C1. The position table is determined based on actual testing using the wheel loader 1 operated by an operator. The turning position setting unit 21 refers to the position table and sets the target turning position P0 based on the target positions P1 and P2.

The turning position setting unit 21 determines the target orientation of the target turning position P0 to be an intermediate orientation between the orientation from the target turning position P0 toward the target excavation position P1 and the orientation from the target turning position P0 toward the target loading position P2. The turning position setting unit 21 determines the angle between the determined target orientation and the reference orientation as the target azimuth angle A0.

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

For travel route R1, the target turning position P0 is the travel start position, and the target excavation position P1 is the travel end position. For travel route R2, the target excavation position P1 is the travel start position, and the target turning position P0 is the travel end position. For travel route R3, the target turning position P0 is the travel start position, and the target loading position P2 is the travel end position. For travel route R4, the target loading position P2 is the travel start position, and the target turning position P0 is the travel end position. For ease of explanation, travel routes R1 to R4 are collectively referred to as travel route R below.

The route generation unit 22 takes into account the target azimuth angle at the travel start position and the target azimuth angle at the travel end position, and generates a travel route R that does not involve unreasonable steering by connecting the coordinates of the travel start position and the coordinates of the travel end position with a gentle curve.

The smaller the curvature of the driving route R, the higher the driving stability of the vehicle. The shorter the route length of the driving route R, the less energy consumption there is. However, the shorter the route length of the driving route R, the greater the curvature is likely to be. For this reason, it is preferable that the turning position setting unit 21 and the route generation unit 22 set an evaluation function using the calculated total length of the driving route R, the amount of change in the curvature of the driving route R, etc., and determine the turning position P0 and the driving route R that minimize the evaluation function by machine learning. This generates a driving route R that is easy to ensure driving stability and reduces energy consumption.

The stable driving planning unit 23 shown in FIG. 5 is a processing unit that plans stable driving of the wheel loader 1 on the generated driving route R. The stable driving planning unit 23 calculates a target bending angle, a target lift arm height, and a target vehicle speed on the driving route R based on the generated driving route R. The stable driving 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 driving planning unit 23 determines the driving 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.

The functions of the stable driving planner 23 will be described in detail below with reference to Figs. 6 to 10. Fig. 6 is a diagram for explaining the functions of the stable driving planner 23 in detail. As shown in Fig. 6, the stable driving planner 23 functions as a bending angle calculator 30, a support polygon calculator 33, a stable area setting unit 34, a height calculator 35, a vehicle speed calculator 37, a center of gravity calculator 31, a ZMP calculator 32, and a driving stability judgement unit 36.

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 in the non-volatile memory 102 travel plan information that associates a plurality of nodes on the travel route R with the target bending angles at the plurality of nodes.

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. Figure 7 is a schematic diagram of the wheel loader 1 seen from above, showing the support polygon SP. As shown in Figure 7, the support polygon SP is a convex polygonal area formed by the sides connecting the ground contact points Pt1 to Pt4 of the wheels 4 of the wheel loader 1.

Specifically, the support polygon calculation unit 33 calculates the position coordinates of the ground contact points Pt1, Pt2 of the pair of left and right front wheels 4a and the ground contact points Pt3, Pt4 of the pair of left and right rear wheels 4b at each node based on the relative position data representing the relative position of each wheel 4 with respect to the center pin 13 and the target bending angle at each node 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 quadrilateral support polygon SP formed by a line segment connecting the ground contact points Pt1 and Pt2 of the vehicle body 16, a line segment connecting the ground contact points Pt2 and Pt4, a line segment connecting the ground contact points Pt4 and Pt3, and a line segment connecting the ground contact points Pt3 and Pt1. The support polygon SP is rectangular when the body 16 is not bent, but becomes a trapezoid when the body 16 is bent, and its shape changes depending on the target bending angle.

The stable area setting unit 34 sets a stable area SA smaller than the support polygon SP inside the support polygon SP calculated by the support polygon calculation unit 33. For example, the stable area setting unit 34 sets as the stable area SA an area surrounded by multiple lines obtained by offsetting each side of the support polygon SP by a predetermined distance inside the support polygon SP.

The stability area SA is set taking into consideration that unevenness of the ground can reduce driving stability. Therefore, it is preferable to set the stability area SA small at work sites where the ground is very uneven, and to set the stability area SA large at work sites where the ground is less uneven.

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 cargo load detection device 50, the target bending angle at each node calculated by the bending angle calculation unit 30, the target lift arm height at each node calculated by the height calculation unit 35 (described later), and the weight data of the wheel loader 1.

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 center of gravity position of the front body 11, the weight and center of gravity position of the rear body 12, the weight and center of gravity position of the empty bucket 3, and the weight and center of gravity position of the lift arm 2. The center of gravity position of each part is specified by the coordinate position of the vehicle body reference coordinate system, which has a predetermined position of the wheel loader 1 as the origin.

The ZMP calculation unit 32 calculates a force vector acting on the center of gravity position G at each node of the travel route R 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 a target vehicle speed calculated by the vehicle speed calculation unit 37 described below. Furthermore, the ZMP calculation unit 32 calculates a ZMP (Zero Moment Point), which is the point where the calculated force vector intersects with the travel surface, at each node of the travel route R.

A specific method for calculating the ZMP at a specified node will be described with reference to Figures 7 and 8. Figure 7 is a schematic diagram of the wheel loader 1 viewed from above, showing the support polygon SP and ZMP. Figure 8 is a schematic diagram of the wheel loader 1 viewed from the side, showing the support polygon SP and ZMP.

As shown in Figures 7 and 8, the ZMP calculation unit 32 calculates the vector of gravity F1 acting on the center of gravity 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 centrifugal force F2 acting on the center of gravity G based on the curvature of the travel route R, the target vehicle speed, and the total weight of the wheel loader 1.

The ZMP calculation unit 32 calculates the time rate of change of the target vehicle speed at each node based on the target vehicle speed at each node. The time rate of change of the target vehicle speed at a specific node can be calculated, for example, based on the target vehicle speed of the specific node, the target vehicle speed of a node adjacent to the specific node, and the distance between the specific node and the node adjacent to that. 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 rate of change of the target vehicle speed.

The ZMP calculation unit 32 calculates the vector of the resultant force F0 of gravity F1, centrifugal force F2, and 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 with the ground (the running surface of the wheel loader 1) as the ZMP.

As described below, the wheel loader 1 has its traveling gear 28 controlled based on the target vehicle speed set for each node of the travel route R. However, a difference may occur between the target vehicle speed and the actual vehicle speed depending on the ground conditions at the work site, such as unevenness of the ground. For this reason, the ZMP calculation unit 32 according to this embodiment performs feedback based on the difference between the actual vehicle speed detected in the past and the target vehicle speed.

The feedback unit 25 shown in Figures 5 and 6 stores 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 driving plan unit 23 at each node while the wheel loader 1 is automatically driving along the driving route R, in association with the position coordinates of the node and the work site. A 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 driving plan controller C1.

The 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.

The ZMP calculation unit 32 calculates the ZMP by taking into account data representing the difference between the actual vehicle speed and the target vehicle speed stored in the non-volatile memory 102 of the driving 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.

As shown in FIG. 6, the driving stability determination unit 36 determines the driving 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 driving 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 area SA set by the stable area setting unit 34. If the ZMP is within the stable area SA, the driving stability determination unit 36 determines that the driving stability is high, i.e., the state of the vehicle body 16 is stable. If the ZMP is not within the stable area SA, the driving stability determination unit 36 determines that the driving stability is low, i.e., the state of the vehicle body 16 is unstable.

The vehicle speed calculation unit 37 calculates the target vehicle speed based on the results of the driving stability judgment at each position on the driving route R. The height calculation unit 35 calculates the target lift arm height based on the results of the driving stability judgment at each position on the driving route R. The calculation method for the target vehicle speed and the target lift arm height is explained in detail below. The calculated target vehicle speed and target lift arm height may be modified depending on the results of the driving stability judgment. In other words, the target vehicle speed and target lift arm height, which are the calculation results before the driving stability judgment process is performed, can be said to be provisional target values.

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, for example, based on the maximum vehicle speed when a wheel loader driven by an operator travels along the travel route R during loader work. In a wheel loader, the speed gear is usually set to second gear when heading toward a loading position. The maximum vehicle speed when the speed gear is set to second gear is approximately 12 km/h. For this reason, the initial vehicle speed value of the target vehicle speed at each node except the final node on the travel route R3 is set to 12 km/h, which is the maximum vehicle speed. In this embodiment, the target vehicle speed at the final node is set to 0 (zero).

When the driving stability determination unit 36 determines that the state of the vehicle body 16 is stable, the vehicle speed calculation unit 37 determines the provisional target vehicle speed used in the determination as the target vehicle speed for the operation command. When the driving 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 in the determination as the new target vehicle speed. Each time the driving 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 a predetermined value lower than the current target vehicle speed. The vehicle speed calculation unit 37 repeatedly corrects the target vehicle speed to a lower value until the state of the vehicle body 16 is determined to be stable. In other words, when the driving stability is low, the vehicle speed calculation unit 37 corrects the target vehicle speed to a lower value.

The vehicle speed calculation unit 37 stores in the non-volatile memory 102 driving plan information that associates multiple nodes on the driving route R with the target vehicle speeds at the multiple nodes.

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 vehicle testing, and the travel route R generated by the route generation unit 22.

The height initial value table is a data table in which each position on the reference travel path is associated with the lift arm height. For example, when the wheel loader 1 heads for a loading position, an operation of raising the lift arm while traveling (rise run) is performed so that loading work can be started immediately after arriving at the loading position. For this reason, the height initial value table used to calculate the lift arm height on the travel path R3 is composed of data in which the lift arm height gradually increases from the travel start position to the travel end position on the reference travel path, and the lift arm height becomes the loading height at the travel end position. As will be described later, the target lift arm height is corrected to a lower value when the state of the vehicle body 16 is determined to be unstable. 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. Note that instead of the height initial value table, the initial value of the target lift arm height at each position on the travel path 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.

Similarly, the initial height values of the target lift arm heights at each position of the other travel routes R1, R2, and R4 are set based on the corresponding initial height value tables or initial values (fixed values). For example, the initial height 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 center axis of the wheels 4, as shown in FIG. 1.

If the path length of the reference driving path in the height initial value table differs from the path length of the driving path R generated by the path generation unit 22, the initial height value of the target lift arm height at each position of the driving path R is set taking into account the ratio between the path length of the reference driving path and the path length of the driving path R.

When the driving 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 provisional target lift arm height used in the determination as the target lift arm height for the operation command. When the driving stability determination unit 36 determines that the state of the vehicle body 16 is unstable, the height calculation unit 35 determines a value obtained by subtracting a predetermined value from the target lift arm height used in the determination as the new target lift arm height. Each time the driving 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 corrects the target lift arm height to be lower until the state of the vehicle body 16 is determined to be stable. In other words, when the driving stability is low, the height calculation unit 35 corrects the target lift arm height in a lowering direction.

The height calculation unit 35 stores in the non-volatile memory 102 driving plan information that associates multiple nodes on the driving route R with the target lift arm heights at the multiple nodes.

When the target vehicle speed and 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. This updates the center of gravity position G. 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. This updates the ZMP. When the ZMP is updated, the driving stability determination unit 36 determines the driving stability based on the positional relationship between the updated ZMP and the stable area SA.

As described above, the stable driving planning unit 23 stores in the non-volatile memory 102 driving plan information that associates multiple positions on the generated driving route R with the target bending angle, target lift arm height, and target vehicle speed at the multiple positions. The driving plan information is stored in the non-volatile memory 102, for example, as a data table. When the stable driving planning unit 23 determines that the state of the vehicle body 16 is unstable, it corrects the target vehicle speed and target lift arm height used in the judgment, recalculates the center of gravity position G and ZMP based on the correction result, and judges the driving stability again. When the stable driving planning unit 23 determines that the state of the vehicle body 16 is stable, it does not correct the target vehicle speed and target lift arm height used in the judgment. As a result, the tentative target vehicle speed and tentative target lift arm height used in the judgment of the driving stability are determined as the target vehicle speed and target lift arm height for the operation command.

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

When the stable driving plan unit 23 decides to modify the driving route R, the turning-back position setting unit 21 shown in FIG. 5 sets a position farther from the target excavation position P1 and the target loading position P2 than the current turning-back position P0 as a new turning-back position P0. When the turning-back position setting unit 21 sets the new turning-back position P0, the route generating unit 22 generates a new driving route R. When the driving route R is updated, the stable driving plan unit 23 again calculates the target bending angle, the target vehicle speed, and the target lift arm height based on the updated driving route R.

The operation command unit 24 calculates steering control commands, driving control commands (accelerator commands and brake commands), and arm control commands as operation commands based on the driving plan information stored in the non-volatile memory 102, and outputs the calculation results to the vehicle control controller C4. The vehicle control controller C4 controls the steering device 19, the driving device 28, and the lift arm 2 based on the steering control commands, driving control commands, and arm control commands output from the operation command unit 24.

Here, the relationship between the deceleration (vehicle speed reduction rate), lift arm height, and bending angle of the vehicle body 16 and the running stability will be described with reference to FIG. 9. The bending angle can also be replaced with the curvature of the running path R. The deceleration (vehicle speed reduction rate) corresponds to the absolute value of the time rate of change of the vehicle speed when the time rate of change of the vehicle speed is negative. As shown in FIG. 9, when the stable region and the unstable region are divided by the deceleration, lift arm height, and bending angle, the boundary between the stable region and the unstable region is shown as shown. The region to the upper right of the illustrated boundary is the unstable region with low running stability, and the region to the lower left of the boundary is the stable region with high running stability. As shown in the figure, the wheel loader 1 has a larger unstable region as the deceleration increases, the lift arm height increases, and the bending angle increases (the curvature of the running path R increases).

An example of the flow of the stable driving plan processing executed by the stable driving planner 23 according to the embodiment of the present invention will be described with reference to the flowchart of FIG. 10. The processing shown in the flowchart of FIG. 10 is executed for each of the following: driving route R1 with the turning position P0 as the driving start position and the target excavation position P1 as the driving end position; driving route R2 with the target excavation position P1 as the driving start position and the turning position P0 as the driving end position; driving route R3 with the turning position P0 as the driving start position and the target loading position P2 as the driving end position; and driving route R4 with the target loading position P2 as the driving start position and the turning position P0 as the driving end position.

The process shown in the flowchart of FIG. 10 is started when the execution conditions for the stable driving plan process are met, and is executed repeatedly at a predetermined control period. The execution conditions for the stable driving plan process include the automatic driving mode being set by the control device 100. When an automatic driving start command is input to the control device 100 by the operator operating the input devices 38 and 72, the control device 100 sets the automatic driving mode.

The execution conditions for the stable driving plan processing are set for each of the driving routes R1 to R4. For example, the execution conditions for the stable driving plan processing for the driving route R3 are met when the automatic driving mode is set, the wheel loader 1 is automatically traveling along the driving route R2, and the wheel loader 1 reaches the target turning position P0.

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 on the driving route R is N. In step S2, the center of gravity calculation unit 31 acquires the load in the bucket calculated by the load calculation controller C3, and proceeds to step S3.

In step S3, the stable driving planning 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 that represents the node number. 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 node number n setting process in step S3 is completed, the process proceeds to step S4.

In step S4, the stable driving planning 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 planning unit 23 calculates the target bending angle at the node set as the calculation target in step S4, and proceeds to step S6.

In step S6, the support polygon calculation unit 33 calculates the support polygon SP based on the target bending angle calculated in step S6. In step S6, the stable area setting unit 34 sets the stable area SA based on the support polygon SP calculated by the support polygon calculation unit 33. When the area calculation process in step S6 is completed, the process proceeds to step S7.

In step S7, the stable driving plan unit 23 determines whether the node number n of the node currently set as the calculation target matches N. If it is determined in step S7 that the node number n of the node currently set as the calculation target matches the node number N, i.e., the node to be calculated is the node at the end position of the driving (final node), the process proceeds to step S8. If it is determined in step S7 that the node number n of the node currently set as the calculation target does not match the node number N, i.e., the node to be calculated is not the node at the end position of the driving (final node), the process proceeds to step S9.

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 a target height of a predetermined travel end position. When the processing of step S8 ends, the processing returns to step S4. Here, the target height of the travel end position corresponds to the loading height of the dump truck 92 when the travel route R3 toward the loading position is the subject of the calculation, and corresponds to the height in the normal travel posture when the other travel routes R1, R2, and R4 are the subject of the calculation.

In other words, the process of step S8 is performed so that the vehicle body 16 stops at the final node and the lift arm height reaches the target height for the travel end position. For example, when the travel route R3 for transporting excavated material to the dump truck 92 is the subject of calculation, the process of step S8 is performed for the purpose of enabling the wheel loader 1 to reach the final node with the lift arm 2 raised to the loading height.

In step S9, the stable driving 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 that represents the number of times the calculation of the target vehicle speed and the target lift arm height for one node is repeated. In step S10, the driving stability determination unit 36 adds 1 to the number of calculations m and proceeds to step S11.

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. If the number of calculations m is 1, the vehicle speed calculation unit 37 sets the target vehicle speed to the initial vehicle speed value, and the height calculation unit 35 sets the target lift arm height to the initial height value. If 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 a 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 a new target lift arm height. When the processing of step S11 ends, the processing proceeds to step S12.

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.

In step S13, the ZMP calculation unit 32 calculates the ZMP based on the target bending 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 area SA. In step S14, if the running stability determination unit 36 determines that the ZMP is within the stable area 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, if the running stability determination unit 36 determines that the ZMP is not within the stable area SA, it sets a flag indicating that the state of the vehicle body 16 at the node is unstable, and proceeds to step S15.

In step S15, the stable driving plan unit 23 determines whether the number of calculations m matches the maximum number of calculations M. If it is determined in step S15 that the number of calculations m does not match the maximum number of calculations M, the process returns to step S10. If it is determined in step S15 that the number of calculations m matches the maximum number of calculations M, the process proceeds to step S16. That is, if it is determined in step S15 that the number of calculations m of the target vehicle speed and target height at the nth node has reached the maximum number of calculations M, the process proceeds to step S16.

In step S16, the stable driving plan unit 23 determines the correction (recalculation) of the driving route R, and ends the processing shown in the flowchart of FIG. 10. When the correction (recalculation) of the driving route R is determined in step S16, the turning position setting unit 21 moves the turning position P0 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 turning position P0. Furthermore, the route generation unit 22 recalculates the driving route R based on the target excavation position P1 and the target loading position P2, and the new turning position P0 calculated by the turning position setting unit 21.

In step S17, the driving stability determination unit 36 determines whether the node number n is equal to 1. In this embodiment, the target bending angle, target vehicle speed, and target lift arm height are calculated sequentially from node number n=N to node number n=1. In other words, the processing of step S17 corresponds to the processing of determining whether the calculation of the target bending angle, target vehicle speed, and target lift arm height for all nodes on the driving route R has been completed.

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, target vehicle speed, and 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 processing, the process of calculating the target bending angle, target height, and target lift arm height for that node is executed.

In step S17, when it is determined that the node number n is equal to 1, that is, when it is determined that the calculation of the target bending angle, target vehicle speed, and target lift arm height for all nodes on the travel route R is completed, the process shown in the flowchart of FIG. 10 is terminated.

If it is determined in the processing of step S17 that the node number n is equal to 1, the operation command unit 24 generates an operation command based on the driving plan information composed of the target bending angle, target vehicle speed, and target lift arm height at each node on the driving route R calculated in the stable driving plan processing shown in FIG. 10, and outputs it to the vehicle control controller C4. This starts the automatic driving of the wheel loader 1. In other words, the judgment processing of step S17 corresponds to a process of determining whether or not the condition for starting the automatic driving of the wheel loader 1 (hereinafter also referred to as the driving start condition) has been met.

An example of the calculation contents of the control device 100 according to this embodiment can be summarized as follows. As shown in FIG. 3, the wheel loader 1 repeatedly performs loading work. When the vehicle is at the turning 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, and the target turning position P0 and the target azimuth angle A0 at that position for the next loading work based on the image data captured by the imaging device 15, and generates travel routes R1 to R4 based on this setting information.

The control device 100 calculates driving plan information including the target vehicle speed, target lift arm height, and target bending angle at each node where driving stability can be ensured on the driving route R1, and generates an operation command based on the calculated driving plan information. The control device 100 controls each part based on the generated operation command to drive the vehicle along the driving route R1. When the vehicle reaches the target excavation position P1, the excavation work is performed automatically. When the excavation work is completed, the control device 100 calculates driving plan information including the target vehicle speed, target lift arm height, and target bending angle at each node where driving stability can be ensured on the driving route R2, and generates an operation command based on the calculated driving plan information. The control device 100 controls each part based on the generated operation command to drive the vehicle along the driving route R2. When the vehicle reaches the target turning position P0, the control device 100 calculates driving plan information including the target vehicle speed, target lift arm height, and target bending angle at each node where driving stability can be ensured on the driving route R3, and generates an operation command based on the calculated driving plan information. The control device 100 controls each part based on the generated operation command, and drives the vehicle along the driving route R3. When the vehicle reaches the target loading position P2, the loading operation is performed automatically. When the loading operation is completed, the control device 100 calculates driving plan information including the target vehicle speed, target lift arm height, and target bending angle at each node where driving is possible while ensuring driving stability on the driving route R4, and generates an operation command based on the calculated driving plan information.

The control device 100 calculates the load in the bucket prior to the calculation of 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 target vehicle speed and target lift arm height at the final node of each travel route R (steps S5 and S8).

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

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 modified (No in step S14, No in 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 modified target vehicle speed, and the target lift arm height (steps S12, S13, S14).

If the state of the vehicle body 16 at the node being calculated is determined to be stable (Yes in step S14), the target vehicle speed and target lift arm height used in that determination become the target values used in calculating the operation command. The control device 100 then performs the same process with the next node being calculated.

In other words, the control device 100 repeatedly performs the processes of steps S5 to S7, S9 to S14, and S17. This calculates the target bending angle, target vehicle speed, and target lift arm height at each node in order from the node at the end position of the travel (final node) to the node at the start position of the travel.

If the state of the vehicle body 16 does not become stable even after repeating the series of calculation processes of calculating the target vehicle speed and the target lift arm height and determining the driving stability up to the maximum number of calculations M, the control device 100 decides to correct (recalculate) the driving route R (Yes in step S15, S16).

As described above, in this 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 modifies the target bending angle, the target vehicle speed, and the target lift arm height when the running stability is low (unstable). For example, in the running route R3, the vehicle body 16 decelerates in the deceleration area DA before the target loading position (running end position) with the lift arm height high, so the running stability is likely to be low. In this embodiment, the control device 100 first determines the target vehicle speed and the target lift arm height at the running end position (target loading position), and then calculates the target vehicle speed and the target lift arm height that can maintain running stability on the running route from the running end position to the running start position. Therefore, according to this embodiment, the calculation time (calculation load) can be reduced compared to the case where the calculation is performed in order from the node of the running start position (target turning position) to the node of the running end position (target loading position).

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

The above-described embodiment provides the following advantages:

(1) The wheel loader 1 comprises 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 attached to the front body 11, a bucket 3 rotatably attached to the lift arm 2, a traveling device 28 that drives the vehicle body 16, a steering device 19 that bends the vehicle body 16 to change the bending angle and steer the vehicle, and a control device 100 that generates a traveling route R based on an excavation position and a loading position at a 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 R.

The control device 100 calculates the target bending angle, the target lift arm height, and the target vehicle speed on the driving path R1 based on the generated driving path 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 driving 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.

With this configuration, it is possible to appropriately determine whether stable automatic driving is possible on the travel route R. In this embodiment, the wheel loader 1 does not start traveling until the travel stability is determined to be stable at all nodes on the travel route R. This prevents the wheel loader 1 from becoming unstable during automatic operation. In other words, according to this embodiment, the wheel loader 1 can be made to travel stably and automatically along the generated travel route R1.

(2) The control device 100 stores in the storage device (non-volatile memory 102) driving plan information (data table) that associates multiple positions (nodes) on the generated driving route R with the target bending angle, target lift arm height, and target vehicle speed at the multiple positions. If the control device 100 determines that the state of the vehicle body 16 is unstable, it corrects the target vehicle speed and the target lift arm height. If the control device 100 determines that the state of the vehicle body 16 is stable, it 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 driving plan information (data table) stored in the storage device (non-volatile memory 102).

In this configuration, the target vehicle speed and target lift arm height for which the state of the vehicle body 16 is determined to be unstable are modified by the travel stability determination process. If the state of the vehicle body 16 is determined to be stable as a result of modifying the target vehicle speed and target lift arm height, the target vehicle speed and target lift arm height used in the determination are stored and held as target values for operation commands in association with positions on the travel route R. In other words, in this configuration, the target vehicle speed and target lift arm height are modified at multiple positions on the travel route R until the state of the vehicle body 16 is determined to be stable. As a result, the wheel loader 1 can be automatically driven stably along the travel route R.

(3) The wheel loader 1 is equipped with a load detection device 50 that detects the load of the load (load in the bucket) loaded on 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 of the load (load in the bucket) detected by the load 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 (resultant force of gravity F1, centrifugal force F2, and inertia 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 with the traveling surface. The control device 100 judges the traveling stability of the vehicle body 16 based on the positional relationship between the calculated support polygon SP and the calculated ZMP.

In this configuration, the center of gravity position G of the wheel loader 1 at each position on the travel route R can be calculated with high accuracy based on the load in the bucket detected before the start of automatic travel. Therefore, the travel stability of the vehicle body 16 at each position on the travel route R can be more appropriately determined. This makes it possible to ensure high travel stability during automatic travel.

(4) The control device 100 sets a stable area SA inside the calculated support polygon SP, the stable area SA being smaller than the calculated support polygon SP. If the calculated ZMP is within the set stable area SA, the control device 100 determines that the state of the vehicle body 16 is stable. If the calculated ZMP is not within the set stable area SA, the control device 100 determines that the state of the vehicle body 16 is unstable.

This configuration makes it possible to appropriately determine the driving stability of the vehicle body 16 at each position on the driving route R at a work site where the ground is uneven. This makes it possible to ensure high driving stability during automatic driving, even if the driving surface (ground) at the work site is uneven.

(5) The wheel loader 1 is equipped 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 associates a position on the generated travel route R with the actual vehicle speed detected by the vehicle speed sensor 45 at that position and data representing the difference between the calculated target vehicle speed, and stores them in the storage device (non-volatile memory 102). 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.

In this configuration, the ZMP is calculated taking into account data that indicates the difference between the target vehicle speed and the actual vehicle speed, so driving stability can be determined with high accuracy. As a result, even if there is a difference between the target vehicle speed and the actual vehicle speed due to the ground conditions at the work site, individual differences in the wheel loader 1, etc., the driving stability of the vehicle body 16 at each position on the travel route R can be appropriately determined. This makes it possible to ensure high driving stability during automatic driving.

(6) The wheel loader 1 is equipped 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 results 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 loading work travel route R3 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.

In this configuration, the loader work is repeatedly performed by automatic driving, so even if the conditions around the vehicle body 16 change, such as the shape of the ground 91 changing or the dump truck 92 being replaced, the target excavation position P1, the target loading position P2, and each of the travel routes R1 to R4 are appropriately set. This makes it possible to improve the work efficiency of the wheel loader 1.

(7) When the control device 100 determines that the state of the vehicle body 16 is unstable, it corrects the target vehicle speed and the target lift arm height to be lower. This makes it possible to 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.

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

In this configuration, the control device 100 determines that high driving stability cannot be ensured by simply correcting the target vehicle speed and the target lift arm height, and corrects (recalculates) the driving route R. As a result, even if it is determined that high driving stability cannot be ensured on the driving route R that was the subject of the calculation, the control device 100 can again appropriately determine whether stable automatic driving is possible on the corrected driving route R.

The present invention is not limited to the above-mentioned examples, but includes various modified examples. For example, the above-mentioned examples have been described in detail to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all of the configurations described. The following modified examples are also within the scope of the present invention, and it is possible to combine the configurations shown in the modified examples with the configurations described in the above-mentioned embodiments, or to combine the configurations described in the different modified examples below.

<Modification 1>
In the above embodiment, an example was described in which the area surrounded by a plurality of lines in which each side constituting the support polygon SP is offset by a predetermined distance inside the support polygon SP in each of the travel routes R1 to R4 is set as the stable area SA, but the present invention is not limited to this. In the loader operation, the vehicle is decelerated 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, so that the vehicle is likely to become unstable. In particular, the lift-up operation is performed before the loading position in the travel route R3, so that the vehicle is likely to become unstable. For this reason, the stable area SA used to determine the running stability in the travel route R3 may be set smaller than the stable area SA used to determine the running stability in the travel routes R1, R2, and R4. This allows the vehicle to run with higher stability when the operation of raising the lift arm while running by automatic driving (rise run) is performed.

Furthermore, even if the driving route is the same, the size of the stability area SA may be changed depending on the position. For example, on driving route R3, deceleration is performed when the lift arm height is at a high position just before the loading position.

For this reason, the control device 100 may set the stable area SA smaller on the travel route R3 for loading operation as the loader approaches the set target loading position P2. For example, the control device 100 sets the size of the stable area SA in the deceleration area DA of the travel route R3 shown in FIG. 3 to be smaller than the size of the stable area SA outside the deceleration area DA of the travel route R3.

This configuration allows the vehicle to travel with greater stability just before the loading position on travel route R3.

<Modification 2>
In the above embodiment, an example has been described in which the stable area SA is set inside the support polygon SP, but the present invention is not limited to this. The control device 100 may determine that the state of the vehicle body 16 is stable when the ZMP is within the support polygon SP without setting the stable area SA, and may determine that the state of the vehicle body 16 is unstable when the ZMP is not within the support polygon SP.

<Modification 3>
In the above embodiment, an example has been described in which the control device 100, when it is determined that the state of the vehicle body 16 is unstable, corrects both the target vehicle speed and the target lift arm height used in the determination to be lower, but 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 correct only one of the target vehicle speed and the target lift arm height used in the determination to be lower.

When the control device 100 determines that the state of the vehicle body 16 is unstable, it makes corrections to lower at least one of the target vehicle speed and the target lift arm height, thereby making it possible to appropriately calculate the target vehicle speed and target lift arm height at which the state of the vehicle body 16 is determined to be stable.

<Modification 4>
The control device 100 may be configured to have a lift arm priority mode, a vehicle speed priority mode, and a normal mode, and to set one of the lift arm priority mode, the vehicle speed priority mode, and the normal mode in response to an operation by an operator. The control device 100 sets the calculation mode in response to a mode selection signal from an input device 38 serving as a mode selection operation unit provided in the cab 5. The control device 100 also sets the calculation mode in response to a mode selection signal obtained via the communication device 46 from an input device 72 serving as a mode selection operation unit provided in the remote control device 70.

The lift arm priority mode is a calculation mode in which the target vehicle speed is corrected but the target lift arm height is not corrected when the state of the vehicle body 16 is determined to be unstable. The vehicle speed priority mode is a calculation mode in which the target lift arm height is corrected but the target vehicle speed is not corrected when the state of the vehicle body 16 is determined to be unstable. The normal mode is a calculation mode in which both the target vehicle speed and the target lift arm height are corrected when the state of the vehicle body 16 is determined to be unstable. The operator can select one calculation mode from the lift arm priority mode, the vehicle speed priority mode, and the normal mode by operating the mode selection operation unit (input device 38, 72). In other words, the operator can freely select the method of correcting the target value when the state of the vehicle body 16 is determined to be unstable.

<Modification 5>
In the above embodiment, an example has been described in which the wheel loader 1 is provided with the object detection device 56 that detects objects such as the natural ground 91 and the dump truck 92 based on the data of the image captured by the imaging device 15, but the present invention is not limited to this. The object detection device 56 may be a device that detects objects based on the detection results of an ultrasonic sensor, a millimeter wave sensor, a laser radar sensor, an infrared sensor, etc.

<Modification 6>
In the above embodiment, an example is described in which the load in the bucket calculated by the load detection device 50 is acquired when determining the running stability on each of the travel routes R1 to R4 (see step S2 in FIG. 10), but the present invention is not limited to this. 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 to determine the running stability on the travel routes R1 and R4 are 0 (zero), and the predetermined loads W2 and W3 used to determine the running stability on the travel routes R2 and R3 are values greater than 0 (zero). The predetermined loads W2 and W3 can be determined, for example, by releasing the soil loaded in the bucket 3 during the loader operation into a load measuring device provided outside the wheel loader 1 in an actual machine test and measuring the load.

<Modification 7>
In the above embodiment, an example has been described in which the control device 100 sets 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, but 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 coordinates input from the input device 38 in response to an operation by 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 coordinates transmitted from the remote operation device 70.

<Modification 8>
The control device 100 may display the traveling stability determination result on the display device 39 in the driver's cab 5. The control device 100 may also transmit the traveling stability determination result to the remote operation device 70 via the communication device 46. The remote operation controller C5 of the remote operation device 70 displays the traveling stability determination result on the display device 73. With this configuration, by looking at the images displayed on the display devices 39, 73, the operator can determine whether or not to automatically operate the wheel loader 1 in the current situation around the vehicle body 16.

<Modification 9>
The configuration of the wheel loader 1 is not limited to the example described in the above embodiment. The wheel loader 1 may be configured to include, for example, a generator motor mechanically connected to the engine 40, and a traveling motor that is rotated and driven by the electric power generated by the generator motor to operate the traveling device. In other words, 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. The wheel loader may also be provided with an HST (Hydro Static Transmission) type power transmission mechanism that converts the power of the engine 40 into hydraulic power and transmits it to the wheels 4.

Although the embodiments of the present invention have been described above, the above embodiments merely show some of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

1...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...photographing device, 16...vehicle body, 17...working device, 18...brake device, 19...steering device, 21...turning position setting unit, 22...path generating unit, 23... Stable driving planning unit, 24...operation command unit, 25...feedback unit, 28...driving device, 30...bending angle calculation unit, 31...center of gravity calculation unit, 32...ZMP calculation unit, 33...support polygon calculation unit, 34...stable area setting unit, 35...height calculation unit, 36...driving 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, 4 7...position detection device, 50...load detection device, 56...object detection device, 60A, 60B, 60C...hydraulic pump, 61...front control unit, 62...brake control unit, 63...steering control unit, 64...transmission control unit, 65...engine control unit, 70...remote control device, 71...communication device, 72...input device, 73...display device, 91...natural ground (object to be excavated), 92...dump truck (transport vehicle), 100...control device, 101...processing device, 102...non-volatile memory ( storage device), C...controller, C1...travel plan controller, C2...position setting controller, C3...load calculation controller, C4...vehicle control controller, C5...remote control controller, DA...deceleration area, F0...force acting on center of gravity G (resultant force of gravity F1, centrifugal force F2, and inertial force F3), P0...target turning position, P1...target digging position, P2...target loading position, Pt1, Pt2, Pt3, Pt4...grounding point, R...travel route, SA...stable area, SP...support polygon

Claims (8)

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 that causes the vehicle body to travel;
A steering device that changes a bending angle by bending the vehicle body to steer the vehicle;
a control device that generates a travel path based on an excavation position and a loading position at a work site, and controls the travel device, the lift arm, and the steering device so that the vehicle body travels along the travel path while raising the lift arm from a predetermined travel start position on the travel path toward the loading position so that the height of the lift arm becomes a loading height at the loading position,
The control device includes:
Calculating target bending angles at a plurality of positions on the travel path based on the generated travel path;
setting target vehicle speeds at a plurality of positions on the travel route to predetermined initial vehicle speed values;
Setting target lift arm heights at a plurality of positions on the travel path to a predetermined initial height value;
Calculating a center of gravity position of the wheel loader based on the target bending angle and the target lift arm height;
determining a traveling stability of the vehicle body at each of a plurality of positions on the traveling 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, the target vehicle speed and the target lift arm height are repeatedly corrected to be lowered until it is determined that the state of the vehicle body is stable.
storing, in a storage device, travel plan information that associates 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;
The steering device, the lift arm, and the traveling device are controlled based on the travel plan information stored in the storage device.
A wheel loader characterized by the above. The wheel loader according to claim 1,
a load detection device for detecting the load of a load loaded on the bucket;
The control device includes:
Calculating a support polygon based on the calculated target bending angle;
Calculating the center of gravity position based on the load of the cargo detected by the cargo load detection device , the target lift arm height , and the target bending angle;
calculating a vector of a force acting on the center of gravity position based on the center of gravity position and the target vehicle speed;
Calculating a ZMP, which is a point where the calculated force vector intersects with a traveling surface;
determining a traveling stability of the vehicle body based on a positional relationship between the calculated support polygon and the calculated ZMP. The wheel loader according to claim 2,
The control device includes:
A stable region smaller than the calculated support polygon is set inside the calculated support polygon;
when the calculated ZMP is within the set stable region, the state of the vehicle body is determined to be stable, and when the calculated ZMP is not within the set stable region, the state of the vehicle body is determined to be unstable. The wheel loader according to claim 3,
a vehicle speed sensor for detecting an actual vehicle speed of the wheel loader traveling along the generated travel route;
The control device includes:
storing in the storage device a position on the travel route that has been generated and data that indicates a difference between an actual vehicle speed detected by the vehicle speed sensor at that position and the target vehicle speed in association with each other ;
the ZMP is calculated taking into consideration data stored in the storage device that indicates a difference between the actual vehicle speed and the target vehicle speed. The wheel loader according to claim 3,
an object detection device for detecting objects around the vehicle body,
The control device includes:
Based on the detection result of the object detection device, a target excavation position and a target loading position are set at the work site;
A target turning back position is set based on the set target excavation position and the set target loading position,
a travel route for excavation work from the set target turning position to the set target excavation position, a travel route for a first return from the set target excavation position to the set target turning position, a travel route for loading work from the set target turning position to the set target loading position, and a travel route for a second return from the set target loading position to the set target turning position. The wheel loader according to claim 5,
The control device includes:
a stability area set to be smaller the closer to the set target loading position on the travel path for loading operation. 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 when it is determined that the state of the vehicle body is not stable, corrects the travel route. 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 modified but the target lift arm height is not modified; 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 modified but the target vehicle speed is not modified; 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 modified; and the control device is configured so that one mode is set from the lift arm priority mode, the vehicle speed priority mode, and the normal mode in response to operation by an operator.