Control device for work vehicles

Abstract

In the automated driving of work vehicles, the vehicle's posture upon reaching the target position is made to follow the target posture. [Solution] A control device for a work vehicle that drives the work vehicle along a target path, comprising: a target path planning unit that plans the target path based on the position of the work vehicle and the target position; and an action generation unit that calculates the amount of steering of the steering mechanism of the work vehicle and controls the driving of the work vehicle so that the work vehicle drives along the target path based on the position of the work vehicle and the target path, wherein the action generation unit limits the amount of steering based on the remaining distance to travel along the target path from the position of the work vehicle to the target position.

Description

[Technical Field]

[0001] This invention relates to a control device for work vehicles. [Background technology]

[0002] In autonomous driving of mobile vehicles, the forward-looking model described in Patent Document 1 is commonly used as a steering model for following a target path. The forward-looking model identifies a predetermined distance away on the target path as the target position (forward gaze point) and sequentially executes steering control to pass through that target position. Because the forward-looking model has a relatively simple control system compared to other error correction models, it is widely used as an autonomous driving technology for mobile vehicles, including automobiles and robots. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Patent No. 4599835 [Overview of the project] [Problems that the invention aims to solve]

[0004] Incidentally, at construction sites, mining sites, and other similar locations, there is a growing demand to automate various types of work vehicles from the perspective of controlling labor costs and reducing the burden on operators. However, when the above-mentioned automated driving technology is applied to work vehicles equipped with an articulated steering mechanism in which the vehicle body itself bends, such as wheel loaders, the bending angle of the vehicle body may become large near the target position, which is the end point of the target path. As a result, the posture of the vehicle body when it reaches the target position may deviate from the target posture, which may hinder the work. The present invention has been made in view of the above-mentioned problems of the prior art, and its purpose is to provide a control device for work vehicles that can make the posture of the vehicle body when it reaches the target position follow the target posture during the automated driving of work vehicles. [Means for solving the problem]

[0005] The present invention provides a control device for a work vehicle to solve the above problems, which is a control device for a work vehicle to drive a work vehicle following a target path, comprising: a target path planning unit that plans a target path based on the position of the work vehicle and a target position; and an action generation unit that calculates the amount of steering of the steering mechanism of the work vehicle and controls the driving of the work vehicle so that the work vehicle follows the target path based on the position of the work vehicle and the target path, wherein the action generation unit limits the amount of steering based on the remaining distance to travel along the target path from the position of the work vehicle to the target position. [Effects of the Invention]

[0006] In the automated driving of work vehicles, the vehicle's posture upon reaching the target position can be made to follow the target posture. Further features related to the present invention will become apparent from the description herein and the accompanying drawings. Furthermore, problems, configurations, and effects other than those described above will be revealed by the following description of embodiments. [Brief explanation of the drawing]

[0007] [Figure 1] External view of the work vehicle according to the embodiment. [Figure 2] A diagram showing the control system of an embodiment. [Figure 3] Figure 2 shows a functional block diagram of the control device. [Figure 4] Figure 3 shows a functional block diagram of the motion generation unit. [Figure 5] A schematic diagram of a work vehicle using a forward-looking model. [Figure 6] A schematic diagram illustrating a method for calculating path-following error. [Figure 7] Correlation diagram between path-following error, remaining distance traveled, and steering limiting gain. [Figure 8] A flowchart illustrating the operation of the steering limiting gain calculation unit in the embodiment. [Figure 9] A schematic diagram showing the path-following error for the path shown in Figure 5. [Modes for carrying out the invention]

[0008] In the following description, a wheel loader will be used as an example of a work vehicle according to the embodiment, with reference to the drawings. In each figure, equivalent components will be denoted by the same reference numeral, and redundant explanations will be omitted as appropriate.

[0009] The embodiments will be described below with reference to Figures 1 to 8. Figure 1 is an external view of the work vehicle 1 of the embodiment, and Figure 2 is a diagram showing the control system of the embodiment. As shown in Figure 1, the work vehicle 1 of this embodiment is a wheel loader equipped with an articulated steering mechanism.

[0010] The work vehicle 1 comprises a front section 6 and a rear section 7. The work vehicle 1 is equipped with a work tool 5 and a lift arm 2 that rotatably supports the work tool 5 on the front of the front section 6. In this embodiment, the work tool is a bucket for excavating soil and sand. The lift arm 2 is rotatably supported by the work vehicle 1, and the work tool 5 moves up and down as the lift arm 2 rotates. The lift arm 2 also rotatably supports a bell crank 3. When the bell crank 3 rotates, the work tool 5 also rotates relative to the lift arm 2 via a bucket link 4.

[0011] A lift cylinder 12 is connected between the front of the vehicle body 6 and the lift arm 2. The angle of the lift arm 2 relative to the front of the vehicle body changes as the lift cylinder 12 expands and contracts due to the supply and discharge of hydraulic fluid. A bucket cylinder 13 is connected between the front of the vehicle body 6 and the bell crank 3. The angle of the work tool 5 relative to the lift arm 2 changes as the bucket cylinder 13 expands and contracts due to the supply and discharge of hydraulic fluid.

[0012] Furthermore, the work vehicle 1 is equipped with a front right tire 21FR, a front left tire 21FL, a rear right tire 21RR, and a rear left tire 21RL. The work vehicle 1 moves by driving the front right tire 21FR, the front left tire 21FL, the rear right tire 21RR, and the rear left tire 21RL.

[0013] The work vehicle 1 comprises a front section 6, a rear section 7, a center joint 23, and the work tool 5 described above. The center joint 23 connects the front section 6 and the rear section 7 so that they can rotate around a vertical axis. The work tool 5 is mounted on the front of the front section 6. The work vehicle 1 changes its direction of travel (steers) by changing the angle (bending angle) between the front section 6 and the rear section 7 around the center joint 23. In other words, the work vehicle 1 of this embodiment is equipped with an articulated steering mechanism. A steering cylinder 11 is connected between the rear of the front section 6 and the front of the rear section 7. The angle between the front section 6 and the rear section 7 changes as the steering cylinder 11 expands and contracts due to the supply and discharge of hydraulic fluid.

[0014] As shown in Figure 2, the control system 1000 is equipped with an engine 10 as a power source. As shown in Figure 2, the engine 10 drives the hydraulic pump 14 and the power transmission device 22. The power transmission device 22 is a transmission such as an HST (Hydro Static Transmission) and transmits the power of the engine 10 to the front right tire 21FR and the front left tire 21FL via the center joint 23 and the front differential 24F. The power transmission device 22 also transmits the power of the engine 10 to the rear right tire 21RR and the rear left tire 21RL via the center joint 23 and the rear differential 24R. The front right tire 21FR, front left tire 21FL, rear right tire 21RR, and rear left tire 21RL, which receive the power of the engine 10, accelerate and drive the work vehicle 1.

[0015] Meanwhile, the hydraulic pump 14 is driven by the engine 10 to supply hydraulic fluid to the control valve 15. The control valve 15 controls the supply and discharge of hydraulic fluid to the steering cylinder 11, lift cylinder 12, bucket cylinder 13, brakes 14F and 14R. As the steering cylinder 11, lift cylinder 12, and bucket cylinder 13 extend and retract due to the supply and discharge of hydraulic fluid, the angles formed by the front 6 and rear 7 of the vehicle body, the angle of the lift arm 2 relative to the front 6 of the vehicle body, and the angle of the work tool 5 relative to the lift arm 2 change, respectively. In addition, as the brakes 14F and 14R are activated by the supply of hydraulic fluid, the rotation of the front right tire 21FR, front left tire 21FL, rear right tire 21RR, and rear left tire 21RL is suppressed, causing the work vehicle 1 to decelerate and stop.

[0016] The control system also includes a control device 100, an engine control device 500, a hydraulic control device 600, and a transmission control device 700. The control device 100 controls the automatic operation of the work vehicle 1, including automatic driving and automatic work. The control device 100 generates engine control signals, hydraulic control signals, and transmission control signals. The control device 100 transmits the generated engine control signal to the engine control device 500. In accordance with the engine control signal, the engine control device 500 controls the rotational speed of the engine 10. The control device 100 transmits the generated hydraulic control signal to the hydraulic control device 600. In accordance with the hydraulic control signal, the hydraulic control device 600 controls the degree of opening and closing of the control valve 15. The control device 100 transmits the generated transmission control signal to the transmission control device 700. In accordance with the transmission control signal, the transmission control device 700 controls the gear ratio and rotational direction of the drive force transmission device 22.

[0017] Figure 3 is a functional block diagram of the control device shown in Figure 2. As shown in Figure 3, the control device 100 includes an action management unit 110, a target route planning unit 120, and an action generation unit 130. A positioning device 51 is connected to the action management unit 110, the target route planning unit 120, and the action generation unit 130 of the control device 100. An attitude sensor 52 is connected to the target route planning unit 120 and the action generation unit 130 of the control device 100. A vehicle speed sensor 53 is connected to the action generation unit 130 of the control device 100. In this embodiment, the positioning device 51 measures the position of the work vehicle 1. The positioning device 51 is a GNSS (Global Navigation Satellite System), but the present invention is not limited thereto, and the positioning device 51 may be configured using a known SLAM (Simultaneous Localization and Mapping) with a camera or LiDAR (Light Detection and Ranging).

[0018] The attitude sensor 52 detects the angle of the center joint 23 and the attitude of the work tool 5. The attitude sensor 52 includes a plurality of angle sensors that detect the angle between the front part 6 and the rear part 7 of the vehicle body, the angle of the lift arm 2 relative to the front part 6 of the vehicle body, and the angle of the work tool 5 relative to the lift arm 2. The vehicle speed sensor 53 is a wheel speed sensor that is provided on a shaft that rotates integrally with the front right tire 21FR, front left tire 21FL, rear right tire 21RR, and rear left tire 21RL of the work vehicle 1, for example, and detects the rotational speed of the shaft.

[0019] A user interface 60 is connected to the action management unit 110 of the control device 100. In this embodiment, the user interface 60 is a personal computer, tablet terminal, or smartphone, and may be any other device that can input work instructions, as described later.

[0020] The action management unit 110 receives work instructions from the user interface 60. The action management unit 110 receives position information, including vehicle orientation information, from the positioning device 51. The action management unit 110 determines the operating mode of the work vehicle 1 and transmits it to the action generation unit 130, and also calculates the target position and transmits it to the target route planning unit 120.

[0021] Here, the target position refers to the position and orientation of the work vehicle 1 during travel. The target position also refers to the position and orientation of the work tool 5 during work. Specifically, the position and orientation of the work vehicle 1 during travel refers to the position of the work vehicle 1 at the excavation position where excavation work is performed, the turning position where the direction of travel is changed (from reverse to forward) when traveling from the excavation position to the loading position, the loading position where loading work is performed, the turning position where the direction of travel is changed (from reverse to forward) when traveling from the loading position to the next excavation position, and the orientation of the work vehicle 1 at the turning position when traveling from the loading position to the next excavation position. The orientation of the work vehicle during travel refers to the angle between the front 6 and rear 7 of the vehicle body. The angle between the front 6 and rear 7 of the vehicle body is the angle of the center joint 23. The position and orientation of the work tool 5 during work refers to the height and ground angle of the work tool 5 during transport, excavation, and loading.

[0022] The target route planning unit 120 receives the operation mode and target position from the action management unit 110. The target route planning unit 120 receives position information from the positioning device 51. The target route planning unit 120 receives attitude information regarding the attitude of the work tool and the angle of the center joint 23 from the attitude sensor 52. If the operation mode is the driving operation mode, the target route planning unit 120 calculates the target route from the current position of the work vehicle 1 to the target position. In other words, the target route planning unit 120 plans the target route based on the position of the work vehicle 1 and the target position. If the operation mode is the work operation mode, the target route planning unit 120 calculates the target trajectory from the current attitude of the work tool 5 to the attitude of the target. The target route planning unit 120 transmits the target route and target trajectory to the action generation unit 130.

[0023] The motion generation unit 130 receives the motion mode from the action management unit 110. The motion generation unit 130 receives the target route from the target route planning unit 120. The motion generation unit 130 receives position information, including information regarding the orientation of the work vehicle 1, from the positioning device 51. The motion generation unit 130 receives attitude information from the attitude sensor 52 regarding the attitude of the work tool 5 and the angle of the center joint 23. The motion generation unit 130 receives the vehicle speed of the work vehicle 1 from the vehicle speed sensor 53. If the motion mode is the driving motion mode, the motion generation unit 130 generates a hydraulic control signal for the work vehicle 1 so that the position information of the work vehicle 1 follows as it drives, based on the target route, position information, the angle of the center joint 23, and the vehicle speed.

[0024] In other words, the motion generation unit 130 controls the movement of the work vehicle 1 by calculating the amount of steering of the steering mechanism of the work vehicle 1 based on the position of the work vehicle 1 and the target path, so that the work vehicle 1 follows the target path and reaches the target position. If the operation mode is the work operation mode, the motion generation unit 130 generates a hydraulic control signal based on the posture of the work tool 5 so that the work tool 5 moves along the target trajectory. The motion generation unit 130 transmits a transmission control signal to the transmission control device 700. The motion generation unit 130 transmits a hydraulic control signal to the hydraulic control device 600. The motion generation unit 130 generates an engine control signal to obtain the output of the engine 10 required for the driving operation mode and the work operation mode. The motion generation unit 130 transmits an engine control signal to the engine control device 500.

[0025] Figure 4 is a functional block diagram of the path following control performed by the motion generation unit 130 when the operating mode is the driving operation mode. In this embodiment, the path following control applies a known Pure Pursuit Model. As shown in Figure 4, the motion generation unit 130 includes a forward gaze distance calculation unit 131, a forward gaze point calculation unit 132, a target steering angle calculation unit 133, a target distance calculation unit 134, a target bending angular velocity calculation unit 135, a path following error calculation unit 136, a remaining driving distance calculation unit 137, and a steering limiting gain calculation unit 138. Figure 5 is a schematic diagram showing the relationship between the forward gaze point and the steering angle of the work vehicle 1 using the Pure Pursuit Model. The method for calculating the steering amount when the Pure Pursuit Model is applied to the work vehicle 1 will be described below using Figures 4 and 5.

[0026] The forward gaze distance calculation unit 131 shown in Figure 4 calculates the forward gaze distance d in the forward gaze model. P Calculate the target vehicle speed V cmd , forward gaze time t P Therefore, the forward gaze distance d shown in Figure 5 P This can be calculated using the following formula (1). In other words, the forward gaze point calculation unit 132 calculates a longer forward gaze distance as the vehicle speed of the work vehicle 1 increases. Note that the target vehicle speed V cmd This is the configuration information of the target route generated by the target route planning unit 120, but the actual vehicle speed of the work vehicle 1 obtained from the vehicle speed sensor 53 may also be used. Also, forward gaze time t P This is information that the motion generation unit 130 has pre-stored as parameters in the forward gaze model.

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[0027] The forward gaze point calculation unit 132 shown in Figure 4 calculates the forward gaze distance d from the forward gaze distance calculation unit 131. P The forward gaze point calculation unit 132 receives the target path from the target path planning unit 120. The forward gaze point calculation unit 132 receives position information from the positioning device 51. The forward gaze point calculation unit 132 receives the forward gaze distance d P Based on the target path and location information, a forward gaze point P is determined as shown in Figure 5.P Perform calculations.

[0028] Forward viewing point P P is the position P of the work vehicle 1 on the target path C Based on this, the forward viewing distance d P is set at a position d ahead. Also, the position P C can be calculated as the position on the target path that is closest to the work vehicle 1. The target path is a set of a starting point, a target position as an end point, and relay points provided at predetermined intervals between the starting point and the target position. If, on the target path, C Based on the position P P there is no target path to be referred to within the range d ahead, that is, if the target position of the target path is included within the range of the forward viewing distance d C Based on the position P P then the target position is set as the forward viewing point P P .

[0029] That is, the forward viewing point calculation unit 132, when the target position is not included in the range d ahead from the position P of the work vehicle 1, C sets the point on the target path d ahead from the position P of the work vehicle 1 as the forward viewing point P P . On the other hand, the forward viewing point calculation unit 132 sets the target position as the forward viewing point when the target position is included in the range d ahead from the position of the work vehicle 1. C From the position P of the work vehicle 1, when the target position is not included in the range d ahead P the forward viewing distance d P is set as the forward viewing point P. On the other hand, the forward viewing point calculation unit 132 sets the target position as the forward viewing point when the target position is included in the range d ahead from the position of the work vehicle 1. P When the target position is included in the range d ahead from the position of the work vehicle 1, the target position is set as the forward viewing point.

[0030] The target steering angle calculation unit 133 shown in FIG. 4 receives the forward viewing point P from the forward viewing point calculation unit 132. P The target steering angle calculation unit 133 receives position information from the positioning device 51. The target steering angle calculation unit 133 calculates the target steering angle δ from the forward viewing point P <, P and the position information. As shown in FIG. 5, the target steering angle δ is the target azimuth D Tag and the vehicle body azimuth D VehThis is the difference. The target direction is the forward gaze point P as seen from a reference point set on the work vehicle 1 (for example, the center of the axle in the left-right direction of the front part 6 of the vehicle body). P This refers to the direction of the front of the vehicle, and the vehicle body direction is the direction of the front of the vehicle (6).

[0031] The target distance calculation unit 134 shown in Figure 4 calculates the forward gaze point P from the forward gaze point calculation unit 132. P The target distance calculation unit 134 receives position information from the positioning device 51. The target distance calculation unit 134 receives forward gaze point P P The target distance d is calculated from the position information. The target distance d is calculated from the position P of the work vehicle 1 on the target route. C and forward gaze distance d P This is the distance to the forward gaze point P. As mentioned above, P If the target position is d, then target distance d < forward gaze distance d P And so, forward gaze point P P If it is not the target position, then target distance d = forward gaze distance d P Figure 5 shows that the target distance d = forward gaze distance d. P This is a diagram illustrating the case.

[0032] The target bending angular velocity calculation unit 135 shown in Figure 4 receives the target steering angle δ from the target steering angle calculation unit 133. The target bending angular velocity calculation unit 135 receives the target distance d from the target distance calculation unit 134. The target bending angular velocity calculation unit 135 receives attitude information from the attitude sensor 52. The target bending angular velocity calculation unit 135 receives the steering limiting gain K from the steering limiting gain calculation unit 138, which will be described later. S The target bending angular velocity calculation unit 135 receives the target steering angle δ, target distance d, attitude information, and steering limiting gain K. S Based on this, the target bending angular velocity ω θref Calculate.

[0033] As shown in Figure 5, the relationship between the target steering angle δ and the turning radius r of the work vehicle 1 can be calculated using the following equation (2). Note that in Figure 5, for the sake of explanation, the turning radius r is shown as small and the target steering angle δ as large, but in reality, the turning radius r is large and the target steering angle δ is small, so it can be approximated by the following equation (2).

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[0034] Furthermore, the relationship between the bending angle θ and the turning radius r of the work vehicle 1 can be calculated using the following equation (3). Note that l is the wheelbase length of the work vehicle 1, and the center joint 23 is positioned in the middle of the wheelbase. The bending angle θ is the angle formed by the front part 6 and the rear part 7 of the vehicle body.

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[0035] From equations (2) and (3), the forward gaze point P P The target bending angle θ when the target position is ref This can be calculated using the following formula (4).

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[0036] Using PID control, the bending angle θ of the work vehicle 1 is set to a target bending angle θ ref When controlled to this extent, the target bending angular velocity ω θref This can be calculated using the following formula (5). Note that the bending angle error e is equal to the target bending angle θ. ref This is the difference between this and the current bending angle θ of work vehicle 1. P , K I , K D These represent the proportional gain, integral gain, and differential gain in PID control, respectively. I , T D These are the integral time and derivative time in PID control, respectively. Steering limit gain K S This parameter, whose value is between 0 and 1, applies to the entire equation. That is, near the target position on the target path, the steering limiting gain K S The target bending angular velocity ω θref By restricting this, the deviation of the work vehicle 1's posture from the target posture when it reaches the target position is suppressed. As described above, the target bending angular velocity calculation unit 135 of the motion generation unit 130 calculates that when the work vehicle 1 reaches the forward gaze point P PThe target bending angular velocity ω is the steering amount relative to the bending angle θ, which is the controlled amount, so that it passes through the curve. θref The system calculates the movement of the work vehicle 1 and controls its movement.

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[0037] The path tracking error calculation unit 136 shown in Figure 4 receives the target path from the target path planning unit 120. The path tracking error calculation unit 136 receives position information from the positioning device 51. Based on the target path and position information, the path tracking error e Route The path-following error e is calculated as shown in Figure 6. Route This can be calculated as the minimum distance between the line segments connecting the starting point, intermediate points, and target position that constitute the target path, and a reference point set on the work vehicle 1 (for example, the center of the axle in the left-right direction of the front part 6 of the vehicle body). As described above, the motion generation unit 130 generates the function when the work vehicle 1 is at the forward gaze point P P The target bending angular velocity ω is the steering amount relative to the bending angle θ, which is the controlled amount, so that it passes through the curve. θref The system calculates the movement of the work vehicle 1 and controls its movement.

[0038] The remaining distance calculation unit 137 shown in Figure 4 receives the target route from the target route planning unit 120. The remaining distance calculation unit 137 receives its own position from the positioning device 51. Based on the target route and its own position, the remaining distance calculation unit 137 determines the position P of the work vehicle 1. C The remaining distance d represents the distance along the target route from the starting point to the target location. Goal The position P on the target path is calculated as shown in Figure 6. C Since this is known, the remaining distance calculation unit 137 calculates the distance between the remaining relay points to the target position and position P. C The nearest relay point and location P C By integrating each distance, the remaining distance d can be calculated. Goal It is possible to calculate this.

[0039] As shown in Figure 4, the steering limiting gain calculation unit 138 calculates the path following error e from the path following error calculation unit 136. Routereceives it. The steering limit gain calculation unit 138 receives the remaining travel distance d from the remaining travel distance calculation unit 137 Goal receives it. The steering limit gain calculation unit 138 uses the path following error e Route and the remaining travel distance d Goal to calculate the steering limit gain K S In this embodiment, the steering limit gain calculation unit 138 of the motion generation unit 130 uses the remaining travel distance d along the target path from the position P of the work vehicle 1 C to the target position to limit the target bending angular velocity ω Goal which is the steering amount. Further, the steering limit gain calculation unit 138 of the motion generation unit 130 uses the path following error e between the position P θref of the work vehicle 1 and the target path, and the remaining travel distance d C to limit the target bending angular velocity ω Route which is the steering amount. Goal and the remaining travel distance d θref Figure 7 is a diagram schematically showing the relationship between the path following error e

[0040] Figure 7 is a diagram schematically showing the relationship between the path following error e Route and the remaining travel distance d Goal and the steering limit gain K S In the graph of FIG. 7, the remaining travel distance d Goal is defined on the horizontal axis, and the path following error e Route is defined on the vertical axis. As shown in FIG. 7, first, in the region where the remaining travel distance d Goal exceeds the forward viewing distance d P , the steering limit gain calculation unit 138 sets the steering limit gain K Route to 1.0 regardless of the path following error e S and does not limit the target bending angular velocity ω θref . Conversely, in the region where the remaining travel distance d Goal is less than the forward viewing distance d P , the steering limit gain calculation unit 138 changes the steering limit gain K Route in accordance with the path following error e S . Specifically, when the path following error e Route is large, the steering limit gain calculation unit 138 increases the steering limit gain K S to prioritize path following performance, and when the work vehicle 1 reaches the target position, the position PC maintains the accuracy. On the other hand, the steering limit gain calculation unit 138 suppresses excessive steering when the path following error e Route is small by reducing the steering limit gain K S to prevent deterioration of the attitude when reaching the target position.

[0041] That is, in the present embodiment, the steering limit gain calculation unit 138 of the motion generation unit 130 limits the target bending angular velocity ω P which is the steering amount based on the path following error e Goal when the remaining travel distance d Route is shorter than the forward viewing distance d Goal . Further, the steering limit gain calculation unit 138 of the motion generation unit 130 restricts the target bending angular velocity ω θref which is the steering amount so that it becomes smaller as the path following error e Route becomes smaller, and restricts the target bending angular velocity ω θref which is the steering amount so that it becomes smaller as the remaining travel distance d Goal becomes shorter. θref

[0042] As shown in FIG. 7, in the region where the remaining travel distance d Goal is less than the forward viewing distance d P , first, second, and third threshold values that change according to the remaining travel distance d Route are set for the path following error e Goal . The second threshold value is smaller than the first threshold value, and the third threshold value is smaller than the second threshold value. A region below the first threshold value is defined by a straight line connecting the forward viewing distance d P on the horizontal axis and the first threshold value on the vertical axis. A region below the second threshold value is defined by a straight line connecting the forward viewing distance d P on the horizontal axis and the second threshold value on the vertical axis. A region below the third threshold value is defined by a straight line connecting the forward viewing distance d P on the horizontal axis and the third threshold value on the vertical axis. That is, all of the first, second, and third threshold values increase in proportion to the decrease in the remaining travel distance d Goal .

[0043] The remaining travel distance d GoalThe forward gaze distance d P In the region below the threshold, in the region above the first threshold, the steering limiting gain K S It is 1.0. Remaining distance d Goal The forward gaze distance d P In the region below the first threshold, and in the region above the second threshold, the steering limiting gain K S It is 0.7. Remaining distance d Goal The forward gaze distance d P In the region below the second threshold, and in the region above the third threshold, the steering limiting gain K S It is 0.3. Remaining distance d Goal The forward gaze distance d P In the region below the third threshold, the steering limiting gain K S It is 0.0.

[0044] Figure 8 is a flowchart showing the operation of the steering limiting gain calculation unit 138 of the embodiment according to the relationship in Figure 7. As shown in Figure 8, the steering limiting gain calculation unit 138 calculates the remaining distance d Goal The forward gaze distance d P Determine whether it is below (S11). Remaining distance d Goal The forward gaze distance d P If it is not below this value, the steering limiting gain calculation unit 138 calculates the steering limiting gain K S Let ω be 1.0 (S12), and the target bending angular velocity ω θref It does not restrict.

[0045] Remaining distance d Goal The forward gaze distance d P When it falls below this value, the steering limiting gain calculation unit 138 calculates the path following error e Route The remaining distance is d Goal It is determined whether the value is below the corresponding first threshold (S13). Path following error e Route The remaining distance is d Goal If it does not fall below the corresponding first threshold, the steering limiting gain calculation unit 138 calculates the steering limiting gain K S Let ω be 1.0 (S12), and the target bending angular velocity ω θref It does not restrict.

[0046] Path tracking error e Route The remaining distance is d Goal When the value falls below the corresponding first threshold, the steering limiting gain calculation unit 138 calculates the path following error e Route The remaining distance is d Goal It is determined whether the value is below the corresponding second threshold (S14). Path following error e Route The remaining distance is d Goal If the value does not fall below the corresponding second threshold, the steering limiting gain calculation unit 138 calculates the steering limiting gain K S Let ω be 0.7 (S15), and the target bending angular velocity ω θref Restrict.

[0047] Path tracking error e Route The remaining distance is d Goal When the value falls below the corresponding second threshold, the steering limiting gain calculation unit 138 calculates the path following error e Route The remaining distance is d Goal It is determined whether the value is below the corresponding third threshold (S16). Path following error e Route The remaining distance is d Goal If the value is not below the corresponding third threshold, the steering limiting gain calculation unit 138 calculates the steering limiting gain K S Let it be 0.3 (S17), and the target bending angular velocity ω θref Limit the path-following error e. Route The remaining distance is d Goal When it falls below the corresponding third threshold, the steering limiting gain calculation unit 138 calculates the steering limiting gain K S Let ω be 0.0 (S18), and the target bending angular velocity ω θref Limit this to 0. That is, maintain the current bending angle and do not steer.

[0048] Figure 9 shows the remaining distance d in Figure 7. Goal The forward gaze distance d P This shows specific operational examples in a shorter region than the specified range. Path-following error e Route This is the position error when the work vehicle 1 reaches the target position, and represents the distance from the target position. The steering limiting gain calculation unit 138 of the motion generation unit 130 calculates the path following error e Route When the steering limit gain K is large,S Set the path tracking error e to a large value. Route When it is small, steering limiting gain K S Set it to a small value.

[0049] For example, let's assume the target path-following accuracy is within a radius of 1m from the target position. Path-following error e Route If the distance is 1.5m, it falls outside the range of the target path-following accuracy, so the steering limiting gain calculation unit 138 calculates the steering limiting gain K S Let ω be 1.0, and the target bending angular velocity ω θref This is not limited. Conversely, the path-following error e Route If the distance is 0.5m, the steering limiting gain calculation unit 138 calculates the steering limiting gain K, as this is half of the target path-following accuracy. S By halving it to 0.5, the target bending angular velocity ω θref This limits excessive steering and suppresses excessive steering input. This prevents the vehicle's attitude upon reaching the target position from deviating from the target attitude. As described above, in this embodiment, the remaining distance d Goal and path tracking error e Route By restricting steering operations accordingly, the vehicle's posture upon reaching the target position can be made to follow the target posture during the automated driving of the work vehicle 1.

[0050] In the forward-looking model, position P of the work vehicle 1. C From forward gaze point P P The forward gaze distance d is the distance to the target. P This is an important parameter related to path-following ability and stability. Specifically, forward gaze distance d P When the distance is short, the ability to follow the target path improves, but the amount of steering required for path-following errors becomes larger, making steering changes and weaving more likely. Conversely, the forward gaze distance d P While a longer distance allows for more stable driving, it also reduces the ability to follow the target path, such as by taking shortcuts on curves. Therefore, the slower the speed of the work vehicle 1, the shorter the forward gaze distance d. P The forward gaze distance d is set to be shorter, and the faster the travel speed of the work vehicle 1, the greater the forward gaze distance d. PIt is common to set it to a long duration.

[0051] However, in the vicinity of the target position on the target path, i.e., the forward gaze distance d P The remaining distance to the target position is d Goal If the forward gaze point P is shorter, P The forward gaze distance d P Because the target position is set to be closer than the target, the path tracking error e Route There is a problem with excessive steering input. In the case of an automobile, even if the steering input increases sharply when the target position is reached, the steering angle of the tires only increases, and the posture of the vehicle does not change significantly. However, in the case of a work vehicle 1 such as a wheel loader equipped with an articulated steering mechanism, if the steering input increases sharply when the target position is reached, the front part 6 and the rear part 7 of the vehicle body bend sharply around the center joint 23, causing a large change in the posture of the vehicle body.

[0052] A work vehicle 1, such as a wheel loader, performs excavation and loading operations using a work tool 5 mounted on the front of the front of the vehicle body 6. Therefore, when it reaches the target position, its posture must be directly facing the object to be excavated and the object to be loaded. Consequently, if the posture of the vehicle when it reaches the target position deviates from the target posture, it will cause problems that hinder the excavation and loading operations.

[0053] On the other hand, in this embodiment, the motion generation unit 130 generates motion at the position P of the work vehicle 1. C The remaining distance d along the target route from the starting point to the target location. Goal Based on this, the steering amount is the target bending angular velocity ω θref This limits the remaining driving distance d Goal Depending on the target bending angular velocity ω θref This is restricted, and in the automated driving of work vehicle 1, the vehicle's posture upon reaching the target position can be made to follow the target posture.

[0054] Furthermore, in this embodiment, the motion generation unit 130 calculates the path tracking error e between the position of the work vehicle 1 and the target path. Route And, remaining distance d GoalBased on this, the steering amount is the target bending angular velocity ω θref This limits the path-following error e. Route and remaining distance d Goal Depending on the target bending angular velocity ω θref This is restricted, and in the automated driving of work vehicle 1, the vehicle's posture upon reaching the target position can be made to follow the target posture.

[0055] Furthermore, in this embodiment, the control device 100 using a forward gaze model has a forward gaze distance d P More remaining driving distance d Goal When the path following error e is short, Route and remaining distance d Goal Based on this, the steering amount is the target bending angular velocity ω θref This limits the forward gaze distance d. P More remaining driving distance d Goal The forward gaze point P is short. P The forward gaze distance d P Even when the target position is set to be closer than the target position, the sudden increase in steering input upon reaching the target position can be reduced. Therefore, in this embodiment, the large change in the vehicle's posture upon reaching the target position can be reduced.

[0056] In this embodiment, the motion generation unit 130 generates the path tracking error e Route The smaller the value, the greater the target bending angular velocity ω, which is the amount of steering input. θref The limit is set so that it is small, and the remaining distance d Goal The shorter the steering amount, the greater the target bending angular velocity ω. θref The path-following error e is restricted to be small. Route If the value is large, priority is given to path-following, and the position P of the work vehicle 1 when it reaches the target position is determined. C Maintaining accuracy, path tracking error e Route When the torque is small, it can suppress excessive steering and prevent the vehicle's posture from changing drastically when it reaches the target position.

[0057] Furthermore, in this embodiment, the work vehicle 1 is a wheel loader or the like, comprising a front section 6, a rear section 7, a center joint 23 that connects the front section 6 and the rear section 7 so as to be rotatable around a vertical axis, and a work tool 5 provided on the front of the front section 6. The work vehicle 1, such as a wheel loader, is equipped with an articulated steering mechanism that rotates by changing the angle between the front section 6 and the rear section 7 around the center joint 23.

[0058] As described above, in a work vehicle 1 such as a wheel loader equipped with an articulated steering mechanism, if the steering amount increases sharply when the target position is reached, the posture of the vehicle changes drastically, making it impossible to face the excavation target and loading target directly, which hinders the excavation and loading operations. However, in this embodiment, the path following error e Route If the value is large, priority is given to path-following, and the position P of the work vehicle 1 when it reaches the target position is determined. C Maintaining accuracy, path tracking error e Route When the steering angle is small, excessive steering can be suppressed, preventing deterioration of the vehicle's posture upon reaching the target position. This eliminates any disruption to the work and improves the work efficiency of the work vehicle 1, such as a wheel loader equipped with an articulated steering mechanism.

[0059] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are included. For example, the embodiments described above are described in detail to make the present invention easier to understand, and are not necessarily limited to those having all the configurations described. Furthermore, it is possible to add, delete, or replace some of the configurations of the embodiments with other configurations. [Explanation of Symbols]

[0060] 1. Work vehicles 2 Lift Arms 3. Bell Crank 4 Bucket Link 5. Work Tools 6 Front of the vehicle 7 Rear of the vehicle 10 Engines 11 Steering Cylinder 12 Lift Cylinders 13 Bucket Cylinder 14. Hydraulic pump 14F, 14R brakes 15 Control valve 21FR Front Right Tire 21FL Front left tire 21RR rear right tire 21RL Rear left tire 22 Power transmission device 23 Center Joint 24F Front Differential 24R Rear Differential 51 Positioning device 52 Attitude Sensors 53 Vehicle speed sensor 60 User Interfaces 100 Control device 110 Behavior Management Department 120 Target Route Planning Department 130 Motion generator 131 Forward gaze distance calculation unit 132 Forward gaze point calculation unit 133 Target steering angle calculation unit 134 Target distance calculation section 135 Target bending angular velocity calculation section 500 Engine Control Unit 600 Hydraulic control device 700 Transmission Control Unit 1000 control systems

Claims

1. A control device for a work vehicle that causes the work vehicle to travel along a target path, A target route planning unit plans the target route based on the position of the work vehicle and the target position, An action generation unit calculates the steering amount of the steering mechanism of the work vehicle and controls the movement of the work vehicle so that the work vehicle follows the target path, based on the position of the work vehicle and the target path. Equipped with, The control device for a work vehicle is characterized in that the motion generation unit limits the amount of steering based on the remaining distance traveled along the target path from the position of the work vehicle to the target position.

2. The control device for a work vehicle according to claim 1, characterized in that the motion generation unit limits the steering amount based on the path following error based on the position of the work vehicle relative to the target path and the remaining distance to travel.

3. The aforementioned motion generation unit, On the aforementioned target path, a forward gaze point is set a distance forward from the position of the work vehicle, and the steering amount is calculated to control the movement of the work vehicle so that the work vehicle passes through the forward gaze point. The faster the vehicle speed of the aforementioned work vehicle, the longer the forward gaze distance should be set. If the target position is not included in the range forward by the forward gaze distance from the position of the work vehicle, a point on the target path forward by the forward gaze distance from the position of the work vehicle is set as the forward gaze point. When the target position is included within the range forward by the forward gaze distance from the position of the work vehicle, the target position is set as the forward gaze point. The control device for a work vehicle according to claim 2, characterized in that when the remaining distance to travel is shorter than the forward gaze distance, the steering amount is limited based on the path following error and the remaining distance to travel.

4. The aforementioned motion generation unit, The smaller the aforementioned path-following error, the smaller the steering amount will be limited. The control device for a work vehicle according to claim 3, characterized in that the steering amount is limited to a smaller amount as the remaining distance to travel decreases.

5. The aforementioned work vehicle is The vehicle has a body in which the front and rear sections are connected in a flexible manner. The control device for a work vehicle according to claim 1, characterized in that it is equipped with a steering mechanism that steers by changing the angle between the front and rear of the vehicle body.

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