Articulated Vehicle

Abstract

To provide an articulate type vehicle capable of suppressing meandering travel while improving following accuracy to a target route.SOLUTION: An articulate type vehicle includes a front frame and a rear frame connected rotatably in a right and left direction. The articulate type vehicle includes a control device that controls operation of the articulate type vehicle. The control device sets a reference point of the articulate type vehicle at a position on a straight line passing a right and left center of an axle of a wheel of a frame in a travel direction side among the front frame and the rear frame, in a front and rear direction perpendicularly to a vehicle axis, the position being on the axle or in the travel direction side further from the axle, calculates a position of the reference point in a work site, and operates a steering control amount that is a bending amount of the front frame with respect to the rear frame on the basis of a target locus predetermined as a travel locus of the articulate type vehicle and a position of the reference point in the work site.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to articulated vehicles. [Background technology]

[0002] Conventionally, articulated vehicles have been used at construction sites, but there is a growing demand for autonomous driving of articulated vehicles due to reasons such as a shortage of operators. For the widespread adoption of autonomous driving of articulated vehicles, they need to be able to follow routes without meandering, from the perspective of fuel efficiency and cycle time.

[0003] A known technology for preventing meandering relative to a target travel route in the automatic travel of an articulated vehicle is described, for example, in Patent Document 1. Patent Document 1 discloses an autonomous travel control device that controls an autonomously traveling construction machine, and that outputs a control signal to correct the traveling direction of the construction machine so that it approaches the traveling reference line when the distance from a traveling reference line to the construction machine is greater than a predetermined first threshold, and outputs a control signal to make the traveling direction of the construction machine parallel to the traveling reference line when the distance from the traveling reference line to the construction machine becomes smaller than a second threshold that is the same as or smaller than the first threshold. [Prior art documents] [Patent documents]

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

[0005] However, in the above-mentioned conventional technology, since the reference point for the vehicle's own position may be behind the center of the axle of the frame ahead of the bend in the direction of travel, in an articulated vehicle in which the vehicle behind moves to follow the frame ahead in the direction of travel, there is a problem that the intervention of steering control in response to deviation from the target route is delayed, resulting in meandering. Also, although an attempt is made to maintain the vehicle's direction of travel parallel to the target route, an error in the vehicle's position relative to the target route is allowed as long as it is within an allowable range of positional deviation, so there is room for improvement in the accuracy of tracking the target route.

[0006] The present invention has been made in view of the above, and has an object to provide an articulated vehicle that can improve the accuracy of following a target route while suppressing meandering. [Means for solving the problem]

[0007] The present application includes a plurality of means for solving the above-mentioned problems, and one example thereof is an articulated vehicle having a front frame having a pair of left and right wheels, and a rear frame having a pair of left and right wheels and connected to the front frame so as to be rotatable in the left and right direction, the articulated vehicle being provided with a self-position sensor for detecting a position at a work site, and a control device for controlling the operation of the articulated vehicle, the control device being configured to detect a position on a straight line passing through the left and right centers of the axles of the wheels of the frame of the front frame or the rear frame that is closer to the traveling direction, perpendicular to the axles, in the front and rear directions. ,before A reference point for the articulated vehicle is set on the side of the axle in the direction of travel, and the position of the reference point at the work site is calculated based on the detection results of the self-position sensor. A steering control amount, which is the amount of bending of the front frame relative to the rear frame, is calculated based on a target trajectory that is predetermined as the travel trajectory of the articulated vehicle and the position of the reference point at the work site. [Effects of the Invention]

[0008] According to the present invention, meandering can be suppressed while improving the accuracy of following a target route. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a side view schematically showing a wheel loader. [Figure 2] FIG. 1 is a top view schematically showing a wheel loader. [Figure 3] FIG. 2 is a diagram illustrating the travel drive system of the wheel loader together with a control device and related configuration. [Figure 4] 2 is a functional block diagram illustrating functions of an automatic driving controller according to a first embodiment together with related configurations. FIG. [Figure 5] 10A and 10B are diagrams showing an example of setting a reference point for a vehicle body, and are diagrams showing an example of setting a reference point when moving forward. [Figure 6] 10A and 10B are diagrams showing an example of setting a reference point relative to a vehicle body, and are diagrams showing an example of setting a reference point when reversing; [Figure 7] FIG. 10 is a functional block diagram illustrating functions of an automatic driving controller according to a second embodiment together with related configurations. [Figure 8] 10 is a flowchart showing the processing contents of a reference point switching unit. [Figure 9] 10 is a flowchart showing the processing contents of a reference point correction amount calculation unit. [Figure 10] FIG. 10 is a functional block diagram illustrating functions of an automatic driving controller according to a third embodiment together with related configurations. [Figure 11] 10 is a flowchart showing the processing contents of a reference point switching unit. [Figure 12] FIG. 10 is a functional block diagram illustrating functions of an automatic driving controller according to a fourth embodiment together with related configurations. [Figure 13] 10 is a flowchart showing the processing content of a target position calculation unit. [Figure 14] 10 is a flowchart showing the processing contents of a reference point switching unit. [Figure 15]10 is a flowchart showing the processing content of a route plan setting unit. [Figure 16] 10 is a flowchart showing the processing content of a reference point switching determination unit. [Figure 17] FIG. 10 is a functional block diagram illustrating functions of an automatic driving controller according to a fifth embodiment together with related configurations. [Figure 18] 10 is a flowchart showing the processing contents of a reference point correction amount calculation unit. [Figure 19] 10 is a flowchart showing the processing content of a reference point switching determination unit. [Figure 20] 10 is a flowchart showing the processing contents of a speed control command calculation unit. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, a wheel loader will be used as an example of an articulated vehicle, but the present invention is not limited to this and can be applied to other articulated work machines. In the following description, when there are multiple identical components, an alphabet will be added to the end of the reference numeral (number), but the alphabet may be omitted to refer to the multiple components collectively. For example, when there are a pair of left and right front wheels 5a, 5b, these may be collectively referred to as the front wheels 5.

[0011] First Embodiment A first embodiment of the present invention will be described with reference to FIGS.

[0012] Fig. 1 is a side view that shows a schematic diagram of a wheel loader according to this embodiment, and Fig. 2 is a top view. Fig. 3 is a diagram that shows the wheel loader's travel drive system together with the control device and related configuration. In the following explanation, unless otherwise specified, the front, back, left, and right of the wheel loader 1 are based on the viewpoint of the operator who is riding on and operating the wheel loader 1.

[0013] 1 and 2, the wheel loader 1 is made up of a front frame 2 and a rear frame 3. A pair of left and right lift arms 8, a bucket 7, and a pair of left and right wheels (front wheels 5a, 5b) are attached to the front frame 2. A cab 4 in which an operator sits and a pair of left and right wheels (rear wheels 6a, 6b) are attached to the rear frame 3. The front frame 2 and the rear frame 3 are connected by a center pin 9 so that they can rotate in the left and right directions. The front frame 2 and the rear frame 3 are also connected by a pair of left and right steering cylinders 10a, 10b.

[0014] The front wheels 5a, 5b and rear wheels 6a, 6b are drive wheels that rotate when power is transmitted from an engine 11 (see Figure 3 below). A pair of left and right lift arms 8a, 8b are attached to the front end of the front frame 2 of the wheel loader 1 and spaced apart in the width direction (left and right direction). A bucket 7 is connected to the front ends of the pair of left and right lift arms 8a, 8b so that they can rotate in the vertical direction, and their rear ends are connected to the front end of the front frame 2 so that they can rotate in the vertical direction. By extending one of the pair of left and right steering cylinders 10a, 10b and simultaneously retracting the other, the front frame 2 and the rear frame 3 are bent in the left and right direction around a center pin 9.

[0015] In FIG. 3, the wheel loader 1 is generally composed of an engine 11, a torque converter 12, a transmission 13, a brake 14, a hydraulic pump 15, a drive shaft 16, an axle shaft 17, an operating device 20, a control device 30, and a hydraulic circuit 40.

[0016] The engine 11 is, for example, a prime mover that generates driving force by burning fossil fuel.

[0017] The torque converter 12 is connected to the output shaft of the engine 11 and the input shaft of the transmission 13, and adjusts the driving force transmitted from the engine 11 to the transmission 13, i.e., transmits a portion of the driving force of the engine 11 to the transmission 13.

[0018] The transmission 13 changes the speed of the driving force of the engine 11 transmitted via the torque converter 12, and transmits the changed speed driving force to the drive wheels (front wheels 5a, 5b and rear wheels 6a, 6b) via a drive shaft 16 and an axle shaft 17. The transmission 13 is also switchable between a forward state in which the drive wheels rotate in a direction that moves the wheel loader 1 forward, and a reverse state in which the drive wheels rotate in a direction that moves the wheel loader 1 backward.

[0019] Brakes 14a, 14b, 14c, and 14d brake the rotation of front wheels 5a and 5b and rear wheels 6a and 6b. Brakes 14 are provided at four locations corresponding to the front wheels 5a and 5b and rear wheels 6a and 6b, respectively.

[0020] The hydraulic pump 15 is connected to and driven by the output shaft of the engine 11. The hydraulic pump 15 pumps hydraulic oil stored in a hydraulic oil tank (not shown) to a hydraulic circuit 40 by using the driving force transmitted from the engine 11.

[0021] The hydraulic circuit 40 is composed of a directional control valve and the like, and controls the flow rate and direction of hydraulic oil discharged from the hydraulic pump 15 and supplied to the hydraulic actuators (brake 14, steering cylinders 10a, 10b) in accordance with an operation signal output from the operating device 20 or a control signal output from the control device 30.

[0022] The operating device 20 operates the wheel loader 1 by outputting an operating signal to the control device 30 in response to the operator's operation, and includes, for example, an accelerator pedal 21, a forward / reverse command switch 22, a brake pedal 23, and a steering wheel 24.

[0023] The accelerator pedal 21 adjusts the rotation speed of the engine 11 in response to operation by the operator. The accelerator pedal 21 outputs an operation signal to the control device 30 that indicates the amount of depression by the operator.

[0024] The forward / reverse instruction switch 22 is an alternate switch that indicates the traveling direction state of the wheel loader 1 in response to operation by the operator. For example, when the forward / reverse instruction switch 22 is switched to the forward position, the transmission 13 is switched to the forward state. When the forward / reverse instruction switch 22 is switched to the reverse position, the transmission 13 is switched to the reverse state. The forward / reverse instruction switch 22 outputs an operation signal indicating the current position to the control device 30.

[0025] The brake pedal 23 adjusts the braking force of the brake 14 in response to operation by the operator. The brake pedal 23 outputs an operation signal to the control device 30 that indicates the amount of depression by the operator.

[0026] The steering wheel 24 extends and retracts the steering cylinders 10a and 10b in response to operation by the operator. For example, when the operator rotates the steering wheel 24 to the right (clockwise), the left steering cylinder 10a extends and the right steering cylinder 10b retracts, causing the front frame 2 to bend to the right relative to the rear frame 3. On the other hand, when the operator rotates the steering wheel 24 to the left (counterclockwise), the left steering cylinder 10a retracts and the right steering cylinder 10b extends, causing the front frame 2 to bend to the left relative to the rear frame 3. The steering wheel 24 outputs a rotation direction and an operation signal corresponding to the rotation direction to the control device 30.

[0027] The control device 30 controls the operation of the wheel loader 1 based on operation signals output from the operating device 20 and detection signals output from various sensors described below. Although not shown, the control device 30 includes a CPU (Central Processing Unit), ROM (Read Only Memory), and RAM (Random Access Memory). The control device 30 realizes each of the functional blocks described below by having the CPU read and execute program code stored in the ROM. The RAM is used as a work area when the CPU executes the program. However, the specific configuration of the control device 30 is not limited to this, and the control device 30 may be realized by other hardware.

[0028] The control device 30 includes, for example, an engine controller 31, a transmission controller 32, a vehicle body controller 33, and an automatic driving controller 34. For example, the engine controller 31, the transmission controller 32, and the vehicle body controller 33 may each be independent hardware and connected to each other so as to be able to communicate with each other via a controller area network (CAN). As another example, the engine controller 31, the transmission controller 32, and the vehicle body controller 33 may each be configured to be realized by a CPU executing a program stored in a ROM.

[0029] The engine controller 31 increases or decreases the rotation speed of the engine 11 in response to an operation signal indicating the depression amount of the accelerator pedal 21. The transmission controller 32 switches the state of the transmission 13 between a forward state and a reverse state in response to an operation signal indicating the position of the forward / reverse command switch 22. The vehicle body controller 33 controls the braking force of the brake 14 in response to an operation signal indicating the depression amount of the brake pedal 23.

[0030] (Automatic Driving Controller 34) FIG. 4 is a functional block diagram illustrating the functions of the automatic driving controller together with the related configuration.

[0031] 4, the automatic traveling controller 34 has a reference point correction amount calculation unit 101, a self-position calculation unit 102, a target trajectory setting unit 103, and a steering control command calculation unit 104. The automatic traveling controller 34 controls the automatic traveling of the wheel loader 1 (including assistance from the operator), and controls the operation of the hydraulic circuit 40 based on a detection signal output from a self-position sensor 50, thereby controlling the operation of the steering cylinders 10a, 10b and the brakes 14a, 14b, 14c, 14d, etc.

[0032] The self-position sensor 50 detects the self-position of the vehicle body of the wheel loader 1 and outputs it as self-position information to the self-position calculation unit 102. The self-position sensor 50 is, for example, a GNSS (Global Navigation Satellite System), and outputs the current latitude and longitude coordinates as the positioning result. Note that the self-position sensor 50 is not limited to this and may be realized by other means. Here, the self-position detected by the self-position sensor 50 is, for example, the position of a GNSS antenna installed on the wheel loader 1.

[0033] The reference point correction amount calculation unit 101 calculates a reference point correction amount for correcting the self-position detected by the self-position sensor 50 to the position of a reference point set on the wheel loader 1, and outputs the calculated reference point correction amount to the self-position calculation unit 102.

[0034] 5 and 6 are diagrams showing examples of setting reference points for the vehicle body, with FIG. 5 showing an example of setting reference points when moving forward and FIG. 6 showing an example of setting reference points when moving backward.

[0035] As shown in Figure 5, when the wheel loader 1 moves forward, the front frame 2 is in the front (in the direction of travel) and the rear frame 3 is in the rear. At this time, a reference point is set at the left-right center of the frame located in the front (in the direction of travel) (i.e., the front frame 2). More specifically, the reference point is set on a straight line 100 that passes through the left-right center of the axles (axle shafts 17a, 17b) of the wheels (front wheels 5a, 5b) of the frame (front frame 2) that is closer to the direction of travel of the front frame 2 or the rear frame 3, in the front-to-rear direction and perpendicular to the axles, and between the axles of the front wheels 5a, 5b and the tip of the bucket 7.

[0036] As shown in Figure 6, when the wheel loader 1 is reversing, the rear frame 3 is in front (in the direction of travel) and the front frame 2 is in the rear. At this time, a reference point is set at the left-right center of the frame located in the front (in the direction of travel) (i.e., the rear frame 3). More specifically, the reference point is set on a straight line 100 that passes through the left-right center of the axles of the wheels (rear wheels 6a, 6b) of the frame (rear frame 3) that is on the side closest to the direction of travel of the front frame 2 or the rear frame 3, in the front-to-rear direction, perpendicular to the axles, and between the axles of the rear wheels 6a, 6b and the rear end of the rear frame 3 (the end in the direction of travel).

[0037] The self-position calculation unit 102 calculates the position of the reference point at the work site (i.e., the coordinate position in the work site coordinate system or the Earth coordinate system) based on the signal (self-position information) from the self-position sensor 50 and the calculation result (reference point correction amount) of the reference point correction amount calculation unit 101, and outputs it to the steering control command calculation unit 104.

[0038] The target trajectory setting unit 103 sets a target trajectory along which the wheel loader 1 travels, sets a target position on the target trajectory, and outputs it to the steering control command calculation unit 104. The target trajectory setting unit 103 forms a target trajectory, for example, by arranging a plurality of target coordinates in advance, and outputs one target coordinate of the target trajectory as the target position. Note that the method for setting the target trajectory and target position by the target trajectory setting unit 103 is not limited to this, and other methods may also be used.

[0039] The steering control command calculation unit 104 calculates the bending angle of the vehicle body as a steering control amount based on the position of the reference point from the self-position calculation unit 102 and the target position from the target trajectory setting unit 103, and outputs it as a control command to the hydraulic circuit 40. That is, the control command output from the steering control command calculation unit 104 is a command to control a directional control valve that controls the direction and flow rate of hydraulic oil supplied to the steering cylinders 10a, 10b.

[0040] Here, the bending angle of the vehicle body refers to the amount of bending between the front frame 2 and the rear frame 3, and is 0 (zero) when the axles of the front wheels 5a, 5b and the axles of the rear wheels 6a, 6b are parallel, that is, when the front frame 2 and the rear frame 3 are straight. The calculation of the bending angle of the vehicle body by the steering control command calculation unit 104 is performed, for example, assuming that the wheel loader 1 is making a turn such that the reference point passes through the target position, by taking the angle formed by the line connecting the turning center position and the target position and the line connecting the turning center position and the reference point, that is, the angle at the turning center position, as the bending angle of the vehicle body. However, the method of calculating the bending angle by the steering control command calculation unit 104 is not limited to this, and other methods may also be used.

[0041] The effects of the present embodiment configured as above will be described.

[0042] In an articulated vehicle, if the reference point for the vehicle's own position is behind the center of the axle of the frame ahead of the bend in the direction of travel, controlling the rear vehicle to follow the frame ahead in the direction of travel can cause a problem of meandering due to a delay in steering control intervention in response to deviation from the target route.Furthermore, controlling the vehicle to maintain its direction of travel parallel to the target route can cause a problem of reduced accuracy in following the target route, as errors in the vehicle's position relative to the target route are tolerated as long as the positional deviation is within an allowable range.

[0043] In contrast, in this embodiment, a reference point for the wheel loader 1, which is an articulated vehicle, is set on the axle or on the side of the axle in the traveling direction of the frame of the front frame 2 or the rear frame 3 that is closest to the traveling direction, on a line that passes through the lateral center of the wheel axle in the front-to-rear direction perpendicular to the axle. The position of the reference point at the work site is calculated based on the detection results of the self-position sensor. Then, a steering control amount, which is the amount of bending of the front frame 2 relative to the rear frame 3, is calculated based on a target trajectory that is predetermined as the travel trajectory of the wheel loader 1 and the position of the reference point at the work site. As a result, the distance from the lateral center of the wheel axle (axle shafts 17a, 17b) of the frame (front frame 2 or rear frame 3) located on the traveling direction side (front) to the target trajectory is equal to or less than the distance from the lateral center of the wheel axle of the frame (front frame 2 or rear frame 3) located on the opposite side to the traveling direction (rear), so that the frame located on the traveling direction side (front) can follow the target trajectory without meandering relative to the target trajectory. In other words, meandering travel can be suppressed while improving the accuracy of following the target path.

[0044] <Second embodiment> A second embodiment of the present invention will be described with reference to FIGS.

[0045] The wheel loader of this embodiment is configured so that the reference point of the wheel loader is set in accordance with the direction of travel indicated by a forward / reverse instruction switch that can be switched by the operator. Note that in this embodiment, the same components as those in the first embodiment are given the same reference numerals and descriptions thereof will be omitted.

[0046] FIG. 7 is a functional block diagram illustrating the functions of the automatic driving controller according to this embodiment together with the related configuration.

[0047] 7, the automatic driving controller 34A has a reference point switching unit 505, a reference point correction amount calculation unit 501, a self-position calculation unit 102, a target trajectory setting unit 103, and a steering control command calculation unit 104.

[0048] The reference point switching unit 505 receives an operation signal from the forward / reverse instruction switch 22, determines whether the transmission 13 is in a forward state or a reverse state, and outputs the determination result to the reference point correction amount calculation unit 501.

[0049] FIG. 8 is a flowchart showing the processing contents of the reference point switching unit.

[0050] In FIG. 8, when the reference point switching unit 505 of the automatic driving controller 34A detects an operation signal from the forward / reverse instruction switch 22 (step S100), it determines whether the detected operation signal from the forward / reverse instruction switch 22 is a signal indicating a forward position (step S110).

[0051] If the determination result in step S110 is YES, the determination result that the transmission 13 is in the forward state is output to the reference point correction amount calculation unit 501 (step S120), and the process ends.

[0052] If the determination result in step S110 is NO, the determination result that the transmission 13 is in reverse is output to the reference point correction amount calculation unit 501 (step S130), and the process ends.

[0053] The reference point correction amount calculation unit 501 calculates the reference point correction amount depending on the judgment result from the reference point switching unit 505, i.e., whether the transmission 13 is in a forward state or a reverse state, and outputs the calculated reference point correction amount to the self-position calculation unit 102.

[0054] FIG. 9 is a flowchart showing the processing contents of the reference point correction amount calculation unit.

[0055] In FIG. 9, the reference point correction amount calculation unit 501 of the automatic driving controller 34 first acquires the determination result from the reference point switching unit 505 (step S200), and determines whether the determination result indicates a forward movement state (step S210).

[0056] If the determination result in step S210 is YES, the reference point correction amount for forward movement, that is, the reference point correction amount when setting the reference point on a straight line passing through the center of the left and right axles of the front wheels 5 of the front frame 2 on the direction of travel in the longitudinal direction perpendicular to the axles, between the axles of the front wheels 5 and the tip of the bucket 7, is output to the self-position calculation unit 102 (step S220), and the processing is terminated.

[0057] Furthermore, if the determination result in step S210 is NO, the reference point correction amount when reversing, that is, the reference point correction amount when setting the reference point on a straight line passing through the center of the left and right axles of the rear wheels 6 of the rear frame 3 on the forward direction side in the longitudinal direction perpendicular to the axles, between the axles of the rear wheels 6 and the rear end of the rear frame 3 (the end on the forward direction side), is output to the self-position calculation unit 102 (step S230), and the processing is terminated.

[0058] The other configurations are the same as those in the first embodiment.

[0059] The present embodiment configured as above can also achieve the same effects as the first embodiment.

[0060] Furthermore, since the reference point is corrected (switched) in response to the operation of the forward / reverse command switch 22 by the operator, it is possible to more reliably improve the accuracy of following the target route and suppress meandering.

[0061] <Third embodiment> A third embodiment of the present invention will be described with reference to FIGS.

[0062] The wheel loader of this embodiment is configured to set a reference point for the wheel loader in accordance with the detection results from a vehicle body information acquisition sensor that detects vehicle body information (acceleration direction). Note that in this embodiment, the same components as those in the first and second embodiments are given the same reference numerals and descriptions thereof will be omitted.

[0063] FIG. 10 is a functional block diagram illustrating the functions of the automatic driving controller according to this embodiment together with the related configuration.

[0064] 10, the automatic driving controller 34B has a reference point switching unit 805, a reference point correction amount calculation unit 501, a self-position calculation unit 102, a target trajectory setting unit 103, and a steering control command calculation unit 104.

[0065] The reference point switching unit 805 determines whether the transmission 13 is in a forward or reverse state according to the detection result from the vehicle body information acquisition sensor 51 , and outputs the determination result to the reference point correction amount calculation unit 501 .

[0066] The vehicle body information acquisition sensor 51 is a device capable of detecting acceleration, such as an IMU (Inertial Measurement Unit), and is installed on the wheel loader 1 so as to detect and output positive acceleration when the wheel loader 1 is moving forward (i.e., moving in the direction of the front frame 2), and detect and output negative acceleration when the wheel loader 1 is moving backward (i.e., moving in the direction of the rear frame 3). However, the configuration of the vehicle body information acquisition sensor 51 is not limited to this, and it may be configured to be realized by other means.

[0067] FIG. 11 is a flowchart showing the processing contents of the reference point switching unit.

[0068] In FIG. 11, when the reference point switching unit 805 of the automatic driving controller 34A acquires a detection result from the vehicle body information acquisition sensor 51 (step S300), it determines whether the acceleration, which is the acquired detection result, is positive (step S310).

[0069] If the determination result in step S310 is YES, that is, if it is determined that the acceleration is positive and the wheel loader 1 is proceeding toward the front frame 2, the determination result that the transmission 13 is in a forward movement state is output to the reference point correction amount calculation unit 501 (step S320), and the processing ends.

[0070] Furthermore, if the determination result in step S310 is NO, that is, if it is determined that the acceleration is negative and the wheel loader 1 is proceeding toward the rear frame 3, the determination result that the transmission 13 is in a reverse state is output to the reference point correction amount calculation unit 501 (step S330), and the process ends.

[0071] The reference point correction amount calculation unit 501 calculates the reference point correction amount depending on the judgment result from the reference point switching unit 805, i.e., whether the transmission 13 is in a forward state or a reverse state, and outputs the calculated reference point correction amount to the self-position calculation unit 102.

[0072] The other configurations are the same as those of the first and second embodiments.

[0073] The present embodiment configured as above can also achieve the same effects as the first and second embodiments.

[0074] Furthermore, the reference point is configured to be corrected (switched) according to the detection results of the vehicle body information acquisition sensor 51 as the wheel loader 1 travels, thereby more reliably improving the accuracy of following the target route while suppressing meandering travel.

[0075] <Fourth embodiment> A fourth embodiment of the present invention will be described with reference to FIGS.

[0076] The wheel loader of this embodiment is configured so that a reference point for the wheel loader 1 is set in accordance with the direction of travel determined based on the position of the reference point at the work site and the target position, and when the reference point is changed, the route plan is switched in accordance with the position of the reference point on the articulated vehicle. Note that in this embodiment, components similar to those in the first to third embodiments are given the same reference numerals and descriptions thereof will be omitted.

[0077] FIG. 12 is a functional block diagram illustrating the functions of the automatic driving controller according to this embodiment together with the related configuration.

[0078] In Figure 12, the automatic driving controller 34C has a reference point switching unit 1005, a route planning setting unit 1006, a reference point switching determination unit 1007, a reference point correction amount calculation unit 501, a self-position calculation unit 102, a target position calculation unit 1003, and a steering control command calculation unit 104.

[0079] The target position calculation unit 1003 calculates the target position based on the position of the reference point from the self-position calculation unit 102 and the route plan from the route plan setting unit 1006, and outputs the calculation result to the steering control command calculation unit 104 and the reference point switching determination unit 1007.

[0080] FIG. 13 is a flowchart showing the processing contents of the target position calculation unit.

[0081] 13, the target position calculation unit 1003 of the automatic driving controller 34C first acquires calculation results from the self-position calculation unit 102 and the route plan setting unit 1006 (step S400), and calculates a target position from the position of the reference point from the self-position calculation unit 102 and the target coordinates of the route plan from the route plan setting unit 1006 (step S410). The calculation of the target position in the target position calculation unit 1003 is performed, for example, by interpolating a route using a spline function based on the current position of the reference point and the current target coordinates, and setting the target position to a position a certain distance along the interpolated route from the current position of the reference point. However, the method of calculating the target position is not limited to this, and other methods may be used.

[0082] After the process of step S410 is completed, the target position calculated in step S410 is output to the steering control command calculation unit 104 and the reference point switching determination unit 1007 (step S420), and the process ends.

[0083] The reference point switching unit 1005 receives the determination result from the reference point switching determination unit 1007 and determines whether the wheel loader 1 is in a forward or backward state. The determination result is output to the reference point correction amount calculation unit 501. The reference point switching determination unit 1007 determines whether the traveling direction of the wheel loader 1 has been switched based on the position of the reference point from the self-position calculation unit 102 and the target position from the target position calculation unit 1003, and outputs the traveling state of the wheel loader 1 as the determination result; details of this processing will be described later.

[0084] FIG. 14 is a flowchart showing the processing contents of the reference point switching unit.

[0085] In FIG. 14, the reference point switching unit 1005 of the automatic driving controller 34C acquires the judgment result from the reference point switching judgment unit 1007 (step S500), and determines whether the acquired judgment result indicates a forward movement state (step S510).

[0086] If the determination result in step S510 is YES, the determination result that the wheel loader 1 is in a forward movement state (in other words, the transmission 13 is in a forward movement state) is output to the reference point correction amount calculation unit 501 (step S520), and the processing ends.

[0087] Furthermore, if the determination result in step S510 is NO, the determination result that the wheel loader 1 is in a reverse state (in other words, the transmission 13 is in a reverse state) is output to the reference point correction amount calculation unit 501 (step S530), and the processing ends.

[0088] The path plan setting unit 1006 sets a path plan to be output to the target position calculation unit 1003 based on the determination result from the reference point switching unit 1005. The path plan output to the target position calculation unit 1003 sets a target trajectory for the wheel loader 1 to travel, and for example, the target trajectory is configured by arranging target coordinates in sequence from a start position to a target arrival position. Furthermore, because the path plan setting unit 1006 determines the target coordinates based on the position of the reference point, it has different path plans for forward and reverse travel, which have different reference points on the wheel loader 1. The path plan for forward travel is configured with target coordinates based on the reference point in the forward state, and the path plan for reverse travel is configured with target coordinates based on the reference point in the reverse state. However, the configuration of the path plan setting unit 1006 is not limited to this and may be configured to be realized by other means.

[0089] FIG. 15 is a flowchart showing the processing content of the route plan setting unit.

[0090] In FIG. 15, the route plan setting unit 1006 of the automatic driving controller 34C acquires the determination result from the reference point switching unit 1005 (step S600), and determines whether the acquired determination result indicates a forward movement state (step S610).

[0091] If the determination result in step S610 is YES, the path plan corresponding to the reference point when the wheel loader 1 is moving forward is output to the target position calculation unit 1003 (step S520), and the process ends.

[0092] If the determination result in step S610 is NO, the path plan corresponding to the reference point when the wheel loader is moving backward is output to the target position calculation unit 1003 (step S630), and the process ends.

[0093] The reference point switching determination unit 1007 determines whether to switch the traveling direction of the wheel loader 1 based on the position of the reference point from the self-position calculation unit 102 and the target position from the target position calculation unit 1003, and outputs the determination result to the reference point switching unit 1005. For example, if the initial state is a forward traveling state, when the traveling direction of the wheel loader 1 is switched, a determination result indicating a switch to a reverse traveling state is output to the reference point switching unit 1005. At this time, until it is determined that the traveling direction of the wheel loader 1 will be switched, a determination result indicating a forward traveling state is output to the reference point switching unit 1005. However, the specific configuration of the reference point switching determination unit 1007 is not limited to this, and it may be configured to be realized by other means.

[0094] FIG. 16 is a flowchart showing the processing contents of the reference point switching determination unit.

[0095] In FIG. 16, the reference point switching determination unit 1007 of the automatic driving controller 34C acquires the calculation results from the self-position calculation unit 102 and the target position calculation unit 1003 (step S700), and based on the acquired calculation results, calculates a vector from the current reference point position at the work site to the target position (step S710), and also calculates a vector from the current reference point position at the work site to the previous reference point position (step S720).

[0096] Next, it is determined whether the angle formed by the vectors calculated in steps S710 and S720 is 90 degrees or greater (step S730), and if the determination result is YES, the determination result indicating the previous traveling direction state (forward or backward state) is output to the reference point switching unit 1005 (step S740), the current position of the reference point at the work site and the traveling direction state are recorded (step S760), and the processing ends. The recorded current position of the reference point and the traveling direction state are used as the previous position of the reference point and the traveling direction state at the next determination process in the reference point switching determination unit 1007.

[0097] If the determination result in step S730 is NO, it is determined whether the previous traveling direction state was a forward state (step S750). If the determination result in step S750 is YES, a determination result indicating a reverse state is output to reference point switching unit 1005 (step S751), and the process proceeds to step S760. If the determination result in step S750 is NO, a determination result indicating a forward state is output to reference point switching unit 1005 (step S752), and the process proceeds to step S760.

[0098] The other configurations are the same as those of the first to third embodiments.

[0099] The present embodiment configured as above can also achieve the same effects as the first to third embodiments.

[0100] Furthermore, since the reference point correction amount is configured to be switched depending on the route plan and the position of the reference point, the reference point of the wheel loader 1 is automatically corrected depending on the direction of travel, making it possible to more reliably improve the accuracy of following the target route while suppressing meandering travel.

[0101] <Fifth embodiment> A fourth embodiment of the present invention will be described with reference to FIGS.

[0102] The wheel loader of this embodiment is configured so that, when the position of the reference point on the vehicle body is changed, a speed control amount is calculated, which is the target traveling speed of the wheel loader at the work site, and braking is applied so that the distance between the target position and the position of the reference point at the work site is equal to or less than the distance between the target position before the reference point was changed and the position of the reference point at the work site. Note that in this embodiment, components that are the same as those in the first to fourth embodiments are given the same reference numerals and descriptions thereof will be omitted.

[0103] FIG. 17 is a functional block diagram illustrating the functions of the automatic driving controller according to this embodiment together with the related configuration.

[0104] In Figure 17, the automatic driving controller 34D has a reference point switching unit 1005, a reference point correction amount calculation unit 1501, a route planning setting unit 1506, a reference point switching determination unit 1507, a speed control command calculation unit 1508, a self-position calculation unit 102, a target position calculation unit 1003, and a steering control command calculation unit 104.

[0105] The reference point correction amount calculation unit 1501 calculates the reference point correction amount depending on the determination result from the reference point switching unit 1005, i.e., whether the wheel loader 1 (in other words, the transmission 13) is in a forward or reverse state, and outputs the calculated reference point correction amount to the self-position calculation unit 102.

[0106] FIG. 18 is a flowchart showing the processing contents of the reference point correction amount calculation unit.

[0107] In FIG. 18, the reference point correction amount calculation unit 1501 of the automatic driving controller 34D first acquires the determination result from the reference point switching unit 1005 (step S800), and determines whether the determination result indicates a forward movement state (step S810).

[0108] If the determination result in step S810 is YES, the reference point correction amount for forward movement, that is, the reference point correction amount when setting the reference point on a straight line passing through the center of the left and right axles of the front wheels 5 of the front frame 2 on the direction of travel in the longitudinal direction perpendicular to the axles, between the axles of the front wheels 5 and the tip of the bucket 7, is output to the self-position calculation unit 102 (step S820), and the processing is terminated.

[0109] Also, if the determination result in step S810 is NO, the reference point correction amount when reversing, that is, the reference point correction amount when setting the reference point on a straight line passing through the center of the left and right axles of the rear wheels 6 of the rear frame 3 on the forward direction side in the longitudinal direction perpendicular to the axles, from the axles of the rear wheels 6 to the rear end of the rear frame 3 (the end on the forward direction side), is output to the self-position calculation unit 102 (step S830), and the processing is terminated.

[0110] The route plan setting unit 1506 outputs the route plan to the target position calculation unit 1003 . The route plan output to the target position calculation unit 1003 sets a target trajectory for traveling the wheel loader 1, and for example, the target trajectory is configured by sequentially arranging target coordinates from a start position to a target arrival position. However, the specific configuration of the route plan setting unit 1506 is not limited to this, and may be realized by other means.

[0111] The reference point switching determination unit 1507 determines whether to switch the traveling direction of the wheel loader 1 based on the position of the reference point from the self-position calculation unit 102 and the target position from the target position calculation unit 1003, and outputs the determination result to the reference point switching unit 1005. For example, if the initial state is a forward traveling state, when the traveling direction of the wheel loader 1 is switched, a determination result indicating a switch to a reverse traveling state is output to the reference point switching unit 1005. At this time, until it is determined that the traveling direction of the wheel loader 1 will be switched, a determination result indicating a forward traveling state is output to the reference point switching unit 1005. However, the specific configuration of the reference point switching determination unit 1507 is not limited to this, and it may be configured to be realized by other means.

[0112] FIG. 19 is a flowchart showing the processing contents of the reference point switching determination unit.

[0113] In FIG. 19, the reference point switching determination unit 1507 of the automatic driving controller 34D acquires the calculation results from the self-position calculation unit 102 and the target position calculation unit 1003 (step S900), and based on the acquired calculation results, calculates a vector from the current reference point position at the work site to the target position (step S910), and also calculates a vector from the current reference point position at the work site to the previous reference point position (step S920).

[0114] Next, it is determined whether the angle formed by the vectors calculated in steps S910 and S920 is 90 degrees or greater (step S930), and if the determination result is YES, the determination result indicating the previous traveling direction state (forward or backward state) is output to the reference point switching unit 1005 (step S940), the current position of the reference point at the work site and the traveling direction state are recorded (step S960), and the processing ends. The recorded current position of the reference point and the traveling direction state are used as the previous position of the reference point and the traveling direction state at the next determination process in the reference point switching determination unit 1507.

[0115] If the determination result in step S930 is NO, it is determined whether the previous traveling direction state was a forward state (step S950). If the determination result in step S950 is YES, a determination result indicating that the traveling direction state has been switched is output to speed control command calculation unit 1508, and a determination result indicating a reverse state is output to reference point switching unit 1005 (step S951), and the process proceeds to step S960. If the determination result in step S950 is NO, a determination result indicating that the traveling direction state has not been switched is output to speed control command calculation unit 1508, and a determination result indicating a forward state is output to reference point switching unit 1005 (step S952), and the process proceeds to step S960.

[0116] The speed control command calculation unit 1508 determines whether it is necessary to control the braking force of the vehicle body based on the position of the reference point from the self-position calculation unit 102, the target position from the target position calculation unit 1003, and the determination result from the reference point switching determination unit 1507, and calculates the necessary control command and outputs it to the hydraulic circuit 40. For example, if the brake 14 is configured to brake the rotation of the drive wheels by clamping a brake disc that rotates integrally with each drive wheel between a pair of brake shoes, the control command output to the hydraulic circuit 40 is a control command for a valve that supplies hydraulic oil to the brake shoes that clamp the brake disc. However, the specific configurations of the speed control command calculation unit 1508 and the brake 14 are not limited to these, and they may be configured to be realized by other means.

[0117] FIG. 20 is a flowchart showing the processing contents of the speed control command calculation unit.

[0118] In FIG. 20, the speed control command calculation unit 1508 of the automatic driving controller 34D acquires the calculation results and the judgment results from the self-position calculation unit 102, the target position calculation unit 1003, and the reference point switching judgment unit 1507 (step S1000), and determines whether the judgment results indicate that the traveling direction state has switched (step S1010).

[0119] If the determination result in step S1010 is YES, the difference between the position of the reference point acquired from the self-position calculation unit 102 and the target position acquired from the target position calculation unit 1003 is calculated (step S1020), and it is determined whether the difference in position is equal to or less than a predetermined threshold value (step S1030). The threshold value is set to a value such as 1 m, for example. However, a table of correction distances for differences between the position of the reference point and the target position depending on other features may be prepared in advance, and the threshold value may be determined based on this table.

[0120] If the determination result in step S1030 is NO, a control command for the brake 14 is output to the hydraulic circuit 40 to control the valve to supply hydraulic oil so that the brake shoes clamp the brake disc (step S1040), and the process ends. The amount of clamping of the brake disc by the brake shoes is set to, for example, about half the amount of depression of the brake pedal 23.

[0121] If the determination result in step S1010 is NO or if the determination result in step S1030 is YES, a control command is not output to the brake 14 (step S1050), and the process ends.

[0122] The other configurations are the same as those of the first to fourth embodiments.

[0123] The present embodiment configured as above can also achieve the same effects as the first to fourth embodiments.

[0124] Furthermore, when moving forward, the target trajectory can be tracked using the center of the bucket 7 in the left-right direction as the reference point for its own position, and if the reference point changes when switched and the error from the target trajectory becomes large, the wheel loader can travel with the braking force of the brakes 14 applied until the error can be absorbed, so sudden movements of the wheel loader 1 due to changes in the reference point when switching between forward and backward can be suppressed, making it possible to more reliably improve the accuracy of tracking the target route and suppress serpentine travel.

[0125] <Additional Notes> The present invention is not limited to the above-described embodiments, and includes various modifications and combinations within the scope of the gist thereof. Furthermore, the present invention is not limited to those including all of the configurations described in the above-described embodiments, and includes those in which some of the configurations are omitted. Furthermore, the above-described configurations, functions, etc. may be realized in part or in whole by designing them as, for example, integrated circuits. Furthermore, the above-described configurations, functions, etc. may be realized in software by a processor interpreting and executing a program that realizes each function. [Explanation of symbols]

[0126] 1...wheel loader, 2...front frame, 3...rear frame, 4...cab, 5...front wheel, 6...rear wheel, 7...bucket, 8...lift arm, 9...center pin, 10...steering cylinder, 11...engine, 12...torque converter, 13...transmission, 14...brake, 15...hydraulic pump, 16...drive shaft, 17...axle shaft, 20...operating device, 21...accelerator pedal, 22...forward / reverse command switch, 23...brake pedal, 24...steering wheel, 30...control device, 31...engine controller, 32...transmission controller, 33...vehicle controller, 34 , 34A, 34B, 34C, 34D...Automatic driving controller, 40...Hydraulic circuit, 50...Self-position sensor, 51...Vehicle information acquisition sensor, 100...Straight line, 101...Reference point correction amount calculation unit, 102...Self-position calculation unit, 103...Target trajectory setting unit, 104...Steering control command calculation unit, 501...Reference point correction amount calculation unit, 505...Reference point switching unit, 805...Reference point switching unit, 1003...Target position calculation unit, 1005...Reference point switching unit, 1006...Path planning setting unit, 1007...Reference point switching determination unit, 1501...Reference point correction amount calculation unit, 1506...Path planning setting unit, 1507...Reference point switching determination unit, 1508...Speed ​​control command calculation unit

Claims

1. An articulated vehicle comprising a front frame having a pair of left and right wheels, and a rear frame connected to the front frame so as to be rotatable in the left and right direction and having a pair of left and right wheels, a self-position sensor for detecting a position at a work site; a control device for controlling the operation of the articulated vehicle; The control device a reference point for the articulated vehicle is set on a straight line passing through the center of the left and right axles of the wheels of the frame of the front frame or the rear frame that is closer to the traveling direction than the axles, in the forward and backward direction, perpendicular to the axles; calculating a position of the reference point in the work site based on the detection result of the self-position sensor; an articulated vehicle, characterized in that a steering control amount, which is the amount of bending of the front frame relative to the rear frame, is calculated based on a predetermined target trajectory as a traveling trajectory of the articulated vehicle and the position of the reference point at the work site.

2. 2. The articulated vehicle of claim 1, the control device calculates the steering control amount so that the distance between the left-right center of the wheel axle of the frame closest to the direction of travel, of the front frame or the rear frame, and the target trajectory is equal to or less than the distance between the center of the wheel axle of the frame opposite to the direction of travel and the target trajectory.

3. 2. The articulated vehicle of claim 1, a forward / reverse switch for indicating the direction of travel of the articulated vehicle; The control device sets the reference point of the articulated vehicle in accordance with the direction of travel indicated by the forward / reverse switch.

4. 2. The articulated vehicle of claim 1, Further provided is a vehicle body information acquisition sensor that detects the direction of acceleration, The control device sets the reference point of the articulated vehicle in accordance with the direction of travel of the articulated vehicle determined based on the detection results of a vehicle body information acquisition sensor.

5. 3. The articulated vehicle according to claim 2, The control device calculating a target position at the work site from a route plan that defines a predetermined travel route for the articulated vehicle at the work site and the position of the reference point at the work site; an articulated vehicle having a reference point set in accordance with a direction of travel of the articulated vehicle determined based on a position of the reference point at the work site and the target position;

6. 6. The articulated vehicle according to claim 5, The articulated vehicle is characterized in that, when the reference point is changed, the control device switches the path plan depending on the position of the reference point on the articulated vehicle.

7. 6. The articulated vehicle according to claim 5, the control device calculates a speed control amount, which is a target traveling speed of the articulated vehicle at the work site, so that when the reference point is changed, the distance between the target position and the position of the reference point at the work site is equal to or less than the distance between the target position and the position of the reference point at the work site before the reference point is changed.

8. 3. The articulated vehicle according to claim 2, a pair of lift arms supported on the front frame at positions spaced apart in the width direction so as to be able to rise and fall and extending forward; a bucket tiltably supported on the front ends of the pair of lift arms, The control device When the front frame side is in the traveling direction, the reference point of the articulated vehicle is set between the axle of the wheel of the front frame and the tip of the bucket; An articulated vehicle characterized in that, when the rear frame side is in the direction of travel, the reference point of the articulated vehicle is set between the axle of the wheel of the rear frame and the rear end of the rear frame.

Images