Work vehicle control apparatus and work vehicle control method

Abstract

To suppress a tolerance between an operational turning radius and a target turning radius in turning.SOLUTION: A control apparatus specifies a relationship between a target turning radius and a speed ratio of a pair of crawlers based on a speed ratio of the pair of crawlers at a first point and a turning radius of a work vehicle resulting from a control following the speed ratio. The control apparatus determines a speed ratio of the pair of crawlers from a target turning radius in a second point based on the specified relationship.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present disclosure relates to a control device for a work vehicle and a control method for a work vehicle. [Background technology]

[0002] There are known work vehicles whose traveling gear is composed of a pair of crawlers. Such work vehicles change their direction of travel by varying the speed ratio of the pair of crawlers. The target terrain for construction is sometimes expressed as a shape combining arcs and straight lines. In order to carry out construction along such target terrain, it is necessary to move the work vehicle along the target terrain. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-157259 Summary of the Invention [Problem to be solved by the invention]

[0004] The turning radius of a work vehicle is geometrically determined from the speed ratio of a pair of crawlers and the gauge width (the distance between the left and right tracks). However, in reality, the surface condition of the road on which the vehicle is traveling and the effects of slippage can cause a discrepancy between the target turning radius and the actual turning radius, so a control method that determines the turning radius geometrically does not provide high path tracking performance. An object of the present disclosure is to provide a control device for a work vehicle and a control method for a work vehicle that can reduce errors from a target turning radius during turning. [Means for solving the problem]

[0005] According to one aspect of the present invention, a control device for a work vehicle is a control device for a work vehicle having a pair of crawlers that operate independently of each other, and identifies a relationship between a target turning radius and the speed parameters of the pair of crawlers based on speed parameters of the pair of crawlers at a first point in time and a turning radius of the work vehicle related to the result of control in accordance with the speed parameters, and determines the speed parameters of the pair of crawlers from the target turning radius at a second point in time based on the identified relationship. [Effects of the Invention]

[0006] According to the above aspect, the control device for the work vehicle can reduce the error from the target turning radius during turning. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a side view of a work vehicle according to a first embodiment. [Figure 2] 1 is a schematic diagram showing a power system of a work vehicle according to a first embodiment. [Figure 3] 1 is a diagram showing the configuration of a measurement system and a control device of a work vehicle according to a first embodiment. [Figure 4] FIG. 4 is a diagram illustrating an example of a rotation command table according to the first embodiment. [Figure 5] FIG. 4 is a diagram illustrating a method for calculating a turn command ratio in the first embodiment. [Figure 6] 4 is an example of a correction function according to the first embodiment. [Figure 7] 10 is an example of a corrected turning command table according to the first embodiment. [Figure 8] 4 is a flowchart illustrating automatic steering control according to the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] First Embodiment Hereinafter, the embodiments will be described in detail with reference to the drawings. FIG. 1 is a side view of a work vehicle according to a first embodiment. The work vehicle 100 according to the first embodiment is, for example, a bulldozer. The work vehicle 100 includes a vehicle body 110, a traveling device 120, a work implement 130, and a driver's cab 140.

[0009] The traveling device 120 is provided on the bottom of the vehicle body 110. The traveling device 120 has a pair of crawlers 121 and sprockets 122. The pair of crawlers 121 are provided on the left and right sides of the vehicle body 110, respectively, and operate independently of each other. The crawlers 121 are rotated by the drive of the sprockets 122, causing the work vehicle 100 to travel.

[0010] The work machine 130 is used to excavate and transport excavation targets such as earth and sand. The work machine 130 includes a lift frame 131, a blade 132, and a blade lift cylinder 133. The blade 132 is disposed in front of the vehicle body 110.

[0011] The base end of the lift frame 131 is attached to the side of the vehicle body 110 via a pin extending in the vehicle width direction. The tip end of the lift frame 131 is attached to the back surface of the blade 132 via a ball joint. This supports the blade 132 so that it can move up and down relative to the vehicle body 110. A cutting edge is provided at the lower end of the blade 132. The blade lift cylinder 133 is a hydraulic cylinder. The base end of the blade lift cylinder 133 is attached to the side of the vehicle body 110. The tip end of the blade lift cylinder 133 is attached to the lift frame 131. The blade lift cylinder 133 extends and retracts using hydraulic oil, driving the lift frame 131 and the blade 132 in the raising or lowering direction.

[0012] The operator's cab 140 is a space where an operator rides and operates the work vehicle 100. The operator's cab 140 is provided on top of the vehicle body 110. Inside the operator's cab 140, a console and operating devices are provided.

[0013] An operation panel, gauges, and switches are attached to the console, and the operator can check the status of the work vehicle 100 by visually checking the console. The operation device receives from the operator operations of the pair of crawlers 121 and the blade 132. The operation device is composed of levers and pedals.

[0014] 《Power system》 FIG. 2 is a schematic diagram showing a power system of the work vehicle according to the first embodiment. The work vehicle 100 is equipped with an engine 210, a PTO 220 (Power Take Off), a pair of HSTs 230 (Hydro Static Transmissions), a hydraulic pump 250, and a proportional control valve 260.

[0015] The engine 210 is, for example, a diesel engine. The PTO 220 transmits a portion of the driving force of the engine 210 to the hydraulic pump 250. In other words, the PTO 220 distributes the driving force of the engine 210 to the HST 230 and the hydraulic pump 250. The HST 230 changes the speed of the driving force input to the input shaft and outputs it from the output shaft. The HST 230 includes a hydraulic pump that is driven by the rotation of the input shaft and a hydraulic motor that rotates the output shaft. The HST 230 controls the rotation speed of the output shaft by controlling the discharge flow rate of the hydraulic pump. The input shaft of the HST 230 is connected to the PTO 220, and the output shaft is connected to the sprocket 122. In other words, the HST 230 transmits the driving force of the engine 210 distributed by the PTO 220 to the sprocket 122. The output shafts of the pair of HSTs 230 are connected to the left sprocket 122 and the right sprocket 122, respectively. The hydraulic pump 250 is driven by the driving force from the engine 210. The hydraulic oil discharged from the hydraulic pump 250 is supplied to the blade lift cylinder 133 via a proportional control valve 260. The proportional control valve 260 controls the flow rate of the hydraulic oil discharged from the hydraulic pump 250. In addition to the proportional control valve 260, the hydraulic pump 250 may supply the hydraulic oil to other destinations such as a steering clutch (not shown).

[0016] 3 is a diagram showing the configuration of a measurement system and control device of work vehicle 100 according to the first embodiment. The measurement system of work vehicle 100 acquires vehicle body data that represents the state of work vehicle 100. Work vehicle 100 is equipped with an IMU 310 and a GNSS sensor 320.

[0017] The IMU 310 measures acceleration and angular acceleration with respect to each axis of the vehicle body coordinate system, which has its origin at the center of the running device 120 and is represented by the X axis extending in the longitudinal direction of the vehicle body, the Y axis extending in the lateral direction of the vehicle body, and the Z axis extending in the vertical direction of the vehicle body. The GNSS sensor 320 measures the position and orientation of the vehicle body 110 in the global coordinate system based on signals from GNSS satellites.

[0018] Control device The work vehicle 100 is equipped with a control device 400 for controlling the work vehicle 100 . The control device 400 outputs control signals to the fuel injection device of the engine 210, the HST 230, and the proportional control valve 260 in accordance with the amount of operation of the operating device in the cab 140. The control device 400 also measures the position of the work vehicle 100 based on measurement data from the measurement system and displays it on the console. The control device 400 may autonomously control the power system based on the position of the work vehicle 100 measured based on the measurement data from the measurement system.

[0019] The control device 400 is a computer that includes a processor 410 , a main memory 430 , a storage 450 , and an interface 470 .

[0020] Storage 450 is a non-transitory tangible storage medium. Examples of storage 450 include a magnetic disk, a magneto-optical disk, and a semiconductor memory. Storage 450 may be an internal medium directly connected to the bus of control device 400, or an external medium connected to control device 400 via interface 470 or a communication line. Storage 450 stores a program for controlling work vehicle 100. Storage 450 stores map data 452 of the construction site. Map data 452 includes a route that work vehicle 100 should travel. The route is represented by a combination of straight lines and arcs.

[0021] FIG. 4 is a diagram showing an example of a turning command table 451 according to the first embodiment. The storage 450 stores the turning command table 451, which has been created in advance through experiments or the like and indicates the relationship between the speed ratio of the pair of crawlers 121 and the turning radius. The speed ratio of the pair of crawlers 121 is the ratio of the speed of the crawler of the pair that is closer to the turning center to the speed of the crawler of the pair that is farther from the turning center. The speed ratio of the pair of crawlers 121 when the work vehicle 100 moves straight is 1. In the turning command table 451, the smaller the turning radius is, the smaller the speed ratio of the pair of crawlers 121 is, and the larger the turning radius is, the closer the speed ratio of the pair of crawlers 121 is to 1. In the turning command table 451, the minimum value of the crawlers 121 may be 0 or -1. When the speed ratio of the pair of crawlers 121 is 0, the crawler closer to the turning center is stopped. When the speed ratio of the pair of crawlers 121 is 0, the crawler closer to the turning center is stopped. In this case, the turning radius is equal to the gauge width. When the speed ratio of a pair of crawlers 121 is a negative number, the crawler closer to the turning center rotates in the opposite direction to the crawler farther from the turning center. In this case, the turning radius is 0. The turning command table 451 may be prepared for each speed step.

[0022] In other embodiments, the control device 400 may include a custom LSI (Large Scale Integrated Circuit) such as a PLD (Programmable Logic Device) in addition to or instead of the above configuration. Examples of PLDs include PAL (Programmable Array Logic), GAL (Generic Array Logic), CPLD (Complex Programmable Logic Device), and FPGA (Field Programmable Gate Array). In this case, some or all of the functions implemented by the processor 410 may be implemented by the integrated circuit.

[0023] By executing a program, the processor 410 is provided with an instruction input unit 411, a measurement data acquisition unit 412, a target turning radius determination unit 413, an actual turning radius calculation unit 414, a table correction unit 415, a command generation unit 416, and an output unit 417. Measurement data from the measurement system is input to the processor 410 via an interface 470.

[0024] The instruction input unit 411 receives operation signals for the crawler 121 and the blade 132 from the operation device. The instruction input unit 411 also receives automatic steering instructions from the console. The measurement data acquisition unit 412 acquires measurement data from the IMU 310 and the GNSS sensor 320.

[0025] When performing automatic steering, the target turning radius determination unit 413 identifies a route along which the work vehicle 100 should travel, based on the map data 452 and the current position indicated by the measurement data of the GNSS sensor 320. The target turning radius determination unit 413 determines a target turning radius for the work vehicle 100 to travel along the identified route.

[0026] The command generation unit 416 uses the turning command table 451 to identify a speed ratio that corresponds to the target turning radius determined by the target turning radius determination unit 413. The command generation unit 416 generates pump displacement commands for the pair of HSTs 230 based on the identified speed ratio. The command generation unit 416 records the identified speed ratio in the main memory 430 in association with a time. The output unit 417 outputs the pump displacement command generated by the command generation unit 416 to the HST 230 .

[0027] The actual turning radius calculation unit 414 calculates the actual turning radius of the work vehicle 100 based on the measurement data of the IMU 310 and the GNSS sensor 320 acquired by the measurement data acquisition unit 412. For example, the actual turning radius calculation unit 414 calculates the speed of the pair of crawlers 121 of the work vehicle 100 from the three-dimensional acceleration measured by the IMU 310 and the speed measured by the GNSS sensor 320. The actual turning radius calculation unit 414 calculates the turning radius by dividing the average speed of the pair of crawlers by the difference between the speeds of the pair of crawlers and multiplying the result by the gauge width of the crawlers. Furthermore, for example, the actual turning radius calculation unit 414 identifies the trajectory of the work vehicle 100 from changes in the position and direction of the work vehicle 100 and the rotation angle in the yaw direction of the IMU 310. The actual turning radius calculation unit 414 identifies the intersection of multiple normal lines of the trajectory as the turning center. The actual turning radius calculation unit 414 may also determine the distance between the turning center and the work vehicle 100 as the turning radius.

[0028] The table correction unit 415 calculates the ratio (turning command ratio) between the speed ratio in the turning command table 451 for realizing the turning radius and the actual speed ratio based on the speed ratio recorded in the main memory 430 and the actual turning radius of the work vehicle 100 traveling in accordance with that speed ratio, and corrects the turning command table 451.

[0029] 5 is a diagram showing a method for calculating a turning command ratio in the first embodiment. The table correction unit 415 identifies the speed ratio corresponding to the actual turning radius of the work vehicle 100 recorded in the main memory 430 from the turning command table 451. The table correction unit 415 obtains the ratio between the speed ratio in the turning command table 451 and the actual speed ratio recorded in the main memory 430 as the turning command ratio.

[0030] FIG. 6 is an example of a correction function according to the first embodiment. The table correction unit 415 generates a correction function representing a correction coefficient for each turning radius from the turning command ratio and the turning radius. The correction function is a linear function in which the correction coefficient decreases as the turning radius decreases. The correction function passes through points where the correction coefficient is 1 for turning radii larger than those expected to be used in controlling the work vehicle 100. In other words, the value range of the actual correction function is between 0 and 1. The table correction unit 415 determines the slope of the correction function so that it passes through the points representing the identified turning command ratio and turning radius. FIG. 7 is an example of a corrected turning command table according to the first embodiment. The table correction unit 415 corrects the speed ratios in the turning command table 451 by multiplying the speed ratios corresponding to each turning radius in the turning command table 451 by the correction coefficient identified by the correction function.

[0031] <<Automatic steering method>> When the operator of the work vehicle 100 operates the console and inputs a command to start automatic steering, the control device 400 starts automatic steering control. The control device 400 repeatedly executes the automatic steering control described below for each control cycle.

[0032] FIG. 8 is a flowchart showing the automatic steering control according to the first embodiment. The measurement data acquisition unit 412 acquires measurement data from the IMU 310 and the GNSS sensor 320 (step S1). The target turning radius determination unit 413 identifies a route along which the work vehicle 100 should travel, based on the map data 452 in the storage 450 and the current position indicated by the measurement data acquired by the GNSS sensor 320 in step S1 (step S2). The target turning radius determination unit 413 determines a target turning radius for the work vehicle 100 to travel along the identified route (step S3). For example, if the current position is located on the route, the target turning radius determination unit 413 determines the radius of the route as the target turning radius. If the current position is not located on the route, the target turning radius determination unit 413 calculates the shortest distance between the current position and the route, and determines the target turning radius for reaching the route by PID control or the like based on the deviation.

[0033] The actual turning radius calculation unit 414 calculates the actual turning radius of the work vehicle 100 based on the measurement data acquired in step S1 (step S4). The table correction unit 415 determines whether the current step is immediately after the start of automatic steering (step S5). If control by automatic steering has already started, the speed ratio determined by the command generation unit 416 is recorded in the main memory 430. If the current step is immediately after control by automatic steering has started, the speed ratio determined by the command generation unit 416 is not recorded in the main memory 430.

[0034] If the current step is immediately after the start of automatic steering (step S5: YES), the table correction unit 415 does not correct the turning command table 451. The command generation unit 416 uses the turning command table 451 recorded in the storage 450 to determine a speed ratio for achieving the target turning radius determined in step S3 (step S6).

[0035] If the current step is not immediately after the start of automatic steering (step S5: NO), the table corrector 415 identifies the speed ratio corresponding to the actual turning radius of the work vehicle 100 calculated in step S4 from the turning command table 451 (step S7). In other words, the table corrector 415 identifies the speed ratio corresponding to the actual turning radius obtained by the previous automatic steering control. The table corrector 415 obtains the ratio between the speed ratio in the turning command table 451 and the actual speed ratio recorded in the main memory 430 as the turning command ratio (step S8).

[0036] Next, table corrector 415 specifies a correction function that passes through the point indicated by the turning command ratio calculated in step S8 and the actual turning radius calculated in step S4 (step S9). Table corrector 415 corrects the speed ratio of turning command table 451 by multiplying the speed ratio corresponding to each turning radius in turning command table 451 by the correction coefficient specified by the correction function calculated in step S9 (step S10). Command generator 416 determines the speed ratio for achieving the target turning radius determined in step S3 using turning command table 451 corrected in step S9 (step S11).

[0037] The command generation unit 416 generates a pump displacement command for the pair of HSTs 230 based on the identified speed ratio (step S12). The command generation unit 416 associates the identified speed ratio with time and records it in the main memory 430 (step S13). The output unit 417 outputs the pump displacement command generated in step S12 to the HST 230 (step S14). This causes the pair of crawlers 121 to rotate and the work vehicle 100 to travel.

[0038] The control device 400 according to the first embodiment causes the work vehicle 100 to travel along a route indicated by the map data 452. At this time, the control device 400 may also automatically control the height of the blade 132 in accordance with the topography indicated by the map data 452.

[0039] Actions and Effects In this way, the control device 400 according to the first embodiment specifies a turning command table 451 indicating the relationship between the target turning radius and the speed ratio of the pair of crawlers 121, based on the speed ratio of the pair of crawlers 121 at a first point in time (the point in time of the previous automatic steering control) and the turning radius of the work vehicle 100 related to the results of control performed in accordance with that speed ratio. The control device 400 determines the speed ratio of the pair of crawlers 121 from the target turning radius at a second point in time, based on the specified turning command table 451. This allows the control device 400 to determine the speed ratio of the crawlers 121 for achieving the target turning radius, in accordance with the results of actual turning control of the work vehicle 100 at the work site. Therefore, the control device 400 can reduce errors from the target turning radius during turning.

[0040] The control device 400 according to the first embodiment corrects a pre-calculated turning command table 451 based on the speed ratio of the pair of crawlers 121 at a first point in time and the turning radius of the work vehicle 100 resulting from control according to that speed ratio. This allows the control device 400 to convert the relationship between a certain speed ratio and turning radius into a relationship between an arbitrary turning radius and speed ratio. Therefore, the control device 400 can reduce the error between the actual turning radius and the target turning radius for an arbitrary target turning radius. Note that the control device 400 according to other embodiments may generate a new turning command table 451 from pairs of speed ratios and turning radii obtained at a construction site, rather than correcting a previously prepared turning command table 451.

[0041] Other Embodiments Although one embodiment has been described in detail above with reference to the drawings, the specific configuration is not limited to the above, and various design modifications are possible. That is, in other embodiments, the order of the above-described processes may be changed as appropriate. Furthermore, some processes may be executed in parallel. The control device 400 according to the above-described embodiment may be configured by a single computer, or the configuration of the control device 400 may be divided among multiple computers that cooperate with each other to function as the control device 400. In this case, some of the computers that make up the control device 400 may be mounted inside the work vehicle, and other computers may be provided outside the work vehicle.

[0042] The pair of crawlers 121 of the work vehicle 100 according to the embodiment described above are driven by a pair of HSTs 230, but this is not limiting. For example, the pair of crawlers 121 according to another embodiment may be driven by a pair of electric motors. In this case, the control device 400 can realize the speed ratio of the pair of crawlers 121 by a current command that indicates the amount of current to the pair of electric motors. Also, for example, the pair of crawlers 121 according to another embodiment may distribute the power of a single power source to the pair of crawlers 121 by a differential device. In this case, the control device 400 can realize the speed ratio of the pair of crawlers 121 by a command that indicates the rotation ratio of the differential device.

[0043] The control device 400 according to the embodiment described above corrects the turning command table 451 in accordance with the correction function shown in Fig. 6, but is not limited to this. For example, the control device 400 according to another embodiment may correct the turning command table 451 by so-called PID control.

[0044] The control device 400 according to the embodiment described above corrects the turning command based on the speed ratio of the pair of crawlers 121, but this is not limited to this. The control device 400 according to other embodiments may correct the turning command in accordance with a speed parameter other than the speed ratio. For example, the control device 400 according to other embodiments may control the pair of HSTs 230 using a combination of the turning radius and the central speed of the traveling device 120. In this case, the control device 400 can correct the turning command by multiplying the turning radius as a command value by the ratio between the target turning radius and the actual turning radius. [Explanation of symbols]

[0045] 100...Work vehicle 110...Body 120...Traveling device 121...Crawler 122...Sprocket 130...Work machine 131...Lift frame 132...Blade 133...Blade lift cylinder 140...Operator's cab 210...Engine 220...PTO 230...HST 250...Hydraulic pump 260...Proportional control valve 310...IMU 320...GNSS sensor 400...Control device 410...Processor 411...Instruction input unit 412...Measurement data acquisition unit 413...Target turning radius determination unit 414...Actual turning radius calculation unit 415...Table correction unit 416...Command generation unit 417...Output unit 430...Main memory 450...Storage 451...Turning command table 452...Map data 470...Interface

Claims

1. A control device for a work vehicle equipped with a pair of crawlers that operate independently of each other, specifying a relationship between a target turning radius and the speed parameters of the pair of crawlers based on speed parameters of the pair of crawlers at a first point in time and a turning radius of the work vehicle related to a result of control in accordance with the speed parameters; determining speed parameters of the pair of crawlers from a target turning radius at a second time point based on the identified relationship; Control device for work vehicle.

2. The speed parameter of the pair of crawlers is a speed ratio of the pair of crawlers. The control device for a work vehicle according to claim 1 .

3. a relationship between the target turning radius and a speed parameter of the pair of crawlers is stored in advance; correcting the relationship based on speed parameters of the pair of crawlers at the first time point and a turning radius of the work vehicle related to a result of control in accordance with the speed parameters; determining speed parameters of the pair of crawlers from a target turning radius at a second time point based on the corrected relationship; The control device for a work vehicle according to claim 1 .

4. determining a correction function for determining a correction coefficient for the speed parameter for each turning radius from the speed parameters of the pair of crawlers at the first time point and a turning radius of the work vehicle related to a result of control in accordance with the speed parameters; correcting the relationship based on the correction function; The control device for a work vehicle according to claim 2.

5. A control method for a work vehicle equipped with a pair of crawlers that operate independently of each other, comprising: The control device for the work vehicle, specifying a relationship between a target turning radius and the speed parameters of the pair of crawlers based on speed parameters of the pair of crawlers at a first point in time and a turning radius of the work vehicle related to a result of control in accordance with the speed parameters; determining speed parameters of the pair of crawlers from a target turning radius at a second time point based on the identified relationship; A method for controlling a work vehicle.

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