Working machine and method for controlling the working machine

Abstract

The control point, which is located away from the vehicle's centerline, is made to move along the target path. [Solution] The control device determines multiple target points from the target path based on the positional relationship between a control point located away from the vehicle's centerline and a control center located on the vehicle's centerline. Based on the working machine's travel model, the control device identifies the deviation between the estimated state of the vehicle at the control point and the multiple target points per unit time as the working machine moves. The control device determines the amount of manipulation required for the control point to move along the target path so that the deviation between the estimated state and the multiple target points per unit time is minimized.

Description

[Technical Field]

[0001] This disclosure relates to a work machine and a method for controlling a work machine. [Background technology]

[0002] Patent Document 1 discloses technology for autonomous driving of a work machine that runs on tires with the front wheels as steering wheels. Patent Document 1 also discloses technology for controlling the driving of a work machine using model predictive control. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Patent No. 7386757 [Overview of the project] [Problems that the invention aims to solve]

[0004] Incidentally, when performing work with a work implement such as a blade attached to the front or rear of a vehicle, automatic control requires that the cutting edge of the work implement move along the target path in order to perform work along that path. However, since the control points of the cutting edge of the work implement are far from the control center of the vehicle body, a control center-based model such as the one shown in Patent Document 1 cannot make the control points of the work implement move along the target path. The purpose of this disclosure is to provide a work machine and a method for controlling the work machine that can move a control point located away from the centerline of the vehicle body along a target path. [Means for solving the problem]

[0005] According to one aspect of the present invention, the work machine comprises a vehicle body, a traveling device attached to the vehicle body, and a control device that determines an amount of operation for the traveling device to move a control point away from the centerline of the vehicle body along a target path, wherein the control device determines a plurality of target points from the target path based on the positional relationship between the control point and a control center located on the centerline of the vehicle body, identifies the deviation between the estimated state of the vehicle body of the control point and the plurality of target points per unit time as the work machine moves, based on a travel model of the work machine, and determines the amount of operation so that the deviation between the estimated state and the plurality of target points per unit time becomes small. [Effects of the Invention]

[0006] According to the above embodiment, a control point located away from the centerline of the vehicle body can be made to travel along a target path. [Brief explanation of the drawing]

[0007] [Figure 1] This is a side view of a work vehicle according to the first embodiment. [Figure 2] This is a schematic diagram showing the power system of a work vehicle according to the first embodiment. [Figure 3] This diagram shows the configuration of the measurement system and control device of the work vehicle according to the first embodiment. [Figure 4] This figure shows an example of a turning command table according to the first embodiment. [Figure 5] This is a flowchart showing the automatic steering control according to the first embodiment. [Figure 6] This figure shows the relationship between the turning radius of the control point and the turning radius of the ground contact center of the traveling device according to the first embodiment. [Modes for carrying out the invention]

[0008] <First Embodiment> The embodiments will be described in detail below with reference to the drawings. Figure 1 is a side view of a work vehicle according to the first embodiment. The work vehicle 100 according to the first embodiment is, for example, a bulldozer. The work vehicle 100 according to other embodiments may be other work vehicles such as a hydraulic excavator, a wheel loader, or a dump truck. The work vehicle 100 comprises a body 110, a running gear 120, a work machine 130, and a driver's cab 140.

[0009] The running gear 120 is installed on the underside of the vehicle body 110. The running gear 120 comprises a pair of crawlers 121 and sprockets 122. The pair of crawlers 121 are installed on the left and right sides of the vehicle body 110, respectively, and operate independently of each other. The crawlers 121 rotate when driven by the sprockets 122, causing the work vehicle 100 to move.

[0010] The work machine 130 is used for excavating and transporting materials such as soil and sand. The work machine 130 comprises a lift frame 131, a blade 132, and a blade lift cylinder 133. The blade 132 is positioned 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 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 vertically 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 of the blade lift cylinder 133 is attached to the lift frame 131. The blade lift cylinder 133 expands and contracts due to hydraulic fluid, driving the lift frame 131 and the blade 132 upward or downward.

[0012] The driver's cab 140 is a space where the operator sits and operates the work vehicle 100. The driver's cab 140 is located on top of the vehicle body 110. A console and control devices are installed inside the driver's cab 140.

[0013] The console will be fitted with a control panel, instruments, and switches. The operator can visually check the status of the work vehicle 100 from the console. The control device receives input from the operator regarding the operation of a pair of crawlers 121 and blades 132. The control device consists of levers and pedals.

[0014] 《Power system》 Figure 2 is a schematic diagram showing the power system of a 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] Engine 210 is, for example, a diesel engine. The PTO 220 transmits a portion of the power from the engine 210 to the hydraulic pump 250. In other words, the PTO 220 distributes the power from the engine 210 to a pair of HSTs 230 and hydraulic pumps 250. The HST230 transmits the driving force input to the input shaft at a variable speed to the output shaft. The HST230 comprises a hydraulic pump driven by the rotation of the input shaft and a hydraulic motor that rotates the output shaft. The HST230 controls the rotational speed of the output shaft by controlling the discharge flow rate of the hydraulic pump. In other embodiments of the HST230, the rotational speed of the output shaft may be controlled by the capacity of the hydraulic motor instead of the discharge flow rate of the hydraulic pump. The input shaft of the HST230 is connected to the PTO220, and the output shaft is connected to the sprocket 122. In other words, the HST230 transmits the driving force of the engine 210 distributed by the PTO220 to the sprocket 122. The output shafts of the pair of HST230s are connected to the left sprocket 122 and the right sprocket 122, respectively. The hydraulic pump 250 is driven by the power from the engine 210. The hydraulic fluid discharged from the hydraulic pump 250 is supplied to the blade lift cylinder 133 via the proportional control valve 260. The proportional control valve 260 controls the flow rate of the hydraulic fluid discharged from the hydraulic pump 250. In addition to the proportional control valve 260, the hydraulic pump 250 may also supply hydraulic fluid to other destinations, such as a steering clutch (not shown).

[0016] Figure 3 shows the configuration of the measurement system and control device of the work vehicle 100 according to the first embodiment. The measurement system of the work vehicle 100 acquires vehicle body data representing the state of the work vehicle 100. The work vehicle 100 is equipped with an IMU 310, a GNSS sensor 320, and a rotation speed sensor 330.

[0017] The IMU310 measures acceleration and angular acceleration for each axis of the vehicle coordinate system, which is represented by the X-axis extending in the longitudinal direction of the vehicle, the Y-axis extending in the lateral direction of the vehicle, and the Z-axis extending in the vertical direction of the vehicle, with the origin being the center of contact with the ground of the running gear 120. The GNSS sensor 320 measures the position, speed, and direction of the vehicle 110 in the global coordinate system based on signals from GNSS satellites. The rotation speed sensor 330 measures the rotation speed of the left and right sprockets 122.

[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 injector of the engine 210, the HST 230, and the proportional control valve 260 according to the amount of operation of the control device by the operator. The control device 400 also measures the position of the work vehicle 100 based on the measurement data of 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 of the measurement system. The control device 400 according to the first embodiment has two control modes: a manual driving mode and an automatic driving mode. The manual driving mode is a control mode in which the driving and steering of the work vehicle 100 are controlled based on the amount of operation of the operating device. The automatic driving mode is a control mode in which the control device 400 calculates the amount of operation and controls the driving and steering of the work vehicle 100. When the control device 400 controls the work vehicle 100 in automatic driving mode, the control device 400 determines the amount of operation from the information of the construction path, which represents the outline of the area to be worked on by the blade 132, and the position of the control point of the cutting edge of the blade 132, so that the control point coincides with the construction path. The control device 400 calculates the amount of operation from at least the direction of travel of the vehicle and the positional relationship between the construction path and the work vehicle 100 (relationship between the position of the construction path and the position of the work vehicle 100, the direction of the construction path as seen from the work vehicle 100, etc.).

[0019] The control unit 400 is a computer equipped with a processor 410, main memory 430, storage 450, and interface 470.

[0020] The storage 450 is a tangible, non-temporary storage medium. Examples of the storage 450 include magnetic disks, magneto-optical disks, and semiconductor memory. The storage 450 may be an internal medium directly connected to the bus of the control device 400, or an external medium connected to the control device 400 via the interface 470 or a communication line. The storage 450 stores a program for controlling the work vehicle 100. The storage 450 stores map data 452 of the construction site. The map data 452 includes a construction route that represents the outline of the area to be constructed with the blade 132. The construction route is represented by a combination of straight lines and arcs. The work vehicle 100 can properly construct the construction site by driving so that the right or left end of the cutting edge of the blade 132 follows the construction route.

[0021] Figure 4 shows an example of a turning command table 451 according to the first embodiment. The storage 450 stores a turning command table 451 that shows the relationship between the speed ratio of a pair of crawlers 121 and the turning radius, which has been created in advance through experiments, etc. The speed ratio of a pair of crawlers 121 is the ratio of the speed of the crawler closer to the turning center to the speed of the crawler further from the turning center. When the work vehicle 100 is moving in a straight line, the speed ratio of the pair of crawlers 121 is 1. In the turning command table 451, the larger the turning radius, the larger the speed ratio of the pair of crawlers 121 becomes, approaching 1, and the smaller the turning radius, the closer the speed ratio of the pair of crawlers 121 becomes, approaching 0. In the turning command table 451, the minimum value of the speed ratio 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 stops. When the speed ratio of a pair of crawlers 121 is negative, the crawler closer to the turning center rotates in the opposite direction to the crawler further from the turning center. The turning command table 451 may be provided for each speed stage.

[0022] In other embodiments, the control device 400 may include, in addition to or instead of the above configuration, a custom LSI (Large Scale Integrated Circuit) such as a PLD (Programmable Logic Device). 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 realized by the processor 410 may be realized by the integrated circuit.

[0023] The processor 410, by executing a program, includes an instruction input unit 411, a measurement data acquisition unit 412, a model prediction control unit 413, a command generation unit 414, and an output unit 415. Measurement data from the measurement system is input to the processor 410 via the interface 470.

[0024] The instruction input unit 411 receives operation signals for the crawler 121 and blade 132 from the control 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, GNSS sensor 320, and rotation speed sensor 330. From the acquired measurement data, the measurement data acquisition unit 412 determines vehicle parameters such as the position of the tip of the blade 132, the speed of the travel device 120, and the turning curvature. Specifically, the measurement data acquisition unit 412 can calculate the position of the tip of the blade 132 by tilting the known positional relationship of the tip of the work machine 130 with respect to the ground contact center of the travel device 120 according to the direction the work vehicle 100 is facing, and adding it to the position of the ground contact center indicated by the measurement data. The measurement data acquisition unit 412 can calculate the speed of the travel device 120 by taking the average of the measured rotation speeds of the left and right sprockets 122. The measurement data acquisition unit 412 can calculate the turning curvature of the travel device 120 from the ratio of the rotation speeds of the left and right sprockets 122 and the turning command table 451.

[0025] When performing automatic steering, the model prediction control unit 413 determines the turning curvature (target turning curvature) for the tip of the blade 132 to move along the construction path represented by the map data 452, based on the map data 452, the current position and direction indicated by the GNSS sensor 320 measurement data, and the turning curvature of the travel device 120. The model prediction control unit 413 simulates the travel of the work vehicle 100 using the travel model of the work vehicle 100 and performs optimization processing to obtain a travel path that minimizes the discrepancy between the tip of the blade 132 and the construction path.

[0026] The command generation unit 414 uses the turning command table 451 to identify the speed ratio corresponding to the target turning curvature determined by the model prediction control unit 413. Based on the identified speed ratio, the command generation unit 414 generates pump capacity commands for a pair of HST230s. The command generation unit 414 records the identified speed ratio in the main memory 430, associating it with time. The output unit 415 outputs the pump capacity command generated by the command generation unit 414 to the HST 230.

[0027] 《Regarding the Travel Model》 The travel model used for model predictive control is the state Z of the work vehicle 100 at time (i×Δt) i and the turning curvature operation amount u i and is a model for obtaining the state Z of the work vehicle 100 after one unit of time. i+1 The travel model is represented by the following equation (1).

[0028]

Number

[0029] The state Z of the work vehicle 100 i is a vector having the position Z of the control point at time (i×Δt) xi Z yi the azimuth Z that the work vehicle 100 faces θi and the turning curvature Z cvi as elements. That is, the state Z i is represented by the following equation (2).

[0030]

Number

[0031] The coefficient A, coefficient B, and term w of equation (1) i are values determined from the initial state Z0 of the work vehicle 100 and the construction path of the map data 452. The coefficient A is represented by equation (3). The coefficient B is represented by equation (4). The term w i is represented by equation (5).

[0032]

Number

Number

Number

[0033] Time Δt is a fixed time interval short enough that the trigonometric functions can be approximated by a straight line. State Z in equation (5) d i This represents an approximate value of the state at time (i × Δt), and u d i This represents an approximate value of the rotational curvature manipulation amount at time (i × Δt). In the first embodiment, state Z d i The value used is a value corrected to the curvature of the path through which the ground contact center of the traveling device 120 passes. State Z d i The calculation method will be explained later. In the first embodiment, the control device 400 determines an approximate value related to the position of the control point based on the point in the construction path closest to the control point, and determines an approximate value related to the orientation and turning curvature of the work vehicle 100 based on the point in the construction path closest to the ground contact center. When the work vehicle 100 turns, the ground contact center of the running device 120 becomes the point of contact of the turning trajectory. Therefore, by determining the approximate values ​​related to the orientation and turning curvature based on the point in the construction path closest to the ground contact center rather than the point in the construction path closest to the control point, the control device 400 can appropriately control the turning operation. In other words, the control center of the vehicle body in the first embodiment is the ground contact center of the running device 120. In the first embodiment, by giving the function g in the form of equation (6), we can obtain u from equations (4) and (5). d i Since it is canceled out, u d i This can be any value. Note that in other embodiments of the control device 400, instead of using the construction route of the map data 452, the state at any time (i × Δt) is determined from the initial state Z0 using the differential model shown in equation (6), and this is then used to determine the state Z d i It may be used as follows. In this case, the rotational curvature manipulation variable u given to the differential model is the rotational curvature manipulation variable u obtained in the previous calculation. i You may use this. Alternatively, you may set u=0.

[0034] By the way, as shown in equations (3) to (5), coefficient A, coefficient B, and constant term w i This is expressed by the partial derivatives of functions f and g. Functions f and g are functions that constitute the differential model of the work vehicle 100 shown in equation (6) below. The differential model represents the relationship between the state Z of the work vehicle 100 at time (i+Δt), the turning curvature control amount u, and the derivative value Z′ of the state Z of the work vehicle 100.

[0035]

number

[0036] The coefficient V is the travel speed of the work vehicle 100. Constant term V slip x , V slip y These are the x and y components of the lateral slip velocity of the work vehicle 100, which are determined from the inclination of the work vehicle 100. The lateral slip velocity is determined based on the lateral velocity of the running gear 120 (Y-axis direction of the vehicle coordinate system). Offset x off and y off These are the x-component length and the y-component length, respectively, from the ground contact center of the traveling device 120 to the control point on the work machine 130. In other words, offset x off and y off These are the x and y coordinates of the control point in the vehicle body coordinate system with respect to the ground contact center of the work vehicle 100. The coefficient τ is the delay time constant of the running gear 120. Functions f and g are determined in advance to satisfy equation (6) above.

[0037] 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 shown below at control cycles (for example, 100 milliseconds).

[0038] Figure 5 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, GNSS sensor 320, and rotation speed sensor 330 (step S1). From the acquired measurement data, the measurement data acquisition unit 412 determines the position (Z) of the tip (control point) of the blade 132 as a vehicle parameter. x , Z y , x off , y off ), the direction Z of the traveling device 120 θ , rotational curvature Z cv and velocity V, as well as sideslip velocity (V slip x , V slip y ) calculate (step S2).

[0039] The model prediction control unit 413 calculates the delay time t of the automatic steering control from the current time based on the measurement data acquired in step S1 and the vehicle parameters calculated in step S2. w The state Z0 of the work vehicle 100 at a later time (initial time) is determined (step S3). Specifically, the model prediction control unit 413 uses the driving model shown in equation (1) or the differential model shown in equation (6) to determine the delay time t w Determine the vehicle parameters after the time interval t. w If this can be ignored, the state Z0 of the work vehicle 100 at the initial time can be determined without using a driving model.

[0040] Next, the model prediction control unit 413 determines the first target point at the initial time, which is the point in the construction route closest to the control point, based on the map data 452 in the storage 450 and the initial state Z0 of the work vehicle 100 obtained in step S3. ref1 Identify 0 (step S4). The model prediction control unit 413 also identifies the position of the ground contact center of the traveling device 120 at the initial time from the initial state Z0, and based on the map data 452 in storage 450 and the position of the ground contact center, it identifies the second target point Z at the initial time, which is the point in the construction route closest to the ground contact center. ref2 Identify 0 (step S5). The model prediction control unit 413 identifies N+1 first target points Z ref1 0~Z ref1N and N+1 second target points Z ref2 0~Z ref2 N Steps S6 to S8 are repeated until the desired result is obtained, where N is a predetermined number of optimization points.

[0041] The model prediction control unit 413 then uses the last determined first target point Z ref1 i Curvature Z ref1 cvi Using this, the work vehicle 100 moves to the first target point Z ref1 i The unit distance D that the control point advances when traveling along the construction route for a unit time Δt. i Find the value of the unit distance D (Step S6). i This can be calculated using the following equation (7).

[0042]

number

[0043] K in equation (7) ref1 i This represents a multiplier for converting the travel amount V × Δt of the traveling device 120 into the travel amount of the control point. This can be determined as a curvature coefficient representing the ratio of the curvature of the construction path when the control point moves along the construction path to the rotational curvature of the ground contact center of the traveling device 120. Curvature coefficient K ref1 i This is expressed by equation (8).

[0044]

number

[0045] Here, the curvature coefficient K ref1 i Let's explain why it is expressed by equation (8). Figure 6 shows the relationship between the turning radius of the control point and the turning radius of the ground contact center of the traveling device according to the first embodiment. As shown in Figure 6, the length of the line segment L1 connecting the control point and the pivot center is equal to the pivot radius r1 of the control point, i.e., the first target point Z.ref1 i The curvature Z ref1 cvi is the reciprocal of this. Here, as shown in FIG. 6, when a perpendicular line L3 is drawn from the control point toward the line segment L2 connecting the grounding center and the turning center, a right triangle appears with the line segment L1 as the hypotenuse and the perpendicular line L3 as the opposite side. From this, the length of the line segment L2 connecting the grounding center and the turning center, that is, the turning radius r2 of the grounding center, is the sum of the length of the adjacent side of the right triangle and the y-axis component of the positional relationship between the grounding center and the control point, which is y off and. Since the length of the adjacent side of the right triangle is represented by the square root of the sum of the squares of the lengths of the line segment L1 and the perpendicular line L3, the turning radius r2 of the grounding center is represented by Equation (9).

[0046]

Equation

[0047] Therefore, it can be seen that when the traveling device 120 moves with the turning radius r2, the control point moves with the turning radius r1. That is, the curvature coefficient K ref1 i becomes r1 / r2, so substituting r1 = 1 / Z ref1 cvi into Equation (9), Equation (8) can be obtained.

[0048] In step S6 of FIG. 5, when obtaining the unit distance D i the model predictive control unit 413 determines, among the construction path, the point that is a unit distance D ref1 i ahead from the last obtained first target point Z i as the next first target point Z ref1 i+1 (step S7). Also, the model predictive control unit 413 determines, among the construction path, the point that is a unit distance D ref2 i ahead from the last obtained second target point Z i as the next second target point Z ref2 i+1 (step S8).

[0049] By repeating steps S6 to S8, N + 1 first target points Z ref1 0 to Z ref1 N and N + 1 second target points Z ref2 0 to Z ref2 N are specified. Then, based on the N + 1 first target points Z ref1 0 to Z ref1 N and the second target points Z<00001..>0 to Z ref2 N the model predictive control unit 413 specifies N + 1 target states Z tgt 0 to Z tgt N (step S9). In the first embodiment, Z tgt xi (the x - component of the target state Z tgt i ) is set to the x - component of the first target point Z ref1 i , Z tgt yi is set to the y - component of the first target point Z ref1 i , Z tgt θi (the θ - component of the state Z tgt i ) is set to the θ - component of the second target point Z ref2 i , Z tgt θi (the θ - component of the state Z tgt i ) is set to the cv - component of the second target point Z ref2 i .

[0050] At this time, the model predictive control unit 413 corrects the cv - component (curvature) of the target state Z tgt i to the curvature of the path through which the ground contact center of the traveling device 120 passes (corrected curvature Z tgt cvi ) (step S10). Specifically, as shown in the following formula (10), the model predictive control unit 413 multiplies the cv - component of the second target point Z ref2 i by the curvature coefficient K ref2 i to obtain the corrected curvature Ztgt cvi We will find the curvature coefficient K. ref1 i This is expressed by equation (11).

[0051]

number

number

[0052] The curvature coefficient K shown in equation (11) ref2 i The first target point K ref1 i The curvature and the second target point K ref2 i Assuming that the curvature of does not change significantly, K in equation (8) ref1 cvi Second target point K ref2 i Curvature K ref2 cvi This is a substitute for the above. In other embodiments, the model prediction control unit 413 calculates the curvature coefficient K in equation (10). ref2 i Instead, the curvature coefficient K ref1 i Using the corrected curvature Z tgt cvi You may also request this.

[0053] The model prediction control unit 413 has an initial state Z0 and N+1 path states Z tgt 0~Z tgt N Based on this, under equation (1), the N turning curvature manipulated variables u0~u are optimized so that the loss function shown in equation (12) is minimized. N-1 We find this (Step S11). For optimization calculations, for example, quadratic programming can be used.

[0054]

number

[0055] The command generation unit 414 generates N turning curvature manipulation amounts u0~u based on the turning command table 451 obtained in step S13. N-1 Among these, the speed ratio required to achieve the initial turning curvature manipulation amount u0 is determined (step S12). The command generation unit 414 generates pump capacity commands for the pair of HST230 based on the determined speed ratio (step S13). The output unit 415 outputs the pump capacity commands generated in step S15 to the HST230 (step S14). As a result, the pair of crawlers 121 rotate and the work vehicle 100 moves.

[0056] In the first embodiment, the control device 400 causes the work vehicle 100 to travel along the 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 terrain indicated by the map data 452.

[0057] Action / Effect The control device 400 according to the first embodiment determines N+1 target states Z based on the positional relationship between a control center located on the centerline of the vehicle body and a control point located away from the centerline of the vehicle body. tgt The control device 400 in the first embodiment estimates a curvature coefficient representing the ratio of the curvature of the control center to the curvature of the control point, and uses this curvature coefficient to determine the unit distance D for extracting the target point from the construction path and the corrected curvature Z obtained by correcting the curvature of the target point to the curvature of the control center. tgt cvi The control device 400 determines multiple target points at unit distances determined using the curvature coefficient, thereby canceling out the difference between the movement distance of the ground contact center of the running device 120, which is the control center, and the movement distance of the control points, which occurs due to differences in turning radii, and determining an appropriate target point. Furthermore, the control device 400 can use the curvature coefficient to cancel out the difference between the curvature of the ground contact center of the running device 120 and the curvature of the control points, which occurs due to differences in turning radii, and determine an appropriate turning curvature (corrected curvature). Thus, according to the control device 400 of the first embodiment, the work vehicle 100 can be driven so that the control point, which is located away from the centerline of the vehicle body, follows the target path.

[0058] <Other Embodiments> Although one embodiment has been described in detail above with reference to the drawings, the specific configuration is not limited to that described above, and various design changes are possible. In other embodiments, the order of the above-described processes may be changed as appropriate. Also, some processes may be executed in parallel. The control device 400 according to the above embodiment may be composed of a single computer, or the configuration of the control device 400 may be divided among multiple computers, and the multiple computers may cooperate with each other to function as the control device 400. In this case, some of the computers constituting the control device 400 may be mounted inside the work vehicle, while the other computers may be provided outside the work vehicle.

[0059] The pair of crawlers 121 of the work vehicle 100 according to the above embodiment are driven by a pair of HST230s, but are not limited to this. 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 achieve the speed ratio of the pair of crawlers 121 by current commands that instruct the amount of current to the pair of electric motors. Alternatively, 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. In this case, the control device 400 can achieve the speed ratio of the pair of crawlers 121 by commands that instruct the rotation ratio of the differential. Alternatively, for example, the speed of the pair of crawlers 121 according to another embodiment may be controlled by controlling the flow rate of hydraulic fluid with a control valve.

[0060] The work vehicle 100 according to the above embodiment runs on a pair of crawlers 121, but is not limited to this. For example, in another embodiment, the work vehicle 100 may run on wheels. In this case, the control center may be set at the center of the rear axle, or at the center of all four wheels. In either case, the control center is located on the centerline of the vehicle body.

[0061] The control device 400 according to the above embodiment predicts predicted path points by model predictive control using a driving model, but is not limited to this. In other embodiments, the control device 400 may predict predicted path points without using a driving model. [Explanation of symbols]

[0062] 100…Work vehicle 110…Body 120…Running gear 121…Crawler 122…Sprocket 130…Work implement 131…Lift frame 132…Blade 133…Blade lift cylinder 140…Driver's cab 210…Engine 220…PTO 230…HST 250…Hydraulic pump 260…Proportional control valve 310…IMU 320…GNSS sensor 330…Rotation speed sensor 400…Control unit 410…Processor 411…Instruction input unit 412…Measurement data acquisition unit 413…Model prediction control unit 414…Command generation unit 415…Output unit 430…Main memory 450…Storage 451…Swing command table 452…Map data 470…Interface

Claims

1. The car body and, The running gear attached to the vehicle body, A control device that determines the amount of operation of the traveling device so that a control point located away from the centerline of the vehicle body moves along a target path, A work machine equipped with, The control device is Based on the positional relationship between the control point and the control center located on the centerline of the vehicle body, multiple target points are determined from the target path. Based on the travel model of the work machine, the deviation between a plurality of predicted path points representing the estimated state of the vehicle body at each unit time associated with the movement of the work machine and the plurality of target points is identified. The manipulated amount is determined so that the discrepancy between the plurality of predicted path points and the plurality of target points is minimized. A type of machinery used for industrial work.

2. The control device is The curvature coefficient is estimated as the ratio of the curvature of the target path to the rotational curvature of the control center when the control point moves along the target path. The manipulated variable is determined using the aforementioned curvature coefficient. The work machine according to claim 1.

3. The control device is The plurality of target points are determined by extracting target points from the target path for each distance calculated by the product of the speed of the work machine, the unit time, and the coefficient of curvature. The working machine according to claim 2.

4. The control device is For each of the aforementioned target points, a corrected curvature is obtained by multiplying the curvature by the curvature coefficient. The manipulated variable is determined such that the difference between the curvature of the plurality of predicted path points and the corrected curvature of the plurality of target points is minimized. The working machine according to claim 2.

5. The aforementioned driving model has a coefficient or term calculated from the corrected curvature. The work machine according to claim 4.

6. The vehicle body is equipped with a work machine located at the front end, The control point is a point on the work machine. The work machine according to claim 1.

7. The car body and, The running gear attached to the vehicle body, A control device that determines the amount of operation of the traveling device so that a control point located away from the centerline of the vehicle body moves along a target path, A control method for a work machine equipped with, The steps include determining multiple target points from the aforementioned target path, A step of identifying the deviation between a plurality of predicted path points and a plurality of target points, which represent the estimated state of the vehicle body at each unit time associated with the movement of the work machine, based on the travel model of the work machine; The steps include determining the manipulated amount such that the discrepancy between the plurality of predicted path points and the plurality of target points becomes small, and A control method for a work machine having a work machine.

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