Systems and methods for controlling a work machine

Abstract

To accurately detect a position of a work implement in a work machine even if the yaw angle of the work implement changes due to an operation of the work implement.SOLUTION: A system includes a work implement sensor and a controller. The work implement sensor detects roll angle and pitch angle of the work implement. The controller obtains an actual frame length indicating a distance between a first vehicle body connection and a first frame connection. When the work implement is in a first posture, the controller calculates an assumed position of the first frame connection when the yaw angle is assumed to be a predetermined angle, based on the roll angle and pitch angle of the work implement. The controller calculates an assumed frame length indicating a distance between the assumed position of the first frame connection and the first vehicle body connection. The controller calculates the yaw angle of the work implement in the first posture based on the difference between the actual frame length and the assumed frame length. The controller calculates the position of the predetermined portion of the work implement based on the roll angle and pitch angle of the work implement and the yaw angle of the work implement in the first posture.SELECTED DRAWING: Figure 5A

Description

[Technical Field]

[0001] The present invention relates to a system and method for controlling a work machine. [Background technology]

[0002] Some work machines are equipped with a working implement such as a blade. For example, in the work machine disclosed in Patent Document 1, the blade and the vehicle body are connected by left and right lift frames. Left and right pitch / tilt cylinders are connected to the left and right lift frames, respectively. The blade tilts when the left and right pitch / tilt cylinders extend and retract, respectively. The tilting operation is an operation in which the blade tilts left and right so that the height of one of the left and right ends of the blade is different from the height of the other. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-31696 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, the position of a predetermined part of a work machine has been detected by a controller of the work machine for purposes such as controlling the work machine. To this end, the work machine is equipped with a work machine sensor that detects the attitude of the work machine and a frame sensor that detects the attitude of the frame. Each sensor is, for example, an acceleration sensor that detects the roll angle and pitch angle from the acceleration of gravity. When the yaw angle of the work machine relative to the vehicle body is zero degrees, the controller can calculate the position of the predetermined part of the work machine relative to the vehicle body based on the length, roll angle, and pitch angle of the frame, the roll angle and pitch angle of the work machine, and the position of the predetermined part of the work machine.

[0005] However, when the blade tilts, one of the left and right frames swings, causing the left and right frames to differ in height. In this case, the positions of the front ends of the left and right frames are shifted from each other in the fore-and-aft direction. As a result, the yaw angle of the work implement relative to the vehicle body becomes a value other than zero degrees. In this case, it is difficult to accurately detect the position of the work implement relative to the vehicle body using the above-mentioned method.

[0006] On the other hand, with the acceleration sensor described above, the yaw angle of the work implement can be calculated by integrating angular velocity, with the value at startup set to 0. However, the accuracy is not high, and errors become large after prolonged use. Therefore, even when detecting the yaw angle using an acceleration sensor, it is not easy to accurately detect the position of the work implement relative to the vehicle body. An object of the present invention is to accurately detect the position of a specific part of the work implement on a work machine, even if the yaw angle of the work implement changes due to the operation of the work implement. [Means for solving the problem]

[0007] A system according to one aspect of the present invention is a system for controlling a work machine. The work machine includes a vehicle body, a work machine frame, a work machine, a first actuator, and a second actuator. The work machine frame includes a first frame and a second frame. The first frame includes a first vehicle body connection portion connected to the vehicle body. The second frame includes a second vehicle body connection portion connected to the vehicle body. The second frame is positioned spaced apart from the first frame in the left-right direction.

[0008] The work implement includes a first frame connection portion, a second frame connection portion, and a predetermined portion. The first frame connection portion is connected to the first frame. The second frame connection portion is arranged spaced apart from the first frame connection portion in the left-right direction. The second frame connection portion is connected to the second frame. The first actuator moves the first frame relative to the vehicle body. The second actuator moves the second frame relative to the vehicle body. A yaw angle of the work implement relative to the vehicle body when the work implement is in a first posture is different from a yaw angle of the work implement when the work implement is in a second posture. The second posture is different from the first posture.

[0009] The system includes a work machine sensor and a controller. The work machine sensor is attached to the work machine. The work machine sensor detects a roll angle and a pitch angle of the work machine. The controller acquires an actual frame length indicating a distance between a first vehicle-body connection portion and a first frame connection portion. The controller acquires a position of the first vehicle-body connection portion. The controller acquires the roll angle and the pitch angle of the work machine.

[0010] When the work implement is in the first posture, the controller calculates an assumed position of the first frame connection part when the yaw angle is assumed to be a predetermined angle based on the roll angle and pitch angle of the work implement. The controller calculates an assumed frame length indicating the distance between the assumed position of the first frame connection part and the first vehicle body connection part. The controller calculates the yaw angle of the work implement in the first posture based on the difference between the actual frame length and the assumed frame length. The controller calculates the position of a predetermined part of the work implement based on the roll angle and pitch angle of the work implement and the yaw angle of the work implement in the first posture.

[0011] A method according to another aspect of the present invention is a method for controlling a work machine. The work machine includes a vehicle body, a work implement frame, a work implement, a first actuator, and a second actuator. The work implement frame includes a first frame and a second frame. The first frame includes a first vehicle body connection portion connected to the vehicle body. The second frame includes a second vehicle body connection portion connected to the vehicle body. The second frame is positioned spaced apart from the first frame in the left-right direction.

[0012] The work implement includes a first frame connection portion, a second frame connection portion, and a predetermined portion. The first frame connection portion is connected to the first frame. The second frame connection portion is arranged spaced apart from the first frame connection portion in the left-right direction. The second frame connection portion is connected to the second frame. A yaw angle of the work implement relative to the vehicle body when the work implement is in a first position is different from a yaw angle of the work implement when the work implement is in a second position. The second position is different from the first position.

[0013] The method includes detecting the position of the first vehicle body connection portion, detecting the roll angle and pitch angle of the work implement, obtaining an actual frame length indicating the distance between the first vehicle body connection portion and the first frame connection portion, calculating an assumed position of the first frame connection portion when the yaw angle is assumed to be a predetermined angle based on the roll angle and pitch angle of the work implement when the work implement is in a first posture, calculating an assumed frame length indicating the distance between the assumed position of the first frame connection portion and the first vehicle body connection portion, calculating the yaw angle of the work implement in the first posture based on the difference between the actual frame length and the assumed frame length, and calculating the position of a predetermined part of the work implement based on the roll angle and pitch angle of the work implement and the yaw angle of the work implement in the first posture. [Effects of the Invention]

[0014] According to the present invention, the yaw angle when the work implement is in the first posture is calculated from the difference between the assumed frame length when the yaw angle of the work implement is assumed to be a predetermined angle and the actual frame length. As a result, even if the yaw angle of the work implement changes due to the operation of the work implement, the position of the work implement can be detected with high accuracy in the work machine. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a perspective view of a work machine. [Figure 2] FIG. 2 is a perspective view of the working machine and its surrounding structure. [Figure 3] FIG. 2 is a block diagram showing a control system of the work machine. [Figure 4A] FIG. 2 is a top view schematically showing the work machine and the work machine frame in a standard position. [Figure 4B] FIG. 2 is a side view schematically showing the work machine and the work machine frame in a standard position. [Figure 4C] FIG. 2 is a rear view schematically showing the work machine and the work machine frame in a standard position. [Figure 5A] FIG. 2 is a top view schematically showing the work implement and the work implement frame in a tilted position. [Figure 5B]FIG. 2 is a side view schematically showing the work implement and the work implement frame in a tilted position. [Figure 5C] FIG. 2 is a rear view schematically showing the work implement and the work implement frame in a tilted position. [Figure 6] 10 is a flowchart showing a process for calculating the position of a predetermined part of a work machine. [Figure 7] FIG. 3 is a diagram illustrating an example of control of a work machine. DETAILED DESCRIPTION OF THE INVENTION

[0016] A work machine according to an embodiment will be described below with reference to the drawings. Fig. 1 is a perspective view showing a work machine 1 according to an embodiment. The work machine 1 according to this embodiment is a bulldozer. The work machine 1 comprises a vehicle body 2, a work implement 3, and a drive mechanism 4 for the work implement 3.

[0017] The vehicle body 2 includes a driver's cab 5, a power compartment 6, and a traveling gear 7. A driver's seat (not shown) is located in the driver's cab 5. The power compartment 6 is located in front of the driver's cab 5. The traveling gear 7 supports the vehicle body 2. The traveling gear 7 includes left and right tracks 8. Note that only the left track 8 is shown in FIG. 1. The work machine 1 travels as the tracks 8 rotate.

[0018] The work implement 3 is disposed in front of the vehicle body 2. In this embodiment, the work implement 3 is a blade. The work implement 3 extends in the left-right direction of the work machine 1. The work implement 3 includes a cutting edge 11. The drive mechanism 4 of the work implement 3 includes a work implement frame 12 and a plurality of actuators 13-16. Figure 2 is a perspective view of the work implement 3 and the drive mechanism 4. As shown in Figure 2, the work implement frame 12 supports the work implement 3. The work implement frame 12 includes a first frame 17 and a second frame 18. The first frame 17 and the second frame 18 extend in the front-rear direction of the work machine 1.

[0019] The first frame 17 is connected to the vehicle body 2 so as to be able to swing. The first frame 17 includes a first vehicle body connection portion 23. The first frame 17 is connected to the vehicle body 2 at the first vehicle body connection portion 23. The second frame 18 is arranged spaced apart from the first frame 17 in the left-right direction. The second frame 18 is connected to the vehicle body 2 so as to be able to swing. The second frame 18 includes a second vehicle body connection portion 24. The second frame 18 is connected to the vehicle body 2 at the second vehicle body connection portion 24.

[0020] The first frame 17 and the second frame 18 swing at least around a lift axis A1 relative to the vehicle body 2. The lift axis A1 extends in the left-right direction of the work machine 1. In detail, the first frame 17 and the second frame 18 are connected to the vehicle body 2 via ball joints 19, and can swing in all directions relative to the vehicle body 2. As shown in FIG. 1 , the first frame 17 and the second frame 18 are disposed outside the traveling device 7 in the left-right direction. The first frame 17 and the second frame 18 are connected to the side surfaces of the traveling device 7.

[0021] As shown in FIG. 2, the work machine 3 includes a first frame connection portion 21 and a second frame connection portion 22. The first frame connection portion 21 and the second frame connection portion 22 are arranged on the rear side of the work machine 3. The first frame connection portion 21 is connected to the first frame 17. The second frame connection portion 22 is arranged spaced apart from the first frame connection portion 21 in the left-right direction. The second frame connection portion 22 is connected to the second frame 18. The work machine 3 is supported by the first frame 17 and the second frame 18 so as to be rotatable about a first axis A2 and a second axis A3. The first axis A2 extends in the left-right direction of the work machine 1. The second axis A3 extends in the up-down direction of the work machine 1.

[0022] The multiple actuators 13-16 include a first lift actuator 13, a second lift actuator 14, a first pitch / tilt actuator 15, and a second pitch / tilt actuator 16. The first lift actuator 13 and the second lift actuator 14 are arranged apart from each other in the left-right direction of the work machine 1. The first lift actuator 13 and the second lift actuator 14 are connected to the vehicle body 2 and the work implement 3. The first lift actuator 13 and the second lift actuator 14 are hydraulic cylinders. The first lift actuator 13 and the second lift actuator 14 swing the work implement frame 12 up and down around the lift axis A1. This causes the work implement 3 to perform a lift operation up and down.

[0023] The first pitch / tilt actuator 15 and the second pitch / tilt actuator 16 are arranged apart from each other in the left-right direction of the work machine 1. The first pitch / tilt actuator 15 is connected to the work implement 3 and a first frame 17. The second pitch / tilt actuator 16 is connected to the work implement 3 and a second frame 18. The first pitch / tilt actuator 15 and the second pitch / tilt actuator 16 are hydraulic cylinders.

[0024] The first pitch / tilt actuator 15 rotates the work implement 3 about the first axis A2 relative to the first frame 17. The second pitch / tilt actuator 16 rotates the work implement 3 about the first axis A2 relative to the second frame 18. The extension and contraction of both the first pitch / tilt actuator 15 and the second pitch / tilt actuator 16 causes the work implement 3 to tilt forward or backward about the first axis A2. This forward and backward tilting movement of the work implement 3 is called pitch movement.

[0025] When only one of the first pitch / tilt actuator 15 and the second pitch / tilt actuator 16 extends or retracts, the work implement 3 tilts to the left or right. For example, when only the first pitch / tilt actuator 15 extends or retracts, the right end of the work implement 3 moves up or down. When only the second pitch / tilt actuator 16 extends or retracts, the left end of the work implement 3 moves up or down. As a result, the work implement 3 tilts so that the left and right ends of the work implement 3 are at different heights. This left and right tilting movement of the work implement 3 is called a tilting movement.

[0026] Figure 3 is a block diagram showing the configuration of the control system of the work machine 1. As shown in Figure 3, the work machine 1 is equipped with a power source 30, a hydraulic pump 31, and a power transmission device 32. The power source 30 is, for example, an internal combustion engine. However, the power source 30 may also be an electric motor. Alternatively, the power source 30 may be a hybrid of an internal combustion engine and an electric motor.

[0027] The hydraulic pump 31 is driven by the power source 30 and discharges hydraulic oil. The hydraulic oil discharged from the hydraulic pump 31 is supplied to the lift actuators 13, 14 and the pitch / tilt actuators 15, 16. Although one hydraulic pump 31 is shown in FIG. 3, multiple hydraulic pumps may be provided.

[0028] The power transmission device 32 transmits the driving force of the power source 30 to the traveling device 7. The power transmission device 32 may be, for example, an HST (Hydro Static Transmission). Alternatively, the power transmission device 32 may be, for example, a torque converter or a transmission having a plurality of speed change gears.

[0029] The work machine 1 includes a controller 33 and a control valve 34. The controller 33 is programmed to control the work machine 1 based on acquired data. The controller 33 includes a memory device 35 and a processor 36. The processor 36 includes, for example, a CPU. The memory device 35 includes, for example, a memory and an auxiliary memory device. The memory device 35 may be, for example, a RAM or a ROM. The memory device 35 may be, for example, a semiconductor memory or a hard disk. The memory device 35 is an example of a non-transitory computer-readable recording medium. The memory device 35 stores computer instructions that are executable by the processor 36 and are used to control the work machine 1.

[0030] The control valve 34 is controlled by a command signal from the controller 33. The control valve 34 is disposed between the actuators 13-16 and the hydraulic pump 31. The control valve 34 controls the flow rate of hydraulic oil supplied from the hydraulic pump 31 to the lift actuators 13, 14. The control valve 34 controls the flow rate of hydraulic oil supplied from the hydraulic pump 31 to the pitch / tilt actuators 15, 16.

[0031] The work machine 1 is equipped with an operating device 37 and an input device 38. The operating device 37 includes, for example, a lever. Alternatively, the operating device 37 may include a pedal or a switch. The operator can use the operating device 37 to manually control the travel of the work machine 1 and the operation of the work implement 3. For example, the operating device 37 can control the lift operation, pitch operation, and tilt operation of the work implement 3. The operating device 37 outputs an operating signal that indicates the operation of the operating device 37. The controller 33 receives the operating signal from the operating device 37.

[0032] The input device 38 includes, for example, a touch panel. However, the input device 38 may also include other devices such as switches. The operator can use the operation device 37 to perform control settings for the work machine 1. The input device 38 outputs an input signal that indicates an input to the input device 38. The controller 33 receives the input signal from the input device 38.

[0033] The work machine 1 includes a vehicle body sensor 41, a frame sensor 42, and a work implement sensor 43. The vehicle body sensor 41 is attached to the vehicle body 2. The vehicle body sensor 41 detects the attitude of the vehicle body 2. The frame sensor 42 is attached to the work implement frame 12. The frame sensor 42 detects the attitude of the work implement frame 12. The work implement sensor 43 is attached to the work implement 3. The work implement sensor 43 detects the attitude of the work implement 3.

[0034] The vehicle body sensor 41, the frame sensor 42, and the work equipment sensor 43 are acceleration sensors such as an IMU (Inertial Measurement Unit), for example. However, the vehicle body sensor 41, the frame sensor 42, and the work equipment sensor 43 are not limited to IMUs and may be other acceleration sensors.

[0035] The vehicle body sensor 41 detects the pitch angle, roll angle, and yaw angle of the vehicle body 2. The frame sensor 42 detects the pitch angle, roll angle, and yaw angle of the work implement frame 12. More specifically, the frame sensor 42 is attached to the second frame 18. The frame sensor 42 detects the pitch angle, roll angle, and yaw angle of the second frame 18. The work implement sensor 43 detects the pitch angle, roll angle, and yaw angle of the work implement 3.

[0036] Each sensor detects the pitch angle and roll angle based on the gravitational acceleration. Each sensor also detects the yaw angle by integrating the angular velocity, with the value set to 0 at startup. The vehicle body sensor 41, frame sensor 42, and work equipment sensor 43 each output a detection signal indicating the detected angle.

[0037] The controller 33 detects the position of a predetermined part of the work implement 3 relative to the vehicle body 2 based on the angles detected by the above-mentioned sensors 41-43 and shape data of the work machine 1. The shape data of the work machine 1 is stored in the controller 33 and indicates the positional relationship of each part of the work machine 1. A method for detecting the position of a predetermined part of the work implement 3 will be explained below.

[0038] Figures 4A to 4C are schematic diagrams showing the work implement 3 and work implement frame 12 in the standard position. Figure 4A is a top view, Figure 4B is a side view, and Figure 4C is a rear view. As shown in Figure 4C, in the standard position, the cutting edge 11 of the work implement 3 is horizontal, and the first end 51 and second end 52 of the cutting edge 11 of the work implement 3 are located at the same height. Furthermore, the first frame 17 and the second frame 18 are located at the same height. The fore-and-aft direction of the work implement 3 and the fore-and-aft direction of the vehicle body 2 coincide, and the yaw angle of the work implement 3 relative to the vehicle body 2 is zero degrees.

[0039] The first end 51 and the second end 52 are the left and right ends of the cutting edge 11. As shown in Fig. 4A, the first end 51 is the right end of the cutting edge 11, and the second end 52 is the left end of the cutting edge 11. However, the first end 51 and the second end 52 may be provided in reverse left and right.

[0040] The shape data includes the positions of the first car body connection portion 23 and the second car body connection portion 24 on the car body 2. For example, the positions of the first car body connection portion 23 and the second car body connection portion 24 are indicated by coordinates in a car body coordinate system based on the car body 2. The shape data includes a first actual frame length and a second actual frame length. The first actual frame length indicates the distance between the first car body connection portion 23 and the first frame connection portion 21. The second actual frame length indicates the distance between the second car body connection portion 24 and the second frame connection portion 22.

[0041] The shape data includes work machine data. The work machine data indicates the positional relationship between the second frame connection portion 22 and a predetermined portion of the work machine 3. The predetermined portion is located, for example, on the cutting edge 11 of the work machine 3. In this embodiment, the predetermined portion includes the first end 51 and the second end 52 of the work machine 3.

[0042] When the work implement 3 is in the standard posture, the controller 33 calculates the positions of the first end 51 and the second end 52 of the work implement 3 as follows. The controller 33 calculates the position of the second frame connection part 22 from the position of the second vehicle-body connection part 24 based on the pitch angle, roll angle, and yaw angle of the second frame 18 and the second actual frame length. The controller 33 calculates the position of the first end 51 of the work implement 3 from the position of the second frame connection part 22 based on the pitch angle, roll angle, and yaw angle of the work implement 3 and the work implement data. Here, the yaw angle of the work implement 3 with respect to the vehicle body 2 is zero degrees. The controller 33 also calculates the position of the second end 52 of the work implement 3 from the position of the second frame connection part 22 based on the pitch angle, roll angle, and yaw angle of the work implement 3 and the work implement data.

[0043] 5A to 5C are schematic diagrams showing the work implement 3 and work implement frame 12 in the tilted position. FIG. 5A is a top view. FIG. 5B is a side view. FIG. 5C is a rear view. As shown in FIG. 5C, in the tilted position, the first end 51 and the second end 52 of the work implement 3 are at different heights. The first frame 17 and the second frame 18 are located at different heights. In this case, depending on the structure of the work machine 1, as shown in FIG. 5A, the yaw angle φ of the work implement 3 in the tilted position will be a value other than zero degrees, different from the yaw angle of the work implement 3 in the standard position. Note that in FIG. 5A, dashed line 3' shows the work implement 3 when the yaw angle φ is zero degrees in the tilted position.

[0044] Next, a method for calculating the position of a predetermined part of the work implement 3 when the work implement 3 is in a tilted posture will be described. As shown in Fig. 6, in step S101, the controller 33 calculates the assumed position of the first vehicle body connection part 23. As shown in Fig. 5A, the controller 33 calculates the assumed position 21' of the first frame connection part 21 when the yaw angle φ is assumed to be zero, based on the roll angle and pitch angle of the work implement 3. For example, the controller 33 calculates the assumed position of the first frame connection part 21 using the following equation (1): P21'= Rx(δ)Ry(θ)Rz(0)P21s ···(1) P21' is the coordinate of the assumed position 21' of the first frame connection part 21. P21s is the coordinate of the first frame connection part 21 in the standard posture. δ and θ are the changes in the roll angle and pitch angle from the standard posture, respectively. Rx(δ), Ry(θ), and Rz(0) are the rotation matrices of the roll angle, pitch angle, and yaw angle of the work implement 3, respectively.

[0045] In step S102, controller 33 calculates assumed frame length L1'. The assumed frame length L1' indicates the distance between assumed position 21' of first frame connection portion 21 and first vehicle-body connection portion 23. Controller 33 calculates assumed frame length L1' from the coordinates of assumed position 21' of first frame connection portion 21 and the coordinates of the position of first vehicle-body connection portion 23.

[0046] In step S103, the controller 33 calculates the yaw angle φ of the work implement 3 in the tilt posture. The controller 33 calculates the yaw angle φ of the work implement 3 in the tilt posture based on the difference between the first actual frame length L1 and the assumed frame length L1'. The controller 33 calculates the yaw angle φ of the work implement 3 in the tilt posture using the following equation (2). φ = arcsin{(L1 - L1') / W} ···(2) W is the width of the work implement 3.

[0047] In step S104, the controller 33 calculates the position of a predetermined portion of the work implement 3. In this embodiment, the predetermined portions are the first end 51 and the second end 52 of the work implement 3. When the work implement 3 is in a tilted posture, the controller 33 calculates the positions of the first end 51 and the second end 52 of the work implement 3 based on the roll angle δ and pitch angle θ of the work implement 3, and the yaw angle φ in the tilted posture. For example, the controller 33 calculates the position of the second end 52 of the work implement 3 using the following equation (3): P52t= Rx(δ)Ry(θ)Rz(φ)P52s (3) P52t is the position of the second end 52 of the work implement 3 in the tilt posture. P52s is the position of the second end 52 of the work implement 3 in the standard posture. Note that, in the same manner as above, the position of the first end 51 of the work implement 3 in the tilt posture may be calculated from the position of the first end 51 of the work implement 3 in the standard posture.

[0048] In the control system for the work machine 1 according to the present embodiment described above, the yaw angle φ when the work machine 3 is in a tilted position is calculated from the difference between the assumed frame length L1' of the first frame 17 when the yaw angle of the work machine 3 is assumed to be zero degrees and the actual frame length L1. As a result, even if the yaw angle of the work machine 3 changes due to a tilt operation, the position of a predetermined part of the work machine 3 can be detected with high accuracy in the work machine 1.

[0049] The controller 33 may control the work machine 3 to operate based on the position of a predetermined portion of the work machine 3 detected as described above. For example, as shown in FIG. 7, the controller 33 may acquire a target design terrain 60. The controller 33 may control the work machine 1 to move a predetermined portion of the work machine 3 in accordance with the target design terrain 60. For example, the controller 33 may acquire the target design terrain 60 via the input device 38. The controller 33 may automatically generate the target design terrain 60.

[0050] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the gist of the invention.

[0051] The work machine 1 is not limited to a bulldozer, and may be other vehicles such as a wheel loader or motor grader. The controller 33 may have multiple controllers that are separate from each other. The work machine 1 may be operable remotely. In that case, the controller 33, the operation device 37, and the input device 38 may be located outside the work machine 1. The controller 33 may control the work machine 1 by communicating wirelessly with the work machine 1.

[0052] The processing by the controller 33 is not limited to that in the above embodiment and may be modified. Part of the processing by the controller 33 may be omitted. Alternatively, part of the above-described processing may be modified.

[0053] For example, in the above embodiment, the frame sensor 42 is attached to the second frame 18. However, the frame sensor 42 may be attached to the first frame 17. Alternatively, the frame sensor 42 may be attached to each of the first frame 17 and the second frame 18. In this case, the controller 33 may calculate the position of a predetermined portion of the work implement 3 from the position of the first frame connection portion 21.

[0054] In the above embodiment, the yaw angle when the work implement 3 is in a tilt posture is calculated from the difference between the assumed frame length L1' and the actual frame length L1 of the first frame 17 when the yaw angle is assumed to be zero degrees. However, the yaw angle when the work implement 3 is in a tilt posture may also be calculated from the difference between the assumed frame length and the actual frame length of the second frame 18 when the yaw angle is assumed to be zero degrees.

[0055] The predetermined angle may be an angle other than zero degrees. The attitudes of the work implement 3 used to calculate the yaw angle are not limited to the standard attitude and tilt attitude described above, and may be two or more attitudes with different yaw angles.

[0056] The predetermined portion is not limited to the first end 51 and the second end 52 of the cutting edge 11 of the work implement 3, but may be another portion. For example, the predetermined portion may be the center of the cutting edge 11. [Industrial Applicability]

[0057] According to the present invention, even if the yaw angle of the work implement changes due to a tilt operation, the position of a predetermined part of the work implement can be detected with high accuracy in the work machine. [Explanation of symbols]

[0058] 1: Work machine, 2: Body, 3: Work implement, 12: Work implement frame, 15: First pitch / tilt actuator, 16: Second pitch / tilt actuator, 17: First frame, 18: Second frame, 21: First frame connection part, 21': Assumed position of first frame connection part 21, 22: Second frame connection part, 23: First body connection part, 24: Second body connection part, 33: Controller, 43: Work implement sensor, 51: First end part, 52: Second end part, L1: First actual frame length, L1': Assumed frame length

Claims

1. 1. A system for controlling a work machine, comprising: The work machine includes: The car body and a work machine frame including a first frame including a first vehicle body connection portion connected to the vehicle body, and a second frame including a second vehicle body connection portion connected to the vehicle body and disposed apart from the first frame in the left-right direction; a work machine including a first frame connection portion connected to the first frame, a second frame connection portion disposed apart in the left-right direction from the first frame connection portion and connected to the second frame, and a predetermined portion; a first actuator that moves the first frame relative to the vehicle body; a second actuator that moves the second frame relative to the vehicle body; Including, a yaw angle of the work implement relative to the vehicle body when the work implement is in a first posture is different from a yaw angle of the work implement when the work implement is in a second posture different from the first posture, The system comprises: a work machine sensor attached to the work machine and detecting a roll angle and a pitch angle of the work machine; A controller; Equipped with The controller acquire an actual frame length indicating the distance between the first vehicle body connection portion and the first frame connection portion; acquiring a position of the first vehicle body connection portion; Acquire the roll angle and pitch angle of the work machine; When the work implement is in the first posture, an assumed position of the first frame connection portion is calculated based on a roll angle and a pitch angle of the work implement when the yaw angle is assumed to be a predetermined angle; calculating an assumed frame length indicating a distance between the assumed position of the first frame connection portion and the first vehicle body connection portion; calculating a yaw angle of the work implement in the first posture based on a difference between the actual frame length and the assumed frame length; calculating the position of the predetermined portion of the work machine based on a roll angle and a pitch angle of the work machine and a yaw angle of the work machine in the first attitude; system.

2. The controller controls the work machine based on the position of the predetermined part of the work machine. The system of claim 1 .

3. The vehicle body further includes a traveling device that causes the work machine to travel, the first frame and the second frame are disposed on outer sides of the traveling device in the left-right direction; The system of claim 1 .

4. The work machine sensor is an acceleration sensor. The system of claim 1 .

5. In the first posture, the heights of the left and right ends of the work machine are different from each other, In the second posture, the heights of the left and right ends of the work machine are the same. The system of claim 1 .

6. The predetermined angle is zero degrees. The system of claim 1 .

7. 1. A method for controlling a work machine, comprising: The work machine includes: The car body and a work machine frame including a first frame including a first vehicle body connection portion connected to the vehicle body, and a second frame including a second vehicle body connection portion connected to the vehicle body and disposed apart from the first frame in the left-right direction; a work machine including a first frame connection portion connected to the first frame, a second frame connection portion disposed apart in the left-right direction from the first frame connection portion and connected to the second frame, and a predetermined portion; Including, a yaw angle of the work implement relative to the vehicle body when the work implement is in a first posture is different from a yaw angle of the work implement when the work implement is in a second posture different from the first posture, The method comprises: Obtaining a position of the first vehicle body connection portion; Detecting a roll angle and a pitch angle of the work machine; obtaining an actual frame length indicating a distance between the first vehicle body connection portion and the first frame connection portion; When the work implement is in the first posture, calculating an assumed position of the first frame connection portion when the yaw angle is assumed to be a predetermined angle based on a roll angle and a pitch angle of the work implement; Calculating an assumed frame length indicating a distance between an assumed position of the first frame connection portion and the first vehicle body connection portion; Calculating a yaw angle of the work implement in the first posture based on a difference between the actual frame length and the assumed frame length; When the work implement is in the first posture, calculating the position of the predetermined part of the work implement based on a roll angle and a pitch angle of the work implement and a yaw angle of the work implement in the first posture; A method for providing the above.

8. further comprising controlling the work machine based on a position of the predetermined portion of the work machine. The method of claim 7.

9. In the first posture, the heights of the left and right ends of the work machine are different from each other, In the second posture, the heights of the left and right ends of the work machine are the same. The method of claim 7.

10. The predetermined angle is zero degrees. The method of claim 7.

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