Work machine

Abstract

The purpose of the present invention is to provide a work machine which makes it possible to suppress a decrease in work efficiency while ensuring work precision. Provided is a control device of a work machine comprising: a prediction point generation unit which generates a prediction point indicating a position where a work tool is predicted to arrive in each control cycle when any control cycle designated in advance is reached in the future; a design surface determination unit which determines a change point where the shape of a design surface changes; a prediction point interval adjustment unit which adjusts a time interval of the control cycle so as to shorten the interval between prediction points generated near the change point in the design surface when the prediction point for the work tool is generated by the prediction point generation unit; an operation generation unit which generates an operation command for an actuator such that the work tool moves so as to follow the prediction point generated with the time interval adjusted; and an actuator control unit which controls the operation of the actuator on the basis of the operation command.

Description

Construction machine

[0001] The present invention relates to a construction machine.

[0002] With the advent of information-based construction, construction machines with machine guidance or machine control functions have been developed. Machine guidance for a hydraulic excavator, which is an example of a construction machine, is a function of monitoring and displaying the position and orientation of each component of a working device such as a boom, arm, or bucket on a monitor and notifying an operator. Machine control for a hydraulic excavator is a function of intervening in an operator's operation to control (operation support control) a working device so that a bucket moves along a design surface representing a target shape of a work object. Machine control can prevent the bucket from digging too deep or idling above the design surface, allowing the operator to perform the intended work. Therefore, machine control can contribute to ensuring work efficiency and improving work accuracy. As a prior art of this machine control, for example, Patent Document 1 is known.

[0003] Patent Document 1 discloses a control system for a construction machine including a working machine (working device) including an arm and a bucket detachably attached to the arm, the control system including: a target value generation unit that generates a target value of a control amount of the working machine; a prediction model storage unit that stores a prediction model of the working machine; a weight data acquisition unit that acquires weight data of the bucket; a prediction model update unit that updates the prediction model based on the weight data; a prediction unit that calculates a predicted value of a control amount of the working machine based on the target value and the prediction model and calculates a drive amount for controlling the working machine based on the predicted value; and a command unit that outputs a control command for controlling the working machine based on the drive amount.

[0004] Japanese Patent Application Laid-Open No. 2020-125594

[0005] The control system disclosed in Patent Document 1 realizes control taking into account the change in the weight of the bucket by model predictive control having a prediction model capable of updating the bucket weight when the weight changes during bucket replacement, preventing the bucket from digging too deep.

[0006] However, the control system disclosed in Patent Document 1 predicts prediction points at equal time intervals between the current coordinates of the bucket tip (toe coordinates) and a predetermined prediction range. When prediction points are set at equal time intervals within a limited number of prediction points, depending on the shape of the design surface, the prediction points may not be appropriately assigned to the design surface, resulting in over-digging or missed shots by the bucket. As a result, the control system disclosed in Patent Document 1 may not be able to work accurately on the design surface, or additional work may be required, reducing work efficiency.

[0007] The present invention has been made in view of the above, and aims to provide a work machine that can suppress a decrease in work efficiency while ensuring work accuracy.

[0008] To solve the above problems, the present invention provides a work machine comprising: a multi-jointed work device that includes a work tool and is rotatably mounted to a vehicle body; an actuator that drives the work device; a posture sensor that detects posture information of the work device; a storage device that stores design information including coordinates of a design plane representing the target shape of the work object; and a control device that controls the operation of the actuator, wherein the control device includes: a coordinate calculation unit that calculates the coordinates of the tip of the work tool based on the posture information; a speed calculation unit that calculates the moving speed of the tip of the work tool based on the coordinates of the work tool calculated by the coordinate calculation unit; and a prediction point that generates a prediction point representing the position that the work tool is expected to reach in each control cycle when a predetermined arbitrary control cycle arrives in the future, based on the coordinates of the work tool, the moving speed of the work tool, and the design information. The device is characterized by comprising: a measurement point generation unit; a design surface determination unit that determines change points in which the shape of the design surface changes based on the design information; a prediction point interval adjustment unit that adjusts the time interval of the control cycle so that the interval between the prediction points generated near the change points on the design surface when the prediction points of the work tool are generated by the prediction point generation unit is shortened, based on the coordinates of the work tool, the movement speed of the work tool, the change points on the design surface, and the design information; an operation generation unit that generates an operation command for the actuator so that the work tool moves in accordance with the prediction points whose time interval has been adjusted, based on the prediction points generated by the time interval, the coordinates of the work tool, and the design information; and an actuator control unit that controls the operation of the actuator based on the operation command generated by the operation generation unit.

[0009] According to the present invention, it is possible to provide a work machine that can suppress a decrease in work efficiency while ensuring work accuracy. Other problems, components, and effects will be clarified by the following description of embodiments.

[0010] Figure 2 shows a schematic perspective view illustrating the configuration of a hydraulic excavator, an example of a work machine. Figure 6 shows a flowchart illustrating the functions of the control device of the first embodiment. Figure 6 shows a schematic diagram illustrating the arrangement of prediction points when the design plane is a horizontal plane. Figure 7 shows a schematic diagram illustrating the arrangement of prediction points when the design plane changes from an inclined plane to a horizontal plane. Figure 8 shows a schematic diagram illustrating the arrangement of prediction points when the design plane is a curved plane. Figure 9 shows a schematic diagram illustrating the method for searching for change points. Figure 1 shows a schematic diagram illustrating the method for adjusting the time interval of prediction points. Figure 2 shows a flowchart illustrating the processing contents of the control device. Figure 1 shows a schematic view illustrating the functions of the control device of the second embodiment. Figure 1 shows a schematic diagram illustrating the arrangement of prediction points when the design plane changes from a horizontal plane to an inclined plane. Figure 1 shows a flowchart illustrating the processing contents of the control device of the first embodiment.

[0011] Embodiments of the present invention will be described below with reference to the drawings. In each embodiment, components denoted by the same reference numerals are similar in each embodiment unless otherwise specified, and their descriptions will be omitted.

[0012] [First Embodiment] A first embodiment of the present invention will be described with reference to Figures 1 to 5. In this embodiment, a hydraulic excavator will be used as an example of the work machine 100. Figure 1 is a schematic perspective view showing the configuration of a hydraulic excavator, which is an example of the work machine 100.

[0013] In Figure 1, the work machine 100 comprises a multi-joint work device 24 formed by connecting a plurality of components (boom 8, arm 9, and bucket 10, which is a work tool) that rotate vertically, and an upper slewing body 22 and a lower traveling body 20 that constitute the vehicle body 20, 22. The upper slewing body 22 is rotatably mounted to the lower traveling body 20 via a slewing mechanism 21. The slewing mechanism 21 includes a slewing motor 23 and a slewing angle sensor 26d. The slewing motor 23 drives the upper slewing body 22 to slewing relative to the lower traveling body 20. The slewing angle sensor 26d detects the slewing angle of the upper slewing body 22 relative to the lower traveling body 20.

[0014] The working device 24 has a boom 8, an arm 9, and a bucket 10. The base end of the boom 8 is rotatably connected to the front of the upper slewing body 22. The base end of the arm 9 is rotatably connected to the tip of the boom 8. The base end of the bucket 10 is rotatably connected to the tip of the arm 9. The bucket 10 is a working tool used to perform excavation and other operations on a work surface such as a mine slope or horizontal surface. The boom 8, arm 9, bucket 10, upper slewing body 22, and lower traveling body 20 are driven by actuators, namely a boom cylinder 5, arm cylinder 6, bucket cylinder 7, slewing motor 23, and traveling motor 3, respectively. In this embodiment, the boom cylinder 5, arm cylinder 6, bucket cylinder 7, slewing motor 23, and traveling motor 3 are collectively referred to as actuator 35.

[0015] In this embodiment, the work machine 100 has a vehicle body coordinate system set up. The vehicle body coordinate system has its origin at the intersection of the pivot center axis 25 of the upper slewing body 22 and the lower surface of the upper slewing body 22. The vehicle body coordinate system is a Cartesian coordinate system having a z-axis that is positive upwards along the pivot center axis 25, an x-axis that is positive forwards in the front-rear direction of the upper slewing body 22 and perpendicular to the z-axis from the origin, and a y-axis that is positive to the right in the left-right direction perpendicular to the z-axis and x-axis from the origin.

[0016] A cab 2, in which the operator sits, is mounted on the front left side of the upper rotating body 22. A control device 28, which controls the overall operation of the work machine 100, is also installed on the upper rotating body 22. The cab 2 is equipped with operating levers 2a and 2b for operating actuators 35. The operating levers 2a and 2b can be tilted forward, backward, left, and right, respectively. The operating levers 2a and 2b are connected to a detection device that electrically detects the amount of tilt, i.e., the amount of operation, of the operating levers 2a and 2b. This detection device outputs the amount and direction of operation of the operating levers 2a and 2b as an operation signal and transmits it to the control device 28. In this embodiment, the operating levers 2a and 2b and this detection device are collectively referred to as the operating device 41.

[0017] The actuator 35 operates using hydraulic fluid supplied from a hydraulic pump driven by a prime mover such as an engine or electric motor. The operation of the actuator 35 is controlled by controlling the flow rate and direction of the hydraulic fluid supplied from the hydraulic pump using a control valve. The operation of the control valve is controlled by the control device 28 based on an operation signal from the operating device 41. In this way, the operation of the actuator 35 is controlled.

[0018] A boom angle sensor 26a, an arm angle sensor 26b, and a bucket angle sensor 26c are attached to the connection points of the boom 8 to the upper slewing body 22, the arm 9 to the boom 8, and the bucket 10 to the arm 9, respectively. The boom angle sensor 26a, arm angle sensor 26b, and bucket angle sensor 26c may be composed of mechanical angle sensors such as potentiometers. The boom angle sensor 26a detects the rotation angle of the boom 8 relative to the upper slewing body 22 and transmits it to the control device 28. The arm angle sensor 26b detects the rotation angle of the arm 9 relative to the boom 8 and transmits it to the control device 28. The bucket angle sensor 26c detects the rotation angle of the bucket 10 relative to the arm 9 and transmits it to the control device 28.

[0019] The rotation angle of the boom 8 is the angle that the longitudinal direction of the boom 8 (the direction in which the line segment connecting the tip and base of the boom 8 extends) makes with the xy plane. The rotation angle of the arm 9 is the angle that the longitudinal direction of the arm 9 (the direction in which the line segment connecting the tip and base of the arm 9 extends) makes with the longitudinal direction of the boom 8. The rotation angle of the bucket 10 is the angle that the longitudinal direction of the bucket 10 (the direction in which the line segment connecting the tip and base of the bucket 10 extends) makes with the longitudinal direction of the arm 9. In this embodiment, the boom angle sensor 26a, arm angle sensor 26b, bucket angle sensor 26c, and slewing angle sensor 26d are collectively referred to as the attitude sensor 26. The rotation angles of the boom 8, arm 9, and bucket 10, as well as the slewing angle of the upper slewing body 22, represent the attitude information of the work device 24 and the upper slewing body 22 detected by the attitude sensor 26.

[0020] In this embodiment, the pivot point of the work device 24 (the connection point between the boom 8 and the upper slewing body 22) is positioned away from the pivot axis 25, but the pivot point of the work device 24 may be positioned intersecting the pivot axis 25. Also, the attitude sensor 26 in this embodiment may be composed of an inertial measurement unit (IMU), tilt sensor, rotation angle sensor, or stroke sensor, rather than a mechanical angle sensor such as a potentiometer.

[0021] Figure 2 is a block diagram illustrating the functions of the control device 28 of the first embodiment.

[0022] The control device 28 of this embodiment controls the operation of the work machine 100, particularly the operation of the work device 24, by model predictive control. Model predictive control is a control method that predicts the future target operating state of the controlled object within a predetermined prediction range (a finite evaluation interval, also called the prediction horizon), and performs an optimization calculation to minimize the value of the evaluation function within the prediction range to obtain the control input. The control device 28 using model predictive control calculates the positions (hereinafter also called "predicted points") that each part of the work machine 100 is predicted to reach in each control cycle when the control sampling period (hereinafter also called the "control cycle") arrives in the future, based on the discretized dynamics and hydraulic models of the work machine 100. Then, the control device 28 using model predictive control predicts the future target operating state of the work machine 100 based on the prediction model, performs an optimization calculation to calculate the appropriate control input for each control cycle, and obtains the optimal control input at the present time.

[0023] In this way, the control device 28 ensures highly accurate operation control of the work machine 100 by performing optimization calculations of the control input, taking into account the positions of each part of the work machine 100 that are expected to be reached in the future. In this embodiment, the operation control of the work machine 100 by the control device 28 will be explained using the case where the work machine 100, which is a hydraulic excavator, performs its main operation, excavation, as an example.

[0024] The control device 28 is configured to include a processor and memory, and the processor executes a program to realize various functions of the control device 28. These various functions include a coordinate calculation unit 30, a velocity calculation unit 31, a prediction point generation unit 32, a motion generation unit 33, an actuator control unit 34, a design surface determination unit 36, and a prediction point interval adjustment unit 37.

[0025] The coordinate calculation unit 30 calculates the coordinates of representative points of each part of the work machine 100 based on the posture information transmitted from the posture sensor 26. In particular, the coordinate calculation unit 30 calculates the coordinates (toe coordinates) of the tip of the bucket 10, which is a work tool. The coordinate calculation unit 30 transmits the calculated coordinates of the representative points (including the coordinates of the tip of the bucket 10) to the speed calculation unit 31, the prediction point interval adjustment unit 37, the prediction point generation unit 32, and the motion generation unit 33.

[0026] The velocity calculation unit 31 calculates the moving speed of the tip of the bucket 10, which is a work tool, based on the coordinates of the representative point calculated by the coordinate calculation unit 30 and the operation signal transmitted from the operation device 41, and transmits it to the prediction point generation unit 32 and the prediction point interval adjustment unit 37.

[0027] The design surface determination unit 36 ​​determines change points 39, which are points where the shape (relief height, curvature, or angle) of the design surface 40 changes, based on the work / design information stored in the storage device 29. The work / design information includes work information and design information. The work information is information indicating the work content of the work machine 100. The design information is information indicating the target shape of the work object according to the work content. The design information includes the coordinates of the design surface 40 representing the target shape of the work object. The design surface determination unit 36 ​​also determines an unchanged range 43, which indicates the range of points where the shape of the design surface 40 does not change, based on the work / design information. The design surface determination unit 36 ​​then transmits the coordinates of the change points 39, the coordinates of the area near the change points 39 on the design surface 40 (hereinafter also referred to as "near the change points 42") (the coordinates of the start and end points of the area near the change points 42), and the coordinates of the unchanged range 43 (the coordinates of the start and end points of the unchanged range 43) to the prediction point interval adjustment unit 37. Details of the design surface determination unit 36 ​​will be described later.

[0028] The prediction point interval adjustment unit 37 adjusts the time interval between prediction points generated near the change point 42 of the design surface 40 when prediction points are generated by the prediction point generation unit 32 (hereinafter also simply referred to as "time interval between prediction points"). The prediction points of the bucket 10 represent the positions that the bucket 10 is expected to reach in each control cycle when a predetermined arbitrary control cycle arrives in the future. Based on the coordinates of the representative point calculated by the coordinate calculation unit 30, the moving speed of the tip of the bucket 10 calculated by the velocity calculation unit 31, the determination result of the design surface determination unit 36 ​​(including the coordinates of the change point 39, the area near the change point 42, and the unchanged range 43), and the work / design information stored in the storage device 29, the prediction point interval adjustment unit 37 adjusts the time interval between prediction points so that the total number of prediction points included in the prediction range is less than or equal to a predetermined upper limit. The prediction point interval adjustment unit 37 transmits the time interval between the prediction points near the adjusted change point 42 to the prediction point generation unit 32. Details of the prediction point interval adjustment unit 37 will be described later.

[0029] The prediction point generation unit 32 generates prediction points over a prediction range, which is the range from the present moment to the arrival of a predetermined arbitrary control cycle. That is, the prediction point generation unit 32 generates prediction points for the arbitrary control cycle. Based on the coordinates of the representative point calculated by the coordinate calculation unit 30, the moving speed of the tip of the bucket 10 calculated by the velocity calculation unit 31, the time interval between prediction points near the change point 42 adjusted by the prediction point interval adjustment unit 37, and the work / design information stored in the storage device 29, the prediction point generation unit 32 generates prediction points for the bucket 10 for the arbitrary control cycle. The prediction point generation unit 32 generates prediction points such that the total number of prediction points included in the prediction range is less than or equal to a predetermined upper limit. The prediction point generation unit 32 transmits the generated prediction points for the bucket 10 to the operation generation unit 33. Details of the prediction point generation unit 32 will be described later.

[0030] The motion generation unit 33 generates motion commands for the actuators 35 so that the bucket 10 moves in accordance with predicted points whose time intervals have been adjusted. The motion generation unit 33 generates the motion commands based on the predicted points of the bucket 10 generated by the predicted point generation unit 32, the coordinates of the representative points calculated by the coordinate calculation unit 30, the work / design information stored in the storage device 29, and the attitude information transmitted from the attitude sensor 26. The motion commands are instructions that indicate how each actuator 35 should be operated to achieve the target operating state of the work machine 100, in particular the target operating state of the work device 24. The motion commands include, for example, the target cylinder speed or target motor rotation speed of the actuator 35. The motion generation unit 33 transmits the generated motion commands to the actuator control unit 34. Details of the motion generation unit 33 will be described later.

[0031] The actuator control unit 34 controls the operation of the actuator 35 based on the operation commands for the actuator 35 generated by the motion generation unit 33. Specifically, the actuator control unit 34 operates the control valve connected to the actuator 35 in accordance with the operation commands. The actuator control unit 34 also synchronizes the operating speed of each actuator 35 based on the response of the actuator 35 detected by sensors related to the actuator 35 (including the attitude sensor 26).

[0032] Next, the details of the design surface determination unit 36 ​​will be explained using Figures 3A to 3C. Figure 3A is a schematic diagram illustrating the arrangement of prediction points when the design surface 40 is a horizontal plane. Figure 3B is a schematic diagram illustrating the arrangement of prediction points when the design surface 40 changes from an inclined surface to a horizontal surface. Figure 3C is a schematic diagram illustrating the arrangement of prediction points when the design surface 40 is a curved surface.

[0033] The design surface determination unit 36 ​​determines, for example, whether or not there is a change in the shape of the design surface 40, as shown in Figure 3B, based on the work / design information stored in the storage device 29. That is, the design surface determination unit 36 ​​determines, based on the work / design information, whether or not there is a change point 39 where the shape of the design surface 40 changes. The design surface determination unit 36 ​​then classifies the coordinates of the design surface 40 into coordinates near the change point 42 and coordinates in the unchanged range 43. The range of the range near the change point 42 changes depending on the magnitude 44 of the angle change of the design surface 40 and the current movement speed of the tip of the bucket 10. For example, if the magnitude 44 of the angle change of the design surface 40 is large, it is preferable to expand the range near the change point 42 in order to prevent the bucket 10 from digging too far. For example, if the current movement speed of the tip of the bucket 10 is fast, the possibility of the bucket 10 digging too far increases, so it is preferable to expand the range near the change point 42.

[0034] Furthermore, if the magnitude of the angular change 44 of the design surface 40 is less than or equal to an allowable value (for example, 30°, which is a common value for the toe angle), the design surface determination unit 36 ​​may consider the angular change of the design surface 40 to be small, and may classify the coordinates of the design surface 40 as an unchanged range 43. The unchanged range 43 is the range in which the bucket 10 can excavate along the design surface 40 by maintaining the movement velocity vector of the tip of the bucket 10 within that range. In other words, the unchanged range 43 is the range in which the bucket 10 can move linearly. The unchanged range 43 shown in Figure 3B consists of the range from the tip of the bucket 10 at the present time to the starting point of the vicinity of the change point 42, and the range from the end point of the vicinity of the change point 42 to the final point of the predicted range (time t4 in Figure 3B).

[0035] In the unchanged range 43, even if the time interval between prediction points is extended beyond the predetermined normal time interval, it does not affect the excavation operation. On the other hand, near the change point 42, if the movement velocity vector of the tip of the bucket 10 is maintained from before the change point 42, there is a possibility that the bucket 10 will over-excavate or miss the target. For this reason, in the range where there is a change in the shape of the design surface 40, it is necessary to adjust the movement velocity vector of the tip of the bucket 10 in detail to change the excavation direction. Therefore, the control device 28 adjusts the time interval between prediction points near the change point 42 to be shorter than the predetermined normal time interval. As a result, the control device 28 can calculate the change in the movement velocity vector of the tip of the bucket 10 in detail near the change point 42, and operate the bucket 10 with high precision.

[0036] By classifying the coordinates of the design surface 40 in this way, the design surface determination unit 36 ​​makes it possible for the prediction point interval adjustment unit 37 to appropriately adjust the time interval of the prediction points.

[0037] For example, as shown in Figure 3A, if the design surface 40 is a horizontal plane, there is no change in the shape of the design surface 40 during the excavation operation (the magnitude of the angle change 44 of the design surface 40 is 0°). Therefore, the design surface determination unit 36 ​​determines that "there is no change in the shape of the design surface 40" and transmits only this determination result to the prediction point interval adjustment unit 37.

[0038] On the other hand, as shown in Figure 3B, if the shape of the design surface 40 changes at the change point 39, the design surface determination unit 36 ​​determines that "there is a change in the shape of the design surface 40" because the shape of the design surface 40 changes during the excavation operation. For example, the design surface determination unit 36 ​​determines that the magnitude of the angle change 44 of the design surface 40 is within the allowable value B. ＤＰ If the value is greater than the specified value, it is determined that "there has been a change in the shape of the design surface 40." The design surface determination unit 36 ​​then transmits this determination result, the coordinates of the change point 39, the coordinates of the start and end points of the vicinity of the change point 42, and the coordinates of the start and end points of the unchanged range 43 to the prediction point interval adjustment unit 37.

[0039] Furthermore, whether or not the shape of the design surface 40 changes may be determined not only by the angle change of the design surface 40, but also, as shown in Figure 3C, based on whether or not the curvature of the design surface 40 changes. In this case, even though there is no clear change point 39, the design surface determination unit 36 ​​considers the centers of both ends of the portion that forms the curved surface of the design surface 40 as the change point 39, and the curvature 45 of the portion that forms the curved surface is within the allowable value R. ＤＰ By determining whether or not it is greater than or equal to R, it is possible to determine whether or not there is a change in the shape of the design surface 40. The design surface determination unit 36 ​​determines whether the curvature 45 is greater than or equal to the allowable value R. ＤＰ If the value is greater than this, it is determined that "there has been a change in the shape of the design surface 40". The design surface determination unit 36 ​​then transmits this determination result, the coordinates of the change point 39, the coordinates of the start and end points of the vicinity of the change point 42, and the coordinates of the start and end points of the unchanged range 43 to the prediction point interval adjustment unit 37.

[0040] Next, the details of the prediction point interval adjustment unit 37 will be explained using Figures 4A and 4B. Figure 4A is a schematic diagram illustrating the method for searching for change points 39. Figure 4B is a schematic diagram illustrating the method for adjusting the time interval of prediction points.

[0041] First, if the design surface determination unit 36 ​​determines that "there is a change in the shape of the design surface 40", as shown in Figure 4A, the prediction point interval adjustment unit 37 searches for coordinates S1 to SN that are predicted to be reached when the coordinate S0 of the tip of the bucket 10 at the current time t0 moves at the moving speed V0 of the tip of the bucket 10 at the current time t0, within the prediction range from the current time t0 to the final point tN (N=4 in Figure 4A). Then, the prediction point interval adjustment unit 37 searches whether or not a change point 39 exists on the design surface 40 within the prediction range from the current time t0 to the final point tN (i.e., between coordinate S0 and coordinate SN). If no change point 39 exists, the prediction point interval adjustment unit 37 fixes the time interval between prediction points when the prediction point generation unit 32 generates the prediction points.

[0042] On the other hand, when there is a change point 39 within the prediction range from the current time t0 to the final time tN, the prediction point interval adjustment unit 37 adjusts the time interval between the prediction points generated near the change point 42. Specifically, the prediction point interval adjustment unit 37 adjusts the time interval so that among the prediction points generated adjacent to the change point 39, the prediction point closest to the change point 39 is assigned to the change point 39. In the example shown in FIG. 4A, there is a change point 39 between the coordinates S2 and S3, and the coordinate S2 is the closest to the change point 39. In this case, as shown in FIG. 4B, the prediction point interval adjustment unit 37 adjusts the time interval so that the prediction point at time t2 is assigned to the change point 39. Thereby, the control device 28 can generate an operation command while surely predicting the target operation state of the working device 24 at the change point 39, and can operate the bucket 10 with high accuracy in accordance with the shape change of the design surface 40.

[0043] Next, when there is a change point 39 within the prediction range from the current time t0 to the final time tN, the prediction point interval adjustment unit 37 fixes the prediction point at the current time t0 and the prediction point at the final time tN. On the other hand, for the prediction points at the intermediate times t1 to t(N−1), the prediction point interval adjustment unit 37 can be made variable according to the vicinity 42 of the change point and the unchanged range 43. Therefore, among the prediction points at the intermediate times t1 to t(N−1), the prediction point interval adjustment unit 37 extends the time interval between the prediction points generated in the unchanged range 43 to be longer than the normal time interval, and for the prediction points generated near the change point 42, the prediction point interval adjustment unit 37 shortens the time interval between the prediction points to be shorter than the normal time interval. In the example shown in FIG. 4B, the prediction point interval adjustment unit 37 extends the time interval between the prediction points from time t0 to time t1 corresponding to the unchanged range 43 and between the prediction points from time t3 to time t4. In the example shown in FIG. 4B, the prediction point interval adjustment unit 37 adjusts (shortens) the time interval so that the interval between the prediction points between time t1 and time t3 corresponding to the vicinity 42 of the change point is shortened. Thereby, the control device 28 can generate an operation command while predicting in detail the target operation state of the working device 24 near the change point 42, can operate the bucket 10 with high accuracy, and does not increase the calculation load because the number of prediction points does not increase.

[0044] In the prediction point interval adjustment unit 37, the array data of the time intervals of the adjusted prediction points is transmitted to the prediction point generation unit 32.

[0045] In addition, FIGS. 4A and 4B show an example where the number of arbitrary control cycles (prediction horizon number) N = 4 specified in advance as the prediction range, but the number N of the control cycles is not particularly limited. The number N of the control cycles depends on the processing performance of the control device 28. From the viewpoint of control performance, it is required that the control device 28 has a high processing performance that can increase the number N of the control cycles, but a control device 28 having a high processing performance is costly. In the present embodiment, it is preferable because it is not necessary to adopt the high-cost control device 28 by specifying a prediction range having the number N of the control cycles that can ensure appropriate control performance and adjusting the time intervals between prediction points within this prediction range.

[0046] Finally, the details of the motion generation unit 33 will be described.

[0047] The motion generation unit 33 predicts the future target motion state of the working machine 100, particularly the target motion state of the working device 24, based on the prediction points of the bucket 10 generated by the prediction point generation unit 32, the coordinates of the representative point calculated by the coordinate calculation unit 30, the work / design information stored in the storage device 29, and the attitude information transmitted from the attitude sensor 26, and generates an operation command for the actuator 35 to realize the target motion state. For example, the motion generation unit 33 calculates the moving speed vector of the tip of the bucket 10 based on the coordinates of the tip of the bucket 10 and the prediction points, and calculates the target angular velocities of the boom 8, the arm 9, and the bucket 10 as the target motion state using the inverse Jacobian matrix. Then, the motion generation unit 33 may calculate the target cylinder speed etc. of the actuator 35 to realize the target angular velocity and generate an operation command.

[0048] On the other hand, in model predictive control, the control input is determined by performing an optimization calculation that minimizes the value of the evaluation function within the prediction range. For example, the motion generation unit 33 may use the deviation between the coordinates of the tip of the bucket 10 and the predicted point as the evaluation function, and calculate a control input that minimizes the value of the evaluation function. In this case, the motion generation unit 33 does not need to individually design the drive amount of each actuator 35, and can automatically obtain the appropriate drive amount of the actuator 35 depending on the situation. The evaluation function described above is merely an example, and a different evaluation function may be used if the same idea is followed. The motion generation unit 33 may also switch between prioritizing the elimination of the deviation or prioritizing the suppression of the control input by adjusting the weight matrix as a parameter for adjusting the motion.

[0049] Figure 5 is a flowchart showing the processing steps of the control device 28 shown in Figure 2. The processing steps from start to end in this flowchart are performed by the control device 28 at each calculation step.

[0050] In step S101, the control device 28 acquires work / design information transmitted from the user interface or another system and stored in the storage device 29. After that, the control device 28 proceeds to step S102.

[0051] In step S102, the control device 28 acquires attitude information detected by and transmitted from the attitude sensor 26. After that, the control device 28 proceeds to step S103.

[0052] In step S103, the control device 28 calculates the coordinates of representative points of each part of the work machine 100 based on the posture information acquired in step S102. After that, the control device 28 proceeds to step S104.

[0053] In step S104, the control device 28 acquires the operation signal detected by the operating device 41 and transmitted from the operating device 41. After that, the control device 28 proceeds to step S105.

[0054] In step S105, the control device 28 calculates the movement speed of the tip of the bucket 10 based on the operation signal acquired in step S104 and the coordinates of the representative point acquired in step S103. After that, the control device 28 proceeds to step S106.

[0055] In step S106, the control device 28 determines whether or not there is a change in the shape of the design surface 40 based on the work / design information acquired in step S101. If it is determined that there is a change in the shape of the design surface 40, the control device 28 proceeds to step S107. If it is determined that there is no change in the shape of the design surface 40, the control device 28 proceeds to step S110.

[0056] In step S107, the control device 28 classifies the coordinates of the design plane 40 into coordinates near the change point 42 and coordinates in the unchanged range 43. After that, the control device 28 proceeds to step S108.

[0057] In step S108, the control device 28 adjusts the time intervals between prediction points so that the prediction point closest to the change point 39 is assigned to the change point 39 from among the prediction points generated adjacent to the change point 39. After that, the control device 28 proceeds to step S109.

[0058] In step S109, the control device 28 adjusts the time intervals between prediction points other than the prediction point assigned to the change point 39 (prediction points generated near the change point 42 or in the unchanged range 43) according to the classification result in step S107. After that, the control device 28 proceeds to step S111.

[0059] In step S110, the control device 28 decides to maintain the time interval between the prediction points. After that, the control device 28 proceeds to step S111.

[0060] In step S111, the control device 28 generates prediction points based on the time intervals between prediction points determined in step S109 or step S110. After that, the control device 28 proceeds to step S112.

[0061] In step S112, the control device 28 predicts the future target operating state of the work machine 100 (particularly the work device 24) based on the prediction points generated in step S111. After that, the control device 28 proceeds to step S113.

[0062] In step S113, the control device 28 generates an operation command for the actuator 35 according to the target operating state predicted in step S112. After that, the control device 28 proceeds to step S114.

[0063] In step S114, the control device 28 controls the actuator 35 in accordance with the operation command generated in step S113. After that, the control device 28 completes the process shown in Figure 5.

[0064] As described above, the work machine 100 of the first embodiment includes a bucket 10 which is a work tool, a multi-jointed work device 24 which is rotatably mounted on the vehicle body 20, 22, an actuator 35 which drives the work device 24, a posture sensor 26 which detects posture information of the work device 24, a storage device 29 which stores design information including the coordinates of a design surface 40 which represents the target shape of the work object, and a control device 28 which controls the operation of the actuator 35. The control device 28 has a coordinate calculation unit 30 which calculates the coordinates of the tip of the bucket 10 based on the posture information, and a speed calculation unit 31 which calculates the moving speed of the tip of the bucket 10 based on the coordinates of the tip of the bucket 10 calculated by the coordinate calculation unit 30. The control device 28 has a prediction point generation unit 32 which generates prediction points that represent the positions to which the bucket 10 is predicted to reach in each control cycle when a predetermined arbitrary control cycle arrives in the future, based on the coordinates of the tip of the bucket 10, the moving speed of the tip of the bucket 10 and the design information. The control device 28 has a design surface determination unit 36 ​​that determines change points 39 in which the shape of the design surface 40 changes, based on design information. The control device 28 has a prediction point interval adjustment unit 37 that adjusts the time interval of the control cycle so that the distance between prediction points generated near the change points 42 of the design surface 40 when the prediction point generation unit 32 generates prediction points for the bucket 10 is shortened, based on the coordinates of the tip of the bucket 10, the movement speed of the tip of the bucket 10, the change points 39, and design information. The control device 28 has an operation generation unit 33 that generates operation commands for the actuator 35 so that the bucket 10 moves in accordance with the time-interval-adjusted prediction points, based on the time-interval-adjusted prediction points, the coordinates of the tip of the bucket 10, and design information. The control device 28 has an actuator control unit 34 that controls the operation of the actuator 35 based on the operation commands generated by the operation generation unit 33.

[0065] As a result, the work machine 100 of the first embodiment can ensure work accuracy without increasing the computational load, while suppressing a decrease in work efficiency.

[0066] [Second Embodiment] A second embodiment of the present invention will be described with reference to Figures 6 to 8. In the second embodiment, the same components as in the first embodiment will not be described.

[0067] In the second embodiment, if a change point 39 exists near the end of the prediction range, the prediction range is extended to include the area near the change point 42, and an operation command is generated while taking into account the shape change of the design surface 40.

[0068] Figure 6 is a block diagram illustrating the functions of the control device 28 in the second embodiment.

[0069] The control device 28 of the second embodiment has a prediction range adjustment unit 38. If a change point 39 exists outside the predetermined prediction range but near the end of the prediction range, the prediction range adjustment unit 38 extends the prediction range so that the change point 39 is included within the prediction range. The prediction range adjustment unit 38 extends the prediction range based on the coordinates of the representative point calculated by the coordinate calculation unit 30, the moving speed of the tip of the bucket 10 calculated by the velocity calculation unit 31, the work / design information stored in the storage device 29, and the determination result of the design surface determination unit 36. The prediction range adjustment unit 38 extends the prediction range so that the total number of prediction points included in the prediction range is less than or equal to a predetermined upper limit. The prediction range adjustment unit 38 transmits the length of the prediction range, i.e., the number of control cycles designated as the prediction range (number of prediction horizons), to the prediction point interval adjustment unit 37 and the prediction point generation unit 32. The prediction point interval adjustment unit 37 adjusts the time interval between prediction points generated near the change point 42 included within the extended prediction range. Details of the prediction range adjustment unit 38 will be described later.

[0070] Figure 7 is a schematic diagram illustrating the arrangement of prediction points when the design surface 40 changes from a horizontal surface to an inclined surface. Figure 7 is a diagram that assumes the extension of the prediction range during slope shoulder excavation.

[0071] If the design surface determination unit 36 ​​determines that "there is a change in the shape of the design surface 40", and a change point 39 exists outside the predetermined prediction range 46 but near the end point of the prediction range 46 (time t4 in Figure 7), the prediction range adjustment unit 38 extends the predetermined prediction range 46 so that the change point 39 is included in the prediction range. In the example in Figure 7, the prediction range adjustment unit 38 extends the predetermined prediction range 46 to the range 47 that includes the prediction points at times t5 and t6. The prediction range adjustment unit 38 transmits the lengths of the extended prediction ranges 46 and 47 to the prediction point interval adjustment unit 37 and the prediction point generation unit 32.

[0072] By extending the prediction range in this way, the control device 28 of the second embodiment can generate operation commands while predicting in advance that the shape of the design surface 40 will change in the future, and can operate the bucket 10 with high precision while preventing the bucket 10 from missing its target near the change point 42. The other configurations of the control device 28 of the second embodiment are the same as those of the first embodiment.

[0073] Figure 8 is a flowchart showing the processing steps of the control device 28 shown in Figure 6. The processing steps from start to end in this flowchart are performed by the control device 28 at each calculation step.

[0074] In steps S201 to S207, the control device 28 performs the same processing as in steps S101 to S107 shown in Figure 5. However, if it is determined in step S206 that "there is a change in the shape of the design surface 40", the control device 28 proceeds to step S207. If it is determined that "there is no change in the shape of the design surface 40", the control device 28 proceeds to step S213.

[0075] In step S208, the control device 28 determines whether the change point 39 is outside the predetermined prediction range but near the end of the prediction range. If the change point 39 is outside the predetermined prediction range but near the end of the prediction range, the control device 28 proceeds to step S209. If the change point 39 is not outside the predetermined prediction range but near the end of the prediction range, the control device 28 proceeds to step S210.

[0076] In step S209, the control device 28 extends the predetermined prediction range so that the change point 39 is included within the prediction range. After that, the control device 28 proceeds to step S211.

[0077] In step S210, the control device 28 decides to maintain the prediction range. Subsequently, the control device 28 proceeds to step S211.

[0078] In steps S211 and S212, the control device 28 performs the same processing as in steps S108 and S109 shown in Figure 5.

[0079] In step S213, the control device 28 decides to maintain the prediction range. Subsequently, the control device 28 proceeds to step S214.

[0080] In step S214, the control device 28 decides to maintain the time interval between prediction points. After that, the control device 28 proceeds to step S215.

[0081] In steps S215 to S218, the control device 28 performs the same processing as in steps S111 to S114 shown in Figure 5. After that, the control device 28 terminates the processing shown in Figure 8.

[0082] The control device 28 of the second embodiment, configured as described above, can achieve the same effects as the first embodiment. Furthermore, the control device 28 of the second embodiment extends the prediction range depending on whether the change point 39 is outside the prediction range and located near the end of the prediction range. This makes it possible to generate operation commands while predicting in advance that the shape of the design surface 40 will change in the future, and to operate the bucket 10 with high precision in accordance with the shape changes of the design surface 40.

[0083] [Note] The present invention is not limited to the embodiments described above, and various modifications are included. For example, the embodiments described above are described in detail to make the present invention easier to understand, and are not necessarily limited to those comprising all the components described. Furthermore, it is possible to replace some of the components of one embodiment with components of another embodiment, and it is also possible to add components of another embodiment to the components of one embodiment. In addition, it is possible to add, delete, or replace some of the components of each embodiment with components of other embodiments.

[0084] Furthermore, each of the above-mentioned components, functions, processing units, or processing means may be implemented in hardware, in whole or in part, for example, by designing them as integrated circuits. Alternatively, each of the above-mentioned components or functions may be implemented in software by a processor interpreting and executing programs that implement each function. Information such as programs, tables, or files that implement each function can be stored in a recording device such as memory, a hard disk, or an SSD (solid state drive), or in a recording medium such as an IC card, SD card, or DVD.

[0085] Furthermore, the control lines and information lines shown are those deemed necessary for explanatory purposes, and not all control lines and information lines are necessarily shown in the actual product. In reality, it can be assumed that almost all components are interconnected.

[0086] 20...Lower traveling body, 22...Upper rotating body, 24...Working device, 26...Attitude sensor, 28...Control device, 29...Storage device, 30...Coordinate calculation unit, 31...Velocity calculation unit, 32...Prediction point generation unit, 33...Motion generation unit, 34...Actuator control unit, 35...Actuator, 36...Design surface determination unit, 37...Prediction point interval adjustment unit, 38...Prediction range adjustment unit, 39...Change point, 40...Design surface, 41...Operating device, 42...Near change point, 43...Unchanged range, 100...Working machine

Claims

1. A multi-joint work device including a work tool and rotatably mounted to the vehicle body; an actuator for driving the work device; a posture sensor for detecting posture information of the work device; a storage device for storing design information including coordinates of a design surface representing the target shape of the work object; and a control device for controlling the operation of the actuator, wherein the control device comprises: a coordinate calculation unit for calculating the coordinates of the tip of the work tool based on the posture information; a speed calculation unit for calculating the moving speed of the tip of the work tool based on the coordinates of the work tool calculated by the coordinate calculation unit; a prediction point generation unit for generating prediction points representing positions that the work tool is expected to reach in each control cycle when a predetermined arbitrary control cycle arrives in the future, based on the coordinates of the work tool, the moving speed of the work tool, and the design information; and a design surface determination unit for determining change points where the shape of the design surface changes based on the design information. A work machine characterized by comprising: a prediction point interval adjustment unit that adjusts the time interval of the control cycle so that the interval between prediction points generated near the change points on the design surface when the prediction points of the work tool are generated by the prediction point generation unit is shortened, based on the coordinates of the work tool, the movement speed of the work tool, the change points on the design surface, and the design information; an operation generation unit that generates an operation command for the actuator so that the work tool moves in accordance with the prediction points whose time interval has been adjusted, based on the prediction points generated by the time interval adjustment, the coordinates of the work tool, and the design information; and an actuator control unit that controls the operation of the actuator based on the operation command generated by the operation generation unit.

2. The work machine according to claim 1, characterized in that the design surface determination unit determines an unchanged range in which the shape of the design surface does not change, and the prediction point interval adjustment unit extends the time interval between the prediction points generated in the unchanged range and shortens the time interval between the prediction points generated near the change point.

3. The work machine according to claim 1, characterized in that the prediction point interval adjustment unit adjusts the time interval between the prediction points so that the prediction points generated near the change point are assigned to the change point.

4. The work machine according to claim 1, wherein the prediction point generation unit generates prediction points over a prediction range which is the range from the present time to the time when a predetermined arbitrary control cycle arrives, the control device further has a prediction range adjustment unit which adjusts the prediction range, the prediction range adjustment unit extends the prediction range so that the change point is included in the prediction range when the change point is outside the predetermined prediction range but near the end of the prediction range, and the prediction point interval adjustment unit adjusts the time interval between the prediction points that are generated near the change point included in the extended prediction range.

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