Control system for a work machine and control method for a work machine

Abstract

To automatically control a work machine so as to move a tilt bucket along a target design surface.SOLUTION: A distance calculation unit calculates a first distance which is a distance between a first bucket point that is a point on a bucket and a target design surface indicating a target shape as an excavation object. The distance calculation unit calculates a second distance which is a distance between a second bucket point that is a point on the bucket on a straight line that passes through the first bucket and is parallel to a tip of the bucket and the target design surface. A tilt control unit compares the first distance with the second distance, and calculates a tilt control amount rotating the bucket around a tilt axis.SELECTED DRAWING: Figure 7

Description

[[Technical Field]]

[0001] The present disclosure relates to a control system for a work machine, a work machine, and a control method for a work machine. [[Background Art]]

[0002] As a bucket attached to a hydraulic excavator, a tilt bucket capable of adjusting an angle with respect to the operation plane of a work implement is known (see, for example, Patent Document 1). The tilt bucket is configured to be rotatable about a bucket axis orthogonal to the operation plane, and rotatable about a tilt axis orthogonal to the bucket axis. [[Prior Art Documents]] [[Patent Documents]]

[0003] [[Patent Document 1]] Japanese Unexamined Patent Application Publication No. 2014-74319 [[Summary of the Invention]] [[Problem to be Solved by the Invention]]

[0004] Incidentally, in a work machine such as a hydraulic excavator, a technique of automatically controlling a work implement such that a bucket moves along a target design surface indicating a target shape of an excavation object is known. Even for the tilt bucket disclosed in Patent Document 1, it is desired to automatically control the work implement such that the tilt bucket moves along the target design surface. An object of the present disclosure is to provide a control system for a work machine, a work machine, and a control method for a work machine, which automatically control a work implement such that a tilt bucket moves along a target design surface. [[Means for Solving the Problem]]

[0005] According to one embodiment, the control system for a work machine comprises a boom rotatable around a boom axis, an arm rotatable around an arm axis parallel to the boom axis, and a bucket rotatable around a bucket axis parallel to the arm axis and rotatable around a tilt axis perpendicular to the bucket axis, the control system for a work machine comprising: a distance calculation unit that calculates a first distance which is the distance between a first bucket point, which is a point on the bucket, and a target design surface indicating the target shape of the object to be excavated, and a second distance which is the distance between a second bucket point, which is a point on the bucket on a straight line passing through the first bucket point and parallel to the cutting edge of the bucket, and the target design surface, and a tilt control unit that calculates a tilt control amount for rotating the bucket around the tilt axis based on at least the larger of the first distance and the second distance. [Effects of the Invention]

[0006] According to the above embodiment, the control system for the work machine can automatically control the work machine so that the tilt bucket moves along the target design plane. [Brief explanation of the drawing]

[0007] [Figure 1] This figure shows examples of the posture of work machines and work equipment. [Figure 2] This is a schematic diagram showing the configuration of a work machine according to the first embodiment. [Figure 3] This is a front view showing the configuration of a bucket according to the first embodiment. [Figure 4] This diagram shows the internal configuration of the driver's cab according to the first embodiment. [Figure 5] This is a schematic block diagram showing the configuration of the control device according to the first embodiment. [Figure 6] This is a flowchart showing the operation of the control device according to the first embodiment. [Figure 7] This diagram shows the relationship between the target design plane and a point on the cutting edge in automatic tilt control. [Figure 8]This figure shows an example of a tilt function illustrating the relationship between the distance difference of the buckets and the target value of the tilt angular velocity according to the first embodiment. [Modes for carrying out the invention]

[0008] <Coordinate system> Figure 1 shows examples of the postures of the work machine 100 and work machine 150. In the following explanation, we define a three-dimensional field coordinate system (Xg, Yg, Zg) and a three-dimensional vehicle body coordinate system (Xm, Ym, Zm), and explain the positional relationships based on these.

[0009] The site coordinate system is a coordinate system consisting of an Xg axis extending north-south, a Yg axis extending east-west, and a Zg axis extending vertically, with the position of the GNSS (Global Navigation Satellite System) reference station installed at the construction site as the reference point. An example of GNSS is GPS (Global Positioning System). In other embodiments, a global coordinate system expressed by latitude and longitude may be used instead of the site coordinate system. The vehicle body coordinate system is a coordinate system based on a representative point O defined on the slewing body 130 of the work machine 100, and consists of the Xm axis extending forward and backward, the Ym axis extending left and right, and the Zm axis extending up and down, as viewed from the operator's seating position in the cab 170 described later. With the representative point O of the slewing body 130 as the reference point, the forward direction is called the +Xm direction, the backward direction is called the -Xm direction, the left direction is called the +Ym direction, the right direction is called the -Ym direction, the upward direction is called the +Zm direction, and the downward direction is called the -Zm direction. The site coordinate system and the vehicle coordinate system can be converted to each other by specifying the position and inclination of the work machine 100 in the site coordinate system.

[0010] <First Embodiment> 《Configuration of the 100th work machine》 Figure 2 is a schematic diagram showing the configuration of the work machine 100 according to the first embodiment. The work machine 100 operates at the construction site and performs excavation work on materials such as soil and sand. The work machine 100 according to the first embodiment is a hydraulic excavator. The work machine 100 comprises a traveling body 110, a rotating body 130, a work implement 150, a driver's cab 170, and a control device 190. The traveling body 110 supports the work machine 100 so that it can move. The traveling body 110 is, for example, a pair of endless tracks on the left and right. The slewing body 130 is supported on the traveling body 110 so that it can slewing around a pivot point. The work machine 150 is hydraulically driven. The work machine 150 is supported on the front of the slewing body 130 so that it can be driven vertically. The cab 170 is a space for the operator to sit in and operate the work machine 100. The cab 170 is located on the front of the slewing body 130. The control device 190 controls the traveling body 110, the slewing body 130, and the work machine 150 based on the operator's input. The control device 190 is located, for example, inside the cab 170.

[0011] 《Configuration of the rotating body 130》 As shown in Figure 2, the rotating body 130 is equipped with a position and orientation detector 131 and a tilt detector 132.

[0012] The position and direction detector 131 calculates the position of the slewing body 130 in the field coordinate system and the direction in which the slewing body 130 is facing. The position and direction detector 131 is equipped with two antennas that receive positioning signals from satellites that constitute the GNSS. The two antennas are installed at different positions on the slewing body 130. For example, the two antennas are installed on the counterweight portion of the slewing body 130. Based on the positioning signals received by at least one of the two antennas, the position and direction detector 131 detects the position of the representative point O of the slewing body 130 in the field coordinate system. Using the positioning signals received by each of the two antennas, the position and direction detector 131 detects the direction in which the slewing body 130 is facing in the field coordinate system.

[0013] The tilt detector 132 measures the acceleration and angular velocity of the revolving superstructure 130, and detects the tilt of the revolving superstructure 130 (for example, roll representing rotation about the Xm axis, and pitch representing rotation about the Ym axis) based on the measurement results. The tilt detector 132 is installed, for example, below the operator's cab 170. An example of the tilt detector 132 is an IMU (Inertial Measurement Unit).

[0014] 《Configuration of Working Machine 150》 As shown in Figure 2, the working machine 150 includes a boom 151, an arm 152, a first link 153, a second link 154, and a bucket 155.

[0015] The base end portion of the boom 151 is attached to the revolving superstructure 130 via a boom pin P1. Hereinafter, the central axis of the boom pin P1 is referred to as a boom axis X1. The arm 152 connects the boom 151 and the bucket 155. The base end portion of the arm 152 is attached to the distal end portion of the boom 151 via an arm pin P2. Hereinafter, the central axis of the arm pin P2 is referred to as an arm axis X2. A first end of the first link 153 is attached to a distal end side side surface of the arm 152 via a first link pin P3. A second end of the first link 153 is attached to a first end of the second link 154 via a bucket cylinder pin P4. The bucket 155 includes a cutting edge for excavating earth and sand and the like, and an accommodating portion for accommodating the excavated earth and sand. The base end portion of the bucket 155 is attached to the distal end portion of the arm 152 via a bucket pin P5. Hereinafter, the central axis of the bucket pin P5 is referred to as a bucket axis X3. The base end portion of the bucket 155 is also attached to the second end of the second link 154 via a second link pin P6. The boom axis X1, the arm axis X2, and the bucket axis X3 are parallel to each other.

[0016] The work machine 150 is equipped with multiple hydraulic cylinders, which are actuators that generate power. Specifically, the work machine 150 is equipped with a boom cylinder 156, an arm cylinder 157, and a bucket cylinder 158. The boom cylinder 156 is a hydraulic cylinder for driving the boom 151. The base end of the boom cylinder 156 is attached to the slewing body 130. The tip end of the boom cylinder 156 is attached to the boom 151. The boom cylinder 156 is equipped with a boom cylinder stroke sensor 1561 for detecting the stroke amount of the boom cylinder 156. The arm cylinder 157 is a hydraulic cylinder for driving the arm 152. The base end of the arm cylinder 157 is attached to the boom 151. The tip end of the arm cylinder 157 is attached to the arm 152. The arm cylinder 157 is equipped with an arm cylinder stroke sensor 1571 for detecting the stroke amount of the arm cylinder 157. The bucket cylinder 158 is a hydraulic cylinder for driving the bucket 155. The base end of the bucket cylinder 158 is attached to the arm 152. The tip end of the bucket cylinder 158 is attached to the second end of the first link 153 and the first end of the second link 154 via a second link pin P6. The bucket cylinder 158 is equipped with a bucket cylinder stroke sensor 1581 for detecting the stroke amount of the bucket cylinder 158.

[0017] 《Configuration of Bucket 155》 Figure 3 is a front view showing the configuration of the bucket 155 according to the first embodiment. The bucket 155 according to the first embodiment is a tilt bucket that can rotate around a tilt axis X4, which is an axis perpendicular to the bucket axis X3. As shown in Figure 3, the bucket 155 comprises a bucket body 161, a joint 162, and a tilt cylinder 163.

[0018] The base end of the joint 162 is provided with a front bracket 1621 having a mounting hole for attaching the arm 152 via a bucket pin P5, and a rear bracket 1622 having a mounting hole for attaching the second link 154 via a second link pin P6. That is, the mounting hole of the front bracket 1621 is provided so as to pass through the bucket axis X3. The tip of the joint 162 is attached to the base end of the bucket body 161 via a tilt pin P7. The tilt pin P7 is provided so as to be perpendicular to the bucket axis X3. The central axis of the tilt pin P7 forms the tilt axis X4.

[0019] A tilt bracket 1611 for attaching a tilt cylinder 163 is provided at one end (left or right) of the base end of the bucket body 161. The tilt cylinder 163 is a hydraulic cylinder for rotating the bucket body 161 around the tilt axis X4. The base end of the tilt cylinder 163 is attached to the tilt bracket 1611 via the tilt cylinder end pin P8. The tip end of the tilt cylinder 163 is attached to the joint 162 via the tilt cylinder top pin P9. The tilt cylinder end pin P8 and the tilt cylinder top pin P9 are each provided parallel to the tilt pin P7. As a result, the bucket body 161 rotates around the tilt axis X4 by the drive of the tilt cylinder 163. The tilt cylinder 163 is equipped with a tilt cylinder stroke sensor 1631 that detects the stroke amount of the tilt cylinder 163.

[0020] 《Configuration of the driver's cab 170》 Figure 4 shows the internal configuration of the driver's cab according to the first embodiment. As shown in Figure 4, the driver's cab 170 is equipped with a driver's seat 171, an operating device 172, and a control device 190.

[0021] The control device 172 is an interface for driving the traveling body 110, the slewing body 130, and the work implement 150 by manual operation by the operator. The control device 172 includes a left control lever 1721, a right control lever 1722, a left foot pedal 1723, a right foot pedal 1724, a left travel lever 1725, and a right travel lever 1726.

[0022] The left control lever 1721 is located on the left side of the driver's seat 171. The right control lever 1722 is located on the right side of the driver's seat 171.

[0023] The left operating lever 1721 is an operating mechanism for controlling the rotation of the slewing body 130, as well as the pulling and pushing movements of the arm 152. Specifically, when the operator pushes the left operating lever 1721 forward, the arm cylinder 157 is activated, causing the arm 152 to push. When the operator pushes the left operating lever 1721 backward, the arm cylinder 157 is activated, causing the arm 152 to pull. When the operator pushes the left operating lever 1721 to the right, the slewing body 130 rotates to the right. When the operator pushes the left operating lever 1721 to the left, the slewing body 130 rotates to the left.

[0024] The right operating lever 1722 is an operating mechanism for performing the digging and dumping operations of the bucket 155, as well as the raising and lowering operations of the boom 151. Specifically, when the operator pushes the right operating lever 1722 forward, the boom cylinder 156 is driven, and the boom 151 is lowered. When the operator pushes the right operating lever 1722 backward, the boom cylinder 156 is driven, and the boom 151 is raised. When the operator pushes the right operating lever 1722 to the right, the bucket cylinder 158 is driven, and the bucket 155 is dumped. When the operator pushes the right operating lever 1722 to the left, the bucket cylinder 158 is driven, and the bucket 155 is dug. Note that the relationship between the operating direction of the left operating lever 1721 and the right operating lever 1722 and the operating direction of the work machine 150 and the slewing direction of the slewing body 130 does not have to be as described above.

[0025] Furthermore, a tilt control button (not shown) is provided on the upper part of the right operating lever 1722. Specifically, when the operator slides the tilt control button to the left, the tilt cylinder 163 is driven, causing the bucket 155 to tilt and rotate to the left from the operator's perspective. When the operator slides the tilt control button to the right, the tilt cylinder 163 is driven, causing the bucket 155 to tilt and rotate to the right from the operator's perspective. The tilt control button may also be configured to rotate in the left and right directions. In addition, the tilt operation may be achieved by operating a pedal (not shown) by the operator.

[0026] The left foot pedal 1723 is located on the left side of the floor in front of the driver's seat 171. The right foot pedal 1724 is located on the right side of the floor in front of the driver's seat 171. The left travel lever 1725 is pivotally supported by the left foot pedal 1723, and the tilt of the left travel lever 1725 is linked to the downward movement of the left foot pedal 1723. The right travel lever 1726 is pivotally supported by the right foot pedal 1724, and the tilt of the right travel lever 1726 is linked to the downward movement of the right foot pedal 1724.

[0027] The left foot pedal 1723 and the left travel lever 1725 correspond to the rotational drive of the left track of the vehicle 110. Specifically, when the drive wheels of the vehicle 110 are at the rear, when the operator pushes the left foot pedal 1723 or the left travel lever 1725 forward, the left track rotates in the forward direction. Conversely, when the operator pushes the left foot pedal 1723 or the left travel lever 1725 backward, the left track rotates in the reverse direction.

[0028] The right foot pedal 1724 and the right travel lever 1726 correspond to the rotational drive of the right track of the vehicle 110. Specifically, when the drive wheels of the vehicle 110 are at the rear, when the operator pushes the right foot pedal 1724 or the right travel lever 1726 forward, the right track rotates in the forward direction. Conversely, when the operator pushes the right foot pedal 1724 or the right travel lever 1726 backward, the right track rotates in the reverse direction.

[0029] Configuration of the control device 190 The control device 190 restricts the movement of the bucket 155 in the direction that would cause it to approach the excavation target, so that the bucket 155 does not enter the target design plane set at the construction site. The target design plane indicates the target shape of the excavation target. The control device 190 restricting the movement of the bucket 155 based on the target design plane is also called intervention control.

[0030] This section describes intervention control when an operator performs leveling work at a construction site by only pulling the arm 152. When the distance between the bucket 155 and the target design surface falls below a predetermined intervention control distance, the control device 190 generates an operation signal for the boom cylinder 156, according to the distance between the tip of the bucket 155 and the target design surface as the arm 152 moves, to prevent the bucket 155 from entering the target design surface. As a result, the control device 190 generates an operation signal for the boom cylinder 156 and automatically raises the boom 151 by simply operating the arm 152, thereby restricting the movement of the bucket 155 and automatically preventing the tip of the bucket 155 from entering the design surface. In other embodiments, the control device 190 may generate a control command for the arm cylinder 157 or a control command for the bucket cylinder 158 during intervention control. In other embodiments, the speed of the bucket 155 may be limited by raising the arm 152 during intervention control, or the speed of the bucket 155 may be limited directly.

[0031] Furthermore, when the distance between the bucket 155 and the target design surface falls below a predetermined tilt control distance, the control device 190 rotates the bucket 155 around the tilt axis X4 so that the cutting edge of the bucket 155 becomes parallel to the target design surface. The rotation of the bucket 155 around the tilt axis X4 by the control device 190 based on the target design surface is also called automatic tilt control.

[0032] Figure 5 is a schematic block diagram showing the configuration of the control device 190 according to the first embodiment. The control device 190 is a computer comprising a processor 210, main memory 230, storage 250, and interface 270.

[0033] The storage 250 is a tangible, non-temporary storage medium. Examples of the storage 250 include magnetic disks, optical disks, magneto-optical disks, and semiconductor memory. The storage 250 may be an internal medium directly connected to the bus of the control device 190, or an external medium connected to the control device 190 via the interface 270 or a communication line. The storage 250 stores a program for controlling the work machine 100.

[0034] The program may be for implementing a part of the functions to be performed by the control device 190. For example, the program may perform functions in combination with other programs already stored in the storage 250, or in combination with other programs implemented in other devices. In other embodiments, the control device 190 may include a custom LSI (Large Scale Integrated Circuit) such as a PLD (Programmable Logic Device) in addition to, or instead of, the above configuration. Examples of PLDs include PAL (Programmable Array Logic), GAL (Generic Array Logic), CPLD (Complex Programmable Logic Device), and FPGA (Field Programmable Gate Array). In this case, some or all of the functions implemented by the processor may be implemented by the integrated circuit.

[0035] The storage 250 stores design plane data that represents the target design plane in advance. The design plane data is three-dimensional data expressed in the field coordinate system and is represented by multiple triangular polygons. Each triangular polygon that makes up the design plane data has a common edge with other adjacent triangular polygons. In other words, the design plane data represents a continuous plane composed of multiple planes. In other embodiments, the design plane data may be composed of polygonal faces other than triangular polygons, or it may be represented in other formats such as point cloud data. In this embodiment, the design surface data is stored in storage 250, but this is not limited to that. The design surface data may also be downloaded from external memory or from a server (not shown) via a communication line (not shown).

[0036] The processor 210, by executing a program, functions as a detection value acquisition unit 211, a bucket position identification unit 212, a target plane determination unit 213, a distance calculation unit 214, a manipulated variable acquisition unit 215, an intervention control unit 216, a tilt control unit 217, and an output unit 218.

[0037] The detection value acquisition unit 211 acquires the detection values ​​of the boom cylinder stroke sensor 1561, arm cylinder stroke sensor 1571, bucket cylinder stroke sensor 1581, tilt cylinder stroke sensor 1631, position and orientation detector 131, and tilt detector 132. In other words, the detection value acquisition unit 211 acquires the position of the slewing body 130 in the field coordinate system, the orientation that the slewing body 130 is facing, the tilt of the slewing body 130, the stroke length of the boom cylinder 156, the stroke length of the arm cylinder 157, the stroke length of the bucket cylinder 158, and the stroke length of the tilt cylinder 163.

[0038] The bucket position identification unit 212 identifies the positions of multiple points on the cutting edge of the bucket 155 based on the detected values ​​acquired by the detected value acquisition unit 211. For example, the bucket position identification unit 212 identifies the positions of five points that divide the cutting edge of the bucket 155 into four equal parts. The method for identifying the position of the cutting edge of the bucket 155 will be described later.

[0039] The target plane determination unit 213 determines the target plane to be subjected to tilt control. The target plane is a plane that passes through at least one of the multiple triangular polygons that constitute the target design plane. Specifically, the target plane determination unit 213 determines the target plane in the following procedure. Based on the design plane data and the positions of multiple points identified by the bucket position identification unit 212, the target plane determination unit 213 calculates the distance between each of the multiple points and the triangular polygon that is opposite to that point among the triangular polygons that constitute the target design plane. At this time, each of the multiple points may be opposite to a different triangular polygon. The target plane determination unit 213 identifies the triangular polygon with the shortest distance and determines the plane passing through that triangular polygon as the target plane.

[0040] The distance calculation unit 214 calculates the distance between the multiple points and the target plane based on the positions of the multiple points identified by the bucket position identification unit 212 and the target plane determined by the target plane determination unit 213.

[0041] The operation amount acquisition unit 215 acquires operation signals indicating the operation amount from the operation device 172. The operation amount acquisition unit 215 acquires at least the operation amounts related to the raising and lowering of the boom 151, the operation amounts related to the pushing and pulling of the arm 152, and the operation amounts related to the digging, dumping, and tilting of the bucket 155.

[0042] The intervention control unit 216 performs intervention control of the work machine 150 based on the shortest of the manipulated amount of the operating device 172 acquired by the manipulated amount acquisition unit 215 and the distance calculated by the distance calculation unit 214.

[0043] The tilt control unit 217 performs automatic tilt control based on the difference between a first distance, which is the distance from the left end of the cutting edge of the bucket 155 to the target plane, and a second distance, which is the distance from the right end of the cutting edge of the bucket 155 to the target plane, among the distances calculated by the distance calculation unit 214. The left and right ends of the cutting edge of the bucket 155 are examples of the first bucket point and the second bucket point, respectively. In other embodiments, the first bucket point and the second bucket point may be other points on the bucket 155. However, the second bucket point must satisfy the condition that it lies on a straight line that passes through the first bucket point and is parallel to the cutting edge of the bucket 155. In other embodiments, the first bucket point and the second bucket point may not necessarily be points on the cutting edge, such as points on the bottom surface.

[0044] The output unit 218 outputs control signals to each actuator based on the manipulated amount acquired by the manipulated amount acquisition unit 215 and the tilt control amount calculated by the tilt control unit 217.

[0045] Method for determining the cutting edge position of bucket 155 Here, with reference to Figures 1 and 3, the method for determining the position of the cutting edge of the bucket 155 by the bucket position determination unit 212 will be described. The position of the cutting edge of the bucket 155 in the vehicle body coordinate system can be determined based on the boom length L1, arm length L2, joint length L3, bucket length L4, boom relative angle α, arm relative angle β, bucket relative angle γ, tilt angle η, the position of the boom pin P1 in the vehicle body coordinate system, and the position of the representative point O in the field coordinate system.

[0046] The boom length L1 is the known length from the boom pin P1 to the arm pin P2. The arm length L2 is the known length from the arm pin P2 to the bucket pin P3. The joint length L3 is the known length from bucket pin P3 to tilt pin P7. The bucket length L4 is the known length from tilt pin P7 to the center point of the cutting edge of bucket 155.

[0047] The boom relative angle α is represented by the angle between the half-line extending upward (+Zm direction) from the boom pin P1 to the slewing body 130 and the half-line extending from the boom pin P1 to the arm pin P2. Note that, as shown in Figure 1, the upward direction (+Zm direction) and the vertically upward direction (+Zg direction) of the slewing body 130 do not necessarily coincide due to the inclination θ of the slewing body 130. The relative arm angle β is expressed by the angle between the half-line extending from boom pin P1 to arm pin P2 and the half-line extending from arm pin P2 to bucket pin P3. The relative angle γ of the bucket is expressed by the angle between the half-line extending from arm pin P2 to bucket pin P3 and the half-line extending from bucket pin P3 to tilt pin P7. The tilt angle η is represented by the angle between a half-line extending from the tilt pin P7 in a direction perpendicular to both the bucket pin P3 and the tilt pin P7, and a half-line extending from the tilt pin P7 to the center point of the cutting edge of the bucket 155.

[0048] The position of the cutting edge of the bucket 155 in the field coordinate system is determined, for example, by the following procedure. The bucket positioning unit 212 determines the position of the arm pin P2 in the vehicle coordinate system based on the position of the boom pin P1, the boom relative angle α, and the boom length L1 in the vehicle coordinate system. The bucket positioning unit 212 determines the position of the bucket pin P3 in the vehicle coordinate system based on the position of the arm pin P2, the arm relative angle β, and the arm length L2 in the vehicle coordinate system. The bucket positioning unit 212 determines the position of the tilt pin P7 in the vehicle coordinate system based on the position of the bucket pin P3, the bucket relative angle γ, and the joint length L3 in the vehicle coordinate system. The bucket positioning unit 212 determines the position of the center point of the cutting edge of the bucket 155 in the vehicle coordinate system based on the position of the tilt pin P7, the tilt angle η, and the bucket length L4 in the vehicle coordinate system. Furthermore, the bucket position identification unit 212 can identify the position of any point on the cutting edge by determining the distance from the center point of the cutting edge to any point on the cutting edge, and by calculating a position shifted from the position of the center point of the cutting edge by the distance from the center point of the cutting edge in the direction of the tilt angle η. For example, the bucket position identification unit 212 can identify the positions of both ends of the cutting edge by calculating a position shifted from the position of the center point of the cutting edge by half the length of the width of the cutting edge in both the positive and negative directions of the tilt angle η.

[0049] The boom relative angle α, arm relative angle β, bucket relative angle γ, and tilt angle η are determined by the values ​​detected by the boom cylinder stroke sensor 1561, arm cylinder stroke sensor 1571, bucket cylinder stroke sensor 1581, and tilt cylinder stroke sensor 1631, respectively. The bucket positioning unit 212 converts the position of the cutting edge of the bucket 155 in the vehicle coordinate system to its position in the field coordinate system, based on the position of the slewing body 130 in the field coordinate system, the direction the slewing body 130 is facing, and the attitude of the slewing body 130. Furthermore, the detection of the boom relative angle α, arm relative angle β, bucket relative angle γ, and tilt angle η is not limited to being performed by a cylinder stroke sensor, but may also be performed by an angle sensor or an IMU.

[0050] Operation of the control device 190 Figure 6 is a flowchart showing the operation of the control device 190 according to the first embodiment. Figure 7 is a diagram showing the relationship between the target design surface and a point on the cutting edge in tilt automatic control. When the operator of the work machine 100 starts operating the work machine 100, the control device 190 executes the following control at predetermined control cycles.

[0051] The operation amount acquisition unit 215 acquires the operation amounts related to the boom 151, the arm 152, the bucket 155, the tilt, and the rotation of the slewing body 130 from the operating device 172 (step S1). The detection value acquisition unit 211 acquires the information detected by each of the position and orientation detector 131, the tilt detector 132, the boom cylinder stroke sensor 1561, the arm cylinder stroke sensor 1571, the bucket cylinder stroke sensor 1581, and the tilt cylinder stroke sensor 1631 (step S2).

[0052] The bucket positioning unit 212 calculates the boom relative angle α, arm relative angle β, bucket relative angle γ, and tilt angle η from the stroke length of each hydraulic cylinder (step S3). The bucket positioning unit 212 also calculates the positions in the field coordinate system of five points that divide the cutting edge of the bucket 155 into four equal parts, based on the detected values ​​obtained in step S2, the angles calculated in step S3, and the known length parameters of the work machine 150 (step S4). Hereinafter, the five points on the cutting edge of the bucket 155 will be called points p1, p2, p3, p4, and p5, in order from the left end of the cutting edge. That is, point p1 is the left end of the cutting edge, point p5 is the right end of the cutting edge, and point p3 is the center point of the cutting edge. If the angle is detected directly using an angle sensor or IMU, step S3 may be omitted.

[0053] The target plane determination unit 213 reads design plane data from the storage 250 and calculates the distance between each of points p1-p5 and the target design plane (step S5). In step S5, the target plane determination unit 213 calculates the distance for each of points p1-p5 to the opposing triangular polygon in the direction extending vertically (Zg axis direction) from that point. In the example shown in Figure 7, the target plane determination unit 213 calculates the distances L11-L13 between points p1-p3 and triangular polygon t1, and the distances L14-L15 between points p4-p5 and triangular polygon t2. If the position of the cutting edge of the bucket 155 is determined in the field coordinate system, design plane data based on the field coordinate system is used. If the position of the cutting edge of the bucket 155 is determined in the vehicle coordinate system, design plane data based on the vehicle coordinate system may be used. For example, design surface data based on the vehicle body coordinate system may be obtained by converting design surface data based on the field coordinate system to the vehicle body coordinate system based on the detection values ​​of the position and orientation detector 131 and the tilt detector 132.

[0054] Next, the target plane determination unit 213 identifies the triangular polygon with the shortest distance and determines the plane passing through that triangular polygon as the target plane g1 (step S6). In the example shown in Figure 7, among the distances L11 to L15, the distance L13 between point p3 and triangular polygon t1 is the shortest, so the target plane determination unit 213 determines the plane passing through triangular polygon t1 as the target plane g1.

[0055] The distance calculation unit 214 calculates the distance L21 between point p1 and target plane g1, and the distance L22 between point p5 and target plane g1, based on the positions of points p1 and p5 at both ends of the cutting edge calculated in step S4 and the target plane g1 determined in step S6 (step S7). In step S7, the target plane determination unit 213 calculates the distances L21 and L22 between point p1 and target plane g1 in the normal direction of target plane g1 for each of points p1 and p5.

[0056] Next, the tilt control unit 217 determines whether or not there is a tilt operation input from the operator based on the manipulated amount obtained in step S1 (step S8). For example, the tilt control unit 217 determines that there is no operation input if the absolute value of the tilt operation amount is less than a predetermined value. If there is no tilt operation (step S8: NO), the tilt control unit 217 determines whether or not at least one of the distance L21 between point p1 and target plane g1, and the distance L22 between point p5 and target plane g1, is less than the tilt control distance th (step S9).

[0057] If at least one of distances L21 and L22 is less than the tilt control distance th (step S9: YES), the tilt control unit 217 calculates the difference between distance L21 and distance L22 calculated in step S7 (step S10). Next, the tilt control unit 217 calculates the tilt control amount based on the difference (distance difference) between distance L21 and distance L22 (step S11).

[0058] Figure 8 shows an example of a tilt function illustrating the relationship between the bucket distance difference and the target value of the tilt angular velocity according to the first embodiment. The bucket distance difference shown in Figure 8 is obtained by subtracting distance L22 from distance L21 shown in Figure 7, with the counterclockwise angular velocity in Figure 7 being considered positive. In step S11, the tilt control unit 217 determines a target value for the tilt angular velocity by substituting the distance difference into a predetermined tilt function as shown in Figure 8. The tilt function is a function that determines the target value for the tilt angular velocity based on the distance difference of the buckets 155. In the tilt function, the target value for the tilt angular velocity increases monotonically with respect to the distance difference of the buckets 155. In addition, upper and lower limits for the tilt angular velocity are defined in the tilt function, and the target value for the tilt angular velocity becomes constant when the absolute value of the distance difference exceeds a predetermined value. Furthermore, a dead zone (hysteresis) is set in the tilt function, and the target value for the tilt angular velocity becomes zero when the distance difference is within the dead zone near zero. That is, when the distance difference is within the dead zone near zero, the rotation of the bucket 155 around the tilt axis X4 is stopped. Then, the tilt control unit 217 determines the tilt control amount based on the determined target value for the tilt angular velocity.

[0059] By incorporating a dead zone into the tilt function, it is possible to prevent repeated overshoot and overcorrection of the bucket 155's tilt control. This prevents rattling of the excavation surface when the tilt angle η of the bucket 155 is controlled by automatic tilt control. Furthermore, by defining the dead zone by the allowable error amount relative to the target construction surface, it is possible to prevent rattling of the excavation surface while keeping the excavation error of the target construction surface within the allowable error amount.

[0060] Furthermore, if a tilt operation is performed (step S8: YES), or if both distance L21 and distance L22 are greater than or equal to the tilt control distance th (step S9: NO), the tilt control unit 217 does not calculate the tilt control amount.

[0061] The output unit 218 then outputs control signals to each actuator based on the respective operating amounts related to the work implement 150 and the tilt control amount calculated by the tilt control unit 217 (step S12). When automatic tilt control is performed, the tilt cylinder 163 is driven according to the signals generated by the tilt control unit 217. When automatic tilt control is not performed, the tilt cylinder 163 is driven according to the signals based on the operator's operating amount.

[0062] Action / Effect As described above, the control device 190 according to the first embodiment calculates a first distance L21, which is the distance between a first bucket point p1 on the bucket 155 and the target design surface, and a second distance L22, which is the distance between a second bucket point p5 on the bucket 155 and the target design surface. The first distance L21 and the second distance L22 are then compared to calculate a tilt control amount that rotates the bucket 155 around the tilt axis X4. As a result, the control device 190 can automatically control the work machine 150 so that the bucket 155 moves along the target design surface.

[0063] In the first embodiment, the first bucket point p1 and the second bucket point p5 are the ends of the cutting edge of the bucket 155, but this is not limited to this. For example, in other embodiments, points p2 and p4 may be the first bucket point and the second bucket point, respectively. In other embodiments, the control device 190 may calculate the tilt control amount based on the tilt angle η of the bucket 155. On the other hand, by using the distance difference between the ends of the cutting edge of the bucket 155, the excavation error relative to the target construction surface can be easily managed. For example, if the control device 190 calculates the tilt control amount based on the tilt angle η of the bucket 155, the excavation error caused by the error in the tilt angle η changes depending on the length of the cutting edge of the bucket 155. In contrast, if the tilt control amount is calculated based on the distance difference between both ends of the bucket 155 and the target plane, as in the first embodiment, the excavation error does not change depending on the length of the cutting edge of the bucket 155.

[0064] Furthermore, in the first embodiment, the control device 190 stops rotation around the tilt axis X4 when the difference between the first distance L21 and the second distance L22 is within the dead zone. That is, in the first embodiment, the control device 190 stops rotation around the tilt axis X4 when the angle between the cutting edge of the bucket 155 and the target design surface is below a predetermined threshold. This prevents repeated overshoot and overcorrection of the tilt control of the bucket 155. Also, since this dead zone is defined by the allowable error amount relative to the target construction surface, it is possible to prevent rattling of the excavated surface while keeping the excavation error of the target construction surface within the allowable error amount.

[0065] Other embodiments Although one embodiment has been described in detail above with reference to the drawings, the specific configuration is not limited to that described above, and various design changes are possible. In other embodiments, the order of the above-described processes may be changed as appropriate. Also, some processes may be executed in parallel.

[0066] The control device 190 according to the above embodiment may be composed of a single computer, or the configuration of the control device 190 may be divided among multiple computers, and the multiple computers may cooperate with each other to function as a control system. In this case, some of the computers constituting the control device 190 may be mounted inside the work machine 100, while the other computers may be provided outside the work machine 100.

[0067] The control device 190 according to the above embodiment determines distances L11-L15 and distances L21 and L22 based on the criteria shown in Figure 7, but is not limited thereto. For example, in the control device 190 according to another embodiment, distances L11-L15 may be determined as distances relative to the normal direction of the triangular polygon, or as distances relative to the direction perpendicular to the cutting edge of the bucket 155. In addition, in the control device 190 according to another embodiment, distances L21 and L22 may be determined as distances relative to the vertical direction, or as distances relative to the direction perpendicular to the cutting edge of the bucket 155. Furthermore, for example, triangular polygons t1 and t2 may be selected from the intersection lines of the tilt operation plane, which passes through the cutting edge of the bucket 155 and is perpendicular to the tilt axis X4, and the target design plane.

[0068] The control device 190 according to the above embodiment calculates a tilt control amount for rotating the bucket 155 around the tilt axis X4 by comparing a first distance L21 and a second distance L22, but is not limited to this. For example, the control device 190 according to another embodiment may calculate the tilt control amount based on the other of the first distance L21 and second distance L22 when one of the first distance L21 and second distance L22 becomes less than the tilt control distance th. For example, the control device 190 may calculate the tilt control amount based on the magnitude of the second distance L22 when the first distance L21 becomes less than the tilt control distance th. Also, for example, the control device 190 may prevent rotation around the tilt axis X4 when the other distance of the first distance L21 and second distance L22 is greater than or equal to a predetermined value. In other words, the control device 190 calculates the tilt control amount based on at least the larger of the first distance L1 and second distance L2.

[0069] The control device 190 in the above-described embodiment always has automatic tilt control enabled, but is not limited to this. The operating device 172 in other embodiments may be equipped with a switch for switching automatic tilt control on or off. In this case, the control device 190 may determine whether or not to perform automatic tilt control based on the state of the switch. That is, the control device 190 performs automatic tilt control when the switch is ON, there is no tilt operation input (step S8: NO), and the distance between the cutting edge of the bucket 155 and the target plane g1 is less than the tilt control distance th (step S9). On the other hand, when the switch is OFF, the control device 190 does not perform automatic tilt control even if there is no tilt operation input and the distance between the cutting edge of the bucket 155 and the target plane g1 is less than the tilt control distance th. The switch may be provided as a function of a monitor (not shown) or placed on an operating lever, etc., as long as it can be operated by an operator. [Explanation of symbols]

[0070] 100…Working machine 110…Traveling body 130…Slewing body 131…Position and orientation detector 132…Tilt detector 150…Working machine 151…Boom 152…Arm 155…Bucket 161…Bucket body 162…Joint 163…Tilt cylinder 190…Control device 211…Detection value acquisition unit 212…Bucket position identification unit 213…Target plane determination unit 214…Distance calculation unit 215…Operation amount acquisition unit 216…Intervention control unit 217…Tilt control unit 218…Output unit

Claims

1. A work machine comprising a boom rotatable around a boom axis, an arm rotatable around an arm axis parallel to the boom axis, and a bucket rotatable around a bucket axis parallel to the arm axis and rotatable around a tilt axis perpendicular to the bucket axis, The system includes a tilt control unit that calculates a tilt control amount to rotate the bucket around the tilt axis so that the cutting edge of the bucket and the target design surface indicating the target shape of the object to be excavated become nearly parallel, and stops the rotation around the tilt axis when the angle between the cutting edge of the bucket and the target design surface is less than or equal to a predetermined threshold. The threshold is defined such that, when the angle between the cutting edge of the bucket and the target design surface is less than or equal to the threshold, the excavation error with respect to the target design surface at the widthwise end of the cutting edge of the bucket is less than or equal to the allowable error amount. Control system for industrial machinery.

2. The target design surface is composed of a plurality of polygons, The control system further includes a target plane determination unit that determines the plane passing through the polygon that is closest in the vertical direction to the bucket from among the target design planes as the target plane, The tilt control unit uses the target plane as the target design plane to calculate the tilt control amount so that the tip of the bucket and the target plane become nearly parallel, and stops the rotation around the tilt axis when the angle between the tip of the bucket and the target plane is less than or equal to the threshold. A control system for a work machine according to claim 1.

3. A control method for a work machine comprising a boom rotatable around a boom axis, an arm rotatable around an arm axis parallel to the boom axis, and a bucket rotatable around a bucket axis parallel to the arm axis and rotatable around a tilt axis perpendicular to the bucket axis, The steps include: calculating a tilt control amount to rotate the bucket around the tilt axis so that the cutting edge of the bucket and the target design surface indicating the target shape of the object to be excavated become nearly parallel; The step of stopping the rotation around the tilt axis when the angle between the cutting edge of the bucket and the target design surface is less than or equal to a predetermined threshold, Equipped with, The threshold is defined such that, when the angle between the cutting edge of the bucket and the target design surface is less than or equal to the threshold, the excavation error with respect to the target design surface at the widthwise end of the cutting edge of the bucket is less than or equal to the allowable error amount. A method for controlling industrial machinery.

4. The target design surface is composed of a plurality of polygons, The step further comprises determining the target plane as the plane passing through the polygon that is closest in the vertical direction to the bucket among the aforementioned target design planes, In the step of calculating the tilt control amount, the target plane is used as the target design plane, and the tilt control amount is calculated so that the cutting edge of the bucket and the target plane become closer to parallel. In the step of stopping the rotation around the tilt axis, the rotation around the tilt axis is stopped if the angle between the cutting edge of the bucket and the target plane is less than or equal to the threshold. A method for controlling a work machine according to claim 3.

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