EP4779087A1

EP4779087A1 - Control system for work machine, work machine, remote operation system for work machine, and control method for work machine

Info

Publication number: EP4779087A1
Application number: EP25778388.6A
Authority: EP
Inventors: Shunsuke Miyamoto
Original assignee: Komatsu Ltd
Current assignee: Komatsu Ltd
Priority date: 2024-03-27
Filing date: 2025-03-07
Publication date: 2026-07-22
Also published as: WO2025204746A1

Abstract

A control system for a work machine includes a controller. The controller determines a presence or absence of a predetermined operation in which a bucket of a work implement of the work machine repeatedly performs a tilt operation and a dump operation, and in a case where it is determined that the predetermined operation has been performed and it is determined that an operation speed of the predetermined operation exceeds a threshold value, the controller outputs a control command such that the operation speed becomes equal to or less than the threshold value.

Description

Technical Field

The present disclosure relates to a control system for a work machine, a work machine, a remote operation system for a work machine, and a control method for a work machine.

Background Art

In the technical field relating to work machines, a remote operation system for a wheel loader as disclosed in Patent Literature 1 is known. In Patent Literature 1, the wheel loader includes a camera and an antenna. An on-board controller of the wheel loader receives a remote signal from an off-board controller via the antenna. The off-board controller receives camera images from the camera, and displays the camera images on a display.

Citation List

Patent Literature

Patent Literature 1: European Patent Application Publication No. 3926107

Summary of Invention

Technical Problem

A work machine includes a work implement. In a case where the work implement is operated based on an operation signal from an operation device operated by an operator, when the operation device is operated abruptly, the work implement operates abruptly. When the work implement operates abruptly, the work machine may deteriorate prematurely.
The work machine includes a vehicle body and a work implement connected to the vehicle body. The work implement operates based on an operation signal from an operation device operated by the operator. For example, when the operation device is operated so as to abruptly interrupt a lowering operation while the work implement is performing the lowering operation, the weight balance of the work machine may be disrupted. When the weight balance of the work machine is disrupted, a load is applied to the work machine, and the work machine may deteriorate.
An object of the present disclosure is to suppress deterioration of a work machine.

Solution to Problem

According to the present disclosure, a control system for a work machine including a controller is provided. The controller determines a presence or absence of a predetermined operation in which a bucket of a work implement of the work machine repeatedly performs a tilt operation and a dump operation, and in a case where it is determined that the predetermined operation has been performed and it is determined that an operation speed of the predetermined operation exceeds a threshold value, the controller outputs a control command such that the operation speed becomes equal to or less than the threshold value.
According to the present disclosure, a control system for a work machine including a controller is provided. The controller acquires an operation signal from an operation device operated for operating a work implement of a work machine, and in a case where a sudden operation of the operation device is performed while the work implement is performing a lowering operation from a raised posture in which the work implement is raised, and a weight balance of the work machine changes, the controller outputs a control command such that a change rate of the operation signal becomes smaller.

Advantageous Effects of Invention

According to the present disclosure, deterioration of a work machine is suppressed.

Brief Description of Drawings

Fig. 1 is a diagram illustrating a remote operation system for a work machine according to a first embodiment.
Fig. 2 is a configuration diagram illustrating a work machine and an operation device according to the first embodiment.
Fig. 3 is a hardware configuration diagram illustrating an on-board controller according to the first embodiment.
Fig. 4 is a diagram for describing an operation of a work machine according to the first embodiment.
Fig. 5 is a functional block diagram illustrating a control system for a work machine according to the first embodiment.
Fig. 6 is a flowchart illustrating a control method for a work machine according to the first embodiment.
Fig. 7 is a diagram for describing a posture of a work implement according to the first embodiment.
Fig. 8 is a diagram illustrating an example of an operation signal from a bucket lever according to the first embodiment.
Fig. 9 is a diagram illustrating an example of an operation signal from a bucket lever according to the first embodiment.
Fig. 10 is a diagram for describing an operation of a work machine according to a second embodiment.
Fig. 11 is a functional block diagram illustrating a control system for a work machine according to the second embodiment.
Fig. 12 is a flowchart illustrating a control method for a work machine according to the second embodiment.
Fig. 13 is a diagram illustrating an example of a relationship between an operation signal from a boom lever and a height of a boom according to the second embodiment.
Fig. 14 is a diagram illustrating an example of a relationship between an operation signal from a boom lever and a height of a boom according to the second embodiment.

Description of Embodiments

Hereinafter, embodiments according to the present disclosure will be described with reference to the drawings, but the present disclosure is not limited to the embodiments. The components of the embodiments to be described below can be appropriately combined. In addition, some components may not be used.

[First Embodiment]

A first embodiment will be described.

Fig. 1 is a diagram illustrating a remote operation system 200 for a work machine 1 according to the embodiment. The remote operation system 200 remotely operates the work machine 1 present at a work site 201. At least a part of the remote operation system 200 is disposed in a remote operation room 202 provided outside the work machine 1. The remote operation system 200 includes an operation device 7, a display device 8, and a remote controller 9.
The operation device 7 is disposed in the remote operation room 202. The operation device 7 is operated by an operator in the remote operation room 202. The operator can operate the operation device 7 while being seated on an operator seat 10. Note that the operator may operate a portable operation device 700. The operation device 700 may be operated outside the remote operation room 202.
The display device 8 is disposed in the remote operation room 202. As the display device 8, a flat panel display such as a liquid crystal display or an organic EL display is exemplified. The display device 8 displays at least an image of the work site 201. The display device 8 may output sound of the work site 201.
The operator operates the operation device 7 while checking the image of the work site 201 displayed on the display device 8. The work machine 1 is remotely operated by the operation device 7.
The remote controller 9 is disposed in the remote operation room 202. The remote controller 9 and the work machine 1 communicate with each other via a communication system 203. As the communication system 203, the Internet, a local area network (LAN), a cellular communication network, and a satellite communication network are exemplified.

In the embodiment, the work machine 1 is a wheel loader. As illustrated in Fig. 1, the work machine 1 includes a vehicle body 2, an articulation mechanism 3, a cab 4, wheels 5, a work implement 6, and a camera 29. The work machine 1 travels over the work site 201 by the wheels 5. The work machine 1 performs work using the work implement 6 at the work site 201. Examples of work that can be performed by the work machine 1 include excavation work, loading work, transport work, and snow removal work.
The vehicle body 2 supports the work implement 6. The vehicle body 2 includes a front frame 2F and a rear frame 2R. The front frame 2F is disposed forward of the rear frame 2R. The front frame 2F and the rear frame 2R are connected by the articulation mechanism 3. The articulation mechanism 3 includes an articulation cylinder 11. The articulation cylinder 11 is a hydraulic cylinder. The articulation cylinder 11 connects the front frame 2F and the rear frame 2R. When the articulation cylinder 11 extends and contracts, the front frame 2F articulates in a left-right direction with respect to the rear frame 2R. By articulation of the front frame 2F with respect to the rear frame 2R, a traveling direction of the work machine 1 is adjusted. The cab 4 is disposed on an upper portion of the rear frame 2R.
The wheels 5 support the vehicle body 2. The wheels 5 include tires. The wheels 5 are in contact with the ground of the work site. The wheels 5 include front wheels 5F mounted on the front frame 2F and rear wheels 5R mounted on the rear frame 2R. The front wheels 5F rotate about a rotation axis CXf. The rear wheels 5R rotate about a rotation axis CXr. When the work machine 1 travels in a straight-ahead state, the rotation axis CXf of the front wheels 5F and the rotation axis CXr of the rear wheels 5R are parallel to each other. By rotation of the wheels 5, the work machine 1 travels over the ground of the work site 201.
The work implement 6 is supported by the vehicle body 2. The work implement 6 is connected to the front frame 2F. The work implement 6 includes a boom 12, a bucket 13, a bell crank 14, and a bucket link 15.
A base end portion of the boom 12 is pivotably connected to the front frame 2F. The boom 12 pivots with respect to the front frame 2F about a rotation axis AXa. A bracket 16 is fixed to an intermediate portion of the boom 12.
The bucket 13 is a work member for excavating an excavation target. The bucket 13 holds an excavated object. The bucket 13 includes a blade tip portion 13A, an opening portion 13B, and a bottom surface 13C.
A base end portion of the bucket 13 is pivotably connected to a distal end portion of the boom 12. The bucket 13 pivots with respect to the boom 12 about a rotation axis AXb. The bucket 13 is disposed forward of the front wheels 5F. A bracket 17 is fixed to a portion of the bucket 13.
An intermediate portion of the bell crank 14 is pivotably connected to the bracket 16 of the boom 12. The bell crank 14 pivots with respect to the bracket 16 of the boom 12 about a rotation axis AXc. A lower end portion of the bell crank 14 is pivotably connected to a base end portion of the bucket link 15.
A distal end portion of the bucket link 15 is pivotably connected to the bracket 17 of the bucket 13. The bucket link 15 pivots with respect to the bracket 17 of the bucket 13 about a rotation axis AXd. The bell crank 14 is connected to the bucket 13 via the bucket link 15.
The boom 12 is operated by a boom cylinder 18. The boom cylinder 18 is a hydraulic cylinder. A base end portion of the boom cylinder 18 is connected to the front frame 2F. A distal end portion of the boom cylinder 18 is connected to the boom 12. The boom 12 pivots with respect to the boom cylinder 18 about a rotation axis AXe.
The bucket 13 is operated by a bucket cylinder 19. The bucket cylinder 19 is a hydraulic cylinder. A base end portion of the bucket cylinder 19 is connected to the front frame 2F. A distal end portion of the bucket cylinder 19 is connected to an upper end portion of the bell crank 14. The bell crank 14 pivots with respect to the bucket cylinder 19 about a rotation axis AXf.
The rotation axis AXa, the rotation axis AXb, the rotation axis AXc, the rotation axis AXd, the rotation axis AXe, the rotation axis AXf, and the rotation axis CXf of the front wheels 5F are parallel to each other. When the work machine 1 travels in a straight-ahead state, the rotation axis AXa of the work implement 6 and the rotation axis CXr of the rear wheels 5R are parallel to each other.
The camera 29 images the work site 201. The camera 29 images at least the work site 201 in front of the work machine 1. The camera 29 images at least a part of the work implement 6. In the embodiment, the camera 29 is disposed in the cab 4.

Fig. 2 is a configuration diagram illustrating the work machine 1 and the operation device 7 according to the embodiment. As illustrated in Fig. 2, the work machine 1 includes an engine 20, a power take-off (PTO) 21, a power transmission device 22, a brake device 23, a steering pump 24, a steering control valve 37, the articulation cylinder 11, a work implement pump 26, a boom control valve 38, a bucket control valve 39, the boom cylinder 18, the bucket cylinder 19, a work implement posture sensor 28, a load sensor 27, the camera 29, and an on-board controller 30.
The engine 20 is a driving source of the work machine 1. The engine 20 is supported by the vehicle body 2. As the engine 20, a diesel engine is exemplified. The power take-off 21 distributes driving force of the engine 20 to the power transmission device 22, the steering pump 24, and the work implement pump 26. The power transmission device 22 transmits driving force of the engine 20 to the wheels 5. The brake device 23 reduces a traveling speed of the work machine 1.
The power transmission device 22 transmits driving force of the engine 20 to the wheels 5. The power transmission device 22 controls a speed range and a traveling direction of the work machine 1. The power transmission device 22 may be a transmission including a torque converter, or a transmission including a plurality of speed-change gears. The brake device 23 reduces a traveling speed of the work machine 1.
The steering pump 24 is a hydraulic pump operated by driving force generated by the engine 20. Hydraulic fluid discharged from the steering pump 24 is supplied to the articulation cylinder 11 via the steering control valve 37. The steering control valve 37 controls a flow rate and a direction of hydraulic fluid supplied from the steering pump 24 to the articulation cylinder 11. The articulation mechanism 3 is operated by hydraulic fluid supplied from the steering pump 24.
The work implement pump 26 is a hydraulic pump operated by driving force generated by the engine 20. Hydraulic fluid discharged from the work implement pump 26 is supplied to the boom cylinder 18 via the boom control valve 38. Hydraulic fluid discharged from the work implement pump 26 is supplied to the bucket cylinder 19 via the bucket control valve 39. The boom control valve 38 controls a flow rate and a direction of hydraulic fluid supplied from the work implement pump 26 to the boom cylinder 18. The bucket control valve 39 controls a flow rate and a direction of hydraulic fluid supplied from the work implement pump 26 to the bucket cylinder 19. The work implement 6 is operated by hydraulic fluid supplied from the work implement pump 26.
The work implement posture sensor 28 detects a posture of the work implement 6. The posture of the work implement 6 includes an angle of the work implement 6. The work implement posture sensor 28 includes a boom angle sensor 28A that detects a posture of the boom 12, and a bucket angle sensor 28B that detects a posture of the bucket 13. The posture of the boom 12 includes an angle of the boom 12. The posture of the bucket 13 includes an angle of the bucket 13.
The posture of the boom 12 includes an angle of the boom 12. The boom angle sensor 28A detects a boom angle indicating the angle of the boom 12. The boom angle refers to an angle of the boom 12 with respect to the vehicle body 2 in a local coordinate system. In the embodiment, the boom angle is an angle formed between a line connecting the rotation axis AXa and the rotation axis AXb and a line connecting the rotation axis CXf and the rotation axis CXr when the work machine 1 travels in a straight-ahead state. As the boom angle sensor 28A, an angle sensor disposed at a connection portion between the front frame 2F and the boom 12 is exemplified.
The posture of the bucket 13 includes an angle of the bucket 13. The bucket angle sensor 28B detects a bucket angle indicating the angle of the bucket 13. The bucket angle refers to an angle of the bucket 13 with respect to the boom 12 in a local coordinate system. In the embodiment, the bucket angle is an angle formed between a line connecting the rotation axis AXb and the blade tip portion 13A and a line connecting the rotation axis AXa and the rotation axis AXb. As the bucket angle sensor 28B, an angle sensor disposed at a connection portion between the boom 12 and the bell crank 14 is exemplified. In the embodiment, the bucket angle sensor 28B detects a bell crank angle indicating an angle of the bell crank 14 with respect to the boom 12 in a local coordinate system. The bell crank angle is an angle formed between a line connecting the rotation axis AXc and the rotation axis AXf and a line connecting the rotation axis AXa and the rotation axis AXb. The bucket angle and the bell crank angle correspond to each other on a one-to-one basis. The bucket angle sensor 28B detects a bell crank angle. The bucket angle is calculated based on detection data of the bell crank angle and detection data of the boom angle.
Each of the boom angle and the bucket angle is an angle in an operation plane of the work implement 6 that is orthogonal to the rotation axis AXa. Each of the lines connecting the rotation axis AXa and the rotation axis AXb, the rotation axis AXc and the rotation axis AXf, the rotation axis AXb and the blade tip portion 13A, and the rotation axis CXf and the rotation axis CXr when the work machine 1 travels in a straight-ahead state is a line in the operation plane of the work implement 6.
The load sensor 27 detects a loaded state of the work implement 6. The load sensor 27 detects whether the bucket 13 is in a loaded state in which an excavated object is held or in an unloaded state in which an excavated object is not held. In the embodiment, the load sensor 27 includes a weight sensor that detects a weight of the work implement 6. The weight of the work implement 6 differs between the loaded state in which the bucket 13 holds an excavated object and the unloaded state in which the bucket 13 does not hold an excavated object. By detecting the weight of the work implement 6, the load sensor 27 can detect whether the work implement 6 is in the loaded state or the unloaded state. As the load sensor 27, a bottom pressure sensor that detects bottom pressure of the boom cylinder 18 is exemplified.
The camera 29 images the work site 201. The camera 29 images at least a part of the work implement 6. Image data captured by the camera 29 is transmitted to the remote controller 9 via the on-board controller 30 and the communication system 203. The remote controller 9 causes the display device 8 to display the image data captured by the camera 29.
The operation device 7 is operated by an operator. By being operated by the operator, the operation device 7 generates an operation signal for operating the work machine 1. The operation signal generated by the operation device 7 is transmitted to the on-board controller 30 via the remote controller 9 and the communication system 203. Based on the operation signal transmitted from the remote controller 9, the on-board controller 30 outputs a control command for operating the work machine 1. The operation device 7 includes a traveling-system operation device 7A and a work-implement operation device 7B.
The traveling-system operation device 7A is operated by an operator to operate at least one of the engine 20, the power transmission device 22, and the brake device 23. The traveling-system operation device 7A generates an operation signal for operating at least one of the engine 20, the power transmission device 22, and the brake device 23. The traveling-system operation device 7A includes an accelerator pedal 71, a brake pedal 72, a steering wheel 73, and a forward/reverse switching lever 74. The accelerator pedal 71 is operated to increase a traveling speed of the work machine 1. The brake pedal 72 is operated to decrease the traveling speed of the work machine 1 or to stop traveling of the work machine 1. The steering wheel 73 is operated to change a traveling direction of the work machine 1. The forward/reverse switching lever 74 is operated to switch between forward travel and reverse travel of the work machine 1.
The work-implement operation device 7B is operated by an operator to operate the work implement 6. The work-implement operation device 7B generates an operation signal for operating the work implement 6. The work-implement operation device 7B includes a boom lever 75 and a bucket lever 76. The boom lever 75 is operated to operate the boom 12. The bucket lever 76 is operated to operate the bucket 13. Each of the boom lever 75 and the bucket lever 76 is operated to a neutral position, a first operation position on one side with respect to the neutral position, and a second operation position rearward of the neutral position.
When the boom lever 75 is operated, a spool of the boom control valve 38 moves. When the boom lever 75 is placed at the neutral position of the boom lever 75, the spool of the boom control valve 38 is placed at a neutral position at which hydraulic fluid is not allowed to flow. When the boom lever 75 is operated to one side with respect to the neutral position of the boom lever 75, a spool of the boom control valve 38 is placed at a bottom position at which hydraulic fluid discharged from the work implement pump 26 is supplied to a bottom chamber of the boom cylinder 18. When the spool of the boom control valve 38 is placed at the bottom position, the boom cylinder 18 extends. When the boom lever 75 is operated to the other side with respect to the neutral position of the boom lever 75, the spool of the boom control valve 38 is placed at a rod position at which hydraulic fluid discharged from the work implement pump 26 is supplied to a rod chamber of the boom cylinder 18. When the spool of the boom control valve 38 is placed at the rod position, the boom cylinder 18 contracts. When the boom lever 75 is operated from the neutral position of the boom lever 75 to one side and the spool of the boom control valve 38 is placed at the bottom position, the boom cylinder 18 extends. When the boom lever 75 is operated from the neutral position of the boom lever 75 to the other side and the spool of the boom control valve 38 is placed at the rod position, the boom cylinder 18 contracts. When the spool of the boom control valve 38 is placed at the neutral position, extension and contraction of the boom cylinder 18 are stopped.
When the bucket lever 76 is operated, a spool of the bucket control valve 39 moves. When the bucket lever 76 is placed at the neutral position of the bucket lever 76, the spool of the bucket control valve 39 is placed at a neutral position at which hydraulic fluid is not allowed to flow. When the bucket lever 76 is operated to one side with respect to the neutral position of the bucket lever 76, the spool of the bucket control valve 39 is placed at a bottom position at which hydraulic fluid discharged from the work implement pump 26 is supplied to a bottom chamber of the bucket cylinder 19. When the spool of the bucket control valve 39 is placed at the bottom position, the bucket cylinder 19 extends. When the bucket lever 76 is operated to the other side with respect to the neutral position of the bucket lever 76, the spool of the bucket control valve 39 is placed at a rod position at which hydraulic fluid discharged from the work implement pump 26 is supplied to a rod chamber of the bucket cylinder 19. When the spool of the bucket control valve 39 is placed at the rod position, the bucket cylinder 19 contracts. When the spool of the bucket control valve 39 is placed at the bottom position, the bucket cylinder 19 extends. When the spool of the bucket control valve 39 is placed at the rod position, the bucket cylinder 19 contracts. When the spool of the bucket control valve 39 is placed at the neutral position, extension and contraction of the bucket cylinder 19 are stopped.

<On-Board Controller>

Fig. 3 is a hardware configuration diagram illustrating the on-board controller 30 according to the embodiment. The on-board controller 30 includes a computer system. The on-board controller 30 includes a processor 31 such as a Central Processing Unit (CPU), a main memory 32 including a non-volatile memory such as a Read Only Memory (ROM) and a volatile memory such as a Random Access Memory (RAM), a storage 33, an input/output interface 34 including input/output circuits, and a communication interface 35 including communication circuits. Functions of the on-board controller 30 are stored in the storage 33 as computer programs. The processor 31 reads a computer program from the storage 33, deploys the computer program into the main memory 32, and executes processing in accordance with the computer program. The computer program may be distributed to the on-board controller 30 via a network.
The remote controller 9 also includes a computer system. Similarly to the on-board controller 30, the remote controller 9 includes a processor, a main memory, a storage, an input/output interface, and a communication interface.

Fig. 4 is a diagram for describing an operation of the work machine 1 according to the embodiment. In the embodiment, the work implement 6 is a front-loading type work implement in which the opening portion 13B of the bucket 13 faces forward during excavation work. By extension and contraction of the boom cylinder 18, the boom 12 performs a raising operation or a lowering operation. By extension and contraction of the bucket cylinder 19, the bucket 13 performs a tilt operation or a dump operation.
The raising operation of the boom 12 refers to an operation in which the boom 12 pivots about the rotation axis AXa such that the distal end portion of the boom 12 moves away from the ground. The lowering operation of the boom 12 refers to an operation in which the boom 12 pivots about the rotation axis AXa such that the distal end portion of the boom 12 approaches the ground.
When the boom lever 75 is operated to one side with respect to the neutral position of the boom lever 75 and the boom cylinder 18 extends, the boom 12 performs the raising operation. When the boom lever 75 is operated to the other side with respect to the neutral position of the boom lever 75 and the boom cylinder 18 contracts, the boom 12 performs the lowering operation.
The tilt operation of the bucket 13 refers to an operation in which the bucket 13 pivots about the rotation axis AXb such that the opening portion 13B of the bucket 13 faces upward and the blade tip portion 13A moves away from the ground. The dump operation of the bucket 13 refers to an operation in which the bucket 13 pivots about the rotation axis AXb such that the opening portion 13B of the bucket 13 faces downward and the blade tip portion 13A approaches the ground.
When the bucket lever 76 is operated to one side with respect to the neutral position of the bucket lever 76 and the bucket cylinder 19 extends, the bell crank 14 pivots such that the upper end portion of the bell crank 14 moves forward and the lower end portion of the bell crank 14 moves rearward. As the lower end portion of the bell crank 14 moves rearward, the bucket 13 is pulled rearward by the bucket link 15 and performs the tilt operation. When the bucket lever 76 is operated to the other side with respect to the neutral position of the bucket lever 76 and the bucket cylinder 19 contracts, the bell crank 14 pivots such that the upper end portion of the bell crank 14 moves rearward and the lower end portion of the bell crank 14 moves forward. As the lower end portion of the bell crank 14 moves forward, the bucket 13 is pushed forward by the bucket link 15 and performs the dump operation.
When the bucket 13 performs the tilt operation, an excavated object is scooped by the bucket 13 and held in the bucket 13. When the bucket 13 performs the dump operation, the excavated object held in the bucket 13 is discharged from the bucket 13.
As illustrated in Fig. 4, the work machine 1 can perform loading work of loading the excavated object into a dump body of a dump truck 300. The operator operates the work-implement operation device 7B to control a posture of the work implement 6 such that the excavated object held in the bucket 13 is loaded into the dump body of the dump truck 300. The operator controls the posture of the work implement 6 such that the excavated object does not spill from the bucket 13 and such that the bucket 13 is positioned above an upper end portion of the dump body.
In order to load an excavated object into the dump body of the dump truck 300, the operator may, after performing a dump operation of the bucket 13 with a front end portion of the boom 12 raised, operate the bucket 13 such that the excavated object adhering to the bucket 13 is shaken off from the bucket 13. In a case where the excavated object adhering to the bucket 13 is shaken off from the bucket 13, the operator performs a reciprocating operation of the bucket lever 76 between one side and the other side with respect to the neutral position. By the reciprocating operation of the bucket lever 76, the bucket 13 repeatedly performs the tilt operation and the dump operation. By repeatedly performing the tilt operation and the dump operation of the bucket 13, the excavated object adhering to the bucket 13 is shaken off from the bucket 13. In the following description, an operation in which the bucket 13 repeatedly performs the excavation operation and the dump operation will be referred to, as appropriate, as a predetermined operation.

Fig. 5 is a functional block diagram illustrating a control system 100 of the work machine 1 according to the embodiment. The control system 100 includes the operation device 7, the remote controller 9, the on-board controller 30, the work implement posture sensor 28, and the camera 29.
The on-board controller 30 includes a sensor data acquisition unit 101, an operation signal acquisition unit 102, a posture determination unit 103, an operation determination unit 104, a traveling control unit 106, a work implement control unit 107, and a transmission unit 108.
The sensor data acquisition unit 101 acquires detection data of the work implement posture sensor 28. The detection data of the work implement posture sensor 28 includes detection data of the boom angle sensor 28A indicating a boom angle and detection data of the bucket angle sensor 28B indicating a bucket angle.
The operation signal acquisition unit 102 acquires an operation signal from the operation device 7. The operation signal from the operation device 7 includes an operation signal from the boom lever 75 that is operated to operate the boom 12 and an operation signal from the bucket lever 76 that is operated to operate the bucket 13.
The posture determination unit 103 determines, based on detection data of the work implement posture sensor 28, whether a posture of the work implement 6 satisfies a predetermined posture condition. Satisfying the posture condition includes a predetermined posture in which a height of the work implement 6 is equal to or greater than a predetermined height. The posture determination unit 103 determines whether a height of the work implement 6 is equal to or greater than a predetermined height. The posture determination unit 103 determines whether the height of the work implement 6 is equal to or greater than the predetermined height based on detection data of the work implement posture sensor 28 that detects the posture of the work implement 6.
In the embodiment, the work implement 6 being in the predetermined posture includes a state in which the bottom surface 13C of the bucket 13 is inclined downward toward the front. The posture determination unit 103 determines whether the predetermined posture in which the bottom surface 13C of the bucket 13 is inclined downward toward the front is obtained.
The operation determination unit 104 determines, based on an operation signal from the bucket lever 76, whether an operation of the bucket 13 satisfies a predetermined operation condition. Satisfying the operation condition includes performing a predetermined operation in which the bucket 13 repeatedly performs the tilt operation and the dump operation. The operation determination unit 104 determines the presence or absence of the predetermined operation in which the bucket 13 repeatedly performs the tilt operation and the dump operation.
The traveling control unit 106 controls traveling of the work machine 1 based on an operation signal from the traveling-system operation device 7A. The traveling control unit 106 adjusts a traveling speed of the work machine 1, adjusts a traveling direction of the work machine 1, and switches between forward travel and reverse travel of the work machine 1 based on the operation signal from the traveling-system operation device 7A.
The work implement control unit 107 controls the work implement 6 based on an operation signal from the work-implement operation device 7B. The work implement control unit 107 controls the boom control valve 38 based on an operation signal from the boom lever 75. By controlling the boom control valve 38, the boom cylinder 18 extends and contracts, and the boom 12 performs the raising operation and the lowering operation. The work implement control unit 107 controls the bucket control valve 39 based on an operation signal from the bucket lever 76. By controlling the bucket control valve 39, the bucket cylinder 19 extends and contracts, and the bucket 13 performs the tilt operation and the dump operation.
The work implement control unit 107 performs intervention control of the bucket 13. The intervention control of the bucket 13 refers to controlling the bucket control valve 39 such that the bucket control valve 39 is driven under a predetermined condition while the bucket lever 76 is being operated. That is, the intervention control of the bucket 13 refers to outputting a control command from the work implement control unit 107 such that the bucket 13 operates under a predetermined condition while an operation signal from the bucket lever 76 is being acquired by the operation signal acquisition unit 102.
The transmission unit 108 transmits image data captured by the camera 29 to the remote controller 9. The transmission unit 108 may transmit detection data of the work implement posture sensor 28 to the remote controller 9.

Fig. 6 is a flowchart illustrating a control method for the work machine 1 according to the embodiment. The operation signal acquisition unit 102 acquires an operation signal from the operation device 7. The traveling control unit 106 controls traveling of the work machine 1 based on an operation signal from the traveling-system operation device 7A. The work implement control unit 107 controls the work implement 6 based on an operation signal from the work-implement operation device 7B. The sensor data acquisition unit 101 acquires detection data of the work implement posture sensor 28 (step S1).
The posture determination unit 103 determines whether the work implement 6 is in the predetermined posture based on detection data of the work implement posture sensor 28 that detects the posture of the work implement 6 (step S2).
Fig. 7 is a diagram for describing the posture of the work implement 6 according to the embodiment. The bucket 13 includes a blade tip portion 13A, the opening portion 13B, and the bottom surface 13C. The opening portion 13B is provided at a front portion of the bucket 13. The blade tip portion 13A is provided at a lower end portion of the opening portion 13B. The bottom surface 13C is provided to extend rearward from the blade tip portion 13A. The bottom surface 13C is a substantially flat surface.
The work implement 6 being in the predetermined posture includes a state in which the height of the work implement 6 is equal to or greater than the predetermined height. In a case where the boom 12 and the bucket 13 are connected via the rotation axis AXb, the height of the work implement 6 includes a height of the rotation axis AXb from the ground. In a case where a line connecting the rotation axis CXf of the front wheels 5F and the rotation axis CXr of the rear wheels 5R is defined as a reference line RL, the predetermined height includes a height of the reference line RL from the ground. That is, in the embodiment, the height of the work implement 6 being equal to or greater than the predetermined height includes a state in which the rotation axis AXb is disposed above the reference line RL. Note that the height of the work implement 6 being equal to or greater than the predetermined height may include a state in which the rotation axis AXb is disposed above a bottom surface of the vehicle body 2. The height of the work implement 6 may be a height of the bottom surface 13C of the bucket 13 from the ground. The height of the bottom surface 13C of the bucket 13 may change due to the tilt operation or the dump operation of the bucket 13.
In addition, the work implement 6 being in the predetermined posture includes a state in which the bottom surface 13C of the bucket 13 is inclined downward toward the front. In the embodiment, in a case where a line connecting the rotation axis CXf of the front wheels 5F and the rotation axis CXr of the rear wheels 5R is defined as a reference line RL, the work implement 6 being in the predetermined posture includes a state in which the bottom surface 13C of the bucket 13 is inclined downward toward the front with respect to the reference line RL. The posture determination unit 103 determines whether the bottom surface 13C of the bucket 13 is inclined downward toward the front with respect to the reference line RL. In a case where the reference line RL is parallel to the horizontal plane, the work implement 6 being in the predetermined posture includes a state in which the blade tip portion 13A is disposed lower than a rear portion of the bottom surface 13C. The work implement 6 being in the predetermined posture includes a state in which, in the vertical direction, a distance between the blade tip portion 13A and the ground is shorter than a distance between the rear portion of the bottom surface 13C and the ground.
Note that the work implement 6 being in the predetermined posture may include a state in which the rotation axis AXb between the boom 12 and the bucket 13 is disposed above the rotation axis AXa between the front frame 2F and the boom 12. That is, the work implement 6 being in the predetermined posture may include a state in which, in the vertical direction, a distance between the rotation axis AXb and the ground is longer than a distance between the rotation axis AXa and the ground. The posture determination unit 103 may determine whether the rotation axis AXb is disposed above the rotation axis AXa.
As illustrated in Fig. 4, when an excavated object is loaded into the dump body of the dump truck 300, the bucket 13 performs the dump operation while the front end portion of the boom 12 is raised. The predetermined posture of the work implement 6 may be regarded as a posture immediately after the work implement 6 has loaded an excavated object into the dump body of the dump truck 300.
In a case where it is determined in step S2 that the work implement 6 is in the predetermined posture (step S2: Yes), the operation determination unit 104 determines the presence or absence of the predetermined operation in which the bucket 13 repeatedly performs the tilt operation and the dump operation, based on an operation signal from the bucket lever 76 (step S3).
Each of Figs. 8 and 9 is a diagram illustrating an example of an operation signal from the bucket lever 76 according to the embodiment. In the following description, an operation signal from the bucket lever 76 will be referred to, as appropriate, as a bucket lever signal. In Figs. 8 and 9, a horizontal axis represents an elapsed time from a time point at which the work implement 6 is determined to be in the predetermined posture, and a vertical axis represents the bucket lever signal. A positive value of the bucket lever signal means that the bucket lever 76 is operated to one side from the neutral position of the bucket lever 76, and a negative value of the bucket lever signal means that the bucket lever 76 is operated to the other side from the neutral position of the bucket lever 76. That is, a positive value of the bucket lever signal means that the bucket 13 has performed the tilt operation, and a negative value of the bucket lever signal means that the bucket 13 has performed the dump operation.
The bucket lever signal includes an operation amount of the bucket lever 76. The larger the absolute value of the bucket lever signal, the larger the operation amount of the bucket lever 76 that is subjected to the reciprocating operation. The larger the absolute value of the bucket lever signal, the higher the operation speed of the bucket 13 that repeatedly performs the tilt operation and the dump operation.
As described above, after an excavated object is loaded into the dump body of the dump truck 300, the operator may cause the bucket 13 to perform the predetermined operation such that the excavated object adhering to the bucket 13 is shaken off from the bucket 13. In a case of causing the bucket 13 to perform the predetermined operation, the operator performs a reciprocating operation of the bucket lever 76 between one side and the other side with respect to the neutral position of the bucket lever 76. As illustrated in Fig. 8, when the bucket lever 76 is subjected to a reciprocating operation, the bucket lever signal repeatedly alternates between a positive-value state and a negative-value state.
In a case where it is determined that the number of times the bucket lever 76 has been subjected to a reciprocating operation between one side and the other side with respect to the neutral position is equal to or greater than a predetermined number of times within a predetermined time Tm, the operation determination unit 104 determines that the bucket 13 has performed the predetermined operation. The number of times the bucket lever 76 has been subjected to a reciprocating operation is the number of times the bucket lever signal changes from one of the positive-value state and the negative-value state to the other. For example, in a case where the bucket lever signal changes from the positive-value state to the negative-value state and then changes to the positive-value state, the operation determination unit 104 determines that the number of times the bucket lever 76 has been subjected to a reciprocating operation is one.
The predetermined time Tm is a time from a time point when the work implement 6 is determined to be in the predetermined posture, and is a predetermined time. The predetermined number of times is a number determined in advance. As an example, the predetermined time Tm is one second, and the predetermined number of times is two.
In a case where it is determined in step S3 that the bucket 13 has performed the predetermined operation (step S3: Yes), the work implement control unit 107 determines, based on an operation speed of the predetermined operation, whether to start intervention control of the bucket 13 (step S4).
An amplitude of the bucket lever signal when the bucket lever 76 is subjected to a reciprocating operation and an operation speed of the bucket 13 that repeatedly performs the tilt operation and the dump operation correspond to each other on a one-to-one basis. The larger the amplitude of the bucket lever signal, the higher, the operation speed of the bucket 13 that performs the predetermined operation. The bucket lever signal includes an operation amount of the bucket lever 76. A large amplitude of the bucket lever signal means that an absolute value of an operation amount of the bucket lever 76 that is subjected to a reciprocating operation is large. A large amplitude of the bucket lever signal means that an operation speed of the bucket 13 that performs the predetermined operation is high. The operation determination unit 104 determines, based on the amplitude of the bucket lever signal, whether the operation speed of the predetermined operation of the bucket 13 exceeds a threshold value. The threshold value is a value determined in advance.
The work implement control unit 107 compares an amplitude of the bucket lever signal at a time point when the predetermined time Tm has elapsed from a time point at which the work implement 6 is determined to be in the predetermined posture, with a threshold value Sh associated with the bucket lever signal. That is, the work implement control unit 107 compares an absolute value of an operation amount of the bucket lever 76 at a time point when the predetermined time Tm has elapsed, with the threshold value Sh. The threshold value Sh is a value determined in advance. In a case where it is determined that the amplitude (the absolute value of the operation amount) of the bucket lever signal at the time point when the predetermined time Tm has elapsed is equal to or less than the threshold value Sh, the work implement control unit 107 determines that the operation speed of the predetermined operation of the bucket 13 does not exceed the threshold value. In a case where it is determined that the amplitude (the absolute value of the operation amount) of the bucket lever signal at the time point when the predetermined time Tm has elapsed exceeds the threshold value Sh, the work implement control unit 107 determines that the operation speed of the predetermined operation of the bucket 13 exceeds the threshold value.
In the example illustrated in Fig. 8, as indicated by reference sign PK, the amplitude of the bucket lever signal at the time point when the predetermined time Tm has elapsed does not exceed the threshold value Sh. In the example illustrated in Fig. 9, as indicated by reference sign PK, the amplitude of the bucket lever signal at the time point when the predetermined time Tm has elapsed exceeds the threshold value Sh. In the case of the amplitude of the bucket lever signal illustrated in Fig. 8, the work implement control unit 107 determines that the operation speed of the predetermined operation of the bucket 13 does not exceed the threshold value. In the case of the amplitude of the bucket lever signal illustrated in Fig. 9, the work implement control unit 107 determines that the operation speed of the predetermined operation of the bucket 13 exceeds the threshold value.
In a case where it is determined that the operation speed of the predetermined operation of the bucket 13 does not exceed the threshold value, the work implement control unit 107 determines not to start the intervention control of the bucket 13. In a case where it is determined that the operation speed of the predetermined operation of the bucket 13 exceeds the threshold value, the work implement control unit 107 determines to start the intervention control of the bucket 13.
In a case where it is determined in step S4 that the intervention control of the bucket 13 is to be started (step S4: Yes), the work implement control unit 107 outputs a control command such that the operation speed of the predetermined operation of the bucket 13 becomes equal to or less than the threshold value. In the embodiment, the intervention control of the bucket 13 includes performing limiting processing to reduce the amplitude of the bucket lever signal while the bucket lever signal is being acquired by the operation signal acquisition unit 102. The work implement control unit 107 performs the limiting processing such that the amplitude of the bucket lever signal is reduced while the bucket lever signal is being acquired by the operation signal acquisition unit 102 (step S5).
As illustrated in Fig. 9, the work implement control unit 107 performs the limiting processing on the bucket lever signal acquired by the operation signal acquisition unit 102 to generate a bucket lever signal having a small amplitude. By the limiting processing, after the predetermined time Tm has elapsed, the amplitude of the bucket lever signal becomes smaller. By the limiting processing, the amplitude of the bucket lever signal is suppressed to a value equal to the threshold value Sh or a value less than the threshold value Sh. The work implement control unit 107 outputs a control command for controlling the bucket control valve 39 based on the bucket lever signal subjected to the limiting processing. The bucket control valve 39 is driven based on the bucket lever signal subjected to the limiting processing (step S6).
In the embodiment, the work implement control unit 107 changes the amplitude of the bucket lever signal acquired by the operation signal acquisition unit 102 such that the amplitude (the absolute value of the operation amount) becomes smaller. The work implement control unit 107 does not change a timing at which the bucket lever signal acquired by the operation signal acquisition unit 102 is switched from one of the positive-value state and the negative-value state to the other. That is, in a case where the bucket lever 76 is operated to one side and the other side with respect to the neutral position at a constant time interval, the work implement control unit 107 does not change a period of the bucket lever signal acquired by the operation signal acquisition unit 102.
As the amplitude of the bucket lever signal becomes smaller, the operation speed of the predetermined operation of the bucket 13 becomes lower.
The work implement control unit 107 determines, based on the bucket lever signal acquired by the operation signal acquisition unit 102, whether to terminate the intervention control (step S7).
In a case where it is determined that the amplitude of the bucket lever signal acquired by the operation signal acquisition unit 102 is equal to or less than the threshold value Sh, the work implement control unit 107 determines to terminate the intervention control. For example, in a case where the operator reduces the operation amount of the bucket lever 76 or stops operating the bucket lever 76, it is determined to terminate the intervention control.
In a case where it is determined in step S7 that the intervention control is not to be terminated (step S7: No), the work implement control unit 107 returns to the processing of step S5. In a case where it is determined in step S7 that the intervention control is to be terminated (step S7: Yes), the processing returns to step S1.
In a case where it is determined in step S2 that the work implement 6 is not in the predetermined posture (step S2: No), in a case where it is determined in step S3 in step S3 that the bucket 13 has performed the predetermined operation (step S3: No), and in a case where it is determined in step S4 that the intervention control of the bucket 13 is not to be started (step S4: No), the work implement control unit 107 does not perform the limiting processing on the bucket lever signal, and outputs a control command for controlling the bucket control valve 39 based on the operation signal acquired by the operation signal acquisition unit 102. The bucket control valve 39 is driven based on the bucket lever signal that has not been subjected to the limiting processing (step S8).

As described above, according to the embodiment, the on-board controller 30 includes the posture determination unit 103 that determines whether the height of the work implement 6 of the work machine 1 is equal to or greater than a predetermined height, the operation determination unit 104 that determines, when it is determined that the height of the work implement 6 is equal to or greater than the predetermined height, the presence or absence of the predetermined operation in which the bucket 13 repeatedly performs the tilt operation and the dump operation, and the work implement control unit 107 that outputs a control command such that the operation speed becomes equal to or less than the threshold value when it is determined that the bucket 13 has performed the predetermined operation and that the operation speed of the predetermined operation exceeds the threshold value.
According to the embodiment, for example, in a case where the bucket lever 76 is abruptly operated by the operator such that the excavated object adhering to the bucket 13 is shaken off from the bucket 13, intervention control is performed such that the tilt operation and the dump operation of the bucket 13 do not accelerate deterioration of the work implement 6. Therefore, deterioration of the work machine 1 is suppressed.
In a case where the work machine 1 is remotely operated, the operator in the remote operation room 202 has difficulty perceiving that the bucket 13 is operating abruptly even when the bucket lever 76 is abruptly operated. Therefore, the operator in the remote operation room 202 may unconsciously operate the bucket lever 76 abruptly. According to the embodiment, in a case where the bucket lever 76 is abruptly operated, intervention control is performed such that the tilt operation and the dump operation of the bucket 13 do not become abrupt. Therefore, deterioration of the work implement 6 is suppressed.

In the above-described embodiment, the operation determination unit 104 determines the presence or absence of the predetermined operation of the bucket 13 based on the bucket lever signal. In addition, the work implement control unit 107 determines whether the operation speed of the bucket 13 performing the predetermined operation exceeds the threshold value based on the amplitude of the bucket lever signal. The operation determination unit 104 may determine the presence or absence of the predetermined operation of the bucket 13 based on the detection data of the work implement posture sensor 28 (bucket angle sensor 28B). The work implement control unit 107 may determine whether the operation speed of the bucket 13 performing the predetermined operation exceeds the threshold value based on the detection data of the work implement posture sensor 28 (bucket angle sensor 28B). In a case where a pressure sensor for detecting a pressure of hydraulic fluid of the bucket cylinder 19 (bottom pressure of the bucket cylinder 19) is provided, the operation determination unit 104 may determine the presence or absence of the predetermined operation of the bucket 13 based on detection data of the pressure sensor. The work implement control unit 107 may determine whether the operation speed of the bucket 13 performing the predetermined operation exceeds the threshold value based on the detection data of the pressure sensor.
In addition, in a case where the camera 29 images the work implement 6, the operation determination unit 104 may determine whether the bucket 13 has performed the predetermined operation based on the image data of the work implement 6 captured by the camera 29. The work implement control unit 107 may determine, based on the image data of the work implement 6 captured by the camera 29, whether the amplitude of the bucket 13 performing the predetermined operation exceeds the threshold value.
In the above-described embodiment, in a case where the intervention control is started, notification data indicating that the intervention control has been started may be output from the display device 8.
In the above-described embodiment, some or all of the functions of the on-board controller 30 may be provided in the remote controller 9. For example, the posture determination unit 103 and the operation determination unit 104 may be provided in the remote controller 9.
In the above-described embodiment, the work machine 1 does not have to be remotely operated. The operator may board the cab 4 of the work machine 1 and operate the work machine 1.
In the above-described embodiment, the work machine 1 is a wheel loader. The work machine 1 may instead be a hydraulic excavator having a work implement.

[Second Embodiment]

A second embodiment will be described. In the following description, the same or equivalent components as those of the above-described embodiment are denoted by the same reference numerals, and the description of the components is simplified or omitted.

Fig. 10 is a diagram for describing an operation of the work machine 1 according to the embodiment. In the embodiment, the work implement 6 is a front-loading type work implement in which the opening portion 13B of the bucket 13 faces forward during excavation work. By extension and contraction of the boom cylinder 18, the boom 12 performs a raising operation or a lowering operation. By extension and contraction of the bucket cylinder 19, the bucket 13 performs a tilt operation or a dump operation.
The raising operation of the boom 12 refers to an operation in which the boom 12 pivots about the rotation axis AXa such that the distal end portion of the boom 12 moves away from the ground. The lowering operation of the boom 12 refers to an operation in which the boom 12 pivots about the rotation axis AXa such that the distal end portion of the boom 12 approaches the ground. When the boom cylinder 18 extends, the boom 12 performs the raising operation. When the boom cylinder 18 contracts, the boom 12 performs the lowering operation.
The tilt operation of the bucket 13 refers to an operation in which the bucket 13 pivots about the rotation axis AXb such that the opening portion 13B of the bucket 13 faces upward and the blade tip portion 13A moves away from the ground. The dump operation of the bucket 13 refers to an operation in which the bucket 13 pivots about the rotation axis AXb such that the opening portion 13B of the bucket 13 faces downward and the blade tip portion 13A approaches the ground. When the bucket cylinder 19 extends, the bucket 13 performs the tilt operation. When the bucket cylinder 19 contracts, the bucket 13 performs the dump operation.
When the bucket 13 performs the tilt operation, an excavated object is scooped by the bucket 13 and held in the bucket 13. When the bucket 13 performs the dump operation, the excavated object held in the bucket 13 is discharged from the bucket 13.
As illustrated in Fig. 10, the work machine 1 can perform loading work of loading the excavated object into the dump body of the dump truck 300. The operator operates the work-implement operation device 7B to control a posture of the work implement 6 such that the excavated object held in the bucket 13 is loaded into the dump body of the dump truck 300. The operator controls the posture of the work implement 6 such that the excavated object does not spill from the bucket 13 and such that the bucket 13 is positioned above an upper end portion of the dump body.
When the loading work is performed, the operator operates the work implement operation device 7B such that the work implement 6 assumes a raised posture. The raised posture of the work implement 6 refers to a posture in which the work implement 6 has been raised to a predetermined height Hp or higher. In the embodiment, the raised posture refers to a posture in which the rotation axis AXb at the distal end portion of the boom 12 has been raised to the predetermined height Hp or higher.
In order to load an excavated object into the dump body of the dump truck 300, the operator performs the dump operation of the bucket 13 while the distal end portion of the boom 12 is in a raised state, and thereafter causes the work machine 1 to move rearward so as to be separated from the dump truck 300. In addition, the operator operates the work implement operation device 7B to cause the work implement 6 to perform the lowering operation.

Fig. 11 is a functional block diagram illustrating the control system 100 of the work machine 1 according to the embodiment. The control system 100 includes the operation device 7, the remote controller 9, the on-board controller 30, the work implement posture sensor 28, the load sensor 27, and the camera 29.
The on-board controller 30 includes the sensor data acquisition unit 101, the operation signal acquisition unit 102, the posture determination unit 103, the operation determination unit 104, a threshold value setting unit 105, the traveling control unit 106, the work implement control unit 107, and the transmission unit 108.
The sensor data acquisition unit 101 acquires detection data of the work implement posture sensor 28 and detection data of the load sensor 27. The detection data of the work implement posture sensor 28 includes detection data of the boom angle sensor 28A indicating a boom angle and detection data of the bucket angle sensor 28B indicating a bucket angle.
The operation signal acquisition unit 102 acquires an operation signal from the operation device 7. The operation signal from the operation device 7 includes an operation signal from the boom lever 75 that is operated to operate the boom 12 and an operation signal from the bucket lever 76 that is operated to operate the bucket 13.
The posture determination unit 103 determines, based on detection data of the work implement posture sensor 28, whether a posture of the work implement 6 satisfies a predetermined posture condition. Satisfying the posture condition includes that the work implement 6 is in the raised posture. The posture determination unit 103 determines whether the work implement 6 is in the raised posture. The posture determination unit 103 determines whether the boom 12 is in the raised posture based on detection data of the boom angle sensor 28A.
The operation determination unit 104 determines whether an operation of the work implement 6 satisfies a predetermined operation condition based on the operation signal from the work implement operation device 7B. Satisfying the operation condition includes that the work implement 6 is performing a lowering operation. The operation determination unit 104 determines whether the boom 12 is performing the lowering operation based on the operation signal from the boom lever 75. Note that the operation determination unit 104 may determine whether the boom 12 is performing the lowering operation based on detection data of the boom angle sensor 28A.
The threshold value setting unit 105 sets the threshold value Sh related to the operation signal from the boom lever 75. The threshold value setting unit 105 changes the threshold value Sh based on the detection data of the load sensor 27. The threshold value Sh includes a threshold value Shc when the work implement 6 is in a loaded state and a threshold value She when the work implement 6 is in an unloaded state. The threshold value setting unit 105 determines, based on the detection data of the load sensor 27, whether the work implement 6 is in a loaded state or an unloaded state. The threshold value setting unit 105 sets the threshold value Sh to the threshold value Shc when the work implement 6 is in the loaded state, and sets the threshold value Sh to the threshold value She when the work implement 6 is in the unloaded state. The threshold value Shc when the work implement 6 is in the loaded state is smaller than the threshold value She when the work implement 6 is in the unloaded state.
The traveling control unit 106 controls traveling of the work machine 1 based on an operation signal from the traveling-system operation device 7A. The traveling control unit 106 adjusts a traveling speed of the work machine 1, adjusts a traveling direction of the work machine 1, and switches between forward travel and reverse travel of the work machine 1 based on the operation signal from the traveling-system operation device 7A.
The work implement control unit 107 controls the work implement 6 based on an operation signal from the work-implement operation device 7B. The work implement control unit 107 controls the boom control valve 38 based on an operation signal from the boom lever 75. By controlling the boom control valve 38, the boom cylinder 18 extends and contracts, and the boom 12 performs the raising operation and the lowering operation. The work implement control unit 107 controls the bucket control valve 39 based on an operation signal from the bucket lever 76. By controlling the bucket control valve 39, the bucket cylinder 19 extends and contracts, and the bucket 13 performs the tilt operation and the dump operation.
The work implement control unit 107 performs intervention control of the boom 12. The intervention control of the boom 12 refers to controlling the boom control valve 38 such that the boom control valve 38 is driven under a predetermined condition while the boom lever 75 is being operated. That is, the intervention control of the boom 12 refers to outputting a control command from the work implement control unit 107 such that the boom 12 operates under a predetermined condition while an operation signal from the boom lever 75 is being acquired by the operation signal acquisition unit 102.
The transmission unit 108 transmits image data captured by the camera 29 to the remote controller 9. The transmission unit 108 may transmit detection data of the work implement posture sensor 28 to the remote controller 9.

Fig. 12 is a flowchart illustrating a control method for the work machine 1 according to the embodiment. The operation signal acquisition unit 102 acquires an operation signal from the operation device 7. The traveling control unit 106 controls traveling of the work machine 1 based on an operation signal from the traveling-system operation device 7A. The work implement control unit 107 controls the work implement 6 based on an operation signal from the work-implement operation device 7B. The sensor data acquisition unit 101 acquires detection data of the work implement posture sensor 28 and detection data of the load sensor 27 (step S1).
The posture determination unit 103 determines whether the work implement 6 is in the raised posture based on detection data of the work implement posture sensor 28 that detects the posture of the work implement 6 (step S2).
The work implement 6 being in the raised posture includes a state in which the boom 12 is in the raised posture. The boom 12 being in the raised posture includes a state in which the rotation axis AXb between the boom 12 and the bucket 13 is disposed above the rotation axis AXa between the front frame 2F and the boom 12. That is, the work implement 6 being in the raised posture includes a state in which, in the vertical direction, a distance between the rotation axis AXb and the ground is longer than a distance between the rotation axis AXa and the ground. In addition, the boom 12 being in the raised posture includes a state in which, in a local coordinate system of the work machine 1, the rotation axis AXb at the distal end portion of the boom 12 has been raised to the predetermined height Hp or higher.
Note that, in a case where a line parallel to the line connecting the rotation axis CXf of the front wheels 5F and the rotation axis CXr of the rear wheels 5R is defined as a reference line, the work implement 6 being in the raised posture may include a state in which the line connecting the rotation axis AXa and the rotation axis AXb is inclined upward toward the front with respect to the reference line. In a case where the reference line is parallel to the horizontal plane, the work implement 6 being in the raised posture includes a state in which, in the vertical direction, a distance between the rotation axis AXb and the reference line is longer than a distance between the rotation axis AXa and the reference line.
As described with reference to Fig. 10, when an excavated object is loaded into the dump body of the dump truck 300, the bucket 13 performs the dump operation while the distal end portion of the boom 12 is raised. The raised posture of the work implement 6 may be regarded as a posture when the work implement 6 loads an excavated object into the dump body of the dump truck 300.
In a case where it is determined in step S2 that the work implement 6 is in the raised posture (step S2: Yes), the operation determination unit 104 determines, based on an operation signal from the boom lever 75, whether the boom 12 is performing a lowering operation from the raised posture. Note that the operation determination unit 104 may determine whether the boom 12 is performing the lowering operation based on detection data of the boom angle sensor 28A (step S3).
Each of Figs. 13 and 14 is a diagram illustrating an example of a relationship between the operation signal from the boom lever 75 and the height of the boom 12 according to the embodiment. In the following description, the operation signal from the boom lever 75 is also referred to as a boom lever signal, as appropriate. In Figs. 13 and 14, a horizontal axis represents elapsed time from a time point at which the work implement 6 is determined to be in the raised posture, and a vertical axis represents a height of the distal end portion of the boom 12, the boom lever signal, and a change rate of the boom lever signal.
A positive value of the boom lever signal means that the boom lever 75 has been operated from the neutral position of the boom lever 75 to one side such that the boom 12 performs the raising operation, and a negative value of the boom lever signal means that the boom lever 75 has been operated from the neutral position of the boom lever 75 to the other side such that the boom 12 performs the lowering operation. That is, a positive value of the boom lever signal means that the boom 12 has performed the raising operation, and a negative value of the boom lever signal means that the boom 12 has performed the lowering operation.
The boom lever signal includes an operation amount of the boom lever 75. The larger the absolute value of the boom lever signal, the larger the operation amount of the boom lever 75. The boom lever signal and a boom speed indicating an extension/contraction speed of the boom cylinder 18 correspond to each other on a one-to-one basis. The larger the absolute value of the boom lever signal, the higher the boom speed. A smaller absolute value of the boom lever signal means a lower boom speed.
A change rate of the boom lever signal refers to a change amount of the boom lever signal per unit time. The change rate of the boom lever signal includes a change rate of the operation amount of the boom lever 75. A larger change rate of the boom lever signal means that the boom lever 75 has been operated abruptly. The change rate of the boom lever signal and a boom acceleration indicating an extension/contraction acceleration of the boom cylinder 18 correspond to each other on a one-to-one basis. The larger the change rate of the boom lever signal, the higher the boom acceleration. The smaller the change rate of the boom lever signal, the lower the boom acceleration.
When the boom lever 75 is abruptly operated, the change rate of the boom lever signal increases. As described with reference to Fig. 10, after an excavated object is loaded into the dump body of the dump truck 300, the operator causes the boom 12 to perform a lowering operation. In a case where the boom lever 75 is operated to interrupt the lowering operation while the boom lever 75 is being operated such that the boom 12 performs the lowering operation, the change rate of the boom lever signal increases. Examples of the operation of the boom lever 75 for interrupting the lowering operation of the boom 12 include operating the boom lever 75 so as to abruptly decelerate or abruptly stop the boom 12 while the boom 12 is performing the lowering operation, and operating the boom lever 75 so as to cause the boom 12 to abruptly perform a raising operation while the boom 12 is performing the lowering operation. In a case where the boom lever 75 is operated so as to interrupt the lowering operation of the boom 12, a change rate of an operation signal from the boom lever 75 increases.
In a case where it is determined in step S3 that the boom 12 is performing the lowering operation (step S3: Yes), the work implement control unit 107 determines, based on an operation signal from the boom lever 75, whether to start intervention control of the boom 12 (step S4).
The work implement control unit 107 determines whether a change rate of the operation signal from the boom lever 75 acquired by the operation signal acquisition unit 102 exceeds the predetermined threshold value Sh while the work implement 6 is performing the lowering operation from the raised posture. In the embodiment, the threshold value Sh includes the threshold value Shc when the work implement 6 is in a loaded state and the threshold value She when the work implement 6 is in an unloaded state.
Fig. 13 illustrates an example in which the change rate of the boom lever signal does not exceed the threshold value She and the threshold value Shc. The threshold value Shc when the work implement 6 is in the loaded state is smaller than the threshold value She when the work implement 6 is in the unloaded state. As described above, in a case where the work implement 6 is in the loaded state, the threshold value Sh is set to the threshold value Shc. In a case where the work implement 6 is in the unloaded state, the threshold value Sh is set to the threshold value She. In a case where the work implement 6 is in the loaded state, the work implement control unit 107 determines whether the change rate of the boom lever signal exceeds the threshold value Shc. In a case where the work implement 6 is in the unloaded state, the work implement control unit 107 determines whether the change rate of the boom lever signal exceeds the threshold value She. In the following description, as an example, it is assumed that the work implement 6 is in an unloaded state and that the threshold value Sh is set to the threshold value She.
In Fig. 13, time point t1 is a time point at which an operation of the boom lever 75 is started so as to cause the boom 12 in the raised posture to perform a lowering operation. Time point t2 is a time point at which the boom lever 75 is operated from the neutral position to the other side and reaches a certain position. Time point t3 is a time point at which an operation of the boom lever 75 is started so as to cause the lowering operation of the boom 12 to end. Time point t4 is a time point at which the boom lever 75 is placed at the neutral position.
Fig. 14 illustrates an example in which a change rate of the boom lever signal exceeds the threshold value She. In the example illustrated in Fig. 14, time point t3 is a time point at which the boom lever 75 is operated such that the lowering operation of the boom 12 is abruptly stopped. Since the lowering operation of the boom 12 is abruptly stopped at time point t3, a change rate of the boom lever signal after time point t3 becomes large. In Fig. 14, time point t3a is a time point at which the change rate of the boom lever signal exceeds the threshold value She. Time point t3a is a time point later than time point t3 and earlier than time point t4. Time point t4a is a time point at which the boom lever 75 is placed at the neutral position. Time point 4a is a time point later than time point t3a and earlier than time point t4. Since the boom lever 75 is abruptly operated to return to the neutral position such that the boom 12 is abruptly stopped while the boom 12 is performing the lowering operation, the change rate of the boom lever signal from time point t3 to time point t4a becomes large.
In the case of the change rate of the boom lever signal illustrated in Fig. 13, the work implement control unit 107 determines that the change rate of the boom lever signal does not exceed the threshold value She. In the case of the change rate of the boom lever signal illustrated in Fig. 14, the work implement control unit 107 determines that the change rate of the boom lever signal exceeds the threshold value She.
In a case where it is determined that the change rate of the boom lever signal does not exceed the threshold value She, the work implement control unit 107 determines not to start the intervention control of the boom 12. In a case where it is determined that the change rate of the boom lever signal exceeds the threshold value She, the work implement control unit 107 determines to start the intervention control of the boom 12.
In a case where it is determined in step S4 that the intervention control of the boom 12 is to be started (step S4: Yes), the work implement control unit 107 outputs a control command such that the change rate of the boom lever signal becomes equal to or less than the threshold value She. In the example illustrated in Fig. 14, since the work implement 6 is in the unloaded state, the work implement control unit 107 outputs a control command such that the change rate of the boom lever signal becomes equal to or less than the threshold value She. In a case where the work implement 6 is in the loaded state, the work implement control unit 107 outputs a control command such that the change rate of the boom lever signal becomes equal to or less than the threshold value Shc.
In the embodiment, the intervention control of the boom 12 includes performing limiting processing to reduce the change rate of the boom lever signal while the boom lever signal is being acquired by the operation signal acquisition unit 102. The work implement control unit 107 performs the limiting processing such that the change rate of the boom lever signal is reduced while the boom lever signal is being acquired by the operation signal acquisition unit 102 (step S5).
In Fig. 14, dotted lines indicate the height of the boom 12, the boom lever signal, and the change rate of the boom lever signal in a case where the intervention control is performed. Solid lines indicate the height of the boom 12, the boom lever signal, and the change rate of the boom lever signal in a case where the intervention control is not performed.
As indicated by the dotted lines in Fig. 14, the work implement control unit 107 performs limiting processing on the boom lever signal acquired by the operation signal acquisition unit 102 to reduce the change rate of the boom lever signal. By the limiting processing, a boom lever signal having a smaller change rate is generated. By the limiting processing, the change rate of the boom lever signal is suppressed to a value equal to the threshold value She or a value less than the threshold value She. The work implement control unit 107 outputs a control command for controlling the bucket control valve 39 based on the boom lever signal subjected to the limiting processing. The bucket control valve 39 is driven based on the bucket lever signal subjected to the limiting processing (step S6).
The work implement control unit 107 performs intervention control such that the change rate of the boom lever signal becomes smaller after time point t3a at which the change rate of the boom lever signal exceeds the threshold value She. The work implement control unit 107 performs limiting processing such that the change rate of the boom lever signal becomes smaller after time point t3a. By performing the intervention control, the change rate of the boom lever signal after time point t3a becomes smaller. Since the change rate of the boom lever signal becomes smaller, an operation acceleration of the boom 12 is reduced. By performing the intervention control, the boom 12 transitions from the lowering operation to a stopped state with a low acceleration.
A stop position of the boom 12 when the intervention control is performed while the boom 12 is performing the lowering operation is lower than a stop position of the boom 12 when the intervention control is not performed. As illustrated in Fig. 14, for example, in a case where the operator intends to stop the boom 12 performing the lowering operation, at a height Hg, when the intervention control is performed, the boom 12 is lowered to a height Ha lower than the height Hg. That is, when the intervention control is performed, the work implement 6 is lowered to the height Ha lower than the height Hg intended by the operator.
The work implement control unit 107 determines whether to terminate the intervention control (step S7). In a case where it is determined in step S7 that the intervention control is not to be terminated (step S7: No), the work implement control unit 107 returns to the processing of step S5. In a case where it is determined in step S7 that the intervention control is to be terminated (step S7: Yes), the processing returns to step S1.
In a case where it is determined in step S2 that the work implement 6 is not in the raised posture (step S2: No), in a case where it is determined in step S3 that the boom 12 is not performing the lowering operation (step S3: No), and in a case where it is determined in step S4 that the intervention control of the boom 12 is not to be started (step S4: No), the work implement control unit 107 does not perform the limiting processing on the boom lever signal, and outputs a control command for controlling the boom control valve 38 based on the operation signal acquired by the operation signal acquisition unit 102. The boom control valve 38 is driven based on the boom lever signal that has not been subjected to the limiting processing (step S8).

As described above, according to the embodiment, the on-board controller 30 includes the operation signal acquisition unit 102 that acquires an operation signal from the operation device 7 operated to actuate the work implement 6 of the work machine 1, and the work implement control unit 107 that outputs a control command such that the change rate becomes smaller in a case where the change rate of the operation signal is large while the work implement 6 is performing the lowering operation from the raised posture in which the work implement 6 has been raised to the predetermined height Hp or higher. In the embodiment, in a case where it is determined that the change rate of the operation signal exceeds the threshold value Sh, the work implement control unit 107 outputs a control command such that the change rate becomes equal to or less than the threshold value Sh.
In a case where the boom lever 75 is operated to interrupt the lowering operation of the boom 12, a weight balance of the work machine 1 may be disrupted. When the boom lever 75 is operated to abruptly decelerate or abruptly stop the boom 12 while the boom 12 is performing the lowering operation, or when the boom lever 75 is operated to cause the boom 12 to abruptly perform the raising operation while the boom 12 is performing the lowering operation, the weight balance of the work machine 1 changes such that the rear wheels 5R of the work machine 1 lift off the ground. When the weight balance of the work machine 1 changes, a localized load is applied to the work machine 1, and the vehicle body 2 and the work implement 6 of the work machine 1 may deteriorate prematurely.
According to the embodiment, in a case where an operation signal from the boom lever 75 for interrupting the lowering operation of the boom 12 is acquired, intervention control is performed such that the lowering operation of the boom 12 is not abruptly interrupted. Therefore, deterioration of the vehicle body 2 and the work implement 6 of the work machine 1 is suppressed.
In a case where the work machine 1 is remotely operated, the operator in the remote operation room 202 has difficulty perceiving that the weight balance of the work machine 1 is disrupted even when the boom lever 75 is abruptly operated. Therefore, the operator in the remote operation room 202 may unconsciously operate the boom lever 75 abruptly. According to the embodiment, in a case where the boom lever 75 is abruptly operated, intervention control is performed such that the lowering operation of the boom 12 is not abruptly interrupted. Therefore, deterioration of the work machine 1 is suppressed.
In the embodiment, the threshold value Sh includes the threshold value Shc when the work implement 6 is in a loaded state and the threshold value She when the work implement 6 is in an unloaded state. A moment applied from the work implement 6 to the vehicle body 2 when the work implement 6 is in the loaded state is larger than a moment applied from the work implement 6 to the vehicle body 2 when the work implement 6 is in the unloaded state. Therefore, in a case where the work implement 6 is in the loaded state, the weight balance of the work machine 1 may be greatly disturbed when the lowering operation of the boom 12 is abruptly interrupted. According to the embodiment, since the threshold value Sh is set to the smaller threshold value Shc while the work implement 6 is in the loaded state, in the intervention control, the change rate of the boom lever signal when the work implement 6 is in the loaded state becomes smaller than the change rate of the boom lever signal when the work implement 6 is in the unloaded state. Therefore, even when the work implement 6 is in the loaded state, a large disturbance of the weight balance of the work machine 1 is suppressed.

As described above, a stop position of the boom 12 when the intervention control is performed while the boom 12 is performing the lowering operation is lower than a stop position of the boom 12 when the intervention control is not performed. As described with reference to Fig. 14, for example, in a case where the operator intends to stop the boom 12 performing the lowering operation, at a height Hg, when the intervention control is performed, the boom 12 is lowered to a height Ha lower than the height Hg. In a case where the height Ha is higher than the ground, even when the intervention control is performed, the bucket 13 can stop at the height Ha without coming into contact with the ground.
In the above-described embodiment, in a case where it is determined that the change rate of the boom lever signal exceeds the threshold value Sh, the work implement control unit 107 outputs a control command such that the change rate of the boom lever signal becomes equal to or less than the threshold value Sh. The work implement control unit 107 may output a control command without using the threshold value Sh. The work implement control unit 107 may output a control command such that, in a case where the change rate of the boom lever signal is large, the change rate of the boom lever signal becomes smaller.
For example, in a case where the work implement control unit 107 outputs control commands at a constant control cycle, a weighted average of a command value of a previous control command and a command value of a control command corresponding to a current boom lever signal is calculated, and a value of the calculated weighted average is set as a command value of the current control command. In a case where the change rate of the boom lever signal is large, the work implement control unit 107 increases a weight w1 for the command value of the previous control command and decreases a weight w2 for the command value of the control command corresponding to the current boom lever signal. The command value of the current control command is calculated, for example, based on the following Expression (1). [Command value of current control command] = w1 × [Command value of previous control command] + w2 × [Command value of control command corresponding to current boom lever signal]
The weight w1 and the weight w2 satisfy a relationship of the following Expression (2). $w 1 + w 2 = 1$
For example, in a case where a control cycle by the work implement control unit 107 is 10 [msec], an initial value of the weight w1 is 0.91, and an initial value of the weight w2 is 0.09, when the change rate of the boom lever signal is large, the work implement control unit 107 changes the weight w1 to 0.98 and changes the weight w2 to 0.02.
In the above-described embodiment, the load sensor 27 that detects the loaded state of the work implement 6 includes a weight sensor that detects a weight of the work implement 6. The load sensor 27 may include, for example, a camera that images the bucket 13. The camera can image an excavated object held in the bucket 13. Image data of the excavated object acquired by the camera is transmitted to the on-board controller 30. Density data indicating a density of the excavated object is stored in advance in the on-board controller 30. The sensor data acquisition unit 101 of the on-board controller 30 estimates a volume of the excavated object held in the bucket 13 based on the image data of the excavated object. The sensor data acquisition unit 101 can calculate a weight of the excavated object held in the bucket 13 based on the estimated volume of the excavated object and the density data of the excavated object. Note that a three-dimensional shape of the excavated object may be detected by a three-dimensional sensor such as a laser scanner or a stereo camera. The sensor data acquisition unit 101 may estimate a volume of the excavated object held in the bucket 13 based on the three-dimensional shape of the excavated object.
In the above-described embodiment, in a case where the camera 29 images the work implement 6, the operation determination unit 104 may determine whether the boom 12 is performing a lowering operation based on the image data of the work implement 6 captured by the camera 29.
In the above-described embodiment, in a case where the intervention control is started, notification data indicating that the intervention control has been started may be output from the display device 8.
In the above-described embodiment, some or all of the functions of the on-board controller 30 may be provided in the remote controller 9. For example, the posture determination unit 103 and the operation determination unit 104 may be provided in the remote controller 9.
In the above-described embodiment, the work machine 1 does not have to be remotely operated. The operator may board the cab 4 of the work machine 1 and operate the work machine 1.
In the above-described embodiment, the work machine 1 is a wheel loader. The work machine 1 may be a hydraulic excavator having a front-loading type work implement. The work machine 1 may also be a hydraulic excavator having a backhoe-type work implement in which an opening portion of a bucket faces rearward during excavation work.

[Supplementary Note]

The present disclosure can also adopt the following configurations.

(Supplementary Note 1)

A control system for a work machine, the control system including:

a controller,
in which the controller determines a presence or absence of a predetermined operation in which a bucket of a work implement of the work machine repeatedly performs a tilt operation and a dump operation, and
in a case where it is determined that the predetermined operation has been performed and it is determined that an operation speed of the predetermined operation exceeds a threshold value, the controller outputs a control command such that the operation speed becomes equal to or less than the threshold value.

(Supplementary Note 2)

The control system for a work machine according to (Supplementary Note 1),
in which the controller determines whether a height of the work implement is equal to or higher than a predetermined height based on detection data of a work implement posture sensor that detects a posture of the work implement.

(Supplementary Note 3)

The control system for a work machine according to (Supplementary Note 1) or (Supplementary Note 2),
in which the controller determines whether a bottom surface of the bucket is inclined downward toward the front.

(Supplementary Note 4)

The control system for a work machine according to (Supplementary Note 3),

in which the work machine includes front wheels and rear wheels,
in a case where a line connecting a rotation axis of the front wheels and a rotation axis of the rear wheels is defined as a reference line, the controller determines whether the bottom surface of the bucket is inclined downward toward the front with respect to the reference line.

(Supplementary Note 5)

The control system for a work machine according to (Supplementary Note 4),

in which the work implement includes a boom pivotably connected to a vehicle body of the work machine about a first rotation axis,
the bucket is pivotably connected to the boom about a second rotation axis, and
the controller determines whether the second rotation axis is disposed above the first rotation axis.

(Supplementary Note 6)

The control system for a work machine according to any one of (Supplementary Note 1) to (Supplementary Note 5),
in which the controller determines the presence or absence of the predetermined operation based on an operation signal from a bucket lever operated for operating the bucket.

(Supplementary Note 7)

The control system for a work machine according to (Supplementary Note 6),

in which the bucket performs the tilt operation by the bucket lever being operated to one side with respect to a neutral position of the bucket lever,
the bucket performs the dump operation by the bucket lever being operated to the other side with respect to the neutral position, and
the controller determines that the predetermined operation has been performed in a case where it is determined that the number of times the bucket lever has been subjected to a reciprocating operation between the one side and the other side with respect to the neutral position is equal to or greater than a predetermined number of times within a predetermined time.

(Supplementary Note 8)

The control system for a work machine according to (Supplementary Note 7),
in which the controller determines whether an operation speed of the predetermined operation exceeds the threshold value based on an amplitude of the operation signal.

(Supplementary Note 9)

The control system for a work machine according to (Supplementary Note 8),
in which the controller outputs the control command such that the amplitude of the operation signal becomes smaller while the operation signal is being acquired from the bucket lever.

(Supplementary Note 10)

A work machine including:
the control system for a work machine according to any one of (Supplementary Note 1) to (Supplementary Note 9) .

(Supplementary Note 11)

A remote operation system for a work machine, the remote operation system including:
the control system for a work machine according to any one of (Supplementary Note 1) to (Supplementary Note 9) .

(Supplementary Note 12)

A control method for a work machine, the control method including:

by a controller,
determining whether a predetermined posture in which a height of a work implement of the work machine is equal to or higher than a predetermined height is obtained;
determining, in a case where it is determined that the predetermined posture is obtained, a presence or absence of a predetermined operation in which a bucket of the work implement repeatedly performs a tilt operation and a dump operation; and
outputting, in a case where it is determined that the predetermined operation has been performed and it is determined that an operation speed of the predetermined operation exceeds a threshold value, a control command such that the operation speed becomes equal to or less than the threshold value.

(Supplementary Note 13)

A control system for a work machine, the control system including:

a controller,
in which the controller acquires an operation signal from an operation device operated for operating a work implement of a work machine, and
in a case where a sudden operation of the operation device is performed while the work implement is performing a lowering operation from a raised posture in which the work implement is raised, and a weight balance of the work machine changes, the controller outputs a control command such that a change rate of the operation signal becomes smaller.

(Supplementary Note 14)

The control system for a work machine according to (Supplementary Note 13),
in which the controller determines whether the work implement is in the raised posture based on detection data of a work implement posture sensor that detects a posture of the work implement.

(Supplementary Note 15)

The control system for a work machine according to (Supplementary Note 13) or (Supplementary Note 14),
in which the controller determines whether the work implement is performing the lowering operation based on detection data of a work implement posture sensor that detects a posture of the work implement or the operation signal.

(Supplementary Note 16)

The control system for a work machine according to any one of (Supplementary Note 13) to (Supplementary Note 15),

in which the work implement includes a boom pivotably connected to a vehicle body of the work machine about a first rotation axis, and a bucket pivotably connected to the boom about a second rotation axis, and
being in the raised posture includes a state in which the second rotation axis is disposed above the first rotation axis.

(Supplementary Note 17)

The control system for a work machine according to any one of (Supplementary Note 13) to (Supplementary Note 16),
in which in a case where it is determined that a change rate of the operation signal exceeds a threshold value, the controller outputs a control command such that the change rate becomes equal to or less than the threshold value.

(Supplementary Note 18)

The control system for a work machine according to (Supplementary Note 17),
in which the controller includes a threshold value setting unit that changes the threshold value based on detection data of a load sensor that detects a loaded state of the work implement.

(Supplementary Note 19)

The control system for a work machine according to (Supplementary Note 18),
in which the controller determines whether the work implement is in a loaded state or in an unloaded state based on detection data of the load sensor, and sets a threshold value in the loaded state to be smaller than a threshold value in the unloaded state.

(Supplementary Note 20)

The control system for a work machine according to (Supplementary Note 18) or (Supplementary Note 19),
in which the load sensor includes a weight sensor that detects a weight of the work implement.

(Supplementary Note 21)

A work machine including:
the control system for a work machine according to any one of (Supplementary Note 13) to (Supplementary Note 20).

(Supplementary Note 22)

A remote operation system for a work machine, the remote operation system including:
the control system for a work machine according to any one of (Supplementary Note 13) to (Supplementary Note 21).

(Supplementary Note 23)

A control method for a work machine, the control method including:

by a controller,
acquiring an operation signal from an operation device operated for operating a work implement of a work machine; and
outputting, in a case where a change rate of the operation signal is large while the work implement is performing a lowering operation from a raised posture in which the work implement is raised to a predetermined height or higher, a control command such that the change rate becomes smaller.

Reference Signs List

1: work machine
2: vehicle body
2F: front frame
2R: rear frame
3: articulation mechanism
4: cab
5: wheel
5F: front wheel
5R: rear wheel
6: work implement
7: operation device
7A: traveling-system operation device
7B: work-implement operation device
8: display device
9: remote controller
10: operator seat
11: articulation cylinder
12: boom
13: bucket
13A: blade tip portion
13B: opening portion
13C: bottom surface
14: bell crank
15: bucket link
16: bracket
17: bracket
18: boom cylinder
19: bucket cylinder
20: engine
21: power take-off
22: power transmission device
23: brake device
24: steering pump
26: work implement pump
27: load sensor
28: work implement posture sensor
28A: boom angle sensor
28B: bucket angle sensor
29: camera
30: on-board controller
31: processor
32: main memory
33: storage
34: input/output interface
35: communication interface
37: steering control valve
38: boom control valve
39: bucket control valve
71: accelerator pedal
72: brake pedal
73: steering wheel
74: forward/reverse switching lever
75: boom lever
76: bucket lever
100: control system
101: sensor data acquisition unit
102: operation signal acquisition unit
103: posture determination unit
104: operation determination unit
105: threshold value setting unit
106: traveling control unit
107: work implement control unit
108: transmission unit
200: remote operation system
201: work site
202: remote operation room
203: communication system
300: dump truck
700: operation device
AXa: rotation axis (first rotation axis)
AXb: rotation axis (second rotation axis)
AXc: rotation axis
AXd: rotation axis
AXe: rotation axis
AXf: rotation axis
CXf: rotation axis
CXr: rotation axis
RL: reference line

Claims

A control system for a work machine, the control system comprising:
a controller,

wherein the controller determines a presence or absence of a predetermined operation in which a bucket of a work implement of the work machine repeatedly performs a tilt operation and a dump operation, and

in a case where it is determined that the predetermined operation has been performed and it is determined that an operation speed of the predetermined operation exceeds a threshold value, the controller outputs a control command such that the operation speed becomes equal to or less than the threshold value.
The control system for a work machine according to claim 1,
wherein the controller determines whether a height of the work implement is equal to or higher than a predetermined height based on detection data of a work implement posture sensor that detects a posture of the work implement.
The control system for a work machine according to claim 1,
wherein the controller determines whether a bottom surface of the bucket is inclined downward toward the front.
The control system for a work machine according to claim 3,
wherein the work machine includes front wheels and rear wheels,

in a case where a line connecting a rotation axis of the front wheels and a rotation axis of the rear wheels is defined as a reference line, the controller determines whether the bottom surface of the bucket is inclined downward toward the front with respect to the reference line.
The control system for a work machine according to claim 4,
wherein the work implement includes a boom pivotably connected to a vehicle body of the work machine about a first rotation axis,

the bucket is pivotably connected to the boom about a second rotation axis, and

the controller determines whether the second rotation axis is disposed above the first rotation axis.
The control system for a work machine according to claim 1,
wherein the controller determines the presence or absence of the predetermined operation based on an operation signal from a bucket lever operated for operating the bucket.
The control system for a work machine according to claim 6,
wherein the bucket performs the tilt operation by the bucket lever being operated to one side with respect to a neutral position of the bucket lever,

the bucket performs the dump operation by the bucket lever being operated to the other side with respect to the neutral position, and

the controller determines that the predetermined operation has been performed in a case where it is determined that the number of times the bucket lever has been subjected to a reciprocating operation between the one side and the other side with respect to the neutral position is equal to or greater than a predetermined number of times within a predetermined time.
The control system for a work machine according to claim 7,
wherein the controller determines whether an operation speed of the predetermined operation exceeds the threshold value based on an amplitude of the operation signal.
The control system for a work machine according to claim 8,
wherein the controller outputs the control command such that the amplitude of the operation signal becomes smaller while the operation signal is being acquired from the bucket lever.
A work machine comprising:
the control system for a work machine according to claim 1.
A remote operation system for a work machine, the remote operation system comprising:
the control system for a work machine according to claim 1.
A control method for a work machine, the control method comprising:
by a controller,

determining whether a height of a work implement of the work machine is equal to or higher than a predetermined height;

determining, in a case where it is determined that the height of the work implement is equal to or higher than the predetermined height, a presence or absence of a predetermined operation in which a bucket of the work implement repeatedly performs a tilt operation and a dump operation; and

outputting, in a case where it is determined that the predetermined operation has been performed and it is determined that an operation speed of the predetermined operation exceeds a threshold value, a control command such that the operation speed becomes equal to or less than the threshold value.
A control system for a work machine, the control system comprising:
a controller,

wherein the controller acquires an operation signal from an operation device operated for operating a work implement of a work machine, and

in a case where a sudden operation of the operation device is performed while the work implement is performing a lowering operation from a raised posture in which the work implement is raised, and a weight balance of the work machine changes, the controller outputs a control command such that a change rate of the operation signal becomes smaller.
The control system for a work machine according to claim 13,
wherein the controller determines whether the work implement is in the raised posture based on detection data of a work implement posture sensor that detects a posture of the work implement.
The control system for a work machine according to claim 13,
wherein the controller determines whether the work implement is performing the lowering operation based on detection data of a work implement posture sensor that detects a posture of the work implement or the operation signal.
The control system for a work machine according to claim 13,
wherein the work implement includes a boom pivotably connected to a vehicle body of the work machine about a first rotation axis, and a bucket pivotably connected to the boom about a second rotation axis, and

being in the raised posture includes a state in which the second rotation axis is disposed above the first rotation axis.
The control system for a work machine according to claim 13,
wherein in a case where it is determined that a change rate of the operation signal exceeds a threshold value, the controller outputs a control command such that the change rate becomes equal to or less than the threshold value.
The control system for a work machine according to claim 17,
wherein the controller changes the threshold value based on detection data of a load sensor that detects a loaded state of the work implement.
The control system for a work machine according to claim 18,
wherein the controller determines whether the work implement is in a loaded state or in an unloaded state based on detection data of the load sensor, and sets a threshold value in the loaded state to be smaller than a threshold value in the unloaded state.
The control system for a work machine according to claim 18,
wherein the load sensor includes a weight sensor that detects a weight of the work implement.
A work machine comprising:
the control system for a work machine according to claim 13.
A remote operation system for a work machine, the remote operation system comprising:
the control system for a work machine according to claim 13.
A control method for a work machine, the control method comprising:
by a controller,

acquiring an operation signal from an operation device operated for operating a work implement of a work machine; and

outputting, in a case where a change rate of the operation signal is large while the work implement is performing a lowering operation from a raised posture in which the work implement is raised to a predetermined height or higher, a control command such that the change rate becomes smaller.