Work machine control system, work machine, work machine remote operation system, and work machine control method

Abstract

To suppress collapse of a load held by a work machine. A work machine control system includes a processor that receives operation signals from an operation device operated to operate a work machine having a work implement and a traveling gear, calculates constraint conditions for preventing a load held by the work implement from collapsing based on vehicle state parameters that indicate the operating state of the work machine, and modifies the operation signals based on the constraint conditions.

Description

[Technical Field]

[0001] The present disclosure relates to a work machine control system, a work machine, a work machine remote operation system, and a work machine control method. [Background technology]

[0002] In the technical field related to work machines, a remote control system for a wheel loader is known, as disclosed in Patent Document 1. In Patent Document 1, the wheel loader has 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 a camera image from the camera and displays it on a display. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] European Patent Application Publication No. 3926107 Summary of the Invention [Problem to be solved by the invention]

[0004] A work machine operates based on an operation signal from an operation device operated by an operator. When the operation device is suddenly operated, the state of the work machine changes suddenly. When the state of the work machine changes suddenly, there is a possibility that a load held by the working implement of the work machine may collapse.

[0005] The present disclosure aims to prevent a load held by a work machine from collapsing. [Means for solving the problem]

[0006] According to the present disclosure, there is provided a work machine control system including a processor, which receives an operation signal from an operation device operated to operate a work machine having a work implement and a traveling device, calculates constraint conditions for preventing a load held by the work implement from collapsing based on vehicle state parameters that indicate the operating state of the work machine, and modifies the operation signal based on the constraint conditions. [Effects of the Invention]

[0007] According to the present disclosure, collapse of a load held by a work machine is suppressed. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing a remote control system for a work machine according to a first embodiment. [Figure 2] FIG. 2 is a configuration diagram showing a work machine and an operating device according to the first embodiment. [Figure 3] FIG. 3 is a hardware configuration diagram showing the in-vehicle controller according to the first embodiment. [Figure 4] FIG. 4 is a block diagram showing the control system for the work machine according to the first embodiment. [Figure 5] FIG. 5 is a diagram illustrating constraints for preventing a load held in the bucket of the work machine according to the first embodiment from collapsing. [Figure 6] FIG. 6 is a diagram illustrating constraints for preventing a load held in the bucket of the work machine according to the first embodiment from collapsing. [Figure 7] FIG. 7 is a diagram illustrating the processing of the in-vehicle controller according to the first embodiment. [Figure 8] FIG. 8 is a diagram illustrating the operation of the work machine according to the first embodiment. [Figure 9] FIG. 9 is a flowchart showing a control method for a work machine according to the first embodiment. [Figure 10] FIG. 10 is a flowchart showing a control method for a work machine according to the second embodiment. [Figure 11]FIG. 11 is a schematic view of a work machine according to a third embodiment, viewed from above. [Figure 12] FIG. 12 is a schematic view of a work machine according to a third embodiment, viewed from above. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, the present embodiment according to the present disclosure will be described with reference to the drawings, but the present disclosure is not limited to the embodiment. The components of the embodiment described below can be combined as appropriate. In addition, some components may not be used.

[0010] [First embodiment] A first embodiment will be described.

[0011] <Remote control system> 1 is a diagram showing a remote operation system 200 for a work machine 1 according to this embodiment. The remote operation system 200 remotely operates a work machine 1 located 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 comprises an operation device 70, a display device 80, an input device 81, and a remote controller 82.

[0012] The operation device 70 is arranged in a remote control room 202 outside the work machine 1. The operation device 70 is operated by an operator in the remote control room 202. The operator can operate the operation device 70 while seated in the operator's seat 83. The operator may also operate a portable operation device 700. The operation device 700 may be operated outside the remote control room 202.

[0013] The display device 80 is disposed in a remote control room 202 outside the work machine 1. An example of the display device 80 is a flat panel display such as a liquid crystal display or an organic EL display. The display device 80 displays at least an image of the work site 201. The display device 80 may also output audio of the work site 201.

[0014] The operator operates the operation device 70 while checking an image of the work site 201 displayed on the display device 80. The work machine 1 is remotely controlled by the operation device 70.

[0015] The input device 81 is arranged in a remote control room 202 outside the work machine 1. The input device 81 is operated by an operator in the remote control room 202. Examples of the input device 81 include a computer keyboard, a touch panel, a mouse, and a voice input device.

[0016] The remote controller 82 is placed in a remote operation room 202 outside the work machine 1. The remote controller 82 and the work machine 1 communicate via a communication system 203. Examples of the communication system 203 include the internet, a local area network (LAN), a mobile phone communication network, and a satellite communication network.

[0017] <Work machinery> In this embodiment, the work machine 1 is a wheel loader. As shown in Fig. 1, the work machine 1 comprises a vehicle body 2, a traveling device 5 including an articulated cylinder 7 and wheels 4, and a work implement 6. The work machine 1 travels on the traveling device 5 at a work site 201. The work machine 1 performs work at the work site 201 using the work implement 6. Examples of work performed by the work machine 1 include excavation work, loading work, and transport work.

[0018] The vehicle body 2 supports a 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 via an articulation mechanism 3.

[0019] The traveling gear 5 supports the vehicle body 2. The traveling gear 5 includes wheels 4 and an articulating cylinder 7. The wheels 4 include front wheels 4F attached to the front frame 2F and rear wheels 4R attached to the rear frame 2R. The wheels 4 include tires. The articulating cylinder 7 connects the front frame 2F and the rear frame 2R. The articulating cylinder 7 is a hydraulic cylinder. When the articulating cylinder 7 extends and retracts, the front frame 2F bends left and right relative to the rear frame 2R. When the front frame 2F bends relative to the rear frame 2R, the traveling direction of the work machine 1 is adjusted. The articulating cylinder 7 is an example of a steering device for the work machine 1.

[0020] 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 has a boom 8, a bucket 9, a bell crank 10, a bucket link 11, a boom cylinder 12, and a bucket cylinder 13.

[0021] The base end of the boom 8 is rotatably connected to the front frame 2F. The base end of the bucket 9 is rotatably connected to the tip end of the boom 8. The middle portion of the bell crank 10 is rotatably connected to a bracket 14 of the boom 8. The lower end of the bell crank 10 is rotatably connected to the base end of a bucket link 11. The tip end of the bucket link 11 is rotatably connected to a bracket 15 of the bucket 9. The bell crank 10 is connected to the bucket 9 via the bucket link 11.

[0022] The bucket 9 is a working member that excavates an excavation target. The bucket 9 is replaceable with another working member. An example of the other working member is a fork that transports an object to be transported.

[0023] The boom 8 is operated by a boom cylinder 12. The boom cylinder 12 is a hydraulic cylinder. A base end of the boom cylinder 12 is connected to the front frame 2F. A tip end of the boom cylinder 12 is connected to the boom 8. The bucket 9 is operated by a bucket cylinder 13. The bucket cylinder 13 is a hydraulic cylinder. A base end of the bucket cylinder 13 is connected to the front frame 2F. A tip end of the bucket cylinder 13 is connected to the upper end of the bell crank 10.

[0024] In this embodiment, the work implement 6 is a front-loading type work implement in which the opening of the bucket 9 faces forward during excavation work. The boom cylinder 12 extends and retracts to perform a raising or lowering operation of the boom 8. The bucket cylinder 13 extends and retracts to perform a tilting or dumping operation of the bucket 9.

[0025] <Configuration of work machine and operating device> Fig. 2 is a configuration diagram showing a work machine 1 and an operation device 70 according to this embodiment. As shown in Fig. 2, the work machine 1 includes a drive unit 16, a power take-off (PTO) 17, a power transmission device 18, wheels 4, a brake device 19, a steering pump 20, a steering control valve 21, an articulated cylinder 7, a work implement pump 22, a work implement control valve 23, a boom cylinder 12, a bucket cylinder 13, a position sensor 24, a direction sensor 25, a speed sensor 26, a steering sensor 27, a work implement attitude sensor 28, an external sensor 29, a load sensor 30, a camera 31, and an on-board controller 32. The traveling device 5 includes the power transmission device 18, the brake device 19, wheels 4, and the articulated cylinder 7.

[0026] The drive machine 16 is the drive source of the work machine 1. The drive machine 16 is supported on the vehicle body 2. Examples of the drive machine 16 include a diesel engine and an electric motor. A power take-off 17 distributes the driving force of the drive machine 16 to a power transmission device 18, a steering pump 20, and a work machine pump 22.

[0027] The power transmission device 18 transmits the driving force of the drive machine 16 to the wheels 4. The power transmission device 18 controls the traveling speed and direction of travel of the work machine 1. The traveling direction of the work machine 1 includes forward and reverse. The power transmission device 18 may be a transmission having a torque converter, or may be a transmission having multiple speed change gears. The brake device 19 slows down or stops the work machine 1 while it is traveling.

[0028] The steering pump 20 is a hydraulic pump that is operated by the driving force generated by the driving machine 16. The hydraulic oil discharged from the steering pump 20 is supplied to the articulate cylinder 7 via a steering control valve 21. The steering control valve 21 controls the flow rate and direction of the hydraulic oil supplied from the steering pump 20 to the articulate cylinder 7. The articulate cylinder 7 is operated by the hydraulic oil from the steering pump 20.

[0029] The work implement pump 22 is a hydraulic pump that operates by the driving force generated by the driving machine 16. The hydraulic oil discharged from the work implement pump 22 is supplied to each of the boom cylinder 12 and the bucket cylinder 13 via a work implement control valve 23. The work implement control valve 23 controls the flow rate and direction of the hydraulic oil supplied from the work implement pump 22 to each of the boom cylinder 12 and the bucket cylinder 13. The work implement 6 operates by the hydraulic oil from the work implement pump 22.

[0030] The position sensor 24 detects the position of the work machine 1. The position of the work machine 1 is detected using a global navigation satellite system (GNSS). The global navigation satellite system includes a global positioning system (GPS). The global navigation satellite system detects the position of a global coordinate system defined by coordinate data of latitude, longitude, and altitude. The global coordinate system is a coordinate system fixed to the Earth. The position sensor 24 includes a GNSS receiver, and detects the absolute position of the work machine 1, which indicates the position of the work machine 1 in the global coordinate system.

[0031] The orientation sensor 25 detects the orientation of the work machine 1. The orientation of the work machine 1 includes an orientation angle relative to a reference orientation. An example of the orientation sensor 25 is an inertial sensor (IMU: Inertial Measurement Unit). The orientation sensor 25 may include a calculator that calculates the orientation from position data detected by two GNSS antennas provided on the work machine 1. The calculator can calculate the orientation from a vector connecting the two GNSS antennas.

[0032] The speed sensor 26 detects the traveling speed of the work machine 1. An example of the speed sensor 26 is a magnetic sensor that detects the rotation speed of a drive shaft connected to the wheels 4.

[0033] The steering sensor 27 detects one or both of the steering angle and steering angular velocity of the work machine 1. Examples of the steering sensor 27 include a cylinder stroke sensor that detects the stroke length of the articulate cylinder 7, and an angle sensor that detects the angle of the front frame 2F relative to the rear frame 2R.

[0034] The work implement attitude sensor 28 detects the attitude of the work implement 6. The attitude of the work implement 6 includes the angle and height of the work implement 6. The work implement attitude sensor 28 includes a boom angle sensor 28A that detects the attitude of the boom 8, and a bucket angle sensor 28B that detects the attitude of the bucket 9.

[0035] The attitude of the boom 8 includes the angle and height of the boom 8. The boom angle sensor 28A detects the boom angle, which indicates the angle of the boom 8. The boom angle refers to the angle of the boom 8 relative to the vehicle body 2 in a local coordinate system defined for the work machine 1. The length of the boom 8 is known. By detecting the boom angle, the height of the tip of the boom 8 is calculated. An angle sensor arranged at the connection between the front frame 2F and the boom 8 is exemplified as the boom angle sensor 28A.

[0036] The attitude of the bucket 9 includes the angle and height of the bucket 9. Bucket angle sensor 28B detects a bucket angle that indicates the angle of the bucket 9. The bucket angle refers to the angle of the bucket 9 relative to the boom 8 in a local coordinate system defined on the work machine 1. In this embodiment, bucket angle sensor 28B detects a bell crank angle that indicates the angle of the bell crank 10 relative to the boom 8 in the local coordinate system. An example of bucket angle sensor 28B is an angle sensor that is arranged at the connection between the boom 8 and the bell crank 10. The bucket angle and the bell crank angle have a one-to-one correspondence. Bucket angle sensor 28B detects the bell crank angle. The bucket angle is calculated based on detection data of the bell crank angle and detection data of the boom angle. The dimensions of the bucket 9 are known. The height of the tip of the bucket 9 is calculated by detecting the bucket angle. The tip of the bucket 9 includes the cutting edge of the bucket 9.

[0037] Note that work implement attitude sensor 28 is not limited to an angle sensor. Work implement attitude sensor 28 may be a cylinder stroke sensor or an inclination sensor such as an inertial measurement unit (IMU). Boom angle sensor 28A may be a cylinder stroke sensor that detects the stroke length of boom cylinder 12, or may be an inclination sensor attached to boom 8. Bucket angle sensor 28B may be a cylinder stroke sensor that detects the stroke length of bucket cylinder 13, or may be an inclination sensor attached to bucket 9.

[0038] The external sensor 29 detects objects in the vicinity of the work machine 1. In this embodiment, the external sensor 29 detects the three-dimensional shapes of objects in the vicinity of the work machine 1. The external sensor 29 is disposed on at least a part of the vehicle body 2. An example of the external sensor 29 is a laser sensor (LiDAR: Light Detection and Ranging) that detects objects by emitting laser light. The external sensor 29 may also be a radar sensor (RADAR: Radio Detection and Ranging) that detects objects by emitting radio waves, or a stereo camera. In this embodiment, the external sensor 29 detects the three-dimensional shape of a load held in the bucket 9. The external sensor 29 detects obstacles in the vicinity of the work machine 1.

[0039] The load sensor 30 detects the load state of the work implement 6. The load sensor 30 detects whether the bucket 9 is in a loaded state where it holds a load, or in an empty state where it does not hold a load. In this embodiment, the load sensor 30 includes a weight sensor that detects the weight of the work implement 6. The weight of the work implement 6 differs between a loaded state where the bucket 9 holds a load and an empty state where it does not hold a load. The load sensor 30 can detect whether the work implement 6 is in a loaded state or an empty state by detecting the weight of the work implement 6. An example of the load sensor 30 is a bottom pressure sensor that detects the bottom pressure of the boom cylinder 12.

[0040] If the external sensor 29 is a three-dimensional sensor such as a laser scanner or a stereo camera, the weight of the load held in the bucket 9 may be calculated based on the detection data of the external sensor 29. If the external sensor 29 includes a three-dimensional sensor, it can detect the three-dimensional shape of the load held in the bucket 9. The on-vehicle controller 32 can estimate the volume of the load held in the bucket 9 based on the three-dimensional shape of the load detected by the external sensor 29. If the density of the load is known, the on-vehicle controller 32 can calculate the weight of the load held in the bucket 9 based on the estimated volume of the load and the load density. The external sensor 29 may include a camera. If the external sensor 29 includes a camera, it can capture an image of the load held in the bucket 9. The on-vehicle controller 32 can estimate the volume of the load held in the bucket 9 based on image data of the load.

[0041] The camera 31 captures an image of the work site 201. The camera 31 captures an image of at least the work site 201 in front of the work machine 1. The camera 31 captures an image of at least a portion of the work implement 6. The camera 31 is disposed, for example, in a cab provided on the rear frame 2R. Image data captured by the camera 31 is transmitted to the remote controller 82 via the on-board controller 32 and the communication system 203. The remote controller 82 displays the image data captured by the camera 31 on the display device 80.

[0042] The operation device 70 is operated by an operator. When operated by the operator, the operation device 70 generates an operation signal for operating the work machine 1. The operation signal generated by the operation device 70 is transmitted to the on-vehicle controller 32 via the remote controller 82 and the communication system 203. The on-vehicle controller 32 outputs a control command for operating the work machine 1 based on the operation signal transmitted from the remote controller 82. The operation device 70 includes a traveling system operation device 70A and a work implement operation device 70B.

[0043] The traveling system operation device 70A is operated by an operator to operate at least one of the driving machine 16, the power transmission device 18, and the braking device 19. The traveling system operation device 70A generates an operation signal to operate at least one of the driving machine 16, the power transmission device 18, and the braking device 19. The traveling system operation device 70A includes an accelerator pedal 71, a brake pedal 72, a steering wheel 73, and a forward / reverse switch lever 74.

[0044] When the accelerator pedal 71 is operated, the work machine 1 (traveling device 5) accelerates. When the brake pedal 72 is operated, the work machine 1 (traveling device 5) decelerates. When the steering wheel 73 is operated, the work machine 1 (traveling device 5) turns. When the forward / reverse switch lever 74 is operated, the work machine 1 (traveling device 5) switches between forward and reverse travel.

[0045] The work implement operating device 70B is operated by an operator to operate the work implement 6. The work implement operating device 70B generates an operation signal to operate the work implement 6. The work implement operating device 70B includes a boom lever 75 and a bucket lever 76. The boom lever 75 is operated to operate the boom 8. The bucket lever 76 is operated to operate the bucket 9.

[0046] When the boom lever 75 is operated, the boom spool of the work implement control valve 23 moves. When the boom lever 75 is operated to one side from the neutral position of the boom lever 75 and the boom spool is located in the bottom position, the boom cylinder 12 extends. When the boom lever 75 is operated to the other side from the neutral position of the boom lever 75 and the boom spool is located in the rod position, the boom cylinder 12 retracts. When the boom spool is located in the neutral position, the extension and contraction of the boom cylinder 12 stops.

[0047] When the bucket lever 76 is operated, the bucket spool of the work implement control valve 23 moves. When the bucket spool is located in the bottom position, the bucket cylinder 13 extends. When the bucket spool is located in the rod position, the bucket cylinder 13 retracts. When the bucket spool is located in the neutral position, the bucket cylinder 13 stops extending and retracting.

[0048] The input device 81 is operated by an operator. The input device 81 generates input data when operated by the operator. The input data generated by the input device 81 is transmitted to the in-vehicle controller 32 via the remote controller 82 and the communication system 203.

[0049] <In-vehicle controller> FIG. 3 is a hardware configuration diagram showing an in-vehicle controller 32 according to this embodiment. The in-vehicle controller 32 includes a computer 33. The computer 33 has a processor 34 such as a central processing unit (CPU), a main memory 35 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 36, an input / output interface 37 including an input / output circuit, and a communication interface 38 including a communication circuit. The functions of the in-vehicle controller 32 are stored in the storage 36 as a computer program 39. The processor 34 reads the computer program 39 from the storage 36, loads it into the main memory 35, and executes processing in accordance with the computer program 39. The computer program 39 may be distributed to the computer 33 via a network.

[0050] The remote controller 82 also includes a computer. Like the in-vehicle controller 32, the remote controller 82 has a processor, a main memory, storage, an input / output interface, and a communication interface.

[0051] <Control System> 4 is a block diagram showing a control system 100 for the work machine 1 according to this embodiment. The control system 100 includes a remote controller 82 and an on-vehicle controller 32. Detection data from the position sensor 24, direction sensor 25, speed sensor 26, steering sensor 27, work implement attitude sensor 28, external sensor 29, and load sensor 30 is transmitted to the on-vehicle controller 32. Operation commands from the operation device 70 are transmitted to the on-vehicle controller 32 via a communication system 203. Input data from the input device 81 is transmitted to the on-vehicle controller 32 via the communication system 203. The on-vehicle controller 32 transmits control commands to each of the traveling devices 5 and the work implement 6.

[0052] 4, the in-vehicle controller 32 includes an operation signal receiving unit 40, a constraint condition calculating unit 41, and a control command unit 42. Each of the operation signal receiving unit 40, the constraint condition calculating unit 41, and the control command unit 42 is realized by the computer 33 including the processor 34 described above.

[0053] The operation signal receiving unit 40 receives an operation signal from the operation device 70 that is operated to operate the work machine 1. The operation signal receiving unit 40 receives the operation signal from the operation device 70 via the communication system 203.

[0054] The constraint condition calculation unit 41 calculates the constraint conditions for maintaining the stability of the work machine 1. In this embodiment, the constraint conditions for maintaining the stability of the work machine 1 include a constraint condition that the load held in the bucket 9 of the work implement 6 does not collapse when the traveling device 5 travels. In this embodiment, the load held in the bucket 9 includes earth and sand. The load (earth and sand) held in the bucket 9 not collapsing means that the load does not spill from the bucket 9 or the load does not fall from the bucket 9.

[0055] The constraint condition calculation unit 41 acquires the detection data of the position sensor 24, the detection data of the direction sensor 25, the detection data of the speed sensor 26, the detection data of the steering sensor 27, the detection data of the work implement attitude sensor 28, the detection data of the external sensor 29, and the detection data of the load sensor 30. In addition, the constraint condition calculation unit 41 acquires input data from the input device 81 via the communication system 203.

[0056] The constraint condition calculation unit 41 calculates constraint conditions under which the load held in the bucket 9 of the work implement 6 does not collapse, based on at least the vehicle state parameters. In an embodiment, the constraint condition calculation unit 41 calculates constraint conditions under which the load held in the bucket 9 of the work implement 6 does not collapse, based on the vehicle state parameters and the load parameters. The constraint condition calculation unit 41 can acquire the vehicle state parameters and the load parameters by acquiring one or both of the detection data and the input data.

[0057] The vehicle state parameters indicate the operating state of the work machine 1. The vehicle state parameters include the position of the work machine 1, the attitude (inclination angle) of the work machine 1, the forward acceleration of the work machine 1, the lateral acceleration of the work machine 1, the position (height) of the work implement 6, the attitude (angle) of the work implement 6, the operating speed of the work implement 6, and the operating acceleration of the work implement 6. The constraint condition calculation unit 41 can obtain the position of the work machine 1 by acquiring detection data from the position sensor 24. If the orientation sensor 25 is an inertial sensor (IMU), the constraint condition calculation unit 41 can obtain the attitude and forward acceleration of the work machine 1 by acquiring detection data from the orientation sensor 25. The constraint condition calculation unit 41 can estimate the lateral acceleration of the work machine 1 based on the detection data from the speed sensor 26 and the detection data from the steering sensor 27. The constraint condition calculation unit 41 can calculate the position of the work implement 6, the attitude of the work implement 6, the operating speed of the work implement 6, and the operating acceleration of the work implement 6 based on detection data from the work implement orientation sensor 28.

[0058] The load parameters indicate the state of the load held in the bucket 9 of the work implement 6. The state of the load includes the mass of the load held in the bucket 9, the inertia tensor of the load, and the position of the center of gravity of the load. The constraint condition calculation unit 41 can acquire the mass of the load by acquiring detection data from the load sensor 30. The constraint condition calculation unit 41 can calculate the inertia tensor and the position of the center of gravity of the load based on the detection data from the external sensor 29. The external sensor 29 can detect the three-dimensional shape of the load held in the bucket 9. Assuming that the density of the load is constant, the constraint condition calculation unit 41 can calculate the inertia tensor and the position of the center of gravity of the load based on the three-dimensional shape of the load detected by the external sensor 29. Note that the load parameters may be input to the constraint condition calculation unit 41 from the input device 81.

[0059] The control command unit 42 outputs control commands for operating the work machine 1. The control command unit 42 outputs control commands for operating the work machine 1 so as to satisfy the constraint conditions calculated by the constraint condition calculation unit 41. The traveling device 5 and the work implement 6 each operate based on the control commands output from the control command unit 42.

[0060] <Restrictions> 5 and 6 are diagrams illustrating constraint conditions under which a load held in the bucket 9 of the work implement 6 according to this embodiment does not collapse. The constraint condition calculation unit 41 calculates constraint conditions under which a load held in the bucket 9 of the work implement 6 does not collapse when the work machine 1 travels.

[0061] In this embodiment, the cargo parameters for calculating the constraint conditions include soil parameters that indicate the properties of the soil that is the cargo. The constraint condition calculation unit 41 calculates the constraint conditions based on the inertial force acting on the cargo held in the bucket 9, the shape of the cargo held in the bucket 9, and the soil parameters that indicate the properties of the cargo held in the bucket 9. In this embodiment, the constraint condition calculation unit 41 calculates the constraint conditions that prevent the cargo held in the bucket 9 from collapsing, based on Mohr's failure criterion.

[0062] As shown in Figure 5, when the work machine 1 accelerates or decelerates while it is traveling, an inertial force Fa acts in the front-to-rear direction on the load held in the bucket 9. When the work machine 1 turns while it is traveling, an inertial force Fb (centrifugal force) acts in the left-to-right direction on the load held in the bucket 9. The inertial force F acting on the load held in the bucket 9 is the resultant force of the inertial forces Fa and Fb.

[0063] In this embodiment, the soil parameter is the cohesion of the soil c [N / m 2 ], the internal friction angle of the soil φ [°], and the density of the soil ρ [kg / m 3 The soil parameters may be input from the input device 81.

[0064] The constraint condition calculation unit 41 may calculate the density ρ of the soil and sand based on the three-dimensional shape (volume) of the soil and sand held in the bucket 9 and the weight of the soil and sand held in the bucket 9. The external sensor 29 is capable of detecting the three-dimensional shape (volume) of the soil and sand held in the bucket 9. The load sensor 30 is capable of detecting the weight of the soil and sand held in the bucket 9.

[0065] As shown in Figure 6, in Mohr's failure criterion, a slide surface is set in the soil held by the bucket 9. The angle θ between the slide surface and the minimum principal stress (horizontal plane) is set arbitrarily. The inertial force F is calculated by the angle θ, the travel speed v [m / sec] of the work machine 1, and the acceleration a [m / sec] of the work machine 1. 2 ] and steering angle δ [rad]. Inertial force F [θ,v,a,δ] is the inertial force acting on the soil above the slide surface.

[0066] The shape of the load held in bucket 9 includes the angle θmax formed by the opening of bucket 9 and a tangent to the surface of the soil and sand located outside the opening of bucket 9, which passes through the point of contact with the opening of bucket 9 and the opening of bucket 9. The angle θmax is detected by external sensor 29.

[0067] The gravity W acting on the soil above the slide surface is a function of the angle θ. The constraint condition calculation unit 41 can calculate the gravity W(θ) based on the three-dimensional shape of the soil (volume of the soil above the slide surface) detected by the external sensor 29 and the density ρ of the soil.

[0068] The area A of the slide surface is a function of the angle θ. The constraint condition calculation unit 41 can calculate the area A(θ) based on the three-dimensional shape of the earth and sand detected by the external sensor 29.

[0069] Normal stress σ and shear stress τ act on the slip surface. The normal stress σ acting on the slip surface is expressed by the balance equation shown in Equation (1) below.

[0070]

number

[0071] In this embodiment, the constraint condition for preventing the load held by the bucket 9 from collapsing is the condition that no slide of earth and sand occurs on the slide surface. The condition that no slide of earth and sand occurs on the slide surface is expressed by the following equation (2).

[0072]

number

[0073] The control command unit 42 calculates a control command in the range of [0<θ<θmax] so as to satisfy the condition of the above-mentioned equation (2).

[0074] The constraint condition calculation unit 41 may calculate the constraint conditions that will prevent the load held in the bucket 9 from collapsing, taking into account the topography of the work site 201. In other words, the constraint condition calculation unit 41 may determine the constraint conditions, taking into account the inclination angle of the ground at the work site 201. If the ground at the work site 201 includes a slope, there is a possibility that the load held in the bucket 9 will easily collapse when the work machine 1 travels on the slope. Therefore, the constraint condition calculation unit 41 may determine the constraint conditions, taking into account the inclination angle of the ground at the work site 201.

[0075] <Intervention control> 7 is a diagram illustrating the processing of the on-board controller 32 according to this embodiment. The control command unit 42 modifies the operation signal from the operation device 70 based on the constraint conditions. In this embodiment, the control command unit 42 performs intervention control of the work machine 1. Modifying the operation signal includes performing intervention control.

[0076] Intervention control refers to controlling the work machine 1 so that it operates under predetermined specified operating conditions when the operation device 70 is being operated and the work machine 1 does not operate under predetermined specified operating conditions. In this embodiment, the specified operating conditions are operating conditions that satisfy the constraint condition that prevents the load from collapsing. In other words, in this embodiment, intervention control refers to the control command unit 42 outputting a control command so that the work machine 1 satisfies the constraint condition, regardless of the operation signal from the operation device 70, when the operation signal receiving unit 40 is receiving an operation signal from the operation device 70 and the work machine 1 does not satisfy the constraint condition.

[0077] The control command unit 42 does not perform intervention control if it determines that the work machine 1 satisfies the constraint conditions while the work machine 1 is operating based on an operation signal from the operation device 70. In other words, if the control command unit 42 determines that the work machine 1 satisfies the constraint conditions while the operation signal receiving unit 40 is receiving an operation signal from the operation device 70, it outputs a control command to operate the work machine 1 based on the operation signal from the operation device 70.

[0078] The control command unit 42 performs intervention control when it is determined that the work machine 1 does not satisfy the constraint conditions while the work machine 1 is operating based on an operation signal from the operation device 70. In other words, when the control command unit 42 determines that the work machine 1 does not satisfy the constraint conditions while the operation signal receiving unit 40 is receiving an operation signal from the operation device 70, it outputs a control command to operate the work machine 1 so that the work machine 1 satisfies the constraint conditions, regardless of the operation signal from the operation device 70.

[0079] In the following description, when it is determined that the work machine 1 satisfies the constraint conditions while an operation signal is being received from the operation device 70, the control command output from the control command unit 42 based on the operation signal from the operation device 70 will be referred to as a manual operation command, as appropriate. When it is determined that the work machine 1 does not satisfy the constraint conditions while an operation signal is being received from the operation device 70, the control command output from the control command unit 42 regardless of the operation signal from the operation device 70 will be referred to as an intervention control command, as appropriate.

[0080] When the traveling system operation device 70A is operated suddenly, the state of the work machine 1 changes suddenly. The state of the work machine 1 includes the traveling state of the work machine 1 (traveling device 5). A sudden change in traveling state includes at least one of sudden acceleration, sudden deceleration, and sudden turning of the work machine 1. When the accelerator pedal 71 is operated suddenly, the work machine 1 accelerates suddenly. When the brake pedal 72 is operated suddenly, the work machine 1 decelerates suddenly. When the steering wheel 73 is operated suddenly, the work machine 1 makes a sudden turn. If the traveling system operation device 70A is operated suddenly while a load is held in the bucket 9, and the state of the work machine 1 changes suddenly, there is a high possibility that the work machine 1 will not satisfy the constraint conditions. If the traveling system operation device 70A is operated so that the work machine 1 suddenly accelerates, decelerates, or turns suddenly, there is a high possibility that the load held in the bucket 9 will collapse.

[0081] In this embodiment, when the control command unit 42 determines that the work machine 1 does not satisfy the constraint conditions while a load is held in the bucket 9 and the operation signal receiving unit 40 is receiving an operation signal from the operation device 70, it intervenes and controls the traveling device 5 so that the work machine 1 satisfies the constraint conditions. When at least one of the traveling system operation device 70A and the work implement operation device 70B is operated in a way that would cause the load held in the bucket 9 to collapse, the control command unit 42 outputs an intervention control command to the traveling device 5 so that the load does not collapse. In this embodiment, the control command unit 42 outputs an intervention control command so that the condition of the above-mentioned equation (2) is satisfied within the range of [0<θ<θmax].

[0082] The value of the operation signal from traveling system operation device 70A changes based on the operation amount of traveling system operation device 70A. Control command unit 42 calculates a manual operation command value indicating the value of the manual operation command based on the operation signal value indicating the value of the operation signal from traveling system operation device 70A. There is a one-to-one correspondence between the operation signal value and the manual operation command value. The greater the operation amount of traveling system operation device 70A and the greater the operation signal value, the greater the manual operation command value. The more abruptly traveling system operation device 70A is operated and the greater the rate of change in the operation signal value, the greater the rate of change in the manual operation command value.

[0083] The greater the operation signal value from the accelerator pedal 71, the greater the manual operation command value for accelerating the work machine 1, and the higher the traveling speed of the work machine 1. The more abruptly the accelerator pedal 71 is operated and the greater the rate of change in the operation signal value from the accelerator pedal 71, the greater the rate of change in the manual operation command value for accelerating the work machine 1, and the more rapidly the work machine 1 accelerates.

[0084] The greater the operation signal value from the brake pedal 72, the greater the manual operation command value for decelerating the work machine 1, and the lower the traveling speed of the work machine 1. The more abruptly the brake pedal 72 is operated and the greater the rate of change in the operation signal value from the brake pedal 72, the greater the rate of change in the manual operation command value for decelerating the work machine 1, and the more rapidly the work machine 1 decelerates.

[0085] The greater the operation signal value from the steering wheel 73, the greater the manual operation command value for turning the work machine 1, and the smaller the turning radius of the work machine 1. The greater the rate of change of the operation signal value from the steering wheel 73, the greater the rate of change of the manual operation command value for turning the work machine 1, and the sharper the turn of the work machine 1.

[0086] When the control command unit 42 determines that the work machine 1 does not satisfy the constraint conditions, it outputs an intervention control command that has a value closest to the value of the manual control command calculated based on the operation signal value within the range of control command values ​​that satisfy the constraint conditions. In other words, when the control command unit 42 determines that the work machine 1 does not satisfy the constraint conditions, it outputs an intervention control command such that the difference between the manual control command value indicating the value of the manual control command and the intervention control command value that is the value of the intervention control command is smallest within the range of control command values ​​that satisfy the constraint conditions. The control command unit 42 outputs an intervention control command such that the intervention control command value becomes the highest control command value within the range of control command values ​​that satisfy the constraint conditions.

[0087] For example, if it is determined that the accelerator pedal 71 will be suddenly operated and the load held in the bucket 9 will collapse, the control command unit 42 outputs an intervention control command to mitigate the sudden acceleration of the work machine 1, regardless of the operation signal from the accelerator pedal 71. The control command unit 42 outputs an intervention control command to the traveling device 5 so that the work machine 1 accelerates at an acceleration that is smaller than the acceleration calculated based on the operation signal from the accelerator pedal 71 and is the largest within the range of acceleration that satisfies the constraint conditions. On the other hand, if it is determined that the load held in the bucket 9 will not collapse when the work machine 1 accelerates at the acceleration calculated based on the operation signal from the accelerator pedal 71, the control command unit 42 outputs a manual control command to accelerate the work machine 1, based on the operation signal from the accelerator pedal 71.

[0088] For example, if it is determined that the brake pedal 72 will be suddenly operated and the load held in the bucket 9 will collapse, the control command unit 42 outputs an intervention control command to mitigate the sudden deceleration of the work machine 1, regardless of the operation signal from the brake pedal 72. The control command unit 42 outputs an intervention control command to the traveling device 5 so that the work machine 1 decelerates at a deceleration that is smaller than the deceleration calculated based on the operation signal from the brake pedal 72 and is the largest within the range of deceleration that satisfies the constraint conditions. On the other hand, if it is determined that the load held in the bucket 9 will not collapse when the work machine 1 decelerates at the deceleration calculated based on the operation signal from the brake pedal 72, the control command unit 42 outputs a manual control command to decelerate the work machine 1, based on the operation signal from the brake pedal 72.

[0089] For example, if it is determined that the steering wheel 73 will be suddenly operated and the load held in the bucket 9 will collapse, the control command unit 42 outputs an intervention control command to mitigate the sudden turn of the work machine 1, regardless of the operation signal from the steering wheel 73. The control command unit 42 outputs an intervention control command to the traveling device 5 so that the work machine 1 turns at a rate of change of turning radius that is smaller than the rate of change of turning radius calculated based on the operation signal from the steering wheel 73 and is the largest within the range of rates of change of turning radius that satisfy the constraint conditions. On the other hand, if it is determined that the load held in the bucket 9 will not collapse when the work machine 1 turns at the rate of change of turning radius calculated based on the operation signal from the steering wheel 73, the control command unit 42 outputs a manual control command to turn the work machine 1, based on the operation signal from the steering wheel 73.

[0090] For example, if it is determined that the work machine operating device 70B will be suddenly operated and the load held in the bucket 9 will collapse, the control command unit 42 outputs an intervention control command to the traveling device 5 so that the work machine 1 satisfies the constraint conditions, regardless of the operation signal from the traveling system operating device 70A. The control command unit 42 outputs an intervention control command to the traveling device 5 so that, within a range of control command values ​​that satisfy the constraint conditions, the difference between the manual control command value calculated based on the operation signal from the traveling system operating device 70A and the intervention control command value for intervening and controlling the traveling device 5 is minimized. On the other hand, if it is determined that the load held in the bucket 9 will not collapse when the work machine 1 operates under operating conditions calculated based on the operation signals from the traveling system operating device 70A and the work machine operating device 70B, the control command unit 42 outputs a manual control command to operate the work machine 1 based on the operation signals from the traveling system operating device 70A and the work machine operating device 70B.

[0091] If the control command unit 42 determines that the work machine 1 does not satisfy the constraint conditions, it may intervene and control the work machine 6 so that the constraint conditions are satisfied. For example, if it determines that the work machine operating device 70B has been suddenly operated and that the load held in the bucket 9 will collapse, the control command unit 42 outputs an intervention control command to the work machine 6 so that the work machine 6 operates at an operating acceleration that is smaller than the operating acceleration of the work machine 6 calculated based on the operation signal from the work machine operating device 70B and is the largest within the range of operating accelerations of the work machine 6 that satisfy the constraint conditions. Even if the traveling device 5 suddenly accelerates, decelerates, or turns, the position or attitude of the work machine 6 is adjusted by the intervention control command, thereby preventing the load held in the bucket 9 from collapsing.

[0092] In other words, if the control command unit 42 determines that the work machine 1 does not satisfy the constraint conditions, it may intervene and control only the traveling device 5, or only the work implement 6, or it may intervene and control both the traveling device 5 and the work implement 6 so that the constraint conditions are satisfied.

[0093] When an intervention control command is output, the operator may be notified that an intervention control command has been output. For example, a notification device such as a light emitting device and an audio output device may be disposed in the remote operation room 202. When an intervention control command is output from the control command unit 42, the notification device may output light or sound based on the intervention control command output from the control command unit 42 to notify the operator that an intervention control command has been output. The operator can recognize that the work machine 1 is being subjected to intervention control based on the notification data from the notification device.

[0094] <What to do if an obstacle is detected> FIG. 8 is a diagram illustrating the operation of the work machine 1 according to this embodiment. The work machine 1 is equipped with an external sensor 29. The external sensor 29 detects obstacles around the work machine 1. The external sensor 29 is disposed, for example, on the rear frame 2R. The external sensor 29 detects obstacles in the direction of travel of the work machine 1. In the example shown in FIG. 8, the external sensor 29 detects obstacles ahead of the work machine 1 moving forward. Note that when the work machine 1 moves backward, the work machine 1 may be provided with an external sensor 29 that detects obstacles behind the work machine 1.

[0095] If the control command unit 42 determines, based on the detection data of the external sensor 29, that there is a possibility that the work machine 1 will come into contact with an obstacle, it outputs a manual control command based on an operation signal from the operation device 70. If the control command unit 42 determines that the work machine 1 does not satisfy the constraint conditions but there is a possibility that the work machine 1 will come into contact with an obstacle, it outputs a manual control command based on an operation signal from the operation device 70 without outputting an intervention control command.

[0096] If the operator suddenly operates the brake pedal 72 to prevent the work machine 1 from coming into contact with an obstacle, an intervention control command to satisfy the constraint conditions is output, and if the sudden deceleration of the traveling gear 5 is alleviated, there is a possibility that the work machine 1 will come into contact with the obstacle. If the operator suddenly operates the steering wheel 73 to prevent the work machine 1 from coming into contact with the obstacle, an intervention control command to satisfy the constraint conditions is output, and if the sudden turning of the traveling gear 5 is alleviated, there is a possibility that the work machine 1 will come into contact with the obstacle. If the control command unit 42 determines, based on the detection data of the external sensor 29, that there is a possibility that the work machine 1 will come into contact with an obstacle, it does not output an intervention control command, but outputs a manual control command based on an operation signal from the operation device 70. By outputting a manual control command based on an operation signal from the operation device 70, contact between the work machine 1 and the obstacle is avoided.

[0097] The work machine 1 may also have a collision prevention function that prevents contact with an obstacle. When the control command unit 42 determines, based on detection data from the external sensor 29, that there is a possibility that the work machine 1 will come into contact with an obstacle, the control command unit 42 may control the traveling gear 5 to avoid contact between the work machine 1 and the obstacle, i.e., to activate the collision prevention function. The control command unit 42 may decelerate the traveling gear 5, stop the traveling of the traveling gear 5, or turn the traveling gear 5, to avoid contact between the work machine 1 and the obstacle. If the work machine 1 has a load shift prevention function that prevents loads from shifting and a collision prevention function that prevents contact between the work machine 1 and an obstacle, the load shift prevention function may be turned off so that the collision prevention function and the load shift prevention function do not interfere with each other. If the work machine 1 has both the load shift prevention function and the collision prevention function, the collision prevention function may take priority. If the work machine 1 has the load shift prevention function but not the collision prevention function, the control command unit 42 may output a manual control command based on an operation signal to activate the load shift prevention function.

[0098] <Control method> 9 is a flowchart showing a method for controlling the work machine 1 according to this embodiment. The operation signal receiving unit 40 receives, via the communication system 203, an operation signal from the operation device 70 that has been operated to operate the work machine 1 (step SA1).

[0099] The constraint condition calculation unit 41 determines whether or not a load is held in the bucket 9 based on the detection data of the load sensor 30 (step SA2).

[0100] If it is determined in step SA2 that a load is held in the bucket 9 (step SA2: Yes), the constraint condition calculation unit 41 calculates constraint conditions that will prevent the load held in the bucket 9 from collapsing, based on vehicle state parameters that indicate the operating state of the work machine 1 and load parameters that indicate the properties of the load held in the bucket 9 (step SA3).

[0101] The control command section 42 determines whether or not the work machine 1 satisfies the constraint conditions calculated in step SA3 (step SA4).

[0102] If it is determined in step SA4 that the work machine 1 does not satisfy the constraint conditions (step SA4: No), the control command unit 42 determines whether or not an obstacle exists in the direction of travel of the work machine 1 based on the detection data of the external sensor 29 (step SA5).

[0103] If it is determined in step SA5 that there is no obstacle in the direction of travel of the work machine 1 (step SA5: No), the control command unit 42 outputs an intervention control command so that the work machine 1 satisfies the constraint conditions, regardless of the operation signal received in step SA1 (step SA6).

[0104] In step SA2, if it is determined that no load is held in the bucket 9 (step SA2: No), the control command unit 42 outputs a manual control command based on the operation signal received in step SA1 (step SA7).

[0105] If it is determined in step SA4 that the work machine 1 satisfies the constraint conditions (step SA4: Yes), the control command unit 42 outputs a manual control command based on the operation signal received in step SA1 (step SA7).

[0106] In step SA5, if it is determined that an obstacle exists in the direction of travel of the work machine 1 and that there is a possibility that the work machine 1 may come into contact with the obstacle (step SA5: Yes), the control command unit 42 outputs a manual control command based on the operation signal received in step SA1 (step SA7).

[0107] <Effects> As described above, according to this embodiment, constraint conditions that prevent the load held by the work implement 6 from collapsing are calculated based on vehicle state parameters that indicate the operating state of the work machine 1 and load parameters that indicate the properties of the load held by the work implement 6. If the work machine 1 operates based on an operation signal from the operation device 70 and the work machine 1 does not satisfy the constraint conditions, intervention control is implemented so that the constraint conditions are satisfied. If the operation device 70 is suddenly operated by the operator, the state of the work machine 1 may change suddenly, causing the load held by the work implement 6 to collapse. According to this embodiment, even if the operation device 70 is suddenly operated by the operator, intervention control is implemented, thereby preventing the load held by the work implement 6 from collapsing.

[0108] In this embodiment, the constraint condition for preventing the load held by the work machine 6 from collapsing is the adhesion force c [N / m 2 ], the internal friction angle of the soil φ [°], and the density of the soil ρ [kg / m 3 As a result, when the load held by the work implement 6 is earth and sand, the constraint conditions that prevent the earth and sand held by the work implement 6 from collapsing are calculated appropriately.

[0109] In this embodiment, the control command unit 42 outputs an intervention control command so as to reduce the difference between the manual control command value and the intervention control command value within a range that satisfies the constraint conditions. By outputting an intervention control command so as to reduce the difference between the manual control command value and the intervention control command value, the operation of the work machine 1 is prevented from becoming excessively slow. Because the operation of the work machine 1 is prevented from becoming excessively slow, a decrease in the work efficiency of the work machine 1 is prevented.

[0110] In this embodiment, when the control command unit 42 determines based on the detection data of the external sensor 29 that there is a possibility that the work machine 1 will come into contact with an obstacle, it does not output an intervention control command, but outputs a manual control command based on an operation signal from the operation device 70. When the operator operates the operation device 70 to avoid contact between the work machine 1 and the obstacle, a manual control command is output based on the operation signal from the operation device 70, and contact between the work machine 1 and the obstacle is avoided.

[0111] In this embodiment, the work machine 1 is remotely operated. When the work machine 1 is remotely operated, the operator in the remote control room 202 is unlikely to feel a sudden change in the state of the work machine 1 even if the operation device 70 is suddenly operated. The operator in the remote control room 202 is unlikely to feel a sudden acceleration, deceleration, or sharp turn of the work machine 1 even if the traveling system operation device 70A is suddenly operated. The operator in the remote control room 202 is unlikely to feel a sudden movement of the work machine 6 even if the work implement operation device 70B is suddenly operated. For this reason, the operator in the remote control room 202 may unintentionally operate the operation device 70 suddenly. If the operation device 70 is suddenly operated and the state of the work machine 1 changes suddenly, there is a high possibility that the load held in the bucket 9 will collapse. According to this embodiment, when the operation device 70 is suddenly operated, an intervention control command is output so that the state of the work machine 1 does not change suddenly, that is, so that the work machine 1 satisfies the constraint conditions. Therefore, the load held in the bucket 9 is prevented from collapsing.

[0112] [Second embodiment] A second embodiment will be described below. In the following description, the same or equivalent components as those in the above-described embodiment will be denoted by the same reference numerals, and the description of those components will be simplified or omitted.

[0113] In the first embodiment described above, the constraint conditions are calculated based on the vehicle state parameters and the load parameters that indicate the properties of the load. In this embodiment, an example will be described in which the vehicle state parameters include the acceleration of the work machine 1, the load parameters include the presence or absence of a load in the bucket 9, and the constraint conditions are such that the acceleration of the load held in the bucket 9 is less than a threshold value.

[0114] When the work machine 1 (traveling device 5) travels with a load held in the bucket 9, the load accelerates. If the acceleration of the load is large, there is a high possibility that the load will collapse. The acceleration of the load includes positive acceleration and deceleration, which is negative acceleration.

[0115] The acceleration of the work machine 1 and the acceleration of the load can be considered to be substantially the same. By calculating the acceleration of the work machine 1, the acceleration of the load held in the bucket 9 can be calculated.

[0116] In this embodiment, when the control command unit 42 determines that the acceleration of the load is less than a predetermined threshold, it determines that the work machine 1 satisfies the constraint conditions and outputs a manual control command. When the control command unit 42 determines that the acceleration of the load is equal to or greater than the threshold, it determines that the work machine 1 does not satisfy the constraint conditions and outputs an intervention control command so that the acceleration of the load becomes less than the threshold.

[0117] The constraint condition calculation unit 41 can calculate the acceleration of the load in the traveling direction of the work machine 1 (forward acceleration) based on the detection data of the speed sensor 26. The constraint condition calculation unit 41 can calculate the forward acceleration of the load by differentially processing the detection data of the speed sensor 26. The constraint condition calculation unit 41 can calculate the acceleration of the load in the turning direction of the work machine 1 (lateral acceleration) based on the detection data of the speed sensor 26 and the detection data of the steering sensor 27. The constraint condition calculation unit 41 can calculate the turning radius of the work machine 1 based on the detection data of the steering sensor 27. The constraint condition calculation unit 41 can calculate the lateral acceleration of the load based on the detection data of the speed sensor 26 and the turning radius of the work machine 1.

[0118] If an acceleration sensor is provided on the vehicle body 2 or the bucket 9, the constraint condition calculation unit 41 may obtain the acceleration of the load by acquiring detection data from the acceleration sensor.

[0119] The constraint condition calculation unit 41 can calculate the positive acceleration of the load based on the rotation speed of the drive machine 16. If the drive machine 16 is an engine, the rotation speed of the drive machine 16 is the engine rotation speed, and if the drive machine 16 is a motor, the rotation speed of the drive machine 16 is the motor rotation speed. The constraint condition calculation unit 41 calculates the tire torque, which indicates the torque of the wheels 4 to which power is transmitted from the power transmission device 18, based on the rotation speed of the drive machine 16. The constraint condition calculation unit 41 can calculate the acceleration of the work machine 1 and the acceleration of the load based on the tire torque.

[0120] The constraint condition calculation unit 41 can calculate the negative acceleration (deceleration) of the load based on the brake pressure, which is the pressure of the brake device 19. The constraint condition calculation unit 41 calculates the tire torque, which indicates the torque of the wheels 4 to which power is transmitted from the power transmission device 18, based on the brake pressure. The constraint condition calculation unit 41 can calculate the deceleration of the work machine 1 and the deceleration of the load based on the tire torque.

[0121] The intervention control command to reduce the positive acceleration of the load below a threshold value includes one or both of decreasing the value of the accelerator command to accelerate the work machine 1 and increasing the value of the brake command to decelerate the work machine 1.

[0122] The intervention control command to reduce the negative acceleration (deceleration) of the load below a threshold value includes one or both of reducing the value of the brake command to decelerate the work machine 1 and increasing the value of the accelerator command to accelerate the work machine 1.

[0123] 10 is a flowchart showing a method for controlling the work machine 1 according to this embodiment. The operation signal receiving unit 40 receives, via the communication system 203, an operation signal from the operation device 70 that has been operated to operate the work machine 1 (step SB1).

[0124] The constraint condition calculation unit 41 determines whether or not a load is held in the bucket 9 based on the detection data of the load sensor 30 (step SB2).

[0125] If it is determined in step SB2 that a load is held in bucket 9 (step SB2: Yes), constraint condition calculation unit 41 calculates the acceleration of the load held in bucket 9 while work machine 1 is traveling, for example, based on the detection data of speed sensor 26 and the detection data of steering sensor 27. Control command unit 42 determines whether the acceleration of the load calculated by constraint condition calculation unit 41 is equal to or greater than a predetermined threshold value (step SB3).

[0126] If it is determined in step SB3 that the acceleration of the cargo is greater than or equal to the threshold value (step SB3: Yes), the control command unit 42 outputs an intervention control command to the traveling device 5 so that the acceleration of the cargo becomes less than the threshold value, regardless of the operation signal received in step SB1 (step SB4).

[0127] In step SB2, if it is determined that no load is held in the bucket 9 (step SB2: No), the control command unit 42 outputs a manual control command based on the operation signal received in step SB1 (step SB5).

[0128] If it is determined in step SB3 that the acceleration of the cargo is less than the threshold value (step SB3: No), the control command unit 42 outputs a manual control command based on the operation signal received in step SB1 (step SB5).

[0129] As described above, according to this embodiment, even if the operator suddenly operates the traveling system operation device 70A and the acceleration of the load increases, intervention control is implemented to prevent the load held by the work implement 6 from collapsing.

[0130] In this embodiment, the control command unit 42 may output an intervention control command when it is determined that either one of the constraint condition (first constraint condition) described in the above-mentioned first embodiment or the constraint condition (second constraint condition) described in the above-mentioned second embodiment is not satisfied. The control command unit 42 may output an intervention control command when it is determined that both of the constraint condition (first constraint condition) described in the above-mentioned first embodiment or the constraint condition (second constraint condition) described in the above-mentioned second embodiment are not satisfied.

[0131] [Third embodiment] A third embodiment will be described below. In the following description, the same or equivalent components as those in the above-described embodiment will be denoted by the same reference numerals, and the description of those components will be simplified or omitted.

[0132] In the first and second embodiments described above, the work machine 1 is a wheel loader. The work machine 1 may be any work machine that has a work implement that holds a load. The work machine may also be, for example, a forklift.

[0133] 11 is a schematic diagram of a work machine 301 according to this embodiment, seen from above. The work machine 301 is a forklift. The work machine 301 has a vehicle body 302 and a work implement 306 arranged at the front of the vehicle body 302.

[0134] The work implement 306 has a mast 307, a bracket 308, and a fork 309. The mast 307 is supported at the front of the vehicle body 302 so as to be able to tilt. The mast 307 is long in the vertical direction. The bracket 308 supports the fork 309. The bracket 308 is supported by the mast 307. The bracket 308 is able to move in the vertical direction along the mast 307. The fork 309 supports a load 400. The fork 309 has a support surface (upper surface) that supports the load 400. The load 400 is placed on the support surface of the fork 309.

[0135] The forks 309 are supported on the mast 307 via brackets 308. A pair of forks 309 are provided. The forks 309 include a first fork 309L and a second fork 309R located to the right of the first fork 309L. The brackets 308 support the first fork 309L and the second fork 309R.

[0136] The constraint condition calculation unit 41 calculates constraint conditions under which the load 400 supported by the forks 309 does not collapse when the work machine 301 travels. The load 400 supported by the forks 309 includes a container. The load 400 (container) supported by the forks 309 not collapsing means that the load 400 does not fall from the forks 309.

[0137] The constraint condition calculation unit 41 calculates constraint conditions based on the load parameters to prevent the load 400 supported by the forks 309 from collapsing. The constraint conditions include a condition that the zero moment point Z0 of the load 400 does not deviate from a set range AP that is set based on the shape of the forks 309. The zero moment point (ZMP) refers to the dynamic center of gravity position of the work machine 1 that takes into account the influence of inertial force (centrifugal force). The zero moment point Z0 is the point where the resultant force of gravity and inertial force intersects with the ground.

[0138] The setting range AP corresponds to the support polygon of the load 400 placed on the forks 309. The setting range AP is a rectangular range connecting the front end of the left end of the support surface of the first fork 309L, the rear end of the left end of the support surface of the first fork 309L, the front end of the right end of the support surface of the second fork 309R, and the rear end of the right end of the support surface of the second fork 309R.

[0139] The constraint condition calculation unit 41 calculates the zero moment point Z0 based on the load parameters related to the load 400 supported by the forks 309. The load parameters for calculating the zero moment point Z0 include the mass of the load 400 supported by the forks 309, the inertia tensor of the load 400, and the center of gravity position of the load 400.

[0140] The work machine 301 has a load sensor that detects the weight of the load 400 and an external sensor that detects the three-dimensional shape of the load 400. The constraint condition calculation unit 41 can obtain the mass of the load 400 by acquiring detection data from the load sensor. The constraint condition calculation unit 41 can calculate the inertia tensor and center of gravity position of the load 400 based on the detection data from the external sensor. Assuming that the density of the load 400 is constant, the constraint condition calculation unit 41 can calculate the inertia tensor and center of gravity position of the load 400 based on the three-dimensional shape of the load detected by the external sensor.

[0141] 12 is a schematic diagram of work machine 301 according to this embodiment, viewed from above. Forks 309 may support load 400 via a pallet 410. That is, there are cases in which work machine 301 travels with pallet 410 placed on the support surface of fork 309 and load 400 placed on pallet 410. When forks 309 support load 400 via pallet 410, the constraint conditions include a condition that the zero moment point of load 400 placed on the pallet does not deviate from set range AP.

[0142] When the forks 309 hold the load 400 via a pallet 410, the constraints may include a condition that the load 400 does not slip on the pallet 410. That is, the constraints may include a condition that the slide surface component SL of the force acting on the load 400 does not become larger than the static friction force. This constraint is calculated as a condition that the slide surface component SL of the force acting on the load 400 on the pallet surface becomes smaller than the static friction force between the load 400 and the pallet 410. This constraint is calculated as a condition that the inertial force does not go outside the friction circle CL shown in FIG. 12. The static friction force is calculated from the static friction coefficient μ and the normal force N acting on the load 400. The normal force N is calculated from the angle of the work implement 306 and the mass of the load 400. The static friction coefficient μ may be input to the constraint calculation unit 41 from the input device 81. The constraint calculation unit 41 can calculate the constraints based on the mass and static friction coefficient of the load 400.

[0143] If the control command unit 42 determines that the constraint conditions are not satisfied while an operation signal for operating the work machine 301 is being received, it outputs an intervention control command so that the constraint conditions are satisfied, regardless of the operation signal. The control command unit 42 may output an intervention control command to the traveling device of the work machine 301, or may output an intervention control command to the work implement 306.

[0144] As described above, in this embodiment as well, the load supported by the forks 309 is prevented from falling by performing intervention control.

[0145] In this embodiment, the constraint condition calculation unit 41 may acquire the acceleration of the load supported by the fork 309, as in the second embodiment described above. The control command unit 42 may output an intervention control command when it is determined that either one of the constraint conditions (second constraint condition) described in the second embodiment described above or the constraint condition (third constraint condition) described in the third embodiment is not satisfied. The control command unit 42 may output an intervention control command when it is determined that both the constraint conditions (second constraint condition) described in the second embodiment described above or the constraint condition (third constraint condition) described in the third embodiment are not satisfied.

[0146] [Other embodiments] In the first and second embodiments described above, the articulate cylinder 7, the boom cylinder 12, and the bucket cylinder 13 are each a hydraulic cylinder. However, at least one of the articulate cylinder 7, the boom cylinder 12, and the bucket cylinder 13 may be an electrically operated cylinder.

[0147] Based on the above-described embodiment, the constraint condition calculation unit 41 calculates constraint conditions that prevent the load held in the bucket 9 of the work machine 6 from collapsing, based on the vehicle state parameters and the load parameters. The constraint condition calculation unit 41 may calculate constraint conditions based on the vehicle state parameters without considering the load parameters. The processor 34 may determine that the load will collapse when the acceleration of the work machine 1 exceeds a predetermined threshold, without considering the properties of the load, and may perform intervention control.

[0148] In the above-described embodiment, the control instruction unit 42 modifies the operation signal from the operation device 70 based on the constraint conditions. Modifying the operation signal includes performing intervention control. Intervention control refers to the control instruction unit 42 outputting a control command regardless of the operation signal from the operation device 70 while the operation signal receiving unit 40 is receiving the operation signal from the operation device 70. Intervention control may be a concept of restricting or modifying all of the operation signal from the operation device 70, or a concept of restricting or modifying part of the operation signal. In other words, in intervention control, at least part of the operation signal may be reflected in the intervention control command output from the control instruction unit 42.

[0149] In the above-described embodiment, at least some of the functions of the in-vehicle controller 32 may be provided in the remote controller 82. At least one of the constraint condition calculation unit 41 and the control command unit 42 may be provided in the remote controller 82.

[0150] In the above-described embodiment, the work machine 1 is remotely controlled. An operator sitting in the cab of the work machine 1 may operate the work machine 1. The operating device 70 may be arranged in the cab of the work machine 1.

[0151] [Note] The present disclosure may also have the following configurations. (Appendix 1) a processor; The processor: receiving an operation signal from an operation device operated to operate a work machine having a work implement and a traveling device; calculating constraint conditions for preventing a load held by the work machine from collapsing based on vehicle state parameters that indicate an operating state of the work machine; modifying the operation signal based on the constraint; Work machine control systems. (Appendix 2) the processor calculates the constraint conditions based on the vehicle state parameters and load parameters indicating properties of a load held by the work machine. 10. A control system for a work machine as described in claim 1. (Appendix 3) The processor: When it is determined that the constraint condition is not satisfied while the operation signal is received, an intervention control command is output so that the constraint condition is satisfied. 10. A control system for a work machine according to claim 1 or 2. (Appendix 4) The processor: calculating the constraint conditions based on an inertial force acting on the cargo, a shape of the cargo, and cargo parameters; 10. A control system for a work machine as described in appended claim 2. (Appendix 5) the cargo includes earth and sand; The load parameters include the adhesion of the soil, the angle of internal friction of the soil, and the density of the soil. 10. A control system for a work machine as described in appended claim 2. (Appendix 6) The processor: calculating the constraints based on load parameters including a mass of the load, an inertia tensor of the load, and a center of gravity location of the load; the constraint condition includes a condition that the zero moment point of the load does not deviate from a set range that is set based on the shape of the work machine. 6. A control system for a work machine according to any one of Supplementary Note 1 to Supplementary Note 5. (Appendix 7) The processor: Calculating the constraints based on the mass and static friction coefficient of the load; The constraint conditions include a condition that the component of the force acting on the load on the sliding surface does not exceed the static friction force. 7. A control system for a work machine according to any one of Supplementary Note 1 to Supplementary Note 6. (Appendix 8) The processor: Calculating the acceleration of the load while the work machine is traveling; The constraint condition includes a condition that the acceleration is less than a predetermined threshold. 8. A control system for a work machine according to any one of Supplementary Note 1 to Supplementary Note 7. (Appendix 9) The processor: If it is determined that the constraint condition is satisfied, a manual control command is output based on the operation signal; When it is determined that the constraint condition is not satisfied, the intervention control command is output so that the difference between the value of the manual control command and the value of the intervention control command becomes small within a range in which the constraint condition is satisfied. 9. A control system for a work machine according to any one of appendices 1 to 8. (Appendix 10) the processor outputs the intervention control command to the traveling device. 10. A control system for a work machine according to any one of Supplementary Note 1 to Supplementary Note 9. (Appendix 11) an external sensor for detecting obstacles around the work machine; The processor: when it is determined based on the detection data of the external sensor that there is a possibility that the work machine will come into contact with an obstacle, a manual control command is output based on the operation signal. 11. A control system for a work machine according to any one of Supplementary Notes 1 to 10. (Appendix 12) an external sensor for detecting obstacles around the work machine; The processor: When it is determined that there is a possibility that the work machine will come into contact with an obstacle based on the detection data of the external sensor, the traveling device is controlled so as to avoid contact between the work machine and the obstacle. 12. A control system for a work machine as described in claim 11. (Appendix 13) The car body and a work machine supported on the vehicle body; an external sensor disposed on the vehicle body; a control system for a work machine according to any one of Supplementary Notes 1 to 12; Work machinery. (Appendix 14) The car body and a work machine supported on the vehicle body; an external sensor disposed on the vehicle body; an on-board controller mounted on the vehicle body and receiving an operation signal from an operation device disposed outside the vehicle body; a control system for a work machine according to any one of Supplementary Notes 1 to 13; Remote control system for work machines. (Appendix 15) The processor: receiving an operation signal from an operation device operated to operate a work machine having a work implement and a traveling device; calculating constraint conditions for preventing a load held by the work machine from collapsing based on vehicle state parameters that indicate an operating state of the work machine; modifying the operation signal based on the constraint; A method for controlling a work machine. [Explanation of symbols]

[0152] 1...Work machine, 2...Vehicle body, 2F...Front frame, 2R...Rear frame, 3...Articulating mechanism, 4...Wheels, 4F...Front wheels, 4R...Rear wheels, 5...Traveling gear, 6...Work machine, 7...Articulating cylinder, 8...Boom, 9...Bucket, 10...Bell crank, 11...Bucket link, 12...Boom cylinder, 13...Bucket cylinder, 14...Bracket, 15...Bracket, 16...Driver, 17...Power take-off, 18...Power transmission a control unit for controlling the driving force of the vehicle, 19...brake device, 20...steering pump, 21...steering control valve, 22...work implement pump, 23...work implement control valve, 24...position sensor, 25...direction sensor, 26...speed sensor, 27...steering sensor, 28...work implement attitude sensor, 28A...boom angle sensor, 28B...bucket angle sensor, 29...external sensor, 30...load sensor, 31...camera, 32...on-board controller, 33...computer, 34...processor, 35...main memory, 36...storage, 37...input / output interface, 38...communication interface, 39...computer program, 40...operation signal receiving unit, 41...constraint condition calculation unit, 42...control command unit, 70...operation device, 70A...traveling system operation device, 70B...work implement operation device, 71...accelerator pedal, 72...brake pedal, 73...steering wheel, 74...forward / reverse switch lever, 75...boom lever, 76...bucket lever , 80...display device, 81...input device, 82...remote controller, 83...operator seat, 100...control system, 200...remote operation system, 201...work site, 202...remote operation room, 203...communication system, 301...work machine, 302...body, 306...work equipment, 307...mast, 308...bracket, 309...fork, 309L...fork, 309R...fork, 700...operating device, AP...setting range, Z0...zero moment point.

Claims

1. a processor; The processor: receiving an operation signal from an operation device operated to operate a work machine having a work implement and a traveling device; calculating constraint conditions for preventing a load held by the work machine from collapsing based on vehicle state parameters that indicate an operating state of the work machine; modifying the operation signal based on the constraint; Work machine control systems.

2. the processor calculates the constraint conditions based on the vehicle state parameters and load parameters indicating properties of a load held by the work machine.

2. A control system for a work machine according to claim 1.

3. The processor: When it is determined that the constraint condition is not satisfied while the operation signal is received, an intervention control command is output so that the constraint condition is satisfied.

2. A control system for a work machine according to claim 1.

4. The processor: calculating the constraint conditions based on an inertial force acting on the cargo, a shape of the cargo, and cargo parameters; 3. A control system for a work machine according to claim 2.

5. The cargo includes soil and sand, The load parameters include the adhesion of the soil, the angle of internal friction of the soil, and the density of the soil.

3. A control system for a work machine according to claim 2.

6. The processor: calculating the constraints based on load parameters including a mass of the load, an inertia tensor of the load, and a center of gravity location of the load; the constraint condition includes a condition that the zero moment point of the load does not deviate from a set range that is set based on the shape of the work machine.

2. A control system for a work machine according to claim 1.

7. The processor: Calculating the constraints based on the mass and static friction coefficient of the load; The constraint conditions include a condition that the component of the force acting on the load on the sliding surface does not exceed the static friction force.

2. A control system for a work machine according to claim 1.

8. The processor: Calculating the acceleration of the load while the work machine is traveling; The constraint condition includes a condition that the acceleration is less than a predetermined threshold.

2. A control system for a work machine according to claim 1.

9. The processor: If it is determined that the constraint condition is satisfied, a manual control command is output based on the operation signal; When it is determined that the constraint condition is not satisfied, the intervention control command is output so that the difference between the value of the manual control command and the value of the intervention control command becomes small within a range in which the constraint condition is satisfied.

4. A control system for a work machine according to claim 3.

10. the processor outputs the intervention control command to the traveling device.

4. A control system for a work machine according to claim 3.

11. an external sensor for detecting obstacles around the work machine; The processor: when it is determined based on the detection data of the external sensor that there is a possibility that the work machine will come into contact with an obstacle, a manual control command is output based on the operation signal.

2. A control system for a work machine according to claim 1.

12. an external sensor for detecting obstacles around the work machine; The processor: When it is determined that there is a possibility that the work machine will come into contact with an obstacle based on the detection data of the external sensor, the traveling device is controlled so as to avoid contact between the work machine and the obstacle.

12. A work machine control system according to claim 11.

13. The car body and a work machine supported on the vehicle body; an external sensor disposed on the vehicle body; and the work machine control system according to claim 1. Work machinery.

14. The car body and a work machine supported on the vehicle body; an external sensor disposed on the vehicle body; an on-board controller mounted on the vehicle body and receiving an operation signal from an operation device disposed outside the vehicle body; and the work machine control system according to claim 1. Remote control system for work machines.

15. The processor: receiving an operation signal from an operation device operated to operate a work machine having a work implement and a traveling device; calculating constraint conditions for preventing a load held by the work machine from collapsing based on vehicle state parameters that indicate an operating state of the work machine; modifying the operation signal based on the constraint; A method for controlling a work machine.

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