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

Abstract

To suppress deterioration of a working machine.SOLUTION: The control system of the work machine includes a controller. The controller determines whether or not there is a downward slope in a traveling direction of the work machine based on topographical data indicating a shape of a ground surface around the work machine, and outputs a control command for reducing a traveling speed of the work machine based on an inclination of the downward slope.SELECTED DRAWING: Figure 7

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] The work machine travels on the ground at the work site. When the work machine moves downhill on the ground at high speed, the work machine may be subjected to impacts. Impacts to the work machine may cause premature deterioration of the work machine.

[0005] The present disclosure aims to suppress deterioration of a work machine. [Means for solving the problem]

[0006] According to the present disclosure, there is provided a control system for a work machine including a controller, which determines whether there is a downward gradient in the direction of travel of the work machine based on topographical data indicating the shape of the ground around the work machine, and outputs a control command to reduce the travel speed of the work machine based on the inclination of the downward gradient. [Effects of the Invention]

[0007] According to the present disclosure, deterioration of the 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 a control system for a work machine according to the first embodiment. [Figure 5] FIG. 5 is a diagram for explaining predetermined traveling states of the work machine according to the first embodiment. [Figure 6] FIG. 6 is a diagram for explaining a method for detecting a downward slope according to the first embodiment. [Figure 7] FIG. 7 is a diagram for explaining a method for detecting a downward slope according to the first embodiment. [Figure 8] FIG. 8 is a flowchart showing a control method for a work machine according to the first embodiment. [Figure 9] FIG. 9 is a block diagram showing a control system for a work machine according to the second 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 diagram for explaining the operation of the work machine according to the second embodiment. [Figure 12]FIG. 12 is a diagram for explaining a method for detecting the topography of a work site using an acceleration sensor according to the second embodiment. [Figure 13] FIG. 13 is a flowchart showing a method for acquiring ground roughness data according to the second embodiment. [Figure 14] FIG. 14 is a diagram for explaining map data updated with rough road data according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of 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 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, 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 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.

[0016] <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.

[0017] 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.

[0018] The traveling gear 5 supports the vehicle body 2. The traveling gear 5 travels on the ground of the work site 201. 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. As the articulating cylinder 7 extends and retracts, the front frame 2F bends left and right relative to the rear frame 2R. As 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.

[0019] The wheels 4 come into contact with the ground at the work site 201. The front wheels 4F rotate about a rotation axis CXf. The rear wheels 4R rotate about a rotation axis CXr. When the work machine 1 travels in a straight line, the rotation axis CXf of the front wheels 4F and the rotation axis CXr of the rear wheels 4R are parallel. The rotation of the wheels 4 causes the work machine 1 to travel on the ground at the work site 201.

[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] A base end of the boom 8 is rotatably connected to the front frame 2F. The boom 8 rotates about a rotation axis AXa relative to the front frame 2F. A bracket 14 is fixed to the middle of the boom 8.

[0022] The bucket 9 is a working member for excavating an excavation target. The bucket 9 holds the excavated material. The bucket 9 has a cutting edge 9A, an opening 9B, and a bottom surface 9C.

[0023] A base end of the bucket 9 is rotatably connected to the tip end of the boom 8. The bucket 9 rotates around a rotation axis AXb relative to the boom 8. The bucket 9 is disposed forward of the front wheels 4F. A bracket 15 is fixed to a part of the bucket 9.

[0024] An intermediate portion of the bell crank 10 is rotatably connected to a bracket 14 of the boom 8. The bell crank 10 rotates about a rotation axis AXc relative to the bracket 14 of the boom 8. A lower end portion of the bell crank 10 is rotatably connected to a base end portion of a bucket link 11.

[0025] The tip end of the bucket link 11 is rotatably connected to a bracket 15 of the bucket 9. The bucket link 11 rotates about a rotation axis AXd relative to the bracket 15 of the bucket 9. The bell crank 10 is connected to the bucket 9 via the bucket link 11.

[0026] 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 boom 8 rotates relative to the boom cylinder 12 about a rotation axis AXe.

[0027] 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 an upper end of a bell crank 10. The bell crank 10 rotates relative to the bucket cylinder 13 about a rotation axis AXf.

[0028] The pivot axis AXa, the pivot axis AXb, the pivot axis AXc, the pivot axis AXd, the pivot axis AXe, the pivot axis AXf, and the rotation axis CXf of the front wheel 4F are parallel to each other. When the work machine 1 travels in a straight line, the pivot axis AXa of the work implement 6 and the rotation axis CXr of the rear wheel 4R are parallel to each other.

[0029] 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.

[0030] <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 50, 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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. The attitude of the boom 8 includes the angle and height of the boom 8. The attitude of the bucket 9 includes the angle and height of the bucket 9.

[0040] 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. In this embodiment, the boom angle is the angle 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 is traveling in a straight line. 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 boom angle sensor 28A.

[0041] Bucket angle sensor 28B detects a bucket angle that indicates the angle of bucket 9. The bucket angle refers to the angle of bucket 9 with respect to boom 8 in a local coordinate system defined for work machine 1. In this embodiment, the bucket angle is the angle between a line connecting pivot axis AXb and cutting edge 9A and a line connecting pivot axis AXa and pivot axis AXb. An example of bucket angle sensor 28B is an angle sensor that is disposed at the connection between boom 8 and bell crank 10. In this embodiment, bucket angle sensor 28B detects a bell crank angle that indicates the angle of bell crank 10 with respect to boom 8 in the local coordinate system. The bell crank angle is the angle between a line connecting pivot axis AXc and pivot axis AXf and a line connecting pivot axis AXa and pivot axis AXb. The bucket angle and the bell crank angle correspond one-to-one. 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.

[0042] The boom angle and bucket angle are each angles in the operating plane of the work implement 6 that is perpendicular to the rotation axis AXa. The line connecting the rotation axis AXa and the rotation axis AXb, the line connecting the rotation axis AXc and the rotation axis AXf, the line connecting the rotation axis AXb and the cutting edge 9A, and the line connecting the rotation axis CXf and the rotation axis CXr when the work machine 1 is traveling in a straight line are each lines in the operating plane of the work implement 6.

[0043] 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.

[0044] The external sensor 29 detects objects in the vicinity of the work machine 1. In this embodiment, the external sensor 29 is a shape sensor that detects the shapes of objects in the vicinity of the work machine 1. The external sensor 29 is a three-dimensional sensor that detects the three-dimensional shapes of objects in the vicinity of the work machine 1. The external sensor 29 is arranged 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 shape of the ground of the work site 201 in the vicinity of the work machine 1. The external sensor 29 detects the three-dimensional shape of the ground on which the work machine 1 travels. The external sensor 29 detects the three-dimensional shape of the ground before the wheels 4 of the work machine 1 pass over it.

[0045] 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.

[0046] 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.

[0047] The camera 50 captures an image of the work site 201. The camera 50 captures an image of at least the work site 201 in front of the work machine 1. The camera 50 captures an image of at least a portion of the work implement 6. The camera 50 is disposed, for example, in a cab provided on the rear frame 2R. Image data captured by the camera 50 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 50 on the display device 80.

[0048] The operation device 70 is operated by an operator to operate the work machine 1. When operated by the operator, the operation device 70 generates an operation signal for operating the work machine 1. The remote controller 82 transmits the operation signal generated in the operation device 70 to the work machine 1. The operation signal generated in 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.

[0049] 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.

[0050] 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. In other words, when the steering wheel 73 is operated, the traveling direction of the work machine 1 (traveling device 5) changes. When the forward / reverse selector lever 74 is operated, the work machine 1 (traveling device 5) switches between forward and reverse travel.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] <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.

[0055] 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.

[0056] <Control System> 4 is a block diagram showing a control system 100A of the work machine 1 according to this embodiment. The control system 100A 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. An operation signal from the operation device 70 is transmitted to the on-vehicle controller 32 via a communication system 203. The on-vehicle controller 32 transmits control commands to each of the traveling devices 5 and the work implement 6.

[0057] 4, the on-vehicle controller 32 has a sensor data acquisition unit 41, an operation signal acquisition unit 42, a vehicle state determination unit 43, a terrain determination unit 44, a threshold setting unit 45, and a control command unit 46. The functions of the sensor data acquisition unit 41, the operation signal acquisition unit 42, the vehicle state determination unit 43, the terrain determination unit 44, the threshold setting unit 45, and the control command unit 46 are realized by the computer 33 including the processor 34 described above.

[0058] The sensor data acquisition unit 41 acquires detection data from the position sensor 24, the direction sensor 25, the speed sensor 26, the steering sensor 27, the work equipment attitude sensor 28, the external environment sensor 29, and the cargo sensor 30.

[0059] The operation signal acquisition unit 42 acquires an operation signal from the operation device 70 that is operated to operate the work machine 1. The operation signal acquisition unit 42 receives the operation signal from the operation device 70 via the communication system 203.

[0060] The vehicle state determination unit 43 determines the vehicle state indicating the state of the work machine 1 based on the detection data acquired by the sensor data acquisition unit 41. The state of the work machine 1 includes the operating state of the work machine 1. The operating state of the work machine 1 includes the traveling state of the work machine 1. In this embodiment, the vehicle state determination unit 43 determines whether the traveling state of the work machine 1 is a predetermined specified traveling state based on the detection data acquired by the sensor data acquisition unit 41.

[0061] Figure 5 is a diagram for explaining a predetermined traveling state of the work machine 1 according to this embodiment. In this embodiment, the predetermined traveling state of the work machine 1 refers to a state in which the work machine 1 is moving forward, the traveling speed of the work machine 1 is equal to or greater than a predetermined first speed threshold, and the attitude of the work implement 6 is a predetermined specific attitude. The first speed threshold is, for example, 1 km / h.

[0062] As described above, the work implement 6 includes the boom 8 rotatably connected to the front frame 2F of the work machine 1 about a rotation axis AXa (first rotation axis), and the bucket 9 rotatably connected to the boom 8 about a rotation axis AXb (second rotation axis). If the line connecting the rotation axis CXf of the front wheels 4F and the rotation axis CXr of the rear wheels 4R when the work machine 1 is traveling in a straight line is defined as a specified line RL, then the rotation axis AXa is positioned above the specified line RL. Up is the direction away from the ground on which the work machine 1 is traveling. The specified posture of the work implement 6 is a posture in which the rotation axis AXb is positioned closer to the specified line RL than the rotation axis AXa, the bottom surface 9C of the bucket 9 is tilted forward so as to move away from the specified line RL, and the bucket 9 is off the ground. When the ground on which the work machine 1 travels is substantially parallel to the horizontal plane, i.e., when the specified line RL is parallel to the horizontal plane, the specified posture of the work implement 6 is a posture in which the pivot axis AXb is positioned below the pivot axis AXa, the bottom surface 9C of the bucket 9 is inclined upward toward the front, and the bucket 9 is off the ground.

[0063] The direction of travel of the work machine 1 (forward or reverse) and the traveling speed of the work machine 1 are detected by a speed sensor 26. The attitude of the work implement 6 is detected by a work implement attitude sensor 28. The vehicle state determination unit 43 can determine whether the work machine 1 is in a predetermined traveling state based on the detection data of the speed sensor 26 and the detection data of the work implement attitude sensor 28 acquired by the sensor data acquisition unit 41.

[0064] The predetermined traveling state does not have to include the work machine 6 being in a predetermined attitude. The predetermined traveling state may also be a state in which the traveling speed of the work machine 1 is equal to or greater than a predetermined first speed threshold.

[0065] The predetermined traveling state may be a state in which the work machine 1 is moving backward and the traveling speed of the work machine 1 is equal to or greater than a predetermined first speed threshold.

[0066] The terrain determination unit 44 determines the shape of the ground of the work site 201 that exists in the traveling direction of the work machine 1 based on the detection data acquired by the sensor data acquisition unit 41. The terrain determination unit 44 determines whether or not there is a downward slope on the ground in the traveling direction of the work machine 1 based on the detection data acquired by the sensor data acquisition unit 41. The terrain determination unit 44 determines whether or not there is a downward slope on the ground in the traveling direction of the work machine 1 based on terrain data that indicates the shape of the ground around the work machine 1 detected by the external sensor 29. The terrain data includes three-dimensional data that indicates the three-dimensional shape of the ground. The terrain determination unit 44 determines whether or not there is a downward slope on the ground in the traveling direction of the work machine 1 based on the three-dimensional data that indicates the three-dimensional shape of the ground around the work machine 1 detected by the external sensor 29. Downward slopes include downward slopes, downward steps, and cliffs.

[0067] 6 and 7 are diagrams for explaining a method for detecting a downward gradient according to this embodiment. The shape of the ground in the direction in which the work machine 1 travels is detected by an external sensor 29.

[0068] As shown in FIG. 6, when the work machine 1 moves forward, the ground surface in the traveling direction of the work machine 1 refers to the ground surface that exists ahead of the advancing work machine 1. As shown in FIG. 6, when the work machine 1 moves forward while turning, the terrain determination unit 44 identifies the ground surface in the traveling direction of the work machine 1 based on the detection data of the steering sensor 27. In the example shown in FIG. 6, the work machine 1 moves forward toward a downward slope with the vehicle body 2 bent. The work machine 1 approaches the downward slope while turning. The work machine 1 moves forward toward the downward slope along a curved trajectory line Tr. The trajectory line Tr is an imaginary line that passes through the center of the vehicle body 2 and the center of the bucket 9 in the vehicle width direction and extends toward the downward slope. The radius of the trajectory line Tr (the turning radius of the work machine 1) is determined based on the articulation angle. There is a one-to-one correspondence between the radius of the trajectory line Tr and the articulation angle. Even if a downward slope is not located in front of the external sensor 29 while the work machine 1 is traveling, it is possible to properly determine whether the work machine 1 is moving forward on a downward slope based on the detection data of the steering sensor 27.

[0069] The external sensor 29 is a three-dimensional sensor that detects three-dimensional data that indicates the three-dimensional shape of the ground. The three-dimensional data of the ground includes three-dimensional point cloud data. As shown in FIG. 7, the external sensor 29 can detect three-dimensional point cloud data of the ground in the traveling direction of the work machine 1. The three-dimensional point cloud data is made up of a plurality of detection points Pc. The external sensor 29 can detect the distance to a detection point Pc defined on the ground (earth's surface) in the traveling direction of the work machine 1. The external sensor 29 can detect the height of the detection point Pc.

[0070] As shown in Fig. 7, the terrain determination unit 44 sets a reference detection point Pcs on the ground with which the front wheels 4F come into contact. The terrain determination unit 44 determines whether there is a downward slope on the ground in the direction of travel of the work machine 1, based on a plurality of detection points Pc that exist in a detection range between the reference detection point Pcs and a detection point Pc that is a predetermined detection distance Dr away from the reference detection point Pcs in the direction of travel. The detection distance Dr is a predetermined value. The detection distance Dr may be set to the value of the dimension (total length) of the work machine 1 in the fore-and-aft direction, for example, or may be set to a value that is an integer multiple of the total length.

[0071] The terrain determination unit 44 calculates the inclination angle θ of the downward slope of the ground in the detection range based on the three-dimensional data of the ground detected by the external sensor 29. The terrain determination unit 44 determines whether the inclination angle θ of the downward slope is equal to or greater than a predetermined angle threshold. The terrain determination unit 44 detects the inclination angle θ between a horizontal plane and a line connecting a first detection point Pc and a second detection point Pc located further forward in the traveling direction than the first detection point Pc among the multiple detection points Pc. The distance between the first detection point Pc and the second detection point Pc is a predetermined value. The distance between the first detection point Pc and the second detection point Pc may be determined to be, for example, the diameter of the front wheel 4F.

[0072] In the example shown in FIG. 7, the inclination angle θv formed by the horizontal plane and a line connecting detection point Pcv and detection point Pc located further forward in the traveling direction than detection point Pcv is equal to or greater than the angle threshold. Of multiple detection points Pc where the inclination angle θ is equal to or greater than the threshold, detection point Pcv is the detection point Pc that is closest to the work machine 1. In other words, detection point Pcv is the detection point Pc where the inclination angle θ first becomes equal to or greater than the angle threshold when the work machine 1 moves forward in the traveling direction. The terrain determination unit 44 determines that detection point Pcv is the start position of the downward slope. The terrain determination unit 44 determines that the distance from reference detection point Pcs to detection point Pcv is the step distance Ds from the current position of the work machine 1 to the start position of the downward slope.

[0073] 7, the inclination angle θm at the detection point Pcm, which is further forward in the traveling direction than the detection point Pcv, is the maximum inclination angle θ within the detection range. The inclination angle θm is equal to or greater than the angle threshold value.

[0074] Note that, for example, if the downward gradient is steep, there is a possibility that the external sensor 29 will not be able to detect a detection point Pc that is further ahead in the traveling direction than the start position of the downward gradient within its detection range. In other words, there is a possibility that the external sensor 29 will not be able to detect some of the detection points Pc within its detection range. If the external sensor 29 is unable to detect some of the detection points Pc within its detection range, the terrain determination unit 44 may determine that the detection point Pc that is farthest from the work machine 1 in the traveling direction of the work machine 1, of the multiple detection points Pc detected by the external sensor 29, is the start position of the downward gradient.

[0075] The threshold setting unit 45 changes the angle threshold based on the detection data acquired by the sensor data acquisition unit 41. The threshold setting unit 45 changes the angle threshold based on, for example, detection data from the load sensor 30 that detects the weight of the work implement 6. The threshold setting unit 45 can determine whether the work implement 6 is in a loaded state or an unloaded state based on the detection data from the load sensor 30. The threshold setting unit 45 sets the angle threshold when the work implement 6 is in a loaded state to be smaller than the angle threshold when the work implement 6 is in an unloaded state. When the work implement 6 is in a loaded state, even if the inclination angle θ of the downward slope is small, the inclination angle θ is determined to be equal to or greater than the angle threshold.

[0076] The threshold setting unit 45 may change the angle threshold based on, for example, detection data from the speed sensor 26 that detects the traveling speed of the work machine 1. The threshold setting unit 45 sets the angle threshold when the traveling speed of the work machine 1 is equal to or greater than the first speed threshold and less than the second speed threshold described above to a smaller angle threshold than the angle threshold when the traveling speed of the work machine 1 is equal to or greater than the second speed threshold. When the work machine 1 is traveling at high speed, even if the inclination angle θ of the downward slope is small, the inclination angle θ is determined to be equal to or greater than the angle threshold.

[0077] The control command unit 46 outputs manual control commands that control the operation of the work machine 1 based on operation signals from the operation device 70. The control command unit 46 adjusts the traveling speed of the work machine 1, adjusts the traveling direction of the work machine 1, and switches between forward and reverse travel of the work machine 1 based on operation signals from the travel system operation device 70A. The control command unit 46 operates the work machine 6 based on operation signals from the work machine operation device 70B.

[0078] Furthermore, the control command unit 46 performs intervention control of the traveling device 5. Intervention control of the traveling device 5 refers to controlling the traveling device 5 so that the traveling device 5 operates under predetermined conditions while the traveling system operation device 70A is being operated. In other words, intervention control of the traveling device 5 refers to outputting an intervention control command from the control command unit 46 so that the traveling device 5 operates under predetermined conditions while the operation signal from the traveling system operation device 70A is being acquired by the operation signal acquisition unit 42.

[0079] The control command unit 46 outputs an intervention control command to reduce the traveling speed of the work machine 1 based on the inclination of the downward slope. In this embodiment, if the control command unit 46 determines that the inclination angle θ of the downward slope is equal to or greater than the angle threshold, it outputs an intervention control command to reduce the traveling speed of the work machine 1. If the control command unit 46 determines that the inclination angle θ is less than the angle threshold, it outputs a manual control command to operate the work machine 1 based on an operation signal from the operation device 70. If the control command unit 46 determines that the inclination angle θ is equal to or greater than the angle threshold and that the traveling speed of the work machine 1 is equal to or greater than the first speed threshold, it outputs an intervention control command to reduce the traveling speed of the work machine 1 regardless of the operation signal from the operation device 70.

[0080] The intervention control command for the traveling device 5 includes an automatic deceleration command to reduce the traveling speed or stop the work machine 1. When performing intervention control of the traveling device 5, the control command unit 46 outputs an automatic deceleration command to activate the brake device 19. When an intervention control command is output from the control command unit 46, the brake device 19 is activated regardless of an operation signal from the brake pedal 72, and the work machine 1 decelerates or stops. Note that when performing intervention control of the traveling device 5, the control command unit 46 may also output an automatic deceleration command to reduce the output of the drive machine 16. When an intervention control command is output from the control command unit 46, the output of the drive machine 16 is reduced regardless of an operation signal from the accelerator pedal 71, and the work machine 1 decelerates or stops.

[0081] When the terrain determination unit 44 determines that there is a downhill gradient with an inclination angle θ equal to or greater than the angle threshold in the direction of travel of the work machine 1, the control command unit 46 outputs an intervention control command to cause the work machine 1 to slow down or stop. The control command unit 46 outputs an intervention control command to prevent the work machine 1 from entering a downhill gradient. The control command unit 46 outputs an intervention control command to prevent the front wheels 4F from exceeding the detection point Pcv described with reference to Figure 7. Note that during intervention control, the work machine 1 may exceed the detection point Pcv.

[0082] The control command unit 46 determines the timing to start outputting an intervention control command based on the step distance Ds between the current position of the work machine 1 and the start position of the downward slope. The control command unit 46 determines the deceleration (negative acceleration) when reducing the traveling speed of the work machine 1 with an intervention control command, based on the traveling speed of the work machine 1. If the step distance Ds is short, the control command unit 46 outputs the intervention control command early. If the step distance Ds is long, the control command unit 46 may output the intervention control command after the work machine 1 approaches the detection point Pcv. If the traveling speed of the work machine 1 is high, the control command unit 46 outputs an intervention control command to suddenly brake the work machine 1.

[0083] The control command unit 46 may determine the deceleration rate when reducing the travel speed of the work machine 1 with an intervention control command, based on the maximum inclination angle θm of the downward gradient. If the inclination angle θm is large (if the difference between the inclination angle θm and the angle threshold is large), the control command unit 46 may output an intervention control command to apply sudden braking to the work machine 1 so that the work machine 1 stops at a position sufficiently far from (sufficiently in front of) the detection point Pcv. If the inclination angle θm is small (if the difference between the inclination angle θm and the angle threshold is small), the control command unit 46 may output an intervention control command to apply braking to the work machine 1 so that the work machine 1 stops at a position near the detection point Pcv.

[0084] The threshold setting unit 45 may set a first angle threshold and a second angle threshold as the angle thresholds. As an example, the first angle threshold is 10 degrees, and the second angle threshold is 20 degrees. The first angle threshold is an angle threshold for decelerating the work machine 1. The second angle threshold is an angle threshold for stopping the work machine 1. When the inclination angle θv of the detection point Pcv is equal to or greater than the first angle threshold and less than the second angle threshold, the control command unit 46 outputs an intervention control command for decelerating the work machine 1. When the inclination angle θv of the detection point Pcv is equal to or greater than the second angle threshold, the control command unit 46 outputs an intervention control command for stopping the work machine 1.

[0085] <Method for controlling a work machine> 8 is a flowchart showing a method for controlling the work machine 1 according to this embodiment. The sensor data acquisition unit 41 acquires detection data from the position sensor 24, the direction sensor 25, the speed sensor 26, the steering sensor 27, the work machine attitude sensor 28, the external environment sensor 29, and the load sensor 30. The operation signal acquisition unit 42 acquires an operation signal from the operation device 70 operated to operate the work machine 1 (step SA1).

[0086] The vehicle state determination unit 43 determines whether or not the work machine 1 is in a predetermined traveling state as described with reference to Figure 5, based on the detection data of the speed sensor 26 and the detection data of the work machine attitude sensor 28 (step SA2).

[0087] If it is determined in step SA2 that the work machine 1 is in a predetermined traveling state (step SA2: Yes), the terrain determination unit 44 determines whether there is a downward gradient in the traveling direction of the work machine 1 based on the detection data of the steering sensor 27 and the detection data of the external sensor 29 (step SA3).

[0088] In step SA3, if it is determined that there is a downward gradient in the direction of travel of the work machine 1 (step SA3: Yes), the control command unit 46 determines whether to start intervention control of the traveling device 5 based on the inclination angle θ of the downward gradient (step SA4).

[0089] The control command unit 46 determines to start intervention control when the tilt angle θv is equal to or greater than the angle threshold value, and determines not to start intervention control when the tilt angle θv is less than the angle threshold value.

[0090] If it is determined in step SA4 that intervention control is to be started (step SA4: Yes), the control command unit 46 outputs an intervention control command to decelerate or stop the work machine 1 (step SA5).

[0091] The control command unit 46 determines whether or not to end the intervention control based on the detection data of the speed sensor 26 (step SA6).

[0092] The control command unit 46 determines to end intervention control when it determines, based on the detection data of the speed sensor 26, that the traveling speed of the work machine 1 has decreased to less than the first speed threshold. The control command unit 46 determines to continue intervention control when it determines, based on the detection data of the speed sensor 26, that the traveling speed of the work machine 1 has not decreased to less than the first speed threshold.

[0093] If it is determined in step SA6 that the intervention control should be ended (step SA6: Yes), the control command unit 46 ends the intervention control. The work machine 1 operates based on an operation signal from the operation device 70. If it is determined in step SA6 that the intervention control should be continued (step SA6: No), the control command unit 46 continues to output the intervention control command.

[0094] If it is determined in step SA2 that the work machine 1 is not in the specified traveling state (step SA2: No), if it is determined in step SA3 that there is no downward gradient ahead in the traveling direction of the work machine 1 (step SA3: No), or if it is determined in step SA4 that intervention control will not be initiated (step SA4: No), the control command unit 46 outputs a manual control command based on the operation signal from the operating device 70 (step SA7).

[0095] <Effects> As described above, according to this embodiment, the on-board controller 32 is equipped with a terrain determination unit 44 that determines whether there is a downward gradient in the direction of travel of the work machine 1, based on three-dimensional data that indicates the three-dimensional shape of the ground around the work machine 1, and a control command unit 46 that outputs a control command to reduce the travel speed of the work machine 1 when it is determined that the inclination angle θ of the downward gradient is equal to or greater than the angle threshold.

[0096] According to this embodiment, the travel speed of the work machine 1 when entering a downward slope on the ground is reduced, or the work machine 1 is prevented from entering a downward slope on the ground. If the work machine enters a downward slope at high speed, or enters a steep downward slope, there is a possibility that an impact will be applied to the work machine 1. If an impact is applied to the work machine 1, there is a possibility that the work machine 1 will deteriorate prematurely. According to this embodiment, if the inclination angle θ of the downward slope in the traveling direction of the work machine 1 is equal to or greater than the angle threshold, the travel speed of the work machine 1 is reduced, thereby preventing deterioration of the work machine 1.

[0097] When the work machine 1 is remotely operated, the operator in the remote control room 202 is less likely to feel the impact that occurs when the work machine 1 enters a downslope at high speed or enters a steep downslope. For this reason, the operator in the remote control room 202 may operate the operation device 70 so that the work machine 1 enters a downslope at high speed or enters a steep downslope. According to this embodiment, when the operation device 70 is operated so that the work machine 1 enters a downslope at high speed or enters a steep downslope, intervention control is implemented to reduce the travel speed of the work machine 1. As a result, deterioration of the work machine 1 is suppressed.

[0098] [Second embodiment] A second embodiment will now be described. In the following description, components that are the same as or equivalent to those in the first embodiment described above will be given the same reference numerals, and descriptions of those components will be simplified or omitted.

[0099] In the first embodiment described above, the external sensor 29 detects the topography of the work site 201 in parallel with the travel of the work machine 1, and a determination is made as to whether intervention control is required based on the detection data of the external sensor 29. In the second embodiment, an example will be described in which map data showing the three-dimensional shape of the ground of the work site 201 is created in advance, and a determination is made as to whether intervention control is required based on the map data.

[0100] <Control System> Figure 9 is a block diagram showing a control system 100B for a work machine 1 according to this embodiment. In this embodiment, the on-board controller 32 has a map data storage unit 47 that stores map data in advance. The map data is defined in a global coordinate system. The work machine 1 also has an acceleration sensor 31 that detects the acceleration of the vehicle body 2. An example of the acceleration sensor 31 is an inertial sensor (IMU: Inertial Measurement Unit).

[0101] Map data can be created using any method. Examples of methods for creating map data include SLAM (Simultaneous Localization and Mapping) and VisualSLAM. Note that map data may be derived from design data (CAD data) of the work site 201. Note that map data may also be created by the work machine 1 traveling through the work site 201. The work machine 1 has an external sensor 29 that detects the three-dimensional shape of the ground of the work site 201 relative to the work machine 1, and a position sensor 24 that detects the absolute position of the work machine 1. The terrain determination unit 44 can create map data based on the detection data of the external sensor 29 and the detection data of the position sensor 24, and store the map data in the map data storage unit 47.

[0102] The map data includes position data indicating the position of the downward slope and inclination angle data indicating the inclination angle θ of the downward slope. The position data and inclination angle data of the downward slope are defined in a global coordinate system.

[0103] <Control method> 10 is a flowchart showing a method for controlling the work machine 1 according to this embodiment. The sensor data acquisition unit 41 acquires each of the detection data from the position sensor 24, the detection data from the direction sensor 25, the detection data from the speed sensor 26, the detection data from the steering sensor 27, the detection data from the work machine attitude sensor 28, the detection data from the external sensor 29, and the detection data from the load sensor 30. The operation signal acquisition unit 42 acquires an operation signal from the operation device 70 that has been operated to operate the work machine 1 (step SB1).

[0104] The terrain determination unit 44 estimates the self-position, which is the position of the work machine 1 in the global coordinate system, and the traveling direction based on the detection data of the position sensor 24 and the detection data of the orientation sensor 25 (step SB2).

[0105] The terrain determination unit 44 acquires map data for the traveling direction of the work machine 1 (step SB3).

[0106] The terrain determination unit 44 determines whether or not there is a downhill gradient in the direction of travel of the work machine 1, based on the self-position and travel direction estimated in step SB2 and the map data acquired in step SB3 (step SB4).

[0107] In step SB4, if it is determined that there is a downward gradient in the direction of travel of the work machine 1 (step SB4: Yes), the control command unit 46 determines whether to start intervention control of the traveling device 5 based on the inclination angle θ of the downward gradient (step SB5).

[0108] The control command unit 46 determines to start intervention control when the tilt angle θv is equal to or greater than the angle threshold value, and determines not to start intervention control when the tilt angle θv is less than the angle threshold value.

[0109] If it is determined in step SB5 that intervention control should be started (step SB5: Yes), the control command unit 46 outputs an intervention control command to decelerate or stop the work machine 1 (step SB6).

[0110] The control command unit 46 determines whether or not to end the intervention control based on the detection data of the speed sensor 26 (step SB7).

[0111] The control command unit 46 determines to end intervention control when it determines, based on the detection data of the speed sensor 26, that the traveling speed of the work machine 1 has decreased to less than the first speed threshold. The control command unit 46 determines to continue intervention control when it determines, based on the detection data of the speed sensor 26, that the traveling speed of the work machine 1 has not decreased to less than the first speed threshold.

[0112] If it is determined in step SB7 that the intervention control should be ended (step SB7: Yes), the control command unit 46 ends the intervention control. The work machine 1 operates based on an operation signal from the operation device 70. If it is determined in step SB7 that the intervention control should be continued (step SB7: No), the control command unit 46 continues to output the intervention control command.

[0113] If it is determined in step SB4 that there is no downward gradient ahead in the direction of travel of the work machine 1 (step SB4: No), and if it is determined in step SB5 that intervention control will not be initiated (step SB5: No), the control command unit 46 outputs a manual control command based on an operation signal from the operating device 70 (step SB8).

[0114] <How to update map data> As described above, map data may be created by having the work machine 1 travel through the work site 201. Map data may also be updated by having the work machine 1 travel through the work site 201. A method for updating map data will be described below.

[0115] 11 is a diagram for explaining the operation of the work machine 1 according to this embodiment. The work machine 1 has an acceleration sensor 31 that detects the acceleration of the vehicle body 2. An example of the acceleration sensor 31 is an inertial sensor (IMU: Inertial Measurement Unit). The terrain determination unit 44 updates the map data based on the detection data of the acceleration sensor 31.

[0116] The acceleration sensor 31 can detect the up and down movement and pitch of the vehicle body 2 when the work machine 1 travels on the ground. The pitch of the vehicle body 2 refers to the rotation of the vehicle body 2 about a pitch axis that extends in the left-right direction in a global coordinate system defined for the work machine 1. In the following description, the rotation of the front part of the vehicle body 2 (work implement 6) upward will be referred to as pitching in a positive direction, and the rotation of the front part of the vehicle body 2 (work implement 6) downward will be referred to as pitching in a negative direction.

[0117] FIG. 12 is a diagram illustrating a method for detecting the topography of the work site 201 using the acceleration sensor 31 according to this embodiment. As shown in FIG. 12, if there is a protrusion on the ground of the work site 201 and the front wheel 4F runs over the protrusion, the vehicle body 2 moves upward and pitches in a positive direction. If the rear wheel 4R runs over the protrusion, the vehicle body 2 moves upward and pitches in a negative direction. If there is a depression on the ground of the work site 201 and the front wheel 4F enters the depression, the vehicle body 2 moves downward and pitches in a negative direction. If the rear wheel 4R enters the depression, the vehicle body 2 moves downward and pitches in a positive direction.

[0118] The terrain determination unit 44 can estimate the terrain of the work site 201 based on the detection data of the acceleration sensor 31, which detects the vertical movement and pitch of the vehicle body 2. The terrain determination unit 44 can estimate the roughness of the ground at the work site 201 based on the detection data of the acceleration sensor 31. In the embodiment, the terrain determination unit 44 can calculate roughness data indicating the roughness of the ground at the work site 201, which is defined in the global coordinate system, based on the detection data of the position sensor 24 and the detection data of the acceleration sensor 31.

[0119] 13 is a flowchart showing a method for acquiring ground roughness data according to this embodiment. The sensor data acquisition unit 41 acquires the detection data from the position sensor 24 and the detection data from the acceleration sensor 31 (step SC1).

[0120] The terrain determination unit 44 estimates the self-position, which is the position of the work machine 1 in the global coordinate system, and the roughness of the ground, based on the detection data of the position sensor 24 and the detection data of the acceleration sensor 31 (step SC2).

[0121] The terrain determining unit 44 determines whether the roughness of the ground estimated in step SC2 is equal to or greater than a predetermined threshold value (step SC3).

[0122] The roughness of the ground refers to the height of the convex parts and the depth of the concave parts of the ground, as described with reference to Figure 12. The higher the convex parts or the deeper the concave parts, the rougher the ground is. When the roughness of the ground is above a threshold, it means that the height of the convex parts is above a threshold or the depth of the concave parts is above a threshold.

[0123] If it is determined in step SC3 that the roughness of the ground is equal to or greater than the threshold (step SC3: Yes), the terrain determination unit 44 records the roughness data of the road surface in the map data. That is, the terrain determination unit 44 updates the map data using the roughness data (step SC4).

[0124] The roughness data is defined in a global coordinate system, and areas with high roughness are added to the map data defined in the global coordinate system.

[0125] If it is determined in step SC3 that the roughness of the ground is not equal to or greater than the threshold (step SC3: No), the terrain determining unit 44 does not update the map data.

[0126] The terrain determination unit 44 determines whether or not to end the acquisition of roughness data (step SC5). If it is determined in step SC5 that the acquisition of roughness data should not be ended (step SC5: No), the terrain determination unit 44 continues to acquire the roughness data. If it is determined in step SC5 that the acquisition of roughness data should be ended (step SC5: No), the terrain determination unit 44 continues to acquire the roughness data.

[0127] 14 is a diagram illustrating map data updated with roughness data according to this embodiment. In the map data before the update, there are convex and concave parts on the ground. By updating the map data, roughness data calculated based on detection data from the acceleration sensor 31, which detects the vertical movement and pitch of the work machine 1, is reflected in the map data.

[0128] [Other embodiments] In the above embodiment, the terrain data indicating the shape of the ground at the work site 201 is three-dimensional data indicating the three-dimensional shape of the ground. The terrain data may also be two-dimensional data indicating the two-dimensional shape of the path of the work machine 1.

[0129] In the above-described embodiment, when it is determined that the inclination angle of the downward gradient is equal to or greater than the angle threshold, the control command unit 46 outputs a control command to reduce the traveling speed of the work machine 1. The control command unit 46 may also output a control command to reduce the traveling speed of the work machine 1 as the inclination angle of the downward gradient increases.

[0130] In the above-described embodiment, when intervention control is started, notification data indicating that intervention control has been started may be output from the display device 80.

[0131] In the above-described embodiment, some or all of the functions of the in-vehicle controller 32 may be provided in the remote controller 82. For example, the vehicle state determination unit 43, the terrain determination unit 44, and the threshold setting unit 45 may be provided in the remote controller 82.

[0132] In the above-described embodiment, the work machine 1 does not have to be remotely controlled. An operator may operate the work machine 1 by getting into the cab of the work machine 1.

[0133] In the above-described embodiment, the work machine 1 is a wheel loader. The work machine 1 may be any machine as long as it is equipped with a work implement. The work machine 1 may be a hydraulic excavator or a bulldozer equipped with a work implement.

[0134] [Note] The present disclosure can also be configured as follows. (Appendix 1) Equipped with a controller, The controller determining whether or not there is a downward gradient in the direction of travel of the work machine based on topographical data that indicates the shape of the ground around the work machine; outputting a control command to reduce the traveling speed of the work machine based on the gradient of the downward slope; Work machine control systems. (Appendix 2) The topographical data includes three-dimensional data indicating a three-dimensional shape of the ground. 10. A control system for a work machine as described in claim 1. (Appendix 3) The controller when it is determined that the inclination angle of the downward gradient is equal to or greater than an angle threshold, outputting a control command to reduce the traveling speed of the work machine. 10. A control system for a work machine according to claim 1 or 2. (Appendix 4) The controller acquiring an operation signal from an operation device operated to operate the work machine; When it is determined that the tilt angle is less than an angle threshold value, a manual control command is output to operate the work machine based on the operation signal; when it is determined that the inclination angle is equal to or greater than an angle threshold and the traveling speed of the work machine is equal to or greater than a speed threshold, an intervention control command to reduce the traveling speed of the work machine is output regardless of the operation signal. 4. A control system for a work machine as described in appended claim 3. (Appendix 5) The controller Calculating a start position of the downward slope based on the topographical data; determining the timing to start outputting the intervention control command based on the distance between the current position of the work machine and the start position of the downward gradient; 5. A control system for a work machine as described in appended claim 4. (Appendix 6) The controller determining a deceleration rate when reducing the traveling speed of the work machine in accordance with the intervention control command, based on the traveling speed of the work machine; 6. A control system for a work machine as described in appended claim 5. (Appendix 7) The controller changing the angle threshold value based on at least one of a traveling speed of the work machine and a weight of a work implement provided on the work machine; 7. A control system for a work machine according to any one of Supplementary Note 3 to Supplementary Note 6. (Appendix 8) the work machine has an external sensor that detects the shape of the ground, The controller determining whether or not there is a downward gradient based on the detection data of the external sensor; 8. A control system for a work machine according to any one of Supplementary Note 1 to Supplementary Note 7. (Appendix 9) The controller storing map data indicating the shape of the ground; determining whether or not there is a downward gradient in the traveling direction of the work machine based on the position and orientation of the work machine and the map data; 9. A control system for a work machine according to any one of appendices 1 to 8. (Appendix 10) The controller calculating roughness data indicating the roughness of the ground surface based on detection data from an acceleration sensor that detects the vertical movement and pitch of the work machine when the work machine travels on the ground surface; updating the map data using the roughness data; 10. A control system for a work machine as described in appended claim 9. (Appendix 11) The car body and a work machine supported on the vehicle body; a traveling device that supports the vehicle body and travels on the ground; and a control system for a work machine according to any one of Supplementary Notes 1 to 10. Work machinery. (Appendix 12) a remote controller that is disposed outside the work machine and transmits an operation signal generated in the operation device to the work machine; and a control system for a work machine according to any one of Supplementary Notes 1 to 10. Remote control system for work machines. (Appendix 13) The controller determining whether there is a downward gradient in the direction of travel of the work machine based on topographical data indicating the shape of the ground around the work machine; outputting a control command to reduce the travel speed of the work machine based on the gradient of the downward slope. A method for controlling a work machine. [Explanation of symbols]

[0135] 1...work machine, 2...body, 2F...front frame, 2R...rear frame, 3...articulation mechanism, 4...wheel, 4F...front wheel, 4R...rear wheel, 5...traveling gear, 6...work machine, 7...articulation cylinder, 8...boom, 9...bucket, 9A...blade tip, 9B...opening, 9C...bottom, 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 device 19...Brake device, 20...Steering pump, 21...Steering control valve, 22...Work implement pump, 23...Work implement control valve, 24...Position sensor, 25...Orientation 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...Acceleration sensor, 32...On-board controller, 33...Computer, 34...Processor, 35...Main memory, 36...Storage, 37 ...input / output interface, 38...communication interface, 39...computer program, 41...sensor data acquisition unit, 42...operation signal acquisition unit, 43...vehicle state determination unit, 44...terrain determination unit, 45...threshold setting unit, 46...control command unit, 47...map data storage unit, 50...camera, 70...operation device, 70A...travel system operation device, 70B...work equipment 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, 82...remote controller, 83...operator seat, 100A...control system, 100B...control system, 200...remote operation system, 201...work site, 202...remote operation room, 203...communication system, 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, Pc...detection point, Pcs...reference detection point, RL...specified line.

Claims

1. Equipped with a controller, The controller determining whether or not there is a downward gradient in the direction of travel of the work machine based on topographical data that indicates the shape of the ground around the work machine; outputting a control command to reduce the traveling speed of the work machine based on the gradient of the downward slope; Work machine control systems.

2. The topographical data includes three-dimensional data indicating a three-dimensional shape of the ground.

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

3. The controller when it is determined that the inclination angle of the downward gradient is equal to or greater than an angle threshold, outputting a control command to reduce the traveling speed of the work machine.

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

4. The controller acquiring an operation signal from an operation device operated to operate the work machine; When it is determined that the tilt angle is less than an angle threshold value, a manual control command is output to operate the work machine based on the operation signal; when it is determined that the inclination angle is equal to or greater than an angle threshold and the traveling speed of the work machine is equal to or greater than a speed threshold, an intervention control command to reduce the traveling speed of the work machine is output regardless of the operation signal.

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

5. The controller Calculating a start position of the downward slope based on the topographical data; determining the timing to start outputting the intervention control command based on the distance between the current position of the work machine and the start position of the downward gradient; 5. A control system for a work machine according to claim 4.

6. The controller determining a deceleration rate when reducing the traveling speed of the work machine in accordance with the intervention control command, based on the traveling speed of the work machine; A control system for a work machine according to claim 5.

7. The controller changing the angle threshold value based on at least one of a traveling speed of the work machine and a weight of a work implement provided on the work machine; 4. A control system for a work machine according to claim 3.

8. the work machine has an external sensor that detects the shape of the ground, The controller determining whether or not there is a downward gradient based on the detection data of the external sensor; 2. A control system for a work machine according to claim 1.

9. The controller storing map data indicating the shape of the ground; determining whether or not there is a downward gradient in the traveling direction of the work machine based on the position and orientation of the work machine and the map data; 2. A control system for a work machine according to claim 1.

10. The controller calculating roughness data indicating the roughness of the ground surface based on detection data from an acceleration sensor that detects the vertical movement and pitch of the work machine when the work machine travels on the ground surface; updating the map data using the roughness data; 10. A work machine control system according to claim 9.

11. The car body and a work machine supported on the vehicle body; a traveling device that supports the vehicle body and travels on the ground; and the work machine control system according to claim 1. Work machinery.

12. a remote controller that is disposed outside the work machine and transmits an operation signal generated in the operation device to the work machine; and the work machine control system according to claim 1. Remote control system for work machines.

13. The controller determining whether there is a downward gradient in the direction of travel of the work machine based on topographical data indicating the shape of the ground around the work machine; outputting a control command to reduce the travel speed of the work machine based on the gradient of the downward slope. A method for controlling a work machine.

Images