System for controlling work machine, work machine, system for remotely operating work machine, and method for controlling work machine

Abstract

This system for controlling a work machine comprises a controller. The controller recognizes a distance from a work machine to an excavation target, determines whether the work machine is traveling at a travel speed equal to or greater than a first speed threshold value, determines whether the work machine is moving forward toward the excavation target, and outputs a deceleration command for reducing the travel speed of the work machine when the work machine is determined to be traveling at a travel speed equal to or greater than the first speed threshold value, the work machine is determined to be moving forward toward the excavation target, and the distance is determined to be equal to or less than a distance threshold value.

Description

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

[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.

[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.

[0003] EP 3926107

[0004] A work machine operates based on an operation signal from an operating device operated by an operator. When excavating an excavation target, the operator moves the work machine forward toward the excavation target with the work implement of the work machine in an excavation position. The work implement enters the excavation target, causing the excavation target to be excavated by the work implement. If the travel speed of the work machine when entering the excavation target is excessively high, excessive load will be placed on the work machine, which may cause deterioration of the work machine.

[0005] The present disclosure aims to suppress deterioration of a work machine.

[0006] According to the present disclosure, there is provided a control system for a work machine including a controller, which recognizes the distance from the work machine to an excavation target, determines whether the work machine is traveling at a traveling speed equal to or greater than a first speed threshold, determines whether the work machine is moving forward toward the excavation target, and outputs a deceleration command to reduce the traveling speed of the work machine when it is determined that the work machine is traveling at a traveling speed equal to or greater than the first speed threshold, that the work machine is moving forward toward the excavation target, and that the distance is equal to or less than the distance threshold.

[0007] According to the present disclosure, deterioration of the work machine is suppressed.

[0008] FIG. 1 is a diagram showing a remote control system for a work machine according to an embodiment. FIG. 2 is a configuration diagram showing a work machine and an operation device according to an embodiment. FIG. 3 is a hardware configuration diagram showing an on-board controller according to an embodiment. FIG. 4 is a diagram explaining the operation of a work machine according to an embodiment. FIG. 5 is a functional block diagram showing a control system for a work machine according to an embodiment. FIG. 6 is a diagram explaining a method for recognizing an excavation target according to an embodiment. FIG. 7 is a diagram explaining a method for recognizing an excavation target that takes into account an articulation angle according to an embodiment. FIG. 8 is a diagram explaining a method for recognizing an excavation target that takes into account an articulation angle according to an embodiment. FIG. 9 is a diagram explaining a detection area of ​​an external sensor according to an embodiment. FIG. 10 is a diagram explaining a detection area of ​​an external sensor according to an embodiment. FIG. 11 is a flowchart showing a method for controlling a work machine according to an embodiment. FIG. 12 is a timing chart showing a method for controlling a work machine according to an embodiment.

[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] [Remote Control System] Figure 1 is a diagram showing a remote control system 200 for a work machine 1 according to an embodiment. The remote control system 200 remotely controls a work machine 1 that is located at a work site 201. At least a part of the remote control system 200 is disposed in a remote control room 202 provided outside the work machine 1. The remote control system 200 comprises an operation device 7, a display device 8, and a remote controller 9.

[0011] The operation device 7 is arranged in a remote control room 202 outside the work machine 1. The operation device 7 is operated by an operator in the remote control room 202. The operator can operate the operation device 7 while seated in the operator seat 10. The operator may also operate a portable operation device 700. The operation device 700 may be operated outside the remote control room 202.

[0012] The display device 8 is disposed in a remote control room 202 outside the work machine 1. An example of the display device 8 is a flat panel display such as a liquid crystal display or an organic EL display. The display device 8 displays at least an image of the work site 201. The display device 8 may also output audio of the work site 201.

[0013] The operator operates the operation device 7 while checking an image of the work site 201 displayed on the display device 8. The work machine 1 is remotely controlled by the operation device 7.

[0014] The remote controller 9 is placed in a remote control room 202 outside the work machine 1. The remote controller 9 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.

[0015] [Working Machine] In this embodiment, the working machine 1 is a wheel loader. As shown in Figure 1 , the working machine 1 includes a vehicle body 2, an articulating mechanism 3, a cab 4, wheels 5, a working implement 6, an external sensor 25, and a camera 29. The working machine 1 travels on the wheels 5 at a work site 201. The working machine 1 performs work using the working implement 6 at the work site 201. Examples of work that the working machine 1 can perform include excavation work, loading work, transporting work, and snow removal work.

[0016] The vehicle body 2 supports the work implement 6. The vehicle body 2 includes a front frame 2F and a rear frame 2R. The front frame 2F is located forward of the rear frame 2R. The front frame 2F and the rear frame 2R are connected by an articulation mechanism 3. The articulation mechanism 3 includes an articulation cylinder 11. The articulation cylinder 11 is a hydraulic cylinder. The articulation cylinder 11 connects the front frame 2F and the rear frame 2R. The rear frame 2R is connected to the front frame 2F via the articulation mechanism 3, which includes the articulation cylinder 11. As the articulation cylinder 11 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 cab 4 is located on top of the rear frame 2R.

[0017] The wheels 5 support the vehicle body 2. The wheels 5 include front wheels 5F attached to the front frame 2F and rear wheels 5R attached to the rear frame 2R. The front wheels 5F rotate about a rotation axis CXf. The rear wheels 5R rotate about a rotation axis CXr. When the work machine 1 travels in a straight line, the rotation axis CXf of the front wheels 5F and the rotation axis CXr of the rear wheels 5R are parallel. The rotation of the wheels 5 allows the work machine 1 to travel on the ground at the work site 201.

[0018] The work implement 6 is supported by the vehicle body 2. The work implement 6 is attached to the front end of the front frame 2F. At least a portion of the work implement 6 is disposed forward of the front frame 2F. The work implement 6 has a boom 12, a bucket 13, a bell crank 14, and a bucket link 15.

[0019] A base end of the boom 12 is rotatably connected to the front frame 2F. The boom 12 rotates about a rotation axis AXa relative to the front frame 2F. A bracket 16 is fixed to the middle portion of the boom 12.

[0020] The bucket 13 is a work member used to excavate the excavation target 300. The bucket 13 holds the material to be excavated. The bucket 13 has a cutting edge 13A, an opening 13B, and a bottom surface 13C. The material to be excavated enters the bucket 13 from the outside to the inside through the opening 13B, and exits the bucket 13 from the inside to the outside through the opening 13B. The cutting edge 13A is located at the bottom end of the opening 13B. The bottom surface 13C is located so as to extend rearward from the cutting edge 13A.

[0021] A base end of the bucket 13 is rotatably connected to the tip end of the boom 12. The bucket 13 rotates about a rotation axis AXb relative to the boom 12. The bucket 13 is disposed forward of the front wheels 5F. A bracket 17 is fixed to a part of the bucket 13.

[0022] An intermediate portion of the bell crank 14 is rotatably connected to a bracket 16 of the boom 12. The bell crank 14 rotates about a rotation axis AXc with respect to the bracket 16 of the boom 12. A lower end of the bell crank 14 is rotatably connected to a base end of a bucket link 15.

[0023] A tip end of the bucket link 15 is rotatably connected to a bracket 17 of the bucket 13. The bucket link 15 rotates about a rotation axis AXd relative to the bracket 17 of the bucket 13. The bell crank 14 is connected to the bucket 13 via the bucket link 15.

[0024] The boom 12 is operated by a boom cylinder 18. The boom cylinder 18 is a hydraulic cylinder. A base end of the boom cylinder 18 is connected to the front frame 2F. A tip end of the boom cylinder 18 is connected to the boom 12. The boom 12 rotates relative to the boom cylinder 18 about a rotation axis AXe.

[0025] The bucket 13 is operated by a bucket cylinder 19. The bucket cylinder 19 is a hydraulic cylinder. A base end of the bucket cylinder 19 is connected to the front frame 2F. A tip end of the bucket cylinder 19 is connected to an upper end of a bell crank 14. The bell crank 14 rotates relative to the bucket cylinder 19 about a rotation axis AXf.

[0026] 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 5F 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 5R are parallel to each other.

[0027] The external sensor 25 detects objects around the work machine 1. The external sensor 25 detects at least objects in front of the work machine 1. An example of the external sensor 25 is a three-dimensional sensor. An example of the three-dimensional sensor is a laser sensor (LiDAR: Light Detection and Ranging) that detects objects by emitting laser light. The three-dimensional sensor may be a radar sensor (RADAR: Radio Detection and Ranging) that detects objects by emitting radio waves, or a stereo camera. The external sensor may be a monocular camera. Objects may be recognized from images captured by a single camera using VSLAM (Visual Simultaneous Localization and Mapping) technology. Objects may be recognized (AI recognition) from images captured by a monocular camera using AI (Artificial Intelligence) technology. In the embodiment, the external sensor 25 is disposed on the rear frame 2R. The external sensor 25 is disposed on an upper part of the cab 4. The external sensor 25 may be disposed inside the cab 4 or on the front frame 2F.

[0028] The camera 29 captures an image of the work site 201. The camera 29 captures an image of at least the work site 201 in front of the work machine 1. The camera 29 captures an image of at least a portion of the work implement 6. In this embodiment, the camera 29 is disposed inside the cab 4.

[0029] [Configuration of Work Machine and Operating Device] Figure 2 is a configuration diagram showing a work machine 1 and an operating device 7 according to an embodiment. As shown in Figure 2, the work machine 1 is equipped with an engine 20, a power take-off (PTO) 21, a power transmission device 22, a brake device 23, a steering pump 24A, a steering control valve 37, an articulate cylinder 11, a work implement pump 24B, a boom control valve 38, a bucket control valve 39, a boom cylinder 18, a bucket cylinder 19, an external sensor 25, a vehicle speed sensor 26, a work implement attitude sensor 28, an articulate angle sensor 27, a camera 29, and an on-board controller 30.

[0030] The engine 20 is a drive source for the work machine 1. The engine 20 is supported by the vehicle body 2. A power take-off 21 distributes the drive force of the engine 20 to a power transmission device 22, a steering pump 24A, and a work implement pump 24B.

[0031] The power transmission device 22 transmits the driving force of the engine 20 to the wheels 5. The power transmission device 22 controls the traveling direction of the work machine 1. The traveling direction of the work machine 1 includes a forward direction and a reverse direction. The power transmission device 22 switches between forward and reverse traveling of the work machine 1. The power transmission device 22 may be a transmission having a plurality of speed change gears, or a transmission having a torque converter. The power transmission device 22 may be a hydraulic static transmission (HST) that combines a hydraulic pump and a hydraulic motor, or a hydraulic mechanical continuously variable transmission (HMT) that combines an HST and a planetary gear mechanism.

[0032] The brake device 23 reduces the traveling speed of the work machine 1. The brake device 23 brakes the work machine 1. The brake device 23 is a service brake. The brake device 23 has brake rotors provided on the front wheels 5F and the rear wheels 5R, respectively, and brake pads that are pressed against the brake rotors. The brake device 23 can adjust the deceleration force (braking force). The stronger the force pressing the brake pads against the brake rotors, the stronger the deceleration force.

[0033] The steering pump 24A is a hydraulic pump that is operated by the driving force generated by the engine 20. The hydraulic oil discharged from the steering pump 24A is supplied to the articulated cylinder 11 via a steering control valve 37. The steering control valve 37 controls the flow rate and direction of the hydraulic oil supplied from the steering pump 24A to the articulated cylinder 11.

[0034] The work implement pump 24B is a hydraulic pump that is operated by the driving force generated by the engine 20. The hydraulic oil discharged from the work implement pump 24B is supplied to the boom cylinder 18 via a boom control valve 38. The hydraulic oil discharged from the work implement pump 24B is supplied to the bucket cylinder 19 via a bucket control valve 39. The boom control valve 38 controls the flow rate and direction of the hydraulic oil supplied from the work implement pump 24B to the boom cylinder 18. The bucket control valve 39 controls the flow rate and direction of the hydraulic oil supplied from the work implement pump 24B to the bucket cylinder 19. The work implement 6 is operated by the hydraulic oil from the work implement pump 24B.

[0035] The external sensor 25 detects at least an object in front of the work machine 1. The detection data of the external sensor 25 is transmitted to the on-board controller 30.

[0036] The vehicle speed sensor 26 detects the traveling speed of the work machine 1. An example of the vehicle speed sensor 26 is a magnetic sensor that detects the rotation speed of a drive shaft connected to the wheels 5. The detection data of the vehicle speed sensor 26 is transmitted to the on-board controller 30.

[0037] The work implement attitude sensor 28 detects the attitude of the work implement 6. The attitude of the work implement 6 includes the angle of the work implement 6. The work implement attitude sensor 28 includes a boom angle sensor 28A that detects the attitude of the boom 12, and a bucket angle sensor 28B that detects the attitude of the bucket 13. The detection data of the work implement attitude sensor 28 is transmitted to the on-vehicle controller 30.

[0038] The attitude of the boom 12 includes the angle of the boom 12. The boom angle sensor 28A detects a boom angle that indicates the angle of the boom 12. The boom angle refers to the angle of the boom 12 with respect to the vehicle body 2 in the local coordinate system. In the 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. An example of the boom angle sensor 28A is an angle sensor that is arranged at the connection between the front frame 2F and the boom 12.

[0039] The attitude of the bucket 13 includes the angle of the bucket 13. The bucket angle sensor 28B detects a bucket angle that indicates the angle of the bucket 13. The bucket angle refers to the angle of the bucket 13 with respect to the boom 12 in a local coordinate system. In this embodiment, the bucket angle is the angle between a line connecting the rotation axis AXb and the cutting edge 13A and a line connecting the rotation axis AXa and the rotation axis AXb. An example of the bucket angle sensor 28B is an angle sensor that is disposed at the connection between the boom 12 and the bell crank 14. In this embodiment, the bucket angle sensor 28B detects a bell crank angle that indicates the angle of the bell crank 14 with respect to the boom 12 in the local coordinate system. The bell crank angle is the angle between a line connecting the rotation axis AXc and the rotation axis AXf and a line connecting the rotation axis AXa and the rotation axis AXb. The bucket angle and the bell crank angle have a one-to-one correspondence. The bucket angle sensor 28B detects the bell crank angle. The bucket angle is calculated based on the detected data of the bell crank angle and the detected data of the boom angle.

[0040] 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 13A, 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.

[0041] The articulation angle sensor 27 detects the articulation angle of the vehicle body 2. The front frame 2F bends left and right relative to the rear frame 2R. The articulation angle refers to the bending angle between the front frame 2F and the rear frame 2R. When the work machine 1 is traveling straight, the articulation angle is 0°. In other words, when the rotation axis CXf of the front wheel 5F and the rotation axis CXr of the rear wheel 5R are parallel, the articulation angle is 0°. An example of the articulation angle sensor 27 is a potentiometer disposed in the articulation mechanism. Note that the articulation angle sensor 27 may also be a stroke sensor that detects the stroke length of the articulation cylinder 11.

[0042] The camera 29 captures an image of the work site 201. The camera 29 captures an image of at least a portion of the work machine 6. The image data captured by the camera 29 is transmitted to the remote controller 9 via the on-board controller 30 and the communication system 203. The remote controller 9 displays the image data captured by the camera 29 on the display device 8.

[0043] The operation device 7 is operated by an operator. When operated by the operator, the operation device 7 generates an operation signal for operating the work machine 1. The operation signal generated by the operation device 7 is transmitted to the on-board controller 30 via the remote controller 9 and the communication system 203. The on-board controller 30 outputs a control command for operating the work machine 1 based on the operation signal transmitted from the remote controller 9. The operation device 7 includes a traveling system operation device 7A and a work implement operation device 7B.

[0044] The traveling system operation device 7A is operated by an operator to operate at least one of the engine 20, the power transmission device 22, and the brake device 23. The traveling system operation device 7A generates an operation signal to operate at least one of the engine 20, the power transmission device 22, and the brake device 23. The traveling system operation device 7A includes an accelerator pedal 71, a brake pedal 72, a steering wheel 73, and a forward / reverse switch lever 74.

[0045] The accelerator pedal 71 is operated to increase the traveling speed of the work machine 1. The brake pedal 72 is operated to decrease the traveling speed of the work machine 1. The steering wheel 73 is operated to adjust the traveling direction of the work machine 1. The forward / reverse selector lever 74 is operated to switch the traveling direction of the work machine 1. The forward / reverse selector lever 74 is operated to switch the work machine 1 between moving forward and reversing.

[0046] The work implement operating device 7B is operated by an operator to operate the work implement 6. The work implement operating device 7B generates an operation signal to operate the work implement 6. The work implement operating device 7B includes a boom lever 75 and a bucket lever 76.

[0047] The boom lever 75 is operated to raise or lower the boom 12. The bucket lever 76 is operated to tilt or dump the bucket 13. The raising operation of the boom 12 refers to the operation of the boom 12 rotating about the rotation axis AXa so that the tip of the boom 12 moves away from the ground. The lowering operation of the boom 12 refers to the operation of the boom 12 rotating about the rotation axis AXa so that the tip of the boom 12 moves closer to the ground. The tilting operation of the bucket 13 refers to the operation of the bucket 13 rotating about the rotation axis AXb so that the opening 13B of the bucket 13 faces upward and the blade tip 13A moves away from the ground. The dumping operation of the bucket 13 refers to the operation of the bucket 13 rotating about the rotation axis AXb so that the opening 13B of the bucket 13 faces downward and the blade tip 13A moves closer to the ground.

[0048] [On-Vehicle Controller] FIG. 3 is a hardware configuration diagram showing an on-vehicle controller 30 according to an embodiment. The on-vehicle controller 30 includes a computer system. The on-vehicle controller 30 includes a processor 31 such as a central processing unit (CPU), a main memory 32 including a nonvolatile memory such as a read-only memory (ROM) and a volatile memory such as a random access memory (RAM), a storage 33, an input / output interface 34 including an input / output circuit, and a communication interface 35 including a communication circuit. The functions of the on-vehicle controller 30 are stored in the storage 33 as a computer program. The processor 31 reads the computer program from the storage 33, loads it into the main memory 32, and executes processing in accordance with the computer program. The computer program may be distributed to the on-vehicle controller 30 via a network.

[0049] The remote controller 9 also includes a computer system. Like the in-vehicle controller 30, the remote controller 9 has a processor, a main memory, a storage, an input / output interface, and a communication interface.

[0050] [Operation of the Work Machine] Figure 4 is a diagram illustrating the operation of the work machine 1 according to the embodiment. At a work site 201, the work machine 1 excavates an excavation target 300. An example of the excavation target 300 is a stockpile placed on the ground at the work site 201. A stockpile is a pile of earth and sand. When excavating the excavation target 300, the operator moves the work machine 1 forward toward the excavation target 300 with the work implement 6 of the work machine 1 in an excavation posture. With the work implement 6 in an excavation posture, the work machine 1 moves forward so as to approach the excavation target 300. After the bucket 13 of the work implement 6 plunges into the excavation target 300, the bucket 13 tilts, causing the excavation target 300 to be excavated by the bucket 13.

[0051] The digging posture of the work implement 6 refers to a posture in which the bucket 13 can excavate the excavation target 300. The digging posture of the work implement 6 refers to a posture in which the cutting edge 13A of the bucket 13 is inserted into the lower end of the excavation target 300 as the work machine 1 moves forward toward the excavation target 300. The digging posture of the work implement 6 includes a posture in which the cutting edge 13A of the bucket 13 approaches or contacts the ground of the work site 201.

[0052] The work implement 6 includes a boom 12 rotatably connected to the front frame 2F of the work machine 1 about a rotation axis AXa, and a bucket 13 rotatably connected to the boom 12 about a rotation axis AXb. If a line connecting the rotation axis CXf of the front wheels 5F and the rotation axis CXr of the rear wheels 5R when the work machine 1 is traveling in a straight line is defined as a specified line RL, the rotation axis AXa is positioned above the specified line RL. "Up" refers to a direction away from the ground on which the work machine 1 is traveling. The excavation posture of the work implement 6 includes a state in which the rotation axis AXb is positioned closer to the ground than the specified line RL, and an angle formed between the bottom surface 13C of the bucket 13 and the ground on which the work machine 1 is traveling being equal to or less than a predetermined first angle threshold As. The first angle threshold As is, for example, 5°. In other words, the digging posture of the work implement 6 includes a situation in which at least a portion of the bucket 13 is approaching or in contact with the ground and the bottom surface 13C of the bucket 13 is approximately parallel to 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 digging posture of the work implement 6 includes a situation in which the rotation axis AXb is positioned below the specified line RL and the angle between the bottom surface 13C of the bucket 13 and the specified line RL is equal to or less than the first angle threshold As. The bottom surface 13C of the bucket 13 may be inclined downward toward the front or may be inclined upward toward the front. If the angle between the bottom surface 13C of the bucket 13 and the ground when the bottom surface 13C of the bucket 13 is inclined downward toward the front is taken as a negative value and the angle between the bottom surface 13C of the bucket 13 and the ground when the bottom surface 13C of the bucket 13 is inclined upward toward the front is taken as a positive value, the first angle threshold As may be −5°≦As≦+3°.

[0053] The digging posture of the work machine 6 may include the blade tip 13A of the bucket 13 approaching or contacting the ground. The distance between the ground and the blade tip 13A of the bucket 13 that satisfies the digging posture of the work machine 6 may be 10 cm or less.

[0054] 5 is a functional block diagram showing a control system 100 for a work machine 1 according to an embodiment. The control system 100 has an operation device 7, a remote controller 9, an on-board controller 30, an external sensor 25, a vehicle speed sensor 26, a work machine attitude sensor 28, an articulation angle sensor 27, and a camera 29.

[0055] The on-board controller 30 has a sensor data acquisition unit 101, an operation signal acquisition unit 102, an object recognition unit 103, an attitude determination unit 104, a driving determination unit 105, a driving control unit 106, a work machine control unit 107, and a transmission unit 108.

[0056] The sensor data acquisition unit 101 acquires detection data from the external sensor 25, the vehicle speed sensor 26, the work implement attitude sensor 28, and the articulate angle sensor 27. The detection data from the work implement attitude sensor 28 includes detection data from a boom angle sensor 28A indicating the boom angle and detection data from a bucket angle sensor 28B indicating the bucket angle.

[0057] The operation signal acquisition unit 102 acquires operation signals from the operation device 7. The operation signals from the operation device 7 include an operation signal from an accelerator pedal 71 operated to increase the traveling speed of the work machine 1, an operation signal from a brake pedal 72 operated to decrease the traveling speed of the work machine 1, an operation signal from a steering wheel 73 operated to adjust the traveling direction of the work machine 1, and an operation signal from a forward / reverse switch lever 74 operated to switch the traveling direction of the work machine 1. The operation signals from the operation device 7 also include an operation signal from a boom lever 75 operated to operate the boom 12, and an operation signal from a bucket lever 76 operated to operate the bucket 13.

[0058] The object recognition unit 103 identifies the excavation target 300 from objects present in the vicinity of the work machine 1 while the work machine 1 is moving forward. The object recognition unit 103 recognizes the excavation target 300 in front of the work machine 1 based on detection data from the external sensor 25. Based on detection data from the external sensor 25, the object recognition unit 103 recognizes, as the excavation target 300, an object whose height from the ground on which the work machine 1 is traveling is equal to or greater than a predetermined height threshold Hs. The object recognition unit 103 also recognizes the distance from the work machine 1 to the excavation target 300.

[0059] FIG. 6 is a diagram illustrating a method for recognizing an excavation target 300 according to an embodiment. Because the external sensor 25 is a three-dimensional sensor, it can detect the height of an object from the ground. The height threshold Hs is a predetermined value. As shown in FIG. 6 , the object recognition unit 103 recognizes, based on the detection data of the external sensor 25, an object whose height from the ground on which the work machine 1 is traveling is equal to or greater than the height threshold Hs as an excavation target 300. The object recognition unit 103 recognizes an object 400 whose height from the ground is less than the height threshold Hs as not being an excavation target. An object 400 whose height from the ground is less than the height threshold Hs may be recognized as a low stockpile, a convex portion on the ground, or a small lump of earth and sand. The height threshold Hs may be the height from the ground to the specified line RL or a height lower than the specified line RL. The height threshold Hs may also be the height from the ground to the center of the bucket 13 in the height direction when the bottom surface 13C of the bucket 13 is in contact with the ground. The height threshold Hs may be the height from the ground to the bottom surface 13C of the bucket 13 when the bottom surface 13C of the bucket 13 is off the ground, or the height from the ground to the center of the bucket 13 in the height direction.

[0060] The object recognition unit 103 also recognizes the distance from the work machine 1 to the excavation target 300. The distance from the work machine 1 to the excavation target 300 is the distance in the direction of travel of the work machine 1. When the object recognition unit 103 recognizes an object in front of the work machine 1 as the excavation target 300, it recognizes the distance from the work machine 1 to the excavation target 300. Because the external sensor 25 is a three-dimensional sensor, it can detect the distance from the work machine 1 to the excavation target 300. The distance from the work machine 1 to the excavation target 300 may be the distance from the reference point of the external sensor 25 to a detection point Ps defined on the surface of the excavation target 300. When the detection data of the external sensor 25 includes three-dimensional point cloud data of the surface of the excavation target 300, the detection point Ps defined on the excavation target 300 is at least one point in the three-dimensional point cloud data. At least one of the detection points Ps is defined at a height equal to the height threshold Hs. The distance from the work machine 1 to the excavation target 300 may be the distance from the reference point of the external sensor 25 to a detection point Ps defined at a height equal to the height threshold Hs.

[0061] The target recognition unit 103 also determines whether the distance from the work machine 1 to the excavation target 300 is equal to or less than a predetermined distance threshold Ls. The distance threshold Ls may be a value equal to the overall length of the work machine 1, for example. The overall length of the work machine 1 refers to the distance in the front-to-rear direction between the blade tip 13A of the bucket 13 and the rear end of the rear frame 2R. The distance threshold Ls may be a value equal to the wheelbase of the work machine 1. The wheelbase of the work machine 1 refers to the distance between the rotation axis CXf of the front wheels 5F and the rotation axis CXr of the rear wheels 5R.

[0062] The attitude determination unit 104 determines whether the work implement 6 is in an excavation attitude in which it excavates the excavation target 300. The attitude determination unit 104 determines whether the work implement 6 is in an excavation attitude based on detection data from the work implement attitude sensor 28. As described above, the excavation attitude of the work implement 6 includes the angle between the bottom surface 13C of the bucket 13 and the ground on which the work machine 1 travels being equal to or less than the predetermined first angle threshold value As. The excavation attitude of the work implement 6 may include the rotation axis AXb being positioned below the specified line RL. The excavation attitude of the work implement 6 may include the cutting edge 13A of the bucket 13 contacting the ground. The excavation attitude of the work implement 6 may include the cutting edge 13A of the bucket 13 being separated from the ground. The distance between the ground and the cutting edge 13A of the bucket 13 may be, for example, 10 cm or less.

[0063] The travel determination unit 105 determines whether the work machine 1 is traveling at a travel speed equal to or greater than a predetermined first speed threshold Fs1. The travel determination unit 105 also determines whether the work machine 1 is moving forward toward the excavation target 300.

[0064] The travel determination unit 105 can determine whether the travel speed of the work machine 1 is equal to or greater than a first speed threshold Fs1, based on detection data from the vehicle speed sensor 26. The first speed threshold Fs1 is, for example, 10 km / h. The maximum travel speed when the upper limit of the speed stage in a transmission having a torque converter is set to third or fourth speed may be set to the first speed threshold Sh1.

[0065] The vehicle speed sensor 26 can detect not only the traveling speed of the work machine 1 but also the rotation direction of the wheels 5. The traveling determination unit 105 can determine whether or not the work machine 1 is moving forward based on the detection data of the vehicle speed sensor 26. The traveling determination unit 105 can determine whether or not the work machine 1 is moving forward toward the excavation target 300 based on the detection data of the external sensor 25 and the detection data of the vehicle speed sensor 26. The traveling determination unit 105 may also determine whether or not the work machine 1 is moving forward based on an operation signal of the forward / reverse switch lever 74.

[0066] In the following description, the operation of the work machine 1 traveling at a speed equal to or greater than the first speed threshold Fs1 and moving forward toward the excavation target 300 will be referred to as "excavation traveling" as appropriate. That is, in the embodiment, the traveling determination unit 105 determines whether the work machine 1 is traveling at a speed equal to or greater than the first speed threshold Fs1 and is performing excavation traveling, moving forward toward the excavation target 300.

[0067] The traveling control unit 106 controls the traveling of the work machine 1 based on operation signals from the traveling system operation device 7A. Based on operation signals from the traveling system operation device 7A, the traveling control unit 106 adjusts the traveling speed of the work machine 1, adjusts the traveling direction of the work machine 1, and switches the work machine 1 between forward and reverse travel.

[0068] Furthermore, the driving control unit 106 outputs control commands so that the engine 20 and the brake device 23 each operate under predetermined conditions, regardless of the operation signal from the driving system operation device 7A. Even if the accelerator pedal 71 is operated, the driving control unit 106 can output control commands so that the engine 20 operates under predetermined conditions, regardless of the operation signal from the accelerator pedal 71. Even if the brake pedal 72 is not operated, the driving control unit 106 can output control commands so that the brake device 23 operates under predetermined conditions.

[0069] In the following description, a control command output from the travel control unit 106 to the brake device 23 to decelerate (brake) the work machine 1 based on an operation signal from the brake pedal 72 will be referred to as a manual deceleration command, and a control command output from the travel control unit 106 to the brake device 23 to decelerate the work machine 1 regardless of an operation signal from the brake pedal 72 will be referred to as an automatic deceleration command. Furthermore, the state in which the brake device 23 operates based on an automatic deceleration command will be referred to as automatic braking, as appropriate.

[0070] The automatic deceleration command may include a control command for reducing the output of the engine 20. In other words, the automatic deceleration command may include an automatic engine brake command for decelerating the work machine 1 by reducing the output of the engine 20. The automatic brake may include an automatic engine brake for reducing the output of the engine 20 based on the automatic deceleration command.

[0071] In an embodiment, when the travel control unit 106 determines that the work machine 6 is in an excavation posture, the work machine 1 is in excavation travel, and the distance from the work machine 1 to the excavation target is determined to be less than the distance threshold Ls, it outputs an automatic deceleration command to reduce the travel speed of the work machine 1.

[0072] The travel control unit 106 stops outputting the automatic deceleration command after the travel speed of the work machine 1 has fallen to a predetermined second speed threshold Fs2 or below due to the automatic deceleration command. The second speed threshold Fs2 is a value smaller than the first speed threshold Fs1. The second speed threshold Fs2 is, for example, 8 km / h. The second speed threshold Sh2 is set to the same value as the travel speed when the work machine 1 is performing excavation work. The second speed threshold Sh2 may be set to the maximum travel speed when the upper limit of the speed stage in a transmission having a torque converter is set to second gear.

[0073] When the automatic deceleration command is output while the work machine 1 is traveling at a traveling speed equal to or greater than the first speed threshold Fs1, the traveling speed of the work machine 1 decreases below the first speed threshold Fs1 and eventually decreases to or below the second speed threshold Fs2. After the traveling speed of the work machine 1 decreases to or below the second speed threshold Fs2, the traveling control unit 106 stops outputting the automatic deceleration command. With the output of the automatic deceleration command stopped, the work machine 1 travels based on operation signals from the accelerator pedal 71 and the brake pedal 72. With the traveling speed of the work machine 1 suppressed to or below the second speed threshold Fs2, the bucket 13 of the work implement 6 plunges into the excavation target 300.

[0074] In an embodiment, when the work machine 6 is determined to be in an excavation posture and the work machine 1 is determined to be excavating traveling, the travel control unit 106 outputs an automatic deceleration command when the distance from the work machine 1 to the excavation target reaches the distance threshold value Ls.

[0075] The travel control unit 106 may adjust the command value of the automatic deceleration command based on the travel speed of the work machine 1 when the work machine 1 is traveling at a travel speed equal to or greater than the first speed threshold Fs1. The larger the command value of the automatic deceleration command, the stronger the deceleration force (braking force) by the brake device 23, and the smaller the command value of the automatic deceleration command, the weaker the deceleration force by the brake device 23. In an embodiment, the larger the command value of the automatic deceleration command, the stronger the force pressing the brake pad against the brake rotor, and the smaller the command value of the automatic deceleration command, the weaker the force pressing the brake pad against the brake rotor. The travel control unit 106 may output the automatic deceleration command so that the deceleration force becomes stronger the higher the travel speed of the work machine 1. By adjusting the command value of the automatic deceleration command so that the deceleration force becomes stronger the higher the travel speed of the work machine 1, the travel speed of the work machine 1 becomes equal to or less than the second speed threshold Fs2 in a short period of time.

[0076] After starting to output the automatic deceleration command, the traveling control unit 106 may adjust the command value of the automatic deceleration command based on the distance from the work machine 1 to the excavation target 300. After starting to output the automatic deceleration command, the traveling control unit 106 may output the automatic deceleration command so that the deceleration force (braking force) becomes stronger the shorter the distance from the work machine 1 to the excavation target 300. In other words, after starting to output the automatic deceleration command, the traveling control unit 106 may gradually increase the deceleration force as the distance from the work machine 1 to the excavation target 300 becomes shorter.

[0077] The work implement control unit 107 controls the work implement 6 based on an operation signal from the work implement operating device 7B. The work implement control unit 107 controls the boom control valve 38 based on an operation signal from the boom lever 75. By controlling the boom control valve 38, the boom cylinder 18 extends and retracts, and the boom 12 performs a raising and lowering operation. The work implement control unit 107 controls the bucket control valve 39 based on an operation signal from the bucket lever 76. By controlling the bucket control valve 39, the bucket cylinder 19 extends and retracts, and the bucket 13 performs a tilting operation and a dumping operation.

[0078] The transmission unit 108 transmits image data captured by the camera 29 to the remote controller 9. The transmission unit 108 may also transmit detection data of the work machine attitude sensor 28 to the remote controller 9.

[0079] [Consideration of Articulation Angle] Figures 7 and 8 are diagrams illustrating a method for recognizing an excavation target 300 that takes into account the articulation angle according to an embodiment. The body 2 of the work machine 1 is bendable by the articulation mechanism 3. The front frame 2F is bendable in the left-right direction relative to the rear frame 2R. As shown in Figures 7 and 8, the work machine 1 may move forward toward the excavation target 300 with the body 2 bent.

[0080] As shown in Figure 7, when the vehicle body 2 is bent, it becomes difficult for the external sensor 25 arranged on the rear frame 2R to detect the excavation target 300 present in front of the bucket 13. For the external sensor 25 arranged on the rear frame 2R to detect the excavation target 300 present in front of the bucket 13, the vehicle body 2 must not be bent. In other words, for the external sensor 25 arranged on the rear frame 2R to detect the excavation target 300 present in front of the bucket 13, the work machine 1 must be traveling in a straight line. Therefore, the traveling determination unit 105 may determine whether the articulation angle of the vehicle body 2 is equal to or less than a predetermined second angle threshold Bs. In other words, the traveling determination unit 105 may determine that the work machine 1 is traveling for excavation when the articulation angle of the vehicle body 2 is equal to or less than the second angle threshold Bs and the work machine 1 is moving forward toward the excavation target 300 at a traveling speed equal to or greater than the first speed threshold Fs1. The travel control unit 106 may output a deceleration command to reduce the travel speed of the work machine 1 when it is determined that the work machine 6 is in an excavation posture, that the work machine 1 is traveling at a travel speed equal to or greater than the first speed threshold Fs1, that the work machine 1 is moving forward toward the excavation target 300, that the distance from the work machine 1 to the excavation target 300 is equal to or less than the distance threshold Ls, and that the articulation angle of the vehicle body 2 is equal to or less than the second angle threshold Bs. If the articulation angle when the front frame 2F is bent leftward relative to the rear frame 2R is taken as a negative value and the articulation angle when the front frame 2F is bent rightward relative to the rear frame 2R is taken as a positive value, the second angle threshold Bs may be -1°≦Bs<+1°. Since the conditions for determining whether the work machine 1 is traveling for excavation include the work machine 1 being in a straight-ahead state, the detection point Ps of the excavation target 300 is located directly in front of the external environment sensor 25. This prevents the external sensor 25 from erroneously detecting the excavation target 300 .

[0081] As shown in Fig. 8 , the travel determination unit 105 may determine whether the work machine 1 is moving forward toward the excavation target 300 based on detection data from the articulation angle sensor 27. In the example shown in Fig. 8 , the work machine 1 moves forward toward the excavation target 300 with the vehicle body 2 bent. The work machine 1 approaches the excavation target 300 while turning. The work machine 1 moves forward toward the excavation target 300 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 13 in the vehicle width direction, and extends toward the excavation target 300. The radius of the trajectory line Tr (the turning radius of the work machine 1) is defined 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 the detection point Ps of the excavation target 300 is not located directly in front of the external sensor 25 while the work machine 1 is traveling, it is possible to determine whether the work machine 1 is moving forward toward the excavation target 300 based on the detection data of the articulation angle sensor 27, and the travel control unit 106 can output an automatic deceleration command at the appropriate timing.

[0082] 9 and 10 are diagrams illustrating the detection area of ​​the external sensor 25 according to the embodiment. As shown in Fig. 9, the detection area of ​​the external sensor 25 may be set only on a detection line Sr that coincides with the track line Tr of the vehicle body 2. In other words, only one detection point Ps on the surface of the excavation target 300 may be defined in the vehicle width direction. Because there are fewer detection points Ps, the calculation load when recognizing the excavation target 300 is reduced.

[0083] As shown in Figure 10, the detection area of ​​the external sensor 25 may be set on each of a plurality of detection lines Sr that are parallel to the track line Tr of the vehicle body 2 in the vehicle width direction and intersect with the bucket 13. In other words, a plurality of detection points Ps on the surface of the excavation target 300 may be defined in the vehicle width direction. The vehicle width direction dimension of the detection area in which the plurality of detection points Ps are defined may be equal to or less than the width of the bucket 13. By increasing the number of detection points Ps in the vehicle width direction, the object recognition unit 103 can recognize the shortest distance from the work machine 1 to the excavation target 300. In other words, the object recognition unit 103 can recognize the closest point Pn of the excavation target 300 to the work machine 1.

[0084] [Work machine control method] Figure 11 is a flowchart showing a control method for the work machine 1 according to the embodiment. The operation signal acquisition unit 102 acquires an operation signal from the operation device 7. The traveling control unit 106 controls the traveling of the work machine 1 based on an operation signal from the traveling system operation device 7A. The work implement control unit 107 controls the work implement 6 based on an operation signal from the work implement operation device 7B. The sensor data acquisition unit 101 acquires detection data from the external sensor 25, detection data from the vehicle speed sensor 26, detection data from the work implement attitude sensor 28, and detection data from the articulation angle sensor 27 (step S1).

[0085] The attitude determination unit 104 determines whether or not the work implement 6 is in an excavation attitude based on the detection data of the work implement attitude sensor 28 (step S2).

[0086] In step S2, if it is determined that the work machine 6 is in an excavation position (step S2: Yes), the travel determination unit 105 determines whether the work machine 1 is traveling at a travel speed equal to or greater than the first speed threshold Fs1 based on the detection data of the vehicle speed sensor 26 (step S3).

[0087] If it is determined in step S3 that the work machine 1 is traveling at a traveling speed equal to or greater than the first speed threshold Fs1 (step S3: Yes), the target recognition unit 103 recognizes the excavation target 300 from objects present in front of the work machine 1 based on the detection data of the external sensor 25. If the target recognition unit 103 recognizes the excavation target 300, the traveling determination unit 105 determines whether the work machine 1 is moving forward toward the excavation target 300 based on the detection data of the external sensor 25 and the detection data of the vehicle speed sensor 26 (step S4).

[0088] In step S4, if it is determined that the work machine 1 is moving forward toward the excavation target 300 (step S4: Yes), the target recognition unit 103 determines whether the distance from the work machine 1 to the excavation target 300 is less than or equal to the distance threshold Ls based on the detection data of the external sensor 25 (step S5).

[0089] In step S5, if it is determined that the distance from the work machine 1 to the excavation target 300 is less than or equal to the distance threshold Ls (step S5: Yes), the travel control unit 106 outputs an automatic deceleration command to the brake device 23 to reduce the travel speed of the work machine 1 (step S6).

[0090] After outputting the automatic deceleration command, the travel control unit 106 determines whether the travel speed of the work machine 1 has decreased to or below the second speed threshold Fs2 based on the detection data of the vehicle speed sensor 26 (step S7).

[0091] In step S7, if it is determined that the traveling speed of the work machine 1 has not decreased to or below the second speed threshold Fs2 (step S7: No), the traveling control unit 106 continues to output the automatic deceleration command.

[0092] If it is determined in step S7 that the traveling speed of the work machine 1 has dropped to or below the second speed threshold Fs2 (step S7: Yes), the travel control unit 106 stops outputting the automatic deceleration command (step S8). Stopping the output of the automatic deceleration command deactivates the brake device 23. When the traveling speed of the work machine 1 has dropped to the second speed threshold Fs2, deactivating the brake device 23 causes the work machine 1 to continue traveling at a traveling speed that is close to the second speed threshold Fs2. As the work machine 1 continues traveling, the bucket 13 of the work implement 6 plunges into the excavation target 300. When the work machine 1 is traveling at a traveling speed that is close to the second speed threshold Fs2, the bucket 13 of the work implement 6 plunges into the excavation target 300.

[0093] If it is determined in step S2 that the work machine 6 is not in an excavation posture (step S2: No), if it is determined in step S3 that the work machine 1 is not traveling at a traveling speed equal to or greater than the first speed threshold Fs1 (step S3: No), if it is determined in step S4 that the work machine 1 is not moving forward toward the excavation target 300 (step S4: No), or if it is determined in step S5 that the distance from the work machine 1 to the excavation target 300 is not equal to or less than the distance threshold Ls (step S5: No), the traveling control unit 106 controls the work machine 1 based on the operation signal from the traveling system operating device 7A without outputting an automatic deceleration command.

[0094] Figure 12 is a timing chart showing a control method for the work machine 1 according to the embodiment. In Figure 12, the horizontal axis represents time, and the vertical axis represents the detection data of the work machine attitude sensor 28, the traveling speed of the work machine 1, the distance from the work machine 1 to the excavation target 300, and the command value of the automatic deceleration command output from the travel control unit 106 to the brake device 23.

[0095] 12 shows a state in which the work machine 1 has been moving forward at a traveling speed Fm since time t0. The work machine attitude sensor 28 outputs detection data Am which indicates that the work machine 6 is in an excavation attitude. The traveling speed Fm of the work machine 1 at time t0 is equal to or greater than the first speed threshold Fs1. Furthermore, as the work machine 1 is moving forward toward the excavation target 300, the distance Lm from the work machine 1 to the excavation target 300, which is recognized by the target recognition unit 103, gradually becomes shorter.

[0096] At time t1, it is determined that the work machine 6 is in an excavation position, it is determined that the work machine 1 is in an excavation traveling state, advancing toward the excavation target 300 at a traveling speed greater than or equal to the first speed threshold Fs1, and it is determined that the distance from the work machine 1 to the excavation target 300 is less than or equal to the distance threshold Ls.

[0097] At time t1, the travel control unit 106 outputs an automatic deceleration command of command value Vm to reduce the travel speed of the work machine 1. The travel control unit 106 continues to output the automatic deceleration command until the travel speed Fm of the work machine 1 becomes equal to or less than the second speed threshold value Fs2. In the example shown in Figure 12, at time t2, the travel speed Fm of the work machine 1 decreases to the second speed threshold value Fs2.

[0098] At time t2, the travel control unit 106 stops outputting the automatic deceleration command. As a result of the output of the automatic deceleration command being stopped, the work machine 1 moves forward toward the excavation target 300 at a travel speed that is equal to or less than the second speed threshold Fs2 and greater than 0 km / h. The work machine 1 moves forward toward the excavation target 300 at a travel speed that approximates the second speed threshold Fs2. As the work machine 1 moves forward toward the excavation target 300 at a travel speed that approximates the second speed threshold Fs2, the bucket 13 of the work implement 6 plunges into the excavation target 300 at a plunge speed that approximates the second speed threshold Fs2. When the bucket 13 plunges into the excavation target 300, the travel speed of the work machine 1 drops sharply. After the bucket 13 plunges into the excavation target 300, the bucket 13 tilts, causing the excavation target 300 to be excavated by the bucket 13. As the bucket 13 tilts, the excavated material is scooped up by the bucket 13.

[0099] [Effects] As described above, in the embodiment, the control system 100 of the work machine 1 includes an on-board controller 30. The on-board controller 30 has an object recognition unit 103 that recognizes the distance Lm from the work machine 1 to the excavation target 300, a travel determination unit 105 that determines whether the work machine 1 is traveling in an excavation mode, advancing toward the excavation target 300 at a travel speed Fm that is equal to or greater than the first speed threshold Fs1, and a travel control unit 106 that outputs an automatic deceleration command to reduce the travel speed Fm of the work machine 1 when it is determined that the work machine 1 is traveling in an excavation mode and that the distance Lm is equal to or less than the distance threshold Ls.

[0100] According to the embodiment, during excavation work in which the bucket 13 is plunged into the excavation target 300, if the traveling speed of the work machine 1 is high when the bucket 13 is plunged into the excavation target 300, the automatic brake is activated before the bucket 13 plunges into the excavation target 300. The bucket 13 plunges into the excavation target 300 after the traveling speed of the work machine 1 is reduced by activation of the automatic brake, thereby reducing the load on the work machine 1. This prevents deterioration of the work machine 1. According to the embodiment, the bucket 13 of the work implement 6 plunges into the excavation target 300 with the traveling speed of the work machine 1 kept at or below the second speed threshold Fs2, so the load on the work implement 6 is prevented from becoming excessive.

[0101] After the travel speed of the work machine 1 drops to or below the second speed threshold Sh2 due to activation of the automatic brake, output of the automatic deceleration command is stopped. After output of the automatic deceleration command is stopped, the work machine 1 can continue traveling at a travel speed that approximates the second speed threshold Fs2. The second speed threshold Fs2 is a value greater than 0 km / h. The bucket 13 can plunge into the excavation target 300 at a plunge speed that approximates the second speed threshold Fs2, and therefore can excavate the excavation target 300.

[0102] When work machine 1 is remotely operated, it is difficult for the operator in remote control room 202 to realize that work machine 1 is traveling at a high travel speed. As a result, the operator may cause bucket 13 to crash into excavation target 300 while work machine 1 is traveling at a high travel speed. According to the embodiment, when work machine 1 is moving forward toward excavation target 300 at a high travel speed that is equal to or greater than first speed threshold Fs1, the automatic brake is activated before bucket 13 crashes into excavation target 300. With the travel speed of work machine 1 suppressed to equal to or less than second speed threshold Fs2, bucket 13 of work implement 6 crashes into excavation target 300. As a result, the load on work machine 1 is reduced.

[0103] Other Embodiments In the above-described embodiments, if it is determined that the work machine 6 is in an excavation posture, if it is determined that the work machine 1 is traveling at a travel speed equal to or greater than the first speed threshold Fs1, if it is determined that the work machine 1 is moving forward toward the excavation target 300, and if it is determined that the distance Lm is equal to or less than the distance threshold Ls, then an automatic deceleration command to reduce the travel speed Fm of the work machine 1 is output from the travel control unit 106. The fact that the work machine 6 is in an excavation posture does not need to be included in the factors for determining whether or not to output an automatic deceleration command. In other words, if it is determined that the work machine 1 is traveling at a travel speed equal to or greater than the first speed threshold Fs1, if it is determined that the work machine 1 is moving forward toward the excavation target 300, and if it is determined that the distance Lm is equal to or less than the distance threshold Ls, then the travel control unit 106 may output a deceleration command to reduce the travel speed of the work machine 1.

[0104] In the above-described embodiment, when an automatic deceleration command is output, notification data indicating that the automatic brake has been activated may be output from the display device 8 .

[0105] In the above-described embodiment, some or all of the functions of the in-vehicle controller 30 may be provided in the remote controller 9. For example, the object recognition unit 103, the attitude determination unit 104, and the driving determination unit 105 may be provided in the remote controller 9.

[0106] In the above-described embodiment, the work machine 1 does not have to be remotely operated. An operator may operate the work machine 1 by getting into the cab 4 of the work machine 1.

[0107] In the above-described embodiment, the work machine 1 is a wheel loader. However, the work machine 1 may be any work machine equipped with a work implement for performing excavation work. The work machine 1 may be, for example, a bulldozer.

[0108] [Supplementary Notes] The present disclosure may also adopt the following configurations. (Supplementary Note 1) A work machine control system comprising a controller, wherein the controller recognizes the distance from the work machine to an excavation target, determines whether the work machine is traveling at a travel speed equal to or greater than a first speed threshold, determines whether the work machine is moving forward toward the excavation target, and outputs a deceleration command to reduce the travel speed of the work machine when it is determined that the work machine is traveling at a travel speed equal to or greater than the first speed threshold, that the work machine is moving forward toward the excavation target, and it is determined that the distance is equal to or less than the distance threshold. (Supplementary Note 2) The work machine control system described in (Supplementary Note 1), wherein the controller stops outputting the deceleration command after the travel speed of the work machine has decreased to or below a second speed threshold that is smaller than the first speed threshold as a result of outputting the deceleration command. (Supplementary Note 3) The work machine control system described in (Supplementary Note 1) or (Supplementary Note 2), wherein the controller outputs the deceleration command so that the deceleration force becomes stronger the higher the travel speed. (Supplementary Note 4) A work machine control system according to any one of (Supplementary Note 1) to (Supplementary Note 3), wherein the controller outputs the deceleration command so that the deceleration force becomes stronger as the distance becomes shorter. (Supplementary Note 5) A work machine control system according to any one of (Supplementary Note 1) to (Supplementary Note 4), wherein the controller recognizes, as the excavation target, an object whose height from the ground surface on which the work machine is traveling is equal to or greater than a height threshold, based on detection data from an external sensor that detects objects in front of the work machine. (Supplementary Note 6) A work machine control system according to (Supplementary Note 5), wherein the height threshold is the height from the ground surface to the centre of a bucket of a work implement carried by the work machine when the bottom of the bucket is in contact with the ground surface on which the work machine is traveling. (Supplementary Note 7) The control system for a work machine according to any one of (Supplementary Note 1) to (Supplementary Note 6), wherein the controller determines whether a work implement of the work machine is in an excavation posture for excavating the excavation target, and outputs the deceleration command when it is determined that the work implement is in an excavation posture and the distance is equal to or less than a distance threshold.(Supplementary Note 8) The work machine control system described in (Supplementary Note 7), wherein the controller determines whether the work machine is in an digging attitude based on detection data from a work machine attitude sensor that detects the attitude of the work machine. (Supplementary Note 9) The work machine control system described in (Supplementary Note 8), wherein the digging attitude includes an angle formed between the bottom of the bucket of the work machine and the ground on which the work machine is traveling being equal to or smaller than a first angle threshold. (Supplementary Note 10) The work machine control system described in (Supplementary Note 9), wherein the digging attitude includes the tip of the blade of the bucket contacting the ground. (Supplementary Note 11) The work machine comprises: a body having a front frame and a rear frame connected to the front frame via an articulation mechanism; a work implement attached to the front frame; an external sensor disposed on the rear frame to detect objects in front of the work machine; and an articulation angle sensor to detect the articulation angle of the body, wherein the controller recognizes, based on detection data from the external sensor, an object whose height from the ground on which the work machine is traveling is equal to or greater than a height threshold, as the excavation target; determines whether the articulation angle of the body is equal to or less than a second angle threshold; and outputs the deceleration command when it is determined that the articulation angle is equal to or less than the second angle threshold. (Supplementary Note 12) The work machine comprises: a body having a front frame and a rear frame connected to the front frame via an articulation mechanism; a work implement attached to the front end of the front frame; an external sensor disposed on the rear frame to detect objects in front of the work machine; and an articulation angle sensor to detect the articulation angle of the body; and the controller recognizes, based on detection data from the external sensor, that an object whose height from the ground on which the work machine is traveling is equal to or greater than a height threshold, as the excavation target, and determines, based on detection data from the articulation angle sensor, whether the work machine is moving forward toward the excavation target. A work machine control system as set forth in any one of (Supplementary Note 1) to (Supplementary Note 11).(Supplementary Note 13) A work machine control system as set forth in any one of (Supplementary Note 1) to (Supplementary Note 12), wherein the work machine has a vehicle body, a work implement attached to the vehicle body, and an external sensor that is disposed on the vehicle body and detects objects in front of the work machine, the detection area of ​​the external sensor being set only on a detection line that coincides with a track line of the vehicle body. (Supplementary Note 14) A work machine control system as set forth in any one of (Supplementary Note 1) to (Supplementary Note 12), wherein the work machine has a vehicle body, a work implement attached to the vehicle body and having a bucket, and an external sensor that is disposed on the vehicle body and detects objects in front of the work machine, the detection area of ​​the external sensor being set on each of a plurality of detection lines that are parallel to the track line of the vehicle body and intersect the bucket. (Supplementary Note 15) A work machine equipped with the work machine control system as set forth in any one of (Supplementary Note 1) to (Supplementary Note 14). (Supplementary Note 16) A work machine remote control system comprising: an operating device arranged outside the work machine; and the work machine control system according to any one of (Supplementary Note 1) to (Supplementary Note 14). (Supplementary Note 17) A work machine control method, in which a controller executes the following: recognizing the distance from the work machine to an excavation target; determining whether the work machine is traveling at a travel speed equal to or greater than a first speed threshold; determining whether the work machine is moving forward towards the excavation target; and outputting a deceleration command to reduce the travel speed of the work machine when it is determined that the work machine is traveling at a travel speed equal to or greater than the first speed threshold, it is determined that the work machine is moving forward towards the excavation target, and it is determined that the distance is equal to or less than the distance threshold.

[0109] REFERENCE SIGNS LIST 1...work machine, 2...body, 2F...front frame, 2R...rear frame, 3...articulation mechanism, 4...cab, 5...wheels, 5F...front wheels, 5R...rear wheels, 6...work implement, 7...operation device, 7A...traveling system operation device, 7B...work implement operation device, 8...display device, 9...remote controller, 10...operator seat, 11...articulation cylinder, 12...boom, 13...bucket, 13A...blade tip, 13B...opening, 13C...bottom, 14...bell crank, 15...ba 1. A bucket link, 16...bracket, 17...bracket, 18...boom cylinder, 19...bucket cylinder, 20...engine, 21...power take-off, 22...power transmission device, 23...brake device, 24A...steering pump, 24B...work implement pump, 25...external sensor, 26...vehicle speed sensor, 27...articulate angle sensor, 28...work implement attitude sensor, 28A...boom angle sensor, 28B...bucket angle sensor, 29...camera, 30...on-vehicle controller, 31...processor, 32...main memory, 33...storage, 34...input / output interface, 35...communication interface, 37...steering control valve, 38...boom control valve, 39...bucket control valve, 71...accelerator pedal, 72...brake pedal, 73...steering wheel, 74...forward / reverse switch lever, 75...boom lever, 76...bucket lever, 100...control system, 101...sensor data acquisition unit, 102...operation signal acquisition unit, 10 3...target recognition unit, 104...posture determination unit, 105...travel determination unit, 106...travel control unit, 107...work machine control unit, 108...transmission unit, 200...remote operation system, 201...work site, 202...remote operation room, 203...communication system, 300...excavation target, 400...object, 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.

Claims

1. A control system for a work machine comprising a controller, wherein the controller recognizes the distance from a work machine to an excavation target, determines whether the work machine is traveling at a speed equal to or greater than a first speed threshold, and determines whether the work machine is moving forward toward the excavation target, and outputs a deceleration command to reduce the travel speed of the work machine when it is determined that the work machine is traveling at a speed equal to or greater than the first speed threshold, that the work machine is moving forward toward the excavation target, and that the distance is equal to or less than the distance threshold.

2. A work machine control system according to claim 1, wherein the controller stops outputting the deceleration command after the travel speed of the work machine drops below a second speed threshold that is lower than the first speed threshold due to the output of the deceleration command.

3. A control system for a work machine according to claim 1, wherein the controller outputs the deceleration command such that the deceleration force increases as the traveling speed increases.

4. A work machine control system according to claim 1, wherein the controller outputs the deceleration command such that the shorter the distance, the stronger the deceleration force.

5. A work machine control system as described in claim 1, wherein the controller recognizes an object whose height above the ground on which the work machine is traveling is equal to or greater than a height threshold as the excavation target based on detection data from an external sensor that detects objects in front of the work machine.

6. A work machine control system according to claim 5, wherein the height threshold is the height from the ground to the center of the bucket of a work implement carried by the work machine when the bottom of the bucket is in contact with the ground on which the work machine is traveling.

7. A control system for a work machine as described in claim 1, wherein the controller determines whether a work implement of the work machine is in an excavation posture for excavating the excavation target, and outputs the deceleration command when it is determined that the work implement is in an excavation posture and the distance is equal to or less than a distance threshold.

8. A work machine control system according to claim 7, wherein the controller determines whether the work machine is in an excavation attitude based on detection data from a work machine attitude sensor that detects the attitude of the work machine.

9. A work machine control system according to claim 8, wherein the digging posture includes an angle formed between the bottom surface of the bucket of the work machine and the ground on which the work machine is traveling being equal to or smaller than a first angle threshold.

10. The work machine control system according to claim 9, wherein the digging position includes a blade tip of the bucket contacting the ground.

11. A control system for a work machine as described in claim 10, wherein the work machine comprises: a body having a front frame and a rear frame connected to the front frame via an articulation mechanism; a work implement attached to the front frame; an external sensor disposed on the rear frame to detect objects in front of the work machine; and an articulation angle sensor to detect the articulation angle of the body; and the controller recognizes, based on the detection data of the external sensor, an object whose height from the ground on which the work machine is traveling is equal to or greater than a height threshold as the excavation target, determines whether the articulation angle of the body is equal to or less than a second angle threshold, and outputs the deceleration command when it is determined that the articulation angle is equal to or less than the second angle threshold.

12. A control system for a work machine as described in claim 1, wherein the work machine comprises: a body having a front frame and a rear frame connected to the front frame via an articulation mechanism; a work implement attached to the front end of the front frame; an external sensor disposed on the rear frame for detecting objects in front of the work machine; and an articulation angle sensor for detecting the articulation angle of the body; and the controller recognizes, based on the detection data of the external sensor, an object whose height from the ground on which the work machine is traveling is equal to or greater than a height threshold, as the excavation target, and determines, based on the detection data of the articulation angle sensor, whether the work machine is moving forward toward the excavation target.

13. A work machine control system as set forth in claim 1, wherein the work machine has a vehicle body, a work implement attached to the vehicle body, and an external sensor disposed on the vehicle body for detecting objects ahead of the work machine, the detection area of ​​the external sensor being set only on a detection line coinciding with the track line of the vehicle body.

14. A work machine control system according to claim 1, wherein the work machine comprises: a vehicle body; a work implement attached to the vehicle body and having a bucket; and an external sensor disposed on the vehicle body for detecting objects ahead of the work machine, the detection areas of the external sensors being set on each of a plurality of detection lines that are parallel to the track line of the vehicle body and intersect with the bucket.

15. A work machine comprising the work machine control system according to claim 1.

16. A remote control system for a work machine, comprising: an operating device disposed outside the work machine; and the work machine control system according to claim 1.

17. A control method for a work machine, in which a controller executes the following steps: recognizes the distance from the work machine to an excavation target; determines whether the work machine is traveling at a travel speed equal to or greater than a first speed threshold; determines whether the work machine is moving forward toward the excavation target; and outputs a deceleration command to reduce the travel speed of the work machine when it is determined that the work machine is traveling at a travel speed equal to or greater than the first speed threshold, that the work machine is moving forward toward the excavation target, and that the distance is equal to or less than the distance threshold.

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