Work machine target operation setting system

Abstract

A work machine target operation setting system (1) comprises a machine body (10a), an inclination detection device (21b), an attachment (15), and a controller (30). The controller (30) determines, on the basis of the inclination of the machine body (10a) detected by the inclination detection device (21b), whether the machine body (10a) is in a raised state in which the machine body (10a) is raised relative to a ground surface. When a target operation change condition set by the controller (30) is satisfied, the controller (30) performs a target operation change process. The target operation change process involves changing a target operation so as to reduce the inclination of the machine body (10a). The target operation change condition includes that the machine body (10a) is in the raised state.

Description

Work machine target operation setting system

[0001] The present invention relates to a work machine target motion setting system that sets a target motion of a work machine.

[0002] For example, Patent Document 1 describes a technique for creating an excavation plan (target operation) for a bucket based on soil type and topographical information.

[0003] When the work machine performs work in accordance with the target operation, the machine body may enter a floating state in which the bottom surface of the machine body is lifted off the contact surface of the machine body.

[0004] Japanese Patent Application Laid-Open No. 2021-188362

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a work machine target motion setting system that can reduce the degree to which the machine body floats when the work machine operates in accordance with a target motion.

[0006] The work machine target motion setting system includes a machine body, a tilt detection device, an attachment, and a controller. The tilt detection device detects the tilt of the machine body. The attachment is attached to the machine body. The attachment has a bucket for performing excavation work. The controller sets a target motion for the excavation motion of the bucket. The controller determines whether the machine body is in a floating state relative to the ground surface based on the tilt of the machine body detected by the tilt detection device. The controller performs a target motion change process when a target motion change condition set in the controller is satisfied. The target motion change process is a process of changing the target motion so that the tilt of the machine body becomes smaller. The target motion change condition includes the machine body being in a floating state.

[0007] The above-described work machine target motion setting system can reduce the degree of floating of the machine body when the work machine operates in accordance with the target motion.

[0008] 8 is a side view of a work machine 10 of the work machine target movement setting system 1. FIG. 9 is a block diagram of the work machine target movement setting system 1. FIG. 1 is a side view of the work machine 10 when the machine main body 10a shown in FIG. 1 is in a front-floating state. FIG. 3 is a side view of the target route P and other changes made when the machine main body 10a is in a front-floating state. FIG. 1 is a side view of the work machine 10 when the machine main body 10a shown in FIG. 1 is in a rear-floating state. FIG. 5 is a side view of the target route P and other changes made when the machine main body 10a is in a rear-floating state. FIG. 1 is a side view of the work machine 10 when the machine main body 10a shown in FIG. 1 is in a front-floating state and the bucket 15c cannot be positioned at the excavation start target bucket ground angle θs. FIG. 9 is a side view of the target route P and other changes made when the target excavation start position Ps shown in FIG. 7 is changed to X1 forward of the position shown in FIG. 7. FIG. 10 is a flowchart showing processing relating to the excavation start target bucket ground angle θs and the target excavation start position Ps shown in FIGS. 7 and 8. 16 is a diagram showing the bucket height H15c and the like stored when the machine main body 10a shown in FIG. 1 is in a rear-floating state. It is a graph showing the relationship between the inclination of the machine main body 10a shown in FIG. 1 and the amount of change in the target operation by the controller 30 shown in FIG. 2. It is a graph showing the relationship between the working time of the work machine 10 shown in FIG. 1 and the accumulated amount of change in the target operation by the controller 30 shown in FIG. 2. It is a flowchart showing the processing of limiting the accumulated change amount using the accumulated change amount limit value shown in FIG. 11. It is a side view of the work machine 10 when the operating direction of the attachment 15 is changed when the machine main body 10a shown in FIG. 1 is in a rear-floating state. It is a side view of the work machine 10 when the element to be operated of the attachment 15 shown in FIG. 1 is changed. It is a side view of the work machine 10 when the operation of the bucket 15c shown in FIG. 1 is changed to a discharge operation. It is a flowchart showing the processing of the controller 30 shown in FIG. 2. It is a flowchart showing the processing (S50) of "handling the front-floating state in the current excavation operation" shown in FIG. 17. It is a flowchart showing the processing (S70) of "handling the rear-floating state in the current excavation operation" shown in FIG.

[0009] A work machine target movement setting system 1 will be described with reference to FIGS.

[0010] 1, the work machine target movement setting system 1 is a system that sets a target movement of a work machine 10. The work machine target movement setting system 1 includes the work machine 10 and a controller 30.

[0011] The work machine 10 is a machine that performs work. For example, the work machine 10 is a construction machine that performs construction work. For example, the work machine 10 is a shovel. The work machine 10 may be configured to be operable by automatic control. The automatic control may be automatic driving or semi-automatic driving (machine control, described below). The work machine 10 may also operate without the use of automatic control. The work machine 10 may be operated by an operator on board the work machine 10, or may be remotely operated by an operator at a location remote from the work machine 10. The following will mainly describe a case where the work machine 10 is a shovel. The work machine 10 comprises a machine main body 10a, an attachment 15, multiple actuators 17, a drive control unit 19 (see FIG. 2 ), and multiple attitude sensors 21.

[0012] The machine body 10a is the main body of the work machine 10. The machine body 10a includes a lower traveling body 11 and an upper rotating body 13. The lower traveling body 11 is capable of traveling on a traveling surface (such as the ground). The lower traveling body 11 may include crawlers or wheels. The upper rotating body 13 is rotatably mounted on the lower traveling body 11. The direction in which the rotation axis of the upper rotating body 13 relative to the lower traveling body 11 extends is defined as the up-down direction Z. In the up-down direction Z, the direction from the lower traveling body 11 toward the upper rotating body 13 is defined as the upward direction Z1, and the side opposite to the upward direction Z1 is defined as the downward direction Z2. The direction in which the rotation axis of the attachment 15 (more specifically, the boom 15a) relative to the machine body 10a extends is defined as the machine body lateral direction. The direction intersecting (e.g., perpendicular to) both the up-down direction Z and the machine body lateral direction is defined as the fore-aft direction X. In the front-to-rear direction X, the direction in which the attachment 15 protrudes relative to the upper revolving body 13 is referred to as the front X1, and the side opposite to the front X1 is referred to as the rear X2. When the machine body 10a is placed on a horizontal plane, the up-down direction Z is the vertical direction.

[0013] The attachment 15 is a part that performs work. The attachment 15 is attached to the machine body 10a. For example, the attachment 15 includes a boom 15a, an arm 15b, and a bucket 15c. The boom 15a is attached to the upper rotating body 13 so as to be able to rise and fall relative to the upper rotating body 13 around a rotation axis at the base end of the boom 15a. The arm 15b is attached to the boom 15a so as to be able to rotate relative to the boom 15a around a rotation axis at the base end of the arm 15b.

[0014] The bucket 15c performs excavation work, which is work to excavate a work object. The work object is an object that is the target of work by the work machine 10 (the target of work by the bucket 15c). The work object may be, for example, soil, granules, chips, powder, etc. Specifically, the work object is earth and sand, etc. The bucket 15c is a tip attachment provided at the tip of the attachment 15. The bucket 15c is attached to the arm 15b so that it can rotate relative to the arm 15b around a rotation axis at the base end of the bucket 15c. The direction of rotation of the bucket 15c backward X2 relative to the arm 15b is defined as the excavation direction R1. The direction of rotation of the bucket 15c forward X1 relative to the arm 15b is defined as the discharge direction R2. The angle of the bucket 15c with respect to a reference direction is called the ground angle of the bucket 15c. The "reference direction" may be a direction along the surface of the work object to be excavated by the bucket 15c, or may be a horizontal direction. The surface of the work object is an excavation surface, for example, the ground. The ground angle of the bucket 15c is, for example, the angle of a specific surface of the bucket 15c (for example, the bucket opening surface 15c1) with respect to the reference direction. The target value (target angle) of the ground angle of the bucket 15c is the target bucket ground angle θ, which will be described later. The bucket 15c includes the bucket opening surface 15c1, a bucket tip back surface 15c3, and a bucket tip portion 15c5.

[0015] The bucket opening surface 15c1 is a virtual surface that extends along the opening of the bucket 15c. Specifically, for example, the bucket opening surface 15c1 may be a virtual plane that includes a linear left edge and a linear right edge among the multiple edges that define the opening of the bucket 15c. The bucket tip back surface 15c3 is the outer surface of the bucket 15c that extends from the bucket tip 15c5 toward the bottom of the bucket 15c. The bucket tip back surface 15c3 is provided on the tip side portion of the bucket 15c (the portion farther from the connection to the arm 15b). When the bucket 15c is positioned so that the bucket opening surface 15c1 faces the upper rotating body 13, the bucket tip back surface 15c3 is located forward in the direction X1 from the bucket opening surface 15c1. The bucket tip back surface 15c3 is, for example, flat. The bucket tip 15c5 is the tip portion of the bucket 15c (the end farther from the connection to the arm 15b). The bucket tip portion 15c5 may have, for example, a plurality of claw-shaped members (bucket teeth).

[0016] The bucket 15c includes a bucket specific portion 15c7. The bucket specific portion 15c7 is a portion that is targeted to be positioned on a target path P (described later). A controller 30, described later, may control the operation of the work machine 10 in automatic control of the work machine 10 so that the bucket specific portion 15c7 is positioned on the target path P. In other words, the controller 30 may control the operation of the work machine 10 in automatic control of the work machine 10 so that the bucket specific portion 15c7 moves along the target path P. The bucket specific portion 15c7 may be, for example, the bucket tip portion 15c5. The bucket specific portion 15c7 may also be the base end portion of the bucket 15c (the portion connecting to the arm 15b).

[0017] The multiple actuators 17 are devices that move the work machine 10. The multiple actuators 17 may include hydraulic actuators that are driven by hydraulic pressure, or may include electric actuators that are driven by electricity. The multiple actuators 17 may include motors or may include extendable cylinders. The multiple actuators 17 include cylinders that move the attachment 15. Specifically, the multiple actuators 17 include a boom cylinder 17a, an arm cylinder 17b, and a bucket cylinder 17c. The boom cylinder 17a raises and lowers the boom 15a relative to the upper rotating body 13. The boom cylinder 17a, the arm cylinder 17b, and the bucket cylinder 17c are each, for example, a hydraulic cylinder that extends and retracts hydraulically. The arm cylinder 17b rotates the arm 15b relative to the boom 15a. The bucket cylinder 17c rotates the bucket 15c relative to the arm 15b.

[0018] The drive control unit 19 (see FIG. 2 ) controls the operation of the actuator 17. If the actuator 17 is hydraulic, the drive control unit 19 may include a hydraulic circuit that controls the hydraulic actuator 17. If the actuator 17 is electric, the drive control unit 19 may include an electric circuit that controls the electric actuator 17.

[0019] Specifically, if the actuators 17 are hydraulic, the drive control unit 19 may include a control valve. The control valve may include a plurality of directional control valves that respectively control the direction of hydraulic oil supplied to the plurality of actuators 17. Each of the plurality of directional control valves may include a spool and a pair of ports. Each directional control valve may be configured such that the spool is displaced in response to an operation command input to one of the pair of ports to adjust the direction and flow rate of hydraulic oil supplied to the actuator 17 connected to the directional control valve. This causes the actuator 17 to operate in response to the operation command. The operation command may be a command (current value) output by the controller 30. Furthermore, if a proportional valve is interposed between the controller 30 and the port of each directional control valve, the operation command may be a secondary pressure (pilot pressure) of the proportional valve. In this case, the proportional valve outputs a secondary pressure having a magnitude corresponding to the command (current value) output by the controller 30.

[0020] The multiple attitude sensors 21 detect the attitude of the work machine 10. Some or all of the attitude sensors 21 may be mounted on the work machine 10. Some or all of the attitude sensors 21 may be arranged outside the work machine 10 (for example, at the work site), and may not be components of the work machine 10. The multiple attitude sensors 21 include a reference position sensor 21a, an inclination detection device 21b, a rotation sensor 21c, a boom sensor 21d, an arm sensor 21e, and a tip attachment sensor 21f.

[0021] The reference position sensor 21a detects the position and orientation of a reference portion of the work machine 10 relative to the work site. The reference portion of the work machine 10 may be, for example, a specific portion of the upper rotating body 13, such as the mounting portion (boom foot) of the boom 15a to the upper rotating body 13, or the center of rotation of the upper rotating body 13 relative to the undercarriage 11. The reference position sensor 21a may perform detection using a positioning system using electromagnetic waves (light, radio waves, etc.). For example, the positioning system may be a satellite positioning system, such as a global navigation satellite system (GNSS), or a system using a (terrestrial) transmitter and receiver that does not use satellites. For example, the positioning system may use a total station. Note that in FIG. 1 , the reference position sensor 21a is designated by the symbol for the reference position sensor 21a to indicate the position of the GNSS antenna when the reference position sensor 21a performs detection using a positioning system using GNSS.

[0022] The tilt detection device 21b detects the tilt of the machine body 10a. The tilt detection device 21b detects the tilt of the machine body 10a relative to the horizontal direction. The tilt detection device 21b detects the tilt of the upper rotating body 13 relative to the horizontal direction. The tilt detection device 21b may be configured to detect, for example, the pitch angle of the machine body 10a relative to the horizontal direction. The pitch angle is the tilt angle of the central axis of the machine body 10a extending in the front-to-back direction X relative to the horizontal direction. The tilt detection device 21b can detect whether the machine body 10a is tilted upward at the front or rear. "Front-to-rear tilt" refers to a state in which the machine body 10a is tilted so that the central axis of the machine body 10a extending in the front-to-rear direction is positioned higher as it moves forward X1. "Rear-to-rear tilt" refers to a state in which the machine body 10a is tilted so that the central axis of the machine body 10a extending in the front-to-rear direction is positioned higher as it moves backward X2. The tilt detector 21b may be capable of detecting the roll angle of the machine body 10a, or may be capable of detecting the yaw angle of the machine body 10a.

[0023] The tilt detection device 21b may include, for example, a gyro sensor, an acceleration sensor, or an inertial measurement device. The tilt detection device 21b may detect the tilt of the machine body 10a based on image information detected by an imaging device. In this case, the imaging device is included in the tilt detection device 21b. Similarly, each of the reference position sensor 21a, the rotation sensor 21c, the boom sensor 21d, the arm sensor 21e, and the tip attachment sensor 21f may be configured to detect the posture of the detection target using image information detected by the imaging device. The tilt detection device 21b may detect the tilt of the machine body 10a based on image recognition of a two-dimensional image. The tilt detection device 21b may detect the tilt of the machine body 10a based on a three-dimensional image (distance image) having depth information. The tilt detection device 21b may detect the tilt of the machine body 10a based on a three-dimensional image and a two-dimensional image. The imaging device that detects the image may be a passive or active type. Specifically, the imaging device may include a camera (monocular camera) that detects two-dimensional information. The imaging device may include a stereo camera that detects three-dimensional information. The imaging device may detect three-dimensional information of an imaging target by irradiating the imaging target with waves such as electromagnetic waves and detecting the reflected waves. The imaging device may include a time-of-flight (TOF) sensor that detects distance based on the time from when the waves are emitted until the reflected waves return, or a sensor that detects distance based on the frequency of the reflected waves. The imaging device may include a device that detects three-dimensional information using light (e.g., laser light), such as a light detection and ranging (LiDAR) sensor. The imaging device may include a device that detects three-dimensional information using radio waves (e.g., millimeter-wave radar). The tilt detection device 21b may include only one imaging device or multiple imaging devices. In the tilt detection device 21b, only one type of imaging device (such as one system) may be used, or multiple types of imaging devices may be combined.

[0024] The rotation sensor 21c detects the rotation angle of the upper rotating body 13 relative to the lower traveling body 11. The rotation sensor 21c may include an angle sensor attached to the rotation axis or a rotation support part (such as a rotation bearing) of the upper rotating body 13 relative to the lower traveling body 11.

[0025] The boom sensor 21d detects the attitude of the boom 15a. The boom sensor 21d detects the angle (tilt angle or rotation angle) of the boom 15a with respect to the horizontal direction or the upper rotating body 13. The boom sensor 21d may include an angle sensor (e.g., a rotary encoder) attached to the rotation shaft or rotation support part of the boom 15a with respect to the upper rotating body 13. The boom sensor 21d may include a sensor that detects the tilt of the boom 15a with respect to the horizontal direction. The boom sensor 21d may include a stroke sensor that detects the stroke of the boom cylinder 17a.

[0026] The arm sensor 21e detects the posture of the arm 15b. The arm sensor 21e detects the angle of the arm 15b relative to the horizontal direction or the boom 15a. The arm sensor 21e may include an angle sensor attached to the rotation axis or rotation support part of the arm 15b relative to the boom 15a, a sensor that detects the inclination of the arm 15b relative to the horizontal direction, or a stroke sensor that detects the stroke of the arm cylinder 17b.

[0027] The tip attachment sensor 21f detects the attitude of the bucket 15c. In the example shown in FIG. 1 , the tip attachment sensor 21f is attached, for example, to a link member that connects the arm 15b, the bucket 15c, and the bucket cylinder 17c. The tip attachment sensor 21f detects the angle of the bucket 15c relative to the horizontal direction or the arm 15b. The tip attachment sensor 21f may include an angle sensor attached to the rotation shaft or rotation support part of the bucket 15c relative to the arm 15b, a sensor that detects the inclination of the bucket 15c relative to the horizontal direction, or a stroke sensor that detects the stroke of the bucket cylinder 17c.

[0028] The controller 30 is a computer that performs signal input / output, calculations (processing), information storage, etc. For example, the functions of the controller 30 shown in FIG. 2 are realized by the calculation unit 30a executing a program stored in the memory unit 30b of the controller 30. The controller 30 may be connected to other devices via wireless communication or wired communication. For example, detection results from multiple attitude sensors 21 are input to the controller 30. For example, the controller 30 (more specifically, the operation control unit 33) controls the operation of the work machine 10 (see FIG. 1). For example, the controller 30 outputs commands (signals) to operate the work machine 10 to the drive control unit 19. The controller 30 may be mounted on the work machine 10 or may be located external to the work machine 10. The controller 30 may be distributed across multiple parts (a distributed system may be configured). The controller 30 includes a calculation unit 30a that calculates (processes) information, and a memory unit 30b. Focusing on the functions of the controller 30 , the controller 30 includes a target motion setting unit 31 and a motion control unit 33 .

[0029] The memory unit 30b stores information. The memory unit 30b stores programs. For example, the memory unit 30b stores the state of inclination of the machine main body 10a determined by the controller 30 (specifically, the floating state, front floating state, and rear floating state, which will be described later). For example, as shown in FIG. 10 , the memory unit 30b stores the bucket height H15c (the floating state bucket height, which will be described later) when the machine main body 10a is in the floating state.

[0030] The target operation setting unit 31 sets a target operation of the work machine 10 (see FIG. 1). Details of the target operation will be described later.

[0031] The movement control unit 33 controls the movement of the work machine 10. The movement control unit 33 outputs commands to the drive control unit 19. The movement control unit 33 may output commands to the drive control unit 19 in response to an operation by the operator (for example, a lever operation). The movement control unit 33 may automatically control the work machine 10 so that the work machine 10 moves in accordance with a target movement. In this case, the movement control unit 33 automatically controls the movement of the work machine 10 based on the detection value of the attitude sensor 21.

[0032] 1 may be operated by an operator in the cab 13a, may be remotely operated by an operator from outside the work machine 10 (remote control device), or may be automatically driven by the controller 30. The work machine 10 is a machine that utilizes information and communication technology (ICT) (for example, ICT construction machinery).

[0033] For example, the work machine 10 may be operated by an operator while utilizing the functions of a machine guidance (MG) system. Specifically, a target operation is set in the controller 30. The controller 30 then provides the operator with guidance, such as the position where work should be done, so that the work machine 10 can operate (perform work) in accordance with the target operation. This guidance is output, for example, to an output device provided in the operator's cab 13a of the work machine 10 or an output device provided in a remote control device. The operator then operates the work machine 10 in accordance with the guidance. As a result, the work machine 10 operates in accordance with the target operation.

[0034] Furthermore, for example, the work machine 10 may be operated by a machine control system (MC). Specifically, a target movement is set in the controller 30. Then, the operator, for example, operates only a lever to operate some of the elements of the attachment 15 (e.g., the boom 15a). At this time, the controller 30 (movement control section 33) automatically controls the movement of elements not operated by the operator (e.g., the arm 15b and bucket 15c) so that the work machine 10 works in accordance with the target movement. In this control, the controller 30 controls the movement of the work machine 10 based on the target movement and the detection value of the attitude sensor 21. As a result, the work machine 10 operates in accordance with the target movement.

[0035] Furthermore, for example, the work machine 10 may operate by automatic driving. In this case, the controller 30 (operation control section 33) controls the operation of the work machine 10 so that the work machine 10 works automatically in accordance with a target operation. In this automatic driving, the controller 30 automatically controls the operation of the work machine 10 based on the target operation and the detection value of the attitude sensor 21. The following mainly describes the case where the work machine 10 operates by automatic control (machine control or automatic driving).

[0036] (Target Motion) A target motion of the work machine 10 is set in the controller 30 (more specifically, the target motion setting unit 31). The target motion is a target motion of the work machine 10. The target motion includes a target motion for the excavation motion of the bucket 15c. The target motion may also include a target motion of the work machine 10 other than the excavation motion. The target motion may also be set (manually) in response to an operation by the operator. The target motion may be automatically generated by the controller 30, or may be set in advance in the controller 30. The target motion may also be set in advance outside the controller 30, and input and set in the controller 30. The target motion includes a target path P and a target bucket ground angle θ.

[0037] The target path P is a target path for the bucket 15c. More specifically, the target path P is a target path for the bucket specific portion 15c7. The target path P includes multiple target points Pp. The target points Pp are information on the target positions of the bucket specific portion 15c7. Specifically, this "position information" may be three-dimensional position coordinates or two-dimensional position coordinates. The target path P is an ordered set of target points Pp. The target path P is information that includes information on the positions of each of the multiple target points Pp and information on the order of the multiple target points Pp. Time information may be added to the information on the target path P. Information obtained by adding time information to the information on the target path P is called a target trajectory. The "time information" is, for example, a time between two points. The time between two points is a target value for the movement time of the bucket specific portion 15c7 between two adjacent (sequential) target points Pp. The time between two points is the time it takes for the bucket specific part 15c7 to reach the next target point Pp from one target point Pp. The "time information" may be information on the time of day, etc. By adjusting the "time information," the target movement speed of the bucket 15c (specifically, the bucket specific part 15c7) is adjusted.

[0038] The coordinate system serving as a reference for representing the target path P may be set in any manner as long as it is a coordinate system from which the attitude of the work machine 10 can be derived. The origin (reference position) of this coordinate system may be set at the work site. The origin of this coordinate system may be set at a specific location on the work machine 10, for example, at a specific location on the upper rotating body 13. Specifically, for example, the origin of this coordinate system may be set at the attachment portion (boom foot) of the boom 15a to the upper rotating body 13, or at the center of rotation of the upper rotating body 13 relative to the undercarriage 11. The coordinate system may be a two-dimensional coordinate system, such as a two-dimensional Cartesian coordinate system including a coordinate axis in the fore-aft direction X and a coordinate axis in the up-down direction Z. The coordinate system may also be a three-dimensional coordinate system, such as a three-dimensional Cartesian coordinate system including a coordinate axis in the fore-aft direction X, a coordinate axis in the up-down direction Z, and a coordinate axis in a direction perpendicular to each of the fore-aft direction X and the up-down direction Z (for example, the lateral direction of the machine body). Furthermore, the coordinate system may include, for example, a coordinate axis in the front-to-rear direction X, a coordinate axis in the up-down direction Z, and a coordinate axis in the direction of rotation of the upper rotating structure 13 relative to the lower traveling structure 11. Furthermore, the coordinate system may include, for example, a coordinate axis for the bucket angle. This bucket angle may be the angle of the bucket 15c with respect to the horizontal direction, the angle with respect to the arm 15b, or the angle with respect to the upper rotating structure 13. Controller 30 (more specifically, operation control unit 33 (see FIG. 2 )) determines the attitude of work machine 10 so that bucket specific part 15c7 is positioned on target path P. For example, once the position of bucket specific part 15c7 and the bucket angle are determined, the attitudes of each of boom 15a and arm 15b are uniquely determined, and therefore controller 30 can derive the target attitudes of each of boom 15a and arm 15b using the position of bucket specific part 15c7 and the bucket angle.

[0039] The target path P includes a target path of the bucket specific portion 15c7 during the excavation operation of the bucket 15c. The target path P may also include a target path of the bucket specific portion 15c7 during an operation of the work machine 10 that is different from the excavation operation of the bucket 15c. The target path P for the excavation operation of the bucket 15c will be described below. Parameters of the target path P include a target excavation start position Ps, a target excavation end position Pe, a target horizontal excavation distance Lh, and a target excavation depth Ld.

[0040] The target excavation start position Ps is the target position at which the excavation operation of the bucket 15c (more specifically, one excavation operation (the same applies below)) starts. For example, the target excavation start position Ps is the target position at which the bucket 15c (e.g., the bucket tip 15c5) first comes into contact with the work object in one excavation operation. For example, the target excavation start position Ps may be represented by the coordinates of a single point (target excavation start coordinates) in the two-dimensional coordinate system or the three-dimensional coordinate system.

[0041] The target excavation end position Pe is a target position where the excavation operation of the bucket 15c ends. For example, the target excavation end position Pe is a target position where the bucket 15c moves away from the work object in one excavation operation. For example, the target excavation end position Pe may be represented by the coordinates of a single point (target excavation end coordinates) in the two-dimensional coordinate system or the three-dimensional coordinate system.

[0042] The target horizontal excavation distance Lh is a target value for the horizontal movement distance of the bucket 15c during the excavation operation of the bucket 15c. For example, in the example shown in Fig. 1, the target horizontal excavation distance Lh is a target value for the movement distance of the bucket specific portion 15c7 when the bucket 15c linearly excavates a work object in the horizontal direction. Furthermore, for example, the target horizontal excavation distance Lh may be a target value for the horizontal distance from the target excavation start position Ps to the target excavation end position Pe (not shown).

[0043] The target excavation depth Ld is a target value for the excavation depth (vertical excavation distance) of the bucket 15c during the excavation operation of the bucket 15c. For example, the target excavation depth Ld is a target value for the vertical distance from the height of the bucket tip 15c5 when the bucket tip 15c5 is positioned at the deepest position during one excavation operation to a certain reference height. This "reference height" may be, for example, the height of the bottom surface of the machine body 10a (of the undercarriage 11). This "reference height" may be, for example, the height of the surface of the work object at the target position where the bucket 15c is to perform the excavation operation (e.g., the target excavation start position Ps or the target excavation end position Pe) before the bucket 15c performs the excavation operation.

[0044] As described above, the target bucket ground angle θ is the target angle (target value) of the bucket 15c with respect to the ground. In the example shown in Fig. 1, the target bucket ground angle θ is the angle of the bucket opening plane 15c1 with respect to the horizontal direction.

[0045] The target bucket ground angle θs for starting excavation is the target bucket ground angle θ at the target excavation start position Ps. More specifically, the target bucket ground angle θs for starting excavation is the target bucket ground angle θ when the bucket specific portion 15c7 is positioned at the target excavation start position Ps.

[0046] (Floating state) As shown in Figures 3 and 5, the machine body 10a may become floating while the work machine 10 is working (for example, during excavation work, etc.). The floating state is a state in which the machine body 10a (more specifically, the undercarriage 11) is floating above the ground surface (vehicle body floating). The floating state includes a front floating state shown in Figure 3 and a rear floating state shown in Figure 5.

[0047] As shown in Figure 3, the front-floating state is a state in which the rear portion of the bottom of the machine body 10a is in contact with the ground surface, while the front portion of the bottom of the machine body 10a is floating above the ground surface. Examples of causes of the machine body 10a becoming in a front-floating state are as follows: At the start of or during an excavation operation, the work machine 10 attempts to move the bucket 15c downward Z2. At this time, the bucket 15c pushes the work object downward Z2 and receives an upward Z1 reaction force F from the work object. As a result, the front portion of the bottom of the machine body 10a becomes floating above the ground surface (i.e., a front-floating state). A front-floating state is likely to occur when the work object (e.g., the ground) being excavated by the bucket 15c is hard. Furthermore, a front-floating state is likely to occur when the bucket 15c is at a large ground angle (details will be described later).

[0048] As shown in Figure 5, the rear-floating state is a state in which the front portion of the bottom of the machine body 10a is in contact with the ground surface, while the rear portion of the bottom of the machine body 10a is floating above the ground surface. Examples of causes of the machine body 10a becoming rear-floating are as follows: During the latter half of an excavation operation, the work machine 10 attempts to move the bucket 15c upward Z1, i.e., to lift the bucket 15c, with the bucket 15c buried in the work object. At this time, the bucket 15c pushes the work object upward Z1 and receives a reaction force F downward Z2 from the work object. As a result, the rear portion of the bottom of the machine body 10a becomes floating above the ground surface (i.e., the rear-floating state). The rear-floating state is likely to occur when the work object (e.g., the ground) being excavated by the bucket 15c is hard. In addition, the rear floating state is likely to occur when there is a large amount of work object located above the bucket tip 15c5, for example, in the latter half of the target path P (for example, the part closer to the upper rotating body 13 than the center between the target excavation start position Ps and the target excavation end position Pe) (see Figure 10).

[0049] (Determination of Floating State) The controller 30 shown in Figures 1 and 2 determines whether the machine body 10a is in a floating state based on the inclination (tilt angle) of the machine body 10a. The inclination of the machine body 10a is detected by the inclination detection device 21b and acquired by the controller 30. A specific example of this determination is as follows. The controller 30 acquires an "initial inclination angle," which is the inclination angle (more specifically, pitch angle) of the machine body 10a detected by the inclination detection device 21b when the machine body 10a is not in a floating state (e.g., before work). The controller 30 acquires an "in-work inclination angle," which is the inclination angle (more specifically, pitch angle) of the machine body 10a detected by the inclination detection device 21b when the work machine 10 is performing work (e.g., excavation operation). The controller 30 then determines whether the machine body 10a is in a floating state based on the difference between the inclination angle during work and the initial inclination angle (amount of change in the inclination angle). Specifically, the controller 30 determines whether the machine body 10a is in a floating state based on whether the amount of change in the tilt angle exceeds a predetermined threshold (tilt threshold). The controller 30 determines whether the machine body 10a is in a front floating state or a rear floating state depending on whether the amount of change in the tilt angle is a positive value or a negative value.

[0050] (Target Motion Changing Process) When the machine body 10a is in a floating state, the controller 30 may perform a target motion changing process. The target motion changing process is outlined below.

[0051] The controller 30 performs a target motion change process when a target motion change condition (described later) is satisfied. The target motion change process is a process of changing the target motion so as to reduce the inclination of the machine body 10a. Specifically, the target motion change process may include, for example, a process of changing the target path P, or a process of changing the target bucket ground angle θs at the start of excavation. "The inclination of the machine body 10a becomes smaller" may mean that the inclination of the machine body 10a (the inclination angle during work) detected by the inclination detection device 21b becomes smaller, or may mean that the difference between the inclination angle during work and the initial inclination angle (the amount of change in the inclination angle) becomes smaller. In other words, "the inclination of the machine body 10a becomes smaller" means that the degree of floating of the machine body 10a is reduced.

[0052] The target motion change condition is a condition for the controller 30 to determine whether to perform the target motion change process. The target motion change condition is set in advance in the controller 30. The target motion change condition is set before the target motion change process is performed in the controller 30. The target motion change condition includes at least the machine body 10a being in a floating state. The target motion change condition may include the machine body 10a being in a floating state and a condition other than the machine body 10a being in a floating state. For example, the target motion change condition may include a condition related to the floating state bucket height (described below), etc.

[0053] By performing the target motion change process, the degree of floating of the machine body 10a is reduced. As a result, vibrations and noise when the machine body 10a returns from a floating state to the ground are reduced, and the machine body 10a is prevented from tipping over. Furthermore, the controller 30 automatically changes the target motion to reduce the degree of floating of the machine body 10a. Therefore, the operator does not need to manually change the target motion.

[0054] The controller 30 can change the target motion in the target motion change process (hereinafter simply referred to as "changing the target motion") at various times and in various ways. As a change in the target motion, the controller 30 may change the target motion to reduce the degree of the front-floating state, or may change the target motion to reduce the degree of the rear-floating state. As a change in the target motion, the controller 30 may change the target motion for the excavation motion, or may change the target motion for a motion other than the excavation motion. As a change in the target motion for the excavation motion, the controller 30 may change the target motion during the current excavation motion, or may change the target motion for subsequent excavation operations. The change in the target motion for the excavation motion may include at least one of Examples A to E described below. Each example will be described in detail below. The "current excavation motion" refers to the motion of the bucket 15c performed in accordance with the target motion set for the current excavation motion. The "next excavation motion" refers to the motion of the bucket 15c performed in accordance with the target motion set for the next excavation operation.

[0055] (Timing of Changing the Target Motion) The controller 30 may change the target motion at various timings.

[0056] (Changing the target motion during the current excavation operation) If a target motion change condition is satisfied while the bucket 15c is performing the "current excavation operation," the controller 30 may change the target motion for the "current excavation operation." A specific example of this aspect is as follows. The controller 30 causes the bucket 15c to perform an excavation operation (the "current excavation operation") based on the target motion before the change. During this excavation operation, the machine main body 10a becomes floating. At this time, the controller 30 changes the target motion for this "current excavation operation." Then, starting midway through the "current excavation operation," the controller 30 causes the bucket 15c to perform an excavation operation based on the changed target motion.

[0057] (Changing the target motion during subsequent excavation operations) If a target motion change condition is satisfied while the bucket 15c is performing the "current excavation operation," the controller 30 may change the target motion for the "current excavation operation." The "current excavation operation" may be a single excavation operation from the next operation onward (for example, the next time), or multiple excavation operations from the next operation onward. A specific example of this aspect is as follows: The controller 30 causes the bucket 15c to perform an excavation operation (the "current excavation operation") based on the target motion before the change. During this excavation operation, the machine main body 10a becomes floating. At this time, the controller 30 changes the target motion for subsequent excavation operations. Then, the controller 30 causes the bucket 15c to perform an excavation operation based on the changed target motion in the subsequent excavation operations.

[0058] (Changing target motion at other times) The controller 30 may change a target motion other than the excavation motion of the bucket 15c when a target motion change condition is satisfied when the bucket 15c is not performing an excavation motion (for example, after the excavation motion is completed or before the excavation motion starts) (specific examples will be described later).

[0059] (Contents of Change in Target Motion) To change the target motion of the excavation motion, the controller 30 may change the target path P (Example A) (see FIGS. 4 and 6) or may change the target bucket ground angle θs for starting excavation (Example B) (see FIG. 4). To change the target motion of the excavation motion, the controller 30 may change the direction of motion (reverse motion) (Example C) (see FIG. 14), may limit the elements of the attachment 15 to be operated (Example D) (see FIG. 15), or may change to a discharge motion (Example E) (see FIG. 16).

[0060] (Example A: Changing the target path P) The controller 30 shown in FIG. 1 may change the target path P as a change in the target operation. This "changing the target path P" is a change in the target path P to reduce the inclination of the machine body 10a. Specifically, the change in the target path P is a change in the parameters of the target path P. As a change in the target path P, the controller 30 may change the target path P to reduce the degree of the front lift state (see FIG. 4), or may change the target path P to reduce the degree of the rear lift state (see FIG. 6).

[0061] (Example A1: Changing the target path P to reduce the degree of front-floating state) As shown in FIG. 3 , one cause of the machine body 10a becoming in a front-floating state is that the force with which the bucket 15c pushes the work object downward Z2 is too strong, causing the reaction force F in the upward Z1 direction that the bucket 15c receives from the work object to be too strong. Therefore, the controller 30 performs the following process when a "front-floating state handling condition" (an example of a target operation change condition) is satisfied, which includes the machine body 10a being in a front-floating state. In this case, as shown in FIG. 4 , the controller 30 changes the target path P so that the force with which the bucket 15c pushes the work object downward Z2 (downward) is reduced. Specifically, the controller 30 changes the target excavation depth Ld so that the force with which the bucket 15c pushes the work object downward Z2 is reduced. Specifically, the controller 30 shallows the target excavation depth Ld. This reduces the force with which the bucket 15c pushes the work object downward Z2. In FIG. 4, the target route P before the change is indicated by a two-dot chain line, and the target route P after the change is indicated by a solid line.

[0062] (Example A2: Changing the Target Path P to Reduce the Degree of Rear-Floating State) As shown in FIG. 5, one cause of the rear-floating state of the machine body 10a is that the force with which the bucket 15c lifts the work object upward Z1 is too great, resulting in an excessively large reaction force F that the bucket 15c receives from the work object. Therefore, the controller 30 performs the following processing when a "rear-floating state handling condition" (an example of a target operation change condition) is satisfied, including the machine body 10a being in the rear-floating state. In this case, as shown in FIG. 6, the controller 30 changes the target path P so as to reduce the force with which the bucket 15c pushes the work object upward Z1 (upward). Specifically, the controller 30 may change the target excavation depth Ld (Example A2-1), the target horizontal excavation distance Lh (Example A2-2), the target excavation end position Pe (Example A2-3), or a combination of these changes. This reduces the force with which the bucket 15c pushes the work object upward Z1.

[0063] (Example A2-1) The controller 30 may change the target excavation depth Ld when the post-floating state handling condition is satisfied. In this case, the controller 30 changes the target excavation depth Ld so as to reduce the amount of work object (e.g., soil volume) lifted by the bucket 15c. Specifically, the controller 30 makes the target excavation depth Ld shallower.

[0064] (Example A2-2) The controller 30 may change the target horizontal excavation distance Lh when the post-floating state handling condition is satisfied. In this case, the controller 30 changes the target horizontal excavation distance Lh so as to reduce the amount of work object (e.g., soil volume) lifted by the bucket 15c. Specifically, the controller 30 shortens the target horizontal excavation distance Lh.

[0065] (Example A2-3) When the rear-floating state handling condition is satisfied, the controller 30 may change the target excavation end position Pe. In this case, the controller 30 changes the target excavation end position Pe so as to reduce the amount of work object (e.g., soil volume) lifted by the bucket 15c. Specifically, the controller 30 changes the target excavation end position Pe to the forward X1.

[0066] The reason for changing the target excavation end position Pe to the forward X1 is as follows. The bucket 15c excavates a work object by moving backward X2 from the target excavation start position Ps. Therefore, a portion of the work object excavated by the bucket 15c moves backward X2 as the bucket 15c moves backward X2, which tends to increase the amount of work object accumulated immediately behind the bucket 15c (see FIG. 10 ). Therefore, when the bucket 15c attempts to lift a large amount of work object accumulated immediately behind the bucket 15c, the machine body 10a tends to enter a rear-floating state. Therefore, when the rear-floating state handling condition is satisfied, the controller 30 changes the target excavation end position Pe (the position where the bucket 15c scoops up the work object) to the forward X1. This reduces the amount of work object accumulated immediately behind the bucket 15c by the time the bucket 15c reaches the target excavation end position Pe. In other words, the amount of earth and sand (soil volume) lifted by the bucket 15c as the work object is reduced. Therefore, the degree of rear floating of the machine body 10a is reduced. Note that, as a result of changing the target excavation end position Pe to the forward X1, the target horizontal excavation distance Lh may be shortened. As a result of shortening the target horizontal excavation distance Lh, the amount of work object lifted by the bucket 15c may be reduced.

[0067] (Example B: Changing the target bucket ground angle θs for starting excavation) The controller 30 may change the target bucket ground angle θs for starting excavation as a change in the target operation. Here, as shown in FIG. 3 , one cause of the machine body 10a being in a front-floating state is that the ground angle of the bucket 15c at the target excavation start position Ps (target bucket ground angle θs for starting excavation) is too large. If the ground angle of the bucket 15c is too large at the target excavation start position Ps, the force with which the bucket tip back surface 15c3 pushes the work object downward Z2 increases when the bucket tip 15c5 is inserted (penetrated) into the work object. Therefore, the reaction force F (resistance) that the bucket 15c receives from the work object increases, making it more difficult for the bucket tip 15c5 to be inserted into the work object. As a result, the machine body 10a is in a front-floating state.

[0068] Therefore, as shown in FIG. 4 , when the front floating state handling condition is satisfied, the controller 30 changes the excavation start target bucket ground angle θs so as to reduce the force with which the bucket 15c pushes the work object downward Z2 (downward). In this case, the controller 30 changes the excavation start target bucket ground angle θs so as to reduce the reaction force F that the bucket 15c receives when the bucket tip 15c5 is inserted into the work object. Specifically, in the example shown in FIG. 4 , the controller 30 reduces the excavation start target bucket ground angle θs. In FIG. 4 , the excavation start target bucket ground angle θs and the bucket 15c before the change are indicated by two-dot chain lines, and the excavation start target bucket ground angle θs and the bucket 15c after the change are indicated by solid lines. When the front floating state handling condition is satisfied, the controller 30 may both change the target path P in example A1 above and change the excavation start target bucket ground angle θs. Depending on the definition of the target bucket ground angle θs for starting excavation, increasing the target bucket ground angle θs for starting excavation may reduce the force with which the bucket 15c pushes the work object downward Z2 (downward).

[0069] (Physical Restrictions on the Attitude of the Attachment 15) As shown in FIG. 7, if the target bucket ground angle θs for starting excavation cannot be changed to a smaller value due to the structure of the work machine 10, the controller 30 changes the target excavation start position Ps as shown in FIG. 8.

[0070] The reason for changing the target excavation start position Ps is as follows. As shown in FIG. 7 , the structure of the work machine 10 limits the range of possible attitudes of the attachment 15. Specifically, the structure of the work machine 10 limits the range of possible bucket rotation angle φ, which is the angle of the bucket 15c relative to the arm 15b. For example, the range of possible bucket rotation angle φ is limited to between the bucket cylinder 17c being in its most retracted state (or a state close to its most retracted state) and the bucket cylinder 17c being in its most extended state (or a state close to its most extended state). Therefore, if the bucket cylinder 17c is in its most retracted state or a state close to it when the front floating state handling condition is satisfied, the structure of the work machine 10 does not allow the ground angle of the bucket 15c to be further reduced, and therefore the excavation start target bucket ground angle θs cannot be changed to a smaller value. This is because the bucket cylinder 17c needs to be retracted to reduce the ground angle of the bucket 15c. Here, the bucket rotation angle φ when the bucket tip 15c5 is positioned at the target excavation start position Ps and the ground angle of the bucket 15c is adjusted to the excavation start target bucket ground angle θs is referred to as the "bucket rotation angle φ corresponding to the excavation start target bucket ground angle θs." For example, as shown in FIG. 7 , when the position at which the bucket 15c excavates the work object (i.e., the ground) is lower than the bottom surface of the machine body 10a, the bucket rotation angle φ corresponding to the excavation start target bucket ground angle θs is likely to be an angle that cannot be achieved due to the structure of the work machine 10. Therefore, when the ground angle of the bucket 15c cannot be further reduced due to the structure of the work machine 10, that is, when the excavation start target bucket ground angle θs cannot be changed to an even smaller value, the controller 30 changes the target excavation start position Ps. Specifically, as shown in FIG. 8 , the controller 30 changes the target excavation start position Ps forward X1.

[0071] The process of changing the target excavation start position Ps will be described with reference to the flowchart shown in Fig. 9. Each step (S11 to S15) will be described below with reference to Fig. 9. Note that the order of steps S11 to S15 can be changed in various ways.

[0072] In step S11, the controller 30 determines a changed target bucket ground angle θs for starting excavation when the machine body 10a is in a front floating state and the front floating state handling condition is satisfied, as shown in FIG.

[0073] In step S12, controller 30 calculates a candidate value for bucket rotation angle φ corresponding to the determined excavation start target bucket ground angle θs. This candidate value for bucket rotation angle φ is the bucket rotation angle φ when it is assumed that the ground angle of bucket 15c is adjusted to the determined excavation start target bucket ground angle θs without changing the target excavation start position Ps.

[0074] In step S13, controller 30 determines whether the calculated candidate value for bucket rotation angle φ is within the allowable bucket rotation angle range. The allowable bucket rotation angle range is an allowable range for bucket rotation angle φ, and is set in advance (before this determination) in controller 30. The allowable bucket rotation angle range is a range of bucket rotation angle φ that is structurally possible for work machine 10. Note that in FIG. 9 , the "allowable bucket rotation angle range" is simply referred to as the "allowable range." If the calculated candidate value for bucket rotation angle φ is within the allowable bucket rotation angle range (YES in step S13), controller 30 causes the process flow to proceed to step S14. If the calculated candidate value for bucket rotation angle φ is not within the allowable bucket rotation angle range (NO in step S13), controller 30 causes the process flow to proceed to step S15.

[0075] In step S14, controller 30 does not perform the process (step S15) of changing target excavation start position Ps shown in Fig. 7. In this case, controller 30 controls the operation of bucket 15c so that the ground angle of bucket 15c at target excavation start position Ps becomes excavation start target bucket ground angle θs in the next and subsequent excavation operations.

[0076] In step S15, controller 30 changes target excavation start position Ps to the forward direction X1 (the rear side as viewed from machine body 10a), as shown in FIG. 8. At this time, controller 30 changes target excavation start position Ps so that the ground angle of bucket 15c becomes the changed target bucket ground angle θs for starting excavation determined in step S11 and so that bucket rotation angle φ falls within the bucket rotation angle allowable range. Through this processing, controller 30 can set the ground angle of bucket 15c to the changed target bucket ground angle θs for starting excavation determined in step S11. As a result, the degree of front floating of machine body 10a (see FIG. 7) can be reduced.

[0077] (Amount of change in target motion) The controller 30 may change the amount of change in the target motion (the amount of change in the target motion in the target motion change process) depending on conditions. The controller 30 may change the amount of change in the target path P shown in FIG. 4 depending on conditions. The controller 30 may change the amount of change in the excavation start target bucket ground angle θs depending on conditions. For example, the controller 30 may change the amount of change in the target motion depending on the bucket height H15c (see FIG. 10) during excavation operation, or depending on the inclination of the machine body 10a. The controller 30 may integrate the amount of change in the target motion. Details of each example are as follows.

[0078] (Amount of Change According to Bucket Height H15c) As shown in FIG. 10 , the controller 30 may change the amount of change in the target motion according to the bucket height H15c when the bucket 15c is performing an excavation operation (the bucket height H15c during excavation operation). The bucket height H15c is the position of the bucket 15c in the height direction. For example, the bucket height H15c may be the distance in the height direction from a reference position of the machine body 10a (e.g., the base end of the boom 15a or the bottom surface of the undercarriage 11) to the bucket specific portion 15c7. The "height direction" may be the vertical direction or the up-down direction Z based on the machine body 10a. The controller 30 may change the amount of change in the target path P or the amount of change in the excavation start target bucket ground angle θs according to the bucket height H15c during excavation operation. Note that the controller 30 may change the amount of change in the target motion according to the height of a portion of the attachment 15 other than the bucket 15c during excavation operation (e.g., the height of the tip of the arm during excavation operation).

[0079] The reason for changing the amount of change in the target operation depending on the bucket height H15c during excavation is as follows. When the bucket height H15c is large (the excavation position is deep), the reaction force F (see FIGS. 3 and 5 ) acting on the bucket 15c is likely to be larger than when the bucket height H15c is small (the excavation position is shallow). For example, a work object that is deep below the surface (ground surface) of the work object before excavation is often harder than a work object that is shallower. Therefore, when the bucket 15c is inserted into the work object, the reaction force F (see FIG. 3 ) acting on the bucket 15c is likely to be larger when the bucket height H15c is large than when it is small. Furthermore, when the bucket 15c excavates by lifting the work object, the amount of work object (e.g., soil volume) lifted by the bucket 15c is greater when the bucket height H15c is large than when the bucket height H15c is small. Therefore, when the bucket 15c excavates to lift up a work object, the reaction force F (see FIG. 5) acting on the bucket 15c is likely to be larger when the bucket height H15c is large than when it is small.

[0080] In this way, when the bucket height H15c is large, the reaction force F (see FIGS. 3 and 5) acting on the bucket 15c is more likely to be large than when it is small, and the machine body 10a is more likely to be in a floating state. Therefore, when the bucket height H15c is large, it is more necessary to change the target operation than when it is small.

[0081] On the other hand, the reaction force F (see FIGS. 3 and 5) acting on the bucket 15c is more likely to be smaller when the bucket height H15c is small than when it is large. Therefore, there is less need to change the target operation when the bucket height H15c is small than when it is large. If the target operation is changed too much to reduce the inclination of the machine body 10a when the bucket height H15c is small, the amount of work object excavated by the bucket 15c will decrease, and the workability of the work machine 10 will deteriorate.

[0082] Therefore, controller 30 changes the amount of change in the target operation depending on bucket height H15c during excavation operation. A specific example of this processing is as follows: When bucket 15c is performing excavation work, machine body 10a becomes floating. At this time, controller 30 stores the "floating state bucket height." The "floating state bucket height" is the bucket height H15c when machine body 10a becomes floating.

[0083] After the machine body 10a enters a floating state and the "floating state bucket height" is stored in the controller 30, the bucket 15c performs an excavation operation at another position (an excavation position that is different in the forward / backward direction X or in the rotation direction from the excavation position when the machine body 10a entered a floating state). At that time, the bucket 15c may perform an excavation operation at a position higher than the floating state bucket height (or a height close to that height (same below)). When the bucket 15c performs an excavation operation at a position higher than the floating state bucket height, it is expected that the machine body 10a is less likely to enter a floating state than when the bucket 15c performs an excavation operation at a position equal to or lower than the floating state bucket height.

[0084] Therefore, the controller 30 limits changes to the target operation when the bucket 15c performs an excavation operation at a position above a "height threshold" based on the floating bucket height. The "height threshold" may be the same value as the floating bucket height. The height threshold may be a height different from the floating bucket height that is set based on the floating bucket height. The height threshold may be, for example, a height close to the floating bucket height. The height threshold may be, for example, a value obtained by adding or subtracting a predetermined value from the floating bucket height. The "position above" the height threshold may be a position vertically above the height threshold, or may be a position Z1 above the height threshold relative to the upper rotating body 13.

[0085] Controller 30 reduces the amount of change in the target motion when bucket 15c performs an excavation operation at a position above the height threshold compared to the amount of change in the target motion when bucket 15c performs an excavation operation at a height below the height threshold, i.e., limits the change in the target motion. Specifically, for example, controller 30 may change the target motion when bucket 15c performs an excavation operation at a height below the height threshold, but may not change the target motion when bucket 15c performs an excavation operation at a position above the height threshold. In other words, the above-mentioned "limitation" in the target motion change processing may include setting the amount of change in the target motion when bucket 15c performs an excavation operation at a position above the height threshold to zero.

[0086] By limiting the change in the target motion when bucket 15c performs an excavation operation above the height threshold, it is possible to stably ensure the excavation volume (e.g., soil volume) of the work object. Furthermore, the change in the target motion when bucket 15c performs an excavation operation below the height threshold is preferably larger than the change in the target motion when bucket 15c performs an excavation operation above the height threshold. In this case, the target motion is changed relatively larger so as to reduce the inclination of machine body 10a, thereby reducing the degree to which machine body 10a floats when bucket 15c performs an excavation operation below the height threshold.

[0087] (Amount of change according to the inclination of the machine body 10a) The controller 30 may change the amount of change in the target operation according to the inclination (amount of inclination, angle of inclination) of the machine body 10a detected by the inclination detection device 21b shown in Figure 1 (see Figure 11).

[0088] The reason for changing the amount of change in the target motion in accordance with the inclination of machine body 10a is as follows. As described above, if controller 30 changes the target motion in the target motion change process so as to reduce reaction force F (see FIGS. 3 and 5) acting on bucket 15c as shown in FIG. 4 or 6, the amount of excavation of the work object by bucket 15c may decrease. For example, if the amount of change in the target motion is too large, the amount of excavation of the work object by bucket 15c may decrease too much. On the other hand, if the amount of change in the target motion is too small, machine body 10a may again become floating. Therefore, controller 30 changes the amount of change in the target motion in accordance with the inclination of machine body 10a.

[0089] The controller 30 may change the amount of change in the target motion depending on the in-work tilt angle of the machine body 10a. Specifically, the controller 30 may change the amount of change in the target motion depending on, for example, the absolute value of the in-work tilt angle. The controller 30 may also change the amount of change in the target motion depending on the difference between the in-work tilt angle of the machine body 10a and the initial tilt angle (the relative value of the tilt angle, the amount of lift). The controller 30 may increase the amount of change in the target motion as the tilt angle increases. The controller 30 may change the amount of change in the target motion stepwise or continuously as the tilt of the machine body 10a increases (see FIG. 11). The relationship between the amount of change in the target motion and the tilt of the machine body 10a may include, for example, a portion represented by a linear function (i.e., a proportional relationship) (see FIG. 11).

[0090] (Accumulation of Change Amount of Target Motion) The controller 30 may change the target motion multiple times. In this case, the controller 30 may accumulate the change amount of the target motion (see FIG. 12).

[0091] A specific example of accumulating the change amount for the target motion (see FIG. 12 ) is as follows: When the machine body 10a is in a floating state and the target motion change condition is satisfied, the controller 30 changes the target motion. This change is referred to as the "initial change." The change amount for the target motion resulting from the initial change is referred to as the "initial change amount." The controller 30 causes the bucket 15c to perform an excavation operation based on the target motion for which the "initial change" has been made (the changed target motion). Then, when the bucket 15c performs an excavation operation based on the changed target motion, the machine body 10a may again become floating. In this case, the controller 30 further changes the target motion so that the inclination of the machine body 10a becomes smaller. This change in the target motion is referred to as the "additional change." The change amount for the target motion resulting from the additional change is referred to as the "additional change amount." The controller 30 may determine the additional change amount based on the bucket height H15c. The controller 30 may determine the additional change amount based on the inclination of the machine body 10a.

[0092] The controller 30 determines the sum of the initial change amount and the additional change amount as the integrated change amount. The controller 30 changes the target motion based on this integrated change amount. The controller 30 may make an additional change multiple times. When an additional change is made multiple times, the controller 30 determines the sum of the initial change amount and the integrated value of the additional change amount as the integrated change amount.

[0093] A further specific example of accumulating the change amount for the target operation is as follows. Here, a case where the target excavation depth Ld is changed as a change in the target operation will be described. When the bucket 15c is performing an excavation operation, the machine body 10a enters a floating state (first time). At this time, the controller 30 shallows the target excavation depth Ld for the next or current excavation operation by the initial change amount, as shown in FIG. 4 . The controller 30 also shallows the target excavation depth Ld for subsequent excavation operations by the initial change amount. When the bucket 15c performs an excavation operation at the target excavation depth Ld shallower by the initial change amount, the machine body 10a again enters a floating state (second time). At this time, the controller 30 shallows the target excavation depth Ld for the next or current excavation operation by the sum of the initial change amount and the additional change amount (accumulated change amount). If the machine body 10a enters a floating state from the third time onwards, the controller 30 further adds the additional change amount to the accumulated change amount (see FIG. 12 ). In this example, the change in the target operation is a change in the target excavation depth Ld, and the change in the target excavation depth Ld is accumulated. However, the change in the target operation may also be a change in other parameters, such as a change in the target horizontal excavation distance Lh, a change in the target excavation end position Pe, or a change in the target bucket ground angle θs for starting excavation, and in this case, the change in the other parameters may be accumulated.

[0094] (Limiting the Accumulated Change Amount) If the accumulated change amount becomes too large, the amount of excavation of the work object by the bucket 15c will decrease. Therefore, controller 30 limits the change of the target motion so that the accumulated change amount is equal to or less than the accumulated change amount limit value (see FIG. 12 ). The accumulated change amount limit value is set in advance in controller 30 (before limiting the change amount of the target motion). As a result of limiting the accumulated change amount to or less than the accumulated change amount limit value, the amount of excavation of the work object by the bucket 15c is ensured.

[0095] A specific example of limiting the integrated change amount will be described with reference to the flowchart shown in Fig. 13. Steps S21 to S24 will be described below with reference to Fig. 13.

[0096] In step S21, the controller 30 shown in FIG. 1 calculates a candidate value for the integrated change amount. Specifically, when the machine body 10a is in a floating state, the controller 30 calculates a candidate value for the "current change amount." This "current change amount" is the change amount of the target operation in the processing for the current excavation operation (the change amount of the target operation corresponding to the current floating state), and is the initial change amount or the additional change amount. The controller 30 then calculates the sum of the integrated change amount up to the previous time and the current change amount as the candidate value for the integrated change amount.

[0097] In step S22, the controller 30 determines whether the candidate value for the integrated change amount is equal to or greater than the integrated change amount limit value. The integrated change amount limit value is set in advance (before this determination) in the controller 30. If the candidate value for the integrated change amount is equal to or greater than the integrated change amount limit value (YES in step S22), the controller 30 causes the process flow to proceed to step S23. If the candidate value for the integrated change amount is less than the integrated change amount limit value (NO in step S22), the controller 30 sets the candidate value for the integrated change amount as the determined value for the integrated change amount, and causes the process flow to proceed to step S24.

[0098] In step S23, if the candidate value for the integrated change amount is equal to or greater than the integrated change amount limit value (YES in step S22), the controller 30 corrects (sets) the determined value of the integrated change amount to be equal to or less than the integrated change amount limit value (see FIG. 12 ). In this case, the controller 30 may set the determined value of the integrated change amount to a value equal to or less than the integrated change amount limit value. Next, the controller 30 causes the process flow to proceed to step S24.

[0099] In step S24, the controller 30 stores the determined value of the integrated change amount, and then changes the target motion based on the determined value of the integrated change amount.

[0100] (Example C: Changing the direction of movement (reverse movement)) As shown in Figure 14, the controller 30 may change the direction of movement of the attachment 15 as a change in the target movement. Specifically, the controller 30 may change the target movement so that a reverse movement of the target path P is performed when a reverse movement execution condition (an example of a target movement change condition) described below is satisfied. In Figure 14, the work machine 10 before the reverse movement is performed is shown by a two-dot chain line, and the work machine 10 after the reverse movement is performed is shown by a solid line.

[0101] The reason for changing the target motion to change the motion direction of the attachment 15 is as follows. One of the reasons why the machine main body 10a becomes floating is that a reaction force F (see FIGS. 3 and 5 ) acts from the work object on the bucket 15c when the bucket 15c performs an excavation motion along the target path P. Therefore, the controller 30 changes the motion direction of the attachment 15. Specifically, the controller 30 changes the target motion so that a motion reverse to the target path P is performed. The "reverse motion" refers to moving (operating) the attachment 15 in a direction opposite (returning direction) to the direction of movement of the attachment 15 in the excavation motion along the target path P. In the reverse motion, the controller 30 moves (operates) the bucket 15c in a direction opposite (returning direction) to the direction of movement of the bucket 15c in the excavation motion along the target path P. In the reverse motion, the controller 30 may move the bucket 15c so as to trace the past trajectory of the bucket 15c in the excavation motion along the target path P. In addition, in the reverse operation, the controller 30 may move the bucket 15c in a direction roughly opposite to the direction of movement of the bucket 15c during the excavation operation along the target path P.

[0102] In the example shown in FIG. 1 , in a normal excavation operation, the bucket 15c performs, for example, a digging operation, a horizontal excavation operation, and a lifting operation. In the digging operation, the bucket 15c digs down the work object in the downward Z2 and backward X2 direction. In the horizontal excavation operation, the bucket 15c digs up the work object in the backward X2 direction. In the lifting operation, the bucket 15c lifts (digs up) the work object while excavating it in the upward Z1 and backward X2 direction. If the normal excavation operation is such an operation, in the reverse operation of the lifting operation, the bucket 15c moves downward Z2 and forward X1. In the reverse operation of the horizontal excavation operation, the bucket 15c moves forward X1. In the reverse operation of the digging operation, the bucket 15c moves forward X1 and upward Z1. Note that while FIG. 14 illustrates a case where the reverse operation is performed when the machine body 10a is in a front-floating state, the reverse operation may also be performed when the machine body 10a is in a rear-floating state.

[0103] (Reverse Action Execution Condition) As described above, the controller 30 may change the target action so that a reverse action of the target path P is performed when a reverse action execution condition (an example of a target action change condition) is satisfied. The reverse action execution condition can be set in various ways. The reverse action execution condition includes at least the mechanical body 10a being in a floating state. The reverse action execution condition may include the mechanical body 10a being in a floating state and the inclination of the mechanical body 10a detected by the inclination detection device 21b being a specific inclination state (a specific state other than being in a floating state). The "specific inclination state" is set in advance in the controller 30 (before determining whether the reverse action execution condition is satisfied). For example, the "specific inclination state" may be a state in which the degree of inclination of the mechanical body 10a is a specific magnitude. For example, the "specific inclination state" may be a state in which the degree of inclination of the mechanical body 10a exceeds a predetermined threshold, a reverse action execution inclination threshold. The "specific tilt state" may be a state in which the degree of tilt of the machine body 10a is increasing, i.e., a state in which the tilt of the machine body 10a is worsening. Note that the reverse operation execution condition may include a condition different from the above-mentioned condition.

[0104] 15 , when a motion element restriction condition (an example of a target motion change condition) described later is satisfied, the controller 30 may restrict the elements of the attachment 15 to be operated as a change to the target motion. The controller 30 may change the target motion so as to reduce the tilt of the machine body 10a by restricting the elements of the attachment 15 to be operated.

[0105] The reason for changing the target motion to limit the elements of the attachment 15 that are operated is as follows. For example, when all of the elements that make up the attachment 15 (the boom 15a, the arm 15b, and the bucket 15c) perform an excavation operation, the reaction force F (see FIGS. 3 and 5) acting from the work object on the bucket 15c becomes large, which may cause the machine body 10a to become floating. In this case, if only some of the elements that make up the attachment 15 (for example, only the bucket 15c) are made to perform the excavation operation, the reaction force F acting from the work object on the bucket 15c is likely to become small, and the degree to which the machine body 10a is floating is likely to be reduced.

[0106] Therefore, the controller 30 limits the elements of the attachment 15 that are to perform the excavation operation to only some of the elements of the attachment 15. Specifically, the controller 30 limits the element of the attachment 15 that is to perform the excavation operation to only the bucket 15c. More specifically, the target motion before the change includes performing the excavation operation of the bucket 15c and elements other than the bucket 15c (one or both of the boom 15a and the arm 15b). The controller 30 then changes the target motion after the change so that the target motion includes performing the excavation operation of only the bucket 15c, of the multiple elements that make up the attachment 15. Specifically, the controller 30 changes the target motion so that the target motion after the change includes stopping the boom 15a and the arm 15b while rotating the bucket 15c in the excavation direction R1 relative to the arm 15b. By having controller 30 limit the elements of attachment 15 that perform the excavation operation to only a portion of attachment 15 (for example, only bucket 15c), the reaction force F (see FIGS. 3 and 5) acting from the work object to bucket 15c tends to be smaller, which tends to eliminate the floating state of machine body 10a.

[0107] (Motion Element Restriction Condition) As described above, when a motion element restriction condition (an example of a target motion change condition) is satisfied, the controller 30 may restrict the elements of the attachment 15 to be operated. The motion element restriction condition can be set in various ways. The motion element restriction condition includes the mechanical body 10a being in a floating state (front-floating state or rear-floating state). For example, the motion element restriction condition may include the mechanical body 10a being in a floating state and the inclination of the mechanical body 10a detected by the inclination detection device 21b being in a specific inclination state (a specific state other than being in a floating state). This "specific inclination state" is set in advance in the controller 30 (before determining whether the motion element restriction condition is satisfied). This "specific inclination state" may be a state in which the degree of inclination of the mechanical body 10a is a specific magnitude. The above-mentioned "specific inclination state" may be a state in which the degree of inclination of the mechanical body 10a exceeds a predetermined threshold.

[0108] (Example E: Change to Discharge Operation) As shown in Fig. 16, the controller 30 may change the target operation to cause the bucket 15c to perform the discharge operation when a discharge condition (described later) is satisfied. The discharge operation may include, for example, an operation for adjusting the amount of soil in the bucket 15c. In particular, the controller 30 may change the target operation to cause the bucket 15c to perform the discharge operation when a discharge condition is satisfied while the bucket 15c is not performing the discharge operation.

[0109] The reason for changing the target operation to cause the bucket 15c to perform a discharge operation is as follows: When the work machine 10 is not performing an excavation operation, if the amount of work object in the bucket 15c is too large, the machine main body 10a may enter a rear-floating state. The above-mentioned "when the work machine 10 is not performing an excavation operation" refers, for example, to after the excavation operation is completed and before the bucket 15c discharges the work object. The above-mentioned "when the work machine 10 is not performing an excavation operation" refers, for example, to when the bucket 15c is moving (lifting) the work object upward Z1. Therefore, when the discharge condition is satisfied, the controller 30 changes the target operation to cause the bucket 15c to perform a discharge operation.

[0110] The "discharge operation" described above is an operation for discharging at least a portion of the work object in the bucket 15c from the bucket 15c. Specifically, the discharge operation is an operation that includes rotating the bucket 15c in the discharge direction R2. When the controller 30 causes the bucket 15c to perform the discharge operation, the amount of work object (e.g., the amount of soil) in the bucket 15c decreases. As a result, the rear floating state of the machine main body 10a is resolved. In this discharge operation, it is preferable that the work object in the bucket 15c is discharged from the bucket 15c until the rear floating state of the machine main body 10a is resolved. This discharge operation may be terminated with the work object remaining in the bucket 15c.

[0111] When causing the bucket 15c to perform the discharge operation, the controller 30 may operate one or both of the boom 15a and the arm 15b. For example, when causing the bucket 15c to perform the discharge operation, the controller 30 may move the boom 15a in a direction such that the tip of the boom 15a moves upward Z1, that is, the controller 30 may cause the boom 15a to perform a boom-raising operation. The boom-raising operation is a movement of the boom 15a such that the tip of the boom 15a moves away from the ground.

[0112] (Dumping Condition) As described above, the controller 30 may cause the bucket 15c to perform a dumping operation when a dumping condition (an example of a target operation change condition) is satisfied. The dumping condition can be set in various ways. The dumping condition includes the machine body 10a being in a floating state (more specifically, a rear-floating state). The dumping condition may also include the machine body 10a being in a rear-floating state and not performing an excavation operation.

[0113] (Specific Examples of Changing the Target Motion) The above examples of changing the target motion can be combined in various ways. The timing of changing the target motion can be set in various ways, and the content of the change to the target motion can be set in various ways. Below, specific examples of the target motion changing process of the controller 30 will be described with reference to the flowcharts shown in FIGS. 17 to 19. Below, steps S31 to S34 will be described with reference to FIG. 17.

[0114] In step S31, the controller 30 shown in FIG. 1 acquires information about the tilt of the machine body 10a detected by the tilt detection device 21b.

[0115] In step S32, the controller 30 determines whether the machine body 10a is floating based on the tilt acquired in step S31. If the machine body 10a is not floating (NO in step S32), the controller 30 returns the process flow to step S31 (start). If the machine body 10a is floating (YES in step S32), the controller 30 causes the process flow to proceed to step S33.

[0116] In step S33, controller 30 stores the "floating state bucket height," which is bucket height H15c (see FIG. 10) when machine main body 10a is in the floating state. In FIG. 17, the floating state bucket height is simply referred to as the "bucket height."

[0117] In step S34, the controller 30 determines whether the machine body 10a is in a front-floating state based on the inclination acquired in step S31. If the machine body 10a is in a front-floating state (YES in step S34), the controller 30 performs processing to deal with the front-floating state in the current excavation operation (step S50). If the machine body 10a is in a rear-floating state (NO in step S34), the controller 30 performs processing to deal with the rear-floating state in the current excavation operation (step S70).

[0118] As shown in Fig. 18, in step S50, if the machine body 10a is in a front-floating state, the controller 30 shown in Fig. 1 performs processing to deal with the front-floating state during the current excavation operation. Steps S52 to S54 will be described below with reference to Fig. 18.

[0119] In step S52, the controller 30 shown in FIG. 1 determines the tilt state (degree of tilt) of the machine body 10a. Specifically, the controller 30 determines whether the tilt state in the front-floating state of the machine body 10a is a "large tilt state." In FIG. 18, the "large tilt state" is simply referred to as "large." The criteria for determining whether the machine body 10a is in a large tilt state are set in advance in the controller 30 (before determining whether the machine body 10a is in a large tilt state). The large tilt state may be, for example, whether the difference between the inclination angle during work and the initial inclination angle (relative value of the inclination angle) is equal to or greater than a threshold value, or whether the value of the inclination angle during work (absolute value of the inclination angle) is equal to or greater than a threshold value. If the inclination state of the machine body 10a is not a "large tilt state" (NO in step S52), the controller 30 proceeds to step S52n. If the tilt state of the machine body 10a is "large tilt state" (YES in step S52), the controller 30 causes the flow to proceed to step S53.

[0120] In step S52n, controller 30 changes the target path P for the current excavation operation. For example, controller 30 decreases the target excavation depth Ld (see example A1 above) (see FIG. 4). Then, controller 30 ends the process for dealing with the front lifting state in the current excavation operation (step S50), and causes the flow to proceed to step S61 (see FIG. 17).

[0121] In step S53, the controller 30 causes the bucket 15c to move in the opposite direction (reverse operation) to the movement of the bucket 15c along the target path P in the excavation operation, as shown in FIG. 14 (see example C above).

[0122] In step S54, the controller 30 determines whether the front floating state of the machine main body 10a has been resolved. The controller 30 continues the process for the reverse operation of step S53 until the front floating state of the machine main body 10a is resolved (until step S54 returns YES). If the front floating state of the machine main body 10a has been resolved (step S54 returns YES), the controller 30 ends the process for dealing with the front floating state in the current excavation operation (step S50) and proceeds to step S61 shown in Figure 17.

[0123] In step S61, controller 30 determines whether bucket height H15c (see FIG. 10 ) for the next excavation operation is greater (deeper) than the “floating-state bucket height” stored in step S33. Here, “bucket height H15c for the next excavation operation” refers to the bucket height H15c expected for the next excavation operation. Controller 30 can acquire the bucket height H15c expected for the next excavation operation based on the target motion for the next excavation operation. Specifically, the target motion for the next excavation operation may include the target path P and the target bucket ground angle θ. More specifically, the target motion for the next excavation operation may include at least one of, for example, the target excavation depth Ld, the target bucket ground angle θs for the start of excavation, the target excavation end position Pe, and the target horizontal excavation distance Lh. If bucket height H15c for the next excavation operation is greater than the floating-state bucket height (YES in step S61), controller 30 causes the flow to proceed to step S62. If the bucket height H15c in the next excavation operation is the same as or smaller (shallower) than the floating state bucket height (NO in step S61), the controller 30 ends the processing flow for the current excavation operation (proceeds to RETURN), and then starts the processing flow for the next excavation operation (returns to START).

[0124] In step S62, the controller 30 performs processing to address the front lift state in the next excavation operation. For example, as shown in FIG. 4 , the controller 30 changes the target path P for the next excavation operation (see Example A above). Specifically, the controller 30 decreases the target excavation depth Ld for the next excavation operation (see Example A1 above). Also, for example, the controller 30 changes the target bucket ground angle θs for starting excavation in the next excavation operation (see Example B above). Then, the controller 30 ends the processing flow for the current excavation operation and starts the processing flow for the next excavation operation.

[0125] As shown in Fig. 19, in step S70, if the machine body 10a is in a rear-floating state (NO in step S34 in Fig. 17), the controller 30 performs processing to deal with the rear-floating state during the current excavation operation. Steps S71 to S76 shown in Fig. 19 will be described below with reference to Fig. 19.

[0126] 1 determines whether the bucket 15c (the attachment 15) is performing an excavation operation. If the bucket 15c is performing an excavation operation (YES in step S71), the controller 30 causes the flow to proceed to step S72. If the bucket 15c is not performing an excavation operation (NO in step S71), the controller 30 causes the flow to proceed to step S71n.

[0127] In step S71n, the controller 30 causes the bucket 15c to perform a discharge operation, as shown in FIG. 16 (see Example E above). Specifically, when the machine body 10a is in a rear-floating state and the bucket 15c is not performing an excavation operation, the controller 30 causes the bucket 15c to perform a discharge operation. At this time, the controller 30 may also cause the boom 15a to perform a boom-up operation. The controller 30 then ends the process for dealing with the rear-floating state during the current excavation operation (step S70), and causes the flow to proceed to step S81 (see FIG. 17).

[0128] In step S72, the controller 30 determines the tilt state of the machine body 10a. Specifically, similar to step S52 (see FIG. 18), the controller 30 determines whether the tilt state (degree of tilt) of the machine body 10a is a "large tilt state." In FIG. 19, the "large tilt state" is simply referred to as "large." Note that the "large tilt state" in step S52 (see FIG. 18) and the "large tilt state" in step S72 may be the same or different. If the tilt state of the machine body 10a is not a "large tilt state" (NO in step S72), the controller 30 advances the flow to step S72n. If the tilt state of the machine body 10a is a "large tilt state" (YES in step S72), the controller 30 advances the flow to step S73.

[0129] In step S72n, the controller 30 changes the target path P for the current excavation operation. For example, as shown in FIG. 6, the controller 30 may shallow the target excavation depth Ld (see example A2-1 above), shorten the target horizontal excavation distance Lh (see example A2-2 above), or change the target excavation end position Pe forward X1 (see example A2-3 above). The controller 30 may make only one of these changes, or may make multiple of these changes. Then, the controller 30 ends the process for dealing with the rear lifting state in the current excavation operation (step S70) and proceeds to step S81 (see FIG. 17).

[0130] In step S73, when the rear floating state of the machine body 10a is in the "large tilt state", the controller 30 causes only the bucket 15c to perform the excavation operation as shown in FIG. 15 (see example D above).

[0131] In step S74, the controller 30 determines whether the rear-floating state of the machine body 10a has worsened (the tilt has increased) as a result of performing the excavation operation using only the bucket 15c (performing step S73). If the rear-floating state of the machine body 10a has worsened (YES in step S74), the controller 30 causes the flow to proceed to step S75. If the rear-floating state of the machine body 10a has not worsened (NO in step S74), the controller 30 causes the flow to proceed to step S74n.

[0132] In step S74n, controller 30 determines whether the excavation operation using only bucket 15c (step S73) has been completed. Specifically, controller 30 determines whether the angle of bucket 15c relative to the ground or bucket rotation angle φ has reached a predetermined angle (excavation operation end angle). If the excavation operation using only bucket 15c has been completed (YES in step S74n), controller 30 ends the process for dealing with the front lift state during this excavation operation (step S70) and proceeds to step S81 (see FIG. 17 ). If the excavation operation using only bucket 15c has not been completed (NO in step S74n), controller 30 continues the excavation operation using only bucket 15c (returns the flow to step S73).

[0133] In step S75, the controller 30 causes the bucket 15c to move in the opposite direction to the movement of the bucket 15c along the target path P in the excavation operation, i.e., causes the bucket 15c to perform the reverse movement along the target path P (see example C above). In more detail, if the rear-floating state has worsened due to the excavation operation of only the bucket 15c (step S73) shown in Figure 15 (YES in step S74), the controller 30 causes the bucket 15c to perform the reverse movement along the target path P, as shown in Figure 14. Note that while Figure 14 illustrates an example of a front-floating state, the processing of step S75 targets the rear-floating state.

[0134] In step S76, the controller 30 determines whether the rear-floating state of the machine body 10a has been resolved by the reverse operation of the target path P (step S75). If the rear-floating state of the machine body 10a has not been resolved (NO in step S76), the controller 30 continues processing for the reverse operation of the target path P (return to step S75). If the rear-floating state of the machine body 10a has been resolved (YES in step S76), the controller 30 ends processing for the reverse operation of the target path P. Then, the controller 30 ends the processing for dealing with the front-floating state in the current excavation operation (step S70), and proceeds to step S81 shown in FIG. 17.

[0135] In step S81, controller 30 determines whether bucket height H15c (see FIG. 10 ) for the next excavation operation is greater (deeper) than the "floating bucket height" stored in step S33 (similar to step S61). Here, "bucket height H15c for the next excavation operation" refers to the bucket height H15c expected for the next excavation operation. Controller 30 can obtain the bucket height H15c expected for the next excavation operation based on the target operation for the next excavation operation. If bucket height H15c for the next excavation operation is greater (deeper) than the floating bucket height (YES in step S81), controller 30 advances the flow to step S82. If bucket height H15c for the next excavation operation is the same as or smaller (shallower) than the floating bucket height (NO in step S81), controller 30 ends the processing flow for the current excavation operation (proceeds to RETURN). Then, the controller 30 starts the processing flow for the next excavation operation (returns to start).

[0136] In step S82, the controller 30 performs processing to deal with the rear-floating state in the next excavation operation. For example, the controller 30 changes the target path P for the next excavation operation, as shown in FIG. 6. For example, the controller 30 may shallow the target excavation depth Ld (see example A2-1 above), shorten the target horizontal excavation distance Lh (see example A2-2 above), or change the target excavation end position Pe forward X1 (see example A2-3 above). The controller 30 may make only one of these changes, or may make multiple of these changes. Then, the controller 30 ends the processing flow for the current excavation operation and starts the processing flow for the next excavation operation.

[0137] (Consideration) In the work machine target motion setting system 1 of this embodiment, if it is determined that the machine body 10a is in a floating state based on the inclination of the machine body 10a detected by the inclination detection device 21b shown in FIG. 1 , a target motion change process may be performed. Here, a case where the target motion of the excavation operation is changed in accordance with information other than the inclination of the machine body 10a is considered. For example, a case where the target motion of the excavation operation is changed in accordance with shape information of the surface of the work object (e.g., the ground surface) is considered (a consideration example). In this consideration example, even if the shape of the work object remains the same, whether or not the machine body 10a is in a floating state changes depending on the environment, such as the quality of the work object (e.g., soil quality). In addition, a database showing the relationship between shape information of the surface of the work object and the target motion may be required. In this case, the processing load on the controller 30 may be large. On the other hand, in this embodiment, if it is determined that the machine body 10a is in a floating state based on the detected (actual) inclination of the machine body 10a, a target motion change process may be performed. Therefore, there is no need to prepare a large amount of information, such as a database showing the relationship between the surface shape information of the work object and the target operation, and the processing load on the controller 30 can be reduced.

[0138] (Effects of the First Invention) The effects of the work machine target movement setting system 1 shown in Fig. 1 are as follows. The work machine target movement setting system 1 includes a machine body 10a, a tilt detection device 21b, an attachment 15, and a controller 30. The tilt detection device 21b detects the tilt of the machine body 10a. The attachment 15 is attached to the machine body 10a and has a bucket 15c that performs excavation work. The controller 30 sets a target movement for the excavation operation of the bucket 15c.

[0139] [Configuration 1] The controller 30 determines whether the mechanical body 10a is in a floating state relative to the ground surface based on the inclination of the mechanical body 10a detected by the inclination detection device 21b. The controller 30 performs a target motion change process when a target motion change condition set in the controller 30 is satisfied. The target motion change process is a process of changing the target motion so that the inclination of the mechanical body 10a becomes smaller. The target motion change condition includes the mechanical body 10a being in a floating state.

[0140] In the above [Configuration 1], when a target motion change condition is satisfied, including the machine body 10a being in a floating state, the controller 30 performs a target motion change process that changes the target motion so that the tilt of the machine body 10a becomes smaller. Thus, when the machine body 10a becomes in a floating state, the controller 30 can change the target motion so that the tilt of the machine body 10a becomes smaller. Therefore, it is possible to reduce the degree to which the machine body 10a is in a floating state when the work machine 10 operates in accordance with the target motion.

[0141] (Effects of the second invention)

[0142] [Configuration 2] The target motion change process includes changing one or both of the target bucket ground angle θs at the start of excavation, which is the angle of the bucket 15c with respect to the ground at the start position of the excavation motion, and the target path P of the bucket 15c during the excavation motion.

[0143] The above-described [Configuration 2] provides the following effect. The reaction force F (see FIGS. 3 and 5 ) that the bucket 15c receives from the work object changes depending on the angle of the bucket 15c with respect to the ground at the start position of the excavation operation (ground angle) and the path of the bucket 15c during the excavation operation. This reaction force F may cause the machine body 10a to float. Therefore, in the above-described [Configuration 2], the change in the target operation includes changing either or both of the target bucket ground angle θs for starting excavation, which is the angle of the bucket 15c with respect to the ground at the start position of the excavation operation, and the target path P of the bucket 15c during the excavation operation. Specifically, the controller 30 preferably changes either or both of the target bucket ground angle θs for starting excavation and the target path P so as to reduce the reaction force F that the bucket 15c receives from the work object when the bucket 15c is performing the excavation operation. As a result, the degree to which the machine body 10a floats can be reduced.

[0144] (Effects of the third invention)

[0145] [Configuration 3] The target motion change conditions include a front-floating state handling condition. The front-floating state handling condition includes a front-floating state in which the front portion of the machine body 10a is floating above the ground surface, as shown in Fig. 3. When the front-floating state handling condition is satisfied, the controller 30 changes, in the target motion change process, one or both of the target bucket ground angle θs at the start of excavation and the target excavation depth Ld of the bucket 15c during the excavation operation, as shown in Fig. 4.

[0146] The above-described [Configuration 3] achieves the following effect. The reaction force F (see FIG. 3) that the bucket 15c receives from the workpiece during excavation varies depending on the angle of the bucket 15c with respect to the ground at the start of the excavation operation and the digging depth of the bucket 15c during the excavation operation. This reaction force F may cause the machine body 10a to float forward. Therefore, in the above-described [Configuration 3], when the machine body 10a is in the float forward state, one or both of the target bucket ground angle θs for starting excavation and the target excavation depth Ld may be changed. The controller 30 preferably changes one or both of the target bucket ground angle θs for starting excavation and the target excavation depth Ld so as to reduce the reaction force F that the bucket 15c receives upward (e.g., upward Z1) from the workpiece. As a result, the degree to which the machine body 10a floats forward can be reduced.

[0147] (Effects of the fourth invention)

[0148] [Configuration 4] The target operation change condition includes a rear-floating state handling condition. The rear-floating state handling condition includes a rear-floating state in which the rear portion of the machine body 10a is floating above the ground surface, as shown in FIG. 5. When the rear-floating state handling condition is satisfied, the controller 30 changes one or more of the target horizontal excavation distance Lh, the target excavation depth Ld of the bucket 15c during excavation operation, and the target excavation end position Pe in the target operation change process, as shown in FIG. 6. The target horizontal excavation distance Lh is the excavation distance in the horizontal direction of the bucket 15c during excavation operation. The target excavation end position Pe is the position at which the excavation operation ends.

[0149] The above-described [Configuration 4] provides the following effect. The reaction force F (see FIG. 5 ) that the bucket 15c receives from the work object while the bucket 15c is performing the excavation operation changes depending on the horizontal excavation distance, excavation depth, and excavation end position of the bucket 15c during the excavation operation. This reaction force F may cause the machine body 10a to become rear-floated. Therefore, in the above-described [Configuration 4], when the machine body 10a is in the rear-floated state, one or more parameters among the target horizontal excavation distance Lh, target excavation depth Ld, and target excavation end position Pe may be changed. The controller 30 preferably changes one or more of the target horizontal excavation distance Lh, target excavation depth Ld, and target excavation end position Pe so as to reduce the reaction force F that the bucket 15c receives from the work object in a downward direction (e.g., downward Z2). As a result, the degree of rear-floating of the machine body 10a can be reduced.

[0150] (Effects of the fifth invention)

[0151] [Configuration 5] As shown in Fig. 10 , controller 30 stores bucket height H15c, which is the position of bucket 15c in the height direction when machine body 10a is in a floating state, i.e., the floating state bucket height. Controller 30 limits changes to the target motion in the target motion change process when bucket 15c performs an excavation operation at a position above the height threshold. The height threshold is a threshold that is set based on the floating state bucket height.

[0152] The above-described [Configuration 5] achieves the following effect. When the bucket 15c excavates at a position above the floating-state bucket height, the risk of the machine body 10a becoming floating is lower than when the bucket 15c excavates at the same height or a position (deeper position) below the floating-state bucket height. In other words, a position above the floating-state bucket height is shallower than the floating-state bucket height, for example, a position Z1 above the floating-state bucket height. Furthermore, if the target motion is changed too much to reduce the inclination of the machine body 10a when the bucket 15c excavates at a position above the floating-state bucket height, the amount of workpiece excavated by the bucket 15c may be excessively reduced. Therefore, in the above-described [Configuration 5], the controller 30 limits the change in the target motion in the target motion change process when the bucket 15c performs an excavation operation at a position above the height threshold based on the floating-state bucket height. This ensures the amount of workpiece excavated by the bucket 15c when the bucket 15c performs an excavation operation at a position above the height threshold.

[0153] 7, the attachment 15 includes the arm 15b to which the bucket 15c is rotatably attached. The controller 30 sets an allowable bucket rotation angle range, which is an allowable range of the bucket rotation angle φ, which is the angle of the bucket 15c with respect to the arm 15b.

[0154] [Configuration 6] When performing target operation change processing, controller 30 determines a changed excavation start target bucket ground angle θs (step S11 in FIG. 9 ). If the angle of bucket 15c with respect to arm 15b (bucket rotation angle φ) for positioning bucket 15c at the determined excavation start target bucket ground angle θs is outside the bucket rotation angle allowable range, controller 30 performs the following processing. In this case (NO in step S13 in FIG. 9 ), controller 30 changes target excavation start position Ps, which is the position where excavation operation is to be started.

[0155] In the above-described [Configuration 6], if the bucket rotation angle φ is outside the bucket rotation angle allowable range, the target excavation start position Ps is changed. Therefore, with the bucket rotation angle φ within the bucket rotation angle allowable range, the ground angle of the bucket 15c at the start position of the excavation operation (target excavation start position Ps) can be easily set to the changed target bucket ground angle θs for excavation start. As a result, the degree of front lift of the machine body 10a can be reduced.

[0156] (Effects of the seventh invention)

[0157] [Configuration 7] In the target motion change process, the controller 30 shown in FIG. 1 changes the amount of change in the target motion according to the tilt of the machine body 10a detected by the tilt detection device 21b (see FIG. 11).

[0158] With the above [Configuration 7], controller 30 can set the change amount of the target motion to an appropriate change amount corresponding to the inclination of machine body 10a. As a result, the degree of floating of machine body 10a can be further reduced compared to when the change amount of the target motion is too small. Furthermore, the amount of excavation of the work object by bucket 15c can be ensured compared to when the change amount of the target motion is too large.

[0159] (Effect of the eighth invention)

[0160] [Configuration 8] If the target motion change condition is satisfied when the bucket 15c performs an excavation operation with the changed target motion, the controller 30 further changes the target motion in the target motion change process so as to reduce the inclination of the machine body 10a (see FIG. 12 ).

[0161] The above [Configuration 8] provides the following effect. In the above [Configuration 1], when a target motion change condition is satisfied, including the machine body 10a being in a floating state, the controller 30 performs a target motion change process to change the target motion so that the inclination of the machine body 10a is reduced. Then, when the bucket 15c performs an excavation operation with the changed target motion, the target motion change condition, including the machine body 10a being in a floating state, may be satisfied again. In this case, in the above [Configuration 8], the controller 30 further changes the target motion in the target motion change process so that the inclination of the machine body 10a is reduced (adds or accumulates the change amount). Therefore, when the bucket 15c performs an excavation operation with the changed target motion, the degree to which the machine body 10a is in a floating state can be reduced.

[0162] (Effect of the ninth invention)

[0163] [Configuration 9] In the target motion change process, the controller 30 limits the change of the target motion so that the accumulated change amount obtained by accumulating the change amounts of the target motion is equal to or less than an accumulated change amount limit value set in the controller 30 (see FIG. 12 ).

[0164] The above [Configuration 9] provides the following effect. In the above [Configuration 8], if the machine body 10a becomes floating again when the bucket 15c performs an excavation operation based on the changed target motion, the controller 30 further changes the target motion so that the inclination of the machine body 10a becomes smaller. In this case, it is conceivable that the target motion may be changed too much in order to reduce the inclination of the machine body 10a. Therefore, in the above [Configuration 9], the controller 30 limits the change in the target motion so that the integrated change amount obtained by accumulating the changes in the target motion is equal to or less than the integrated change amount limit value set in the controller 30. This makes it possible to ensure the amount of excavation of the work object by the bucket 15c.

[0165] (Effect of the 10th invention)

[0166] [Configuration 10] If the target motion change condition is satisfied while the bucket 15c is performing the current excavation operation, the controller 30 changes the target motion for the next and subsequent excavation operations in the target motion change process (see steps S62 and S82 in FIG. 17 ).

[0167] In the above [Configuration 10], the degree of floating of machine body 10a in the next and subsequent excavation operations can be reduced. If the target motion for the next and subsequent excavation operations is changed but the target motion for the current excavation operation is not changed, it is easy to ensure the amount of work object excavated by bucket 15c in the current excavation operation.

[0168] (Effects of the eleventh invention)

[0169] [Configuration 11] If the target motion change condition is satisfied while the bucket 15c is performing the current excavation operation, the controller 30 changes the target motion for the current excavation operation in the target motion change process (see step S52n in FIG. 18 and step S72n in FIG. 19 ).

[0170] In the above [Configuration 11], the degree of floating of the machine body 10a during the current excavation operation can be reduced.

[0171] (Effects of the twelfth aspect of the invention)

[0172] [Configuration 12] The target motion change condition includes a reverse motion execution condition. The reverse motion execution condition includes the machine body 10a being in a floating state and the inclination of the machine body 10a detected by the inclination detection device 21b being a specific inclination state set in the controller 30. As shown in FIG. 14 , when the reverse motion execution condition is satisfied, the controller 30 performs the following process in the target motion change process. In this case, the controller 30 changes the target motion so that the bucket 15c moves in a direction opposite to the direction of movement of the bucket 15c along the target path P of the bucket 15c (see the reverse motion in Example C above).

[0173] With the above-described [Configuration 12], when bucket 15c operates in the direction opposite to the direction of movement of bucket 15c along target path P, reaction force F (see FIGS. 3 and 5) acting from the work object to bucket 15c is reduced, thereby reducing the degree to which machine main body 10a is floating.

[0174] (Effects of the thirteenth invention)

[0175] [Configuration 13] The target motion change condition includes a motion element restriction condition. The motion element restriction condition includes the machine body 10a being in a floating state and the inclination of the machine body 10a detected by the inclination detection device 21b being a specific inclination state set in the controller 30. As shown in Fig. 15 , when the motion element restriction condition is satisfied, the controller 30 changes the target motion in the target motion change process so that only the bucket 15c of the multiple elements that make up the attachment 15 is operated.

[0176] The above-described [Configuration 13] provides the following effect: When only the bucket 15c is moved, the reaction force F (see FIGS. 3 and 5) acting from the work object to the bucket 15c is reduced compared to when the bucket 15c and elements other than the bucket 15c are moved among the multiple elements that make up the attachment 15. This reduces the degree to which the machine body 10a is floating.

[0177] (Effect of the fourteenth invention)

[0178] [Configuration 14] The target motion change condition includes a discharge condition. The discharge condition includes a state in which the rear portion of the machine body 10a is in a post-floating state above the ground surface and no excavation motion is being performed, as shown in Fig. 16. When the discharge condition is satisfied, the controller 30 changes the target motion in the target motion change process so that the bucket 15c performs a discharge motion.

[0179] In the above-described [Configuration 14], when the machine body 10a is in the rear-floating state, a work object may be discharged from the bucket 15c. In this case, the load acting on the bucket 15c due to the mass of the work object is reduced. As a result, the degree of rear-floating state of the machine body 10a is reduced.

[0180] (Effects of the fifteenth aspect of the invention)

[0181] [Configuration 15] The controller 30 automatically controls the attachment 15 so that the excavation operation of the bucket 15c is performed in accordance with a target operation.

[0182] The above [Configuration 15] makes it possible to reduce the degree to which the machine body 10a floats when the work machine 10 operates under automatic control.

[0183] (Modifications) The above embodiment may be modified in various ways. For example, the modifications of the above embodiment may be combined in various ways. For example, the number of components (including the modifications) of the above embodiment may be changed, or some of the components may not be provided. For example, the components may be fixed or connected directly or indirectly to one another. For example, the connections between the components shown in FIG. 2 may be changed. For example, the arrangement of the components may be changed. For example, the inclusion relationships between the components may be changed in various ways. For example, a component described as a lower-level component included in a higher-level component may not be included in this higher-level component, but may be included in another component. For example, what is described as multiple different components or parts may be combined into a single component or part. For example, what is described as a single component or part may be provided as multiple different components or parts. For example, the order of steps in a flowchart (see FIG. 17, etc.) may be changed, some steps may not be performed, or steps of different flowcharts may be combined. For example, the various parameters (e.g., various parameters of the target path P) used for control by the controller 30 shown in FIG. 1 do not have to be identical to these various parameters, and may be parameters that can be converted into various parameters. For example, the controller 30 may perform substantially the same processing as that of the above-described embodiment (including modifications). The various processing may be combined in various ways. For example, each component may have only a part of its characteristics (function, arrangement, shape, operation, etc.).

Claims

1. A work machine target motion setting system comprising: a machine body; a tilt detection device that detects the inclination of the machine body; an attachment attached to the machine body and having a bucket for performing excavation work; and a controller that sets a target motion for the excavation motion of the bucket, wherein the controller determines whether the machine body is in a floating state relative to the ground surface based on the inclination of the machine body detected by the tilt detection device, and performs a target motion change process that changes the target motion so that the inclination of the machine body is reduced when a target motion change condition set in the controller is satisfied, and the target motion change condition includes the machine body being in a floating state.

2. A work machine target motion setting system as described in claim 1, wherein the target motion change process includes changing one or both of a target bucket ground angle at the start of excavation, which is the angle of the bucket with respect to the ground at the start position of the excavation operation, and a target path of the bucket during the excavation operation.

3. A work machine target motion setting system as described in claim 2, wherein the target motion change condition includes a front-floating state handling condition including a front portion of the machine body being in a front-floating state in which it is floating above the ground surface, and when the front-floating state handling condition is satisfied, the controller changes one or both of the target bucket ground angle at the start of excavation and the target digging depth of the bucket during the excavation operation in the target motion change process.

4. A work machine target operation setting system as described in claim 2 or 3, wherein the target operation change condition includes a rear-floating state handling condition including a rear portion of the machine body being in a rear-floating state above the ground surface, and when the rear-floating state handling condition is satisfied, the controller changes one or more of the target horizontal excavation distance, which is the excavation distance in the horizontal direction of the bucket during the excavation operation, the target excavation depth of the bucket during the excavation operation, and the target excavation end position, which is the position at which the excavation operation ends, in the target operation change process.

5. A work machine target movement setting system as claimed in any one of claims 2 to 4, wherein the controller stores a floating state bucket height, which is the position of the bucket in the height direction when the machine body is in the floating state, and limits changes to the target movement in the target movement changing process when the bucket performs the excavation movement at a position above a height threshold, which is a threshold value set based on the floating state bucket height.

6. A work machine target movement setting system according to any one of claims 2 to 5, wherein the attachment comprises an arm to which the bucket is rotatably attached, a bucket rotation angle tolerance range which is a tolerance range for the angle of the bucket relative to the arm is set in the controller, and the controller, when performing the target movement change processing, determines the changed excavation start target bucket ground angle, and changes a target excavation start position, which is a position at which the excavation movement is to be started, if the angle of the bucket relative to the arm for positioning the bucket at the determined excavation start target bucket ground angle is outside the bucket rotation angle tolerance range.

7. A work machine target motion setting system as claimed in any one of claims 2 to 6, wherein the controller, in the target motion changing process, changes an amount of change in the target motion according to the inclination of the machine body detected by the inclination detection device.

8. A work machine target motion setting system as claimed in any one of claims 2 to 7, wherein the controller, in the target motion change process, further changes the target motion so as to reduce the inclination of the machine body if the target motion change condition is satisfied when the bucket is caused to perform the excavation motion with the changed target motion.

9. A work machine target operation setting system as described in claim 8, wherein the controller, in the target operation change process, limits the change to the target operation so that an accumulated change amount obtained by accumulating the change amounts of the target operation is equal to or less than an accumulated change amount limit value set in the controller.

10. A work machine target motion setting system as claimed in any one of claims 1 to 9, wherein the controller changes the target motion for the next and subsequent excavation operations in the target motion change process when the target motion change condition is satisfied while the bucket is performing the current excavation operation.

11. A work machine target motion setting system as claimed in any one of claims 1 to 10, wherein the controller changes the target motion for the current excavation operation in the target motion change process when the target motion change condition is satisfied while the bucket is performing the current excavation operation.

12. A work machine target motion setting system as described in claim 11, wherein the target motion change condition includes an inverse motion execution condition including that the machine body is in a floating state and the inclination of the machine body detected by the inclination detection device is in a specific inclination state set in the controller, and when the inverse motion execution condition is satisfied, the controller changes the target motion in the target motion change process so that the bucket moves in a direction opposite to the direction of movement of the bucket along the target path of the bucket.

13. A work machine target motion setting system as described in claim 11 or 12, wherein the target motion change condition includes an operation element limiting condition including that the machine body is in a floating state and the inclination of the machine body detected by the inclination detection device is in a specific inclination state set in the controller, and when the operation element limiting condition is satisfied, the controller changes the target motion in the target motion change process so as to operate only the bucket among the multiple elements constituting the attachment.

14. A work machine target motion setting system as claimed in any one of claims 11 to 13, wherein the target motion change condition includes a discharge condition including a state in which a rear portion of the machine body is in a floating state after being lifted off the ground surface and the excavation operation is not being performed, and when the discharge condition is satisfied, the controller changes the target motion in the target motion change process so as to cause the bucket to perform a discharge operation.

15. A work machine target motion setting system according to any one of claims 1 to 14, wherein the controller automatically controls the attachment so that the excavation motion of the bucket is performed in accordance with the target motion.

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