Work machine

Abstract

An object is to ensure posture stability of a work machine by taking into account the effect of a cliff-like terrain on the posture stability of the work machine. The work machine includes a posture detection device that detects an inclination angle of the work machine and a swing angle of an upper swing body; a surrounding detection device that detects a surrounding terrain; and a controller that controls the work machine. The controller includes: a cliff determination section that determines whether a bench edge exists around the work machine based on a detection result of the surrounding detection device; a center-of-gravity calculation section that calculates a center-of-gravity position of the work machine based on a detection result of the posture detection device; and a stabilization assistance section that assists in posture stabilization of the work machine. If a distance between the bench edge and the center-of-gravity position is equal to or less than a threshold, the stabilization assistance section causes a notification device to issue an alert or restricts an operator operation that will cause the center-of-gravity position to approach the bench edge, as assisting in the posture stabilization.

Description

Technical Field

[0001] The present invention relates to a work machine.Background Art

[0002] There is known a work machine including an upper swing body attached swingably to a lower traveling body and an articulated work device attached rotatably to the upper swing body. The work device includes a boom attached rotatably to the upper swing body, an arm attached rotatably to the boom, and a bucket attached rotatably to the arm.

[0003] Patent Literature 1 describes a technique of estimating the volume of earth and sand to be lifted using the bucket and evaluating the posture stability of the work machine on the basis of the estimated volume of the earth and sand and the posture of the upper swing body, the boom, the arm, and the bucket. In addition, Patent Literature 1 mentions acquiring information about terrains and estimating the volume of earth and sand to be lifted by the bucket.Citation ListPatent Literature

[0004] Patent Literature 1: JP 2022-154674 ASummary of InventionTechnical Problem

[0005] The posture stability of the work machine is affected by the terrain around the work machine. For example, if there is a cliff-like terrain around the work machine and the work machine is inclined downward from the cliff, the posture stability of the work machine is likely to decrease. Patent Literature 1 describes estimating the volume of earth and sand in the bucket from the terrain and evaluating the posture stability, but does not mention the effect of the cliff-like terrain on the posture stability.

[0006] The present invention has been made in view of the foregoing, and aims to ensure the posture stability of the work machine by taking into account the effect of the cliff-like terrain on the posture stability of the work machine.Solution to Problem

[0007] To solve the above problem, the work machine of the present invention is a work machine including a lower traveling body and an upper swing body provided swingably to the lower traveling body. The work machine includes: a posture detection device that detects an inclination angle of the work machine and a swing angle of the upper swing body; a surrounding detection device that detects a terrain around the work machine; and a controller that controls the work machine. The controller includes: a cliff determination section that determines whether a cliff edge exists around the work machine based on a detection result of the surrounding detection device; a center-of-gravity calculation section that calculates a center-of-gravity position of the work machine based on a detection result of the posture detection device; and a stabilization assistance section that assists in posture stabilization of the work machine. If a distance between the cliff edge determined by the cliff determination section and the center-of-gravity position calculated by the center-of-gravity calculation section is equal to or less than a preset threshold, the stabilization assistance section causes a notification device of the work machine to issue an alert or restricts an operator operation that will cause the center-of-gravity position to approach the cliff edge, as assisting in the posture stabilization.Advantageous Effects of Invention

[0008] According to the present invention, it is possible to ensure the posture stability of the work machine by taking into account the effect of the cliff-like terrain on the posture stability of the work machine.

[0009] Other problems, components, and advantageous effects will become apparent from the following description of embodiments.Brief Description of Drawings

[0010] Fig. 1 is a side view of a work machine. Fig. 2 is a diagram illustrating a state in which the work machine works at a worksite. Fig. 3 is a diagram illustrating the configuration of a hydraulic system mounted on the work machine. Fig. 4 is a block diagram illustrating the functional configuration of a controller according to a first embodiment. Fig. 5 is a diagram showing a reference coordinate system set in the controller shown in Fig. 4. Fig. 6 is a diagram of the reference coordinate system shown in Fig. 5 as viewed from another direction. Fig. 7 is a diagram of the reference coordinate system shown in Fig. 5 as viewed from another direction. Fig. 8 is a flowchart showing a process related to assisting in posture stabilization performed by the controller shown in Fig. 4. Fig. 9 is a rear view of the work machine illustrating a state in which the work machine is inclined in a roll direction. Fig. 10 is a side view of the work machine illustrating a state in which the work machine is inclined in a pitch direction. Fig. 11 is a top view of the work machine illustrating a state during a swing action when a center-of-gravity position is located closer to a front work device. Fig. 12 is a diagram illustrating an example of an alert issued by a notification device shown in Fig. 4. Fig. 13 is a block diagram illustrating the functional configuration of a controller according to a second embodiment. Fig. 14 is a flowchart showing a process related to assisting in posture stabilization performed by the controller shown in Fig. 13. Fig. 15 is a diagram illustrating an example of an alert issued by a notification device shown in Fig. 13. Fig. 16 is a block diagram illustrating the functional configuration of a controller according to a third embodiment. Fig. 17 is a graph illustrating a relationship between a threshold changed by a stabilization assistance section shown in Fig. 16 and soil property information. Fig. 18 is a diagram illustrating a remote operation device that operates the work machine according to a fourth embodiment. Description of Embodiments

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Components denoted by identical reference signs in the embodiments have similar components in the embodiments unless particularly specified otherwise, and description thereof will be omitted.

[0012] In the present embodiment, as a work machine 1, a hydraulic excavator provided with a bucket 10 as a work implement (attachment) at the end of a work device (a front work device 2) will be described by way of example. The work machine 1 may be a work machine provided with an attachment other than the bucket 10. The work machine 1 may be a work machine other than the hydraulic excavator as long as the work machine 1 has an articulated work device with a plurality of members (a boom 8, an arm 9, an attachment, and the like) coupled to each other, on a swingable structure (an upper swing body 7).[First Embodiment]

[0013] The work machine 1 according to a first embodiment will be described using Fig. 1 to Fig. 12. Fig. 1 is a side view of the work machine 1. Fig. 2 is a diagram illustrating a state in which the work machine 1 works at a worksite.

[0014] The work machine 1 performs excavation operation to excavate the ground to be excavated and loading operation to load an excavated object, such as the excavated earth and sand, onto a machine 200 being loaded, such as a hauling machine including a dump truck. The work machine 1 includes an articulated front work device 2 that holds the excavated object and rotates in a vertical direction or a front-rear direction, and a machine main body 3 on which the front work device 2 is mounted.

[0015] The machine main body 3 includes a lower traveling body 5 that travels using a right traveling hydraulic motor 4a and a left traveling hydraulic motor 4b provided in the right and left parts of the lower traveling body 5 and an upper swing body 7 that is attached to the upper part of the lower traveling body 5 via a swinging device and swings using a swing hydraulic motor 6 of the swinging device. Note that in the present embodiment, the right traveling hydraulic motor 4a and the left traveling hydraulic motor 4b are also collectively referred to as a traveling hydraulic motor 4. The lower traveling body 5 includes a right crawler 21a and a left crawler 21b on the right and left sides in pair. In the present embodiment, the right crawler 21a and the left crawler 21b are also collectively referred to as a crawler 21.

[0016] The front work device 2 is an articulated work device made up of a plurality of front members attached to the front part of the upper swing body 7. The front work device 2 includes a boom 8 coupled to the front part of the upper swing body 7 so as to be vertically rotatable, an arm 9 coupled to the end of the boom 8 so as to be vertically rotatable, and a bucket 10 coupled to the end of the arm 9 so as to be vertically rotatable.

[0017] The boom 8 is coupled to the upper swing body 7 by a boom pin 8a to rotate according to expansion and contraction of a boom cylinder 11. The arm 9 is coupled to the end of the boom 8 by an arm pin 9a to rotate according to expansion and contraction of an arm cylinder 12. The bucket 10 is coupled to the end of the arm 9 by a bucket pin 10a and a bucket link 16 to rotate according to expansion and contraction of a bucket cylinder 13.

[0018] A boom angle sensor 14 for detecting a rotation angle of the boom 8 relative to the machine main body 3 (i.e., the upper swing body 7) is attached to the boom pin 8a. An arm angle sensor 15 for detecting a rotation angle of the arm 9 relative to the boom 8 is attached to the arm pin 9a. A bucket angle sensor 17 for detecting a rotation angle of the bucket 10 relative to the arm 9 is attached to the bucket link 16.

[0019] Note that each rotation angle of the boom 8, the arm 9, and the bucket 10 may be acquired by detecting each angle of the boom 8, the arm 9, and the bucket 10 relative to a reference plane such as a horizontal plane using an inertial measurement unit (IMU) and converting the angle into each rotation angle. Further, each rotation angle of the boom 8, the arm 9, and the bucket 10 may be acquired by detecting each stroke of the boom cylinder 11, the arm cylinder 12, and the bucket cylinder 13 using a stroke sensor and converting the stroke into each rotation angle.

[0020] An inclination angle sensor 18 for detecting an inclination angle of the machine main body 3 relative to a reference plane such as a horizontal plane is attached to the upper swing body 7. A swing angle sensor 19 for detecting a swing angle of the upper swing body 7 relative to the lower traveling body 5 is attached to the swinging device between the lower traveling body 5 and the upper swing body 7.

[0021] The boom angle sensor 14, the arm angle sensor 15, the bucket angle sensor 17, the inclination angle sensor 18, and the swing angle sensor 19 form a posture detection device 53 that detects an inclination angle of the machine main body 3, rotation angles of the front work device 2, and a swing angle of the upper swing body 7, and the like.

[0022] Inside of an operator's cab 71 provided on the upper swing body 7, an operation device that operates a plurality of hydraulic actuators 4, 6, 11, 12, 13 is installed. Specifically, the operation device includes a right traveling lever 23a for operating the right traveling hydraulic motor 4a, a left traveling lever 23b for operating the left traveling hydraulic motor 4b, a right operation lever 22a for operating the boom cylinder 11 and the bucket cylinder 13, and a left operation lever 22b for operating the arm cylinder 12 and the swing hydraulic motor 6. In the present embodiment, the right traveling lever 23a, the left traveling lever 23b, the right operation lever 22a, and the left operation lever 22b are also collectively referred to as operation levers 22, 23. The operation levers 22, 23 may be, for example, an electric lever type operation lever. The operation levers 22, 23 include a switch that can specify whether control is enabled or disabled.

[0023] In addition, a surrounding detection device 54 that detects a type and position of an object around the work machine 1 as well as a terrain is attached to the upper swing body 7, for example, on the operator's cab 71. The surrounding detection device 54 may be, for example, a LiDAR (light detection and ranging) or a stereo camera.

[0024] Fig. 2 shows an example of the state in which the work machine 1 works at a worksite, showing the work machine 1 mining ores or the like in a strip mine or the like. In Fig. 2, the height of a ground 220 on which the machine 200 being loaded is located is referred to as ground level. The terrain on which the work machine 1 is located and which is also the target to be excavated is referred to as a bench 210. An upper surface 211 of the bench 210 on which the work machine 1 is located is at a higher position with a height difference of a predetermined value or more above the ground level of the ground 220 on which the machine 200 being loaded is located. The bench 210 includes the upper surface 211 on which the work machine 1 is located, a bench edge 212 which is the edge of the bench 210 (the upper surface 211), and a slope 213 which is a surface connecting the bench edge 212 and the ground 220. The bench edge 212 and the slope 213 form a cliff-like terrain. The bench edge 212 and the slope 213 are an example of a cliff. The bench edge 212 is an example of a cliff edge.

[0025] The surrounding detection device 54 detects the terrain around the work machine 1. The surrounding terrain includes at least the terrain of the bench 210. Multiple surrounding detection devices 54 may be attached to the work machine 1. The surrounding detection device 54 may acquire information about terrains detected by a terrain detection device installed at the worksite via a communication device.

[0026] Fig. 3 is a diagram illustrating the configuration of a hydraulic system mounted on the work machine 1.

[0027] An engine 103, which is a prime mover mounted on the upper swing body 7, drives a main hydraulic pump 102 and a pilot pump 104. A controller 40 controls the rotation action of the front work device 2, the traveling action of the lower traveling body 5, and the swing action of the upper rotating body 7 in accordance with operation information (amount and direction of operation) of the operation levers 22, 23 by an operator. Specifically, the controller 40 detects the operation information of the operation levers 22, 23 by the operator using sensors 52a to 52f such as rotary encoders or potentiometers, and outputs a control command in accordance with the detected operation information to proportional solenoid valves 51a to 511. The proportional solenoid valves 51a to 511 are provided on a pilot line 100. Upon receiving a control command from the controller 40, the proportional solenoid valves 51a to 51l are activated to output pilot pressure to a flow rate control valve 101, and actuate the flow rate control valve 101. Note that in the present embodiment, the sensors 52a to 52f that detect the operation information of the operation levers 22, 23 by the operator are also collectively referred to as an operation detection device 52.

[0028] The flow rate control valve 101 controls pressure oil supplied from the hydraulic pump 102 to each of the swing hydraulic motor 6, the arm cylinder 12, the boom cylinder 11, the bucket cylinder 13, the right traveling hydraulic motor 4a and the left traveling hydraulic motor 4b in accordance with the pilot pressure from the proportional solenoid valves 51a to 511. Note that the proportional solenoid valves 51a, 51b output the pilot pressure for controlling the pressure oil supplied to the swing hydraulic motor 6 to the flow rate control valve 101. The proportional solenoid valves 51c, 51d output the pilot pressure for controlling the pressure oil supplied to the arm cylinder 12 to the flow rate control valve 101. The proportional solenoid valves 51e, 51f output the pilot pressure for controlling the pressure oil supplied to the boom cylinder 11 to the flow rate control valve 101. The proportional solenoid valves 51g, 51h output the pilot pressure for controlling the pressure oil supplied to the bucket cylinder 13 to the flow rate control valve 101. The proportional solenoid valves 51i, 51j output the pilot pressure for controlling the pressure oil supplied to the right traveling hydraulic motor 4a to the flow rate control valve 101. The proportional solenoid valves 51k, 511 output the pilot pressure for controlling the pressure oil supplied to the left traveling hydraulic motor 4b to the flow rate control valve 101.

[0029] The boom cylinder 11, the arm cylinder 12, and the bucket cylinder 13 each extend and contract with the supplied pressure oil, and rotate the boom 8, the arm 9, and the bucket 10, respectively. This changes the position and posture of the bucket 10. The swing hydraulic motor 6 rotates with the supplied pressure oil, and allows the upper swing body 7 to swing. The right traveling hydraulic motor 4a and the left traveling hydraulic motor 4b rotate with the supplied pressure oil, and allows the lower traveling body 5 to travel. Note that even when there is no operation of the operation levers 22, 23 by the operator, the hydraulic actuators 4, 6, 11, 12, 13 can be driven by actuating the proportional solenoid valves 51a to 511 according to the control command from the controller 40 and actuating the flow rate control valve 101.

[0030] Fig. 4 is a block diagram illustrating the functional configuration of the controller 40 according to the first embodiment. Fig. 5 is a diagram showing a reference coordinate system set in the controller 40 shown in Fig. 4. Fig. 6 is a diagram of the reference coordinate system shown in Fig. 5 as viewed from another direction. Fig. 7 is a diagram of the reference coordinate system shown in Fig. 5 as viewed from another direction.

[0031] Although not shown, the controller 40 is composed of a computer in which a CPU (central processing unit), RAM (random access memory), ROM (read only memory), an external I / F (interface), and the like are connected to each other via a bus. The proportional solenoid valve 51, the operation detection device 52, the posture detection device 53, the surrounding detection device 54, a weight acquisition device 55, a notification device 56, and a storage device (for example, a hard disk drive or large-capacity flash memory and the like) are connected to the external I / F of the controller 40.

[0032] The weight acquisition device 55 is a device that acquires the weight of the excavated object excavated by the excavation operation and held in the bucket 10. The weight acquisition device 55 is configured by a known weight acquisition device. The notification device 56 is a device that notifies the operator of information from the controller 40. The notification device 56 is configured, for example, by a display. The notification device 56 may also be configured to include a speaker.

[0033] A reference coordinate system that specifies the position and posture of the components of the work machine 1 is set in advance in the controller 40. The reference coordinate system of the present embodiment is defined as a right-handed coordinate system with the origin O being the point on the swing center axis where the lower traveling body 5 contacts the ground G, as shown in Fig. 5 to Fig. 7. In the reference coordinate system, the forward direction of the lower traveling body 5 is defined as the positive direction of the X axis. In the reference coordinate system, the direction in which the swing center axis extends upward is defined as the positive direction of the Z axis. In the reference coordinate system, of the left and right directions of the lower traveling body 5 that are perpendicular to the X axis and Z axis, the left direction is defined as the positive direction of the Y axis. In addition, in the reference coordinate system, the inclination angle in the front-rear direction of the work machine 1 relative to the direction of gravity is defined as the pitch angle, and the inclination angle in the left-right direction is defined as the roll angle.

[0034] In the reference coordinate system of the present embodiment, the swing angle of the upper swing body 7 is defined as 0 degrees when the front work device 2 is parallel to the X axis. When the swing angle of the upper swing body 7 is 0 degrees, the action plane of the front work device 2 is parallel to the XZ plane, the direction of the lifting action of the boom 8 is the positive direction of the Z axis, and the direction of the dumping action of the arm 9 and the bucket 10 is the positive direction of the X axis.

[0035] The controller 40 includes a topography calculation section 41, a posture calculation section 42, an operation direction calculation section 43, a cliff determination section 44, a center-of-gravity calculation section 45, and a stabilization assistance section 46.

[0036] The posture calculation section 42 calculates a posture of the components of the work machine 1 in the reference coordinate system and the like based on a detection result of the posture detection device 53. Specifically, the posture calculation section 42 calculates a rotation angle θbm of the boom 8 relative to the X axis from a detection signal of the rotation angle of the boom 8 output from the boom angle sensor 14. The posture calculation section 42 calculates a rotation angle θam of the arm 9 relative to the boom 8 from a detection signal of the rotation angle of the arm 9 output from the arm angle sensor 15. The posture calculation section 42 calculates a rotation angle θbk of the bucket 10 relative to the arm 9 from a detection signal of the rotation angle of the bucket 10 output from the bucket angle sensor 17. The posture calculation section 42 calculates a swing angle θsw of the upper swing body 7 relative to the X axis (the lower traveling body 5) from a detection signal of the swing angle of the upper swing body 7 output from the swing angle sensor 19.

[0037] Furthermore, the posture calculation section 42 calculates a plan position and height of each of the boom 8, the arm 9, and the bucket 10 based on the calculated rotation angles θbm, θam, θbk of the front work device 2 and the calculated swing angle θsw of the upper swing body 7, as well as a dimension Lbm of the boom 8, a dimension La of the arm 9, and a dimension Lbk of the bucket 10. Note that the dimension Lbm of the boom 8 is the length from the boom pin 8a to the arm pin 9a. The dimension Lam of the arm 9 is the length from the arm pin 9a to the bucket pin 10a. The dimension Lbk of the bucket 10 is the length from the bucket pin 10a to the end of the bucket 10. Furthermore, when the swing angle θsw is set to zero, the boom pin 8a is offset by Lox in the positive direction of the X axis from the swing center axis.

[0038] Furthermore, the posture calculation section 42 calculates an inclination angle of the machine main body 3 and the lower traveling body 5 relative to a reference plane DP from a detection signal of the inclination angle of the machine main body 3 output from the inclination angle sensor 18. The reference plane DP is, for example, a horizontal plane perpendicular to the direction of gravity. The inclination angle of the machine main body 3 and the lower traveling body 5 relative to the reference plane DP includes a pitch angle θp, which is a rotation angle about the Y axis, and a roll angle θr, which is a rotation angle about the X axis. The posture calculation section 42 can calculate a pitch angular velocity and a roll angular velocity by differentiating the pitch angle θp and the roll angle θr. The posture calculation section 42 calculates a pitch angle θp, a roll angle θr, a pitch angular velocity, and a roll angular velocity of the machine main body 3 and the lower traveling body 5 relative to the reference plane DP from the pitch angle relative to the direction of gravity, the roll angle relative to the direction of gravity, and the swing angle θsw.

[0039] The topography calculation section 41 calculates a terrain around the work machine 1 in the reference coordinate system based on the detection result of the surrounding detection device 54 and the calculation result of the posture calculation section 42. If the bench 210 exists around the work machine 1, the terrain calculated by the topography calculation section 41 includes the terrain of the bench 210. The terrain of the bench 210 includes the terrain of the bench edge 212.

[0040] The cliff determination section 44 determines whether a cliff edge (a bench edge 212) exists around the work machine 1 based on the detection result of the surrounding detection device 54. Specifically, the cliff determination section 44 detects the bench edge 212 using the calculation result of the topography calculation section 41. To detect the bench edge 212, for example, the technique described in JP 2023-69275 A can be used. In this case, the bench edge 212 is detected by determining whether a height H1 of the upper surface 211 on which the work machine 1 is located and the ground surface 220 at a height H2 with a height difference from the height H1 of a predetermined value or more are detected. Note that the method for detecting the bench edge 212 does not need to be limited to this method.

[0041] The cliff determination section 44 then determines whether a bench edge 212 exists within a range of a threshold th from the origin of the reference coordinate system. The threshold th may be, for example, a distance that the bucket 10 can reach. The distance that the bucket 10 can reach may be, for example, the maximum working radius of the work machine 1.

[0042] The cliff determination section 44 then calculates a distance between the bench edge 212 and each component of the work machine 1. Specifically, the cliff determination section 44 calculates a distance between the bench edge 212 and the end of the crawler 21, and a distance between the bench edge 212 and the side portion of the crawler 21. The cliff determination section 44 may calculate a distance between the bench edge 212 and a point on the crawler 21 that is closest to the bench edge 212, rather than the distance between a specific point on the crawler 21 and the bench edge 212.

[0043] The operation direction calculation section 43 calculates speed of each of the hydraulic actuators 6, 11, 12, 13 based on the detection result of the operation detection device 52. The operation direction calculation section 43 calculates a velocity vector generated in the front work device 2 (the bucket 10) based on the calculated speeds of the hydraulic actuators 6, 11, 12, 13 and the posture of the work machine 1 calculated by the posture calculation section 42.

[0044] Specifically, the controller 40 stores in advance a table showing the correspondence between the operation amounts of the operation levers 22, 23 and the speeds of the hydraulic actuators 6, 11, 12, 13. By referencing this table, the operation direction calculation section 43 calculates the speeds of the hydraulic actuators 6, 11, 12, 13 from the operation amounts included in the operation information of the operation levers 22, 23 output from the operation detection device 52. The operation direction calculation section 43 can then convert the speed of the swing hydraulic motor 6 into the swing angular velocity of the upper swing body 7. The operation direction calculation section 43 can convert the speed of the boom cylinder 11 into the rotation angular velocity of the boom 8. The operation direction calculation section 43 can convert the speed of the arm cylinder 12 into the rotation angular velocity of the arm 9. The operation direction calculation section 43 can convert the speed of the bucket cylinder 13 into the rotation angular velocity of the bucket 10.

[0045] The operation direction calculation section 43 then calculates a velocity vector generated in the bucket 10 based on the rotation angles θbm, θam, θbk of the front work device 2 and the swing angle θsw of the upper swing body 7 calculated by the posture calculation section 42, as well as the rotation angular velocities of the front work device 2 and the swing angular velocity of the upper swing body 7.

[0046] The center-of-gravity calculation section 45 calculates a center-of-gravity position of the work machine 1 based on the detection result of the posture detection device 53. Specifically, the center-of-gravity calculation section 45 calculates a current center-of-gravity position of the work machine 1 in the reference coordinate system based on the rotation angles of the front work device 2, the swing angle of the upper swing body 7, and the inclination angle of the machine main body 3 detected by the posture detection device 53, and the weight of the excavated object in the bucket 10 acquired by the weight acquisition device 55. Furthermore, the center-of-gravity calculation section 45 calculates a current center-of-gravity position of the work machine 1 in an upper swing body coordinate system, where, in plan view, the orientation of the front work device 2 is the first axis and the direction perpendicular to the first axis is the second axis.

[0047] Furthermore, based on the operation information detected by the operation detection device 52, the rotation angles of the front work device 2, the swing angle of the upper swing body 7, and the inclination angle of the machine main body 3 detected by the posture detection device 53, the center-of-gravity calculation section 45 predicts a movement direction of the center-of-gravity position in accordance with the operation information. Specifically, the center-of-gravity calculation section 45 predicts a movement direction of the center-of-gravity position of the work machine 1 based on the velocity vector calculated by the operation direction calculation section 43. The center-of-gravity calculation section 45 may also predict a movement trajectory of the center-of-gravity position based on the velocity vector.

[0048] In particular, the center-of-gravity calculation section 45 can predict the movement direction of the center-of-gravity position of the work machine 1 when the upper swing body 7 performs a swing action in accordance with operation information for a swing operation performed on the upper swing body 7. Note that if the machine 200 being loaded has been detected by the surrounding detection device 54, the center-of-gravity calculation section 45 can predict the action direction of the swing action of the upper swing body 7, assuming that the loading operation after the excavation operation will be performed on the machine 200 being loaded. This allows the center-of-gravity calculation section 45 to predict the movement direction of the center-of-gravity position of the work machine 1 when the upper swing body 7 performs a swing action, without using the velocity vector calculated by the operation direction calculation section 43.

[0049] The stabilization assistance section 46 assists in the posture stabilization of the work machine 1. If the distance between the bench edge 212 determined by the cliff determination section 44 and the center-of-gravity position calculated by the center-of-gravity calculation section 45 is equal to or less than a preset threshold, the stabilization assistance section 46 assists in the posture stabilization of the work machine 1.

[0050] Specifically, the stabilization assistance section 46 determines whether the work machine 1 is in an inclined state that causes a change in the distance between the bench edge 212 and the center-of-gravity position, based on the inclination angle of the work machine 1 calculated by the posture calculation section 42 based on the detection result of the posture detection device 53, and the center-of-gravity position calculated by the center-of-gravity calculation section 45. For example, the stabilization assistance section 46 may determine whether the work machine 1 is in an inclined state that causes a change in the distance, by determining whether an inclination angular velocity of the lower traveling body 5 is generated in a direction in which the center-of-gravity position approaches the bench edge 212.

[0051] The stabilization assistance section 46 then determines whether the work machine 1 is in an inclined state and the distance between the bench edge 212 and the center-of-gravity position is less than or equal to a first threshold th1. If the distance between the bench edge 212 and the center-of-gravity position is less than or equal to the first threshold th1, the stabilization assistance section 46 assists in the posture stabilization of the work machine 1.

[0052] As a result, when the work machine 1 is actually in an inclined state, the stabilization assistance section 46 can prevent the bench edge 212 from collapsing, reducing the posture stability of the work machine 1, or can prevent the work machine 1 from falling off the bench edge 212, which could occur if the center-of-gravity position excessively approaches the bench edge 212. Therefore, the work machine 1 can reliably ensure the posture stability of the work machine 1 by taking into account the effect of the cliff-like terrain on the posture stability of the work machine 1.

[0053] The first threshold th1 is a value that distinguishes whether or not the risk of the bench edge 212 collapsing or the risk of the work machine 1 falling off the bench edge 212 significantly increases due to the center-of-gravity position of the work machine 1 approaching the bench edge 212.

[0054] The first threshold th1 may include a first threshold th1a for determining the distance between the bench edge 212 that exists in the direction of travel of the crawler 21 and the center-of-gravity position and a first threshold thlb for determining the distance between the bench edge 212 that exists in the left-right direction of the crawler 21 and the center-of-gravity position, and these thresholds may be set to different values. The crawler 21 is more likely to retreat from the bench edge 212 that exists in the direction of travel of the crawler 21 than from the bench edge 212 that exists in the left-right direction of the crawler 21. Therefore, the first threshold thlb used to determine the bench edge 212 that exists in the left-right direction of the crawler 21 may be set to a larger value than the first threshold thla used to determine the bench edge 212 that exists in the direction of travel of the crawler 21. As a result, when the bench edge 212 exists in the left-right direction of the crawler 21, the stabilization assistance section 46 can assist in the posture stabilization from a situation where the work machine 1 is farther away from the bench edge 212 than when the bench edge 212 exists in the direction of travel of the crawler 21. Therefore, the stabilization assistance section 46 can more reliably ensure the posture stability of the work machine 1.

[0055] Furthermore, the stabilization assistance section 46 predicts a distance between the bench edge 212 and the center-of-gravity position based on the movement direction of the center-of-gravity position predicted by the center-of-gravity calculation section 45, and determines whether the predicted distance between the bench edge 212 and the center-of-gravity position is less than or equal to the second threshold th2. If the predicted distance between the bench edge 212 and the center-of-gravity position is less than or equal to the second threshold th2, the stabilization assistance section 46 assists in the posture stabilization of the work machine 1 even if the work machine 1 is not in an inclined state.

[0056] As a result, the stabilization assistance section 46 can assist in the posture stabilization before the work machine 1 actually becomes inclined, to prevent the posture stability of the work machine 1 from decreasing due to the center-of-gravity position excessively approaching the bench edge 212. Therefore, the work machine 1 can reliably ensure the posture stability of the work machine 1 by taking into account the effect of the cliff-like terrain on the posture stability of the work machine 1.

[0057] The second threshold th2 is a value that distinguishes whether or not the risk of the bench edge 212 collapsing or the risk of the work machine 1 falling off the bench edge 212 is predicted to significantly increase due to the center-of-gravity position of the work machine 1 approaching the bench edge 212. The second threshold th2 may be set to the same value as the first threshold th1, or may be set to a value different from the first threshold th1. For example, the first threshold th1 may be set to a value greater than the second threshold th2. The second threshold th2 is a threshold used when the work machine 1 is not in an inclined state, while the first threshold th1 is a threshold used when the work machine 1 is in an inclined state. By setting the first threshold th1 to a value greater than the second threshold th2, the stabilization assistance section 46 can assist in the posture stabilization from a situation where the work machine 1 is farther away from the bench edge 212 when the work machine 1 is in an inclined state than when the work machine 1 is not in an inclined state. Therefore, the stabilization assistance section 46 can more reliably ensure the posture stability of the work machine 1.

[0058] In particular, the stabilization assistance section 46 predicts a distance between the bench edge 212 and the center-of-gravity position when a swing action is performed, based on the movement direction of the center-of-gravity position predicted by the center-of-gravity calculation section 45, and can determine whether the predicted distance between the bench edge 212 and the center-of-gravity position is less than or equal to the second threshold value th2.

[0059] As a result, even before the swing action of the upper swing body 7 is performed, the stabilization assistance section 46 can predict that the swing action will reduce the posture stability of the work machine 1, and can assist in the posture stabilization. Therefore, the work machine 1 can reliably ensure the posture stability of the work machine 1 by taking into account the effect of the cliff-like terrain on the posture stability of the work machine 1.

[0060] The stabilization assistance section 46, for example, causes the notification device 56 to issue an alert, as assisting in the posture stabilization. At this time, as the alert, the stabilization assistance section 46 causes the notification device 56 to issue at least one of an alert notifying content of the operation that will cause the center-of-gravity position to approach the bench edge 212, and an alert warning that the operation that will cause the center-of-gravity position to approach the bench edge 212 has been performed by the operator.

[0061] Fig. 8 is a flowchart showing a process related to assisting in posture stabilization performed by the controller 40 shown in Fig. 4.

[0062] In step S1, the controller 40 acquires information about the terrain around the work machine 1. Specifically, the controller 40 calculates a terrain around the work machine 1 in the reference coordinate system from a detection result of the surrounding detection device 54.

[0063] In step S2, the controller 40 determines whether a bench edge 212 exists around the work machine 1. Specifically, the controller 40 determines whether a bench edge 212 exists within a range of the threshold th from the origin of the reference coordinate system. If a bench edge 212 exists around the work machine 1, the controller 40 proceeds to step S3. If a bench edge 212 does not exist around the work machine 1, the controller 40 ends the process shown in Fig. 8.

[0064] In step S3, the controller 40 determines whether the work machine 1 is in an inclined state that causes a change in the distance between the bench edge 212 and the center-of-gravity position. If the work machine 1 is in an inclined state that causes a change in the distance between the bench edge 212 and the center-of-gravity position, the controller 40 proceeds to step S4. If the work machine 1 is not in an inclined state that causes a change in the distance between the bench edge 212 and the center-of-gravity position, the controller 40 proceeds to step S5.

[0065] In step S4, the controller 40 determines whether the distance between the bench edge 212 and the center-of-gravity position is less than or equal to the first threshold th1. If the distance between the bench edge 212 and the center-of-gravity position is less than or equal to the first threshold th1, the controller 40 proceeds to step S7. If the distance between the bench edge 212 and the center-of-gravity position is not less than or equal to the first threshold th1, the controller 40 ends the process shown in Fig. 8.

[0066] In step S5, the controller 40 determines whether the center-of-gravity position is located closer to the front work device 2 or to the counterweight, with reference to the upper swing body 7. If the center-of-gravity position is located closer to the front work device 2, the controller 40 proceeds to step S6. If the center-of-gravity position is located closer to the counterweight, the controller 40 ends the process shown in Fig. 8.

[0067] In step S6, the controller 40 determines whether the distance between the bench edge 212 and the center-of-gravity position is predicted to be less than or equal to the second threshold th2 when the upper swing body 7 performs a swing action. If the distance between the bench edge 212 and the center-of-gravity position is predicted to be less than or equal to the second threshold th2, the controller 40 proceeds to step S7. If the distance between the bench edge 212 and the center-of-gravity position is predicted not to be less than or equal to the second threshold th2, the controller 40 ends the process shown in Fig. 8.

[0068] In step S7, the controller 40 causes the notification device 56 to issue an alert notifying content of the operation that will cause the center-of-gravity position to approach the bench edge 212.

[0069] In step S8, the controller 40 determines whether the operation corresponding to the alert in step S7 has been performed by the operator. If the operation corresponding to the alert in step S7 has been performed, the controller 40 proceeds to step S9. If the operation corresponding to the alert in step S7 has not been performed, the controller 40 ends the process shown in Fig. 8.

[0070] In step S9, the controller 40 causes the notification device 56 to issue an alert warning that the operation that will cause the center-of-gravity position to approach the bench edge 212 has been performed by the operator. The controller 40 then ends the process shown in Fig. 8.

[0071] Operational effects of the work machine 1 will be described using Fig. 9 to Fig. 12. Fig. 9 is a rear view of the work machine 1 illustrating a state in which the work machine 1 is inclined in a roll direction.

[0072] As shown in Fig. 9, if the collapse of the bench edge 212 near the left crawler 21b causes the lower traveling body 5 to become inclined in the roll direction, the posture stability of the work machine 1 may decrease. The work machine 1 issues an alert notifying content of the operation that will cause the center-of-gravity position to approach the bench edge 212. The operator who is notified of the alert does not need to perform the operation. This prevents the work machine 1 from applying a large load to the bench edge 212, which could cause the collapse of the bench edge 212, and thus the posture stability of the work machine 1 can be ensured. Therefore, the work machine 1 can ensure the posture stability of the work machine 1 by taking into account the effect of the cliff-like terrain on the posture stability of the work machine 1.

[0073] Fig. 10 is a side view of the work machine 1 illustrating a state in which the work machine 1 is inclined in a pitch direction.

[0074] If the collapse of the bench edge 212 near the front of the crawler 21 causes the lower traveling body 5 to become inclined in the pitch direction, the posture stability of the work machine 1 may decrease. The work machine 1 issues an alert notifying content of the operation that will cause the center-of-gravity position to approach the bench edge 212. The operator who is notified of the alert does not need to perform the operation. This prevents the work machine 1 from applying a large load to the bench edge 212, which could cause the collapse of the bench edge 212, and thus the posture stability of the work machine 1 can be ensured.

[0075] Fig. 11 is a top view of the work machine 1 illustrating a state during a swing action when the center-of-gravity position is located closer to the front work device 2.

[0076] When the bucket 10 is holding an excessively large excavated object, the center-of-gravity position of the work machine 1 shifts toward the front work device 2. If a left swing action is performed in this state, the center-of-gravity position approaches the bench edge 212 near the left crawler 21b, and a large load is applied to the bench edge 212. This could cause the bench edge 212 to collapse, reducing the posture stability of the work machine 1. The work machine 1 issues an alert notifying content of the operation that will cause the center-of-gravity position to approach the bench edge 212. The operator who is notified of the alert does not need to perform the operation. This prevents the work machine 1 from applying a large load to the bench edge 212, which could cause the collapse of the bench edge 212, and thus the posture stability of the work machine 1 can be ensured.

[0077] Fig. 12 is a diagram illustrating an example of an alert issued by the notification device 56 shown in Fig. 4.

[0078] Fig. 12 shows an example of an alert issued in a situation in which a left swing action performed by the upper swing body 7 will cause the center-of-gravity position to approach the bench edge 212. The alert shown in Fig. 12(a) is an example of an alert notifying content of the operation that will cause the center-of-gravity position to approach the bench edge 212, and corresponds to the alert issued in step S7 of Fig. 8. The alert shown in Fig. 12(b) is an example of an alert warning that the operation that will cause the center-of-gravity position to approach the bench edge 212 has been performed by the operator, and corresponds to the alert issued in step S9 of Fig. 8. By issuing such alerts, the work machine 1 can reliably allow the operator to recognize an operation that reduces the posture stability of the work machine 1, thereby reliably ensuring the posture stability of the work machine 1.[Second Embodiment]

[0079] A working machine 1 according to a second embodiment will be described using Fig. 13 to Fig. 15. In the working machine 1 according to the second embodiment, descriptions of components that are the same as those in the first embodiment will be omitted.

[0080] Fig. 13 is a block diagram illustrating the functional configuration of the controller 40 according to the second embodiment.

[0081] The controller 40 of the second embodiment differs from the controller 40 of the first embodiment in that an action controller 47 that controls the action of the work machine 1 is added. The action control section 47 generates a control command for the proportional solenoid valve 51 and outputs the control command to the proportional solenoid valve 51.

[0082] In the second embodiment, if the distance between the bench edge 212 determined by the cliff determination section 44 and the center-of-gravity position calculated by the center-of-gravity calculation section 45 is equal to or less than a preset threshold, the stabilization assistance unit 46 restricts the operator operation that will cause the center-of-gravity position to approach the bench edge 212, as assisting in the posture stabilization of the work machine 1.

[0083] Specifically, the stabilization assistance section 46 sets an upper limit of an operation amount of the operation that will cause the center-of-gravity position to approach the bench edge 212, and notifies the action control section 47 of the set upper limit. The action control section 47 generates a control command by keeping the operation amount of the operation that will cause the center-of-gravity position to approach the bench edge 212 equal to or below the upper limit notified by the stabilization assistance section 46, and outputs the control command to the proportional solenoid valve 51. Note that the upper limit of the operation amount may be zero. That is, the stabilization assistance section 46 may restrict the operation that will cause the center-of-gravity position to approach the bench edge 212 such that the operation is disabled.

[0084] Fig. 14 is a flowchart showing a process related to assisting in posture stabilization performed by the controller 40 shown in Fig. 13.

[0085] In the process shown in Fig. 14, step S17 and step S18 are added instead of step S7 to step S9 in the process shown in Fig. 8. That is, the controller 40 of the second embodiment proceeds to step S17 if the work machine 1 is in an inclined state and the distance between the bench edge 212 and the center-of-gravity position is less than or equal to the first threshold th1 (step S4: Yes). The controller 40 proceeds to step S17 if the distance between the bench edge 212 and the center-of-gravity position is predicted to be less than or equal to the second threshold th2 when the upper swing body 7 performs a swing action (step S6: Yes).

[0086] In step S17, the controller 40 restricts the operation that will cause the center-of-gravity position to approach the bench edge 212.

[0087] In step S18, the controller 40 causes the notification device 56 to issue an alert notifying that the operation that will cause the center-of-gravity position to approach the bench edge 212 is restricted. The controller 40 then ends the process shown in Fig. 14.

[0088] The work machine 1 of the second embodiment can prevent the center-of-gravity position from approaching the bench edge 212 by restricting the operation that will cause the center-of-gravity position to approach the bench edge 212, thereby more reliably ensuring the posture stability of the work machine 1. For example, in the situation shown in Fig. 9, if the operator performs a left swing operation and the upper swing body 7 performs a left swing action, depending on the posture of the front work device 2 and the weight of the excavated object, the center-of-gravity position of the work machine 1 may approach the bench edge 212 and the posture stability of the work machine 1 may decrease. In such a case, the work machine 1 of the second embodiment can prevent decrease in the posture stability of the work machine 1 since the left swing action is restricted. Therefore, the work machine 1 of the second embodiment can more reliably ensure the posture stability of the work machine 1 by taking into account the effect of the cliff-like terrain on the posture stability of the work machine 1.

[0089] Fig. 15 is a diagram illustrating an example of an alert issued by the notification device 56 shown in Fig. 13.

[0090] Fig. 15 shows an example of an alert issued in a situation in which a left swing action performed by the upper swing body 7 will cause the center-of-gravity position to approach the bench edge 212. The alert shown in Fig. 15 is an example of an alert notifying that the operation that will cause the center-of-gravity position to approach the bench edge 212 is restricted, and corresponds to the alert issued in step S18 of Fig. 14. By issuing such an alert, the work machine 1 can reliably allow the operator to recognize that an operation that reduces the posture stability of the work machine 1 is restricted, thereby reducing the discomfort felt by the operator due to the operation restriction.[Third Embodiment]

[0091] A work machine 1 according to a third embodiment will be described using Fig. 16 and Fig. 17. In the work machine 1 according to the third embodiment, descriptions of components that are the same as those in the second embodiment will be omitted.

[0092] Fig. 16 is a block diagram illustrating the functional configuration of the controller 40 according to the third embodiment. Fig. 17 is a graph illustrating a relationship between a threshold changed by the stabilization assistance section 46 shown in Fig. 16 and soil property information.

[0093] The work machine 1 of the third embodiment further includes a soil property acquisition device 57 that acquires soil property information around the work machine 1, including the bench edge 212. The soil property information may include information related to the hardness of the ground around the work machine 1. The information related to the hardness of the ground may be information indicating the ground hardness itself. Alternatively, the information related to the hardness of the ground may be information indicating parameters that affect the hardness of the ground, such as the moisture content of the ground, the type of ground (sand, sandy soil, gravel, clayey soil, ore, etc.), the particle size of the ground, or the specific gravity of the ground. The soil property acquisition device 57 may be configured as a receiver that receives soil property information around the work machine 1 from outside the work machine 1 (for example, a control system, etc.). Alternatively, the soil property acquisition device 57 may acquire soil property information by detecting resistance generated in the bucket 10 during the excavation operation of the front work device 2. Alternatively, the soil property acquisition device 57 may have an imaging device that captures images of the excavated object, and acquire soil property information from the images of the excavated object captured by the imaging device. The soil property acquisition device 57 may acquire soil property information when the work machine 1 starts working, or may acquire soil property information in real time while the work machine 1 is working.

[0094] The stabilization assistance section 46 of the third embodiment changes the threshold (at least one of the first threshold th1 and the second threshold th2) used when determining the distance between the bench edge 212 and the center-of-gravity position, in accordance with the soil property information acquired by the soil property acquisition device 57. For example, as shown in Fig. 12, in the stabilization assistance section 46, a map showing the relationship between the ground hardness and the threshold is set in advance. This map may show a relationship in which the threshold decreases as the ground hardness increases, and becomes a constant value after a certain level of the ground hardness. The stabilization assistance section 46 estimates the hardness of the ground from the soil property information acquired by the soil property acquisition device 57. The stabilization assistance section 46 refers to the map shown in Fig. 12, identifies the threshold corresponding to the estimated hardness of the ground, and sets the identified threshold. In this way, the stabilization assistance section 46 can change the threshold.

[0095] As a result, the work machine 1 of the third embodiment can change the conditions for starting the assisting in the posture stabilization of the work machine 1 in accordance with the surrounding soil property information, thereby reliably ensuring the posture stability of the work machine 1 while further reducing the discomfort felt by the operator due to the alert issuance or the operation restriction.[Fourth Embodiment]

[0096] A work machine 1 according to a fourth embodiment will be described using Fig. 18. In the work machine 1 according to the fourth embodiment, descriptions of components that are the same as those in the first to third embodiments will be omitted.

[0097] Fig. 18 is a diagram illustrating a remote operation device 300 that operates the work machine 1 according to the fourth embodiment.

[0098] The work machine 1 of the fourth embodiment is operated by the remote operation device 300 located in a remote location away from the work machine 1. The remote operation device 300 includes a wireless communication device 301 that communicates wirelessly with a communication device 60 of the work machine 1, a remote operation lever 302 that is operated by an operator in the remote location, and a display 303 that displays the terrain around the work machine 1.

[0099] The operator in the remote location can operate the remote operation lever 302 to move the work machine 1 while viewing the terrain around the work machine 1 displayed on the display 303. Operation information of the remote operation lever 302 by the operator is transmitted from the wireless communication device 301 to the communication device 60 of the work machine 1. The communication device 60 of the work machine 1 receives the operation information transmitted from the wireless communication device 301 of the remote operation device 300 and outputs it to the controller 40. The controller 40 controls the work machine 1 in accordance with the operation information transmitted from the wireless communication device 301 of the remote operation device 300.

[0100] In such a remotely operated work machine 1, the controller 40 assists in the posture stabilization of the work machine 1, similar to the first to third embodiments, if the distance between the bench edge 212 and the center-of-gravity position is equal to or less than the threshold. As a result, the work machine 1 of the fourth embodiment, similar to the first to third embodiments, can ensure the posture stability of the work machine 1 by taking into account the effect of the cliff-like terrain on the posture stability of the work machine 1.

[0101] Furthermore, when restricting the operation that will cause the center-of-gravity position to approach the bench edge 212, the remote operation device 300 can apply to the remote operation lever 302 a force (reaction force) that acts in a direction opposite to the operation direction of the remote operation lever 302. As a result, in the fourth embodiment, it is possible to reliably allow the operator to recognize that an operation that reduces the posture stability of the work machine 1 is restricted while reliably ensuring the posture stability of the work machine 1, thereby reducing the discomfort felt by the operator due to the operation restriction. Note that instead of the above-mentioned reaction force, the remote operation device 300 may apply vibrations or the like to the remote operation lever 302 to stimulate the operator's tactile sense.

[0102] It should be noted that the present invention is not limited to the aforementioned embodiments, and includes a variety of modifications. For example, although the aforementioned embodiments have been described in detail to clearly illustrate the present invention, the present invention need not include all of the components described. It is possible to replace a part of components of an embodiment with a component of another embodiment, and it is also possible to add, to components of an embodiment, a component of another embodiment. Further, it is also possible to, for a part of components of each embodiment, add, remove, or substitute a component of another embodiment.

[0103] Some or all of the aforementioned components, functions, processing sections, processing means, and the like may be implemented in hardware, for example, by designing them as an integrated circuit. Alternatively, each component, function, and the like may be implemented in software by a processor that analyzes and executes a program implementing each function. Information such as programs implementing each function, tables, and files may be stored in a recording device, such as memory, a hard disk, or a SSD (solid state drive), or in a recording medium, such as an IC card, an SD card, or a DVD.

[0104] In addition, the control lines and information lines shown are those considered necessary for description and do not necessarily represent all control lines and information lines required in a product. In practice, almost all components may be interconnected.Reference Signs List

[0105] 1Work machine 2Front work device (work device) 5Lower traveling body 7Upper swing body 21Crawler 40Controller 44Cliff determination section 45Center-of-gravity calculation section 46Stabilization assistance section 52Operation detection device 53Posture detection device 54Surrounding detection device 56Notification device 57Soil property acquisition device 60Communication device 212Bench edge (cliff edge) 300Remote operation device 302Remote operation lever

Claims

1. A work machine including a lower traveling body and an upper swing body provided swingably to the lower traveling body, the work machine comprising: a posture detection device that detects an inclination angle of the work machine and a swing angle of the upper swing body; a surrounding detection device that detects a terrain around the work machine; and a controller that controls the work machine, wherein the controller includes: a cliff determination section that determines whether a cliff edge exists around the work machine based on a detection result of the surrounding detection device; a center-of-gravity calculation section that calculates a center-of-gravity position of the work machine based on a detection result of the posture detection device; and a stabilization assistance section that assists in posture stabilization of the work machine, wherein if a distance between the cliff edge determined by the cliff determination section and the center-of-gravity position calculated by the center-of-gravity calculation section is equal to or less than a preset threshold, the stabilization assistance section causes a notification device of the work machine to issue an alert or restricts an operator operation that will cause the center-of-gravity position to approach the cliff edge, as assisting in the posture stabilization.

2. The work machine according to claim 1, wherein the stabilization assistance section determines whether the work machine is in an inclined state that causes a change in the distance between the cliff edge and the center-of-gravity position, based on the inclination angle detected by the posture detection device and the center-of-gravity position calculated by the center-of-gravity calculation section, and if the work machine is in an inclined state and the distance between the cliff edge and the center-of-gravity position is less than or equal to a first threshold, assists in the posture stabilization.

3. The work machine according to claim 1, further comprising: an articulated work device attached rotatably to the upper swing body and including a boom, an arm, and a bucket; a weight acquisition device that acquires weight of an excavated object held in the bucket; and an operation detection device that detects operation information for each of the work device and the upper swing body, wherein the posture detection device further detects a rotation angle of each joint of the work device, wherein based on the operation information detected by the operation detection device, the inclination angle, the swing angle, and the rotation angle detected by the posture detection device, and the weight acquired by the weight acquisition device, the center-of-gravity calculation section predicts a movement direction of the center-of-gravity position in accordance with the operation information, and wherein the stabilization assistance section predicts the distance between the cliff edge and the center-of-gravity position based on the movement direction predicted by the center-of-gravity calculation section, and if the predicted distance between the cliff edge and the center-of-gravity position is less than or equal to a second threshold, assists in the posture stabilization.

4. The work machine according to claim 3, wherein the operation detection device detects the operation information for a swing operation performed on the upper swing body, wherein the center-of-gravity calculation section predicts the movement direction when the upper swing body performs a swing action in accordance with the operation information for the swing operation, and wherein the stabilization assistance section predicts the distance between the cliff edge and the center-of-gravity position when the swing action is performed, based on the movement direction predicted by the center-of-gravity calculation section.

5. The work machine according to claim 1, wherein the lower traveling body includes a crawler, and wherein the stabilization assistance section sets, as different values, the threshold for determining the distance between the cliff edge that exists in a direction of travel of the crawler and the center-of-gravity position, and the threshold for determining the distance between the cliff edge that exists in a left-right direction of the crawler and the center-of-gravity position.

6. The work machine according to claim 1, further comprising a soil property acquisition device that acquires soil property information around the work machine, wherein the stabilization assistance section changes the threshold in accordance with the soil property information acquired by the soil property acquisition device.

7. The work machine according to claim 1, wherein as the alert, the stabilization assistance section causes the notification device to issue at least one of an alert notifying content of the operation that will cause the center-of-gravity position to approach the cliff edge, and an alert warning that the operation that will cause the center-of-gravity position to approach the cliff edge has been performed.

8. The work machine according to claim 1, wherein the stabilization assistance section sets an upper limit of an operation amount of the operation as restriction of the operation that will cause the center-of-gravity position to approach the cliff edge.

9. The work machine according to claim 8, wherein the stabilization assistance section causes the notification device to issue an alert notifying that the operation that will cause the center-of-gravity position to approach the cliff edge is restricted.

10. The work machine according to claim 1, further comprising a communication device that communicates wirelessly with a remote operation device, wherein the communication device receives operation information transmitted from the remote operation device and outputs the operation information to the controller, and wherein the controller controls the work machine in accordance with the operation information transmitted from the remote operation device.

11. The work machine according to claim 10, wherein the remote operation device includes a remote operation lever, and when restricting the operation that will cause the center-of-gravity position to approach the cliff edge, applies to the remote operation lever a force that acts in a direction opposite to an operation direction of the remote operation lever.

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