Work machine

Abstract

To provide a work machine capable of performing a return operation that achieves both a shortened time to reach an excavation position and a reduced possibility of damage to a work tool due to contact with surrounding objects.SOLUTION: A work machine 1 comprises a control device 60 that controls a return operation that moves a bucket 10 of a front work mechanism 2 toward an excavation start position. The control device 60 sets whether or not the bucket 10 can come into contact with surrounding objects detected by a surrounding object detection device 26, and operates an upper rotating body 5 and the front work mechanism 2 so as to perform a return operation while allowing contact of the bucket 10 with respect to surrounding objects that have been set as contactable.SELECTED DRAWING: Figure 11

Description

[Technical field]

[0001] The present invention relates to a work machine including an articulated working device for performing work and a rotatable body to which the working device is attached. [Background technology]

[0002] Some working machines, such as hydraulic excavators, have a multi-jointed working device attached to a rotatable rotating body. The working device is composed of, for example, a boom attached to the rotating body so as to be rotatable in the vertical direction, an arm attached to the boom so as to be rotatable, and a bucket as a working tool attached to the arm so as to be rotatable.

[0003] A work machine configured in this way performs an excavation and loading operation of soil by, for example, repeating an excavation operation in which the work device excavates soil and sand, a transport operation in which the excavated soil and sand are transported to the top of the bed of the loaded machine such as a dump truck, an earth-discharging operation in which the excavated soil and sand are discharged onto the bed of the loaded machine, and a return operation in which the bucket after earth-discharging is moved to the excavation start position in sequence. When performing such excavation and loading operation, objects such as land near the excavation target and the loaded machine are present around the work machine. Therefore, in excavation and loading operation, it is necessary to consider the contact of the bucket with surrounding objects during the return operation in which the bucket is moved to the excavation start position.

[0004] The technology described in Patent Document 1 is known as a method for moving a work machine that takes into consideration contact of the work machine with objects present around the work machine. The path setting system described in Patent Document 1 sets a target path for an attachment (bucket) of a work machine. When it is determined that a specific obstacle exists between the start point and end point of the target path, the path setting system is configured to set an avoidance path in which the attachment performs an avoidance operation to avoid the obstacle, whereas when it is determined that no specific obstacle exists, the path setting system sets a non-avoidance path in which the attachment does not perform an avoidance operation. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2022-71693 A Summary of the Invention [Problem to be solved by the invention]

[0006] Consider the case where the technology described in Patent Document 1 is applied to the return operation of the above-mentioned work machine. In the technology described in Patent Document 1, anything that may come into contact with the bucket (attachment) when the bucket moves is considered as an obstacle. Therefore, it is possible to prevent damage caused by contact with an object during the return operation of the bucket. However, the top of a mountain-shaped pile of earth and sand is also considered as an obstacle. For this reason, if the top of the pile of earth and sand (a specific part of an obstacle) is located near (for example, directly above) the excavation start position, which is the end point of the target path in the return operation, an avoidance path is set to avoid the top of the pile of earth and sand, and the bucket moves on the avoidance path. As a result, it takes time for the bucket, which is a working tool, to reach the excavation start position, and it is considered that the work efficiency will decrease. From the viewpoint of work efficiency in the return operation, it is necessary to reconsider the idea of ​​considering everything that may come into contact with the bucket as an obstacle. For example, even if the bucket comes into contact with the pile of earth and sand, the possibility of the bucket being damaged by the contact is extremely low.

[0007] The present invention has been made based on the above-mentioned considerations, and its object is to provide a work machine that can perform a return movement that achieves both a shorter arrival time to the excavation position and a reduced possibility of damage to the work implement due to contact with surrounding objects. [Means for solving the problem]

[0008] The present application includes a plurality of means for solving the above-mentioned problems. For example, in a work machine including a rotatable rotating body, a multi-jointed working device attached to the rotating body so as to be rotatable in the vertical direction and having a working tool, a surrounding object detection device for detecting objects including the terrain existing around the rotating body, and a control device for controlling the rotating body and the working device, the control device is configured to control a return operation of moving the working tool toward an excavation start position where the working tool starts excavation of an excavation target, the control device sets whether or not the working tool can come into contact with surrounding objects detected by the surrounding object detection device, and operates the rotating body and the working device so as to perform the return operation while allowing the working tool to come into contact with surrounding objects set as contactable among the surrounding objects. Effect of the Invention

[0009] According to one example of the present invention, a return motion that allows the tool to come into contact with a surrounding object that is set to be contactable can shorten the path to the excavation position compared to a return motion that avoids contact with the surrounding object. In this case, the possibility of damage to the tool can be reduced by setting whether or not the tool can come into contact with the surrounding object according to the possibility of damage to the tool. In other words, a return motion that achieves both a shortened time to reach the excavation position and a reduced possibility of damage to the tool due to contact with the surrounding object can be performed. Problems, configurations and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is an external view showing a hydraulic excavator as a work machine according to a first embodiment of the present invention and a dump truck as a machine to be loaded in a loading operation of the hydraulic excavator. [Diagram 2] 1 is a configuration diagram showing a hydraulic system and a control system for the hydraulic system in a work machine according to a first embodiment. [Diagram 3]3 is a block diagram showing functions of a control device for the work machine according to the first embodiment shown in FIG. 2. [Figure 4] FIG. 2 is an explanatory diagram showing information defining the attitude of the hydraulic excavator together with the plane of the XZ axes of a reference coordinate system set in the work machine according to the first embodiment. [Diagram 5] FIG. 2 is an explanatory diagram showing information defining the attitude of the hydraulic excavator together with the plane of the XY axes of a reference coordinate system set in the work machine according to the first embodiment. [Figure 6] 4 is an explanatory diagram showing an example of a method for setting contact characteristics by a surrounding object characteristic setting unit in the control device for the work machine according to the first embodiment shown in FIG. 3. [Figure 7] 4 is an explanatory diagram showing an example of a method for setting an entry-prohibited area by an evaluation function setting unit in the control device for the work machine according to the first embodiment shown in FIG. 3. [Figure 8] 8 is a diagram illustrating the entry-forbidden area shown in FIG. 7 in a reference coordinate system. [Figure 9A] 4 is a diagram showing a first example of weights (coefficients of a penalty function) for a penalty cost set by an evaluation function setting unit in the control device for the work machine according to the first embodiment shown in FIG. 3. FIG. [Figure 9B] 7 is a diagram showing a second example of the weighting on the penalty cost (coefficient of the penalty function) set by the evaluation function setting unit in the control device for the work machine according to the first embodiment shown in FIG. 3. FIG. [Figure 10] 4 is an explanatory diagram showing an example of a part of a bucket that is to be moved in an optimization calculation of an evaluation function in the control device for the work machine according to the first embodiment shown in FIG. 3. [Figure 11] 4 is a flowchart showing an example of a control procedure for a return motion by the control device of the work machine according to the first embodiment shown in FIG. 3. [Figure 12] FIG. 2 is an explanatory diagram showing a bucket path in a case where there is no surrounding terrain (surrounding object) that will come into contact with the bucket during a return operation of the work machine according to the first embodiment. [Figure 13]FIG. 11 is an explanatory diagram showing an example of a bucket path when there is a surrounding terrain (surrounding object) that may come into contact with the bucket during a return motion. [Figure 14] FIG. 2 is an explanatory diagram showing a bucket path when a surrounding terrain (surrounding object) for which contact characteristics forbidding contact are set is present during a return operation of the work machine according to the first embodiment. [Figure 15] FIG. 2 is an explanatory diagram showing a bucket path in a case where a surrounding terrain (surrounding object) exists for which contact characteristics are set that allow contact during a return operation of the work machine according to the first embodiment. [Figure 16] FIG. 4 is an explanatory diagram showing a bucket path from the end of an earth-discharging operation onto a loaded machine during a return operation of the work machine according to the first embodiment. [Figure 17] FIG. 5 is a block diagram showing the functions of a control device in a work machine according to a second embodiment of the present invention. [Figure 18] FIG. 13 is an explanatory diagram showing a case where the excavation target contains minerals and there is surrounding terrain (surrounding objects) that may come into contact with the bucket during the return motion. [Figure 19] FIG. 11 is a block diagram showing functions of a control device in a work machine according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a working machine according to the present invention will be described with reference to the drawings. In this embodiment, a hydraulic excavator will be described as an example of a working machine.

[0012] [First embodiment] First, the configuration of a hydraulic excavator as a work machine according to the first embodiment will be described with reference to Fig. 1. Fig. 1 is an external view showing a hydraulic excavator as a work machine according to the first embodiment of the present invention and a dump truck as a machine to be loaded in a loading operation of the hydraulic excavator. Here, the description will be given using the direction as seen by an operator seated in the driver's seat of the hydraulic excavator.

[0013] 1, a hydraulic excavator 1 as a work machine is a type of loader that loads objects onto a machine to be loaded 100. The machine to be loaded 100 is, for example, a transport vehicle such as a dump truck, and is equipped with a tray (cargo platform) 101. The hydraulic excavator 1 performs excavation and loading work, and repeats a series of actions including an excavation action for excavating a surface to be excavated such as the ground, a transport action for transporting the excavated material (object to be loaded) such as excavated soil and sand onto the tray 101 of the machine to be loaded 100, an earth-discharging action for discharging the excavated material onto the tray 101, and a return action for performing the next excavation.

[0014] The hydraulic excavator 1 is made up of a machine body 3 and an articulated front working mechanism 2 that is attached to the machine body 3 so as to be rotatable in the vertical direction. The machine body 3 is made up of a self-propelled lower running body 4 and an upper rotating body 5 that is mounted on the lower running body 4 so as to be rotatable via a rotating device 6.

[0015] The front working mechanism 2 is configured by connecting a plurality of driven members so that they can rotate in the up-down direction or the front-back direction. The plurality of driven members are configured, for example, by a boom 8, an arm 9, and a bucket 10 as a working tool for excavation work. The boom 8 is connected to the front of the upper rotating body 5 via a boom pin 8a (see FIG. 4 described later) so that it can rotate in the up-down direction. The arm 9 is connected to the tip of the boom 8 via an arm pin 9a so that it can rotate in the front-back direction. The bucket 10 is located at the tip of the front working mechanism 2, and is connected to the tip of the arm 9 via a bucket pin 10a and a bucket link 10b so that it can rotate in the up-down direction or the front-back direction. The boom 8, the arm 9, and the bucket 10 are driven to rotate by the extension and contraction of a boom cylinder 11, an arm cylinder 12, and a bucket cylinder 13, which are hydraulic actuators, respectively.

[0016] The lower traveling body 4 includes, for example, a crawler type traveling device 15. The traveling device 15 is driven by a left traveling hydraulic motor 16a and a right traveling hydraulic motor 16b (see FIG. 2 described later) which are hydraulic actuators. The left traveling hydraulic motor 16a and the right traveling hydraulic motor 16b may be collectively referred to as traveling hydraulic motors 16.

[0017] The upper rotating body 5 is configured to be driven to rotate relative to the lower traveling body 4 by, for example, a swing hydraulic motor 7 of a swing device 6 which is a hydraulic actuator. The upper rotating body 5 includes an operator's cab 18 in which an operator sits, and a machine room 19 which houses various devices. An operation device 50 (see FIG. 2 described later) for operating the multiple hydraulic actuators 7, 11, 12, 13, 16 is disposed in the operator's cab 18. The configuration of the operation device 50 will be described in detail later. In the machine room 19, various devices constituting a hydraulic system 30 (see FIG. 2 described later), such as a prime mover 31 and a hydraulic pump 32, are disposed.

[0018] A rotation angle sensor 21 that detects the rotation angle of the upper rotating body 5 relative to the lower running body 4 and a rotation angular velocity sensor 22 that detects the rotation angular velocity of the upper rotating body 5 (both see FIG. 2 described later) are attached to the rotating device 6 and the upper rotating body 5, respectively. The rotation angular velocity sensor 22 is formed, for example, by an inertial measurement unit (IMU), and can detect the pitch angle and roll angle of the upper rotating body 5 (airframe 3) relative to a reference plane such as a horizontal plane.

[0019] Angle sensors are attached to the boom 8, arm 9, and bucket 10 of the front working mechanism 2, respectively. Specifically, a boom angle sensor 23 (see FIG. 2, described later) that detects the rotation angle of the boom 8 relative to the upper rotating structure 5 (boom rotation angle) is attached to the boom pin 8a (see FIG. 4, described later). An arm angle sensor 24 (see FIG. 2, described later) that detects the rotation angle of the arm 9 relative to the boom 8 (arm rotation angle) is attached to the arm pin 9a. A bucket angle sensor 25 (see FIG. 2, described later) that detects the rotation angle of the bucket 10 relative to the arm 9 (bucket rotation angle) is attached to the bucket link 10b.

[0020] The swing angle sensor 21, swing angular velocity sensor 22, boom angle sensor 23, arm angle sensor 24, and bucket angle sensor 25 constitute a posture detection device 20 (see FIG. 2 described later) that detects the swing angle of the upper swing structure 5 and each rotation angle of the front working implement 2. The sensors 21, 22, 23, 24, and 25 that constitute the posture detection device 20 output detection information to a control device 60 described later.

[0021] The rotation angles of the boom 8, arm 9, and bucket 10 can be obtained by detecting the angles of the boom 8, arm 9, and bucket 10 relative to a reference plane such as a horizontal plane using an inertial measurement unit (IMU) and converting the detection values ​​of the inertial measurement unit into the rotation angles. The rotation angles of the boom 8, arm 9, and bucket 10 can also be obtained by detecting the strokes of the boom cylinder 11, arm cylinder 12, and bucket cylinder 13 using a stroke sensor and converting the detection values ​​of the stroke sensors into the rotation angles.

[0022] A surrounding object detection device 26 is attached to the upper rotating body 5 (e.g., the cab 18) to detect information on objects (hereinafter, sometimes referred to as surrounding objects) present around the hydraulic excavator 1. The surrounding object detection device 26 can detect, for example, the loaded machine 100 that is the target of the loading work of the hydraulic excavator 1, other work machines, or people. In the present embodiment, the surrounding objects detected by the surrounding object detection device 26 include the terrain (hereinafter, sometimes referred to as surrounding terrain) present around the hydraulic excavator 1, for example, the terrain of the land to be excavated and the land in the vicinity of the excavation target. The surrounding object detection device 26 can detect information on the position and shape of the surrounding objects, and can be configured with, for example, a stereo camera or LiDAR (Light Detection And Ranging). The surrounding object detection device 26 can also be configured with a plurality of devices capable of detecting surrounding objects.

[0023] Next, the configuration of the hydraulic system and the control system in the work machine according to the first embodiment will be described with reference to Fig. 2. Fig. 2 is a configuration diagram showing the hydraulic system and the control system of the hydraulic system in the work machine according to the first embodiment.

[0024] 2, the hydraulic excavator 1 is equipped with a hydraulic system 30 that hydraulically drives the front working implement 2, the lower traveling body 4, and the upper rotating body 5 (all see FIG. 1). The hydraulic system 30 is equipped with a prime mover 31 which is an engine or an electric motor, a hydraulic pump 32 driven by the prime mover 31, and a plurality of hydraulic actuators driven by pressure oil supplied from the hydraulic pump 32. The hydraulic pump 32 is, for example, a variable displacement pump. The plurality of hydraulic actuators include a swing hydraulic motor 7, a boom cylinder 11, an arm cylinder 12, a bucket cylinder 13, a left traveling hydraulic motor 16a, and a right traveling hydraulic motor 16b.

[0025] Each of the hydraulic actuators 7, 11, 12, 13, 16a, 16b is connected to the hydraulic pump 32 via a flow control valve 33. The flow control valve 33 controls the flow rate and direction of pressure oil supplied from the hydraulic pump 32 to each of the hydraulic actuators 7, 11, 12, 13, 16a, 16b, and is, for example, a collection of spool valves corresponding to each of the hydraulic actuators 7, 11, 12, 13, 16a, 16b. The flow control valve 33 is driven in response to an input pilot pressure, and is connected to a pilot pump 35, which is a pilot hydraulic source, via a pilot line 36. The pilot pump 35 is driven by, for example, the prime mover 31.

[0026] On the pilot line 36, electromagnetic proportional valves 41a, 41b, 42a, 42b, 43a, 43b, 44a, 44b, 45a, 45b, 46a, 46b are provided to generate pilot pressures to be input to spool valves corresponding to the hydraulic actuators 7, 11, 12, 13, 16a, 16b of the flow control valve 33. Each of the electromagnetic proportional valves 41a, 41b to 46a, 46b generates pilot pressures according to drive commands from a control device 60, which will be described later. The electromagnetic proportional valves 41a, 41b generate pilot pressures to be input to spool valves corresponding to the swing hydraulic motor 7. The electromagnetic proportional valves 42a, 42b generate pilot pressures to be input to spool valves corresponding to the arm cylinder 12. The electromagnetic proportional valves 43a, 43b generate pilot pressures to be input to spool valves corresponding to the boom cylinder 11. The electromagnetic proportional valves 44a, 44b generate pilot pressures to be input to the spool valves corresponding to the bucket cylinder 13. The electromagnetic proportional valves 45a, 45b generate pilot pressures to be input to the spool valves corresponding to the left traveling hydraulic motor 16a. The electromagnetic proportional valves 46a, 46b generate pilot pressures to be input to the spool valves corresponding to the right traveling hydraulic motor 16b.

[0027] The hydraulic system 30 is configured to be controlled by a control device 60 in response to operation of an operating device 50 by an operator of the hydraulic excavator 1 .

[0028] The operating device 50 commands the operations of the front working implement 2, the lower traveling body 4, and the upper rotating body 5 (all see FIG. 1). The operating device 50 includes, for example, a left operating lever 51 for operating the swing hydraulic motor 7 and the arm cylinder 12, a right operating lever 52 for operating the boom cylinder 11 and the bucket cylinder 13, a left traveling operating lever 53 for operating the left traveling hydraulic motor 16a, and a right traveling operating lever 54 for operating the right traveling hydraulic motor 16b. The left operating lever 51 and the right operating lever 52 can also be configured to include, for example, an operating switch (not shown) for instructing the execution of a return operation performed during excavation and loading work of the hydraulic excavator 1.

[0029] The operation device 50 is, for example, an electric operation lever device, and has an operation information detection device that detects the operation direction (tilt direction) and operation amount (tilt amount) as operation information of the operation lever. The operation information detection device includes, for example, first operation detectors 51a and 51b that detect the operation of the left operation lever 51, second operation detectors 52a and 52b that detect the operation of the right operation lever 52, a third operation detector 53a that detects the operation of the left travel operation lever 53, and a fourth operation detector 54a that detects the operation of the right travel operation lever 54. Each of the operation detectors 51a, 51b, 52a, 52b, 53a, and 54a is, for example, composed of a rotary encoder or a potentiometer. The operation device 50 outputs the operation information detected by each of the operation detectors 51a, 51b, 52a, 52b, 53a, and 54a to the control device 60.

[0030] The control device 60 is electrically connected to the operation detectors 51a, 51b, 52a, 52b, 53a, and 54a of the operation device 50, and receives operation information of the operation device 50 detected by the operation detectors 51a, 51b, 52a, 52b, 53a, and 54a. The control device 60 is electrically connected to the sensors 21, 22, 23, 24, and 25 constituting the attitude detection device 20, and receives detection information (attitude information of the hydraulic excavator 1) of the sensors 21 to 25 of the attitude detection device 20. The control device 60 is also electrically or communicatively connected to the surrounding object detection device 26, and receives detection information of the surrounding object detection device 26.

[0031] Furthermore, an excavation start position setting device 27 is electrically or communicatively connected to the control device 60. The excavation start position setting device 27 sets an excavation start position, which is a position where the front working implement 2 starts excavating the excavation target, and can be configured to set the excavation start position based on the operation of the operator of the hydraulic excavator 1, for example. Specifically, the excavation start position setting device 27 can be configured to display the surrounding terrain photographed by the surrounding object detection device 26 on a display device that also serves as an input device 28 (see the configuration indicated by dashed lines in FIG. 3 described later) including a touch panel, and to instruct the setting of the excavation start position by the operator's touch operation or button operation on the display screen of the display device.

[0032] The control device 60 controls the driving of each hydraulic actuator 7, 11, 12, 13, 16a, 16b by outputting drive commands corresponding to operation information from the operating device 50 to the electromagnetic proportional valves 41a, 41b to 46a, 46b of the hydraulic system 30. This makes it possible to execute various operations such as the swing operation of the upper swing body 5, the rotation operation of the front working mechanism 2, and the traveling operation of the lower traveling body 4.

[0033] For example, the control device 60 outputs a drive command corresponding to the operation information of the left operation lever 51 to the electromagnetic proportional valves 41a and 41b, so that the swing hydraulic motor 7 rotates by supplying pressure oil to swing the upper swing body 5. By outputting a drive command corresponding to the operation information of the left operation lever 51 to the electromagnetic proportional valves 42a and 42b, the arm cylinder 12 expands and contracts by supplying pressure oil to swing the arm 9. Also, by outputting a drive command corresponding to the operation information of the right operation lever 52 to the electromagnetic proportional valves 43a and 43b, the boom cylinder 11 expands and contracts by supplying pressure oil to swing the boom 8. By outputting a drive command corresponding to the operation information of the right operation lever 52 to the electromagnetic proportional valves 44a and 44b, the bucket cylinder 13 expands and contracts by supplying pressure oil to swing the bucket 10. By outputting drive commands corresponding to operation information of the left traveling operation lever 53 and the right traveling operation lever 54 to the electromagnetic proportional valves 45a, 45b, 46a, 46b, the left traveling hydraulic motor 16a and the right traveling hydraulic motor 16b are rotated by the supply of pressurized oil, causing the lower traveling body 4 to travel.

[0034] Incidentally, even if the operating device 50 is not operated, the control device 60 can drive the hydraulic actuators 7, 11, 12, 13, 16a, and 16b by outputting control commands for automatic control or semi-automatic control to the electromagnetic proportional valves 41a, 41b to 46a, and 46b.

[0035] The control device 60 includes, as a hardware configuration, an interface 61 (hereinafter sometimes referred to as I / F) for transmitting and receiving information to and from external devices, an internal storage device 62 made of RAM, ROM, etc., and a processing device 63 made of CPU, MPU, etc. The I / F 61 is configured to take in, for example, information from the operation device 50, the attitude detection device 20, and the surrounding object detection device 26, and to output control signals to the electromagnetic proportional valves 41a, 41b to 46a, 46b. The internal storage device 62 stores in advance programs and various information required for controlling the return operation of the hydraulic excavator 1 during the excavation and loading work in this embodiment. The control device 60 is also connected to an external storage device 80 in which various information is stored. The processing device 63 appropriately reads programs and various information from the internal storage device 62 and the external storage device 80, appropriately takes in various information via the I / F 61, and executes processing according to the program, thereby realizing various functions for controlling the return operation. Details of the functional parts of the control device 60 in this embodiment will be described later.

[0036] Next, the functional configuration of the control device for the work machine according to the first embodiment will be described with reference to Figs. 3 to 6. Fig. 3 is a block diagram showing the functions of the control device for the work machine according to the first embodiment shown in Fig. 2. Fig. 4 is an explanatory diagram showing information defining the attitude of the hydraulic excavator together with the plane of the XZ axes of a reference coordinate system set in the work machine according to the first embodiment. Fig. 5 is an explanatory diagram showing information defining the attitude of the hydraulic excavator together with the plane of the XY axes of a reference coordinate system set in the work machine according to the first embodiment. Fig. 6 is an explanatory diagram showing an example of a method for setting contact characteristics by a surrounding object characteristic setting unit in the control device for the work machine according to the first embodiment shown in Fig. 3.

[0037] The control device 60 of this embodiment controls the return movement performed during excavation and loading work of the hydraulic excavator 1 by calculating control inputs for controlling the operation of each component of the front working mechanism 2 and the operation of the upper rotating body 5 based on the detection information (attitude information) from the attitude detection device 20, the detection information from the surrounding object detection device 26, and instructions from the excavation start position setting device 27. The control device 60 has an attitude calculation unit 71, a surrounding object position calculation unit 72, a surrounding object characteristic setting unit 73, an evaluation function setting unit 74, an optimization calculation unit 75, and an actuator control unit 76 as functional units for controlling the return movement of the hydraulic excavator 1.

[0038] In the control device 60, a reference coordinate system for specifying the positions and postures of the components of the hydraulic excavator 1, such as the front working device 2 and the upper rotating body 5, is set in advance as a premise for the calculation of each of the functional units 71 to 76. The reference coordinate system in this embodiment is defined as a right-handed coordinate system with an origin O at the intersection of the rotation axis 5a of the upper rotating body 5 and the ground G, as shown in, for example, Figs. 4 and 5. In addition, in this reference coordinate system, as shown in Fig. 4, the forward direction of the lower traveling body 4 is defined as the positive direction of the X-axis, and the direction extending upward from the rotation axis 5a is defined as the positive direction of the Z-axis. In addition, as shown in Fig. 5, the left direction perpendicular to both the X-axis and the Z-axis and facing the forward direction of the lower traveling body 4 (the positive direction of the X-axis) is defined as the positive direction of the Y-axis.

[0039] In addition, in this reference coordinate system, the rotation angle of the upper rotating body 5 is defined as 0 degrees when the front working implement 2 is parallel to the X-axis. When the rotation angle of the upper rotating body 5 is 0 degrees, the motion plane of the front working implement 2 is parallel to the XZ plane of the reference coordinate system. Furthermore, the lifting motion direction of the boom 8 is the positive direction of the Z-axis, and the dumping direction of the arm 9 and bucket 10 is also the positive direction of the X-axis.

[0040] The posture calculation unit 71 calculates the postures of the components of the hydraulic excavator 1, such as the front working mechanism 2 and the upper rotating body 5, in a reference coordinate system based on the detection information of the posture detection device 20. Specifically, the posture calculation unit 71 calculates the rotation angle θ of the boom 8 with respect to the X-axis based on the detection information of the boom angle sensor 23.Bm (FIG. 4). Based on the detection information of the arm angle sensor 24, the rotation angle θ Am (FIG. 4). Based on the detection information of the bucket angle sensor 25, the rotation angle θ Bk Based on the detection information of the rotation angle sensor 21, the attitude calculation unit 71 calculates the rotation angle θ of the upper rotating body 5 with respect to the X-axis (lower running body 4). Swg (Figure 5) is calculated.

[0041] The posture calculation unit 71 calculates the rotation angles θ of the respective components 8, 9, and 10 of the front working implement 2 as a result of the calculation. Bm , θ Am , θ Bk and the rotation angle θ of the upper rotating body 5 Swg and the dimensions L of each component of the front working mechanism 2 (the boom 8, the arm 9, and the bucket 10). Bm , L Am , L Bk Based on the above, the positions of the boom 8, arm 9, and bucket 10 on the XY plane and on the Z axis (height) are calculated. Bm is the length from the boom pin 8a to the arm pin 9a, and the dimension L of the arm 9 Am is the length from the arm pin 9a to the bucket pin 10a, and the dimension L of the bucket 10 Bk is the length from the bucket pin 10a to the tip of the bucket 10. For example, when the rotation angle is 0 degrees, the boom pin 8a is located at a position L in the positive direction of the X-axis from the rotation axis 5a. ox Each dimension is offset by L Bm , L Am , L Bk Information on the offset of the boom pin 8a is stored in advance, for example, in the internal storage device 62 (see FIG. 2).

[0042] The surrounding object position calculation unit 72 calculates the position in the reference coordinate system of the surrounding object detected by the surrounding object detection device 26 based on the detection information of the surrounding object detection device 26. The targets of the position calculation by the surrounding object position calculation unit 72 are the loaded machine 100, the excavation target, and the surrounding topography near the excavation target, which are detected by the surrounding object detection device 26.

[0043] The surrounding object characteristic setting unit 73 sets contact characteristics indicating the conditions (including the case of conditionally allowing) for whether or not contact with the front working implement 2 is allowed for the surrounding object detected by the surrounding object detection device 26. The surrounding object characteristic setting unit 73 can be configured to set the above-mentioned contact characteristics for the surrounding object detected by the surrounding object detection device 26 in response to an instruction from an HMI (Human Machine Interface) as an input device 28 (shown by a dashed line in FIG. 3 ) such as a touch panel operated by an operator. The surrounding object characteristic setting unit 73 can also be configured to determine the type or attribute of the surrounding object detected by the surrounding object detection device 26 based on the detection information of the surrounding object detection device 26, and to set the contact characteristics by itself in accordance with the type or attribute of the surrounding object as a result of the determination. Specifically, the surrounding object characteristic setting unit 73 determines the type and attribute of the surrounding object from, for example, the shape of the surrounding object obtained from the detection information of the surrounding object detection device 26. The types of surrounding objects are classified in advance, for example, machines other than the hydraulic excavator 1 such as the loaded machine 100, people, the surrounding terrain of the work site, the terrain of the travel route of the loaded machine 100, etc. The soil of the surrounding terrain can also be classified according to attributes such as soil that is softer than a certain value, soil located around minerals, etc. It is also possible to classify it as soil with unknown attributes.

[0044] The surrounding object characteristic setting unit 73 can set the contact characteristics as shown in Table 1 below, depending on the type and attribute of the surrounding object detected by the surrounding object detection device 26, for example.

[0045] [Table 1]

[0046] As shown in Table 1, when the surrounding object is a machine other than the hydraulic excavator 1 (including the loaded machine 100) or a person, a contact characteristic of no contact (X in Table 1) is set, indicating that contact with the bucket 10 is not permitted. This is to ensure the safety of the machine and people. Similarly, when the surrounding object is the topography of the travel path of the loaded machine 100 (surrounding topography), a contact characteristic of no contact is set. This is to avoid a situation in which the topography of the travel path of the loaded machine 100 is disturbed by contact with the bucket 10, thereby impairing the comfort of the travel of the loaded machine 100.

[0047] Furthermore, when the surrounding object is soil (surrounding terrain) near the excavation start position, for example, a contact characteristic is set to prohibit contact, indicating that contact with the front working implement 2 is not permitted under a first condition in which the bucket 10 moves with the upper rotating body 5 rotating, while a contact characteristic is set to permit contact with the bucket 10 (◯ in Table 1), indicating that contact with the bucket 10 is permitted under a second condition in which the bucket 10 moves with the operation of only the front working implement 2 without the upper rotating body 5 rotating. However, this contact characteristic setting is applied when the hardness (attributes) of the soil is unknown. This is desirable from the viewpoint of preventing the risk of damage to the bucket 10, which moves with the upper rotating body 5 rotating, due to contact with soil (surrounding terrain) of unknown attributes (hardness), and uneven wear of the tip of the bucket 10.

[0048] Furthermore, when the surrounding object is soil (surrounding terrain) near the excavation start position and minerals are present around the soil, the contact characteristic is set to prohibit contact under the first condition, as in the case of soil (surrounding terrain) with unknown attributes (hardness), while the contact characteristic is set to permit contact under the second condition. This is to prevent the bucket 10, which moves in conjunction with the rotation of the upper rotating body 5, from being deformed due to contact with the minerals.

[0049] On the other hand, when the surrounding object is soil (surrounding topography) near the excavation start position and the soil is softer than a predetermined value, the contact characteristics are set to allow contact under the above-mentioned second condition, and the contact characteristics are set to allow contact even when the upper rotating body 5 is rotating, or the contact characteristics are set to allow contact only when the rotation speed of the upper rotating body 5 is slower than a predetermined speed. This is because it is assumed that the bucket 10 will not be deformed or damaged even if the bucket 10 moving with the rotating or low-speed rotating operation comes into contact with soft soil, and is intended to prioritize shortening the time it takes for the bucket 10 to reach the excavation start position.

[0050] Also, as shown in FIG. 6, the surrounding object characteristic setting unit 73 can be configured to compare the shape of the surrounding terrain before the start of work and the shape during excavation work, which are obtained based on the detection information of the surrounding object detection device 26, and set a contact characteristic of contact permission indicating that contact with the bucket 10 is permitted for an area where the shape of the surrounding terrain during excavation work has changed from the shape before the start of work. It is assumed that the shape of the soil generated by the excavation work is included in the area where the shape of the surrounding terrain during excavation work has changed from the shape of the surrounding terrain before the start of work. Even if the bucket 10 comes into contact with the soil generated by the excavation work, it is unlikely that the bucket 10 will be damaged or worn out. Therefore, in this embodiment, the contact characteristic of contact permission is set for the surrounding terrain that is assumed to be the soil generated by the excavation work. This makes it possible to prioritize shortening the time it takes for the bucket 10 to reach the excavation start position.

[0051] The evaluation function setting unit 74 and the optimization calculation unit 75 use, for example, a framework of model predictive control (MPC) to calculate a control input for controlling the return operation of the hydraulic excavator 1. Model predictive control is a method of predicting the behavior of a controlled object (hydraulic excavator 1) for a finite time from the current time using dynamic characteristics (for example, an equation of motion or a transfer function model) of the controlled object, and calculating a control input that minimizes a specific evaluation function in that finite time interval (for details of model predictive control, see Introduction to Nonlinear Optimal Control, Toshiyuki Otsuka, Corona Publishing (2011)).

[0052] The evaluation function setting unit 74 sets an evaluation function to be used in the optimization calculation executed by the optimization calculation unit 75, based on the position information of the surrounding objects, which is the calculation result of the surrounding object position calculation unit 72, the contact characteristics of the surrounding objects set by the surrounding object characteristic setting unit 73, and the excavation start position (target value) set in response to an instruction from the excavation start position setting device 27. The optimization calculation unit 75 performs optimization calculation to minimize the evaluation function set by the evaluation function setting unit 74 in a prediction time interval from the current time to a finite time ahead, thereby calculating the control input of the front working implement 2 and the upper rotating body 5 for each control period. In the optimization calculation of the evaluation function, the attitude information of the front working implement 2 and the upper rotating body 5, which is the calculation result of the attitude calculation unit 71, is used as the control output of the current time to perform optimization calculation of the evaluation function for the prediction time interval, thereby calculating the control input of each time step in the prediction time interval. The optimization calculation unit 75 outputs the control input of the first time step among the control inputs of each time step in the prediction time interval, which is the calculation result, to the actuator control unit 76, as the control input of the current control period used for control of the return operation. The evaluation function set by the evaluation function setting unit 74 and used by the optimization calculation unit 75 will be described in detail later.

[0053] The actuator control unit 76 converts the calculation results of the optimization calculation unit 75 into command values ​​for realizing control inputs for the front working implement 2 and the upper rotating body 5, and outputs control signals corresponding to the command values ​​to each of the electromagnetic proportional valves 41a, 41b to 46a, 46b.

[0054] Next, the evaluation function used in the control device will be described with reference to Figs. 7 to 10. Fig. 7 is an explanatory diagram showing an example of a method for setting an intrusion-prohibited area by an evaluation function setting unit in the control device for a work machine according to the first embodiment shown in Fig. 3. Fig. 8 is a diagram showing the intrusion-prohibited area shown in Fig. 7 in a reference coordinate system. Fig. 9A is a diagram showing a first example of a weight for a penalty cost (coefficient of a penalty function) set by an evaluation function setting unit in the control device for a work machine according to the first embodiment shown in Fig. 3. Fig. 9B is a diagram showing a second example of a weight for a penalty cost (coefficient of a penalty function) set by an evaluation function setting unit in the control device for a work machine according to the first embodiment shown in Fig. 3. Fig. 10 is an explanatory diagram showing an example of a part of a bucket to be moved in an optimization calculation of an evaluation function in the control device for a work machine according to the first embodiment shown in Fig. 3.

[0055] In the model predictive control used in the evaluation function setting unit 74 and the optimization calculation unit 75, the dynamic characteristics (mathematical model) of the hydraulic excavator 1, which is the object to be controlled, are required as a premise for setting the evaluation function. It is possible to adopt an equation of motion as the dynamic characteristics of the return motion of the hydraulic excavator 1. In this case, for example, the upper rotating body 5 and the three components (boom 8, arm 9, bucket 10) of the hydraulic excavator 1 can be simulated by a four-link rigid body system. The equation of motion of this four-link rigid body system can be expressed by the following equation (1).

[0056]

number

[0057] In formula (1), θ and ω respectively indicate the angle and angular velocity (both of which correspond to the output) of each link, and τ indicates the drive torque (corresponding to the control input). In addition, the subscripts Swg, Bm, Am, and Bk of θ, ω, and τ respectively indicate the upper rotating body 5, the boom 8, the arm 9, and the bucket 10.

[0058] The operation of each link is realized by driving the hydraulic actuators, that is, the swing hydraulic motor 7, the boom cylinder 11, the arm cylinder 12, and the bucket cylinder 13. Therefore, the driving torque τ requires a conversion equation according to the pressure p of the pressure oil acting on the hydraulic actuators 711, 12, and 13, as shown in the following equation (2). Note that detailed explanations of equations (1) and (2) are omitted because they are not essential to the present invention.

[0059]

number

[0060] Moreover, instead of the equation of motion, it is also possible to adopt a transfer function of a delay system as the dynamic characteristics (mathematical model) of the return motion of the hydraulic excavator 1. In this case, for example, the motion of the three components (boom 8, arm 9, bucket 10) of the upper rotating body 5 and the front working implement 2 can be expressed by the following equation (3) as a delay system with respect to a speed command.

[0061]

number

[0062] In addition, y and x in equation (3) respectively indicate the speed output and the speed command value (corresponding to the control input). n are the Laplace operator, the damping ratio, and the natural angular frequency, respectively. Note that x in equation (3) and x in equation (1) are different variables.

[0063] Based on the above-mentioned dynamic characteristics, the evaluation function setting unit 74 sets an evaluation function for realizing a return movement that satisfies the conditions according to the calculation results of the surrounding object position calculation unit 72 and the contact characteristics of the surrounding object set by the surrounding object characteristic setting unit 73. The end position (target value) of the return movement is the excavation start position set by the excavation start position setting device 27.

[0064] Specifically, the evaluation function setting unit 74 sets, for example, the following formula (4) as the evaluation function J. Note that this evaluation function J is an example in which the dynamic characteristics (mathematical model) of the above formula (1) is adopted.

[0065]

number

[0066] Equation (4) is constructed using equations (4a), (4b), and (4c). Equation (4a) is the terminal cost φ, and equation (4b) is the stage cost L. Equation (4c) is the penalty cost P as a constraint condition. Note that K(x) in equations (4a), (4b), and (4c) is a function that converts the above-mentioned dynamic characteristic variable x into the position of the tip of the bucket 10. Also, y in equations (4a) and (4b) d is the end point (target value) of the return movement of the hydraulic excavator 1, and is the excavation start position set by the excavation start position setting device 27.

[0067] In both equations (4a) and (4b), K(x(t)), which indicates the tip position of the bucket 10 at time t, is calculated based on the digging start position y d In other words, a control input that moves the tip of the bucket 10 closer to the digging start position is generated by equations (4a) and (4b).

[0068] The penalty cost P in this embodiment is defined as the product of a penalty function F and a weight μp, as shown in equation (4c). The penalty function F is a function that outputs a large value only when the tip position of the bucket 10 enters an intrusion-prohibited area described below, and outputs zero when the tip position does not enter the intrusion-prohibited area. The weight μp is a function that is set so as to match the contact prohibition or contact permission condition of the contact characteristics set for the surrounding object.

[0069] The intrusion forbidden area is set according to the contact characteristics of the surrounding object set by the surrounding object characteristics setting unit 73. For example, when contact characteristics that prohibit contact are set for the surrounding object, the intrusion forbidden area is set to match the shape of the surrounding object or to surround the surrounding object. When contact characteristics that permit contact with conditions are set for the surrounding object, this is equivalent to the contact characteristics that prohibit contact when outside the range of the conditions, so an intrusion forbidden area similar to the above is set for the surrounding object. On the other hand, when contact characteristics that permit contact without conditions are set for the surrounding object, no intrusion forbidden area is set for the surrounding object.

[0070] For example, as shown in the upper diagram of FIG. 7, a situation is assumed in which soil and sand are present around the excavation start position. In this case, the soil and sand near the excavation start position is detected as the surrounding terrain. For the soil and sand near the excavation start position (surrounding terrain), for example, as shown in Table 1, when the hardness (attributes) of the soil and sand is unknown or when minerals are present in the vicinity, contact characteristics that prohibit contact are set under the condition that the upper rotating body 5 is in a rotating motion. Also, even if the surrounding terrain is softer than a predetermined value, contact with the bucket 10 is not permitted under the condition that the upper rotating body 5 is in a rotating motion at least at a predetermined speed or more.

[0071] Therefore, for the soil (surrounding terrain) near the excavation start position, an intrusion prohibition area is set so as to cover the soil, as shown in the lower diagram of Fig. 7. The intrusion prohibition area can be defined as a three-dimensional position in a reference coordinate system based on the position information of surrounding objects calculated by the surrounding object position calculation unit 72, as shown in Fig. 8, for example. When the intrusion prohibition area is set as shown in Fig. 8, the penalty function F is calculated based on the x coordinate of the tip position of the bucket 10. min x max Range to, Y coordinate y min From y max Range up to and including Z coordinate z min From z max Only when the tip position of the bucket 10 is within the range of the intrusion prohibited area, that is, when the tip position of the bucket 10 is within the range of the intrusion prohibited area, a large value is output.

[0072] The weight μp is determined according to the contact characteristics set for the surrounding object. For example, the weight μp is determined based on the rotation speed ω Swg is a function of .

[0073] For example, as described above, for soil and sand (surrounding terrain) near the excavation start position, when the attributes are unknown or when minerals are present in the surroundings, contact characteristics are set to prohibit contact when the upper rotating body 5 is rotating. Therefore, in the case of such surrounding terrain, the weight μp is set, for example, based on the rotation speed ω Swg is zero when the rotation speed ω of the upper rotating body 5 is zero. Swg is set to a value greater than zero when the weight μp is not zero. By setting the weight μp in this manner, even if the tip of the bucket 10 is in the intrusion-prohibited area and the penalty function F becomes a large value, the rotation speed ω Swg When is zero, that is, when only the front working implement 2 is operating, the weight μp becomes 0 and the penalty cost P shown in (Equation 4c) becomes 0. In other words, the penalty cost P in (Equation 4c) is a function that reflects the conditional contact prohibition contact characteristics.

[0074] Furthermore, when the soil (surrounding terrain) near the excavation start position is softer than a predetermined value, as described above, the contact characteristic is set to allow contact under the condition that the upper rotating body 5 is rotating at a speed slower than a predetermined speed. In other words, contact with the bucket 10 is not permitted under the condition that the upper rotating body 5 is rotating at a speed equal to or faster than a predetermined speed. In the case of such surrounding terrain, the weight μp is set to a value that is smaller than the rotation speed ω of the upper rotating body 5 as shown in FIG. 9A, for example. Swg becomes zero when the speed is lower than a predetermined speed ω0, while the turning speed ω Swg is set to be a constant value greater than zero when the rotation speed ω is equal to or greater than the predetermined speed ω0. By setting the weight μp in this manner, even if the tip of the bucket 10 is in the intrusion prohibited area and the penalty function F becomes a large value, the rotation speed ω Swgis slower than the predetermined speed ω0, the weight μp becomes 0, and the penalty cost shown in (Equation 4c) becomes 0. In other words, the penalty cost in (Equation 4c) is a function reflecting the contact characteristics that make contact prohibited under the condition that the upper rotating body 5 is rotating at a speed equal to or faster than the predetermined speed ω0. Note that the weight μp is calculated based on the rotation speed ω Swg is the given speed ω A It becomes zero at low speeds below, while the turning speed ω Swg is the given first speed ω A The value increases as the turning speed ω Swg is the given second speed ω B It is also possible to set it so that it becomes constant when the value exceeds this value.

[0075] The penalty cost P in (Equation 4c) is defined as the product of the penalty function F and the weight μp set in this manner. For this reason, when the tip of the bucket 10 enters the intrusion-prohibited area under specified conditions, the penalty cost P becomes the product of the penalty function F with a large value and the weight μp with a non-zero value, and the evaluation function J becomes a large value. Therefore, solutions in which the penalty cost P becomes a large value by optimizing the evaluation function J are excluded. In other words, when the weight μp is set as shown in FIG. 9A or FIG. 9B, the penalty cost P becomes large at the specified speed ω0 or ω B A control input is calculated so that the return operation is performed along a path that avoids the tip of the bucket 10, which is turning faster than the forward rotation speed, from entering the intrusion prohibited area. On the other hand, in a state where a turning operation is not being performed, a control input is calculated so that the return operation is performed along a path that does not take into account the intrusion prohibited area.

[0076] In this way, the evaluation function J is calculated by dividing the tip position of the bucket 10 by the excavation start position y d and a penalty cost P for moving the tip position away from the forbidden area under conditions according to the set contact characteristics.

[0077] Also, K(x) in each of the terms φ, L, and P indicating the evaluation function J in the above-mentioned equation (4) has been described as indicating the tip position of the bucket 10. However, as shown in Fig. 10, it is also possible to configure K(x) so that not only the tip (vertex A) of the bucket 10 but also each of the vertices A, B, and C of a polygon set to include the bucket 10 are set as the calculation target. In this case, a control input for the return operation is calculated to prevent not only the tip (vertex A) of the bucket 10 but also the bottom (vertex B and vertex C) of the bucket 10 from entering the intrusion prohibited area, so that it is possible to reliably avoid contact between the bucket 10 and a surrounding object for which a contact characteristic of contact prohibition is set.

[0078] Also, in the penalty cost P term of the evaluation function J, in addition to the function targeted at the tip position of the bucket 10, a function targeted at the geometric center (see FIG. 10) of the bucket 10 can be added. Specifically, the penalty cost P can be configured by combining the above formula (4c) and the following formula (4d).

[0079]

number

[0080] In equation (4d), Kg(x) indicates the geometric center position of the bucket 10, and μpg indicates a weight for the penalty function F related to the geometric center position of the bucket. The weight μpg in equation (4d) can be set to be larger than the weight μp in equation (4c), for example. Moreover, the weight μp in equation (4c) is set as shown in FIG. 9A, and μpg in equation (4d) is set to be larger than the rotation speed ω SwgIt is also possible to set it to a value greater than 0 regardless of the magnitude of ω0. This indicates a condition under which, during a swing operation slower than a predetermined value ω0, the tip of the bucket 10 is permitted to come into contact with the soil (surrounding terrain) near the excavation start position (entry into the forbidden area), while the geometric center of the bucket 10 is not permitted to come into contact with the soil (surrounding terrain) near the excavation start position (entry into the forbidden area). Although an example has been shown in which Kg(x) and the weight μpg in equation (4d) are targeted at the geometric center position of the bucket 10, they can also be set as functions targeted at any part of the bucket 10 other than the geometric center or tip.

[0081] Next, the control procedure for the return motion in the control device for the work machine according to the first embodiment will be described with reference to Fig. 11. Fig. 11 is a flow chart showing an example of the control procedure for the return motion by the control device for the work machine according to the first embodiment shown in Fig. 3.

[0082] In Fig. 11, the control device 60 (see Fig. 3) starts control of the return operation (START), for example, when an operator operates a start switch for the return operation provided on the operating device 50 or the like, or when the soil releasing operation is completed in the case where control for automatic excavation and loading work is being executed. The control device 60 first acquires surrounding object detection information from the surrounding object detection device 26 and information on the excavation start position which is an instruction from the excavation start position setting device 27 (step S10).

[0083] Next, the control device 60 calculates the position of the detected surrounding object based on the detection information of the surrounding object obtained from the surrounding object detection device 26 (step S20), and sets the contact characteristic for the detected surrounding object (step S30). Note that the order of the processes of steps S20 and S30 does not matter.

[0084] Specifically, the surrounding object position calculation unit 72 of the control device 60 calculates the three-dimensional position of the detected surrounding object based on the position information (e.g., the distance from the surrounding object detection device 26, etc.) included in the detection information of the surrounding object detection device 26. In addition, the surrounding object characteristic setting unit 73 of the control device 60 determines the type and attribute of the surrounding object from, for example, shape information of the surrounding object obtained based on the detection information of the surrounding object detection device 26 or information previously stored in the internal storage device 62 or the external storage device 80, and sets contact characteristics for the surrounding object according to the type and attribute of the determination result. When the detection information of the surrounding object detection device 26 is image data, it is also possible to set the contact characteristics by the operator's operation for the image that is the detection information of the surrounding object detection device 26 displayed on the display device that also serves as the input device 28 (shown by the dashed line in FIG. 3).

[0085] Next, the control device 60 sets an evaluation function J based on the excavation start position acquired from the excavation start position setting device 27 in step S10, the three-dimensional position of the surrounding object which is the processing result of step S20, and the contact characteristics set in step S30 (step S40). Specifically, the evaluation function setting unit 74 of the control device 60 calculates the excavation start position y d An evaluation function J is set that is composed of a terminal cost φ and a stage cost L for approaching the bucket 10 to the target position, and a penalty cost P for moving a specific portion of the bucket 10 away from the entry-prohibited area under predetermined conditions. The predetermined conditions in the penalty cost P are specified as weights corresponding to the contact characteristics with respect to surrounding objects, and the entry-prohibited area is specified based on the positions of the surrounding objects obtained as a result of calculation.

[0086] Next, the control device 60 calculates a control input using the evaluation function set in step S40 (step S50). Specifically, the optimization calculation unit 75 of the control device 60 calculates the control inputs for the upper rotating body 5 and the front working implement 2 by performing optimization calculation to optimize the evaluation function set by the evaluation function setting unit 74 in a predicted time interval from the current time using the attitude information of the upper rotating body 5 and the front working implement 2, which is the calculation result of the attitude calculation unit 71.

[0087] Furthermore, the controller 60 converts the control inputs of the upper rotating body 5 and the front working implement 2, which are the calculation results of step S50, into control commands and outputs them to the electromagnetic proportional valves 41a, 41b to 46a, 46b (step S60). As a result, the electromagnetic proportional valves 41a, 41b to 46a, 46b are driven in response to the control commands, thereby controlling the pilot pressure input to the flow control valve 33. As a result, the stroke of the flow control valve 33 is controlled, and the hydraulic actuators 7, 11, 12, 13 are driven in response to the control inputs, which are the calculation results.

[0088] Next, the control device 60 determines whether the tip of the bucket 10 has reached the excavation start position (step S70). Specifically, it determines whether the tip position of the bucket 10 calculated by the attitude calculation unit 71 based on the attitude information acquired from the attitude detection device 20 has reached the excavation start position. If it is determined that the tip of the bucket 10 has not reached the excavation start position (No), the process returns to step S50, and steps S50 to S70 are repeated until YES is determined in step S70. In this way, the return operation is controlled until the tip of the bucket 10 reaches the excavation start position. If it is determined that the tip of the bucket 10 has reached the excavation start position (Yes), the control of the return operation is terminated (End).

[0089] Next, the path of the bucket in the control of the return operation of the work machine according to the first embodiment will be described with reference to Fig. 12 to Fig. 16. First, the path of the bucket in the absence of surrounding terrain (surrounding object) with which the bucket will come into contact during the return operation will be described. Fig. 12 is an explanatory diagram showing the bucket path in the absence of surrounding terrain (surrounding object) with which the bucket will come into contact during the return operation of the work machine according to the first embodiment.

[0090] Consider a case where there is no surrounding terrain such as soil and sand that may come into contact with the bucket during the return motion near the excavation start position, as shown in Fig. 12. In this case, since no forbidden area is set near the excavation start position, the penalty cost P in equation (4c) of the evaluation function J shown in equation (4) is zero. Therefore, the tip of the bucket 10 moves to the excavation start position based on the control input obtained from the result of the optimization calculation of the evaluation function J in which the penalty cost in equation (4c) is zero. For this reason, the combined motion of the swinging motion of the upper rotating body 5 and the lowering motion of the front working implement 2 causes the bucket 10 to move diagonally downward, for example, in the direction of the white arrow shown in Fig. 12.

[0091] Secondly, the path of the bucket during the return operation when there is surrounding terrain where contact characteristics are set to prohibit contact will be described with reference to Fig. 13 and Fig. 14. Fig. 13 is an explanatory diagram showing an example of the bucket path when there is surrounding terrain (surrounding object) that may come into contact with the bucket during the return operation. Fig. 14 is an explanatory diagram showing the bucket path when there is surrounding terrain (surrounding object) where contact characteristics are set to prohibit contact during the return operation of the work machine according to the first embodiment.

[0092] Consider a case where surrounding terrain (surrounding objects) that may come into contact with the bucket 10 is present near the excavation start position, as shown in Fig. 13. Furthermore, consider a case where the surrounding terrain is set to have contact characteristics that do not allow contact with the bucket 10 during swing. In this case, if the combined motion of the swinging motion of the upper swing body 5 and the lowering motion of the front working implement 2 causes the bucket 10 to move diagonally downward as shown in Fig. 12 and travel a path that brings it into contact with the surrounding terrain, the evaluation function J will increase due to the value of the penalty cost in equation (4c).

[0093] In this embodiment, the return movement is controlled based on the control input obtained from the result of the optimization calculation of the evaluation function J. Therefore, when the upper rotating body 5 is rotating, the bucket 10 moves to a position where the excavation start position can be reached only by the operation of the front working implement 2 via a path that does not come into contact with the surrounding terrain (surrounding objects) as shown in Fig. 14 so that the evaluation function J does not increase due to the value of the penalty cost in equation (4c). Then, the bucket 10 reaches the excavation start position only by the operation of the front working implement 2 without the rotating movement of the upper rotating body 5.

[0094] Thirdly, the path of the bucket during the return operation when a surrounding object for which contact characteristics are set to allow contact is present will be described with reference to Fig. 15. Fig. 15 is an explanatory diagram showing the bucket path when a surrounding terrain (surrounding object) for which contactable contact characteristics are set is present during the return operation of the work machine according to the first embodiment.

[0095] As shown in FIG. 15, a case is considered in which surrounding terrain (surrounding objects) that may come into contact with the bucket 10 is present near the excavation start position. Furthermore, a case is considered in which the surrounding terrain is set to have contact characteristics that allow contact with the bucket 10 during swing. In this case, when the bucket 10 moves diagonally downward and moves along a path that comes into contact with the surrounding terrain due to the combined action of the swinging motion of the upper rotating body 5 and the lowering motion of the front working implement 2, as in the case shown in FIG. 12, the penalty cost of the formula (4c) set corresponding to the contact characteristics indicating conditional contact permission becomes zero, so that the evaluation function J does not increase. Therefore, when the return operation is controlled based on the control input obtained from the result of the optimization calculation of the evaluation function J, for example, as shown in FIG. 15, the combined action of the swinging motion of the upper rotating body 5 and the lowering motion of the front working implement 2 results in the bucket 10 moving diagonally downward to the excavation start position.

[0096] In this manner, in this embodiment, the movement path of the bucket 10 during the return motion is changed according to the setting of the contact characteristic indicating the condition of whether or not the bucket 10 during the swing contacts the surrounding terrain (surrounding object) existing in the vicinity of the excavation start position. For example, when the surrounding terrain (surrounding object) is assumed to be hard, the movement path of the bucket 10 during the swing is a path that does not contact the surrounding terrain by setting the contact characteristic of contact prohibition, which does not allow contact with the bucket 10 during the swing, to the surrounding terrain. Therefore, the excavation start position can be reached while reducing the possibility of damage to the front working implement 2. Also, when the surrounding terrain is assumed to be soft, the movement path of the bucket 10 during the swing is a path that allows contact with the surrounding terrain by setting the contact characteristic of contact permission, which indicates that contact with the bucket 10 during the swing is allowed, to the surrounding terrain. In this case, by allowing contact with the surrounding terrain, the bucket 10 can reach the excavation start position via a path that is shorter than the path that avoids contact with the surrounding terrain.

[0097] Furthermore, in this embodiment, a contact prohibition contact characteristic is set for the loaded machine 100, which does not allow any contact with the bucket 10 at all, and the return operation is controlled based on a control input obtained from an optimization calculation of the evaluation function J set according to the contact prohibition contact characteristic. This makes it possible to perform a return operation that avoids contact between the loaded machine 100 and the bucket 10, as shown in Fig. 16, for example. Fig. 16 is an explanatory diagram showing a bucket path from the end of the soil discharge operation to the loaded machine in the return operation of the work machine according to the first embodiment.

[0098] After the bucket 10 releases soil by dumping, the position of the bucket 10 closest to the loaded machine 100 is the tip. Therefore, when setting the penalty function F in the penalty cost P of the evaluation function J, an intrusion prohibition area is set so as to include the loaded machine 100, which is a surrounding object. In addition, the weight μp in the penalty cost P of the formula (4c) is made to correspond to the contact characteristic of contact prohibition, and the swing speed ω Swgis set constant regardless of. When the penalty cost P of the evaluation function J is set in this manner, if the bucket 10 takes a path that brings the loaded machine 100 into contact with the loaded machine 100 (a path that enters the forbidden area), the evaluation function J increases by the value of the penalty cost in formula (4c). Therefore, when the return operation is controlled based on the control input obtained from the result of the optimization calculation of the evaluation function J, it is possible to perform a return operation that avoids contact between the loaded machine 100 and the bucket 10, for example, as shown in FIG.

[0099] As described above, the hydraulic excavator 1 (working machine) according to the first embodiment includes a rotatable upper rotating body 5 (rotating body), a multi-joint front working implement 2 (working implement) that is attached to the upper rotating body 5 (rotating body) so as to be rotatable in the vertical direction and has a bucket 10 (working implement), a surrounding object detection device 26 that detects objects including the terrain that exist around the upper rotating body 5 (rotating body), and a control device 60 that controls the upper rotating body 5 (rotating body) and the front working implement 2 (working implement). The control device 60 is configured to control a return operation that moves the bucket 10 (working implement) toward an excavation start position where the front working implement 2 (working implement) starts excavating an excavation target. The control device 60 sets whether or not the bucket 10 (working implement) can come into contact with surrounding objects detected by the surrounding object detection device 26, and is configured to operate the upper rotating body 5 (rotating body) and the front working implement 2 (working implement) to perform a return movement while allowing contact by the bucket 10 (working implement) for surrounding objects that are set as contactable.

[0100] According to this configuration, a return motion that allows contact between the bucket 10 (working tool) and a surrounding object that is set to be contactable can shorten the path to the excavation position compared to a return motion that avoids contact with the surrounding object. In this case, by setting whether or not the bucket 10 (working tool) can contact the surrounding object depending on the possibility of damage to the bucket 10 (working tool), the possibility of damage to the bucket 10 (working tool) can be reduced. In other words, a return motion that achieves both a reduction in the time to reach the excavation position and a reduction in the possibility of damage to the bucket 10 (working tool) due to contact with the surrounding object can be performed.

[0101] Furthermore, the control device 60 of the hydraulic excavator 1 (working machine) according to this embodiment is configured to set contact characteristics indicating the conditions for whether or not the bucket 10 (working implement) will come into contact with surrounding objects, calculate control inputs for the upper rotating body 5 (rotating body) and the front working implement 2 (working implement) such that the presence or absence of contact of the bucket 10 (working implement) with surrounding objects satisfies the contact characteristics while the bucket 10 (working implement) approaches the excavation start position, and operate the upper rotating body 5 (rotating body) and the front working implement 2 (working implement) based on the calculated control inputs.

[0102] According to this configuration, the bucket 10 (working tool) can be moved so as to approach the excavation start position while satisfying the contact characteristics set for the surrounding objects, so that when the contact characteristics for the surrounding objects are set to permit contact with the bucket 10 (working tool) in consideration of the low possibility of damage to the bucket 10 (working tool), the arrival time can be shortened by taking a path in which the bucket 10 (working tool) moves to the excavation start position without avoiding the surrounding objects, compared to a path that avoids the surrounding objects. In other words, a return operation can be performed that achieves both a shortened arrival time to the excavation position and a reduced possibility of damage to the bucket 10 (working tool) due to contact with the surrounding objects.

[0103] Furthermore, the control device 60 of the hydraulic excavator 1 (work machine) according to this embodiment is configured to determine the type or attributes of a surrounding object, and set contact characteristics according to the type or attributes of the surrounding object as a result of the determination.

[0104] According to this configuration, the control device 60 automatically determines the type and attributes of the surrounding objects detected by the surrounding object detection device 26 without any operation by the operator and sets the contact characteristics, thereby reducing the amount of operation required by the operator during the return motion.

[0105] Moreover, the control device 60 of the hydraulic excavator 1 (work machine) according to this embodiment is configured to set the contact characteristics in response to instructions from the input device 28 operated by the operator.

[0106] According to this configuration, contact characteristics corresponding to the operator's judgment are set for the surrounding objects detected by the surrounding object detection device 26, so that the return movement intended by the operator can be realized.

[0107] Furthermore, in the hydraulic excavator 1 (working machine) according to this embodiment, the contact characteristics are set so that the conditions for whether or not the bucket 10 (working implement) will come into contact with surrounding objects are different between a case in which the bucket 10 (working implement) moves in conjunction with the rotational movement of the upper rotating body 5 (rotating body) and a case in which the upper rotating body 5 (rotating body) does not rotate and the bucket 10 (working implement) moves in conjunction with the movement of the front working implement 2 (working implement).

[0108] According to this configuration, by changing the contact characteristics with respect to surrounding objects in accordance with the movement mode of the bucket 10 (work tool), it is possible to reduce the possibility of damage to the bucket 10 (work tool) due to contact with surrounding objects.

[0109] In addition, in the hydraulic excavator 1 (work machine) according to this embodiment, the contact characteristics indicate the conditions under which the tip of the bucket 10 (a part of the work implement) can or cannot come into contact with a surrounding object.

[0110] According to this configuration, the control input is calculated using only information about the tip (a part of the implement) of the entire bucket 10, so that the calculation load can be reduced.

[0111] In addition, in the hydraulic excavator 1 (work machine) according to this embodiment, the contact characteristics indicate the conditions for whether or not the entire bucket 10 (work implement) (vertices A, B, C) can come into contact with a surrounding object.

[0112] According to this configuration, a control input is calculated that takes into account the entire bucket 10 (work tool) regarding whether or not the bucket 10 (work tool) will come into contact with surrounding objects, so that contact of the bucket 10 (work tool) with surrounding objects can be reliably avoided.

[0113] Furthermore, in the hydraulic excavator 1 (work machine) according to this embodiment, the contact characteristics are set so that the conditions for whether or not the tip (first part) of the bucket 10 (work tool) can come into contact with a surrounding object are different from the conditions for whether or not the tip (first part) of the bucket 10 (work tool) can come into contact with a surrounding object and a geometric center (second part) different from the tip (first part).

[0114] According to this configuration, by setting appropriate contact characteristics for surrounding objects, it is possible to prioritize shortening the time it takes to reach the excavation position or to prioritize reducing the possibility of damage to the bucket 10 (work tool) due to contact with surrounding objects.

[0115] Furthermore, in the case of a surrounding terrain in which surrounding objects exist around a rotating body, the control device 60 of the hydraulic excavator 1 (work machine) in this embodiment is configured to compare the shape of the surrounding terrain before work begins, obtained based on the detection information from the surrounding object detection device 26, with the shape during excavation work, and to set contact characteristics that permit contact with the bucket 10 (working tool) for the area in which the shape of the surrounding terrain during excavation work has changed from the shape of the surrounding terrain before work begins.

[0116] With this configuration, the area where the shape of the surrounding terrain changes during excavation work compared to the shape before work began is assumed to be soil caused by excavation work, so the possibility of the bucket 10 (work tool) being damaged by contact with the soil in that area is low. This allows priority to be given to shortening the time it takes to reach the excavation position.

[0117] Moreover, the control device 60 of the hydraulic excavator 1 (work machine) according to this embodiment is configured to perform the calculation of the above-mentioned control input using an evaluation function J of model predictive control. The control device 60 is configured to calculate the position of a surrounding object based on the detection information from the surrounding object detection device 26, and to set the evaluation function J so as to include a penalty cost P expressed as the product of a penalty function F whose value increases under conditions in which the bucket 10 (work tool) enters a forbidden area set based on the position of the surrounding object as a result of the calculation, and a weight μp set in accordance with the contact characteristics.

[0118] According to this configuration, the penalty cost P is a function that reflects the contact characteristics set for the surrounding objects, so that the control of the return operation in this embodiment can be realized by implementing the algorithm of the evaluation function J in the control device 60.

[0119] [Second embodiment] Next, a work machine according to a second embodiment will be described with reference to Figs. 17 and 18. Fig. 17 is a block diagram showing the functions of a control device in a work machine according to a second embodiment of the present invention. Fig. 18 is an explanatory diagram showing a case where the excavation target contains minerals and there is a surrounding topography (surrounding object) that may come into contact with the bucket during the return motion. In Figs. 17 and 18, the same reference numerals as those in Figs. 1 to 16 denote similar parts, and detailed description thereof will be omitted.

[0120] The work machine according to the second embodiment differs from the first embodiment in the following ways. First, the hydraulic excavator 1 is equipped with a position information detection device 29 that detects information relating to the three-dimensional position of the work machine itself in a global coordinate system. Second, the control device 60A sets contact characteristics for the surrounding topography detected by the surrounding object detection device 26, using the detection information from the position information detection device 29 and geological information of the work site.

[0121] 17, a surrounding object characteristic setting unit 73A sets contact characteristics for the surrounding terrain detected by the surrounding object detection device 26 in a different manner. The control device 60A has functional units similar to those of the attitude calculation unit 71, the surrounding object position calculation unit 72, the evaluation function setting unit 74, the optimization calculation unit 75, and the actuator control unit 76, which are functional units other than the surrounding object characteristic setting unit 73 in the control device 60 according to the first embodiment.

[0122] The control device 60A is electrically or communicatively connected to the position information detection device 29, and is communicatively connected to a geological information database 81 (hereinafter, sometimes referred to as a geological information DB). The position information detection device 29 detects the position of the hydraulic excavator 1 itself in a global coordinate system by using, for example, a Global Navigation Satellite System (GNSS). The position information detection device 29 is composed of, for example, a GNSS antenna that receives satellite signals from positioning satellites, and a GNSS receiver that calculates the position of the GNSS antenna in the global coordinate system based on the satellite signals received by the GNSS antenna. The geological information DB81 stores geological information such as hardness, viscosity, and mass per unit volume for the topography of the work site including the excavation target to which the global coordinate position is assigned. The geological information DB81 transmits geological information of the work site including the excavation target associated with the global coordinate position to the control device 60A via a communication device.

[0123] The control device 60A is configured to acquire the geological information transmitted from the geological information DB 81. The control device 60A can also be configured to store the geological information in the internal storage device 62 in advance.

[0124] The surrounding object characteristic setting unit 73A of the control device 60A specifies the position in the global coordinate system of the surrounding terrain detected by the surrounding object detection device 26 by using the position of the hydraulic excavator 1 detected by the position information detection device 29 and the attitude information of the upper rotating body 5 which is the calculation result of the attitude calculation unit 71, and determines the type and attributes of the surrounding terrain by referring to the geological information to which the global coordinate position information obtained from the geological information DB 81 is added. The surrounding object characteristic setting unit 73A further sets the contact characteristics of the surrounding terrain in accordance with the determination result of the type and attributes of the surrounding terrain.

[0125] For example, if the geological information at a position in the global coordinate system corresponding to the surrounding terrain detected by the surrounding object detection device 26 is soil and sand that is harder than a predetermined value, the surrounding object characteristic setting unit 73A sets a contact prohibition contact characteristic that does not allow the bucket 10 to come into contact with the surrounding terrain while rotating.

[0126] In addition, when the geological information of the position of the global coordinate system corresponding to the surrounding terrain detected by the surrounding object detection device 26 is soil softer than a predetermined value, the contact characteristic of contact permission that allows the bucket 10 to contact the surrounding terrain during the swing is set. However, as shown in FIG. 18, when it is known from the geological information acquired from the geological information DB 81 that the mineral to be excavated exists at the excavation start position and soil of the surrounding terrain near the excavation start position is detected, the surrounding object characteristic setting unit 73A can be configured to set the contact characteristic of contact prohibition that does not allow the bucket 10 to contact the surrounding terrain during the swing even if the soil of the detected surrounding terrain is softer than a predetermined value. If the bucket 10 during the swing comes into contact with the surrounding terrain at the excavation start position, there is a concern that the soil of the surrounding terrain will fall and become mixed with the mineral to be excavated. Therefore, even if the soil of the surrounding terrain is softer than a predetermined value, in order to avoid mixing of the soil of the surrounding terrain with the mineral to be excavated, the contact characteristic of contact prohibition that does not allow the bucket 10 to contact the surrounding terrain during the swing is set as described above.

[0127] According to the second embodiment described above, as in the case of the first embodiment described above, the bucket 10 (working tool) can be moved so as to approach the excavation start position while satisfying the contact characteristics set for the surrounding objects, so that a return operation can be performed that achieves both a shortened time to reach the excavation position and a reduced possibility of damage to the bucket 10 (working tool) due to contact with surrounding objects.

[0128] In addition, the control device 60A of the hydraulic excavator 1 (work machine) in this embodiment is configured to acquire or pre-store geological information of the work site, and in the case of a surrounding terrain in which the surrounding object is a terrain that exists around the upper rotating body 5 (rotating body), to set contact characteristics according to the geological information acquired or stored for the surrounding terrain.

[0129] According to this configuration, the contact characteristics of the surrounding terrain can be set in accordance with attributes based on geological information, so that the possibility of damage to the bucket 10 (work tool) due to contact with the surrounding terrain can be reliably reduced.

[0130] [Third embodiment] Next, a work machine according to a third embodiment will be described with reference to Fig. 19. Fig. 19 is a block diagram showing the functions of a control device in a work machine according to a third embodiment. In Fig. 19, the same reference numerals as those in Figs. 1 to 18 denote similar parts, and detailed descriptions thereof will be omitted.

[0131] The difference between the work machine of the third embodiment and the second embodiment is that the control device 60B sets contact characteristics with respect to the surrounding terrain based on design information of the work site stored in a design database 82 (hereinafter sometimes referred to as the design DB) instead of the geological information stored in a geological information DB81.

[0132] Specifically, the design DB 82 stores design information in which each topography of the work site associated with the position of the global coordinates is classified into a travel route of the loaded machine 100, a bench for excavation work, etc. The design DB 82 transmits the design information of the work site associated with the position of the global coordinates to the control device 60B via the communication device.

[0133] The control device 60B is communicably connected to the design DB 82 and configured to acquire design information transmitted from the design DB 82. The control device 60B can also be configured to store the design information in advance in the internal storage device 62.

[0134] The surrounding object characteristic setting unit 73B of the control device 60B identifies the position in the global coordinate system of the surrounding terrain detected by the surrounding object detection device 26 based on the position of the hydraulic excavator 1 detected by the position information detection device 29 and the attitude information of the upper rotating body 5 as a result of the calculation by the attitude calculation unit 71. Furthermore, the surrounding object characteristic setting unit 73B determines the type and attributes of the surrounding terrain whose global coordinate system position has been determined by referring to design information (information associated with the position in the global coordinate system) obtained from the design DB 82. The surrounding object characteristic setting unit 73B further sets contact characteristics for the surrounding terrain in accordance with the type and attributes of the determination result.

[0135] For example, when the design information corresponding to the position of the global coordinate system of the surrounding terrain detected by the surrounding object detection device 26 is the terrain of the travel path of the loaded machine 100, the surrounding object characteristic setting unit 73B sets a contact prohibition contact characteristic that does not allow contact with the turning bucket 10 with respect to the surrounding terrain. This makes it possible to avoid contact of the bucket 10 with the travel path. Therefore, the terrain of the travel path of the loaded machine 100 is maintained without being disturbed, and the comfort of the travel of the loaded machine 100 is not impaired.

[0136] According to the third embodiment described above, as in the second embodiment described above, the bucket 10 (working tool) can be moved so as to approach the excavation start position while satisfying the contact characteristics set for the surrounding objects, so that a return operation can be performed that achieves both a shortened time to reach the excavation position and a reduced possibility of damage to the bucket 10 (working tool) due to contact with surrounding objects.

[0137] Furthermore, the control device 60B of the hydraulic excavator 1 (work machine) in this embodiment is configured to acquire or pre-store design information of the work site including information on the travel route of the loaded machine 100, and set contact characteristics that do not allow contact between the bucket 10 (work tool) and the surrounding objects when the surrounding objects have a topography that corresponds to the travel route included in the acquired or stored design information.

[0138] According to this configuration, contact of the bucket 10 (working tool) with the travel path of the loaded machine 100 is avoided, and the travel path is not disturbed, so that the comfort of the travel of the loaded machine 100 can be maintained.

[0139] [Other embodiments] The present invention is not limited to the present embodiment, and various modified examples are included. The above-mentioned embodiment has been described in detail to easily explain the present invention, and is not necessarily limited to those having all of the configurations described. It is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add, delete, or replace a part of the configuration of each embodiment with another configuration.

[0140] For example, in the above-mentioned first to third embodiments, the hydraulic excavator 1 equipped with the bucket 10 as the working implement of the front working mechanism 2 has been exemplified. However, the present invention can also be applied to hydraulic excavators equipped with a working implement other than the bucket 10. Furthermore, the present invention can also be applied to various types of work machines other than the hydraulic excavator 1, so long as a multi-joint type working implement is attached to a rotatable rotating body.

[0141] In the above-described embodiment, an example of a configuration in which the excavation start position setting device 27 is connected to the control device 60 has been shown. However, a configuration in which the control device 60 sets the excavation start position without external input is also possible. For example, a configuration in which the excavation start position is automatically determined based on information on the surrounding topography detected by the surrounding object detection device 26 is possible.

[0142] In the above-described embodiment, an example of a configuration in which the operation device 50 is an electric operation lever device has been shown, but the operation device may also be configured as a hydraulic operation lever device. [Explanation of symbols]

[0143] REFERENCE SIGNS LIST 1... hydraulic excavator (working machine), 2... front working device (working device), 5... upper rotating body (rotating body), 10... bucket (working tool), 26... surrounding object detection device, 28... input device, 60... control device, 100... loaded machine

Claims

1. A rotatable revolving body, a multi-joint working device that is attached to the revolving body so as to be rotatable in the vertical direction and has a working tool, a surrounding object detection device that detects an object including the terrain existing around the revolving body, and a control device that controls the revolving body and the working device, wherein in a working machine configured such that the control device controls a return operation of moving the working tool toward a digging start position which is a position where the working device starts digging a digging target, the control device determines whether the working tool can contact a surrounding object which is an object detected by the surrounding object detection device, and operates the revolving body and the working device so that the return operation is performed along a movement path where the working tool contacts the surrounding object among the surrounding objects for which contact is determined to be possible. A working machine characterized by the above.

2. In the working machine according to Claim 1, the control device sets a contact characteristic indicating a condition of whether the working tool can contact the surrounding object, calculates a control input for the revolving body and the working device such that the presence or absence of contact between the working tool and the surrounding object satisfies the contact characteristic and the working tool approaches the digging start position, and operates the revolving body and the working device based on the calculated control input. A working machine characterized by the above.

3. In the working machine according to Claim 2, the control device discriminates the type or attribute of the surrounding object, and sets the contact characteristic according to the type or attribute of the surrounding object as the discrimination result. A working machine characterized by the above.

4. In the working machine according to Claim 2, the control device sets the contact characteristic according to an instruction from an input device operated by an operator. A working machine characterized by the above.

5. In the working machine according to Claim 2, the contact characteristic is set such that conditions for whether the working tool can contact the surrounding object are different when the working tool moves with the revolving operation of the revolving body and when the working tool moves with the operation of the working device without the revolving operation of the revolving body. A working machine characterized by the above.

6. In the working machine according to Claim 2, the contact characteristic indicates a condition for whether the entire working tool can contact the surrounding object. A working machine characterized by the above.

7. In the working machine according to Claim 2, The contact characteristics are set such that the condition for the first part of the working tool to come into contact with the surrounding object is different from the condition for a second part, different from the first part of the working tool, to come into contact with the surrounding object. A working machine characterized by this.

8. In the working machine according to claim 2, when the surrounding object is the surrounding terrain which is the terrain existing around the revolving body, the control device compares the shape of the surrounding terrain before the start of the work obtained based on the detection information of the surrounding object detection device with the shape during the excavation work, and sets contact characteristics that allow contact with the working tool for the area of the change in the shape during the excavation work with respect to the shape of the surrounding terrain before the start of the work. A working machine characterized by this.

9. In the working machine according to claim 2, the control device acquires or stores in advance the geological information of the work site, and when the surrounding object is the surrounding terrain which is the terrain existing around the revolving body, sets the contact characteristics according to the geological information with respect to the surrounding terrain. A working machine characterized by this.

10. In the working machine according to claim 2, the control device acquires or stores in advance the design information of the work site including the information on the traveling route of the loading machine, and when the surrounding object is the terrain corresponding to the traveling route included in the design information, sets contact characteristics that do not allow the working tool to come into contact with the surrounding object. A working machine characterized by this.

11. In the working machine according to claim 2, the control device is configured to perform the calculation of the control input using the evaluation function of model predictive control, the control device calculates the position of the surrounding object based on the detection information of the surrounding object detection device, and sets the evaluation function to include a penalty cost represented by the product of a penalty function whose value increases in the case where the working tool enters the intrusion prohibition area set based on the position of the surrounding object in the calculation result and the weight set according to the contact characteristics. A working machine characterized by this.

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