CONTROL DEVICE, CONTROL METHOD, AND WORK MACHINE

Description

TECHNICAL FIELD

The present disclosure relates to a control device, a control method, and a work machine.

Priority is claimed on Japanese Patent Application No. 2022-174261, filed Oct. 31, 2022, the content of which is incorporated herein by reference.

BACKGROUND ART

Patent Document 1 describes a device for determining a strategy that may efficiently perform excavation processing. The device described in Patent Document 1 divides an excavation site into small excavation areas in a grid pattern, determines boundary lines and an excavation sequence for each of the areas, searches for each excavation site in the order of the provided excavation sequence, and optimizes a cost function on the basis of performance criteria such as an amount of excavation, and consumed energy and time. Thereby, an optimum position and orientation of an excavator's bucket for starting excavation is determined. Here, a width of each excavation area is set to approximately one bucket width. Also, the order in which the excavation areas are excavated may be set on the basis of, for example, a top-to-bottom order and an order of directions that do not obstruct a view of an operator. Also, in each excavation area, a bucket angle and an excavation start position within the area are optimized.

CITATION LIST

Patent Document

• • Patent Document 1: Japanese Unexamined Patent Application, First Publication No. H11-247230

SUMMARY OF INVENTION

Technical Problem

In the device described in Patent Document 1, the order in which the excavation areas are excavated is determined in advance. Therefore, for example, if the order of operations becomes less appropriate as the operations progress, there is a problem that maintaining an efficiency of excavation operations becomes difficult.

The present disclosure has been made to solve the above-described problem, and an objective thereof is to provide a control device, a control method, and a work machine that are capable of easily maintaining an efficiency in automatic excavation operations.

Solution to Problem

One aspect of the present disclosure is a control device of a work machine including a swing body swinging around a swing center and work equipment attached to the swing body, and includes an excavation-start-position determination unit determining a start position of an excavation operation for each single excavation operation on the basis of at least an excavation time required for the excavation operation and a swing time required for a loading swing and a return swing when the excavation operation, a dumping operation, and the loading swing and the return swing between the excavation operation and the dumping operation are automatically performed by the work equipment.

One aspect of the present disclosure is a control method for a work machine including a swing body swinging around a swing center and work equipment attached to the swing body, and includes a step of determining a start position of an excavation operation for each single excavation operation on the basis of at least an excavation time required for the excavation operation and a swing time required for a loading swing and a return swing when the excavation operation, a dumping operation, and the loading swing and the return swing between the excavation operation and the dumping operation are automatically performed by the work equipment.

One aspect of the present disclosure is a work machine including a swing body swinging around a swing center, work equipment attached to the swing body, and a control device, in which the control device includes an excavation-start-position determination unit determining a start position of an excavation operation for each single excavation operation on the basis of at least an excavation time required for the excavation operation and a swing time required for a loading swing and a return swing when the excavation operation, a dumping operation, and the loading swing and the return swing between the excavation operation and the dumping operation are automatically performed by the work equipment.

One aspect of the present disclosure is a control method remotely controlling a work machine including a swing body swinging around a swing center and work equipment attached to the swing body, and includes a step of determining a start position of an excavation operation for each single excavation operation on the basis of at least an excavation time required for the excavation operation and a swing time required for a loading swing and a return swing when the excavation operation, a dumping operation, and the loading swing and the return swing between the excavation operation and the dumping operation are automatically performed by the work equipment. Advantageous Effects of Invention

The control device, the control method, and the work machine of the present disclosure are capable of easily maintaining an efficiency in an automatic excavation operation.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 A schematic view illustrating a configuration of a work machine according to an embodiment of the present disclosure.

FIG. 2 A block diagram showing a configuration example of a control system according to the embodiment of the present disclosure.

FIG. 3 A plan view schematically illustrating an operation example of a control device according to the embodiment of the present disclosure.

FIG. 4 A flowchart illustrating an operation example of the control device according to the embodiment of the present disclosure.

FIG. 5 A schematic view illustrating an example of a three-dimensional shape of a terrain for explaining an operation example of the control device according to the embodiment of the present disclosure.

FIG. 6 A schematic view illustrating an example of a positional relationship between the work machine and a dump truck according to the embodiment of the present

DISCLOSURE

FIG. 7 A schematic diagram showing an example of a relationship between an excavation direction and a two-dimensional cross section of a terrain according to the embodiment of the present disclosure.

FIG. 8 A side-view diagram schematically showing an example of an excavation trajectory according to the embodiment of the present disclosure.

FIG. 9 A schematic diagram showing an example of a model of work equipment according to the embodiment of the present disclosure.

FIG. 10 A schematic diagram showing examples of parameters according to the embodiment of the present disclosure.

FIG. 11 A side view schematically illustrating an example of a positional relationship between the work equipment and an excavation target according to the embodiment of the present disclosure.

FIG. 12 A side view schematically illustrating an example of movement of the work equipment according to the embodiment of the present disclosure.

FIG. 13 A schematic diagram showing examples of an evaluation index, an excavation volume, an excavation time, and a swing time according to the embodiment of the present disclosure.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that, the same or corresponding components in each drawing are denoted using the same reference signs and description thereof will be omitted as appropriate. FIG. 1 is a schematic view illustrating a configuration of a work machine according to an embodiment of the present disclosure. FIG. 2 is a block diagram showing a configuration example of a control system according to the embodiment of the present disclosure. FIG. 3 is a plan view schematically illustrating an operation example of a control device according to the embodiment of the present disclosure. FIG. 4 is a flowchart illustrating an operation example of the control device according to the embodiment of the present disclosure. FIG. 5 is a schematic view illustrating an example of a three-dimensional shape of a terrain for explaining an operation example of the control device according to the embodiment of the present disclosure. FIG. 6 is a schematic view illustrating an example of a positional relationship between the work machine and a dump truck according to the embodiment of the present disclosure. FIG. 7 is a schematic diagram showing an example of a relationship between an excavation direction and a two-dimensional cross section of a terrain according to the embodiment of the present disclosure. FIG. 8 is a side-view diagram schematically showing an example of an excavation trajectory according to the embodiment of the present disclosure. FIG. 9 is a schematic diagram showing an example of a model of work equipment according to the embodiment of the present disclosure. FIG. 10 is a schematic diagram illustrating examples of parameters according to the embodiment of the present disclosure. FIG. 11 is a side view schematically illustrating an example of a positional relationship between the work equipment and an excavation target according to the embodiment of the present disclosure. FIG. 12 is a side view schematically illustrating an example of movement of the work equipment according to the embodiment of the present disclosure. FIG. 13 is a schematic diagram showing examples of an evaluation index, an excavation volume, an excavation time, and a swing time according to the embodiment of the present disclosure.

(Configuration of Work Machine 100)

FIG. 1 illustrates a configuration example of a work machine 100 according to an embodiment of the present disclosure. The work machine 100 operates at a construction site and performs a construction on a construction object such as earth. The work machine 100 according to the embodiment of the present disclosure is, for example, a hydraulic excavator. However, the work machine of the present disclosure is not limited as long as it is a work machine that is equipped with, for example, a swing body and work equipment, and may be other work machines such as, for example, a face excavator or an electric excavator. The work machine 100 includes an undercarriage 110, a swing body 120, work equipment 130, and a cab 140.

The undercarriage 110 supports the work machine 110 in a state in which the work machine 100 is capable of traveling. The undercarriage 110 includes two crawler tracks 111 provided on the left and right and two travel motors 112 for driving the crawler tracks 111. The swing body 120 is supported by the undercarriage 110 in a state in which the swing body 120 is capable of swinging around a swing center.

The work equipment 130 is driven by a hydraulic pressure. The work equipment 130 is supported by a front part of the swing body 120 in a state in which it is capable of being driven in a vertical direction. The cab 140 is a space for an operator to be on board and perform an operation of the work machine 100. The cab 140 is provided in a left front part of the swing body 120. Note that, in the present embodiment, as illustrated in FIG. 1, a vertical direction, a left-right direction, and a front-rear direction are defined with the swing body 120 as a reference. In the present embodiment, this coordinate system is called an excavator coordinate system. A part of the swing body 120 to which the work equipment 130 is attached is referred to as a front part. With respect to the swing body 120, with the front part as a reference, a part opposite to the front part is referred to as a rear part, a part on a left side is referred to as a left part, and a part on a right side is referred to as a right part.

(Configuration of Swing Body 120)

The swing body 120 includes an engine 121, a hydraulic pump 122, an electromagnetic proportional control (EPC) valve 123-1, a main valve 123-2, a swing motor 124, and a fuel injection device 125. The engine 121 is a prime mover that drives the hydraulic pump 122. The engine 121 is an example of a power source. A starter motor 1211 is provided in the engine 121. The engine 121 is started by rotation of the starter motor 1211. The EPC valve 123-1 controls a hydraulic oil flowing to the main valve 123-2 on the basis of an operation command signal output by a control device 61.

The hydraulic pump 122 is a variable capacity pump driven by the engine 121. The hydraulic pump 122 supplies a hydraulic oil to each of actuators via the main valve 123-2. The actuators include a boom cylinder 131C, an arm cylinder 132C, a bucket cylinder 133C, the travel motor 112, and the swing motor 124. The main valve 123-2 controls a flow rate of the hydraulic oil supplied from the hydraulic pump 122.

The swing motor 124 is driven by the hydraulic oil supplied from the hydraulic pump 122 via the main valve 123-2. Thereby, the swing motor 124 swings the swing body 120 around a swing axis 120C (swing center). The fuel injection device 125 injects fuel into the engine 121.

(Configuration of Work Equipment 130)

The work equipment 130 includes a boom 131, an arm 132, a bucket 133, the boom cylinder 131C, the arm cylinder 132C, and the bucket cylinder 133C. Note that, the boom cylinder 131C, the arm cylinder 132C, and the bucket cylinder 133C are included in a cylinder 130C shown in FIG. 2.

A base end part of the boom 131 is attached to the swing body 120 via a boom pin. The arm 132 connects the boom 131 and the bucket 133. A base end part of the arm 132 is attached to a distal end part of the boom 131 via an arm pin. The bucket 133 includes bucket teeth (also referred to as a distal end) 133T for excavating earth or the like, and an accommodation portion for accommodating the excavated earth. A base end part of the bucket 133 is attached to a distal end part of the arm 132 via a bucket pin 133P.

The boom cylinder 131C is a hydraulic cylinder for operating the boom 131. A base end part of the boom cylinder 131C is attached to the swing body 120. A distal end part of the boom cylinder 131C is attached to the boom 131. The arm cylinder 132C is a hydraulic cylinder for driving the arm 132. A base end part of the arm cylinder 132C is attached to the boom 131. A distal end part of the arm cylinder 132C is attached to the arm 132. The bucket cylinder 133C is a hydraulic cylinder for driving the bucket 133. A base end part of the bucket cylinder 133C is attached to the arm 132. A distal end part of the bucket cylinder 133C is attached to a link member that is connected to the bucket 133.

(Configuration of Cab 140)

A driver's seat, an operation device 143 shown in FIG. 2, and the like are provided in the cab 140. The operation device 143 is a device for driving the undercarriage 110, the swing body 120, and the work equipment 130 through a manual operation by an operator, setting and changing set values of various types, and providing information to the operator. The operation device 143 includes a plurality of levers and a plurality of pedals (a left operation lever, a right operation lever, a left foot pedal, a right foot pedal, a left travel lever, a right travel lever, and the like), a display input device 143D, and the like. The display input device 143D is a device that combines a display device and a sensor that detects a touch operation on a display screen. For example, it is possible for the operator to set or change set values of various types by using the display input device 143D. Note that, the work machine 100 according to the present embodiment operates in accordance with an operation of the operator seated in the driver's seat, but it is not limited thereto in another embodiment. For example, the work machine 100 according to another embodiment may be operated by an operation command signal or the like generated and transmitted through a remote operation performed by the operator outside the work machine 100.

(Sensor and the Like)

As shown in FIG. 2, a control system 60 of the work machine 100 includes the control device 61, the operation device 143 and the like, and sensors of various types.

Note that, in FIG. 2, a hydraulic system circuit is indicated by a thick line. In the example shown in FIG. 2, the control system 60 includes a three-dimensional shape sensor 150, a posture angle sensor 151, a global navigation satellite system (GNSS) sensor 152, and an inertial measurement unit (IMU) 153.

Examples of the three-dimensional shape sensor 150 include a stereo camera, a light detection and ranging (LiDAR) device, a millimeter wave radar, and the like. Alternatively, examples of the three-dimensional shape sensor 150 include a combination of one or more of those sensors described above. These sensors are provided so that, for example, detection directions of the sensors face forward and rearward of the cab 140 of the work machine 100. These sensors determine a three-dimensional position of an object on the basis of a coordinate system referenced to a position of each sensor. The three-dimensional shape sensor 150 outputs, for example, depth information indicating three-dimensional positions of a plurality of points within a detection range. Examples of the depth information include depth images formed of a plurality of pixels representing a depth, and point cloud data formed of a plurality of points expressed in an orthogonal coordinate system (x, y, z).

The posture angle sensor 151 includes, for example, stroke sensors attached to respective cylinders. Then, on the basis of cylinder lengths measured by the stroke sensors, posture angles of the boom 131, the arm 132, and the bucket 133 are calculated. Note that, in addition to the stroke sensors, an IMU may be mounted on each of the swing body 120, the boom 131, the arm 132, and the bucket 133 to measure a posture angle of each axis.

The GNSS sensor 152 calculates a position of the swing body 120 and an azimuth direction in which the swing body 120 is directed. The GNSS sensor 152 includes two receivers 126-1 and 126-2 that receive positioning signals from artificial satellites that form a GNSS. The two receivers 126-1 and 126-2 are installed at different positions in the swing body 120. The GNSS sensor 152 detects a position of a representative point (origin of an excavator coordinate system) of the swing body 120 in the site coordinate system on the basis of the positioning signals received by the receivers 126-1 and 126-2. The GNSS sensor 152 uses the positioning signals received by the two receivers 126-1 and 126-2 to calculate an azimuth angle in which the swing body 120 is directed. This azimuth angle is calculated as a relationship of an installation position of one receiver with respect to an installation position of the other receiver. The azimuth angle in which the swing body 120 is directed (also referred to as a vehicle body azimuth angle) refers to a front direction of the swing body 120. The azimuth angle in which the swing body 120 is directed is equal to a horizontal component of an extension direction of a straight line extending from the boom 131 to the bucket 133 of the work equipment 130.

The IMU 153 measures an acceleration and an angular velocity of the swing body 120 and detects a posture (for example, a roll angle and a pitch angle) of the swing body 120 on the basis of the measurement result. The IMU 153 is installed, for example, on a lower surface of the swing body 120.

The work machine 100 includes, for example, a short-range communication device for performing vehicle-to-vehicle communication with other vehicles in the vicinity or the like, a mobile body communication device for establishing communication connections with remote servers or the like, and the like.

(Basic Operation of Control Device)

First, a basic operation of the control device 61 according to the embodiment of the present disclosure will be described with reference to FIG. 3. Note that, in the present embodiment, a swinging operation of automatically moving the bucket 133 loaded with excavated earth or the like from an excavation completion position or the like to a dumping position is referred to as “loading swing”. A swing operation of automatically moving the bucket 133 from the dumping position to an excavation start position is referred to as “return swing”. The dumping position is a target position in which loading or the like is performed. The dumping position is set, for example, at an inlet of a loading platform of a dump truck, a land improvement machine, a hopper, or the like. However, the dumping position is not limited thereto. For example, when excavated earth or the like is moved to another ground surface, such a destination of the movement may also be set as the dumping position. In the present disclosure, the dumping position corresponds to a target position for unloading a load performed by a loading tool (such as the bucket 133). The excavation start position is a target position for an automatic return operation of the bucket 133 after completion of dumping. The excavation start position is set, for example, to a point at which excavation starts. In the present disclosure, the excavation start position corresponds to a target position for loading a load by a loading tool (such as the bucket 133). In the present embodiment, a position of the bucket pin 133P is used as a reference for the dumping position, and a position of the distal end 133T of the bucket 133 is used as a reference for the excavation start position.

FIG. 3 schematically illustrates a series of flows including excavation, loading swing, dumping, and return swing. In the work machine 100 illustrated in FIG. 3, for example, when a start of automatic excavation is instructed by the operator through a predetermined input operation, the control device 61 determines an excavation start position taking into account a swing time (a total of a time for loading swing following an excavation operation and a time for return swing to a next excavation start position after dumping). A method of determining the excavation start position will be described later.

Next, the control device 61 starts automatic excavation from the determined excavation start position (S1). As illustrated in the upper right, when a single excavation operation ends, the work equipment 130 automatically swings (loading swing) to the dumping position (S2). The control device 61 determines the dumping position on the basis of, for example, an output of the three-dimensional shape sensor 150, position information of a dump truck to be dumped, and specification information indicating a shape of the dump truck, or the like.

Next, as illustrated in the lower right, the control device 61 automatically executes the dumping operation at the dumping position (S3), and determines a next excavation start position taking into consideration the swing time (a total of a time for return swing to the next excavation start position following the dumping operation and a time for loading swing to a next dumping position after a next excavation operation) (S4). Note that, the next excavation start position only needs to be determined before the dumping operation ends. For example, after the automatic excavation (S1), processing of determining the excavation start position may be started at a stage in which shape data after excavation has been acquired. For example, the processing of determining the next excavation start position may be started before the loading swing (S2) or the dumping operation (S3).

Next, as illustrated in the lower left, the control device 61 automatically swings the work equipment 130 (return swing) to the excavation start position (S5). Thereafter, for example, operations of steps S1, S2, S3, S4, S5, S1, S2, S3, S4, S5, . . . are repeatedly performed until the dump truck or the like is full.

(Configuration of control device)

The control device 61 shown in FIG. 2 may be configured using, for example, a computer such as a microcomputer. The control device 61 includes, as a functional configuration, an automatic excavation/swing/dumping control unit 62 (first control unit), a storage unit 63, and an operation-command switching unit 64 (switching unit). This functional configuration is formed by a combination of hardware such as a computer, computer peripheral devices, and peripheral circuits, and software such as a program executed by the computer. The automatic excavation/swing/dumping control unit 62 includes an information acquisition unit 621 (acquisition unit), an excavation-start-position determination unit 622 (determination unit), an operation-command-switching control unit 623 (second control unit), and an operation-command-signal generation unit 624 (generation unit). The storage unit 63 stores information 631 including design surface information, work machine specification information, loading target specification information, and the like. The design surface information is information that represents a design shape (or a target shape) when an excavation surface is formed so that the excavation surface becomes a predetermined design surface during the excavation operation. The work machine specification information includes information representing a shape of the work machine 100, information representing a speed and time of the swing operation, and the like. The loading target specification information is, for example, information representing a shape of a loading target such as a dump truck, or the like.

The automatic excavation/swing/dumping control unit 62 generates an (automatic) operation command signal and outputs it to the EPC valve 123-1 via the operation-command switching unit 64. Thereby, the automatic excavation/swing/dumping control unit 62 automatically drives the swing body 120 and the work equipment 130 to automatically perform the excavation operation, the loading swing, the dumping operation, and the return swing.

The information acquisition unit 621 acquires predetermined information output by the operation device 143, the three-dimensional shape sensor 150, the posture angle sensor 151, the GNSS sensor 152, the IMU 153, and the like.

(Excavation-Start-Position Determination Unit)

When the automatic excavation/swing/dumping control unit 62 automatically performs the excavation operation, the dumping operation, and the loading swing and the return swing between the excavation operation and the dumping operation by the work equipment 130, the excavation-start-position determination unit 622 determines a start position of the excavation operation for each single excavation operation on the basis of at least an excavation time tf required for the excavation operation and a swing time tm required for the loading swing and the return swing. Note that, the excavation-start-position determination unit 622 determines the start position of the excavation operation for each single excavation operation on the basis of, for example, an estimated value S of an excavation amount for a single excavation operation, the excavation time tf, and the swing time tm. At that time, the excavation-start-position determination unit 622 determines the start position of the excavation operation for each single excavation operation on the basis of, for example, an evaluation index J shown in expression (1). Note that, the estimated value S of the excavation amount (hereinafter also referred to as an excavation amount S, an excavation volume S, or the like) may be a weight or the like as well as the volume.

As another embodiment, the excavation-start-position determination unit 622 may be configured to determine a start position of the excavation operation for each single excavation operation on the basis of an estimated value of the excavation amount for a single excavation operation, the excavation time tf, a dumping time required for the dumping operation, and the swing time tm. In this case, for example, the dumping time in automatic dumping may be assumed to be substantially constant regardless of a loading point of the dump truck. Also, for example, an optimum excavation start position determination may be performed by employing an evaluation function in which the dumping time in automatic dumping is also included. The evaluation function in this case may be, for example, an expression in which the denominator of expression (1) is set as (excavation time+swing time+dumping time). Hereinafter, a case in which the dumping time is not included will be described as an example.

[ Math . 1 ] J = S t f + t m = Excavation ⁢ amount Excavation ⁢ time + Swing ⁢ time ( 1 )

In this case, the excavation-start-position determination unit 622 determines the start position of the excavation operation for each single excavation operation on the basis of, for example, a value (evaluation index J) obtained by dividing the estimated value S by a total value of the excavation time tf and the swing time tm.

Note that, the excavation-start-position determination unit 622 may obtain the estimated value S, the excavation time tf, and the swing time tm for a plurality of excavation directions, and determine the start position on the basis of comparison results between the plurality of excavation directions. In this case, the excavation-start-position determination unit 622 estimates the estimated value S and the excavation time tf on the basis of, for example, a two-dimensional cross section obtained for each excavation direction from the three-dimensional shape of the excavation target in the excavation operation.

FIG. 4 shows a flow of processing executed by the automatic excavation/swing/dumping control unit 62. The processing shown in FIG. 4 is, for example, the processing executed in step S4 shown in FIG. 3. The processing shown in FIG. 4 is executed for each single (one pass) excavation operation. The processing in steps S11 to S14 is for estimating the excavation amount S [m³] and the excavation time tf [s]. The processing in steps S15 to S18 is for estimating the swing time tm. In the example shown in FIG. 4, the processing of steps S11 to S14 and the processing of steps S15 to S18 are executed in parallel. However, the processing in steps S11 to S14 and the processing in steps S15 to S18 may be executed in sequence.

In the processing of steps S11 to S14, first, the information acquisition unit 621 acquires a current terrain from the three-dimensional shape sensor 150 (S11). Next, the information acquisition unit 621 acquires the design surface (information) from the storage unit 632 (S12). Note that, if the design surface is not set (for example, if a sole purpose is to acquire earth or the like), the processing of step S12 is omitted.

Next, the excavation-start-position determination unit 622 extracts the current terrain or design surface of the two-dimensional cross section when the excavation direction is varied at intervals of, for example, 10 degrees (S13). FIG. 5 schematically illustrates an example of the current terrain acquired by the information acquisition unit 621 from the three-dimensional shape sensor 150. x′, y′, and z are coordinate axes used as references when the three-dimensional shape sensor 150 acquires three-dimensional shape data. FIG. 6 schematically illustrates positions of the work machine 100 and the dump truck (loading target) 200 along with the three-dimensional shape of the terrain illustrated in FIG. 5. A plurality of arrows around the work machine 100 indicate excavation directions with the swing axis 120C as a reference. In this case, a loading platform 201 (dumping position (loading position)) of the dump truck 200 is positioned in a direction of 180 degrees.

In step S13, the excavation-start-position determination unit 622 extracts the current terrain or design surface of the two-dimensional cross section when the excavation direction is varied, for example, at intervals of 10 degrees. FIG. 7 schematically shows an example of extraction of the two-dimensional cross section. FIG. 7 shows an example in which, for example, the three-dimensional shape of the terrain illustrated in FIG. 5 has information on a height direction (z direction) for each predetermined mesh M. A point O is a reference point of mesh information. φ represents an excavation direction illustrated in FIG. 6 as 80°, 40°, 0°, −40°, −80°, or the like. A point O′ corresponds to the swing axis 120C of the work machine 100. x represents a forward direction of the swing body 120. In this case, in step S13, the excavation-start-position determination unit 622 calculates two-dimensional cross-sectional information (Z0=0, Z1, Z2, Z3, . . . ) by arranging the height information for each mesh M in the excavation direction φ to be associated with positions x1, x2, . . . in the x direction.

Next, the excavation-start-position determination unit 622 calculates an optimal trajectory for one-pass excavation for each cross section at intervals of 10 degrees, and estimates the excavation amount S [m³] and excavation time tf [s] of the optimal trajectory (S14). FIG. 8 shows an example of calculation of the excavation trajectory. The horizontal axis represents a position in the x direction, and the vertical axis represents a position (height) in the z direction. FIG. 8 shows an example of the trajectory of the tip 133T when the excavation direction φ is 0 degrees. The black circle on the trajectory indicated by the dashed line represents an excavation start position, and the white circle indicates an excavation completion position. In the present embodiment, the excavation-start-position determination unit 622 calculates an optimal excavation trajectory for each single excavation operation. The optimal trajectory is determined by, for example, an angular velocity of each joint and a cylinder speed in a time series.

(Calculation of Optimal Trajectory)

In the present embodiment, the optimal excavation trajectory is formulated as an optimal control problem and is solved. At that time, the work equipment 130 was modeled as shown in FIG. 9, and the equation of motion shown in expression (2) was used.

Further, in solving the optimal control problem, the pseudospectral method is employed, and therefore, expression (2) is expressed in a form of equation shown in expression (3). The pseudospectral method facilitates handling of control conditions and enables optimal control problems to be solved with relatively high speed and stability.

[ Math . 3 ] d ⁢ ξ d ⁢ t = d d ⁢ t [ q q . ] = [ q . f 0 ( ξ , u ) ] = f ⁡ ( ξ , u ) ) ( 3 )

Where,

[ Math . 4 ] ξ = [ q q . ] ( 4 )

• • holds true.

FIG. 10 represents some of the parameters used in expression (2). Expressions (5) to (19) represent variables used in expression (2). Note that, in expression (2), the term TM11 is an inertia matrix, the term TM12 is a torque due to a centrifugal force and Coriolis force, and the term TM13 is a gravitational torque. Also, in FIGS. 9, a11 and a12 represent a length and a height from a joint of the boom 131 to a center of gravity, a21 and a22 represent a length and a height from a joint of the arm 132 to a center of gravity, and a31 and a32 represent a length and a height from a joint of the bucket 133 to a center of gravity.

[ Math . 5 ] H = ( SQ 1 T + CQ 2 T ) ⁢ M ⁡ ( Q 1 ⁢ S + Q 2 ⁢ C ) + ( CQ 1 T - SQ 2 T ) ⁢ M ⁡ ( Q 1 ⁢ C - Q 2 ⁢ S ) + I ( 5 ) [ Math . 6 ] B = ( SQ 1 T + CQ 2 T ) ⁢ M ⁡ ( Q 1 ⁢ C - Q 2 ⁢ S ) - ( CQ 1 T - SQ 2 T ) ⁢ M ⁡ ( Q 1 ⁢ S + Q 2 ⁢ C ) ( 6 ) [ Math . 7 ] g = g ⁡ ( CQ 1 T - SQ 2 T ) ⁢ m ( 7 ) [ Math . 8 ] Q 1 = [ a 11 0 0 l 1 a 21 0 l 1 l 2 a 31 ] ( 8 ) [ Math . 9 ] Q 2 = [ a 12 0 0 0 a 22 0 0 0 a 32 ] ( 9 ) [ Math . 10 ] K = [ 1 0 0 1 1 0 1 1 1 ] ( 10 ) [ Math . 11 ] θ = Kq ( 11 ) [ Math . 12 ] d = R ⁢ q . ( 12 ) [ Math . 13 ] Θ = diag ⁡ ( θ ) ( 13 ) [ Math . 14 ] C = diag ⁡ ( cos ⁢ θ 1 , cos ⁢ θ 2 , cos ⁢ θ 3 ) ( 14 ) [ Math . 15 ] S = diag ⁡ ( sin ⁢ θ 1 , sin ⁢ θ 2 , sin ⁢ θ 3 ) ( 15 ) [ Math . 16 ] m = [ m 1 , m 2 , m 3 ] T ( 16 ) [ Math . 17 ] M = diag ⁡ ( m ) ( 17 ) [ Math . 18 ] I = diag ⁡ ( I 1 , I 2 , I 3 ) ( 18 ) [ Math . 19 ] R = diag ⁡ ( r 1 , r 2 , r 3 ) ( 19 )

Next, a solution process using the pseudospectral method based on expression (3) and expression (4) will be described. In the present embodiment, the model shown in expression (20) was introduced to obtain a numerically stable solution. In this model, a time from an initial time 10 to a terminal time tf is converted into a normalized time τ (where, τ belongs to [−1, 1]). Here, ξ and u are state variables and control inputs defined in expression (3) and expression (4).

[ Math . 20 ]  d ⁢ ξ d ⁢ τ = t f - t 0 2 ⁢ f ⁡ ( ξ ⁡ ( τ ) , u ⁡ ( τ ) , τ ; t 0 , t f ) ( 20 )

Next, a control variable u(τ) and a state variable ξ(τ) were discretized using the Lagrange polynomial Li(τ). Here, τi is an i-th discrete time.

[ Math . 21 ]  ξ ⁡ ( τ ) ≈ Ξ ⁡ ( τ ) = ∑ i = 0 N Ξ ⁡ ( τ i ) ⁢ L i ( τ ) ( 21 ) [ Math . 22 ]  L i ( τ ) = ∏ j = 0 , j ≠ i N τ - τ j τ i - τ j ( 22 ) [ Math . 23 ]  u ⁡ ( τ ) ≈ U ⁡ ( τ ) = ∑ i = 0 N U ⁡ ( τ i ) ⁢ L i * ( τ ) ( 23 ) [ Math . 24 ]  L i * ( τ ) = ∏ j = 1 , j ≠ i N τ - τ j τ i - τ j ( 24 )

An evaluation function (minimization) was defined as expression (25). In this case, an excavation efficiency is maximized.

[ Math . 25 ]  g = - bucket ⁢ sweep ⁢ area ⁢ per ⁢ unit ⁢ time ( 25 )

Expression (25), when expressed in mathematical form, becomes expression (26).

[ Math . 26 ]  g = - 1 t f - t 0 ⁢ ∫ x ⁡ ( t 0 ) x ( t f ) z ⁢ dx = - 1 t f - t 0 ⁢ ∫ t 0 t f z ⁢ x . ⁢ dt ( 26 )

From this expression (26), the excavation amount S and the excavation time tf in expression (1) may be obtained. Also, a position at the start of excavation is the excavation start position in the excavation direction. FIG. 11 illustrates an example of a relationship between an xz-axis and a reference point O. The vertically hatched region is an excavation region in an excavation target EX1.

Note that, in the solution process using the pseudospectral method, an expanded evaluation function, in which boundary conditions are included, shown in expression (27) may be used. When there is a design surface, information representing the design surface may be set in constraint conditions.

Here, the term TM21 represents a penalty for the initial condition and terminal condition. The term TM22 represents (−1)×bucket sweep area for a single excavation.

Where,

[ Math . 28 ]  Ξ i = Ξ ⁡ ( τ i ) ( 28 ) [ Math . 29 ]  U i = U ⁡ ( τ i ) ( 29 )

• • holds true.

The constraint conditions are listed below.

Note that, an equation of motion of the hydraulic excavator is given by expression (30).

[ Math . 30 ]  ξ . ( τ k ) = ∑ i = 0 N Ξ ⁡ ( τ i ) ⁢ D ki ( τ k ) = t f - t 0 2 ⁢ f ⁡ ( Ξ k , U k , τ k ; t 0 , t f ) ( 30 )

Expression (31) represents a constraint on a height of a bucket distal end at the initial and terminal times (see FIG. 12).

[ Math . 31 ]  z ⁡ ( τ 0 ) = z ⁡ ( τ f ) = 0 ( 31 )

Expression (32) represents a constraint on a bucket angle at the terminal time.

[ Math . 32 ]  ϕ ⁡ ( t f ) = - π ( 32 )

Expression (33) represents a constraint on a height of the bucket distal end.

[ Math . 33 ]  z ≦ 0 ( 33 )

Expression (34) represents a constraint on a horizontal speed of the bucket distal end.

[ Math . 34 ]  x . ≦ 0 ( 34 )

Expressions (35) and (36) represent constraints on a joint angular velocity.

[ Math . 35 ]  ω 2 ⁢ min ≦ ω 2 ≦ 0 ( 35 ) [ Math . 36 ]  ω 3 ⁢ min ≦ ω 3 ≦ 0 ( 36 )

Expressions (37) to (39) represent constraints on a joint angle.

[ Math . 37 ]  q 1 ⁢ min ≦ q 1 ≦ q 1 ⁢ max ( 37 ) [ Math . 38 ]  q 2 ⁢ min ≦ q 2 ≦ q 2 ⁢ max ( 38 ) [ Math . 39 ]  q 3 ⁢ min ≦ q 3 ≦ q 3 ⁢ max ( 39 )

Expressions (40) and (41) represent constraints on a joint torque.

[ Math . 40 ]  ❘ "\[LeftBracketingBar]" T 2 ❘ "\[RightBracketingBar]" ≦ T 2 ⁢ max ( q 2 ) ( 40 ) [ Math . 41 ]  ❘ "\[LeftBracketingBar]" T 3 ❘ "\[RightBracketingBar]" ≦ T 3 ⁢ max ( q 3 ) ( 41 )

Expression (42) represents a constraint on an engine output (n is an efficiency, and P1, P2, and P3 are joint outputs).

[ Math . 42 ]  ❘ "\[LeftBracketingBar]" P 1 ❘ "\[RightBracketingBar]" + ❘ "\[LeftBracketingBar]" P 2 ❘ "\[RightBracketingBar]" + ❘ "\[LeftBracketingBar]" P 3 ❘ "\[RightBracketingBar]" ≦ η ⁢ P max ( 42 )

Expression (43) represents a constraint on a bucket capacity.

[ Math . 43 ]  S ≦ 2. ( 43 )

(Processing after S14)

As described above, in step S14, the excavation-start-position determination unit 622 sets the excavation amount S [m³] and the excavation time tf [s] of the optimal trajectory, which are determined in the processing of calculating the optimal trajectory for one-pass excavation for each cross section at 10 degree intervals, as estimated values of the excavation amount S [m³] and the excavation time tf [s], and calculates the excavation start position.

On the other hand, in parallel with the processing of steps S11 to S14, the information acquisition unit 621 acquires hydraulic excavator position information (S15), and then acquires dump truck position information (S16). Note that, the information acquisition unit 621 may acquire, for example, position information acquired by the dump truck using a GNSS sensor of the dump truck as the dump truck position information via, for example, wireless communication such as a wireless local area network (LAN). Alternatively, the control device 61 may acquire the dump truck position information on its own by, for example, using the three-dimensional shape sensor 150 or the like.

Next, the excavation-start-position determination unit 622 calculates a relative position of the dump truck with respect to the hydraulic excavator (S17), and estimates the swing time tm [s] required for the loading swing and return swing for each cross section (S18). The swing time tm may be calculated by, for example, using a predetermined table or the like. The predetermined table defines a relationship between the angle and time on the basis of, for example, a rated swing speed in the specifications, the swing motor, a gear ratio, and the like.

Next, the excavation-start-position determination unit 622 calculates the evaluation index J for each cross section (excavation direction) (S19). Then, on the basis of results of comparing the evaluation index J between the cross sections, the excavation-start-position determination unit 622 determines the excavation direction and excavation start position (position of the bucket distal end 133T at the start of excavation) of the cross section in which the evaluation index J is maximum as the start position of the excavation operation. Next, the operation-command-signal generation unit 624 generates and outputs an operation command signal to excavate the cross section with the maximum evaluation index (S20), and ends the processing shown in FIG. 4.

FIG. 13 shows an example of calculation of the evaluation index J, the excavation volume S, the excavation time tf, and the swing time tm. In the example shown in FIG. 13, the excavation amount (excavation volume S) in an excavation direction of 80 degrees is the largest, but the excavation time tf and the swing time tm in an excavation direction of 100 degrees are relatively small. Then, the evaluation index S in the excavation direction of 100 degrees is the largest. In this case, the excavation direction of 100 degrees is selected as the start position for the excavation operation.

(Other Configurations in Control Device)

The operation-command-switching control unit 623 controls the operation-command switching unit 64 to cause either an operation command signal (manual) or an operation command signal (automatic) to be output from the operation-command switching unit 64. The operation command signal (manual) (also referred to as a first operation command signal) is generated in response to an operator's operation for the operation device 143. The operation command signal (automatic) (also referred to as a second operation command signal) is generated by the operation-command-signal generation unit 624. For example, when the operation-command-signal generation unit 624 generates and outputs the operation command signal (automatic), the operation-command-switching control unit 623 selects the operation command signal (automatic). Then, the operation-command-switching control unit 623 causes the operation command signal (automatic) to be output from the operation-command switching unit 64.

The operation-command-signal generation unit 624 generates and outputs an operation command signal on the basis of the start position of the excavation operation determined by the excavation-start-position determination unit 622, information representing the three-dimensional shape of the terrain acquired by the information acquisition unit 621, relative position information with respect to the dump truck 200, and the like. The operation command signal is a signal for automatically executing the excavation operation, the loading swing, the dumping operation, and the return swing of the work machine 100.

The operation-command switching unit 64 outputs either the operation command signal (manual) or the operation command signal (automatic) under the control of the operation-command-switching control unit 623.

(Operation and Effects)

According to the present embodiment, when the excavation operation, the dumping operation, and the loading swing and return swing between the excavation operation and the dumping operation are automatically performed by the work equipment 130, the start position of the excavation operation is determined for each single excavation operation on the basis of at least the excavation time required for the excavation operation and the swing time required for the loading swing and return swing. According to this configuration, the start position of the excavation operation (the excavation direction and the position of the bucket distal end at the start of excavation) is determined for each single excavation operation, taking into account the swing direction. Therefore, it is possible to maintain efficiency in the automatic excavation operation easily.

Although an embodiment of the present invention has been described above with reference to the drawings, the specific configurations are not limited to the above-described embodiment, and may include design changes or the like within a range not departing from the gist of the present invention. Also, a part or all of the programs executed by the computer in the above-described embodiment may be distributed via a computer-readable recording medium or a communication line.

(Additional Statement 1)

A control device of a work machine including a swing body swinging around a swing center and work equipment attached to the swing body, including:

• • an excavation-start-position determination unit determining a start position of an excavation operation for each single excavation operation on the basis of at least an excavation time required for the excavation operation and a swing time required for a loading swing and a return swing when the excavation operation, a dumping operation, and the loading swing and the return swing between the excavation operation and the dumping operation are automatically performed by the work equipment.

(Additional Statement 2)

The control device according to (Additional statement 1), in which the excavation-start-position determination unit determines a start position of the excavation operation for each single excavation operation on the basis of an estimated value of an excavation amount for the single excavation operation, the excavation time, and the swing time.

(Additional Statement 3)

The control device according to (Additional statement 2), in which the excavation-start-position determination unit determines a start position of the excavation operation for each single excavation operation on the basis of the estimated value of the excavation amount, the excavation time, a dumping time required for the dumping operation, and the swing time.

(Additional Statement 4)

The control device according to (Additional statement 2) or (Additional statement 3), in which the excavation-start-position determination unit determines a start position of the excavation operation for each single excavation operation on the basis of a value obtained by dividing the estimated value by a total value of the excavation time and the swing time.

(Additional Statement 5)

The control device according to (Additional statement 2), (Additional statement 3), or (Additional statement 4), in which the excavation-start-position determination unit obtains the estimated value, the excavation time, and the swing time for a plurality of excavation directions, and determines the start position on the basis of comparison results between the plurality of excavation directions.

(Additional Statement 6) The control device according to any one of (Additional statement 2) to (Additional statement 5), in which the excavation-start-position determination unit estimates the estimated value and the excavation time on the basis of a two-dimensional cross section obtained for each of the excavation directions from a three-dimensional shape of an excavation target in the excavation operation.

(Additional Statement 7)

The control device according to any one of (Additional statement 1) to (Additional Statement 6), in which the excavation-start-position determination unit calculates an optimal excavation trajectory for each single excavation operation.

(Additional Statement 8)

The control device according to (Additional statement 7), in which the excavation trajectory is determined by an angular velocity or a cylinder speed in a time series.

REFERENCE SIGNS LIST

• • 100 Work machine
  • 110 Undercarriage
  • 120 Swing body
  • 130 Work equipment
  • 133 Bucket
  • 140 Cab
  • 143D Display input device
  • 60 Control system
  • 61 Control device
  • 62 Automatic excavation/swing/dumping control unit
  • 622 Excavation-start-position determination unit
  • 623 Operation-command-switching control unit
  • 624 Operation-command-signal generation unit