AU2020414620A1

AU2020414620A1 - System and method for controlling work machine

Info

Publication number: AU2020414620A1
Application number: AU2020414620A
Authority: AU
Inventors: Masami Hirayama
Original assignee: Komatsu Ltd
Current assignee: Komatsu Ltd
Priority date: 2019-12-26
Filing date: 2020-12-07
Publication date: 2022-04-14
Anticipated expiration: 2040-12-07
Also published as: US20220389679A1; JP2021105258A; WO2021131645A1; CA3155835A1; AU2020414620B2

Abstract

A controller determines a plurality of candidate paths. Each of the plurality of candidate paths crosses a first excavation wall from a first slot to a second slot, and extends in one of a plurality of directions. The controller calculates an evaluation function of a route search algorithm for each of the plurality of candidate paths. The controller determines the path having the optimal evaluation function, among the plurality of candidate paths, as a first excavation path. The controller controls a work machine along the first excavation path.

Description

SYSTEM AND METHOD FOR CONTROLLING WORK MACHINE TECHNICAL FIELD

[0001] The present disclosure relates to a system and a method for controlling a work machine.

BACKGROUNDART

[0002] Slot dozing is work performed by a work machine. In slot dozing, an actual topography

of a work site is dug by a work implement, whereby a plurality of slots are formed on the actual

topography. Moreover, digging walls are formed between the plurality of slots. The digging

walls are berms left along the slots.

[0003] Patent Document 1 describes a start condition for work to dig and remove the digging

walls. For example, the controller determines whether to start digging of a digging wall based on

the difference in the depths of the slots adjacent to the digging wall on both sides or the width of the

digging wall.

CITATION LIST PATENT DOCUMENT

[0004] Patent Document 1: US Patent No. 9, 469, 967

SUMMARY OF THE INVENTION

Technical Problem

[0005] However, a specific operation of the work machine for digging the digging walls is not

disclosed in Patent Document 1. The digging work of the digging walls requires skill. Therefore,

the digging work of the digging walls is not easy for an inexperienced operator. An object of the

present disclosure is to easily perform digging work of digging walls with automatic control of the

work machine.

SOLUTION TO PROBLEM

[0006] A system according to a first aspect of the present disclosure is a system for controlling a

work machine. The system according to the present aspect includes a position sensor and a

controller. The position sensor outputs position data indicative of a position of the work machine.

The controller acquires the position data. The controller acquires actual topography data. The

actual topography data includes a position of a first slot, a position of a second slot, and a position of

a first digging wall. The first slot extends in a predetermined work direction. The second slot is

positioned adjacent to the first slot. The first digging wall is positioned between the first slot and

the second slot.

[0007] The controller determines a plurality of candidate paths. The plurality of candidate

paths cross the first digging wall from the first slot toward the second slot and extend in respective

directions. The controller calculates an evaluation function of a path search algorithm for each of

the plurality of candidate paths. The controller determines a candidate path having an optimal

evaluation function of the plurality of candidate paths as a first digging path. The controller

controls the work machine according to the first digging path.

[0008] A method according to a second aspect of the present disclosure is a method for

controlling a work machine. The method according to the present aspect includes the following

processes. A first process is to acquire position data indicative of a position of the work machine.

A second process is to acquire actual topography data. The actual topography data includes a

position of a first slot, a position of a second slot, and a position of afirst digging wall. The first

slot extends in a predetermined work direction. The second slot is positioned adjacent to the first

slot. The first digging wall is positioned between the first slot and the second slot.

[0009] A third process is to determine a plurality of candidate paths. The plurality of candidate

directions. A fourth process is to calculate an evaluation function of a path search algorithm for

each of the plurality of candidate paths. A fifth process is to determine a candidate path having an

optimal evaluation function of the plurality of candidate paths as a first digging path. A sixth

process is to control the work machine according to the first digging path. The order in which the

above processes are executed is not limited to the order described above and may be changed.

ADVANTAGEOUS EFFECTS OF INVENTION

[0010] According to the present disclosure, digging work of digging walls can be easily

performed with automatic control of the work machine.

BRIEF DESCRIPTION OF DRAWINGS

[0011] FIG.1 is a side view of a work machine according to an embodiment.

FIG. 2 is a block diagram illustrating a configuration of a drive system and a control system of the

work machine.

FIG. 3 is a side view of an actual topography at a work site.

FIG. 4 is a perspective view illustrating an example of slots and digging walls formed on the actual

topography.

FIG. 5 is a flowchart illustrating processes of automatic control of the work machine.

FIG. 6 is a top view illustrating an example of the actual topography.

FIG. 7 is a view illustrating an example of a travel path.

FIG. 8 is a view illustrating the example of the travel path.

FIG. 9 is a view illustrating the example of the travel path.

FIG. 10 is an enlarged view of a first travel path and a second travel path.

FIG. 11 is an enlarged view of an m-th travel path.

FIG. 12 is a flowchart illustrating processes for determining a digging path.

FIG. 13 is a view illustrating an example of candidate paths of a digging path.

FIG. 14 is a block diagram illustrating a configuration of the drive system and the control system of

the work machine according to another embodiment.

FIG. 15 is a view illustrating an example of the travel path according to a modified example.

FIG. 16 is a view illustrating the example of the travel path according to the modified example.

FIG. 17 is a view illustrating the example of the travel path according to the modified example.

DESCRIPTION OF EMBODIMENTS

[0012] A system and a method for controlling a work machine 1 according to an embodiment

will be described with reference to the drawings. FIG.1 is a side view of the work machine 1

according to the embodiment. The work machine 1 according to the present embodiment is a

bulldozer. The work machine 1 includes a vehicle body 11, a travel device 12, and a work

implement 13.

[0013] The vehicle body 11 includes an operating cabin 14 and an engine compartment 15. A

operator's seat that is not illustrated is disposed in the operating cabin 14. The engine compartment

is disposed in front of the operating cabin 14. The travel device 12 is attached to a bottom part

of the vehicle body 11. The travel device 12 has a pair of left and right crawler belts 16. Only the

left crawler belt 16 is illustrated in FIG. 1. The work machine 1 travels due to the rotation of the

crawler belts 16.

[0014] The work implement 13 is attached to the vehicle body 11. The work implement 13

includes a lift frame 17, a blade 18, and a lift cylinder 19. The lift frame 17 is attached to the

vehicle body 11 such as to be movable up and down. The lift frame 17 supports the blade 18.

[0015] The blade 18 is disposed in front of the vehicle body 11. The blade 18 moves up and

down accompanying the up and down movements of the lift frame 17. The lift cylinder 19 is

coupled to the vehicle body 11 and the lift frame 17. Due to the extension and contraction of the lift

cylinder 19, the lift frame 17 moves up and down.

[0016] FIG. 2 is a block diagram illustrating a configuration of a drive system 2 and a control

system 3 of the work machine 1. As illustrated in FIG. 2, the drive system 2 includes an engine 22,

a hydraulic pump 23, and a power transmission device 24.

[0017] The hydraulic pump 23 is driven by the engine 22 to discharge hydraulic fluid. The

hydraulic fluid discharged from the hydraulic pump 23 is supplied to a hydraulic actuator 25. The

hydraulic actuator 25 includes the above-mentioned lift cylinder 19. Although one hydraulic pump

23 is illustrated in FIG. 2, a plurality of hydraulic pumps may be provided.

[0018] A control valve 26 is disposed between the hydraulic actuator 25 and the hydraulic pump

23. The control valve 26 is a proportional control valve and controls the flow rate of the hydraulic

fluid supplied from the hydraulic pump 23 to the lift cylinder 19. The control valve 26 may be a pressure proportional control valve. Alternatively, the control valve 26 may be an electromagnetic proportional control valve.

[0019] The power transmission device 24 transmits driving force of the engine 22 to the travel

device 12. The power transmission device 24 may be, for example, a transmission having a torque

converter or a plurality of transmission gears. Alternatively, the power transmission device 24 may

be another type of power transmission device such as a hydro static transmission (HST).

[0020] The control system 3 includes a controller 31, a machine position sensor 32, a

communication device 33, a storage 34, and an input device 35. The controller 31 is programmed

to control the work machine 1 based on acquired data. The controller 31 includes a memory 38 and

a processor 39. The memory 38 includes, for example, a random access memory (RAM) and a

read only memory (ROM). The storage 34 includes, for example, a semiconductor memory, a hard

disk, or the like. The memory 38 and the storage 34 record computer commands and data for

controlling the work machine 1.

[0021] The processor 39 is, for example, a CPU, but may be another type of processor 39. The

processor 39 executes processes for controlling the work machine 1 based on the computer

commands and data stored in the memory 38 or the storage 34. The communication device 33 is,

for example, a module for wireless communication and communicates with a device outside of the

work machine 1. The communication device 33 may be a device that uses a mobile

communication network. Alternatively, the communication device 33 may be a device that uses a

local area network (LAN) or another network such as the Internet.

[0022] The machine position sensor 32 detects a position of the work machine 1. The machine

position sensor 32 includes, for example, a global navigation satellite system (GNSS) receiver such

as a global positioning system (GPS). The machine position sensor 32 is mounted on the vehicle

body 11. Alternatively, the machine position sensor 32 may be mounted on another position such

as on the work implement 13. The controller 31 acquires current position data indicative of a

current position of the work machine 1 from the machine position sensor 32.

[0023] The input device 35 is operable by an operator. The input device 35 includes, for

example, a touch screen. Alternatively, the input device 35 may include another operating element such as hardware keys. The input device 35 receives an operation by an operator and outputs a signal indicative of the operation by the operator to the controller 31.

[0024] The controller 31 outputs command signals to the engine 22, the hydraulic pump 23, the

power transmission device 24, and the control valve 26, thereby controlling said devices. For

example, the controller 31 controls the displacement of the hydraulic pump 23 and the opening

degree of the control valve 26 to operate the hydraulic actuator 25. As a result, the work implement

13 can be operated.

[0025] The controller 31 controls the rotation speed of the engine 22 and the power transmission

device 24 to cause the work machine 1 to travel. For example, when the power transmission device

24 is an HST, the controller 31 controls the displacement of the hydraulic pump and the

displacement of a hydraulic motor of the HST. When the power transmission device 24 is a

transmission having a plurality of transmission gears, the controller 31 controls an actuator for gear

shifting. Further, the controller 31 controls the power transmission device 24 so as to bring about a

speed difference between the left and right crawler belts 16, thereby causing the work machine 1 to

turn.

[0026] Next, automatic control of the work machine 1 executed by the controller 31 will be

described. The controller 31 controls the engine 22 and the power transmission device 24, thereby

causing the work machine 1 to travel automatically. Further, the controller 31 controls the engine

22, the hydraulic pump 23, and the control valve 26, thereby automatically controlling the work

implement 13.

[0027] FIG. 3 is a side view of an actual topography 40 at a work site. As illustrated in FIG. 3,

the work machine 1 determines a target design surface 41. At least a portion of the target design

surface 41 is positioned below the actual topography 40. The target design surface 41 extends in a

predetermined work direction Al. The target design surface 41 may be determined in advance and

stored in the storage 34. The controller 31 may determine the target design surface 41 from the

actual topography 40. Alternatively, the target design surface 41 may be input by an operator via

the input device 35.

[0028] The controller 31 determines a start position 101 of digging on the actual topography 40.

For example, the controller 31 may determine the start position 101 based on the amount of soil to be

dug. The controller 31 controls the work machine 1 to cause the work machine 1 to move from the

start position 101 to a dumping position D1. Asa result, the actual topography 40 is dug from the

start position 101 and the dug soil is transported to the dumping position D1.

[0029] Next, the controller 31 causes the work machine 1 to move to a next start position 102

positioned behind the previous start position 101. Then, the controller 31 controls the work

machine 1 to cause the work machine 1 to move from the start position 102 to the dumping position

D1. As a result, the actual topography 40 is dug from the start position 102 and the dug soil is

transported to the dumping position D1. By repeating the above operations, as illustrated in FIG. 4,

a first slot S extending in the predetermined work direction Al is formed on the actual topography

40. The control for generating the first slot SI is not limited to the control described above and may

be changed.

[0030] The controller 31 controls the work machine 1, whereby a plurality of slots S Ito S4 are

formed on the actual topography 40 in order. The plurality of slots Si to S4 are aligned in a lateral

direction. The lateral direction is a direction intersecting the predetermined work direction Al.

The plurality of slots Si to S4 are disposed apart from each other. Therefore, digging walls WI to

W3 are formed between the slots Si to S4. The following is an explanation of automatic control of

digging work of the digging walls WI to W3 performed by the work machine 1 at the work site.

[0031] FIG. 5 is a flowchart illustrating processes of automatic control of the work machine 1.

As illustrated in FIG. 5, instep S101, the controller 31 acquires current position data. Thecontroller

31 acquires the current position data from the machine position sensor 32.

[0032] In step S102, the controller 31 acquires actual topography data. The actual topography

data is data indicative of the actual topography 40 at the work site. For example, the actual

topography data includes plane coordinates and heights of a surface of the actual topography 40.

The actual topography data includes positions of the above-mentioned slots Si to S4 and digging

walls WI to W3.

[0033] FIG. 6 is a top view illustrating an example of the actual topography 40. The controller

31 performs digging work of the digging walls WI to W3 in a work area 100 at the work site. The work area 100 maybe determined in advance and stored in the storage 34. Thework area 100 may be automatically determined by the controller 31. Alternatively, the work area 100 maybe input by an operator via the input device 35.

[0034] In the example illustrated in FIG. 6, the actual topography 40 in the work area 100

includes the first to fourth slots Sl to S4. The first to fourth slots Sl to S4 extend in the

predetermined work direction Al. The first to fourth slots Sl to S4 are aligned in the lateral

direction. The first to fourth slots Sl to S4 are disposed apart from each other. The actual

topography 40 in the work area 100 includes the first to third digging walls WI to W3. The first

digging wall WI is positioned between the first slot Sl and the second slot S2. The second digging

wall W2 is positioned between the second slot S2 and the third slot S3. The third digging wall W3

is positioned between the third slot S3 and the fourth slot S4. The first to third digging walls WI to

W3 extend in the predetermined work direction Al.

[0035] The actual topography data may be stored in the storage 34 in advance. The controller

31 may acquire the actual topography data by recording trajectories of the work implement 13 or the

bottom of the travel device 12. Alternatively, the actual topography data may be measured by a

measuring device such as a laser imaging detection and ranging (LIDAR) or a camera. The

controller 31 may acquire the actual topography data from the measuring device. The measuring

device may be mounted on the work machine 1. The measuring device may be disposed outside of

the work machine 1.

[0036] In step S103, the controller 31 acquires dumping positions D1 to D4. The dumping

positions Di to D4 are positioned in front of the slots S to S4 in the predetermined work direction

Al. In the example illustrated in FIG. 6, the dumping positions D1 to D4 include the first to fourth

dumping positions D1 to D4. The first to fourth dumping positions D1 to D4 are respectively

positioned in front of the first to fourth slots Si to S4 in the predetermined work direction Al.

[0037] In step S104, the controller 31 determines travel paths P1 to Pn. FIGS. 7 to 9 are views

illustrating an example of the travel paths P1 to Pn. As illustrated in FIGS. 7 to 9, the controller 31

determines a plurality of travel paths P1to Pn for dumping all the digging walls WI to W3 in the

work area 100 at the dumping positions Di to D4. In the example illustrated in FIGS. 7 to 9, the controller 31 allocates the first to n-th travel paths P1to Pn to the digging walls W Ito W3 in order in the lateral direction.

[0038] Specifically, as illustrated in FIG. 7, the controller 31 allocates the first to third travel

paths P1 to P3 to the first to third digging walls WI to W3 in order. As illustrated in FIG. 8, the

controller 31 reverses the order of allocation in the opposite direction at the third digging wall W3.

The controller 31 allocates the fourth to sixth travel paths P4 to P6 in order from the remaining

portion of the third digging wall W3 to the remaining portion of the first digging wall WI. As

illustrated in FIG. 9, the controller 31 reverses the order of allocation in the opposite direction at the

first digging wall WI. In the same manner as described above, the controller 31 allocates the

seventh to n-th travel paths P7 to Pn in order from the remaining portion of the first digging wall WI

to the remaining portion of the third digging wall W3.

[0039] FIG. 10 is an enlarged view of the first travel path P1 and the second travel path P2. As

illustrated in FIG. 10, the first travel path P1 includes a first digging path PA, a first soil

transportation path PB1, and a first reverse path PCi. The first digging path PAl includes a straight

line crossing the first digging wall WI from the first slot Sl toward the second slot S2. The first

digging path PAl is inclined with respect to the predetermined work direction Al. Thefirstdigging

path PAl extends from a start position STI at the first slot Sl side to a position on the second slot S2.

[0040] The first soil transportation path PB1 is a straight line extending from the first digging

path PAl to the second dumping position D2. The first soil transportation path PB1 extends in the

predetermined work direction Al on the second slot S2. The controller 31 determines the first soil

transportation path PB1 from the first digging path PAl and the second dumping position D2. The

first reverse path PCi extends from the second dumping position D2 to a next start position ST2.

The controller 31 determines the first reverse path PCi from the first digging path PAl, the second

dumping position D2, and the next start position ST2.

[0041] The second travel path P2 includes a second digging path PA2, a second soil

transportation path PB2, and a second reverse path PC2. The second digging path PA2 includes a

straight line crossing the second digging wall W2 from the second slot S2 toward the third slot S3.

The second digging path PA2 is inclined with respect to the predetermined work direction Al. The second digging path PA2 extends from the start position ST2 at the second slot S2 side to a position on the third slot S3.

[0042] The second soil transportation path PB2 is a straight line extending from the second

digging path PA2 to a third dumping position D3. The second soil transportation path PB2 extends

in the predetermined work direction Al on the third slot S3. The controller 31 determines the

second soil transportation path PB2 from the second digging path PA2 and the third dumping

position D3. The second reverse path PC2 extends from the third dumping position D3 to a next

start position ST3. The controller 31 determines the second reverse path PC2 from the second

digging path PA2, the third dumping position D3, and the next start position ST3. Similarly to the

first travel path P1 and the second travel path P2, other travel paths also include a digging path, a soil

transportation path, and a reverse path.

[0043] The controller 31 determines the start positions STI to STn based on, for example, the

positions of the digging walls WI to W3. The controller 31 may determine, as the start positions

STI to STn, positions spaced apart by a predetermined distance from the digging wall WI to W3.

Alternatively, the controller 31 may set arbitrary start lines and determine positions on the start lines

as the start positions STI to STn.

[0044] In step S105, the controller 31 controls the work machine 1 according to the travel paths

P1 to Pn. For example, as illustrated in FIG. 10, the controller 31 controls the work machine 1

according to the first travel path Pl. Specifically, the controller 31 causes the work machine 1 to

move along the first digging path PAL. The controller 31 causes the work machine 1 to move along

the first soil transportation path PB1 subsequent to the first digging path PAL. The controller 31

causes the work machine 1 to move along the first reverse path PCi subsequent to the first soil

transportation path PB1. As a result, the work machine 1 digs a part or entire of thefirst digging

wall WI and dumps the dug soil at the second dumping position D2.

[0045] The controller 31 controls the work machine 1 according to the second travel path P2

subsequent to the first travel path Pl. Specifically, the controller 31 causes the work machine 1 to

move from the start position ST2 along the second digging path PA2. The controller 31 causes the

work machine 1 to move along the second soil transportation path PB2 subsequent to the second digging path PA2. The controller 31 causes the work machine 1 to move along the second reverse path PC2 subsequent to the second soil transportation path PB2. As a result, the work machine 1 digs a part or entire of the second digging wall W2 and dumps the dug soil at the third digging position D3.

[0046] Hereinafter, as illustrated in FIGS. 7 to 9, the controller 31 controls the work machine 1

so that the work machine 1 travels along the first to n-th travel paths P1 to Pn in order and the

digging walls WI to W3 are dug with the work implement 13. As illustrated in FIG. 9, the travel

paths P7 to Pn when the last portions of each of the digging walls WI to W3 are dug may extend in

the predetermined work direction Al along the digging walls WI to W3, respectively. Alternatively,

the travel paths P7 to Pn may extend in a direction inclined with respect to the predetermined work

direction A1, similarly to other travel paths.

[0047] Next, processes for determining the digging path will be described below. FIG. 11 is an

enlarged view of the m-th travel path Pm (1 m < n). The m-th travel path Pm is an arbitrary travel

path of the first to n-th travel paths P1 to Pn. As illustrated in FIG. 11, the m-th travel path Pm

includes an m-th digging path PAm, an m-th soil transportation path PBm, and an m-th reverse path

PCm.

[0048] FIG. 12 is a flowchart illustrating processes for determining the digging path. As

illustrated in FIG. 12, in step S201, the controller 31 determines candidate paths Mij of the m-th

digging path PAm. The controller 31 determines the candidate paths Mij of the m-th digging path

PAm based on the actual topography data. FIG. 13 is a view illustrating an example of the

candidate paths Mij of the m-th digging path PAm. As illustrated in FIG. 13, the candidate paths

Mij of the m-th digging path PAm extend from each of reference points Ri (i = 1, 2, ... ) in a plurality

of directions and are defined by straight lines crossing an m-th digging wall Wm.

[0049] The controller 31 determines a reference point Ri on the m+1-th slot Sm+1. The

controller 31 determines one or more reference points Ri along the centerline of the m+1-th slot

Sm+1. For example, the controller 31 determines positions at certain intervals along the centerline

of the m+1-th slot Sm+1 as the reference points Ri. The candidate paths Mij of the m-th digging

path PAm extend in different directions by a predetermined angle a. For example, the candidate paths Mij of the m-th digging path PAm may extend from a predetermined reference line in different directions by the predetermined angle a. The reference line may be determined in consideration of work efficiency. The predetermined angle a may be determined in consideration of the work efficiency and the calculation costs of the controller 31.

[0050] In step S202, the controller 31 calculates an evaluation function for each of the candidate

paths Mij of the first digging path PAL. The evaluation function is, for example, a function of the

A* algorithm. The evaluation function may be a function of another path search algorithm such as

the Dijkstra algorithm or the greedy algorithm. The evaluation function is represented by the

following equation (1).

f(m)=g(m)+h(m) (1) The function g(m) represents work time of the work machine 1. h(m) represents the amount of

remaining soil in the digging walls WI to W3. The work time of the work machine 1 is, for

example, the moving time from the start position STm to the next start position STm+1 via the m-th

dumping position Dm+1. The controller 31 calculates the work time from, for example, the set

vehicle speed, the moving distance, and the traction force of the work machine 1.

[0051] In step S203, the controller 31 determines a candidate path Mij having a smallest

evaluation function f(m) of the plurality of candidate paths Mi,j as the m-th digging path. That is,

the controller 31 determines the candidate path Mij having the smallest evaluation function f(m) of

the plurality of candidate paths Mij as the m-th digging path PAm. The controller 31 determines

the m-th travel path Pm based on the m-th digging path PAm.

[0052] In step S204, the controller 31 determines whether the remaining soil amount Vr of the

digging walls W Ito W3 is equal to or less than a predetermined threshold Vth. The predetermined

threshold Vth may be zero. The predetermined threshold Vth may be a small value to a degree that

assumes that substantially all of the digging walls WI to W3 has been dumped. When the

remaining soil amount Vr of the digging walls WI to W3 is not equal to or less than the

predetermined threshold Vth, the process returns to step S201 and the controller 31 determines a next

travel path. When the remaining soil amount Vr of the digging walls WI to W3 is equal to or less

than the predetermined threshold Vth, the controller 31 stops determining the travel path. That is, the controller 31 repeats determining the travel paths until the remaining soil amount Vr of the digging walls W Ito W3 is equal to or less than the predetermined threshold Vth.

[0053] In the system and method for controlling the work machine 1 according to the present

embodiment described above, the plurality of candidate paths Mij crossing the digging walls WI to

W3 are determined. Then, a candidate path Mij having the smallest evaluation function f(m) of the

plurality of candidate paths Mij is determined as the digging path PAm. Therefore, the digging

work of the digging walls can be easily performed with the automatic control of the work machine 1.

[0054] Although one embodiment of the present invention has been described so far, the present

invention is not limited to the above embodiment and various modifications can be made without

departing from the gist of the invention. The work machine 1 is not limited to the bulldozer and

may be another machine such as a wheel loader. The travel device may include tires instead of the

crawler belts. The work machine 1 may be a vehicle that can be remotely operated. In this case,

the operating cabin may be omitted from the work machine 1.

[0055] A portion of the control system 3 may be disposed outside of the work machine 1. For

example, the controller 31 may have a plurality of controllers 31 separate from each other. As

illustrated in FIG. 14, the controller 31 may include a remote controller 311 disposed outside of the

work machine 1 and an onboard controller 312 mounted on the work machine 1. The remote

controller 311 and the onboard controller 312 may be able to wirelessly communicate with each

other via the communication devices 33 and 36. A portion of the above-mentioned functions of the

controller 31 may be executed by the remote controller 311 and the remaining functions may be

executed by the onboard controller 312. For example, the processes for determining the digging

path may be executed by the remote controller 311 and the processes for causing the work machine 1

to move may be executed by the onboard controller 312.

[0056] The automatic control of the work machine 1 may be a semi-automatic control that is

performed in combination with manual operation by an operator. Alternatively, the automatic

control may be a fully automatic control that is performed without manual operation by an operator.

For example, as illustrated in FIG. 14, the work machine 1 may be remotely operated by an operator

operating an operating device 37 disposed outside of the work machine 1.

[0057] The processes for performing digging work of the digging walls are not limited to the

above-mentioned processes and may be changed. For example, some of the above processes may

be changed or omitted. A process that is different from the above processes may be added to the

processes for performing digging work of the digging walls.

[0058] The plurality of work machines 1 may simultaneously perform digging work of the

digging walls. In this case, each of the controllers mounted on the plurality of work machines 1

may autonomously execute the above control. Alternatively, a controller that is common to the

plurality of work machines 1 may execute the above control for the plurality of work machines 1.

[0059] The order of digging of the digging walls is not limited to that of the above embodiment

and may be changed. For example, as illustrated in FIGS. 15 to 17, the controller 31 may

determine the travel paths P1 to P3 in order from a starting end to a terminating end of the first

digging wall WI. Specifically, as illustrated in FIG. 15, the controller 31 determines the first travel

path P1 for the first digging wall WI. The first travel path P1 includes the first digging path PAl

crossing a first portion Wi1 of the first digging wall WI. The first portion Wi1 includes a starting

end of the first digging wall WI.

[0060] As illustrated in FIG. 16, the controller 31 determines the second travel path P2 for the

first digging wall WI. The second travel path P2 includes the second digging path PA2. The

second digging path PA2 is positioned in front of the first digging path PAL. The second digging

path PA2 crosses a second portion W12 of the first digging wall WI. The second portion W12 is

positioned in front of the first portion W11.

[0061] Subsequently, the controller 31 repeats determining the travel paths for the first digging

wall WI until the work machine 1 reaches the terminating end of the first digging wall WI. As

illustrated in FIG. 17, the controller 31 determines a k-th travel path Pk for the first digging wall WI.

The k-th travel path Pk includes a k-th digging path PAk. The k-th digging path PAk crosses a k-th

portion Wik of the first digging wall WI. The k-th portion Wik includes the terminating end of

the first digging wall WI.

[0062] After the digging of the first digging wall WI is finished, the controller 31 may

determine the travel paths in order from a starting end to a terminating end of the second digging wall W2. Subsequently, the controller 31 may determine the travel paths in order from a starting end to a terminating end of the third digging wall W3. In the above embodiment, the number of digging walls (m) is three. However, the number of digging walls (m) may be less than three or greater than three.

[0063] The method for determining the candidate paths is not limited to that of the above

embodiment and may be changed. For example, the reference point is not limited to being on the

centerline of the m+1-th slot Sm+1 and may be positioned apart from the centerline. The

evaluation function f (m) is not limited to the work time or the remaining soil amount and may

include another parameter. For example, the evaluation function f(m) may include the moving

distance or fuel consumption of the work machine 1. Alternatively, the evaluation function f(m)

may include a tipping probability based on the gradient of the actual topography.

[0064] In the above embodiment, the smallest evaluation function is regarded as an optimal

solution. However, a largest evaluation function may be regarded as an optimal solution. In this

case, the controller may determine a candidate path having a largest evaluation function of the

plurality of candidate paths as the digging path.

INDUSTRIAL APPLICABILITY

[0065] According to the present disclosure, the digging work of the digging walls can be easily

performed with the automatic control of the work machine.

REFERENCE SIGNS LIST

[0066] 1 Work machine

31 Controller

32 Machine position sensor

Sl First slot

S2 Second slot

Mij Candidate paths

PAl First digging path

PB1 First soil transportation path

PA2 Second digging path

Ri Reference point

W1 First digging wall

W2 Second digging wall

Claims

1. A system for controlling a work machine, the system comprising:

a position sensor configured to output position data indicative of a position of the work

machine; and

a controller configured to acquire the position data, wherein

the controller is configured to

acquire actual topography data, the actual topography data including a position of a

first slot extending in a predetermined work direction, a position of a second slot positioned adjacent

to the first slot, and a position of afirst digging wall positioned between the first slot and the second

slot,

determine a plurality of candidate paths crossing the first digging wall from the first

slot toward the second slot and extending in respective directions,

calculate an evaluation function of a path search algorithm for each of the plurality of

candidate paths,

determine a candidate path having an optimal evaluation function of the plurality of

candidate paths as a first digging path, and

control the work machine according to the first digging path.

2. The system according to claim 1, wherein

the controller is configured to

acquire a dumping position for the second slot,

determine a first soil transportation path extending from the first digging path to the

dumping position along the second slot, and

control the work machine according to the first soil transportation path subsequent to

the first digging path.

3. The system according to claim 2, wherein

the controller is configured to determine one or more reference points on the second slot, and determine the plurality of candidate paths so as to extend from the one or more reference points in the respective directions.

4. The system according to claim 2, wherein

the actual topography data further includes a position of a third slot positioned adjacent to

the second slot and a position of a second digging wall positioned between the second slot and the

third slot, and

the controller is configured to

determine a second digging path crossing the second digging wall from the second

slot toward the third slot, and

control the work machine according to the second digging path subsequent to the first

soil transportation path.

5. The system according to claim 2, wherein

the controller is configured to

determine a second digging path positioned in front of the first digging path and

crossing the first digging wall in the predetermined work direction, and

soil transportation path.

6. A method for controlling a work machine, the method comprising:

acquiring position data indicative of a position of the work machine;

acquiring actual topography data including a position of a first slot extending in a

predetermined work direction, a position of a second slot positioned adjacent to the first slot, and a

position of a first digging wall positioned between the first slot and the second slot;

determining a plurality of candidate paths crossing the first digging wall from the first slot

toward the second slot and extending in respective directions; calculating an evaluation function of a path search algorithm for each of the plurality of candidate paths; determining a candidate path having an optimal evaluation function of the plurality of candidate paths as a first digging path; and controlling the work machine according to the first digging path.

7. The method according to claim 6, further comprising:

acquiring a dumping position for the second slot;

determining a first soil transportation path extending from the first digging path to the

dumping position along the second slot; and

controlling the work machine according to the first soil transportation path subsequent to

the first digging path.

8. The method according to claim 7, further comprising:

determining one or more reference points on the second slot; and

determining the plurality of candidate paths so as to extend from the one or more reference

points in the respective directions.

9. The method according to claim 7, wherein

the actual topography data further includes a position of a third slot positioned adjacent to the

second slot and a position of a second digging wall positioned between the second slot and the third

slot,

the method further comprising:

determining a second digging path crossing the second digging wall from the second slot

toward the third slot; and

controlling the work machine according to the second digging path subsequent to the first

soil transportation path.

10. The method according to claim 7, further comprising:

determining a second digging path positioned in front of the first digging path and crossing

the first digging wall in the predetermined work direction; and

soil transportation path.