JP2024068831A - System and method for controlling work machine - Google Patents

Abstract

To quickly release a work machine from a slip state.SOLUTION: A work machine includes a vehicle body, a left drive wheel, a right drive wheel, a drive source, a drive device, a yaw angle sensor and a controller. The drive device rotates the left drive wheel and the right drive wheel by the drive force from the drive source. The yaw angle sensor detects an actual yaw angle speed of the vehicle body. The controller controls the drive device to turn the vehicle body by the difference in rotational speed between the left drive wheel and the right drive wheel. The controller calculates a theoretical yaw angle speed of the vehicle body in response to the control of the drive device. The controller obtains the actual yaw angle speed. The controller calculates the actual slip value of the vehicle body during the turn on the basis of the theoretical yaw angle speed and the actual yaw angle speed. The controller controls the rotational speed of at least one of the left drive wheel and the right drive wheel so that the actual slip value is a predetermined target slip value greater than 0.SELECTED DRAWING: Figure 4

Description

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

Some work machines turn the vehicle body by using a speed difference between the left and right drive wheels. For example, in the tracked vehicle of Patent Document 1, a clutch and a brake are connected to each of the left and right drive wheels. The tracked vehicle has left and right tracks, and the tracks are driven by the rotation of the left and right drive wheels. To turn the vehicle, the operator operates the steering lever. The vehicle controller sets a turn command in response to the operator's operation of the steering lever. Then, the controller controls the clutch and brake in response to the turn command, thereby creating a speed difference between the left and right drive wheels. This causes the vehicle body to turn.

JP 2000-142455 A

For example, when a work machine makes a small turn to change direction, or when making a small turn while working, the operator inputs a large turn command. At this time, if the load on the vehicle body is large, the vehicle body cannot turn and the outer track may slip violently. If such a slipping state continues, the vehicle body will wear out and a loss of driving force will occur. The purpose of this disclosure is to allow the work machine to quickly escape from a slipping state.

The system according to the first aspect of the present disclosure is a system for controlling a work machine. The work machine includes a vehicle body, a left drive wheel, a right drive wheel, a drive source, a drive unit, a yaw angle sensor, and a controller. The left drive wheel is rotatably supported by the vehicle body. The right drive wheel is rotatably supported by the vehicle body. The drive source is mounted on the vehicle body. The drive unit rotates the left drive wheel and the right drive wheel by the drive force from the drive source. The yaw angle sensor detects the actual yaw angular velocity of the vehicle body.

The controller controls the drive unit to turn the vehicle body using the difference in rotational speed between the left drive wheel and the right drive wheel. The controller calculates the theoretical yaw angular velocity of the vehicle body according to the control of the drive unit. The controller acquires the actual yaw angular velocity. The controller calculates an actual slip value indicating the amount of slip of the vehicle body during turning based on the theoretical yaw angular velocity and the actual yaw angular velocity. The controller controls the rotational speed of at least one of the left drive wheel and the right drive wheel so that the actual slip value becomes a predetermined target slip value greater than 0.

In the system according to this embodiment, when the actual slip value is greater than a predetermined target slip value, the rotational speed of at least one of the left and right drive wheels is controlled so that the actual slip value becomes the predetermined target slip value. This allows the work machine to quickly escape from the slip state.

In addition, in an environment in which a work machine is used, the work machine generates some slip even in a normal state. Therefore, even when the work machine is in a normal state, the slip ratio is not 0. In the system according to this aspect, the rotational speed of at least one of the left drive wheel and the right drive wheel is controlled so that the actual slip value becomes a predetermined target slip value that is greater than 0. This prevents the actual slip value from being excessively reduced.

A method according to a second aspect of the present disclosure is a method for controlling a work machine. The work machine includes a vehicle body, a left drive wheel, a right drive wheel, a drive source, and a drive unit. The left drive wheel is rotatably supported by the vehicle body. The right drive wheel is rotatably supported by the vehicle body. The drive source is mounted on the vehicle body. The drive unit rotates the left drive wheel and the right drive wheel by drive force from the drive source.

The method includes controlling a drive unit to turn the vehicle body using the difference in rotational speed between the left and right drive wheels, calculating a theoretical yaw angular velocity of the vehicle body according to the control of the drive unit, acquiring an actual yaw angular velocity of the vehicle body, calculating an actual slip value of the vehicle body during turning based on the theoretical yaw angular velocity and the actual yaw angular velocity, and controlling the rotational speed of at least one of the left and right drive wheels so that the actual slip value becomes a predetermined target slip value greater than 0.

The method according to this aspect allows the work machine to quickly escape from a slip state. In addition, excessive reduction in the actual slip value is suppressed.

A method according to a third aspect of the present disclosure is a method for controlling a work machine. The work machine includes a vehicle body, a left drive wheel, a right drive wheel, a drive source, and a drive unit. The left drive wheel is rotatably supported by the vehicle body. The right drive wheel is rotatably supported by the vehicle body. The drive source is mounted on the vehicle body. The drive unit rotates the left drive wheel and the right drive wheel by drive force from the drive source.

The method includes controlling a drive unit to turn the vehicle body using the difference in rotational speed between the left and right drive wheels, acquiring the rotational speed of the left drive wheel, acquiring the rotational speed of the right drive wheel, calculating a theoretical yaw angular velocity of the vehicle body based on the rotational speed of the left drive wheel and the rotational speed of the right drive wheel, acquiring an actual yaw angular velocity of the vehicle body, calculating an actual slip value of the vehicle body during turning based on the theoretical yaw angular velocity and the actual yaw angular velocity, and controlling the rotational speed of at least one of the left and right drive wheels to reduce the actual slip value if the actual slip value is greater than a predetermined target slip value.

In the method according to this aspect, when the actual slip value is greater than a predetermined target slip value, the rotational speed of at least one of the left and right drive wheels is controlled so as to reduce the actual slip value. This allows the work machine to quickly escape from the slip state. In addition, the theoretical yaw angular velocity of the vehicle body is calculated based on the rotational speed of the left and right drive wheels. Therefore, the theoretical yaw angular velocity is calculated with higher accuracy than when the theoretical yaw angular velocity is calculated based on the amount of operation of the drive wheel operating lever, for example.

This disclosure allows the work machine to quickly escape from a slipping state.

1 is a perspective view of a work machine according to an embodiment. FIG. FIG. FIG. 1 is a schematic diagram showing a configuration of a work machine. FIG. 4 is a block diagram showing a process of slip control. FIG. 2 is a schematic diagram showing the configuration of a work machine according to a first modified example. FIG. 13 is a schematic diagram showing the configuration of a work machine according to a second modified example. FIG. 13 is a schematic diagram showing the configuration of a work machine according to a third modified example. FIG. 13 is a schematic diagram showing the configuration of a work machine according to a fourth modified example. FIG. 13 is a schematic diagram showing the configuration of a work machine according to a fifth modified example.

The control system and control method for a work machine according to an embodiment will be described below with reference to the drawings. FIG. 1 is a side view showing a work machine 1 according to an embodiment. FIG. 2 is a top view of the work machine 1. The work machine 1 according to this embodiment is a bulldozer. The work machine 1 includes a vehicle body 11, a traveling device 12, and a work implement 13. The vehicle body 11 has a cab 14 and a power room 15. A driver's seat (not shown) is disposed in the cab 14. The power room 15 is disposed in front of the cab 14.

The traveling gear 12 is attached to the bottom of the vehicle body 11. The traveling gear 12 includes a left driving wheel 16, a right driving wheel 17, a left crawler belt 18, and a right crawler belt 19. The left driving wheel 16 and the right driving wheel 17 are rotatably supported by the vehicle body 11. The left crawler belt 18 is wound around the left driving wheel 16. The right crawler belt 19 is wound around the right driving wheel 17. The left and right driving wheels 16, 17 rotate to drive the left and right crawlers 18, 19, causing the work machine 1 to travel.

The work machine 13 is attached to the vehicle body 11. The work machine 13 includes lift frames 21, 22, a blade 23, lift cylinders 24, 25, and tilt cylinders 26, 27. The lift frames 21, 22 are attached to the vehicle body 11 so as to be movable up and down. The lift frames 21, 22 support the blade 23.

The blade 23 is disposed in front of the vehicle body 11. The blade 23 moves up and down in accordance with the up and down movement of the lift frames 21, 22. The lift cylinders 24, 25 are connected to the vehicle body 11 and the blade 23. Alternatively, the lift cylinders 24, 25 may be connected to the vehicle body 11 and the lift frames 21, 22. The lift frames 21, 22 move up and down as the lift cylinders 24, 25 extend and retract. The tilt cylinders 26, 27 are connected to the lift frames 21, 22 and the blade 23. The left and right ends of the blade 23 tilt up and down as the tilt cylinders 26, 27 extend and retract.

Figure 3 is a block diagram showing the configuration of the drive system 2 and control system 3 of the work machine 1. As shown in Figure 3, the drive system 2 includes a drive source 31 and a drive device 32. The drive source 31 and the drive device 32 are mounted on the vehicle body 11. The drive source 31 includes, for example, an internal combustion engine. The drive device 32 rotates the left drive wheel 16 and the right drive wheel 17 by the driving force from the drive source 31. The drive system 2 includes a hydraulic pump (not shown) for the work machine 13. The hydraulic pump for the work machine 13 is driven by the drive source 31 and discharges hydraulic oil for driving the cylinders 24-27 described above.

The drive device 32 includes a PTO (Power Take Off) 33, a transmission 34, a transfer 35, and a steering mechanism 36. The PTO 33 distributes the driving force from the drive source 31 to the transmission 34 and the steering mechanism 36. The transmission 34 is connected to the drive source 31 via the PTO 33. The transmission 34 includes, for example, a clutch and multiple speed change gears. The transmission 34 is connected to the left drive wheel 16 and the right drive wheel 17 via the transfer 35.

The drive device 32 includes a left clutch 37, a left brake 38, and a left link mechanism 39. The left clutch 37, the left brake 38, and the left link mechanism 39 are connected to the left driving wheel 16. The left clutch 37 switches between transmitting and cutting off the driving force from the transmission 34 to the left driving wheel 16. The left brake 38 brakes the left driving wheel 16. The left link mechanism 39 connects the left driving wheel 16 and the steering mechanism 36. The left link mechanism 39 includes, for example, a planetary gear mechanism.

The drive device 32 includes a right clutch 41, a right brake 42, and a right link mechanism 43. The right clutch 41, the right brake 42, and the right link mechanism 43 are connected to the right driving wheel 17. The right clutch 41 switches between transmitting and cutting off the driving force from the transmission 34 to the right driving wheel 17. The right brake 42 brakes the right driving wheel 17. The right link mechanism 43 connects the right driving wheel 17 and the steering mechanism 36. The right link mechanism 43 includes, for example, a planetary gear mechanism.

The steering mechanism 36 turns the vehicle body 11 by generating a rotational speed difference between the left drive wheel 16 and the right drive wheel 17. For example, the steering mechanism 36 turns the vehicle body 11 to the right by increasing the speed of the left drive wheel 16 more than that of the right drive wheel 17. The steering mechanism 36 turns the vehicle body 11 to the left by increasing the speed of the right drive wheel 17 more than that of the left drive wheel 16. The steering mechanism 36 includes a hydraulic pump 44 and a hydraulic motor 45.

The hydraulic pump 44 is connected to the drive source 31 via the PTO 33. The hydraulic pump 44 is driven by the drive source 31 to discharge hydraulic oil. The hydraulic motor 45 is connected to the hydraulic pump 44 via a hydraulic circuit 46. The hydraulic motor 45 is driven by the hydraulic oil discharged from the hydraulic pump 44. The hydraulic motor 45 is connected to the left driving wheel 16 via the left link mechanism 39. The hydraulic motor 45 is connected to the right driving wheel 17 via the right link mechanism 43. The hydraulic motor 45 is driven by the hydraulic oil from the hydraulic pump 44 to increase the speed of the left driving wheel 16 and the right driving wheel 17.

The control system 3 includes a controller 51. The controller 51 is programmed to control the work machine 1. The controller 51 includes memories such as RAM and ROM, and a processor such as a CPU. The controller 51 may include an auxiliary storage device such as an SSD or HDD. The controller 51 records programs and data for controlling the work machine 1. The controller 51 executes processing for controlling the work machine 1 based on the programs and data.

The control system 3 includes a gear shift operating member 52, a work machine operating member 53, a steering operating member 54, and an input device 55. The gear shift operating member 52 can be operated by an operator to switch the reduction ratio of the transmission 34. The gear shift operating member 52 is, for example, a lever, but may be other members such as a switch. The controller 51 controls the transmission 34 in response to the operation of the gear shift operating member 52. The work machine operating member 53 can be operated by an operator to operate the work machine 13. The work machine operating member 53 is, for example, a lever, but may be other members such as a switch. The controller 51 controls the work machine 13 in response to the operation of the work machine operating member 53.

The steering operation member 54 can be operated by an operator to turn the vehicle body 11 left and right. The steering operation member 54 is, for example, a lever, but may be other members such as a switch. The controller 51 controls the steering mechanism 36 in response to the operation of the steering operation member 54. The input device 55 can be operated by an operator to set the work machine 1. The input device 55 is, for example, a touch screen, but may be other members such as a switch.

The control system 3 includes a yaw angle sensor 56, a first velocity sensor 57, and a second velocity sensor 58. The yaw angle sensor 56 detects the actual yaw angular velocity of the vehicle body 11. The actual yaw angular velocity of the vehicle body 11 indicates the amount of change in the yaw angle of the vehicle body 11 per unit time. The yaw angle sensor 56 is, for example, an IMU (Inertial Measurement Unit). Alternatively, the yaw angle sensor 56 may be a position sensor such as a GPS (Global Positioning System). Alternatively, the yaw angle sensor 56 may be another sensor such as an azimuth sensor or a yaw rate sensor. The yaw angle sensor 56 outputs a signal indicating the actual yaw angular velocity of the vehicle body 11 to the controller 51. Alternatively, the yaw angle sensor 56 may output a signal indicating the actual yaw angle of the vehicle body 11 to the controller 51, and the controller 51 may calculate the actual yaw angular velocity from the change in the actual yaw angle.

The first speed sensor 57 and the second speed sensor 58 are rotation sensors. The first speed sensor 57 detects the actual rotation speed of the left driving wheel 16. The first speed sensor 57 outputs a signal indicating the rotation speed of the left driving wheel 16 to the controller 51. The second speed sensor 58 detects the actual rotation speed of the right driving wheel 17. The second speed sensor 58 outputs a signal indicating the rotation speed of the right driving wheel 17 to the controller 51.

As described above, the controller 51 controls the steering mechanism 36 in response to the operation of the steering operation member 54. As a result, the vehicle body 11 turns in response to the operation of the steering operation member 54. In detail, the controller 51 acquires the operation amount (hereinafter referred to as the steering operation amount) and operation direction of the steering operation member 54. The controller 51 controls the capacity of the hydraulic pump 44 in response to the steering operation amount. As a result, the magnitude of the speed increase of the left driving wheel 16 or the right driving wheel 17 is controlled.

The controller 51 controls the left link mechanism 39 and the right link mechanism 43 according to the operating direction of the steering operation member 54 to increase the speed of one of the left driving wheel 16 and the right driving wheel 17. For example, when the operating direction of the steering operation member 54 is a left turn, the hydraulic motor 45 increases the speed of the right driving wheel 17 via the right link mechanism 43. As a result, the rotation speed of the right driving wheel 17 becomes faster than the rotation speed of the left driving wheel 16, and the vehicle body 11 turns to the left due to the rotation speed difference. When the operating direction of the steering operation member 54 is a right turn, the hydraulic motor 45 increases the speed of the left driving wheel 16 via the left link mechanism 39. As a result, the rotation speed of the left driving wheel 16 becomes faster than the rotation speed of the right driving wheel 17, and the vehicle body 11 turns to the right due to the rotation speed difference.

As described above, when the operator turns the vehicle body 11 by operating the steering operation member 54, the vehicle body 11 may not be able to turn and the outer track may slip violently. In the control system 3 of the work machine 1 according to this embodiment, if the vehicle body 11 falls into a slip state while turning, the controller 51 executes slip control to quickly recover from the slip state. The process of the slip control will be described below.

Figure 4 is a block diagram showing the slip control process. As shown in Figure 4, in step S101, the controller 51 determines a first turning command C1 based on the operation of the operator. The controller 51 determines the first turning command C1 according to the steering operation amount described above. The first turning command C1 indicates the magnitude of the speed increase of the left track 18 or the right track 19 according to the steering operation amount.

In detail, the first turning command C1 is indicated by a command value to the hydraulic pump 44. For example, the controller 51 stores turning command data that defines the relationship between the steering operation amount and the first turning command C1. The controller 51 determines the first turning command C1 from the steering operation amount by referring to the turning command data.

Ｖ１は、左履帯１８と右履帯１９とのうち、旋回の内側に位置する方の履帯（以下、内側履帯と呼ぶ）の動作速度（以下、内側速度と呼ぶ）である。Ｖ２は、左履帯１８と右履帯１９とのうち、旋回の外側に位置する方の履帯（以下、外側履帯と呼ぶ）の動作速度（以下、外側速度と呼ぶ）である。車体１１が左方へ旋回する場合には、図２に示すように、内側速度Ｖ１は左履帯１８の動作速度であり、外側速度Ｖ２は右履帯１９の動作速度である。逆に、車体１１が右方へ旋回する場合には、内側速度Ｖ１は右履帯１９の動作速度であり、外側速度Ｖ２は左履帯１８の動作速度である。 In step S102, the controller 51 acquires a theoretical yaw angular velocity ωt. The theoretical yaw angular velocity ωt is the yaw angular velocity of the vehicle body 11 during turning, which is calculated in accordance with the control of the drive unit 32. In detail, the theoretical yaw angular velocity ωt is the yaw angular velocity of the vehicle body 11 calculated from the operating speed of the left crawler 18 and the operating speed of the right crawler 19. The theoretical yaw angular velocity ωt is expressed by the following formula (1).

V1 is the operating speed (hereinafter referred to as the inner speed) of the left track 18 or the right track 19, which is located on the inner side of the turn (hereinafter referred to as the inner track). V2 is the operating speed (hereinafter referred to as the outer speed) of the left track 18 or the right track 19, which is located on the outer side of the turn (hereinafter referred to as the outer track). When the vehicle body 11 turns to the left, as shown in FIG. 2, the inner speed V1 is the operating speed of the left track 18, and the outer speed V2 is the operating speed of the right track 19. Conversely, when the vehicle body 11 turns to the right, the inner speed V1 is the operating speed of the right track 19, and the outer speed V2 is the operating speed of the left track 18.

Ｂは、ゲージ幅である。図２に示すように、ゲージ幅Ｂは、左履帯１８と右履帯１９との中心間距離である。ゲージ幅は、作業機械１の機種に固有の値であり、コントローラ５１に記憶されている。式（１）と式（２）とから、理論ヨー角速度ωｔは、以下の式（３）で表される。コントローラ５１は、式（３）により、内側速度Ｖ１と外側速度Ｖ２とに基づいて、理論ヨー角速度ωｔを算出する。

ステップＳ１０３では、コントローラ５１は、実ヨー角速度ωｒを取得する。実ヨー角速度ωｒは、車体１１の実際のヨー角速度である。コントローラ５１は、ヨー角センサ５６からの信号により、現在の実ヨー角速度ωｒを取得する。 The controller 51 calculates the motion speed of the left crawler belt 18 based on the rotational speed of the left driving wheel 16 and the reduction ratio of the drive unit 32. The controller 51 calculates the motion speed of the right crawler belt 19 based on the rotational speed of the right driving wheel 17 and the reduction ratio of the drive unit 32. In equation (1), R is the turning radius. The turning radius R is expressed by the following equation (2).

B is the gauge width. As shown in Fig. 2, the gauge width B is the center-to-center distance between the left crawler track 18 and the right crawler track 19. The gauge width is a value specific to the model of the work machine 1, and is stored in the controller 51. From equations (1) and (2), the theoretical yaw angular velocity ωt is expressed by the following equation (3). The controller 51 calculates the theoretical yaw angular velocity ωt based on the inside speed V1 and the outside speed V2 using equation (3).

In step S103, the controller 51 acquires the actual yaw angular velocity ωr. The actual yaw angular velocity ωr is the actual yaw angular velocity of the vehicle body 11. The controller 51 acquires the current actual yaw angular velocity ωr based on a signal from the yaw angle sensor 56.

ステップＳ１０５では、コントローラ５１は、目標スリップ率Ｓｔを取得する。目標スリップ率Ｓｔは、０より大きい所定の値である。目標スリップ率Ｓｔは、コントローラ５１に記憶された固定値であってもよい。目標スリップ率Ｓｔは、例えば、車体１１が旋回の困難なスリップ状態ではなく通常状態であると、オペレータが感じる程度の値に設定される。ただし、目標スリップ率Ｓｔは、可変であってもよい。 In step S104, the controller 51 calculates an actual slip ratio Sr. The actual slip ratio Sr indicates the magnitude of slip of the vehicle body 11. The controller 51 calculates the actual slip ratio Sr of the turning vehicle body 11 based on the theoretical yaw angular velocity ωt and the actual yaw angular velocity ωr. The controller 51 calculates the actual slip ratio Sr of the vehicle body 11 by the following equation (4).

In step S105, the controller 51 acquires a target slip ratio St. The target slip ratio St is a predetermined value greater than 0. The target slip ratio St may be a fixed value stored in the controller 51. For example, the target slip ratio St is set to a value that makes the operator feel that the vehicle body 11 is in a normal state, not in a slip state that makes it difficult to turn. However, the target slip ratio St may be variable.

ステップＳ１０７では、コントローラ５１は、最終旋回指令Ｃ３を決定する。コントローラ５１は、オペレータの操作による第１旋回指令Ｃ１に、スリップ制御による第２旋回指令Ｃ２を加えることで、最終旋回指令Ｃ３を決定する。コントローラ５１は。最終旋回指令Ｃ３により、油圧ポンプ４４を制御する。 In step S106, the controller 51 determines a second turning command C2 by slip control. The controller 51 determines the second turning command C2 by slip control so that the actual slip ratio Sr becomes the target slip ratio St. The controller 51 determines the second turning command C2 by slip control by P (proportional) control, for example, by the following equation (5). In the following equation (5), Kp is a P gain.

In step S107, the controller 51 determines a final turning command C3. The controller 51 determines the final turning command C3 by adding the second turning command C2 by the slip control to the first turning command C1 by the operation of the operator. The controller 51 controls the hydraulic pump 44 based on the final turning command C3.

For example, if the actual slip ratio Sr is greater than the target slip ratio St, the second turning command C2 due to slip control will be a negative value. Therefore, the controller 51 reduces the final turning command C3 to be less than the first turning command C1 due to the operator's operation. This reduces the operating speed of the outer track during turning. As a result, the actual slip ratio Sr is reduced, allowing the vehicle body 11 to escape from the slip state.

When the vehicle body 11 escapes from the slip state, the actual slip ratio Sr decreases and approaches the target slip ratio St. When the actual slip ratio Sr decreases and the difference between the actual slip ratio Sr and the target slip ratio St becomes small, the controller 51 decreases the value of the turning command C2. Then, the controller 51 increases the final turning command C3 so that it approaches the first turning command C1 input by the operator. This increases the operating speed of the outer track during turning. As a result, work efficiency improves.

The control system 3 of the work machine 1 according to the present embodiment described above controls the rotational speed of at least one of the left drive wheel 16 and the right drive wheel 17 so that the actual slip ratio Sr becomes the target slip ratio St. This allows the work machine 1 to quickly escape from a slip state.

The target slip ratio St is a predetermined value greater than 0. This prevents the actual slip ratio Sr from decreasing excessively, thereby improving work efficiency.

The theoretical yaw angular velocity ωt of the vehicle body 11 is calculated based on the actual rotational speed of the left drive wheel 16 and the actual rotational speed of the right drive wheel 17. Therefore, the theoretical yaw angular velocity ωt of the vehicle body 11 is calculated with high accuracy.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the invention.

The work machine 1 is not limited to a bulldozer, but may be other machines such as a shovel, wheel loader, or tractor. The travelling device 12 is not limited to tracks, but may include tires. The work machine 1 may be a vehicle that can be remotely controlled. In that case, the operating members 52-54 and the input device 55 may be disposed outside the work machine 1. The cab 14 may be omitted from the work machine 1.

The configuration of the drive device 32 is not limited to that of the above embodiment and may be modified. For example, the clutches 37, 41 may be omitted from the work machine 1 of the above embodiment. Alternatively, FIG. 5 is a schematic diagram showing the configuration of the work machine 1 according to a first modified example. As shown in FIG. 5, the steering mechanism 36 and link mechanisms 39, 43 may be omitted from the drive device 32. The controller 51 may control the clutches 37, 41 and the brakes 38, 42 to generate a rotational speed difference between the left drive wheel 16 and the right drive wheel 17, thereby turning the vehicle body 11.

Figure 6 is a schematic diagram showing the configuration of the work machine 1 according to the second modified example. As shown in Figure 6, the drive device 32 may include a first travel pump 61, a second travel pump 62, a first travel motor 63, and a second travel motor 64. The first travel pump 61 and the second travel pump 62 are hydraulic pumps. The first travel pump 61 and the second travel pump 62 are driven by the drive source 31. The first travel motor 63 and the second travel motor 64 are hydraulic motors. The first travel motor 63 is driven by hydraulic oil from the first travel pump 61. The first travel motor 63 is connected to the left drive wheel 16 and rotates the left drive wheel 16. The second travel motor 64 is driven by hydraulic oil from the second travel pump 62. The second travel motor 64 is connected to the right drive wheel 17 and rotates the right drive wheel 17. The controller 51 may control the capacity of the first traveling pump 61 and the capacity of the second traveling pump 62 to cause a rotational speed difference between the left driving wheel 16 and the right driving wheel 17, thereby turning the vehicle body 11.

The slip control is not limited to that of the above embodiment, and may be modified. For example, the actual slip ratio Sr is an example of an actual slip value. Instead of the actual slip ratio Sr, the actual slip amount may be used as the actual slip value. The actual slip amount may be indicated by the difference between the theoretical yaw angular velocity ωt and the actual yaw angular velocity ωr. Similarly, the target slip ratio St is an example of a target slip value. Instead of the target slip ratio St, the target slip amount may be used as the target slip value.

The method for determining the target slip ratio St is not limited to that of the above embodiment and may be modified. For example, the target slip ratio St may be set by the input device 55. The operator may be able to input the value of the target slip ratio St by the input device 55. Alternatively, the target slip ratio St may be set according to a selection of a level indicating the strength of the slip control, such as "strong," "medium," or "weak."

Alternatively, FIG. 7 is a schematic diagram showing the configuration of a work machine 1 according to a third modified example. As shown in FIG. 7, the work machine 1 may be equipped with a soil sensor 65. The soil sensor 65 detects the hardness of the ground on which the work machine 1 is placed. The controller 51 may obtain the hardness of the ground on which the work machine 1 is placed, and determine the predetermined target slip ratio St based on the hardness of the ground. For example, the controller 51 may increase the predetermined target slip ratio St as the hardness of the ground becomes softer.

Alternatively, the controller 51 may obtain the ground hardness based on the work site information. The work site information indicates the relationship between the position in the work site where the work machine 1 is placed and the ground hardness. The controller 51 may accept the selection of an arbitrary position in the work site by the input device 55. For example, the input device 55 may include a monitor, and a map of the work site may be displayed on the monitor. The operator may select an arbitrary position from the map displayed on the monitor. The controller 51 may obtain the ground hardness corresponding to the selected work site position by referring to the work site information.

The determination of the predetermined target slip ratio St may be performed not only by the controller 51 of the work machine 1, but also by a computer external to the work machine 1. The controller 51 may obtain the target slip ratio St from an external computer. For example, FIG. 8 is a schematic diagram showing the configuration of a work machine 1 according to a fourth modified example.

As shown in FIG. 8, the work machine 1 may be equipped with a communication device 66. The communication device 66 is, for example, a module for wireless communication, and communicates with a computer external to the work machine 1. The communication device 66 may use a mobile communication network. Alternatively, the communication device 66 may use another network such as a LAN (Local Area Network) or the Internet. The work machine 1 may transmit the acquired ground hardness to an external server 67 via the communication device 66. The server 67 may calculate a target slip ratio St according to the ground hardness and transmit it to the controller 51 of the work machine 1 via the communication device 66.

In the above-described embodiment or modified example, the drive source 31 is not limited to an internal combustion engine, and may include an electric motor. The electric motor may be driven by electric power generated by the driving force of the internal combustion engine. For example, as in a fifth modified example shown in FIG. 9, the work machine 1 may be provided with a generator 71 and a motor 73 instead of the transmission 34. The generator 71 may generate electric power by the driving force from the drive source 31. The motor 73 may be connected to the generator 71 via an inverter 72. The motor 73 may be driven by the electric power generated by the generator 71, thereby driving the drive wheels 16, 17. Similarly, in the other modified examples described above, the work machine 1 may be provided with a generator and a motor instead of the transmission 34. Alternatively, the work machine 1 may be provided with a generator and a motor instead of the travel pumps 61, 62 and the travel motors 63, 64.

This disclosure allows the work machine to quickly escape from a slipping state.

1: Work machine 11: Body 16: Left driving wheel 17: Right driving wheel 18: Left track 19: Right track 31: Driving source 32: Driving device 51: Controller 55: Input device 56: Yaw angle sensor 57: First speed sensor 58: Second speed sensor

Claims (20)

A system for controlling a work machine including a vehicle body, a left drive wheel rotatably supported on the vehicle body, a right drive wheel rotatably supported on the vehicle body, a drive source mounted on the vehicle body, and a drive device that rotates the left drive wheel and the right drive wheel by drive force from the drive source,
a yaw angle sensor for detecting an actual yaw angular velocity of the vehicle body;
a controller that controls the drive device to turn the vehicle body using a rotational speed difference between the left drive wheel and the right drive wheel;
Equipped with
The controller:
Calculating a theoretical yaw angular velocity of the vehicle body in response to control of the drive device;
Obtaining the actual yaw angular velocity;
Calculating an actual slip value indicating a magnitude of slip of the vehicle body during turning based on the theoretical yaw angular velocity and the actual yaw angular velocity;
a rotation speed of at least one of the left driving wheel and the right driving wheel is controlled so that the actual slip value becomes a predetermined target slip value greater than 0;
system. The controller:
When the actual slip value is greater than the target slip value, a rotation speed of one of the left driving wheel and the right driving wheel, which is located on the outer side during turning, is reduced.
The system of claim 1 . The controller:
increasing a rotation speed of one of the left driving wheel and the right driving wheel, which is located on the outer side during turning, in response to a decrease in the actual slip value;
The system of claim 2. a first speed sensor for detecting a rotation speed of the left driving wheel;
a second speed sensor for detecting a rotation speed of the right driving wheel;
Further equipped with
The controller calculates the theoretical yaw angular velocity based on a rotation speed of the left driving wheel and a rotation speed of the right driving wheel.
The system of claim 1 . A left crawler belt wound around the left driving wheel;
A right crawler belt wound around the right driving wheel;
Further equipped with
The controller:
Calculating a motion speed of the left crawler based on a rotational speed of the left drive wheel;
Calculating a motion speed of the right crawler based on a rotational speed of the right drive wheel;
Calculating the theoretical yaw angular velocity based on the motion speed of the left crawler and the motion speed of the right crawler;
The system of claim 4. The predetermined target slip value is a fixed value.
The system of claim 1 . Further comprising an input device operable by an operator;
The predetermined target slip value is set by the input device.
The system of claim 1 . The controller:
Obtaining the hardness of the ground on which the work machine is placed;
determining the predetermined target slip value based on the hardness of the ground;
The system of claim 1 . The controller:
acquiring work site information indicative of a relationship between a position within a work site where the work machine is located and ground hardness;
Accepting a selection of any location within the work site;
Refer to the work site information to obtain the ground hardness corresponding to the selected position within the work site;
determining the predetermined target slip value based on the hardness of the ground;
The system of claim 1 . A method for controlling a work machine including a vehicle body, a left drive wheel rotatably supported on the vehicle body, a right drive wheel rotatably supported on the vehicle body, a drive source mounted on the vehicle body, and a drive device that rotates the left drive wheel and the right drive wheel by drive force from the drive source, comprising:
controlling the drive device to turn the vehicle body using a rotational speed difference between the left drive wheel and the right drive wheel;
Calculating a theoretical yaw angular velocity of the vehicle body in response to control of the drive device;
Obtaining an actual yaw angular velocity of the vehicle body;
Calculating an actual slip value indicating a magnitude of slip of the vehicle body during turning based on the theoretical yaw angular velocity and the actual yaw angular velocity;
controlling a rotation speed of at least one of the left driving wheel and the right driving wheel so that the actual slip value becomes a predetermined target slip value greater than 0;
A method for providing the above. When the actual slip value is greater than the target slip value, a rotational speed of one of the left driving wheel and the right driving wheel, which is located on an outer side during turning, is reduced;
The method of claim 10 further comprising: increasing a rotational speed of one of the left driving wheel and the right driving wheel, which is located on an outer side during turning, in response to a decrease in the actual slip value;
The method of claim 11 further comprising: Obtaining a rotational speed of the left driving wheel;
Obtaining a rotational speed of the right drive wheel;
Calculating the theoretical yaw angular velocity based on a rotation speed of the left driving wheel and a rotation speed of the right driving wheel;
The method of claim 10 further comprising: The work machine includes:
A left crawler belt wound around the left driving wheel;
A right crawler belt wound around the right driving wheel;
Further equipped with
Calculating a motion speed of the left crawler based on a rotational speed of the left drive wheel;
Calculating a motion speed of the right crawler based on a rotational speed of the right drive wheel;
Calculating the theoretical yaw angular velocity based on a motion speed of the left crawler and a motion speed of the right crawler;
The method of claim 13 further comprising: The predetermined target slip value is a fixed value.
The method of claim 10. The predetermined target slip value is set by an input device operable by an operator.
The method of claim 10. Obtaining a hardness of the ground on which the work machine is placed;
determining the predetermined target slip value based on the hardness of the ground;
The method of claim 10 further comprising: acquiring work site information indicative of a relationship between a location within a work site where the work machine is located and ground hardness;
accepting a selection of a location within the work site;
Referencing the work site information to obtain the ground hardness corresponding to a selected position within the work site;
determining the predetermined target slip value based on the hardness of the ground;
The method of claim 10 further comprising: A method for controlling a work machine including a vehicle body, a left drive wheel rotatably supported on the vehicle body, a right drive wheel rotatably supported on the vehicle body, a drive source mounted on the vehicle body, and a drive device that rotates the left drive wheel and the right drive wheel by drive force from the drive source, comprising:
controlling the drive device to turn the vehicle body using a rotational speed difference between the left drive wheel and the right drive wheel;
Obtaining a rotational speed of the left driving wheel;
Obtaining a rotational speed of the right drive wheel;
Calculating a theoretical yaw angular velocity of the vehicle body based on a rotation speed of the left driving wheel and a rotation speed of the right driving wheel;
Obtaining an actual yaw angular velocity of the vehicle body;
Calculating an actual slip value of the vehicle body during turning based on the theoretical yaw angular velocity and the actual yaw angular velocity;
When the actual slip value is greater than a predetermined target slip value, controlling a rotation speed of at least one of the left driving wheel and the right driving wheel so as to reduce the actual slip value;
A method for providing the above. The work machine includes:
A left crawler belt wound around the left driving wheel;
A right crawler belt wound around the right driving wheel;
Further equipped with
Calculating a motion speed of the left crawler based on a rotational speed of the left drive wheel;
Calculating a motion speed of the right crawler based on a rotational speed of the right drive wheel;
Calculating the theoretical yaw angular velocity based on a motion speed of the left crawler and a motion speed of the right crawler;
20. The method of claim 19 further comprising:

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