Control system for work machine and control method for work machine

Abstract

This control system for a work machine comprises a vehicle body (1), steering cylinders (2a, 2b), a steering lever (55), an IMU (62), and a controller (26). The steering cylinders (2a, 2b) are attached to the vehicle body (1). The steering lever (55) outputs movement command signals (C1) for causing the steering cylinders (2a, 2b) to move. The IMU (62) detects information pertaining to the vibration of the vehicle body (1). On the basis of the information pertaining to the vibration of the vehicle body (1), the controller (26) restricts the movement of the steering cylinders (2a, 2b) with respect to the movement command signal (C1).

Description

Work machine control system and work machine control method

[0001] The present invention relates to a control system and a control method for a work machine.

[0002] 2. Description of the Related Art Work machines such as wheel loaders are used at construction sites or mining excavation sites. At such sites, excavation work and the like is carried out, and unevenness may be formed in the ground.

[0003] For example, Patent Document 1 discloses that when a transport vehicle detours around a section of a mining site that has large unevenness, the unevenness of the detoured road surface is estimated and road surface maintenance is carried out effectively.

[0004] JP 2019-44538 A

[0005] However, if a detour is not possible, the vehicle will have to travel on an uneven road surface, and the vibration of the vehicle body may cause an unintended input to the steering operation device, which may affect steering operation.

[0006] An object of the present disclosure is to provide a control system and a control method for a work machine that enables the vehicle body to travel stably.

[0007] A work machine control system according to a first aspect of the present disclosure includes a vehicle body, a steering cylinder, an operation device, a sensor, and a controller. The steering cylinder is attached to the vehicle body. The operation device outputs an operation command to operate the steering cylinder. The sensor detects information related to vibrations of the vehicle body. The controller limits operation of the steering cylinder in response to the operation command based on the information related to vibrations of the vehicle body.

[0008] A work machine control method according to a second aspect of the present disclosure includes a vibration detection step, an output step, and a control step. The vibration detection step detects information related to vibrations of the body of the work machine. The output step outputs an operation command to operate a steering cylinder attached to the body. The control step limits operation of the steering cylinder in response to the operation command based on the information related to vibrations of the body. (Effects of the Invention)

[0009] According to the present disclosure, it is possible to provide a control system and a control method for a work machine that allows the vehicle body to travel stably.

[0010] Fig. 1 is a side view of a wheel loader according to an embodiment of the present disclosure. Fig. 2 is a block diagram showing a system configuration of a wheel loader according to an embodiment of the present disclosure. Fig. 3 is a diagram for explaining detection by an IMU. Fig. 4 is a block diagram showing a configuration related to steering operation of a wheel loader according to an embodiment of the present disclosure. Fig. 4 is a diagram showing an example of an acceleration vibration waveform. Fig. 5 is a diagram for explaining determination of a state transition of the wheel loader. Fig. 5 is a diagram showing an operation command signal output from a steering lever. Fig. 6 is a diagram showing the relationship between a steering lever angle and an output value to an EPC valve. Fig. 7 is a diagram showing a valve drive command signal to an EPC valve. Fig. 7 is a flow diagram showing operation of a wheel loader according to an embodiment of the present disclosure.

[0011] (Outline of Wheel Loader) A control system for a work machine will be described with reference to the drawings, using a wheel loader as an example of a work machine. In the following description, "front," "rear," "right," "left," "up," and "down" refer to directions relative to the state when looking forward from the driver's seat. "Vehicle width direction" is synonymous with "left-right direction."

[0012] FIG. 1 is a side view showing the overall configuration of a wheel loader 10 according to this embodiment.

[0013] The wheel loader 10 includes a vehicle body 1 and steering cylinders 2a, 2b (see FIG. 4 ). The vehicle body 1 includes a vehicle frame 3, a pair of front tires 4, a pair of rear tires 5, a work implement 6, a cab 7, an engine compartment 8, and a counterweight 9.

[0014] The body frame 3 is of a so-called articulated type and includes a front frame 11 (an example of a first frame), a rear frame 12 (an example of a second frame), and a connecting shaft 13. The front frame 11 is disposed in front of the rear frame 12. The connecting shaft 13 is provided in the center in the vehicle width direction and rotatably connects the front frame 11 and the rear frame 12 to each other. A pair of front tires 4 are attached to the left and right of the front frame 11. Furthermore, a pair of rear tires 5 are attached to the left and right of the rear frame 12.

[0015] The pair of steering cylinders 2a, 2b are attached to the vehicle body 1. The pair of steering cylinders 2a, 2b are hydraulically driven. The pair of steering cylinders 2a, 2b are arranged side by side on the left and right sides in the vehicle width direction, sandwiching a connecting shaft 13 therebetween. One end of each of the steering cylinders 2a, 2b is attached to the front frame 11, and the other end is attached to the rear frame 12. The angle of the front frame 11 relative to the rear frame 12 is adjusted by the extension and contraction of the steering cylinders 2a, 2b.

[0016] The work implement 6 is attached to the vehicle body frame 3. The work implement 6 is attached to the front side of the front frame 11. The work implement 6 is used for various tasks (for example, loading and unloading earth and sand). The work implement 6 is driven by hydraulic oil from a hydraulic pump (not shown). The work implement 6 has a boom 14, a bucket 15, a lift cylinder 16, a bucket cylinder 17, and a bell crank 18. The boom 14 is attached to the front frame 11. The bucket 15 is attached to the tip of the boom 14.

[0017] The lift cylinder 16 and the bucket cylinder 17 are hydraulic cylinders. One end of the lift cylinder 16 is attached to the front frame 11, and the other end of the lift cylinder 16 is attached to the boom 14. The boom 14 moves up and down as the lift cylinder 16 extends and retracts. One end of the bucket cylinder 17 is attached to the front frame 11, and the other end of the bucket cylinder 17 is attached to the bucket 15 via a bell crank 18. The bucket 15 moves up and down as the bucket cylinder 17 extends and retracts.

[0018] The cab 7 is mounted on the rear frame 12. Inside the cab 7, there are arranged a steering lever 55 for changing the traveling direction of the wheel loader 10, a work implement control lever 56 for operating the work implement 6, various pedals, various switches, a display device, etc. (see FIG. 2).

[0019] The engine room 8 is disposed on the rear frame 12 behind the cab 7. An engine 31, which will be described later, is housed in the engine room 8. The counterweight 9 is disposed behind the engine room 8. The counterweight 9 is disposed on the rear end of the rear frame 12.

[0020] (System Configuration of Wheel Loader) FIG. 2 is a block diagram that schematically shows the system configuration of the wheel loader 10. As shown in FIG.

[0021] The wheel loader 10 includes a travel unit 21 , a braking unit 22 , an operation unit 23 , a detection unit 24 , a steering unit 25 , and a controller 26 .

[0022] (Running Unit 21 ) The running unit 21 includes an engine 31 , an HST (Hydro Static Transmission) 32 , a transfer case 33 , an axle 34 , front tires 4 , and rear tires 5 .

[0023] The engine 31 is, for example, a diesel engine. The HST 32 includes a pump 32a, a motor 32b, and a hydraulic circuit 32c.

[0024] The pump 32a is a swash plate type variable displacement pump. The angle of the swash plate of the pump 32a can be changed by a solenoid 32d. The pump 32a is driven by the engine 31 to discharge hydraulic oil. The hydraulic oil discharged from the pump 32a is sent to the motor 32b through a hydraulic circuit 32c. The motor 32b is a swash plate type pump. The angle of the swash plate of the motor 32b can be changed by a solenoid 32e.

[0025] The hydraulic circuit 32c is connected to the pump 32a and the motor 32b. The hydraulic circuit 32c includes a first drive circuit 32c1 and a second drive circuit 32c2. Hydraulic oil is supplied from the pump 32a to the motor 32b via the first drive circuit 32c1, thereby driving the motor 32b in one direction (e.g., forward movement). Hydraulic oil is supplied from the pump 32a to the motor 32b via the second drive circuit 32c2, thereby driving the motor 32b in the other direction (e.g., reverse movement). The direction of hydraulic oil discharge to the first drive circuit 32c1 or the second drive circuit 32c2 can be changed by the solenoid 32d.

[0026] The motor 32b is connected to the transfer 33 via a drive shaft 35. A vehicle speed sensor 36 is provided on the drive shaft 35. The vehicle speed sensor 36 detects the speed of the vehicle body 1 (hereinafter referred to as vehicle speed). The vehicle speed sensor 36 detects the vehicle speed based on the rotation speed of the drive shaft 35. The vehicle speed sensor 36 transmits a detection signal indicating the vehicle speed to the controller 26.

[0027] The transfer 33 distributes the output from the engine 31 to a front axle 34 and a rear axle 34. A pair of front tires 4 are connected to the front axle 34. The pair of front tires 4 rotate by the output distributed to the front axle 34. A pair of rear tires 5 are connected to the rear axle 34. The pair of rear tires 5 rotate by the output distributed to the rear axle 34.

[0028] (Brake Unit 22) The brake unit 22 has a brake valve 41, a service brake 42, and a parking brake 43. The brake valve 41 is, for example, an EPC (Electric Proportional Control Valve). The amount of hydraulic oil sent to the service brake 42 is adjusted according to the opening degree of the brake valve 41. The opening degree of the brake valve 41 is controlled by a controller 26. The controller 26 controls the opening degree of the brake valve 41 according to the operation amount of a brake pedal 54 (described later). Note that a PPC (Pressure Proportional Control Valve) may be used as the brake valve 41.

[0029] The service brakes 42 are provided on the front axle 34 and the rear axle 34. The service brakes 42 are hydraulic brakes. The braking force of the service brakes 42 increases as the opening of the brake valves 41 increases.

[0030] The parking brake 43 is provided on the transfer 33. As the parking brake 43, for example, a wet multi-stage brake that can be switched between a braking state and a non-braking state, a disc brake, or the like can be used.

[0031] (Operation Unit 23 ) The operation unit 23 has an accelerator pedal 51 , an FNR lever 52 , a parking switch 53 , a brake pedal 54 , a steering lever 55 (an example of an operation device), and a work equipment operation lever 56 .

[0032] The accelerator pedal 51 is provided inside the cab 7. The accelerator pedal 51 transmits an operation signal indicating the accelerator pedal operation amount to the controller 26. The controller 26 controls the throttle opening of the engine 31 based on the received operation signal.

[0033] The FNR lever 52 is provided inside the cab 7. The FNR lever 52 can be switched to any one of a forward position, a neutral position, and a reverse position. The FNR lever 52 transmits an operation signal indicating the position of the FNR lever 52 to the controller 26. The controller 26 controls the solenoid 32d based on the received operation signal to switch between forward, neutral, and reverse.

[0034] The parking switch 53 is provided in the cab 7. The parking switch 53 can be switched between an ON position and an OFF position. The parking switch 53 transmits an operation signal indicating the position of the parking switch 53 to the controller 26. The controller 26 places the parking brake 43 in an applied or non-applied state based on the received operation signal.

[0035] The brake pedal 54 is provided inside the cab 7. The brake pedal 54 transmits an operation signal indicating the pedal operation amount and the pedal operation speed to the controller 26. The controller 26 controls the opening degree of the brake valve 41 based on the received operation signal.

[0036] The steering lever 55 is provided inside the cab 7. The steering lever 55 transmits an operation command signal indicating the steering direction and steering amount to the controller 26. The controller 26 extends and retracts the steering cylinders 2a, 2b arranged on the body frame 3 based on the received operation command signal.

[0037] The work implement operation lever 56 is provided inside the cab 7. The work implement operation lever 56 transmits an operation signal indicating the amount of operation of the lift cylinder 16 and the bucket cylinder 17 to the controller 26. Although not shown, the controller 26 controls a pump that supplies hydraulic oil to the lift cylinder 16 and the bucket cylinder 17, a lift cylinder control valve that adjusts the amount of hydraulic oil supplied to the lift cylinder 16, and a bucket cylinder control valve that adjusts the amount of hydraulic oil supplied to the bucket cylinder 17, based on the received operation signal. As a result, hydraulic oil is supplied to the lift cylinder 16 and the bucket cylinder 17, and the work implement 6 is driven.

[0038] (Detection Unit 24) The detection unit 24 has a frame angle sensor 61 and an IMU 62. The frame angle sensor 61 detects the angle of the front frame 11 relative to the rear frame 12 and transmits a frame angle signal indicating the detected value to the controller 26. The frame angle sensor 61 is, for example, a potentiometer. The frame angle sensor 61 is disposed on the connecting shaft portion 13. The controller 26 extends and retracts the steering cylinders 2a, 2b while referring to the frame angle signal so that the steering angle corresponds to the steering angle indicated by the operation command signal received from the steering lever 55.

[0039] The IMU (Inertial Measurement Unit) 62 is an inertial measurement unit. As shown in FIG. 1 , the IMU 62 is disposed on the rear frame 12. The IMU 62 has an acceleration sensor and a gyro sensor. The IMU 62 measures acceleration and angular velocity along the X-axis, Y-axis, and Z-axis shown in FIG. 3 . For example, the X-axis points forward of the vehicle body 1, the Y-axis points to the right of the vehicle body 1, and the Z-axis points downward of the vehicle body 1. The IMU 62 outputs detection signals including information on the acceleration and angular velocity along the X-axis, Y-axis, and Z-axis to the controller 26.

[0040] (Steering Unit 25) The steering unit 25 adjusts the flow rate of oil supplied to the steering cylinders 2a, 2b. FIG. 4 is a block diagram showing the configuration related to steering control. In FIG. 4, the basic system configuration related to the traveling unit 21 is omitted from the controller 26. The steering unit 25 has a steering valve 71, a main pump 72, an EPC valve 73 (an example of an adjustment valve), and a pilot pump 74.

[0041] The steering valve 71 is a flow rate control valve that adjusts the flow rate of oil supplied to the steering cylinders 2 a, 2 b in accordance with the input pilot pressure. A spool valve, for example, is used as the steering valve 71. The main pump 72 supplies the steering valve 71 with hydraulic oil that operates the steering cylinders 2 a, 2 b.

[0042] The steering valve 71 has a valve body (not shown, e.g., a spool) that can be moved to a left steering position, a neutral position, and a right steering position. When the valve body of the steering valve 71 is located in the right steering position, as shown in Figure 4, the steering cylinder 2b contracts and the steering cylinder 2a expands, increasing the frame angle and causing the vehicle body 1 to turn right.

[0043] When the valve body of the steering valve 71 is positioned in the left steering position, the steering cylinder 2a contracts and the steering cylinder 2b expands, reducing the frame angle and turning left the vehicle body 1. When the valve body of the steering valve 71 is positioned in the neutral position, the frame angle does not change.

[0044] The EPC valve 73 is a flow rate regulating valve that adjusts the flow rate or pressure of pilot hydraulic pressure supplied to the steering valve 71 in response to a command from the controller 26. The pilot pump 74 supplies hydraulic oil for operating the steering valve 71 to the EPC valve 73. The EPC valve 73 is, for example, a spool valve, and is controlled in accordance with a valve drive command signal from the controller 26.

[0045] The EPC valve 73 has a valve body (not shown, for example, a spool) that can be moved to a left pilot position, a neutral position, and a right pilot position. When the valve body of the EPC valve 73 is located in the left pilot position, the steering valve 71 is in the left steering position. When the valve body of the EPC valve 73 is located in the right pilot position, the steering valve 71 is in the right steering position. When the valve body of the EPC valve 73 is located in the neutral position, the steering valve 71 is in the neutral position.

[0046] The pilot pressure or pilot flow rate from the EPC valve 73 is controlled in response to a valve drive command signal from the controller 26, thereby controlling the steering valve 71 and thereby the steering cylinders 2 a, 2 b. The valve drive command signal is a command value for the flow rate of hydraulic oil supplied from the steering valve 71 to the steering cylinders 2 a, 2 b.

[0047] (Controller 26) The controller 26 includes a processor and a storage device. The processor is, for example, a CPU (Central Processing Unit). Alternatively, the processor may be a processor different from the CPU. The processor executes processing for controlling the wheel loader 10 in accordance with a program stored in the storage device. The storage device includes non-volatile memory such as ROM (Read Only Memory) and volatile memory such as RAM (Random Access Memory). The storage device may include an auxiliary storage device such as a hard disk or an SSD (Solid State Drive). The storage device is an example of a non-transitory computer-readable recording medium.

[0048] The controller 26 has a calculation unit 81, a vibration determination unit 82, a correction unit 83, and a valve drive command creation unit 84. The functions of the calculation unit 81, the vibration determination unit 82, the correction unit 83, and the valve drive command creation unit 84 are realized by the processor executing a program stored in the storage device.

[0049] The calculation unit 81 calculates the change in acceleration over time from the detection signal input from the IMU 62. For example, the calculation unit 81 calculates the axial acceleration by combining the acceleration in the X-axis direction, the acceleration in the Y-axis direction, and the acceleration in the Z-axis direction. Note that the calculation unit 81 is not limited to the combined value, and the absolute value of the acceleration in any one of the three axes may be used, for example, the acceleration in the Z-axis direction. Furthermore, the calculation unit 81 may use the combined acceleration or the change in acceleration in any one of the axes over time. Furthermore, although the calculation unit 81 acquires acceleration from the IMU 62, if an angular velocity is acquired from the IMU 62, the calculation unit 81 may calculate the acceleration by differentiating the angular velocity.

[0050] The vibration determination unit 82 determines whether or not vibration is occurring in the vehicle body 1 based on the calculated axial acceleration.

[0051] Fig. 5 is a diagram showing the change over time in the axial acceleration calculated by the calculation unit 81. A vibration detection acceleration Gt is set in Fig. 5. The time when the axial acceleration reaches the vibration detection acceleration Gt is designated as T1, and the time after time T1 when the axial acceleration reaches the vibration detection acceleration Gt is designated as T2. Furthermore, the time after time T2 when the axial acceleration reaches the vibration detection acceleration Gt is designated as T3, the time after time T3 when the axial acceleration reaches the vibration detection acceleration Gt is designated as time T4, and the times when the axial acceleration reaches the vibration detection acceleration Gt are designated as times T5, T6, T7, T8, T9, T10, T11, and T12, respectively.

[0052] 6 is a state transition diagram showing the vibration state of the wheel loader 10. The vibration determination unit 82 determines that the wheel loader 10 has transitioned from the no-vibration state M1 to the vibrating state M2 when condition (1) is satisfied.

[0053] The condition (1) is satisfied when the first time ≦ the first vibration determination time and the second time ≦ the second vibration determination time are satisfied. The first vibration determination time and the second vibration determination time are set to times that allow vibrations caused by unevenness in the ground to be detected.

[0054] The vibration determination unit 82 first sets the time T1 when the axial acceleration becomes the vibration detection acceleration Gt as the reference time, sets the time between time T1 and time T2 as the first time t1, and sets the time between time T1 and time T3 as the second time t2.

[0055] The vibration determination unit 82 determines that vibration is occurring in the vehicle body 1 when the first time t1≦the first vibration determination time and the second time t2<the second vibration determination time are satisfied. Furthermore, the vibration determination unit 82 determines that vibration is not occurring in the vehicle body 1 when the first time t1≦the first vibration determination time and the second time t2≦the second vibration determination time are not satisfied. Thus, by setting condition (1), it is possible to detect vibrations that have an acceleration equal to or greater than a predetermined threshold and a short period, which are generated in the steering lever 55 due to unevenness in the ground. The vibration detection acceleration Gt, the first vibration determination time, and the second vibration determination time are set to values ​​that enable detection of vibrations caused by unevenness in the ground, and are stored in the controller 26.

[0056] When time T1 is set as the reference time, if the first time t1≦first vibration determination time and the second time t2≦second vibration determination time are not satisfied, the vibration determination unit 82 sets the first time and the second time as the reference time, that is, time T2, when the axial acceleration becomes the vibration detected acceleration Gt after time T1. Specifically, the vibration determination unit 82 sets the time between time T2 and time T3 as the first time, and the time between time T2 and time T4 as the second time. Note that in FIG. 5 , in order to distinguish between the first time and the second time when time T1 is set as the reference time, the first time between time T2 and time T3 is indicated as t1′, and the second time between time T2 and time T4 is indicated as t2′.

[0057] Then, the vibration determination unit 82 determines whether the first time t1'≦the first vibration determination time and the second time t2'≦the second vibration determination time are satisfied.

[0058] In this way, the vibration determination unit 82 first determines whether condition (1) is met using time T1, when the axial acceleration reaches the vibration detection acceleration Gt, as the reference time, and then shifts the reference time to time T2, when the axial acceleration decreases to the vibration detection acceleration Gt, sets the first time t1' and the second time t2', and determines whether condition (1) is met. If condition (1) is not met using time T2 as the reference time, the vibration determination unit 82 shifts the reference time sequentially to time T3 and time T4, in that order, to set the first time and the second time, and then performs determination.

[0059] The vibration determination unit 82 determines whether condition (1) is satisfied, using the time when the axial acceleration becomes the vibration detection acceleration Gt as the reference time, the time from the reference time to the next time when the axial acceleration becomes the vibration detection acceleration Gt as the first time, and the time from the reference time to the next time when the axial acceleration becomes the vibration detection acceleration Gt after the first time has elapsed as the second time.

[0060] Furthermore, if the vibration determination unit 82 determines that the vehicle body 1 is in the vibrating state M2 when the condition (1) is satisfied and then determines that the vehicle body 1 is in the vibrating state M2 and the condition (2) is satisfied, the vibration determination unit 82 determines that the state of the vehicle body 1 has transitioned from the vibrating state M2 to the non-vibrating state M1 and that the vibration has converged. The case where the condition (2) is satisfied is when the state where the condition (1) is not satisfied continues for a predetermined threshold time or more. This predetermined threshold time is a vibration convergence determination time for determining the convergence of the vibration.

[0061] The case where the state where condition (1) is not satisfied continues for a predetermined threshold time or longer is, for example, when condition (1) is satisfied using time T1 as the reference time and it is determined that the vibrating state M2 is being established, and then the first condition is not satisfied even when the first and second times are set using times T7, T8, and T9 as the reference times, respectively, and the predetermined threshold time has elapsed. The predetermined threshold time is stored in the controller 26.

[0062] In addition, a case where condition (1) is not satisfied also includes a case where the first time or the second time cannot be set. For example, if time T11 is the reference time, the axial acceleration reaches the vibration detection acceleration Gt at time T12, so the time from time T11 to time T12 can be set as the first time. However, the axial acceleration after time T12 does not reach the vibration detection acceleration Gt, so the second time cannot be set. If the time during which the second time cannot be set continues for a predetermined threshold time or longer, the vibration determination unit 82 determines that condition (2) is satisfied. Also, if time T12 is the reference time, the axial acceleration after time T12 does not reach the vibration detection acceleration Gt, so the first time cannot be set. If the time during which the first time cannot be set continues for a predetermined threshold time or longer, the vibration determination unit 82 determines that condition (2) is satisfied.

[0063] The correction unit 83 corrects the operation command signal received from the steering lever 55 when the vibration determination unit 82 determines that the vehicle is in the vibrating state M2.

[0064] The upper part of Fig. 7 shows the operation command signal C1 transmitted from the steering lever 55 to the controller 26. In Fig. 7, the horizontal axis represents time (s) and the vertical axis represents the steering lever angle. 0 (deg) represents the input value when the steering lever 55 is in the neutral position. A positive value of the steering angle represents, for example, the angle when the steering wheel is operated to the right from the neutral position, and a negative value represents the angle when the steering wheel is operated to the left from the neutral position. It can be seen that a high-frequency signal is generated in the operation command signal C1 due to vibrations occurring in the vehicle body 1 from time T20.

[0065] When the vibration determination unit 82 determines that vibration has been occurring in the vehicle body 1 since time T20, the correction unit 83 corrects the operation command signal C1 from time T20. The lower part of Figure 7 shows the corrected operation command signal C2 corrected by the correction unit 83.

[0066] The correction unit 83 filters the motion command signal C1 using a low-pass filter that eliminates high frequencies and passes low-frequency signals. This allows the motion command signal C1 to be smoothed, as shown in the corrected motion command signal C2. Note that filtering is not limited to using a low-pass filter, and any method that can smooth the motion command signal is sufficient.

[0067] The valve drive command generation unit 84 generates a valve drive command signal C3 to be output to the EPC valve 73 from the operation command signal C1 or the corrected operation command signal C2. FIG. 8 is a diagram showing an example of the relationship between the steering lever angle and the output value to the EPC valve 73. In the example shown in FIG. 8, the output value to the EPC valve 73 changes linearly with the steering lever angle. As shown in FIG. 8, when the steering lever 55 is in the neutral position, a current value A0 is output to the EPC valve 73. When the steering lever 55 is operated rightward from the neutral position and the steering lever angle increases, the current value output to the EPC valve 73 is set to increase from A0. Furthermore, when the steering lever 55 is operated leftward from the neutral position and the steering lever angle decreases, the current value output to the EPC valve 73 is set to decrease from A0.

[0068] The controller 26 stores the relationship of the output value to the EPC valve 73 versus the steering lever angle shown in FIG. 8. The valve drive command creation unit 84 creates a valve drive command signal C3 from the operation command signal C1 or the corrected operation command signal C2 based on this relationship. If the vibration state M2 is determined, the valve drive command creation unit 84 creates the valve drive command signal C3 from the corrected operation command signal C2. On the other hand, if the no-vibration state M1 is determined, no correction has been made by the correction unit 83, so the valve drive command creation unit 84 creates the valve drive command signal C3 from the operation command signal C1.

[0069] The upper part of Fig. 9 shows a valve drive command signal C3 generated from the corrected operation command signal C2. The vertical axis of Fig. 9 represents current value, and the horizontal axis represents time. The valve drive command signal C3 represents changes in the output value to the EPC valve 73 over time. The valve drive command signal C3 generated by the valve drive command generation unit 84 is sent to the EPC valve 73. The spool of the EPC valve 73 moves based on the valve drive command signal C3, and the pilot pressure supplied to the steering valve 71 is controlled. By controlling the pilot pressure, the hydraulic oil supplied from the steering valve 71 to the steering cylinders 2a, 2b is controlled, changing the angle of the front frame 11 relative to the rear frame 12, thereby performing a steering operation.

[0070] 9 is a diagram showing a valve drive command signal C103 obtained when it is assumed that a valve drive command signal is generated from the operation command signal C1 without any correction being made to the operation command signal C1, which includes a signal due to vibrations occurring in the vehicle body 1. If no correction is made, the operation command signal includes a high-frequency signal due to vibrations occurring in the vehicle body 1, and therefore the valve drive command signal C103 also includes a high-frequency signal due to vibrations, and the amount of hydraulic oil supplied to the steering cylinders 2a, 2b becomes unstable.

[0071] In this way, the wheel loader 10 of this embodiment can reduce the sensitivity of the steering lever 55 by smoothing the operation command signal C1, thereby stabilizing steering operation.

[0072] (Control Operation) Next, a description will be given of the control operation of the wheel loader 10 of this embodiment. Fig. 10 is a flow chart showing the control operation of the wheel loader 10 of this embodiment.

[0073] First, in step S10 (an example of a vibration information detection step), the controller 26 acquires a detection signal from the IMU 23 .

[0074] Next, in step S11 , the calculation unit 81 of the controller 26 calculates the axial acceleration by combining the acceleration in the X-axis direction, the acceleration in the Y-axis direction, and the acceleration in the Z-axis direction contained in the detection signal from the IMU 23 .

[0075] Next, in step S12, the vibration determination unit 82 of the controller 26 determines whether the axial acceleration satisfies condition (1). If the first time ≦ the first vibration determination time and the second time ≦ the second vibration determination time are satisfied, the vibration determination unit 82 determines that condition (1) is satisfied and that vibration is occurring in the vehicle body 1.

[0076] If it is determined in step S12 that vibration is occurring in the vehicle body 1, and the operator operates the steering lever 55, the controller 26 receives an operation command signal C1 in step S13.

[0077] Next, in step S14 (an example of a control step), the corrector 83 of the controller 26 performs correction to smooth the motion command signal C1, and generates a corrected motion command signal C2.

[0078] Next, in step S15 (an example of an output step), the valve drive command generator 84 generates a valve drive command signal C3 based on the corrected operation command signal C2 and outputs the signal C3 to the EPC valve 73 .

[0079] Next, in step S16, the vibration determination unit 82 determines whether or not condition (2) is satisfied. If the state in which condition (1) is not satisfied continues for the vibration convergence determination time or more, the vibration determination unit 82 determines that condition (2) is satisfied and the vibration of the vehicle body 1 has converged. On the other hand, if the state in which condition (1) is not satisfied does not continue for the vibration convergence determination time or more, the vibration determination unit 82 determines that condition (2) is not satisfied and the vibration of the vehicle body 1 has not converged.

[0080] If it is determined in step S16 that the condition (2) is satisfied, the control proceeds to step S17. When the controller 26 receives the operation command signal C1 in step S17, in step S18, the correction unit 83 does not correct the operation command signal C1, and the valve drive command creation unit 84 creates a valve drive command signal C3 from the operation command signal C1 and outputs the valve drive command signal C3 to the EPC valve 73, and the control ends.

[0081] If the vibration determination unit 82 determines in step S12 that the condition (1) is not satisfied, the control proceeds to step S17. If the vibration determination unit 82 determines in step S16 that the condition (2) is not satisfied, the control returns to step S13.

[0082] (Features, etc.) In the work machine control system of this embodiment, the controller 26 limits the operation of the steering cylinders 2a, 2b in response to the operation command signal C1 output from the steering lever 55, based on the acceleration or angular velocity detected by the IMU 62. As a result, when vibrations are generated in the vehicle body 1 due to unevenness of the ground or the like, the behavior of the steering cylinders 2a, 2b is prevented from becoming unstable due to the vibrations transmitted to the steering lever 55, and the vehicle body 1 can travel stably.

[0083] In the work machine control system of this embodiment, the operation command signal C1 output from the steering lever 55 is corrected and the operation of the steering cylinders 2a, 2b is restricted based on the detection value of the IMU 62. By correcting the operation command signal C1 in this way, it is possible to reduce signal components generated from the operation command signal C1 due to vibration of the vehicle body 1, thereby stabilizing the behavior of the steering cylinders 2a, 2b and stabilizing the traveling of the vehicle body 1.

[0084] In the work machine control system of this embodiment, the controller 26 corrects the operation command signal C1 when it determines that vibration is occurring in the vehicle body 1 based on the detection value of the IMU 62. As a result, when vibration is occurring in the vehicle body 1, the corrected operation command signal C2 is used to control the steering cylinders 2a, 2b, and when vibration is not occurring, the operation command signal C1 is used to control the steering cylinders 2a, 2b.

[0085] In the work machine control system of this embodiment, the controller 26 smooths and corrects the operation command signal C1 by filtering, thereby reducing the sensitivity of the steering lever 55 and stabilizing the steering operation.

[0086] In the control system for a work machine of this embodiment, when the controller 26 determines that vibration is occurring in the vehicle body 1, it outputs a valve drive command signal C3 to the EPC valve 73 in accordance with the corrected operation command signal C2, thereby operating the steering cylinders 2a, 2b. In this way, by outputting the valve drive command signal C3 to the EPC valve 73, which adjusts the pilot pressure for operating the steering valve 71, in accordance with the corrected operation command signal C2, it is possible to stabilize the behavior of the steering cylinders 2a, 2b and to stabilize the traveling of the vehicle body 1.

[0087] (Other Embodiments) 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 gist of the invention.

[0088] (A) In the above embodiment, it was described that the steering lever 55 vibrates due to vibrations generated in the vehicle body 1 inside the wheel loader 10, but the present invention is not limited to this. For example, the present invention is also effective in a construction machine control system in which a remote-operated driver's seat is provided separately from the wheel loader 10 and a mechanism is provided to vibrate the remote-operated driver's seat in response to vibrations of the actual vehicle body 1. In other words, if the steering lever provided in the remote-operated driver's seat vibrates due to vibrations of the remote-operated driver's seat, by correcting the operation command signal from the steering lever to the wheel loader 10, it is possible to stabilize the behavior of the steering cylinders 2a, 2b of the remotely operated wheel loader 10 and to stabilize the travel of the wheel loader 10.

[0089] (B) In the above embodiment, a determination as to whether the vehicle is traveling is not made. However, after it is determined that the vehicle is traveling, a determination as to whether condition (1) is satisfied may be made. The determination as to whether the vehicle is traveling can be made based on a detection signal from the vehicle speed sensor 36 shown in FIG. 2, but is not limited to this. For example, the determination as to whether the vehicle is traveling may be made based on an operation signal input from the accelerator pedal 51 or an operation signal from the FNR lever 52.

[0090] (C) In the above embodiment, as shown in Figure 8, the output value to the EPC valve 73 with respect to the steering lever angle is linear, but this is not limited to this. For example, when the absolute value of the steering angle becomes equal to or greater than a predetermined threshold, the slope of the output value to the EPC valve 73 with respect to the steering lever angle may decrease or become constant. Alternatively, the output value to the EPC valve 73 with respect to the steering angle may change exponentially.

[0091] (D) In ​​the above embodiment, steering is performed using the steering lever 55, but this is not limited to a lever and may also be a handle.

[0092] (E) In the above embodiment, a valve drive command signal is sent to the EPC valve 73 that supplies pilot pressure to operate the steering valve 71. However, the EPC valve 73 may not be provided, and the valve drive command signal may be sent to the steering valve 71 to directly drive the steering valve 71.

[0093] (F) In the above embodiment, the wheel loader 10 is provided with an IMU 62, but this is not limited to an IMU. For example, if vibration is determined using vertical acceleration, an acceleration sensor may be provided instead of an IMU.

[0094] (G) In the above embodiment, the IMU 62 is provided on the rear frame 12, but this is not limiting and the IMU 62 may be provided, for example, inside the cab 7. The IMU 62 may also be provided on the front frame 11, but it is preferable to provide the IMU 62 in a position that is subject to the vibrations of the vehicle body 1.

[0095] (H) In the above embodiment, the vibration determination unit 82 determines whether vibration is occurring in the vehicle body 1 by determining whether condition (1) is satisfied, but this is not limited to this. For example, it may be determined that vibration is occurring when the interval between the times when the axial acceleration increases and becomes equal to or greater than the vibration detection acceleration Gt is equal to or less than a predetermined value. In this case, referring to FIG. 5 , it may be determined that vibration is occurring when the interval between time T1 and time T3 or the interval between time T3 and time T5 is equal to or less than a predetermined value.

[0096] (I) In the above embodiment, vibration is judged using two times, the first time and the second time, but vibration may also be judged using three or more times, not just two times.

[0097] (J) In the above embodiment, acceleration is used to determine vibration, but this is not limiting. As shown in FIG. 3 , the IMU 62 calculates the pitch angle pθ, yaw angle yθ, and roll angle rθ from the accelerations and angular velocities of the X-axis, Y-axis, and Z-axis. This pitch angle pθ may be used to determine vibration. For example, the calculation unit 81 calculates the frequency and amplitude of vibration of the pitch angle pθ. The vibration determination unit 82 may determine that vibration is occurring when the calculated amplitude of the pitch angle pθ is greater than a predetermined threshold and the frequency of the pitch angle pθ is greater than a predetermined threshold.

[0098] (K) In the above embodiment, the wheel loader 10 is equipped with an HST 32 as a transmission, but this is not limited to this. For example, an HMT (Hydro Mechanical Transmission), a T / C (torque converter), or the like can be used as the transmission.

[0099] The work machine and work machine control method disclosed herein have the effect of enabling the vehicle body to travel stably, and are useful in, for example, wheel loaders.

[0100] 1: Vehicle body 2a: Steering cylinder 2b: Steering cylinder 26: Controller 55: Steering lever 62: IMU

Claims

1. A control system for a work machine comprising: a vehicle body; a steering cylinder attached to the vehicle body; an operating device that outputs an operation command signal to operate the steering cylinder; a sensor that detects information related to vibration of the vehicle body; and a controller that limits the operation of the steering cylinder in response to the operation command signal based on the information related to the vibration of the vehicle body.

2. A control system for a work machine as set forth in claim 1, wherein the sensor detects at least one of the acceleration and angular velocity of the vehicle body as information relating to the vibration, and the controller corrects the operation command signal based on the detection value of the sensor and limits the operation of the steering cylinder.

3. A control system for a work machine as set forth in claim 2, wherein the controller corrects the operation command signal when it determines that vibration is occurring in the vehicle body based on the detection value of the sensor.

4. A control system for a work machine as described in claim 3, wherein the controller sets a first time as the time from a reference time when the detection value of the sensor reaches a predetermined threshold to the time when the detection value next reaches the predetermined threshold, and sets a second time as the time from the reference time to the time when the detection value next reaches the predetermined threshold after the first time has elapsed, and determines whether or not vibration is occurring in the vehicle body based on the first time and the second time.

5. A work machine control system as set forth in claim 4, wherein the controller releases the restriction on the operation of the steering cylinder when it determines that no vibration is occurring in the vehicle body based on the first time period and the second time period.

6. A work machine control system as described in claim 1, wherein the vehicle body has: a first frame; and a second frame disposed rearward of the first frame and rotatably connected to the first frame; and the steering cylinder is disposed across the first frame and the second frame.

7. A work machine control system as claimed in claim 3, further comprising an adjusting valve for adjusting the hydraulic oil supplied to the steering cylinder, wherein when the controller determines that vibration is occurring in the vehicle body, it outputs a valve drive command signal to the adjusting valve in accordance with the corrected operation command signal, thereby operating the steering cylinder by driving the adjusting valve.

8. A control method for a work machine, comprising: a vibration information detection step of detecting information relating to vibration of a body of the work machine; an output step of outputting an operation command signal for operating a steering cylinder attached to the body; and a control step of limiting the operation of the steering cylinder in response to the operation command signal based on the information relating to the vibration of the body.

Images