GB2553504A

GB2553504A - A machine comprising a body and an implement movable relative to the body

Info

Publication number: GB2553504A
Application number: GB1614569.0A
Authority: GB
Inventors: Curran Patrick
Original assignee: Caterpillar Inc
Current assignee: Caterpillar Inc
Priority date: 2016-08-26
Filing date: 2016-08-26
Publication date: 2018-03-14
Also published as: CN107780449A; CN107780449B; GB201614569D0

Abstract

A method for controlling a machine, such as a wheel loader, with a body and a movable arm. Hydraulic actuators 150 move the arm and a hydraulic accumulator 310 dampens its movement. An accumulator valve 320 fluidly couples the hydraulic accumulator 310 to the hydraulic actuators 150 and a sensor determines arm position. The machine has an undamped mode of operation where the accumulator valve 320 is in a closed position, a damped mode of operation where the accumulator valve 320 is at least partially open and a transition mode between the undamped and damped mode. To control the machine, a sensor signal is used as a reference value, the accumulator valve 320 is opened so hydraulic fluid flows from the hydraulic actuators 150 to the hydraulic accumulator 310 to dampen arm movement, after a delay, a new sensor value is obtained and used as a damped value, and the hydraulic actuators 150 moves the arm until its position matches the reference value.

Description

(54) Title of the Invention: A machine comprising a body and an implement movable relative to the body Abstract Title: Ride control system with machine arm damping (57) A method for controlling a machine, such as a wheel loader, with a body and a movable arm. Hydraulic actuators 150 move the arm and a hydraulic accumulator 310 dampens its movement. An accumulator valve 320 fluidly couples the hydraulic accumulator 310 to the hydraulic actuators 150 and a sensor determines arm position. The machine has an undamped mode of operation where the accumulator valve 320 is in a closed position, a damped mode of operation where the accumulator valve 320 is at least partially open and a transition mode between the undamped and damped mode. To control the machine, a sensor signal is used as a reference value, the accumulator valve 320 is opened so hydraulic fluid flows from the hydraulic actuators 150 to the hydraulic accumulator 310 to dampen arm movement, after a delay, a new sensor value is obtained and used as a damped value, and the hydraulic actuators 150 moves the arm until its position matches the reference value.

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A machine comprising a body and an implement movable relative to the body

Technical Field

The disclosure relates to the field of machines of a kind comprising a body and an implement movable relative to the body.

Background

It is known that when a machine having one or more arms that support an implement, such as a wheel loader, is being driven with a loaded implement, it is possible that the machine may be subjected to shocks due to the weight of the loaded implement reacting to the machine encountering bumps or other obstacles in its pathway. In order to help reduce or eliminate the effects of shocks, it is known to use one or more hydraulic accumulators selectively connected to the hydraulic lift cylinder actuator. The hydraulic accumulator, when connected to the loaded end of the hydraulic lift cylinder actuators, serves to absorb pressure fluctuations in the actuators thus offsetting the changing forces that would otherwise be acting on the various components of the machine. It is these changing forces acting on the machine that produce shocks. In order to maintain a pre-charge in the accumulator equal to the pressure in the loaded end of the actuator, it is known to connect the accumulator to the loaded end of the lift cylinder actuator. In this way, the load supporting end of the cylinder is in free communication with the accumulator in order to absorb the changing forces. An implementation of this concept may be known as a ride control system.

One consequence of such a ride control system may be that the implement arms change position when the ride control system is first engaged. For example, if the implement is heavily loaded then the implement arms may drop when the hydraulic accumulator is first connected to the hydraulic lift cylinder actuator. Conversely, if the arms are not heavily loaded (e.g. where an implement is absent altogether) then the implement arms may rise when the hydraulic accumulator is first connected to the hydraulic lift cylinder actuator.

Furthermore, it may be that in a ride control mode, an operator is prevented from altering the height of the implement arms.

Summary of the disclosure

Against this background, there is provided a method of controlling a machine, the machine comprising:

a body; an arm movable relative to the body; a hydraulic actuator configured to actuate movement of the arm relative to the body; a hydraulic accumulator for damping movement of the arm relative to the body; an accumulator valve configured to selectively fluidly couple the hydraulic accumulator to the hydraulic actuator; and a sensor configured to provide a sensor signal indicative of arm position relative to the body;

the machine having an undamped mode of operation in which the accumulator valve is in a closed position; a damped mode of operation in which the accumulator valve is in an at least partly open position; and a transition mode that occurs on transition between the undamped mode and the damped mode;

the method comprising the following steps, in order:

on commencement of the transition mode, obtaining a present value of the sensor signal as a reference value;

at least partly opening the accumulator valve such that hydraulic fluid flows from the hydraulic actuator to the hydraulic accumulator to provide damping of movement of the arm relative to the body;

after a delay, obtaining a present value of the sensor signal for use as a damped value; and actuating the hydraulic actuator to move the arm relative to the body until arm position matches the reference value.

In a further aspect, the disclosure provides a machine comprising:

a body; an arm movable relative to the body; a hydraulic actuator configured to actuate movement of the arm relative to the body; a hydraulic accumulator for damping movement of the arm relative to the body; an accumulator valve configured to selectively fluidly couple the hydraulic accumulator to the hydraulic actuator; and a sensor configured to provide a sensor signal indicative of arm position relative to the body; and a controller;

-3the machine having an undamped mode of operation in which the accumulator valve is closed; a damped mode of operation in which the accumulator valve is at least partly open; and a transition mode that occurs on transition between the undamped mode and the damped mode;

the controller configured such that:

on commencement of the transition mode, the controller obtains a present value of the sensor signal as a reference value;

the controller outputs a signal that at least partly opens the accumulator valve such that hydraulic fluid flows from the hydraulic actuator to the hydraulic accumulator to provide damping of movement of the arm relative to the body;

after a delay, the controller obtains a present value of the sensor signal for use as a damped value; and the controller actuates the hydraulic actuator to move the arm relative to the body until arm position matches the reference value.

Brief description of the drawings

Figure 1 is a highly schematic representation of a machine having an implement movable relative to the body configured to be controlled in accordance with the disclosure;

Figure 2 is a schematic representation of a hydraulic fluid circuit in accordance with the disclosure; and

Figure 3 is a flow chart that shows a flow of control operations in accordance with the disclosure.

Detailed description

Referring to Figure 1, there is shown a machine 100 known as a backhoe loader. The backhoe loader may comprise a body 110 mounted on wheels 180 and means (such as an internal combustion engine) for providing rotational kinetic energy to the wheels 180 for effecting ground propulsion of the machine 100. The machine 100 may further comprise a

-4loader assembly 120 and a backhoe assembly 130. The loader assembly may be configured to carry an implement 140.

While it is common for the backhoe assembly 130 to be operated only while the machine is stationary, it is common for the loader assembly 120 to be used to carry loads a distance using the ground propulsion of the machine 100.

The present disclosure may be particularly applicable to the loader assembly 120. The backhoe assembly 130 may be configured as is known in the art.

The loader assembly 120 comprises a first arm 170 and a second arm (not visible in Figure 1) on an opposite side of the machine 100 from the first arm 170. The arms 170 are each pivotally attached at a first end 171 to the body 110 at an arm pivot 160. An implement 140 (shown as forks in the Figure 1 example) is pivotally attached to second end 172 of each of the arms 170, the second end 172 being opposite the first end 171. The first and second arms 170 may be pivoted in tandem via the arm pivots 160. Pivoting the arms 170 via the arm pivots 160 may cause the implement 140 to raise or lower relative to the body 110.

Pivoting of each arm 170 relative to the body 110 may be effected by a hydraulic actuator 150, one for each arm. (Note that one of the wheels 180 is cut away in the Figure 1 representation in order that a front end of the hydraulic actuator is not obscured by the wheel 180.) Each hydraulic actuator 150 may comprise a cylinder 151 and a rod 152 slidable in a telescopic arrangement from a first position in which much of the rod 152 is contained within the cylinder 151 into a second position in which much of the rod 152 protrudes from the cylinder 151. A proximal end 153 of the cylinder 151 may be pivotally connected to the body 110 whilst a distal end of the rod 154 (opposite the proximal end 153 of the cylinder 151) may be pivotally connected to a part of the arm 170 that is distant from the arm pivot 160. In this way, movement of the rod 152 in a direction into the cylinder 151 may cause the arms 170 to pivot in a downward direction relative to the body 110 while movement of the rod 152 in a direction out of the cylinder 151 may cause the arms 170 to pivot in an upward direction relative to the body 110.

One or more sensors (not illustrated) may be provided on the body 110 to sense the position of the arms 170. The sensors may be loader arm angle sensors located adjacent each of the arm pivots 160. Since both arms 170 may be expected to be at the same

-5height, where two sensors are provided (one for each arm) that may be expected to provide the same angular output value.

Other linkages, pivots and hydraulic actuators may be provided on the loader assembly 120, for example in order to control an angle of the implement 140 relative to the arms 170. An example of such an arrangement is shown in Figure 1.

When the machine 100 is stationary it may be desirable to have no damping of the hydraulic actuators 150 such that movement of the arms 170 may be controlled with greater precision. By contrast, when the machine 100 is being driven, especially at higher speeds and over uneven surfaces, it may be desirable to dampen the hydraulic actuators 150 in order that forces resulting from movement over uneven ground will not be fully transferred to the implement 140, which may otherwise be particularly problematic if the implement is in a raised position.

Turning to Figure 2, there is shown a hydraulic circuit 200 in accordance with the present disclosure. The pair of hydraulic actuators 150, one for each of the two arms, is shown. As described previously, each hydraulic actuator 150 comprises a cylinder 151 and a rod 152. The rod 152 may be movable axially relative to the cylinder 151. A rod head 155 may be located at the end of the rod 152 that is permanently located within the cylinder 151. Hydraulic fluid may be supplied towards a head end 156 of the cylinder 151 in order to effect movement of the rod 152 out of the cylinder 151. Conversely, hydraulic fluid may be supplied towards a rod end 157 of the cylinder 151 in order to effect movement of the rod 152 into the cylinder 151.

The hydraulic circuit 200 may comprise a hydraulic fluid tank 220, a hydraulic fluid pump 230, and an implement control valve 210 for controlling flow and direction of hydraulic fluid between the hydraulic fluid tank 220 via the hydraulic fluid pump 230 to either the head end 156 or the rod end 157 of the cylinder 151.

The implement control valve 210 may comprise a first position 211 in which direction of flow may be such that hydraulic fluid from the hydraulic fluid tank 220 via the hydraulic fluid pump 230 is supplied to the head ends 156 of the cylinders 151 such that the rods 152 move out of the cylinders 151 so as to effect raising of the arms 170 relative to the body 110 and therefore raising of the implement 140.

-6The implement control valve 210 may comprise a second position 212 (as shown in Figure 2) in which flow of fluid is prevented in either direction.

The implement control valve 210 may comprise a third position 213 in which direction of flow may be such that hydraulic fluid from the hydraulic fluid tank 220 via the hydraulic fluid pump 230 is supplied to the rod ends 157 of the cylinders 151 such that the rods 152 move into the cylinders 151 so as to effect lowering of the arms 170 relative to the body 110 and therefore lowering of the implement 140.

The hydraulic circuit 200 may further comprise a damping arrangement 300 comprising a hydraulic accumulator 310. The damping arrangement 300 may further comprise a first proportional valve 320 configured to control flow between the head end 156 of the cylinders 151 and the hydraulic accumulator 310. In a first position of the first proportional valve 320 (as shown in Figure 2), flow may be largely restricted or entirely prevented. When entirely prevented, the hydraulic accumulator 310 is isolated from the hydraulic actuators 150 such that no damping is provided. In a second position of the valve, fluid may flow freely between the head end 156 of the cylinders 151 and the hydraulic accumulator 310.

Working in tandem with the first proportional valve 320 is a second proportional valve 330 configured to control flow between the rod end 157 of the cylinders 151 and the hydraulic fluid tank 220.

The first and second proportional valves 320, 330 may be configured such that: when the one is closed the other is closed; when one is fully open the other is fully open; and when neither closed nor fully open, an extent to which one is open matches an extent to which the other is open.

A controller may be provided. The controller may receive user inputs (for example, requesting movement of the arms 170) and in response the controller may supply output signals to one or more of the hydraulic fluid pump 230, the implement control valve 210, the first proportional valve 320 and the second proportional valve 330 so as to execute user input requests. In addition, the controller may receive other signals (such as sensor values) and supply output signals to the hydraulic fluid pump 230, the implement control valve 210, the first proportional valve 320 and the second proportional valve 330.

-7In accordance with the disclosure, control of the damping arrangement 300 of the hydraulic circuit 200 by the controller may be as follows.

In an undamped mode, the first and second proportional valves 320, 330 may be fully closed such that the hydraulic accumulator 310 is isolated from the hydraulic actuators 150 and no damping is provided.

The undamped mode may be particularly appropriate when the machine is stationary such that there are no forces resulting from ground propulsion over uneven ground and where precision of implement position is desirable, such as when accessing a pallet with a pair of forks 140.

Movement of the implement 140 up and down is effected by movement of the hydraulic actuators 150 which move when hydraulic fluid flows into the head end 156 (for raising the implement 140) or the rod end 157 (for lowering the implement 140).

Flow of hydraulic fluid is controlled by the hydraulic fluid pump 230 in combination with the implement control valve 210. When the implement control valve 210 is in the first position 211 and the hydraulic fluid pump 230 is in operation, hydraulic fluid may flow into the head end 156. When the implement control valve 210 is in the second position 212, whether or not the hydraulic fluid pump 230 is in operation, no hydraulic fluid will flow into either end of the hydraulic actuator 150. When the implement control valve 210 is in the third position 213 and the hydraulic fluid pump 230 is in operation, hydraulic fluid may flow into the rod end 157.

In a damped mode (also known as a ride control mode), the first and second proportional valves 320, 330 may be at least partly open such that the hydraulic accumulator 310 is in fluid communication with the head end 156 of the cylinders 151. Fluid in the hydraulic accumulator 310 may act against a biasing means which may act to absorb sudden forces that may be applied to the machine.

The damped mode may be particularly appropriate when the machine is moving, especially when at speed and/or on uneven ground, where damping of forces resulting from

-8movement of the machine may be desirable so as to reduce the effect of those forces on the implement 140 and machine 100.

The damped mode may be implemented upon an instruction from a user; or when machine speed exceeds a predetermined threshold or in the event of any other appropriate trigger.

When the damped mode is first implemented, flow of hydraulic fluid into or out of the hydraulic accumulator 310 may result in a change in pressure at the head end 156 of the cylinders 151 which may in turn result in an undesirable movement of the rod 152 leading to undesired movement of the implement 140 relative to where 156.

In order to compensate for an undesired change in position of the implement 140, there may be provided a transition mode that it adopted between the undamped mode and the damped mode.

In the transition mode it may be that user control of the implement valve is limited or restricted or prevented. Alternatively, it may be that in the event that user inputs are received that request movement of the arms then the transition mode is terminated and the undamped mode is reinitiated.

In the transition mode, the loader arm position may be noted by the controller noting the angular output value from the loader arm angle sensors. This value may be stored by the controller as a reference value.

Subsequently, the first and second proportional valves 320, 330 are opened to some degree in order to allow fluid pressure at the head end 156 of the cylinders 151 to be released into the hydraulic accumulator 310 (or, as the case may be, to allow fluid pressure in the hydraulic accumulator 310 to be released into the into the head end 156 of the cylinders 151).

This stage may result in movement of the rods 152 causing a change in height of the loader arms 170.

-9The loader arm position may be continuously noted by the controller receiving the angular output value from the loader arm angle sensors. This value may be compared by the controller to the reference value.

In response, the controller may implement instructions to the implement control valve 210 and the hydraulic fluid pump 230 to provide fluid from the hydraulic fluid tank 220 into the head end of the hydraulic actuator 150 or the rod end 157 of the cylinder 151, as the case may be, in order to move the loader arms 170 back to the reference position. The faster the controller is in detecting and compensating for a change, the less change will be apparent. Return of the arms to the reference position may be confirmed when the sensor outputs the same as the previously measured reference value.

The control of the implement control valve 210 and the hydraulic fluid pump 230 during the transition period may be configured in a continuous feedback loop such that the compensatory fluid flow is provided rapidly in response to changes in loader arm position meaning that significant movement of the implement is unnoticeable to an operator.

At the conclusion of the transition period, the accumulator pressure and the pressure at the head end 156 of the cylinder 151 is balanced such that continuous feedback is no longer required. At this point, the damped mode may be implemented. The transition mode may last for an order of seconds, preferably fewer than 10 seconds, more preferably between 2 and 5 seconds and may be implemented in such a manner such that significant movement of the loader arm is continuously prevented. The first and second proportional valves 320, 330 may then be set to a pre-determined position proportional to the measured pressure at the head end 156 of the cylinder 151.

In the damped mode it may be that user control of the implement valve is limited or restricted or prevented. The controller may automatically terminate the damped mode and initiate the undamped mode in the event that user inputs are received that request movement of the arms.

A simplified control process flow diagram is shown in Figure 3. This represents a technique by which the control of the transition mode in particular may be implemented. The skilled person will appreciate that the control technique is not limited to that illustrated

- 10in Figure 3 and amendments, additions and subtractions to the control technique suggested in Figure 3 fall within the scope of the disclosure.

Once the process starts 505, if ride control is requests 510 then reference arm angle 0_ref is measured 515 using the loader arm angle sensor(s) prior to engaging 520 the hydraulic accumulator 310. The arm angle θ_η is measured 525 and the difference between 0_ref and θ_η is calculated (ΔΘ). If ΔΘ # 0 535 then the implement control valve 210 and hydraulic fluid pump 230 may be implemented 540 to compensate for ΔΘ. The process then repeats back to the step of arm angle θ_η being measured 525. If ΔΘ = 0 for at least minimum period (e.g. 10 second, 5 seconds or 2 seconds) then no further compensation is provided. By contrast, if ΔΘ = 0 for less than a minimum period then the process then repeats back to the step of arm angle θ_η being measured 525.

When implement instructions are received 550, the hydraulic accumulator 310 is disengaged 555. The system loops back to the start for a next ride control request 510.

Industrial applicability

The method, system and apparatus of the present disclosure may be particularly applicable in machines that have both a loading mode and a driving mode, where the requirements as to damping are divergent in each of these modes.

The disclosure provides for improved safety and comfort during a driving mode (in which the damped mode is applicable), whilst not sacrificing any aspect of precision control whilst in the loading mode (in which undamped mode is applicable). Moreover, the transition mode (between the undamped mode and the damped mode) may be used to compensate for undesirable consequences of the switch in mode with little or no knowledge of the operator to the feedback control being implemented in the transition mode.

While the disclosure has focused on the a backhoe loader application as shown in Figure 1 (albeit that the backhoe itself is not central to the disclosure), it will be appreciated by the skilled person that the disclosure is applicable to other machine types including all types of loaders such as tractor loaders, wheel loaders, skid steer loaders, telescopic loaders, track loaders, crawler loaders and multi-terrain loaders.

Claims

CLAIMS:

1. A method of controlling a machine, the machine comprising:

the method comprising the following steps, in order:

2. The method of claim 1 wherein the step of actuating the hydraulic actuator to move the arm relative to the body until arm position matches the reference value concludes when a present accumulator value matches the reference value.

3. The method of claim 1 or claim 2 wherein the body comprises propulsion apparatus configured to facilitate ground propulsion of the body in a propulsion mode of the machine, wherein the method involves implementing the transition mode when the machine is in the propulsion mode.

4. The method of claim 3 wherein the machine comprises a stationary mode in which the propulsion apparatus is disengaged, wherein the method involves implementing the undamped mode when the machine is in the stationary mode.

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5. The method of claim 4 further comprising invoking the transition mode on detecting a transition from stationary mode to propulsion mode.

6. The method of any preceding claim further comprising, in the damped mode, regulating the position of the accumulator valve between the open position and one or more intermediate positions.

7. A machine comprising:

the machine having an undamped mode of operation in which the accumulator valve is closed; a damped mode of operation in which the accumulator valve is at least partly open; and a transition mode that occurs on transition between the undamped mode and the damped mode;

the controller configured such that:

8. The machine of claim 7 wherein the controller is configured to stop actuating the hydraulic actuator to move the arm relative to the body when a present accumulator value matches the reference value.

9. The machine of claim 7 or claim 8 wherein the body comprises propulsion apparatus configured to facilitate ground propulsion of the body in a propulsion mode of the

- 13machine, and wherein the controller is configured to implement the transition mode when the machine is in the propulsion mode.

10. The machine of claim 9 comprising a stationary mode in which the propulsion 5 apparatus is disengaged and wherein the controller is configured to implement the undamped mode when the machine is in the stationary mode.

11. The machine of claim 10 wherein the controller is further configured to invoke the transition mode on detecting a transition from stationary mode to propulsion mode.

12. The machine of any of claims 8 to 11 wherein the controller is further configured in the damped mode to regulate the position of the accumulator valve between the open position and one or more intermediate positions.

Intellectual

Property

Office

Application No: GB1614569.0 Examiner: Mike McKinney