GB2641304A

GB2641304A - Work machine and method for operating at least one hydraulic cylinder of a work machine

Info

Publication number: GB2641304A
Application number: GB2407461.9A
Authority: GB
Inventors: W Provenzano Roger; P Lee Daniel; Lee Gorman Corey; M Ruemelin Christopher
Original assignee: Caterpillar Inc
Current assignee: Caterpillar Inc
Priority date: 2024-05-24
Filing date: 2024-05-24
Publication date: 2025-11-26
Also published as: WO2025244821A1; GB202407461D0

Abstract

A work machine (10 fig.1) has an arm (14 fig.1), tool (15 fig.1) and a hydraulic cylinder 600 having a piston 601 extendable along a full range determined by end stops 608, 610. A control system (50 fig.2) receives sensor data from a sensor system (7 fig.2) indicative of the movement of the piston, such as position, acceleration or pressure data. From the sensor data the control system determines a current velocity of and current load on the piston and controls deceleration of the piston to reduce an impact load, if any, of the piston upon the first or second end stop, possibly by altering a clearance between the piston and the end stops. The impact parameters may include velocity, static force or momentum of the piston whilst default parameters may be loaded into the control system and thresholds may be set depending on tool type or position of the tool relative to the arm but may also be overridden by the operator.

Description

WORK MACHINE AND METHOD FOR OPERATING AT LEAST ONE HYDRAULIC CYLINDER OF A WORK MACHINE

Technical Field

The present disclosure relates to a work machine, and a method for operating at least one hydraulic cylinder of a work machine. In particular, the at least one hydraulic cylinder is operated based upon the determination of whether the piston of the at least one hydraulic cylinder will contact an end stop of the at least one hydraulic cylinder.

Background

Work machines, or vehicles such as excavators or backhoe loaders, typically function and perform work through the extension and retraction of hydraulic cylinders. These hydraulic cylinders are attached either side of a pivot to allow the relative rotation of components of the work machine, such as a boom arm, stick, and/or bucket. Hydraulic cylinders comprise a piston moveable in a range determined by two end stops. The piston of a hydraulic cylinder comprises a piston head and a piston rod. The piston of the hydraulic cylinder moves in response to work machine fluid (which could be hydraulic fluid/hydraulic oil) being pumped into the cylinder on either side of the piston head.

Repeated contact between the piston and end stop(s) can damage the hydraulic cylinder over time, with contact between the piston and end stop occurring at higher loads and/or velocities having a greater impact on the operational life and/or service intervals required for the hydraulic cylinder.

US10648154 discloses a method of controlling hydraulic fluid flow to an implement of a material handling vehicle. It includes coupling a boom arm to a vehicle frame for rotation about the vehicle frame, rotating a boom arm with respect to the vehicle frame with an actuator, coupling an attachment to the boom arm for rotation with respect to the boom arm, sensing a pressure of fluid in the actuator, communicating the sensed pressure to a control system, determining a baseline pressure of the attachment based upon the sensed pressure of the fluid in the actuator, and limiting fluid flow to the actuator with a control valve in response to the sensed pressure of the fluid in the actuator being above the baseline pressure.

Summary

An object of the present disclosure is to reduce wear on and/or avoid damage to the end stops of a hydraulic cylinder of a work machine. A further object of the present disclosure may be to allow the hydraulic cylinder to operate across its full range when necessary. A further object of the present disclosure may be to ensure that operators are made aware of the operation to reduce wear.

The present disclosure provides a work machine and method in accordance with the claims. In particular, the control system controls deceleration of the piston on the basis of the current velocity of and load on a piston of at least one hydraulic cylinder of the work machine, so as to avoid or reduce impact of the piston on the cylinder end stops.

The present disclosure is generally directed towards a work machine comprising: an arm arrangement and a tool mounted to the arm arrangement; at least one hydraulic cylinder comprising a piston, extendable along a full range determined by first and second end stops to actuate the arm arrangement and/or tool; and a sensor system for generating sensor data indicative of the movement of the piston. The work machine further comprises a control system configured to: receive sensor data from the sensor system; determine, from the sensor data, a current velocity of and current load on the piston; and control deceleration of the piston based upon the current velocity of and current load on the piston so as to reduce an impact load, if any, of the piston upon the first or second end stop.

The present disclosure further provides a method for operating at least one hydraulic cylinder of a work machine, comprising detecting via a sensor system, sensor data indicative of the status of at the least one hydraulic cylinder, arm arrangement and/or tool.

The method further comprises receiving by a control system the sensor data, and determining from the sensor data a current status of the at least one hydraulic cylinder, arm arrangement and/or tool. The method further comprises determining, based upon the current status, whether the piston is going to come into contact with the first or second end stop and calculating the impact load of this contact. If the impact load is above an impact parameter threshold, the method comprises limiting the motion of the piston to reduce the impact load. As a result of operating at a work machine with this method, the service interval and mean time between failures of hydraulic cylinders will be increased, as the severity of loads transmitted between the piston and the end stops will be reduced.

Brief Description of the Drawings

By way of example only, embodiments according to the present disclosure are now described with reference to, and as shown in, the accompanying drawings, in which: Figure 1 is a side elevation of an embodiment of a work machine of the present disclosure; Figure 2 is a schematic of a control system of the work machine of Figure 1; Figure 3 is a flow chart of a method for operating a work machine according to an

embodiment of the present disclosure;

Figure 4 is a flow chart of a method for operating a work machine in a normal working range; Figure 5 is a flow chart of a method for operating a work machine according to an

embodiment of the present disclosure; and

Figure 6 is a schematic of a hydraulic cylinder according to an embodiment of the present disclosure.

Detailed Description

The ensuing description provides preferred exemplary embodiment(s) only, and is not intended to limit the scope, applicability or configuration of the invention. Rather, the ensuing description of the preferred exemplary embodiment(s) will provide those skilled in the art with an enabling description for implementing a preferred exemplary embodiment of the invention, it being understood that various changes may be made in the function and arrangement of elements, including combinations of features from different embodiments, without departing from the scope of the invention. Specific details are given in the following description to provide a thorough understanding of the embodiments. However, it will be understood by one of ordinary skill in the art that embodiments may be practised without these specific details. For example, well-known circuits, processes, algorithms, structures, and techniques may be shown without unnecessary detail in order to avoid obscuring the embodiments.

Also, it is noted that the embodiments may be described as a process which is depicted as a flowchart, a flow diagram, a data flow diagram, a structure diagram, or a block diagram.

Although a flowchart may describe the operations as a sequential process, many of the operations can be performed in parallel or concurrently. In addition, the order of the operations may be re-arranged. A process is terminated when its operations are completed, but could have additional steps not included in the figure. A process may correspond to a method, a function, a procedure, a subroutine, a subprogram, etc. When a process corresponds to a function, its termination corresponds to a return of the function to the calling function or the main function. Moreover, as disclosed herein, the term "storage medium" may represent one or more devices for storing data, including read only memory (ROM), random access memory (RAM), magnetic RAM, core memory, magnetic disk storage mediums, optical storage mediums, flash memory devices and/or other machine readable mediums for storing information. The term "computer-readable medium" includes, but is not limited to, portable or fixed storage devices, optical storage devices, wireless channels and various other mediums capable of storing, containing or carrying instruction(s) and/or data.

Furthermore, embodiments may be implemented by hardware, software, firmware, middleware, microcode, hardware description languages, or any combination thereof. When implemented in software, firmware, middleware or microcode, the program code or code segments to perform the necessary tasks may be stored in a machine readable medium such as storage medium. A processor(s) may perform the necessary tasks. A code segment may represent a procedure, a function, a subprogram, a program, a routine, a subroutine, a module, a software package, a class, or any combination of instructions, data structures, or program statements. A code segment may be coupled to another code segment or a hardware circuit by passing and/or receiving information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, etc. may be passed, forwarded, or transmitted via any suitable means including memory sharing, message passing, token passing, network transmission, etc. It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various embodiments. Specific examples of components and arrangements are described below to simplify the present disclosure.

These are, of course, merely examples and are not intended to be limiting. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact.

Figure 1 illustrates an embodiment of a system 9 comprising a work machine 10, in this case an excavator. The work machine 10 may be any suitable type of work machine 10, including multi-purpose work machines, such as excavators, backhoes, loaders, dozers, shovels, fellers, harvesters, material handlers and other such work machines.

The work machine 10 may comprise a swing apparatus 11 and may comprise a swing base 13. The swing apparatus 11 comprises an arm arrangement 14. The swing apparatus 11 may comprise a main body 12. The swing base 13 may comprise an undercarriage 32 and/or a platform. The undercarriage 32 may comprise wheels or tracks 20. The main body 12 may comprise a cab 8 for an operator and a power unit (not shown) therein for providing power to the wheels or tracks 20.

The swing apparatus 11 may be attached to the swing base 13 via a swivel mount 31. The swivel mount 31 may allow the swing apparatus 11 to rotate in relation to the swing base 13. The swivel mount 31 may comprise a slip ring or a slewing ring. Rotation of the swing apparatus 11 relative to the swing base 13 may be actuated using a swing actuator 30. The swing actuator 30 may comprise a hydraulic motor or a hydraulic swivel.

The swing apparatus 11 may be rotatable about a swing axis 33. The swing apparatus 11 may be able to rotate by 360 degrees relative to the swing base 13 about the swivel mount 31 and/or swing axis 33. The swing axis 33 may be perpendicular to the swing base 13 and/or may be perpendicular to a horizontal plane or the ground when the work machine 10 is on a level surface. The swing axis 33 may be a central axis of the swivel mount 31 and may be the axis of rotation of the swing apparatus 11 relative to the swing base 13 at the swivel mount 31.

The arm arrangement 14 comprises at least one hydraulic cylinder 18, 19, 21 for controlling the orientation thereof. The at least one hydraulic cylinder 18, 19, 21 is shown in more detail as hydraulic cylinder 600 in Figure 6. The at least one hydraulic cylinder 600 comprises a piston 601 within a cylinder tube 616. The piston comprises a piston head 602, and a piston rod 604 connected to the piston head 602. The piston rod 604 may be configured to move along an axis parallel to the centre axis of the cylinder tube 616, and may be displaced relative to the cylinder tube 616 through an opening 606 in a first end 618 or a second end 620 of the cylinder tube 616. The at least one hydraulic cylinder 600 further comprises at least one end stop 608, 610, and may comprise a first end stop 608 at a first end 618 of the hydraulic cylinder 600 and a second end stop 610 at a second end 620 of the hydraulic cylinder 600.

The end stops 608, 610 may be positioned inside the cylinder tube 616, configured to contact the piston head 602. Alternatively, although not illustrated in the figures, at least one end stop may be configured to contact a portion of the piston rod 604. End stops 608, 610, configured to contact a portion of the piston rod 604 may be outside the cylinder tube 616, and the portion of the piston rod 604 configured to contact such an end stop 608, 610, may have a wider cross-section than the remainder of the piston rod 604.

In particular, the end stop 608 associated with extension of the at least one hydraulic cylinder 600 may be configured to engage with the piston rod 604, and the end stop 610 associated with the contraction of the at least one hydraulic cylinder 600 may be configured to engage the piston head 602. Work machines comprising double-acting hydraulic cylinders may comprise two end stops configured to contact portions of the piston rod 604.

In a further example, the piston rod 604 may be mounted at the opposing end of the cylinder tube 616 to a rod mount (not illustrated) having a greater diameter than the piston rod 604. Instead of having an internal second end stop 610, the second end stop 610 may be formed externally where the rod mount meets the outside of the cylinder tube 616 (i.e. the left hand end of the cylinder tube 616 in Figure 6). Alternatively, an end stop 608, 610 may be formed where the cylinder tube 616 impacts another part of the machine 10, such as another part of the arm arrangement 14.

The terms full range and normal working range describe ranges of possible motion of the piston head 602. Full range is intended to describe the range of motion of the piston 601 which is mechanically possible, i.e. the full physical or mechanical extent of the motion of the piston 601 between a first extreme, in which further motion of the piston 601 (such as by a contacting portion thereof, which may be through piston head 602 or piston rod 604, for example) in one direction is prevented by contact with the first end stop 608, and a second extreme, in which the further motion of the piston 601 (such as by a contacting portion thereof, which may be through piston head 602 or piston rod 604, for example) in an opposing direction is prevented by contact with the second end stop 610.

The piston rod 604 is moved by directing work machine fluid into the cylinder tube 616 through at least one inlet 612. The at least one inlet 612 may be at the first end 618 of the at least one hydraulic cylinder 600. The at least one hydraulic cylinder 600 may comprise an inlet 614 at the second end 620 of the at least one hydraulic cylinder 600 for receiving work machine fluid. Alternatively or additionally the at least one hydraulic cylinder 600 may comprise a spring or motor for resetting the position of the piston 601.

The at least one inlet 612 of the at least one hydraulic cylinder 600 may be within a cylinder cap (not shown in Figures), which may further comprise a rod bearing band, a rod seal, and/or a wiper.

The at least one inlet 612, 614 may be situated level with or distally spaced from the surface of the end stop 608, 610, which connects with the surface of the piston head 602. The at least one inlet 612, 614 may be substantially perpendicular to the circumferential surface 622 of the cylinder tube 616, or substantially parallel to the circumferential surface 622 of the cylinder tube 616 (as shown in Figure 6).

The work machines 10 and methods described herein are compatible with various known hydraulic cylinders 600, such as double acting hydraulic cylinders 600, telescopic cylinders, and single acting cylinders. The boom, stick and tool hydraulic cylinders 18, 19, 21 may each comprise a piston rod 604.

Work machine fluid may be supplied to the at least one hydraulic cylinder 600 to displace the piston rod 604 relative to the cylinder tube 616. The boom hydraulic cylinder 18 may comprise a boom hydraulic piston rod (not shown). The stick hydraulic cylinder 19 may comprise a stick hydraulic piston rod 5. As the boom hydraulic piston rod and/or the stick hydraulic piston rod 5 are extended, the position of the arm arrangement 14 changes. A boom hydraulic piston rod extension and/or a stick hydraulic piston rod extension may be used to define the position of the arm arrangement 14.

The arm arrangement 14 may comprise a boom 16 and a stick 17. The boom 16 and the stick 17 may be pivotally attached to one another. The boom 16 may be pivotally attached to the main body 12 at a first end of the boom 16. The stick 17 may be pivotably attached to the boom 16 at a second end of the boom 16 and a first end of the stick 17. A tool 15 may be connected to the arm arrangement 14. The tool 15 may be pivotably attached to the stick 17 at a second end of the stick 17. In particular, the arm arrangement 14 may comprise the boom hydraulic cylinder 18 for controlling the orientation and movement of the boom 16. The arm arrangement 14 may comprise the stick hydraulic cylinder 19 for controlling the orientation and movement of the stick 17. The arm arrangement 14 may comprise the tool hydraulic cylinder 21 for controlling the orientation and movement of the tool 15.

The tool 15 may be of any suitable type. The tool 15 may, for example, be a bucket as illustrated or may be a grapple, tiltable bucket, tilt rotator, hammer, handling arm, multiprocessor, pulveriser, saw, shears, blower, grinder, tiller, trencher, winch, auger, broom, cutter, planer, delimber, felling head, mulcher, or rake. The tool 15 may comprise a spray head or the like for providing a water spray during operation of the work machine 10, for example for dust suppression. The fluid may be pressurised hydraulic fluid, water or the like.

The work machine 10 may comprise a work machine fluid circuit (not shown) around which fluid may be circulated. The work machine 10 may comprise a controller 51 for controlling the work machine fluid circuit automatically or based upon inputs received from at least one input device 6 (shown in Figure 1). The at least one input device 6 may comprise one or more of a joystick, a display 57, a touch screen, a button, or any suitable input device. The least one input device 6 may be used to operate the work machine 10. The work machine 10 may be operated to change the position of the arm arrangement 14. The work machine fluid circuit may be connected to the at least one hydraulic cylinder 18, 19, 21. Changing the position of the arm arrangement 14 may comprise controlling the at least one hydraulic cylinder 18, 19, 21 for pivoting of the arm arrangement 14 and the tool 15. The work machine fluid circuit may be connected to the swing actuator 30 and a swing brake 34 for controlling the swing of the swing apparatus 11 relative to the swing base 13.

The system 9 comprises a control system 50, which may be configured to perform the methods of the present disclosure. As illustrated in Figure 2, the control system 50 may comprise the controller 51, which may comprise a memory 53, which may store instructions or algorithms in the form of data, and a processing unit 55, which may be configured to perform operations based upon the instructions. The controller 51 may be of any suitable known type and may comprise an engine control unit (ECU) or the like. The memory 53 may comprise any suitable computer-accessible or non-transitory storage medium for storing computer program instructions, such as RAM, SDRAM, DDR SDRAM, RDRAM, SRAM, ROM, magnetic media, optical media and the like. The processing unit 55 may comprise any suitable processor capable of executing memory-stored instructions, such as a microprocessor, uniprocessor, a multiprocessor and the like. The controller 51 may further comprise a graphics processing unit for rendering objects for viewing on the display 57 of the control system 50. The controller 51 may also be in communication with least one work machine communication module 59 for transferring data with an external computing system 61 via a wired or wireless network 63 (such as Ethernet, fibre optic, satellite communication network, broadband communication network, cellular, Bluetooth). The external computing system 61 may comprise computing systems, processors, servers, memories, databases, control systems and the like.

As summarised in Figure 2, the system 9 may comprise at least one system actuator 4. The at least one system actuator 4 may comprise one or more of the boom, stick and tool hydraulic cylinders 18, 19, 21, the swing actuator 30 and the swing brake 34.

The system 9 comprises a sensor system 7. The sensor system 7 may comprise one or more position sensors 71, movement or acceleration sensors 73, velocity sensors 75, load sensors 77, inertial measurement units (IMU), accelerometers, gyroscopes, magnetometers, strain gauges, temperature sensors and/or pressure sensors. In order to reduce complexity of the work machine 10, it may be beneficial to reduce the number of sensors necessary. In particular, the sensor system 7 may comprise at least one position sensor for determining the relative positions of the arm arrangement 14 and/or tool 15, at least one accelerometer for determining the acceleration of the arm arrangement 14 and/or tool 15, and/or at least one pressure sensor for determining at least one pressure in the at least one hydraulic cylinder 18, 19, 21, 600. The sensor system 7 may comprise one or more temperature sensors configured to measure the temperature of the work machine fluid.

The controller 51 may be communicatively connected (via a wired or wireless connection) to the power unit, and any of the at least one system actuator 4 and/or the sensor system 7 for providing control signals thereto and receiving sensor signals therefrom in order to control the operation of the work machine 10. The controller 51 may communicate with the input device 6, for receiving an input from the operator and for controlling the work machine 10 based upon such inputs.

An embodiment of a method for operating a work machine of the present disclosure is shown in Figure 3. In an initial step 301, the control system 50 may receive user set parameters. User set parameters may include an abuse event severity level, which sets the level of the load parameter thresholds. When an abuse event is detected, the work machine 10 may enter a state of normal working range operation (step 308).

The normal working range (referred to as "NWR" in the Figures) is a range of motion smaller than the full range. The normal working range may be the full range less a cushioning distance, or snubbing area, from the first and/or second extremes. The cushioning distance subtracted from the first extreme may be different from the cushioning distance subtracted from the second extreme. This latter feature is advantageous, if, for example only one of the two end stops 608, 610, is likely to be subject to adverse loading from abuse events, or if the end stops 608, 610 are configured to contact different portions of the piston 601, such as if the first end stop 608 is configured to contact the piston head 602, and the second end stop 610 is configured to contact the piston rod 604.

The cushioning distance may be determined such that there is sufficient work machine fluid between the piston head 602 and the first or second end stops 608, 610 or first end 618 or second end 620, that the work machine fluid and circumferential surface 622 of the at least one hydraulic cylinder 600 can absorb some of the load. The cushioning distance may be a function of the length of the hydraulic cylinder 600 (wherein, hydraulic cylinder length is taken to be the distance between the first end 618 and second end stops 620). The suitable cushioning distance may be at least 1% of the hydraulic cylinder length. The suitable cushioning distance may be 1-2% of the hydraulic cylinder length, 1-5% of the hydraulic cylinder length, or 2-5% of the hydraulic cylinder length. The cushioning distance may further be a function of the type of tool 15 attached to the work machine 10 and/or the temperature of the work machine fluid.

The abuse event severity level may, for example, involve selecting from 'OFF' (in which the method is not performed, and the machine operates in full range operating mode), 'LEAST SENSITIVE' (in which the load parameter thresholds are set to high values, resulting in fewer events triggering normal working range operation), 'STANDARD' (a middle value), and/or 'MOST SENSITIVE' (in which the load parameter thresholds are set to low values, resulting in more events triggering normal working range operation).

Further user set parameters may comprise disabling alerts or specific features of alerts, such as an audible alarm. In particular, it may be desirable to disable first alert to operator 406, in which an abuse event is detected, but the piston head 602 position is inside the normal working range, so no corrective action is necessary and the operator is unlikely to notice the reduced operating characteristics. Further user set parameters may include enabling or disabling an 'auto-protect' feature 403, in which the piston head 602 position is automatically corrected if the at least one hydraulic cylinder 600 is determined as operating outside the normal working range during an abuse event.

The control system 50 may then either load the default parameters 302 if no user set parameters are entered, or override the default parameters 303 where the user has set parameters. The appropriate parameters may then be stored 304 for use later in the method. The default parameters, in particular the load parameter thresholds, may be a function of the tool 15 which is attached to the work machine. The default and/or user parameters may be stored in the memory 53 of the control system 50. The default parameters may be a function of the type of tool 15 attached to the work machine 10. In particular, certain tools 15 may be more susceptible to particular abuse events and therefore would benefit from lower load parameter thresholds for particular modes. The tool 15 type may be selected by the operator via the input device 6 on start up of the work machine 10, or else communicated to the control system 50 through an identification signal from the tool 15.

The sensor system 7 then detects sensor data indicative of the status of the at least one hydraulic cylinder 600. The sensor data may comprise velocity, position, acceleration, work machine fluid temperature, and/or load data. The control system 50 then receives sensor data from the sensor system 7, in step 305.

The control system 50 then determines, in step 306, on the basis of the sensor data, a current status of the at least one hydraulic cylinder 600, arm arrangement 14, and/or tool 15. The current status of the at least one hydraulic cylinder 600 may comprise the kinetic energy, momentum, position, velocity, and/or acceleration of the at least one hydraulic cylinder 600 and/or piston head 602 of the at least one hydraulic cylinder 600.

The control system 50 then determines whether a calculated load parameter is greater than a load parameter threshold in step 307. The load parameters may include frequencies of vibration, velocities, momenta, kinetic energies, pressures and/or accelerations as well as functions thereof. The calculated load parameter and/or load parameter threshold may be a function of the detected position of the arm arrangement 14, since certain abuse events may be more likely in certain configurations, so it may be advantageous to either lower the load parameter threshold, or (equivalently) increase the load parameter by some factor (and vice versa).

The control system 50, may only perform the step of determining the current status and/or comparing the load parameters to the load parameter threshold if the current position of the piston 601 of the at least one hydraulic cylinder 600 is outside the normal working range of operation of the at least one hydraulic cylinder 600.

Figure 4 shows a flow chart illustrating possible steps when an abuse event is detected, and the hydraulic cylinder 600 is operated in normal working range operation 308. The control system 50 may determine if the piston 601 of the at least one hydraulic cylinder 600 is operating outside of the normal working range by receiving sensor data from the sensor system 7, as in step 400.

If the piston 601 of the at least one hydraulic cylinder 600 is not operating outside of the normal working range, the control system 50 may communicate a first alert to the operator as in step 406. The alert may comprise an audio warning and/or a message on a screen in the cab 8. If the at least one hydraulic cylinder 600 is operating outside of the normal working range, the control system 50 may then determine if the auto-protect feature is enabled, as in step 401. If the auto-protect feature is enabled, a first alarm may be triggered, as in step 402, and the piston 606 may move automatically to within the normal working range as in step 403. The at least one hydraulic cylinder 600 may then operate within the normal working range until the load parameter is less than the load parameter threshold, as in step 307. If the auto-protect feature is disabled, a second alert may be displayed or sounded. The second alert may sound or appear differently to the first alert, to indicate its increased severity compared to the first alert.

There may be a delay before automatic motion of the at least one hydraulic cylinder 600 of the work machine to inside the normal working range. The delay may be a time delay, which may be 1, 2, 5, or 10 seconds, or for a period of time which is customisable by the operator, for example between 0 and 30 seconds. Alternatively or additionally, the automatic motion of the at least one hydraulic cylinder 600 of the work machine 10 to inside the normal working range may be delayed until an acknowledgement of the automatic motion by an operator, which may be pushing a button, such as on a control screen displaying an alert. Preferably, the delay may be on a timer, and the operator may be able to accept the automatic motion, thereby expediting the timer, or cancel the automatic motion. The work machine 10 may not respond to additional inputs during this delay. The work machine 10 may function normally during this delay period with an alarm signal. The operator may be able to override normal working range operation from this alert. The purpose of any of the delay periods as described above may be to provide sufficient warning and/or ability to cancel automatic motion so as to avoid potential safety incidents.

During normal working range operation, the operator may be able to override normal working range operation through using the at least one input device 6 in response to an alert, alarm, or a message, which may be displayed on the display 57. Alternatively, the action of overriding may only be performed by a supervising operator with an access code, other key, or alternative security feature, such as multi-factor authentication via a mobile device.

Optionally, the control system 50 may utilise machine learning to improve its abuse event detection. Cancelling of normal working range operation may result in a prompt to the operator on the display 57 asking if the reason for cancellation was because the work machine was not in an abuse mode; if the operator selects yes, this may be used to train the control system to update load parameter thresholds. This update may, in particular, be related to the position of the arm arrangement 14.

When operating within the normal working range, the control system 50 may communicate with the controller 51 for controlling the work machine fluid circuit to limit the flow of work machine fluid to prevent the at least one hydraulic cylinder 600 from operating outside the normal working range. This control may include a feedback loop, which may use the input controls and/or the current status of the at least one hydraulic cylinder 600, in particular using sensor data from velocity, position, and acceleration sensors to determine appropriate flow rates of work machine fluid. To automatically return the at least one hydraulic cylinder 600 to inside a normal working range, the control system 50 may communicate with the controller 51 and may further calculate a volume of work machine fluid which is required to be pumped into the at least one hydraulic cylinder 600 to leave a suitable cushioning distance between the piston 601, piston head 602 or piston rod 604 and the end stop 608, 610. This calculation may be performed using position sensor data from at least one position sensor.

Figure 5 illustrates a flow chart of a further embodiment of a method for operating at least one hydraulic cylinder 600 of the work machine 10, which may be performed alternatively or additionally to the previously disclosed features.

The sensor system 7 may measure the velocity and position of the piston 601, as in step 501. The velocity of the piston 601 may be calculated directly with a velocity sensor 75 on the piston rod 604, or indirectly, through a combination of position, velocity, and acceleration sensors on other parts of the work machine 10, with the velocity of the piston 601 being calculated using geometry. The sensor system 7 may also measure the temperature of the work machine fluid.

The sensor system 7 may further measure the load being transmitted through the at least one hydraulic cylinder 600, as in step 502. The load measurement may be through a load sensor 77, which may measure any of work machine fluid pressure, deflection, material strain and/or other indicators of mechanical load as are known in the art.

The control system 50 may then determine on the basis of the position and velocity of the piston 601, and the load on the piston 601, whether deceleration is required to avoid a hard impact on the first or second end stop 608, 610, as in step 503. The control system 50 may then control the deceleration of the piston 601 based upon the current velocity of and current load on the piston 601, as in step 504.

The required deceleration may be calculated so as to avoid the piston 601 contacting an end stop 608, 610 with a momentum greater than or equal to a particular momentum threshold. The momentum threshold may be settable by the operator. Optionally, the momentum threshold may only be set by a supervising operator with an override key or code.

Alternatively or additionally, the control system 50 may control deceleration of the piston 601 by determining whether, based on current parameters, the piston 601 is going to contact the first or second end stop 608, 610, and calculate predicted impact parameters of this contact. If a predicted impact parameter is above an impact parameter threshold, the control system 50 may limit the motion of the piston 601 to reduce the impact load. The impact parameter thresholds may be a function of the tool 15 attached to the work machine 10. The impact parameter thresholds may be a function of the relative positions of the arm arrangement 14 and tool 15; for example, the threshold may be different if the direction of travel of the piston 601 is substantially with the direction of the gravitational force, than if the direction of travel of the piston 601 is substantially against or perpendicular to the direction of the gravitational force. The impact parameter thresholds may be settable by the operator. Optionally, the impact parameter thresholds may only be set by a supervising operator with an override key or code. The impact parameter thresholds may be a function of the end stop design. Examples of end stop design features which may be used to calculate impact parameter thresholds include whether the end stop is configured to contact the piston head 602 or the piston rod 604.

The control system 50 may continually re-calculate the predicted impact parameters while controlling deceleration of the piston 601. The control system 50 may comprise a feedback loop for controlling the deceleration of the piston 601. Calculation of the predicted impact parameters by the control system 50 may comprise calculating predicted impact velocity of the piston 601, predicted impact load on the piston 601, predicted impact position of the arm arrangement 14, predicted impact momentum, and/or predicted impact kinetic energy.

The calculation of predicted impact parameters may comprise calculations involving: the current velocity of the piston 601, the load on the piston 601, and may optionally further comprise the position and acceleration of the piston 601, and/or an input from the operator through input device 6. The calculation of impact parameters may comprise calculations involving the work machine fluid temperature, such as incorporating temperature dependence of fluid and/or material properties.

The impact parameter thresholds may comprise maximum impact velocity, maximum load, maximum momentum, and/or maximum kinetic energy values. The impact parameter thresholds may also comprise threshold values which are a function of any combination of predicted impact velocity of the piston 601, predicted impact load on the piston 601, predicted impact position of the arm arrangement 14, predicted impact momentum, and/or predicted impact kinetic energy. The impact parameter thresholds may comprise a maximum work machine fluid temperature, and/or be dependent upon the work machine fluid temperature.

The method of Figure 5 may further comprise determining, based upon the current velocity and/or load, a deceleration start point at which velocity of the piston 601 should be decelerated so as to reduce an impact load, if any, of the piston 601 upon the first or second end stop 608, 610, and operating the piston 601 to decelerate upon reaching the deceleration start point. The control system 50 may further control the deceleration of the piston 601 so as to avoid impact with the first and/or second end stop 608, 610, maintaining a minimum clearance between the piston 601 and the first and/or second end stop 608, 610. In particular, the minimum clearance may be 1% of the length of the cylinder, 2% of the length of the cylinder, 5% of the length of the cylinder, 1-2% of the length of the cylinder, 1-5% of the length of the cylinder, or 2-5% of the length of the cylinder.

An alert may be communicated to the operator when the control system 50 determines that an impact which will require automatic deceleration will be required. An additional or alternative alert may be communicated to the operator when the controlled deceleration of the present disclosure begins. These alerts may be audible warnings and/or may be visual warnings displayed on a display 57.

The minimum clearance may be settable by an operator. The minimum clearance may only be settable by a supervising operator with an access code, other key, or alternative security feature, such as multi-factor authentication via a mobile device. Alternatively and/or additionally, an operator or supervising operator may input an override command to the input device 6 such that, for a set period of time, the control system does not limit the motion of the piston 601. The set period of time may be until the machine is restarted. The minimum clearance may further be a function of the type of tool 15 attached to the work machine 10.

The control system 50 may further limit the maximum velocity of extension and/or contraction of the at least one hydraulic cylinder 600.

The memory 53 of the control system 50 may store data on the status of the at least one hydraulic cylinder 600, arm arrangement 14, and/or tool 15.

The control system 50 may communicate with the controller 51 for controlling the work machine fluid circuit to control the flow of work machine fluid to control the deceleration of the piston 601. This control may include a feedback loop, which may use the input controls and/or the current status of the at least one hydraulic cylinder 600, in particular using sensor data as described above to determine appropriate flow rates of work machine fluid.

An alert signal may be communicated to the operator when the control system 50 is limiting the motion of the at least one hydraulic cylinder 600. The alert signal may be an audible alarm and/or a visual warning on the display 57.

A work machine according to the present disclosure may perform both the method substantially illustrated by the embodiment of Figure 3 and that substantially illustrated by the embodiment of Figure 5.

Industrial Applicability

The at least one hydraulic cylinder 600 of the work machine of the present disclosure, or the at least one hydraulic cylinder 600 operated according to the method of the present disclosure may therefore be operated with longer service intervals, and have increased service lives compared to those without such a system.

Through limiting extension only in the detection of abuse events, operators are able to use the full extent of the extension of the at least one hydraulic cylinder 600 during full range operation. This is beneficial compared to known systems using mechanical snubbing, during which the effective length of the cylinder is substantially reduced.

In addition, allowing operators to have some control over the load parameter thresholds for abuse event detection and/or impact parameter thresholds, and the severity of the action taken to reduce the wear on the at least one hydraulic cylinder 18, 19, 21, 600 will allow for newer operators to have stricter controls as they learn. The alert system will also teach operators about the sorts of events that can result in machine damage.

Claims

CLAIMS: 1. A work machine comprising: an arm arrangement and a tool mounted to the arm arrangement; at least one hydraulic cylinder comprising a piston extendable along a full range determined by first and second end stops to actuate the arm arrangement and/or tool; a sensor system for generating sensor data indicative of the movement of the piston; and a control system configured to: receive sensor data from the sensor system; determine, from the sensor data, a current velocity of and current load on the piston; and control deceleration of the piston based upon the current velocity of and current load on the piston so as to reduce an impact load, if any, of the piston upon the first or second end stop.
2. A work machine as claimed in claim 1 wherein the control system is configured to determine control deceleration of the piston by: determining, based upon the current velocity, whether the piston is going to contact the first or second end stop and calculate impact parameters of this contact; and if an impact parameter is above an impact parameter threshold, limiting the motion of the piston to reduce the impact load.
3. A work machine as claimed in any preceding claim wherein the control system is configured to control deceleration of the piston by: determining, based upon the current velocity, a deceleration start point at which velocity of the piston should be decelerated so as to reduce an impact load, if any, of the piston upon the first or second end stop; and operating the piston to decelerate upon reaching the deceleration start point.
4. The work machine of claim 1, wherein an alert signal is communicated to an operator when the control system is limiting the motion of the hydraulic cylinder.
5. The work machine of any preceding claim, wherein the impact parameters comprise any of a velocity, a static force, and/or a momentum.
6. The work machine of any preceding claim, wherein the impact parameter thresholds can be set by an operator.
7. The work machine of any preceding claim wherein the impact parameter thresholds are a function of the attached tool.
8. The work machine of any preceding claim wherein the impact parameter thresholds are a function of the relative positions of the arm arrangement and tool.
9. The work machine of any preceding claim wherein the sensor system comprises a position sensor and/or an accelerometer and/or a pressure sensor.
10. The work machine of any preceding claim wherein the control system is configured to limit the motion of the hydraulic cylinder such that there is a minimum clearance between the piston and the first and/or second stop.
11. The work machine of claim 8 wherein an operator can determine the minimum clearance.
12. The work machine of any preceding claim wherein the control system is configured to limit the motion of the hydraulic cylinder such that the velocity of the extension and/or contraction of the hydraulic cylinder is limited.
13. The work machine of any preceding claim, wherein the operator can input an override command such that for a set period of time, the control system does not limit the motion of the piston.
14. The work machine of any preceding claim further comprising a memory for storing data on the status of the at least one hydraulic cylinder, arm arrangement, and/or tool.
15. A method for preventing damage to hydraulic cylinders of work machines comprising: detecting via a sensor system, sensor data indicative of the status of at the least one hydraulic cylinder, arm arrangement and/or tool; receiving by a control system the sensor data; determining from the sensor data a current status of the at least one hydraulic cylinder, arm arrangement and/or tool; determining, based upon the current status, whether the piston is going to come into contact with the first or second end stop and calculating the impact load of this contact; and if the impact load is above an impact parameter threshold, limiting the motion of the piston to reduce the impact load.