This application is the U.S. National Stage entry under 35 U.S.C. § 371 of International Patent Application No. PCT/NO2016/050119, filed Jun. 8, 2016, and entitled “Improvements in the Control of Hydraulic Actuators,” and European Patent Application EP15171831.9 filed Jun. 12, 2015, which are hereby incorporated by reference in their entirety for all purposes.
The present disclosure relates in particular to the operation and control of hydraulic actuators.
Hydraulic actuators are used in a wide range of industrial applications for handling loads. Examples include uses for example in large-scale industrial apparatus for lifting and manipulating heavy equipment, such as cranes, elevators, manipulator arms or the like. Such apparatus are typically supplied with power fluid for driving the actuators through a hydraulic circuit. The circuit may include components such as valves or the like which are configured in response to a sensed load on the actuator to operate and control the actuator appropriately. Components in such circuits may operate under data control for example electrically by supplying electrical control signals to the components and/or under fluid control by supplying a control fluid to the components, but at the same time it is typically of interest that such control arrangements avoid unnecessary complexity. In large-scale equipment, power requirements for the actuators may be substantial and as such prevailing thinking has been to keep both the power supply and control circuitry straightforward and reliable, for reducing potential failures in the hydraulic circuitry or actuator where such an eventuality could be safety concern and be costly to rectify. In harsh environments, such as on marine platforms or vessels, for example in the oil and gas exploration and production industry, provision of simple, reliable and safe systems for delivering hydraulic operability of this kind has been paramount. Downtime due to failures in equipment in this industry can also be very costly.
In
The hydraulic power fluid is supplied from a tank 4 with the assistance of a pump 5, and is guided through the circuit 2 to the first or second sides 3a, 3b of the actuator 3 as appropriate. Power fluid is supplied into a chamber in the piston housing 3h on one of the sides 3a, 3b, causing movement of the piston 3p toward the other side, whilst power fluid is expelled from the chamber in the piston housing 3h on the other of the sides 3a, 3b and is guided back through the circuit to a drain 6 along a drain line 13.
The power fluid is guided into the actuator via line 8 or line 7. To facilitate this, the circuit 1 has load-sensing directional control valve 9. The configuration of the directional control valve 9 determines the route for the hydraulic power fluid from the pump 5 to the actuator 3. In
The load exerted on the actuator 3 may vary, and in view of this, the circuit 2 includes certain control measures. Firstly, the circuit 2 is provided with a pressure compensating valve 10. The pressure compensating valve 10 is configured to adjust the flow of power fluid from the pump 5 so that a suitable pressure is applied so that the piston 3b is moved at a particular speed. Secondly, the circuit 2 is provided with a counterbalance valve 11. The counterbalance valve 11 is configured to adjust the flow of returning power fluid from the actuator 3 to control the pressure on the second side 3b of the actuator 3 against which the piston 3p needs to act. This is intended to help to control the speed and stop the piston 3p running away in the event of load components which may be exerted in the same direction as the piston movement. In this way, the circuit 2 using the counterbalance valve 11 and the pressure compensating valve 10 provides a way for the speed of the actuator 3 to be independent of the load and for overrunning loads to be handled.
Nevertheless, the circuit 2 can experience practical difficulties in that instabilities can appear over time leading to a loss of control of movement of the piston 3p, e.g. in the event of overrunning loads, which in turn may cause cavitation damage in the metering-in line 7 (or line 8 which is the metering-in line when moving in the other direction) and/or damage to the piston 3p and/or the piston housing 3h. It is also typically desirable to ensure that the movement of the actuator 3, e.g. speed of piston 3b, is unchanged over a range of different loads, in order to handle loads safely and predictably. This issue can be further understood by further considering the operation of the counterbalance valve 11 and the pressure compensation valve 10 in
The counterbalance valve 11 is controlled using control lines 11a, 11b which supply control fluid to the valve 11 for configuring the valve, e.g. positioning a valve spool so as to restrict or permit fluid flow through the valve by an amount determined by the control fluid in the control lines 11a, 11b. The control line 11a is connected to the line 7 supplying fluid to the first side 3a of the actuator 3, and the control line 11b is connected to the line 8 from the second side 3b of the actuator. In this way, the valve 11 can sense the pressure in the power fluid being supplied to the first side 3a in line 7 and the pressure in the returning power fluid from the second side 3b of the actuator in line 8, and is configured according to the difference in pressure between the first and second sides 3a, 3b of the actuator 3. In the event that the actuator 3 experiences an overrunning load, for example, an effect is produced on the pressures in the power fluid on the first and second sides 3a, 3b of the actuator, and the valve responds accordingly through the control lines 11a, 11b to configure the valve to limit the flow out of the second side 3b actuator to resist the load, to restore the pressure differential.
The pressure compensating valve 10 is controlled using control lines 10a, 10b which supply control fluid to the valve 10 for configuring the valve, e.g. by positioning a valve spool so as to restrict or permit fluid flow from the pump 5 through the valve by an amount determined by the control pressure in the control lines 10a, 10b. As can be seen, the control line 10a is connected to an outlet side of the load-sensing directional control valve 9, which when block 9a is active (for moving the actuator piston 3p toward the second side 3b), senses the pressure in the power fluid being supplied into the first side of the piston via line 7. The control line 10b is connected to the inlet side of the load-sensing directional control valve 9 which senses the pressure of the power fluid being supplied into the directional control valve 9 through supply line 12. The valve therefore adjusts to compensate for any pressure drop in the power fluid across the load-sensing directional control valve 9. The pressure compensating valve 10 is further configured to allow an increased or decreased flow into the first side of the actuator 3a to facilitate the same speed of movement of the piston 3p for different loads. In the event of a change in load, e.g. an overrunning load, pressure effects in the first side 3a of the actuator 3c can lead to the valve 10 increasing or decreasing the pressure in line 12 to maintain the same pressure drop in the fluid flowing through the directional control valve 9 from line 12 to line 7 via block 9a, thereby counteracting the influence of the pressure effect on the speed of the actuator 3.
The actuator 3, in particular the speed and movement of the piston 3p when handling loads, is therefore controlled by way of counterbalance valve 11 and the pressure compensating valve 10 acting and cooperating together. However, valve responses to the load conditions can be imperfect in terms of timings, such that short duration, high frequency pressure perturbations may occur in the power fluid in the metering-in line 7 to the first side 3a of the actuator 3a. Such instabilities may amplify over time, and jeopardize the performance of the actuator 3 in handling loads and adversely affect safety. In particular, the actuator 3 may become susceptible to sudden movements and damage as described above in the event of overrunning loads.
Various solutions have been proposed to deal with this instability issue where additional valves or modifications to the counterbalance valve 11 and/or pressure compensation valve 10 are made but where to their detriment they give up much of the functionality to ensure that the speed of movement of the piston 3p is independent of the load, whilst the effects of overrunning loads are counteracted.
It will be noted that
In addition, it can be noted that
In light of the above, according to a first aspect of the disclosure, there is provided a method of controlling an actuator during operation of a hydraulic circuit, the circuit comprising a first path section along which fluid is supplied to a first chamber of the actuator using a first valve, and a second path section along which fluid is extracted from a second chamber of the actuator using a second valve, the method comprising the steps of:
(a) obtaining pressure data associated with a pressure of the fluid supplied to the first side of the actuator;
(b) producing a pilot pressure pPilot based on the data; and
(c) configuring either or both of the first and second valves using the pilot pressure pPilot.
The pressure data may typically comprise a signal of the pressure in the fluid supplied to the first chamber.
The actuator typically comprises a moving component, movable in dependence upon the pressure of the fluid in said first and/or second chambers, e.g. according to a pressure differential therebetween. The moving component may be for example a piston arm, shaft or rod or the like.
The obtained pressure data may be first pressure data, and the method may further comprise processing the first pressure data to produce second pressure data, wherein the pilot pressure is produced based upon the second pressure data. At least one component from the first pressure data may be preserved in the produced second pressure data.
The obtained pressure data may be first pressure data, and the method may further comprise processing the first pressure data to determine at least one set pressure pSet for determining the pilot pressure.
The step of processing the first pressure data to obtain the second pressure data may comprise filtering the first pressure data. Thus, the first pressure data may be processed to remove at least one frequency component. Accordingly, the step of processing the first pressure data to obtain the second pressure data may be performed to remove high frequency components. The second pressure data, e.g. time-series data, may thus be based on the first data, without the removed high-frequency component or components. The second pressure data obtained may therefore typically not contain the removed component or components.
The step of filtering may be performed to remove one or more high-frequency components may be removed. The step of filtering may comprise applying a low-pass filter to the first pressure data.
The pilot pressure pPilot may typically be produced using a third valve operable to configure a valve control path. In this way, the third valve may be operable for adjusting a pressure in a control fluid in the valve control path, e.g. within a control fluid circuit.
The method may further comprise generating a control signal uProp based on the second pressure data. The method may include passing the control signal uProp to a third valve to produce the pilot pressure pPilot for configuring either or both of the first and second valves. The third valve may be a pressure relief valve operable to configure a valve control path for adjusting a pressure in a control fluid in the path. The third valve may be a pressure reducing valve operable for configuring a valve control path for adjusting a pressure in a control fluid in the valve control path.
The method may further comprise measuring the produced pilot pressure pPilot, comparing the measured pilot pressure pPilot with the second pressure data, and updating the control signal uProp in dependence upon the comparison.
The first valve may preferably comprise a pressure compensating valve. The pressure compensating may typically be operable for adjusting a pressure of the fluid in the first path section, and/or the first chamber. In doing so, the pressure compensating valve may be operable to configure an inlet pathway for supplying fluid into an inlet of a load-sensing directional control valve.
The second valve may preferably be a counterbalance valve. The counterbalance valve may typically be operable for resisting undesired movement of the actuator. The counterbalance valve may be operable to configure the second path section.
The first and second valves may preferably be configured to be operable to maintain an actuator speed that is independent of external disturbances on the actuator. The first and second valves may cooperate to protect the actuator from being affected by external force components or changes in such force components during movement. Such force components may result from a load such as an overrunning load, or changes in such a load, on the actuator or the moving component thereof.
The first path section may comprise a metering-in line.
The pressure data associated with the pressure in the fluid supplied to the first side of the actuator may comprise at least one pressure pLS of the fluid at an outlet of a load sensing directional control valve.
The method may further comprise measuring at least one pressure pLS to obtain the data. The data may typically be obtained using a pressure transducer.
According to a second aspect of the disclosure, there is provided apparatus for operating and controlling a hydraulic actuator, the apparatus comprising:
first and second valves;
a first path section along which fluid is supplied to a first chamber of the actuator using the first valve;
a second path section along which fluid is extracted from a second chamber of the actuator using the second valve; and
at least one device for producing a pilot pressure pPilot based upon obtained data associated with a pressure of the fluid supplied to the first chamber of the actuator, wherein either or both of the first and second valves are configured using the pilot pressure pPilot.
The apparatus may further comprise the actuator. The device may typically comprise a third valve.
The device may comprise any one or more of: a determiner; a controller; and control structure.
The apparatus may further comprise a control fluid circuit, or a component thereof, for controlling the first and second valves.
According to a third aspect of the disclosure, there is provided a computer device for use in operating and controlling an actuator operable using a hydraulic circuit comprising a path section along which fluid is supplied to a first chamber of the actuator using a first valve, and a path section along which fluid is extracted from a second chamber of the actuator using a second valve, the computer device being configured to receive data associated with a pressure of the fluid supplied to the first chamber of the actuator, for determining a pilot pressure pPilot to be generated based upon the obtained data for configuring either or both of the first and second valves.
According to a fourth aspect of the disclosure, there is provided a computer program for the computer device of the third aspect.
According to a fifth aspect of the disclosure, there is provided a method of controlling an actuator during operation of a hydraulic circuit comprising a first path section along which fluid is supplied to a first chamber of the actuator using a first valve, and a second path section along which fluid is extracted from a second chamber of the actuator using a second valve, the method comprising the steps of:
(a) computing a set pressure pSet in dependence upon a pressure of the fluid supplied to the first chamber of the actuator; and
(b) configuring either or both of the first and second valves based on the computed set pressure.
The method may further comprise producing a pilot pressure pPilot based on the set pressure pSet; and configuring the first and second valves using the pilot pressure pPilot.
According to a sixth aspect of the disclosure, there is provided apparatus for use in controlling an actuator during operation of a hydraulic circuit comprising, the apparatus comprising:
first and second valves;
a first path section along which fluid is supplied to a first chamber of the actuator using the first valve;
a second path section along which fluid is extracted from a second chamber of the actuator using the second valve; and
at least one device for computing a set pressure pSet in dependence upon a pressure of the fluid supplied to the first chamber of the actuator for configuring either or both of the first and second valves based on the computed set pressure.
According a seventh aspect of the disclosure, there is provided a computer device for use in controlling an actuator operable using a hydraulic circuit comprising a path section along which fluid is supplied to a first chamber of the actuator using a first valve, and a path section along which fluid is extracted from a second chamber of the actuator using a second valve, the computer device being configured to compute a set pressure pSet in dependence upon a pressure of the fluid supplied to the first chamber of the actuator, the computed set pressure to be used for configuring either or both of the first and second valves.
According to an eighth aspect of the disclosure, there is provided a computer program for the computer device of the seventh aspect.
Any of the aspects of the disclosure may include further features as described in relation to any other aspect, wherever described herein. Features described in one embodiment may be combined in other embodiments. For example, a selected feature from a first embodiment that is compatible with the arrangement in a second embodiment may be employed, e.g. as an additional, alternative or optional feature, e.g. inserted or exchanged for a similar or like feature, in the second embodiment to perform (in the second embodiment) in the same or corresponding manner as it does in the first embodiment. Embodiments of the claimed invention are advantageous in various ways as will be apparent from the specification throughout.
There will now be described, by way of example only, exemplary embodiments of the invention with reference to the accompanying drawings, in which:
Reference is made firstly to
The circuit 102 has a pressure compensating valve 110 and a counterbalance valve 111 which are configured using a pilot pressure pPilot which is generated based upon a determined pressure pSet. The pressure pSet is determined using a control structure 150. A pressure pLS is measured using a transducer 120 and is passed to a determiner 151 in the control structure 150 as an input, and the pressure pLS is processed in order to determine the pressure pSet for generating the pilot pressure pPilot. The pressure pLS is processed in the determiner 151 by applying a low-pass filter to the pressure pLS, in order to obtain the set pressure pSet. In this way, the set pressure pSet is obtained in dependence upon the pressure as measured in the line 107 with a high frequency component filtered out. This technique can therefore provide an improved basis for configuring the counterbalance valve 111 and the pressure compensating valve 110. The functionality of the counterbalance valve 111 and pressure compensating valve 110 to control the actuator 103 under external loads may thus be improved as the valves 110, 111 can respond on the basis of the pressure in the metering-in line 107 (since the set pressure pSet is based upon the pressure pLS), whilst the processing performed in the control structure 150 can help to suppress instabilities as may be suffered by the prior art.
Whilst this example illustrates that the pressure pLS may be subjected to filtering, it will be understood that other operations may be applied in order to determine a suitable pressure pSet for generating the pilot pressure pPilot. Such operations may for example include removing a noise component, performing signal smoothing or averaging, analysing or performing an estimation using the pressure pLS. In doing so, empirical or numerical methods could be used.
The pilot pressure pPilot is communicated through control lines 110a, 111a to the ‘X’ ports of the valves 110, 111 to configure them accordingly. In order to generate the pilot pressure pPilot, the determiner 150 is used to control a proportional pressure relief valve 130, which is used to adjust the pressure of control fluid in the lines 110a, 111a to correspond with the pressure pSet. A uProp signal is generated based on pSet and is passed to the proportional pressure relief valve 130 to operate it appropriately. The uProp signal is output from the In/Out unit 201 of the computer device 200.
Referring again to
It can be noted further in
When the apparatus 101 is used to move the piston 103p, an input signal uMain is passed to the directional control valve 109 to activate the relevant block 109a and an input signal uDist, based upon the input signal uMain, is sent from the determiner 150 to the pressure distribution valve 131 in order to activate the block 109a so as to communicate the pilot pressure pPilot for configuring the pressure compensating valve 110 and counterbalance valve 111 as described above.
In general, operation is such that a pilot pressure is generated using the determiner 150 on an ongoing basis. The pressure pLS is received and the pressure pSet produced by the determiner as time-series data, and the determiner 150 sends a time-series command signal uProp to the pressure relief valve 130 accordingly. The pilot pressure pPilot generated in the control fluid is thus updated over time, e.g. continuously and/or automatically.
In order to facilitate proper generation of the pilot pressure, the generated pressure pPilot is measured using a pressure transducer 140 and is fed back to the determiner 150 as an input. The measured pilot pressure pPilot and the set pressure pSet are compared for checking agreement between the pressure pPilot actually generated and the determined set pressure pSet. A proportional integral (PI)-control function is used to determine any difference pDelta between the measured pressure pPilot generated in the fluid and the pressure pSet, and applies a gain to the pressure pSet signal if appropriate. The signal uProp is then communicated accordingly, taking into account the gain, to control the pilot pressure pPilot being generated in the fluid via the proportional pressure relief valve 130.
With reference again to
The pressure compensating valve 110 is configured to adjust the flow of power fluid from the pump 105 so that a suitable pressure is applied for moving the piston 103p at a certain speed. The counterbalance valve 111 can adjust the flow of returning power fluid from the actuator 103 to control the pressure in the chamber on the second side 103b against which the piston 103p needs to act to maintain the speed (when moving for example toward the second side 103b). In the event of variations in the load, the counterbalance valve 111 can adjust the path for fluid out of the second side 103b in order to maintain the speed of the piston 103p independently of the load, e.g. to maintain a pressure differential between the chambers on the first and second sides 103a, 103b of the actuator. Control of the valves 110, 111 using the pilot pressure generated as described above facilitates correct performance of the counterbalance valve 111 and the pressure compensating valve 110 such that potential instabilities as may arise by operation of the valves in the presence of overrunning or other externally imparted loads can be suppressed or prevented.
It can further be noted that the pressure compensating valve 110 is controlled according to the pressures in control lines 110a, 110b e.g. by positioning a valve spool as determined by the pressure in the control lines 110a, 110b. In this way, the pilot pressure in the control line 110a can control the valve 110 so as to configure the path for power fluid through the valve 110. The control line 110b is connected to the inlet side of the load-sensing directional control valve 109 and senses the pressure of the power fluid being supplied into the directional control valve 109 through supply line 112.
The counterbalance valve 111 is controlled according to the pressures in control lines 111a, 111b, e.g. by positioning a valve spool so as to restrict or permit fluid flow through the valve 111 by an amount determined by the pressure in the control lines 111a, 111b. In this way, the pilot pressure in the control line 111a can control the valve 111 so as to configure the path for power fluid through the valve 111. The control line 111b is connected to the line 108 from the second side 103b of the actuator 103 so as to sense the pressure in the returning power fluid from the second side 103b of the actuator in line 108.
In
The counterbalance valves 111, 111′ uses separate control lines 111a, 111a′ to the respective X ports of the valves 111, 111′. In order to supply control fluid on these lines 111a, 111a′, the apparatus 101′ has a pressure distribution valve in the form of a directional control valve 531, operating under control of the uDist signal (which in turn is linked to the uMain load sensing signal). When the piston 103p of the actuator 103 is being moved toward the second side 103b (upon application of power fluid into the chamber on the first side 103a), block 531b of the valve 531 is active and control fluid at the pilot pressure pPilot is communicated through the valve 531 into the line 111a and into the port X of the counterbalance valve 111. Conversely, when the piston 103p of the actuator 103 is being moved toward the first side 103a (upon application of power fluid into the chamber on the second side 103b), block 531a of the valve 531 is active and control fluid at the pilot pressure pPilot is communicated through the valve 531 into the line 111a′ and into the port X of the second counterbalance valve 111′. The neutral configuration with block 531c active is shown in
In other variants, other arrangements may be used to generate the pressure pPilot in the control fluid, not necessarily using the proportional pressure relief valve 130 as illustrated in
Turning to
In the above-described embodiments, the pilot pressure pPilot which is generated from pSet as determined by the determiner 150 is communicated to both the counterbalance valve 111 and the proportional pressure relief valve 130. It will however be appreciated that the pressure pPilot from the determiner 150 can in other examples be applied to one or the other of the counterbalance valve 111 and the pressure compensating valve 110 (or the counterbalance valve 111′ and the pressure compensating valve 110 as the case may be). Such examples are illustrated in
In
In
The configurations in
It can be noted that the presently described techniques can be applied with actuators of different types. The actuators may be multi-directional in their movement, and may be controlled in respective directions using apparatus as described. For example, as illustrated in
In
Various modifications and improvements may be made without departing from the scope of the invention claimed below.
Number | Date | Country | Kind |
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15171831 | Jun 2015 | EP | regional |
Filing Document | Filing Date | Country | Kind |
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PCT/NO2016/050119 | 6/8/2016 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
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WO2016/200272 | 12/15/2016 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
4955194 | Christensen | Sep 1990 | A |
5138838 | Crosser | Aug 1992 | A |
20030121409 | Lunzman | Jul 2003 | A1 |
20130298541 | Carlin | Nov 2013 | A1 |
Number | Date | Country |
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0379595 | Aug 1990 | EP |
2667038 | May 2013 | EP |
2667038 | Nov 2013 | EP |
2016200272 | Dec 2016 | WO |
Entry |
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English translation of abstract for EP 2667038 (2 pages). |
Written Opinion for PCT/NO2016/050119 dated Aug. 31, 2016 (8 pages). |
International Search Report for PCT/NO2016/050119 dated Aug. 31, 2016 (5 pages). |
Number | Date | Country | |
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20180180066 A1 | Jun 2018 | US |