Guidelines for Properly Adjustning Pressure Feedback in Systems with Over-Centre Valves

Research output: Contribution to book/anthology/report/conference proceedingArticle in proceedingResearchpeer-review

Abstract

Many mobile hydraulic systems are fitted with over centre valves for safety measures. However, it is well known that over centre valves in combination with pressure compensated flow control valves may lead to oscillatory and even unstable system behaviour. The traditional solution to overcome this problem is to use an over centre valve with a sufficiently low pilot ratio and/or include various damping orifices in the system. Both of these solutions are energy consuming and may decrease the control performance. An alternative approach is to use (electronic) pressure feedback — also referred to as active damping — to stabilise the system and damp pressure pulsations. This is not a new method, but the effect and adjustment of the filters is often misunderstood leading to incorrectly adjusted filters and degraded system performance. The focus of the current paper is therefore to explain and derive a set of guidelines for how to properly adjust a standard pressure feedback in system with an over centre valve when also considering model uncertainties, un-modelled dynamics and parameter variations.
The paper takes its basis in a standard cylinder drive with an inertia load, over centre valve and a pressure compensated proportional valve. Based on a linearized model of the system, the system is analysed and it is shown that there is an optimal range for both the filter frequency and gain, which are closely linked. It is furthermore shown that these both closely affect the obtainable damping and dynamic response of the system. From the analysis a set of guidelines are derived for how to properly adjust the filter coefficients and the effect of different filter adjustments are shown and commented for the example system.
Original languageEnglish
Title of host publicationProceedings of BATH/ASME 2016 Symposium on Fluid Power and Motion Control
Number of pages9
PublisherAmerican Society of Mechanical Engineers
Publication dateSep 2016
Article numberFPMC2016-1780
ISBN (Print)978-0-7918-5006-0
DOIs
Publication statusPublished - Sep 2016
Event BATH/ASME 2016 Symposium on Fluid Power and Motion Control - Bath, United Kingdom
Duration: 7 Sep 20169 Sep 2016
http://www.bath.ac.uk/mech-eng/research/ptmc/symposium

Conference

Conference BATH/ASME 2016 Symposium on Fluid Power and Motion Control
CountryUnited Kingdom
CityBath
Period07/09/201609/09/2016
Internet address

Fingerprint

Feedback
Damping
Pressure control
Orifices
Flow control
Dynamic response
Hydraulics
Uncertainty

Keywords

  • Pressure
  • Valves
  • Feedback

Cite this

Pedersen, H. C., Andersen, T. O., & Hansen, M. R. (2016). Guidelines for Properly Adjustning Pressure Feedback in Systems with Over-Centre Valves. In Proceedings of BATH/ASME 2016 Symposium on Fluid Power and Motion Control [FPMC2016-1780] American Society of Mechanical Engineers. https://doi.org/10.1115/FPMC2016-1780
Pedersen, Henrik Clemmensen ; Andersen, Torben O. ; Hansen, Michael R. / Guidelines for Properly Adjustning Pressure Feedback in Systems with Over-Centre Valves. Proceedings of BATH/ASME 2016 Symposium on Fluid Power and Motion Control. American Society of Mechanical Engineers, 2016.
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Pedersen, HC, Andersen, TO & Hansen, MR 2016, Guidelines for Properly Adjustning Pressure Feedback in Systems with Over-Centre Valves. in Proceedings of BATH/ASME 2016 Symposium on Fluid Power and Motion Control., FPMC2016-1780, American Society of Mechanical Engineers, BATH/ASME 2016 Symposium on Fluid Power and Motion Control, Bath, United Kingdom, 07/09/2016. https://doi.org/10.1115/FPMC2016-1780

Guidelines for Properly Adjustning Pressure Feedback in Systems with Over-Centre Valves. / Pedersen, Henrik Clemmensen; Andersen, Torben O.; Hansen, Michael R.

Proceedings of BATH/ASME 2016 Symposium on Fluid Power and Motion Control. American Society of Mechanical Engineers, 2016. FPMC2016-1780.

Research output: Contribution to book/anthology/report/conference proceedingArticle in proceedingResearchpeer-review

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N2 - Many mobile hydraulic systems are fitted with over centre valves for safety measures. However, it is well known that over centre valves in combination with pressure compensated flow control valves may lead to oscillatory and even unstable system behaviour. The traditional solution to overcome this problem is to use an over centre valve with a sufficiently low pilot ratio and/or include various damping orifices in the system. Both of these solutions are energy consuming and may decrease the control performance. An alternative approach is to use (electronic) pressure feedback — also referred to as active damping — to stabilise the system and damp pressure pulsations. This is not a new method, but the effect and adjustment of the filters is often misunderstood leading to incorrectly adjusted filters and degraded system performance. The focus of the current paper is therefore to explain and derive a set of guidelines for how to properly adjust a standard pressure feedback in system with an over centre valve when also considering model uncertainties, un-modelled dynamics and parameter variations.The paper takes its basis in a standard cylinder drive with an inertia load, over centre valve and a pressure compensated proportional valve. Based on a linearized model of the system, the system is analysed and it is shown that there is an optimal range for both the filter frequency and gain, which are closely linked. It is furthermore shown that these both closely affect the obtainable damping and dynamic response of the system. From the analysis a set of guidelines are derived for how to properly adjust the filter coefficients and the effect of different filter adjustments are shown and commented for the example system.

AB - Many mobile hydraulic systems are fitted with over centre valves for safety measures. However, it is well known that over centre valves in combination with pressure compensated flow control valves may lead to oscillatory and even unstable system behaviour. The traditional solution to overcome this problem is to use an over centre valve with a sufficiently low pilot ratio and/or include various damping orifices in the system. Both of these solutions are energy consuming and may decrease the control performance. An alternative approach is to use (electronic) pressure feedback — also referred to as active damping — to stabilise the system and damp pressure pulsations. This is not a new method, but the effect and adjustment of the filters is often misunderstood leading to incorrectly adjusted filters and degraded system performance. The focus of the current paper is therefore to explain and derive a set of guidelines for how to properly adjust a standard pressure feedback in system with an over centre valve when also considering model uncertainties, un-modelled dynamics and parameter variations.The paper takes its basis in a standard cylinder drive with an inertia load, over centre valve and a pressure compensated proportional valve. Based on a linearized model of the system, the system is analysed and it is shown that there is an optimal range for both the filter frequency and gain, which are closely linked. It is furthermore shown that these both closely affect the obtainable damping and dynamic response of the system. From the analysis a set of guidelines are derived for how to properly adjust the filter coefficients and the effect of different filter adjustments are shown and commented for the example system.

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KW - Feedback

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DO - 10.1115/FPMC2016-1780

M3 - Article in proceeding

SN - 978-0-7918-5006-0

BT - Proceedings of BATH/ASME 2016 Symposium on Fluid Power and Motion Control

PB - American Society of Mechanical Engineers

ER -

Pedersen HC, Andersen TO, Hansen MR. Guidelines for Properly Adjustning Pressure Feedback in Systems with Over-Centre Valves. In Proceedings of BATH/ASME 2016 Symposium on Fluid Power and Motion Control. American Society of Mechanical Engineers. 2016. FPMC2016-1780 https://doi.org/10.1115/FPMC2016-1780