EQUIVALENT TIME-INVARIANT MODELLING OF ELECTROHYDRAULIC ACTUATORS WITH APPLICATION TO ROBUST CONTROL SYNTHESIS

Authors

  • Mark Karpenko Fluid Power Research Laboratory, Department of Mechanical and Manufacturing Engineering, University of Manitoba, Winnipeg, Manitoba, R3T 5V6
  • Nariman Sepehri Fluid Power Research Laboratory, Department of Mechanical and Manufacturing Engineering, University of Manitoba, Winnipeg, Manitoba, R3T 5V6

Keywords:

electrohydraulic actuators, robust control synthesis, equivalent linear time-invariant modelling, frequency response functions, Fourier transformation

Abstract

An important aspect of robust control development around hydraulic actuators is establishing a set of equivalent linear time-invariant (LTI) models that describe the dynamics of the system over the desired envelope of operation. The nonlinearities inherent in the hydraulic functions must be recast into an equivalent linear form in order to make the robust control problem amenable to solution by linear techniques. This paper develops a simple model-based approach for evaluating equivalent LTI frequency response functions of an electrohydraulic actuator by Fourier transformation of acceptable actuator input-output data. The efficacy of the numerical procedure is compared with two other available methods, namely small-signal analysis and Golubev’s least-squares approach. It is shown that the proposed approach can describe large signal effects and at the same time properly characterize the features of the hydraulic actuator frequency response that are important for robust control design, without the need for a priori information about the asymptotic behaviour or structure of the equivalent LTI transfer function. The applicability of the proposed numerical technique towards development of practical controllers for fluid power systems is demonstrated by the results of a typical robust control design example for an experimental electrohydraulic positioning system.

Downloads

Download data is not yet available.

Author Biographies

Mark Karpenko, Fluid Power Research Laboratory, Department of Mechanical and Manufacturing Engineering, University of Manitoba, Winnipeg, Manitoba, R3T 5V6

Mark Karpenko is currently completing his Ph.D. degree in Mechanical Engineering at the University of Manitoba, and holds B.Sc. and M.Sc. degrees from the same University. His research interests include robust control of fluid power systems and, in particular, fault tolerant control. He has published several papers on QFT control system design for hydraulic and pneumatic servos.

Nariman Sepehri, Fluid Power Research Laboratory, Department of Mechanical and Manufacturing Engineering, University of Manitoba, Winnipeg, Manitoba, R3T 5V6

Nariman Sepehri is a professor with the Department of Mechanical and Manufacturing Engineering, at the University of Manitoba. He received M.Sc. and Ph.D. both from the University of British Columbia, Canada. His areas of interest include telerobotics applied to hydraulic manipulators and fluid power fault tolerant control and diagnosis systems.

References

Bailey, D. H. and Swarztrauber, P. N. 1994. A fast

method for the numerical evaluation of continuous

Fourier and Laplace transforms. SIAM Journal on

Scientific Computing, Vol. 15, pp. 1105-1110.

Edge, K. A. 1997. The control of fluid power systems

– responding to the challenges. Proceedings of the

Institution of Mechanical Engineers Part I: Journal

of Systems and Control Engineering, Vol. 211, pp.

-110.

Filon, L. N. G. 1929. On a quadrature formula for

trigonometric integrals. Proceedings of the Royal

Society of Edinburgh, Vol. 49, pp. 38-47.

Finney, J. M., de Pennington, A., Bloor, M. S. and

Gill, G. S. 1985. A pole-assignment controller for

an electrohydraulic cylinder drive. ASME Journal of

Dynamic Systems, Measurement, and Control, Vol.

, pp. 145-150.

Golubev, B. and Horowitz, I. 1982. Plant rational

transfer approximation from input-output data. International

Journal of Control, Vol. 36, pp. 711-

Horowitz, I. 1981. Improvement in quantitative

nonlinear feedback design by cancellation. International

Journal of Control, Vol. 34, pp. 547-560.

Horowitz, I. M. 1993. Quantitative Feedback Design

Theory - QFT, Vol. 1. QFT Publications, Boulder,

CO.

Karpenko, M. and Sepehri, N. 2003. Robust position

control of an electrohydraulic actuator with a faulty

actuator piston seal. ASME Journal of Dynamic Systems,

Measurement, and Control, Vol. 125, pp. 413-

Kim, M. Y. and Lee, C.-O. 2006. An experimental

study on the optimization of controller gains for an

electro-hydraulic servo system using evolution

strategies. Control Engineering Practice, Vol. 14,

pp. 137-147.

Merritt, H. E. 1967. Hydraulic Control Systems.

Wiley, New York.

Mopsik, F. I. 1985. The transformation of time-domain

relaxation data into the frequency domain. IEEE

Transactions on Electrical Insulation, Vol. 20, pp.

-964.

Nikiforuk, P. N. and Westlund, D. R. 1965. The large

signal response of a loaded high-pressure hydraulic

servomechanism. Proceedings of the Institution of

Mechanical Engineers, Vol. 180, pp. 757-775.

Niksefat, N., Sepehri, N. and Wu, Q. 2007. Design

and experimental evaluation of a QFT contact task

controller for electro-hydraulic actuators. International

Journal of Robust and Nonlinear Control,

Vol. 17, pp. 225-250.Piche, R., Pohjolainen, S. and Virvalo, T. 1991. Design

of robust controllers for position servos using

the H∞ theory. Proceedings of the Institution of Mechanical

Engineers Part I: Journal of Systems and

Control Engineering, Vol. 205, pp. 299-306.

Plummer, A. R. and Vaughan, N. D. (1996) Robust

adaptive control for hydraulic servosystems. ASME

Journal of Dynamic Systems, Measurement, and

Control, Vol. 118, pp. 237-244.

Sekhavat, P., Wu, Q., Wu and Sepehri, N. 2005.

Impact control in hydraulic actuators. ASME Journal

of Dynamic Systems, Measurement, and Control,

Vol. 127, pp. 197-205.

Stahl, H. 1984. Transfer function synthesis using frequency

response data. International Journal of

Control, Vol. 39, pp. 541-550.

‘t Mannetje, J. J. 1973. Transfer-function identification

using a complex curve-fitting technique. Journal

of Mechanical Engineering Science, Vol. 15,

pp. 339-345.

Whitfield, A. H. and Messali, N. 1987. Integralequation

approach to system identification. International

Journal of Control, Vol. 45, pp. 1431-1445.

Wu, D., Burton, R., Schoenau, G. and Bitner, D.

Establishing operating points for a linearized

model of a load sensing system. International Journal

of Fluid Power, Vol. 3, pp. 47-54.

Downloads

Published

2008-11-01

Issue

Section

Original Article

Most read articles by the same author(s)