EFFECT OF CONTROLLER IN REDUCING STEADY-STATE ERROR DUE TO FLOW AND FORCE DISTURBANCES IN THE ELECTROHYDRAULIC ACTUATOR SYSTEM
Keywords:
actuator, electrohydraulic, hydrostatic, micro-precision, disturbance rejectionAbstract
This paper pertains to the nonlinear control of a high-precision hydrostatic actuation system known as the Electro-Hydraulic Actuator (EHA). It describes the action of the controller in reducing the steady state error resulting from flow and force disturbances. The EHA uses inner-loop pump velocity feedback to achieve an unprecedented level of accuracy for a hydrostatic system. A published mathematical model of the EHA is reviewed and expanded to produce an equation that predicts the response of the EHA to both desired inputs as well as flow and force disturbances. This equation suggests that the use of a proportional outer-loop controller should result in steady-state error as a result of these disturbances, but that a PI outer-loop controller should eliminate the steady-state error. Experimental results from a prototype of the EHA demonstrate that due to the nonlinear friction present in the actuator, the use of a conventional proportional or PI controller is not sufficient to effectively deal with these disturbances. However, a nonlinear proportional outer-loop controller does result in a substantial performance improvement in regards to disturbance rejection for positional accuracy. Experiments conducted on the prototype using the nonlinear controller reveal that it is capable of a positional accuracy of 1 μm for a load of 20 kg.
Downloads
References
Arnautovic, S. 1993. Electrohydraulic Actuator.
Technical Report, University of Toronto, Canada.
Chinniah, Y. 2004. Fault Detection in the Electrohydraulic
Actuator Using Extended Kalman Filter.
Phd thesis, University of Saskatchewan, Canada.
Desai, J. and Bobrow, J. 1989. Modelling and Analysis
of a High Torque Hydrostatic Actuator for Robotic
Applications. Exp. Robotics.
Habibi, S. and Goldenberg, A. 1999. Design and
Analysis of a Symmetrical Linear Actuator for Hydraulic
Systems. Transactions of the CSME, Vol.
, No. 3 & 4, pp. 377-397.
Habibi, S. and Goldenburg, A. 2000. Design of a New
High Performance Electrohydraulic Actuator.
IEEE/ASME Transactions on Mechatronics, Vol. 5,
No. 2.
Habibi, S., Pastrakuljic, V. and Goldenburg, A.
Model Identification and Analysis of a High
Performance Hydrostatic Actuation System. SAE
paper 2000-01-2619, 2000 SAE International Off-
Highway & Powerplant Congress and Exposition.
Habibi, S. and Singh, G. 2000. Derivation of Design
Requirements for Optimization of a High Performance
Hydrostatic Actuation System. International
Journal of Fluid Power, Vol. 1, No. 2.
Manring, N. and Lueke, G. 1998. Modelling and Designing
a Hydrostatic Transmission with a Fixed-
Displacement Motor. Journal of Dyn. Sys. Meas. &
Cont, Vol. 120, pp. 45-50.
Merritt, H. 1967. Hydraulic Control Systems. John
Wiley & Sons.
Ogata, K. 2002. Modern Control Engineering, 4thEd.
Prentice Hall.
Watton, J. 1989. Fluid Power Systems. Prentice Hall.