A Linearized Electrohydraulic Servovalve Model for Valve Dynamics Sensitivity Analysis and Control System Design

Abstract

This paper presents the derivation of a linearized model for flapper-nozzle type two-stage electrohydraulic servovalves from the nonlinear state equations. The coefficients of the linearized model are derived in terms of the valve physical parameters and fluid properties explicitly, and are useful for valve design and sensitivity analysis. When using this model structure to fit experimental frequency response data, the results render closer agreement than when using existing low order linear models. This model also suggests important servovalve dynamic properties such as the nonminimum phase zero and the transfer function relative degree, and how they relate to the valve component arrangement. Because of the small modeling errors over a wide frequency range, a high bandwidth control system can be designed. A robust performance controller is designed and implemented to demonstrate the utility of the model. [S0022-0434(00)03401-8]