Model identification of the electrohydraulic actuator for Small signal inputs

A prototype of a high-precision hydrostatic actuation system, referred to as the ElectroHydraulic Actuator (EH A), has demonstrated an unprecedented level of accuracy for large load manipulation. This prototype has been able to move an inertial load of 20 Kg with an accuracy of 1 micron, and is currently being modified for sub-micron precision operation. The aim of this paper is to characterize the EHA using an empirical model for operation in the micron and sub-micron range. Previous experimental studies on the EHA have indicated that the system is nonlinear, but can be characterized as piecewise linear. The natural frequency and damping ratio of the EHA varies in a piecewise manner depending on its operating range, which is largely determined by the magnitude of the input signal. System characterization at input levels corresponding to micro-precision movements of the load has not been previously reported and is investigated in this paper. Piecewise linear empirical models are identified in view of implementing a nonlinear fuzzy control strategy. © With The Centre for Power Transmission and Motion Control.