THE SIMPLEST IDENTIFICATION MODEL OF AN ASYMMETRIC HYDRAULIC SYSTEM

A single-rod cylinder servo system driving a discontinuous load is a 4 th-order nonlinear system. It can be simplified as a time-varying 1st- order system for typical low frequency applications. The time-varying parameters of such a system conceal the discontinuous loading effect, uncertainties and transient behavior of a single-rod cylinder and serv ovalve. To overcome these difficulties, the parameter identification p rocess requires the characteristics of exponential convergence and unb iased parameter estimation. Here, the parameter identification process incorporates the Ist-order ARMAX model with PEDF algorithm. Experimen ts indicate quantatively that this identification process is superior and more adaptive than high-order ARMA models with RLS algorithm.