Nonlinear Control Of Electrohydraulic Servo System

This paper presents a linear model of electrohydraulic servo-system and designs its static parameter as a sample of rudder loading system of one model airplane. The linear model is used to the system that has relative low frequency and relative small varying parameter and outer disturb. But electrohydraulic servo-system is often required to have the ability to trace any curve function and endure relative big outer disturb, so the dot of balance change greatly during working, that make linear model is not successful. To solve this problem, a nonlinear model of electrohydraulic servo-system is established and is linearizaed accurately under the large scale using nonlinear control theory. The method make nonlinear system to be transformed a linear system which can be controlled complete through searching a nonlinear state feedback, so we can analyze the system using the mature theory of linear system. Though simulation, it is made clear that controlled by the nonlinear controller the system has good dynamic performance and good robustness when the model and parameter of the system vary.