Discrete Nonlinear Reference Models Of AMFC Research On Electrohydraulic Servo System

Electrohydraulic servo control system is regarded as an important component in the electromechanical control system, which has some characteristics of little inertia, big power, fast responding, high accuracy and so on, so it is widely used in the field of industry, national defence, Aero-Space, etc.. Because of electrohydraulic servo system is a complicated structure and multifactor coupling system which is composed of mechanical, electronic and hydraulic components, and the factors of nonlinearity, time varying, uncertainty, etc. are inherent in its. When the system is used in the high frequency response and high accuracy occasion, the factors can make a serious influence on control properties. Therefore, the study of nonlinearity of electrohydraulic servo system possess the practical meanings, it is also a hot subject for research of relevant trade experts and scholars' both at home and abroad.This paper takes aim at the nonlinearity of servo-valve's flow/pressure of electrohydraulic servo system, and have carried on the comparatively deep research on valve-controlled symmetrical cylinder electrohydraulic servo system and valve-controlled asymmetrical cylinder electrohydraulic servo system.1. According to the characteristics of electrohydraulic servo system, this paper analyses the nonlinearity of servo-valve's flow/pressure of valve-controlled symmetrical cylinder system and valve-controlled asymmetrical cylinder system, builds the nonlinear reference models which hold the main nonlinearities of the controlled plants, and has carried on the accurate linearization to the models by using affine transformations and nonlinear state feedback. Then, the nonlinear reference models which have dynamics characteristic of expecting are built by using pole-zero placement after the models are made discrete. So the discrete nonlinear reference models are designed for the controlled plant to follow.2. With the method of designing AMFC system by using hyperstability theory, perfect model following (PMF) conditions are deduced, and the discrete nonlinear reference model AMFC scheme of electrohydraulic servo system is gained. The scheme can achieve state feedback of the controlled plant needed only measuring the output of system.3. This paper carries on the simulation analysis for valve-controlled symmetrical cylinder system and valve-controlled asymmetrical cylinder system by using MATLAB/Simulink. The consequences of simulations in this paper are satisfactory.4. The check experiment of valve-controlled symmetrical cylinder electrohydraulic servo system which is controlled by the discrete nonlinear reference model AMFC scheme has been carried on on the modified electrohydraulic servo actuator laboratory device, and an internet applications which utilizes the AMFC scheme to carry on real-time control has been developed by using Turbo C. According to the result of experimentation, the conclusion is verified, that is, the frequency spectrum of the outputs is composed of the frequency spectrum of the inputs. So the linearization to electrohydraulic servo nonlinear system has been succeeded in achieving by using the discrete nonlinear reference model AMFC scheme, and the effect of the linearization is satisfactory.