Electro-hydraulic Position Servo System Based On Iterative Learning Control

Electro-hydraulic position servo system is a high-order system with time-varying, serious non-linear and uncertain structure. These characteristics make it difficult to achieve high-precision conventional PID control. At present, the study on reducing the high-order to low-order and linearization system is prevalent. However, the current hydraulic position servo system is gradually developing toward wide-frequency band, high-power, high-accurate, anti-jamming and fast-response characters, and the method with large-distortion and low-accurate exists many shortages in actual engineering appliance. In order to meet the needs of the development of the electro-hydraulic servo system, the iterative-learning controller based on the high-order and nonlinear system is studied in the text.Iterative learning control does not need accurate mathematical model and its algorithm is simple, and makes it to have some advantages in dealing with non-linear system. In theory, the iterative-learning can fully track the designed trajectory with zero error, adapts to controlled object with repeated movement, can directly been studied in time-domain, and can been researched in off-line. In additional, it is able to changes the input parameters of the system instead of algorithmic itself when the system takes place mice-variety or appears disturbance. How to design the rational controller based on iterative learning control theory for the system with high-order and nonlinear is the focus of the article.After a large number of documents is studied, the model of electro-hydraulic system is built, its transfer function and convergent conditions of iterative learning are deduced, its characteristics of time-domain and frequency-domain are analyzed, and the nonlinear of the system and the time-varying characteristics of parameters are discussed in the text. In addition, hydraulic simulation software AMESim is introduced, and is used with Matlab interface to build the semi-physical simulation model of electro-hydraulic servo system. The simulation model of the controller is constituted and researched in Matlab environment when input signals are separately step signal, sine signal and impulse signal. The result demonstrates that the controller basically can fully track the desired orbit with fast response speed, and further, the controller need to be restarted to learn but not to be reset parameters when the desired orbit is changed, in other words, the controller don't need to be resigned only if the controlled object isn't changed even if the desired orbit is altered.