The application of fuzzy control strategy in electro-hydraulic servo system

This paper presents a fuzzy tracking control methodology for electro-hydraulic servo system from the viewpoint of industrial application and implementation. Since the hydraulic control systems always have the high nonlinearity and uncertain dynamics, the simple linear or nonlinear differential equations cannot sufficiently represent corresponding practical system. And many conventional control methods based on mathematical models are limited in their abilities to improve the tracking performance. The solution in this study is to develop a new nonlinear hybrid controller composed of a classical PID controller and a fuzzy controller based on self-adjusting modifying factor, which greatly improves the robustness, the dynamic and static properties of the system. Additionally, the fuzzy switching mode is employed to avoid the undesirable disturbances caused by the switchover between the two control methods. The proposed fuzzy controller shows excellent robustness against variations of system parameters and external disturbances through a series of simulation studies. Finally, by experiments on a practical electro-hydraulic servo test bench, the effectiveness of this control scheme is verified by comparison with the classical PID or fixed fuzzy controller. The research results show that the hybrid fuzzy PID controller has good performance in real time application.