Electro-hydraulic Position Servo Systems Using Fuzzy Control Study

With the development of electro-hydraulic servo technology and the wide use in more areas, the higher capability of electro-hydraulic servo system is required more and more. The control strategy of electro-hydraulic servo system is one of the most important factors that affect the control capability. Basing on improving the control precision of hydraulic machine, the author successfully applies Fuzzy control to the electro-hydraulic position servo system and has a conclusion that the adaptive property of Fuzzy control is better than PID control's. Fuzzy control is more adapted to the nonlinear and time-variable system such as hydraulic system.The article has improved the existed fluid power system of hydraulic machine, and at the same time, it designs the electro-hydraulic position servo system. On the basis of fluid dynamics and classical control theory, the mathematical model of asymmetry cylinder controlled by symmetry four-way valve is set up. Through analyzing the dynamic and static characteristics, the author regulates system by using PID control strategy and uses Cut & Try method to adjust the parameters of PID controller. Through the simulation and experiment, we can realize it's difficult to adjust the parameters of PID controller, the self-adaptive property of PID controller is not good too.By researching on Fuzzy control theory, the article designs the conventional Fuzzy eontroller. Although the dynamic response performance is good, its steady-state precision is bad. In order to improve those defects, the author analyses the cause, designs several Fuzzy controllers according to PID control from different sides and achieves their control arithmetic by the computer. Fuzzy PID controller minimizes steady-state error by joining the intelligent integral. Fuzzy-PID dual-mode Fuzzy controller can automatically change control mode by a threshold between the Fuzzy control with PID control, so it possesses the advantages of those two control modes. Self-tuning factor Fuzzy controller can automatically adjust the control rulers of Fuzzy controller on-line in real time, so it improves the self-leaning function of the controller. Self-adaptive controller can adjust and optimize the PID control parameters on-line by using expert system, it enhances the control precision and the function of self-adaptive and self-learning.The mathematics expression of Fuzzy controller can be adopted toward the understanding of the substance of Fuzzy logic illation, and those programs such as parameter adjustment of PID controller, the arithmetic of Fuzzy control and simulation processes, can be applied in scientific research and production in the practice.