Development of fuzzy state controller for a hydraulic position servo

By combining control theory and fuzzy set theory, a new kind of state controller is proposed. The ideas of full order feedback and the membership functions, which utilize the experiences of experts, are used in the design of the state controller which we call a fuzzy state controller. Hydraulic position servo with nonsymmetrical cylinder is popularly used in industry. This kind of system is nonlinear in nature and difficult to control. For different ending position, moving direction, strokes, and load the system dynamics is totally different. Once the above mentioned factors of the system are known, it is relatively easy to tune the gains of state controller to obtain good dynamic response. But when the factors change especially the load, which often happens in practice, using the same gains will cause overshoot or even loss of system stability. The fuzzy state controller has been successfully applied to the hydraulic position servo with excellent robustness when the system unknown factors are encountered