Fuzzy control of a hydraulic position servo with unknown load

By combining control theory and fuzzy set theory, a new kind of state controller is obtained. The ideas of full-order feedback and a membership function are used in the design of the state controller, which is called the fuzzy state controller (FSC). The hydraulic position servo (HPS) is nonlinear in nature and difficult to control. Once the load of the system is known, it is relatively easy to tune the gains of the state controller to obtain good dynamic response. But when the load changes, which often happens in practice, using the same gains will cause overshoot or even loss of system stability. Adaptive control is not applicable in this case due to the complexity of the algorithm and the fast response characteristics of the system. The FSC has been successfully applied to the HPS with excellent robustness when the system load is changed