Comparison and application of three integral-improved methods on conventional fuzzy control strategy

This paper presents three integral methods to a fuzzy knowledge-based control system to diminish the steady-state output errors. These three controllers, namely the three-input fuzzy controller, the fuzzy plus integral controller and the fuzzy-PI controller, are described and applied to two systems. One is a zero-type-number first-order system whose input is a step, while the other is a linearized one-type-number fifth-order electrohydraulic servo system whose input is a ramp. The response of these two systems have steady-state errors without integral control. Simulation results show that all these three integral methods can effectively eliminate steady-state errors. The three-input fuzzy controller that produces the least overshoot and the shortest rise time is the best one to produce rapid dynamic response and minimum output errors. Fuzzy-PI controller is the second best controller in producing small output errors.