Fuzzy-PD controller design with stability equations for electro-hydraulic servo systems

In this paper, the focus is on the system stability information, namely the stable region and stability boundary explored by the use of the parameter plane method, the stability equation method, and the describing function method. A PD controller, under the consideration of stability, is first designed for the electro-hydraulic servo systems subject to nonlinear friction. Then, in accordance with the known data with the use of PD controller, a robust methodology using the fuzzy logic is proposed to have better tracking performance. Finally, the fuzzy-PD controller is used to replace the PD controller.