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An active suspension system is inherently nonlinear due to the nonlinear electrohydraulic actuatoudynamics. In this thesis, we propose a fuzzy auto-tuning PD control and an adaptive fuzzy sliding mode control for active suspension systems, and compare theri performance with backstepping control proposed by Lin and Kanellakopoulos〔11〕. The Taguchi method is used for the optimal selection of the controller parameters. The fuzzy auto-tuning PD controller is composed of a PD control with gains auto-tuned using a fuzzy system and nonlinear controls based on the electrohydraulic actuatou nonlinear model. The design methodology is similar to the backstepping approach based on the cascade structrue of the active suspension systems, however, it is much more simpler. As for the adaptive fuzzy sliding mode control, the traditional sliding mode control, backstepping control and adaptive fuzzy systems desing methodology are integrated, and the Lyapunov theroy is used to construct and analyze the stable adsptive system. The centers of the consequents of an adaptive fuzzy system are on-line adapted to update the gain of the switching part of the sliding control to compensate for the uncertainty. Computer simulations show that the ability of the backstepping control to reject the road disturbance is better than the other two strategies, but its respose speed is rather slow, and its robustness is very poor. The suggested adaptive fuzzy sliding mode control can work well and have good robustness, Form implementation point of view, the fuzzy self-tuning PD control is more practical than the other twos since iots control performance is good and the required computation is much lower.
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