DESIGN AND EVALUATION OF AN OPTIMAL FUZZY PID CONTROLLER FOR AN ACTIVE VEHICLE SUSPENSION SYSTEM

The goal of studying the vehicle suspension systems is to reduce the vehicle vibrations which are due to the irregularities of road levels and the fluctuations in the vehicle velocity. These vibrations are transferred to the body and occupants of vehicles through the suspension system. In general, the main function of an active suspension system is to support the vehicle body by reducing the input vibrations and to provide a safe and smooth ride on a bumpy road surface. In this research, a quarter vehicle model has been employed for designing a suspension system. The road level irregularities have been considered as disturbances to this system. The optimal fuzzy PID (OFPD+I) controller has been used to optimize the performance of the suspension system in reducing the adverse effects resulting from road level irregularities, vehicle braking, and moving around the road curves. To verify the efficacy of the optimal fuzzy PID controller, its performance has been evaluated and compared with the performances of three separate controllers (PID, fuzzy, and fuzzy PID) and a system without any controller. The findings indicate the advantage of the optimal fuzzy PID controller over the other systems. Thus, in the integral of the absolute error criterion for the vehicle body velocity and displacement changes, the OFPD+I controller has a superior performance relative to the other systems.