A HYBRD OF PID AND SELF-TUNING FUZZY PIE) CONTROLLER FOR NON LINEAR SYSTEMS

Abstract

In this thesis, a hybrid of PID and self-tuning fuzzy PID controller is developed to enhance the performance of the magnetic levitation ball system. Since the nonlinear plant is susceptible to unpredictable parameter variations like current & voltage fluctuations due to temperature, noise etc., the PID parameters could not be properly tuned, so it is crucial to naturally tune the PID parameters. In Self-tuning fuzzy PID (STFPID) controller, the tuning of PID parameters is done through fuzzy controller. Now, a hybrid system is developed to exploit the advantages of both PID and STFPID. An algorithm is proposed and applied to magnetic levitation ball system which switches the control from PID controller to STFPID controller as the error changes from positive to negative. Then comparison is done between conventional PID controller, STFPID controller and the hybrid of PID and STFPID controller and the corresponding results are presented and discussed in Chapter-5. Further, the implementation of STFPID controller has also been applied on Ball and Beam System. Due to high non-linearity of the system, transfer function of Ball and beam system is divided into two separate models and STFPID controller is used in the inner loop to stabilize the system and its performance has been studied. Later the system performance is also studied using PID controller and then two performances are compared and it is found that STFPID controller has a better transient response in comparison to PID controller.