Grey Prediction Based Control of a Non-Linear Liquid Level System Using PID Type Fuzzy Controller

Product-sum type fuzzy controllers are known to have similar characteristics with PD type controllers. In the case of type-0 control systems, PID type fuzzy controllers have been proposed in the literature in order to eliminate the steady-state error. However, these control methods, essentially based on conventional PID theory, have no predictive capabilities. This paper proposes a grey prediction based fuzzy PID controller that can overcome the stated shortcoming. A non-linear liquid level system is taken as a test bed. The grey model developed is examined under several different conditions and it is shown that the proposed grey fuzzy PID controller can predict the future output value of the system. The simulation results indicate that the proposed controller has the ability to control the non-linear system accurately with little overshoot with no steady-state error