Implementation of Simple Fuzzy PI Controller for Liquid Level Cascade Control

This paper presents simplest fuzzy logic controller (SFLC) PLC's based implementation applied to the cascade control strategy.Level and flow control loops are important and widely used in the oil and manufacturing industries to ensure a quality product.The control is used to maintain the level of the liquid in the tank at the desired value by manipulating the liquid in the reservoir.Two fuzzy sets on each input variable, five fuzzy sets on the output variable, five linear control rules, algebraic product bounded AND/OR operator, Larsen product inference and Centre of Sums (CoS) defuzzification are the components of this simplest nonlinear fuzzy controller to be implemented.The proposed work deals with the real implementation of a simplest fuzzy logic cascade control strategy designed on SIMATIC S7-300 Plc based on ladder diagram (LD) programming.In this paper, we have presented the results of the experimental tests of the conventional PI control strategy as well as the simplest fuzzy PI implementation applied to a PUL-2/EV cascade control device.Experimental results using this simplest fuzzy PI controller with the setpoint error shown that the setpoint tracking rise time can be reduced by 30% and the disturbance rejection time is decreased at 7sec compared to the conventional PID-PLC based controller, and concluded by stressing the importance of this new controller implementation.