Fuzzy logic based self tuning of PI controller for a non linear spherical tank system

Tuning the parameters of a controller is very important in system performance. Ziegler and Nichols tuning method is simple and cannot guarantee to be effective always. This paper investigates the design of fuzzy logic based self tuning Proportional Integral (PI) controller on a First order Plus Dead Time (FOPDT) non linear spherical tank system using block box modelling. The real time PI controller was designed for a liquid level process, the servo and regulatory responses of the controller were obtained. The simulation results of conventional PI controller, Internal Model Control (IMC) based PI controller and Self tuning Fuzzy PI controller is obtained using MATLAB. From the simulation it is clear that there is substantial improvement in the Self tuning Fuzzy PI controller in terms of peak overshoot, settling time, peak time, rise time, Integral Square Error (ISE) and Integral Absolute Error (IAE).