Auto Tuning of PI Controller using Fuzzy Logic for the Spherical Tank System and its Real Time Implementation

Abstract

In this paper, Auto Tuning of PI controller using fuzzy logic is developed to improve the performance of the spherical tank process. A real time implementation of proposed controller for a spherical tank to control liquid level is studied. Control of liquid level in a spherical tank is highly non linear due to variation in the area of cross section of level system with change in shape. System identification of spherical tank system is done using black box model which is identified to be non linear and approximated to be a first order plus dead time model. Here the conventional PI controller parameters are obtained based on Ziegler-Nicholas (ZN) method and its servo & regulatory responses are compared with PI controller tuned by fuzzy logic. The real time implementation of the process is designed and implemented in MATLAB using VMAT-01 Data Acquisition Module. Fuzzy logic is used to tune each parameter of PI controller, fuzzy rules are designed to tune the parameters Kp and Ki of the PI controller, the performance of the spherical tank system has improved significantly compare to conventional PI controller.

Keywords: Fuzzy controller, PI controller, spherical tank, system identification, Fuzzy tuners