Comparison of PI controller performances for a Conical Tank process using different tuning methods

Conical Tank is one of the nonlinear processes used in many industries. In this paper various analog PI controllers were designed and analyzed for the conical tank system to maintain the liquid level in tank at the desired value. The level control becomes quite typical due to the nonlinear shape of tank as the rate of rise of water in the narrow part of the tank is high and gets reduce as height increases thus causing non linear rise in level. The time constant and gain varies as a function of level. Conventional PID controllers are widely used in many industrial control systems for several decades. In this paper various tuning strategies like Zeigler Nichols, Cohen-coon, CHR and Kappa-Tau have been applied and their performance indices are compared.