Design, Analysis and Performance Evaluation of Fractional Order Proportional Integral for Three Interacting Tank Process in Frequency Domain considered as Third Order System

Conventional Integer order Proportional Integral Derivative (IOPID) are the workhorse for the control of almost 90% of the Industrial processes due to its structural simplicity. With the application of fractional calculus in the field of control engineering, Fractional Order (FO) PID controllers are gaining popularity since it requires a slight modification of the integer order PID controller. Tuning of the Integer Order PID controller parameters are by well known techniques like Ziegler Nichols method, Cohen Coon Method, etc mostly time domain based and few frequency techniques are also available. In the present research work, an attempt has been made to tune the FOPI controller using Frequency domain specifications. Frequency domain specifications considered for the design includes the Phase Margin specification, Gain crossover frequency specification and robustness to gain variations. The proposed control schemes are applied to three interacting tank process represented as third order system and verified under servo, regulatory, servo-regulatory response and robustness conditions. Comparison of the time domain performance indices are performed to guarantee the superiority of the proposed scheme.