Design And Real Time Implementation Of Fractional Order Proportional-Integral Controller ( Pi ? ) In A Liquid Level System

This research article deals with the design and real time implementation of a fractional order Proportional-Integral controller (PI?) for a Liquid Level System (LLS). The system is approximated as a First Order Plus Time Delay (FOPTD) model. The equivalent transfer function of this system in polynomial format is considered here for controller design. Expressions for controller parameters (KP and KI) in terms of frequency (?) and fractional order (?) are derived from the Fractional Order Characteristic Polynomial (FOCP) of the closed loop system. The global stability region based on K P and K I for each ? is constructed. Average values of KP and KI, for each ?, are taken. Among these values, the best fit of KP average and KI average and corresponding ? are identified by means of optimization techniques. The real time implementation of PI? controller with the identified controller settings in LLS is done. The PI? controller performances are analyzed in terms of ISE and IAE. A comparison of this control strategy with other conventional based controller techniques is made. PI? controller outperforms the conventional PI controllers. In addition the load disturbance studies are also carried out and it justifies the supremacy of PI? controller.