Abstract

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 (K_P and K_I) 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 K_P and K_I, for each ?, are taken. Among these values, the best fit of K_{P average} and K_{I 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.

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