A two-phase approach for the design of two-degree-of-freedom of robust controller for higher order interval system

Abstract

This paper proposes a novel method for the design of the robust controller to retain both the robust stability and performance of the higher order interval system via reduced order model using the differential evolution (DE) algorithm. A stable reduced interval model is generated from a higher order interval system using DE in order to minimise the cost and reduce the complexity of the system. The reduced order interval numerator and denominator polynomials are determined by minimising the integral squared error (ISE) using the DE. From the reduced order interval model, a robust PI controller is designed based on the new stability conditions of interval system. The designed robust controller from the reduced order interval model will be attributed to the higher order interval system. The designed PI controller from the proposed method not only stabilises the reduced order model, but also stabilises the original higher order system. Finally, with the help of frequency domain method a pre-filter is constructed to improve the performance of interval system. The viability of the proposed methodology is illustrated through a numerical example for its successful implementation.