Robust stabilisation of coprime factor plant description subject to plant perturbations

Abstract

This paper presents a new procedure for the synthesis of linear multivariable system subjected to plant perturbations and external disturbances. Coprime factorisation approach is used to model the plant perturbations. External disturbances is treated as exogenous system whose unstable modes are assumed to be disjoint from the system zeros. A stable desired closed loop transfer matrix is obtained which can be expressed as the product of an open loop transfer matrix and any proper rational transfer matrix. Internal model principle is employed to realise the closed loop transfer matrix which simultaneously ensures: (1) stability robustness in the presence of plant perturbations, (2) decoupling, (3) complete and arbitrary closed loop pole placement, (4) internal stability and (5) disturbance rejection. The compensation scheme is presented in the frequency domain. This is compared with H-infinity control technique and the simulation result shows better robust performance for the frequency domain method.