A robust approach to fault tolerant controller design based on GIMC structure for non-minimum phase systems

This paper represents a robust scheme for designing fault tolerant controller (FTC) based on Generalized Internal Model Control structure, and extends it to non-minimum phase LTI systems. In this scheme, first the nominal controller is designed to have a closed-loop stability and acceptable performance, and then by correcting the nominal controller based on the idea of GIMC, a robustification signal is imposed to compensate the actuator faults. The proposed scheme, deals with nonminimum phase systems by utilizing the idea of transmission zero-assignment. It will be shown that the problem of zero-assignment problem for state-accessible systems is equivalent to a pole-placement problem with state feedback on a reduced-order subspace, which always has a solution. The advantages of the proposed control scheme have been verified by the simulation on the quadruple-tank process subjected to the actuator fault.