Robust fault-tolerant controller design

A robust fault-tolerant control scheme using an accurately-identified model of a plant operating in closed-loop is proposed. Parametric uncertainties are restricted to the subsystems which are likely to vary and do not apply to the entire system. A good accuracy of the parameter estimation scheme is obtained by ensuring that the identified model set includes the true system model, and by using a two-stage closed - loop identification. Both the primary goal of this paper, namely high - performance controller design, and the secondary goal of performance, stability and condition monitoring are achieved. The parametric uncertainty associated with the identified model is modeled as perturbations in the numerator and denominator polynomials to develop robust controllers using a mixed-sensitivity H_∞ controller. The proposed scheme is extensively tested through simulations and on a physical laboratory- scale magnetic levitation system.