Application of passivity and cascade structure to robust control against loss of actuator effectiveness

In this paper the problem studied is passive fault tolerant control with respect to loss of actuator effectiveness, for nonlinear models. The main idea of the work is the formulation of the faulty models as cascade systems of the healthy models with the fault models. Based on this simple formulation, passivity theory is used to ensure the stability of the faulty system. We also study the problem of input saturation. The type of faults studied here are constant as well as time-varying faults. The validity of the proposed controllers is shown on several numerical examples.