Fault tolerant control allocation for fractional-order systems

In this paper a new fault tolerant control strategy for commensurate Fractional Order time invariant systems is proposed, where only measured system outputs are supposed to be available. The output-feedback Fault Tolerant Control/Control Allocation procedure introduced by Edwards et al. [18] is extended to commensurate Fractional-Order uncertain systems. Both the parametric uncertainty of the system matrix and an extra disturbance term are considered. The policy ensures closed-loop stability throughout the entire closed-loop response of the system even in the presence of actuator reduction in the effectiveness. This is accomplished by incorporating ideas of Fractional Sliding Mode Control, Unknown Input Observers and a fixed Control Allocation method. A convex representation of the problem is created in order to get the controller and observer gains.