An FDI approach for aircraft actuator lock-in-place fault

In this paper, an adaptive observer approach is developed to detect and isolate aircraft actuator faults. Particularly, the fault of actuator locked in place is considered. In a multiple-model scheme, a bank of parallel observers are constructed, each of which is based on a model that describes the system in the presence of a particular actuator fault. The observers are designed by eigenstructure assignment based on a modified form of the standard observer to generate fault-dependant residual signals, such that when a model matches the system, the residual signal will be zero. Otherwise, the residual will be non-zero and governed uniquely by the faulty signal. For locked actuators in which the locked position is additional unknown, we develop an adaptive scheme to estimate the unknown parameter. We prove that the proposed adaptive algorithm guarantees the convergence of residual signal when a model matches the plant. By further designing a model-matching index, the fault can be isolated accurately.