Design of a soft sensor for the oscillatory failure detection in the flight control system of a civil aircraft

The objective of this study is the detection of oscillatory failure (unknown and bounded) that may affect the control system of a control surface (CS) of a civil aircraft. Beside the fact that the failure may result in additional loads on the aircraft structure, it can excite a resonance phenomenon. Early and robust detection of this type of failure is therefore a need for structural design objectives as well as for the controllability of the aircraft. From an analytical model of the actuator and its control loop, a so-called failure-free model translating the behavior of the system in the absence of failure is developed, as well as failure models corresponding to system behaviors in the occurrence of different types of failure. This allows generating residual signals for failure detection.