Fault diagnosis for nonlinear aircraft based on control-induced redundancy

A Fault Detection and Isolation (FDI) method for a generic 3D aircraft is presented. The behavior of the aircraft is described by a nonlinear control-affine model, which is closed-loop controlled by a classical guidance, navigation and control (GNC) algorithm. The proposed FDI procedure exploits the redundancy induced by this control module, along with the accelerations measured by the Inertial Measurement Unit (IMU). Estimates of first-order derivatives of some state variables are thus readily available and allow one to estimate the control inputs as achieved by the actuators. Since the computed control input sent to the actuator is known, it is possible to use the discrepancy between these two elements as a residual indicative of faults. This strategy is successfully applied to the proposed aeronautical benchmark to detect and isolate actuator faults affecting simultaneously flight control surfaces and propulsion.