Sliding mode observers-based fault detection and isolation in flight control systems

The actuator fault detection, isolation and estimation problem for a class of linear systems with unknown disturbance are proposed. To isolate the possible actuator faults, each possibility is related to a faulty model. Then for each possible faulty model, a sliding mode observer (SMO) is designed, and the residuals are defined as the norm of the magnitudes of the output estimation errors resulting from all possible faulty models. It is proved that, for the faulty model corresponding to the faulty actuators, the designed SMO can ensure that the related output estimation error converges to a sufficient small set. It is also shown that, for all other possible faulty models, the related output estimation errors are much larger. The proposed actuator FDI method is tested in a research civil aircraft model (RCAM), and simulation results show that it can isolate various types of actuator faults effectively.