FDI filter design for decoupling of actuator and sensor faults under disturbance/noise conditions

Fault Detection and Isolation (FDI) filters are very important for guaranteeing the safety and reliability of realistic active control systems, such as those in actuators and sensors. FDI filters based on the sliding mode observer provide desirable performances for the detection of faults, but they do not include sufficient disturbance rejection performance. In general, the required capabilities of FDI filters are 1) sensitivity to occurring faults and 2) robustness against disturbances. This paper proposes an FDI filter design that decouples actuator faults and sensor faults by using the sliding mode observer as well as the disturbance observer. Accurate fault estimation performances by the proposed method for actuator faults and/or sensor faults under input disturbances and sensor noises are verified in applied conditions.