Actuator and Sensor Fault Detection and Isolation for Uncertain Switched Nonlinear System Based on Sliding Mode Observers

In this paper, we discuss actuator fault and sensor fault detection and isolation (FDI) problems for a class of switched nonlinear systems with external disturbances. First, an augmented descriptor system is constructed where the augmented state vector consists of the original states, the actuator faults and sensor faults. Secondly, a specific transformation, which transforms the descriptor system into a general system, is made and the relationship between the preconditions relative to these two kinds of systems are discussed in detail. Thirdly, based on the equivalent general switching system, a sliding mode observer which is robust to external disturbances and sensitive to both actuator and sensor faults is designed. Furthermore, based on the proposed fault detection method, a fault isolation method which can isolate the actuator faults from sensor faults is developed by using multiple observer design techniques. Finally, a numerical example is given to illustrate the effectiveness of these methods.