A fault detection and isolation scheme for nonlinear uncertain discrete-time sytems

This paper presents a fault detection and isolation scheme for abrupt and incipient faults in nonlinear uncertain discrete-time systems. The proposed fault diagnosis architecture consists of the fault detection and approximation estimator and a bank of fault isolation estimators, each corresponding to a particular type of fault. A time-varying threshold that guarantees no false-positive alarms and fault detectability conditions is derived analytically. For the fault isolation scheme, we design adaptive residual thresholds associated with each isolation estimator and obtain sufficient conditions for fault isolability. To illustrate the theoretical results, a simulation example based on a discrete-time version of the three-tank problem is presented.