Diagnosis of Nonlinear Delay Systems

The general theme of this article concerns the diagnosis of nonlinear delay systems. Parity space and observers approaches are used to generate residuals. To accomplish fault isolation, we use a bank of observers for all possible faulty models. The paper considers constant actuator faults, that is, the outputs of some actuators are stuck at fixed undesirable constant values. The fault isolation strategy is based on combining the conventional observer design techniques with adaptation techniques. Based on the designed observers, a bank of residuals are defined correspondingly. The actuator faults can be isolated if only one residual goes to zero while the others do not. The faulty model with residual approaching zero identifies the faulty actuators. For linear and nonlinear systems with all states available, new sufficient conditions for fault isolation are derived, which require only that the distribution matrices of the actuators are of full column rank.