Fault isolation for linear non-minimum phase systems using dynamically extended observers

This article is devoted to the design of fault isolation observers (FIOs). Their purpose is to detect and isolate faults occuring in linear systems by means of only a single, specifically parameterized observer. While parameterizations for such observers have been proposed for minimum phase systems, we generalize the existing results to linear systems without such restrictions. To achieve stable fault isolation, we introduce virtual system extensions, which enable stable isolation despite right half-plane zeros. These virtual augmentations are then realized by dynamically extended fault isolation observers (DFIOs). Apart from that, the proposed design allows to isolate both actuator and sensor faults. The applicability of the proposed approach is shown in both simulations and lab experiments with a gantry crane.