Optimal design of FDI systems via parity space and observer based approaches

Model-based FDI (fault detection and isolation) schemes operate either in the parameter space (identification methods) or in the state space (observer-based or parity space methods). The authors compare the residuals which are generated by the observer-based and the parity space methods, show the link which exists between the two approaches, and give a geometrical interpretation of the relationship between the two projection spaces. The equivalence of the deadbeat observer and the generalized parity space is discussed in this framework. The authors discuss the optimal design of the FDI system according to the selected method. The optimal design of the FDI system with respect to robustness properties is based on orthogonality considerations. Since the projection space of the generalized parity space approach is included in the projection space of the observer-based one, the latter may be more powerful if all its degrees of freedom are actually used