Robust H ∞ /μ Observer-Based Residual Generation for Fault Diagnosis

Abstract

This paper presents a new approach to the design of a robust observer-based residual generation scheme for incipient fault diagnosis. This H ∞ /μ based approach takes account of the disturbance robustness and fault sensitivity simultaneously. Unlike the robust H ∞ /μ estimator which minimises the disturbance effect on the estimation error and subsequently on the diagnostic residual, this new approach maximises the fault effect on the residual by the proper selection of the performance bound and the estimation weighting matrix of the H ∞ robust estimator. Depending on the class of modelling uncertainty considered, one or two Riccati equations are required for the H ∞ estimator design. The H ∞ estimator can be designed to be robust against; disturbance only, disturbance and parameter uncertainty only, and disturbance and a large variety of modelling errors. The μ robust estimator assumes a block diagonal structure for uncertainty and can produce a less conservative design. A 3rd order system has been used to illustrate special design features. The results show that the FDI scheme developed can effectively detect incipient faults even in the presence of disturbances and modelling errors