H∞ bounded fault detection filter

A key issue in practical fault detection filter applications is sensitivity to system disturbances and sensor noise, In this paper, a stabilizing fault detection filter gain is found that bounds the H(infinity) norm of the transfer matrix from system disturbances and sensor noise to the residual. For multidimensional faults, a residual direction is identified that enhances the fault signal-to-noise ratio while maintaining the H(infinity) norm bound, By retaining the fault detection filter structure, the practical applicability of the proposed approach is the same as for fault detection filter designs found by conventional eigenvector assignment. In contrast to an unknown input observer approach wherein noise is explicitly decoupled from the fault signal, a noise bounding approach does not impose additional geometric constraints on the filter structure. This allows a given filter to isolate more faults, an important feature because in practical applications low-order filter dynamics are common. Further, the possibility of ill-conditioned filter eigenvectors, occasionally imposed by geometric constraints, may be reduced.