Optimal auxiliary input for fault detection and fault diagnosis

An optimal input design problem in frequency domain is discussed for quick detection of the system fault without affecting the original system in normal mode. The input is designed to enlarge the distance measured by the Kullback discrimination information measure between the system models corresponding to the normal and the fault modes in single fault mode case. The idea is then extended to multiple fault modes case (fault diagnosis problem). In this case, the auxiliary input is designed to maximize the minimum distance among the distances between the normal and several fault modes in order to detect the true fault mode. Numerical simulation results indicate the applicability of the proposed auxiliary input in fault detection and fault diagnosis.