Fault diagnosis in closed control loops via frequency domain approach

This paper deals with the problem of designing detection filters for FD1 in closed control loops. The methodology presented in here makes use of model-based approaches applied to linear systems. The residual generator proposed in the following is derived from the transfer functions of the system in open and closed loop, and is designed to be sensitive to the different types of faults which can occur on the plant (e.g., sensor, actuator, process). Another topic of interest is that of the robustness of the FD1 systems to different disturbances. The solution proposed here consists in a detection filter which is placed at the output of the residual generator in order to reduce the sensitivity to these disturbances and enhance only the influence of the faults on the residuals. The design procedure of the detection filter is based on the optimization of a performance index expressed in the frequency domain.