Detection and identification of bias faults in nonlinear system

Although fault detection and identification (FDI) methods for linear systems have been developed extensively, FDI for nonlinear systems still deserves much attention. In order to detect bias type faults, a bias χ² FDI method is proposed here on the basis of the pseudo separated-bias estimation (PSBE) algorithm. Estimates of biases obtained by PSBE are used to construct a statistical variable which obeys χ² distribution in normal operational conditions. As a result, by testing if the constructed variable is χ² distributed at every estimation step, one can detect input-output bias faults quickly. In order to identify where a bias fault occurs, a bias component χ² detection scheme is proposed further. Simulation results of a paper machine illustrate the effectiveness of the method for real-time application