F. Previdi et T. Parisini, Model-free fault detection: a spectral estimation approach based on coherency functions, INT J CONTR, 74(11), 2001, pp. 1107-1117
This paper presents a model-free fault detection technique based on the use
of a specific spectral analysis tool, namely, squared coherency functions.
The fault-free dynamic behaviour of the plant considered is described by a
stochastic linear state equation, where the stochastic part is due to unpr
edictable external disturbances. A fault is assumed to be a nonlinear dynam
ic perturbation of the linear plant dynamics. The detection of the fault is
achieved by on-line monitoring the estimates of a squared coherency functi
on that is sensitive to the occurrences of non-linear events affecting the
plant dynamics. A theoretical analysis of the fault-detectability issue is
made and an original algorithm for a low-bias estimation of the squared coh
erency function is exploited to minimize the false-alarm rate. Finally, exp
erimental results obtained by using real data concerning the three-tank ben
chmark problem are reported, showing the effectiveness of the proposed meth
odology.