A New Scheme of Fault Detection for Linear Discrete Time-Varying Systems

In this note, a new scheme of fault detection (FD) is proposed for linear discrete time-varying (LDTV) systems subject to l(2)-norm bounded unknown inputs. The basic idea is to find an optimal estimation of the l(2)-norm of the unknown inputs including the unknown initial state variables. This leads to a natural design of the FD system with the l(2)-norm boundedness of the unknown inputs as a threshold and the l(2)-norm of the unknown input estimate as the evaluation function. To avoid heavy computational burden, projection technique in Krein space is applied which allows a recursive computation of the evaluation function. It is shown that the achieved FD system satisfies both the worst case and best case sensitivity/robustness ratio criteria and further applications to observer-based FD lead to an alternative design of H-infinity/H-infinity and/or H-/H-infinity fault detection filter.