Fault Diagnosis in Non-Stationary Systems via Interval Observers

The paper is devoted to the problem of fault diagnosis in technical systems described by non-stationary linear dynamic equations under unmatched disturbances and measurement noise via interval observers. The problem is to design the observer insensitive to the disturbances and having fewer dimension than that of the original system. Such an observer generates two (upper and lower) residuals such that if zero is between these residuals, then the faults in the system are absent; if zero is out of these residuals, one concludes that a fault has occurred. The interval observer consists of two subsystems: the first one generates the lower residual, the second one the upper residual. The relations describing both subsystems are given. Theoretical results are illustrated by practical example of the electric servoactuator for which the fault diagnosis problem is solved.