A critique of several failure detection approaches for navigation systems

Additional references relating to the work of J.E. White and J.L. Speyer (ibid., vol.AC-32, p.593-603, July 1987) are reported and commented on. White and Speyer discussed predecessor studies that dealt with failure detection in navigation applications described by stochastic time-invariant linear system with additive Gaussian white process and measurement noises being present, and sought to use Kalman filters tuned in this application context to detect a priori specified failures. It is argued that, since the predecessor work dealt exclusively with time-invariant deterministic systems devoid of noise terms, exclusive use of observers suffice for failure detection in this more benign context