Critical thinking is essential in designing complex behavioral systems. The most difficult systems to design are those that require the system to operate through failure scenarios - design of a fail active system is fundamentally different than design of a fail safe system. In these cases, real-time state knowledge and fault isolation are critical elements of the overall fault design. Incorrect "assumptions" of the current state of the system or the root cause of the failure based on known fault signatures alone can produce catastrophic failures in real world situations. The real world has a disconcerting habit of failing in ways designers never dream of. A discussion of available techniques for modeling and estimating state and the importance of design flexibility will be discussed.
Document date May 3, 2010.