A geometric approach to nonlinear fault detection and isolation

We present in this paper a differential-geometric approach to the problem o f fault detection and isolation for nonlinear systems. A necessary conditio n for the problem to be solvable is derived in terms of an unobservability distribution, which is computable by means of suitable algorithms. The exis tence and regularity of such a distribution implies the existence of change s of coordinates in the state and in the output space which induce an "obse rvable" quotient subsystem unaffected by all fault signals but one, For thi s subsystem, a fault detection filter is designed.