ON A GENERALIZED TEST SEQUENCING PROBLEM

Motivated by the need to increase the availability of systems, the primary focus of diagnosis in field maintenance of systems is to identify the faulty modules rather than the individual faults within the modules. In addition, diagnosis is often integrated with two types of repair: Type 1 repair wherein a module is repaired after complete diagnosis, and a Type 2 repair where a module suspected to be faulty is replaced after partial diagnosis. In this note, we consider the problem of constructing optimal and suboptimal test sequences to diagnose faults in such modular systems with Type 1 and Type 2 repair options. Dynamic programming recursion for this generalized test sequencing problem is derived, and lower bounds on the optimal cost-to-go based on information theory are derived. These bounds ensure that an optimal test algorithm is found by AND/OR graph heuristic search procedures. It is illustrated how Type 2 repair can be profitably combined with diagnosis to reduce the expected test time.