A Two Phase Approach for Minimal Diagnostic Test Set Generation

We optimize the full-response diagnostic fault dictionary from a given test set. The smallest set of vectors is selected without loss of diagnostic resolution of the given test set. We give an integer linear program (ILP) formulation using a fault diagnostic table. The complexity of the ILP is made manageable by two innovations. First, we define generalized fault independence. This property identifies many fault pairs that are guaranteed to be distinguished, significantly reducing the number of ILP constraints. Second, we propose a two-phase ILP approach. An initial phase, which uses existing procedures, selects a minimal detection test set. In a final phase, additional tests are then selected for the undiagnosed faults using a new diagnostic ILP. The overall minimized test set may be only slightly longer than that obtained from a one-step ILP optimization, but has advantages of significantly reduced computation complexity and reduced test time. Benchmark results show potential for very small diagnostic test sets.