Diagnosis in Automatic Checkout

This paper summarizes several approaches to the problem of isolating faults in a complex system. The formulation of a diagnostic procedure involves 1) logical analysis techniques for the interpretation of results obtained from testing and 2) optimization techniques to insure that procedures employed in performing tests, selecting or sequencing tests, processing data, etc., are as efficient as possible. A procedure developed at Syracuse University, applicable when deterministic tests are used, is described. A model which extends the logical aspects of this procedure to the case when multiple failures can occur is presented. The problem of applying the figure of merit used in the single error case is discussed briefly. It is pointed out that the extended model is capable of handling a more general class of tests than those usually considered. A simple logic circuit is used to illustrate a test which will fail if two particular element failures occur together, but which will not fail if either one of the two failures occurs alone.