PMC Model Research Articles

A New Measure for Hybrid Fault Diagnosability

Using the PMC model of a multiprocessor system, a new, general quality of hybrid fitult (combinations of hard anid soft failing units) diagnosability is characterized which encompasses previously known results as well as provides a major extension. This new diagnosability, called t/ts/τ-diagnosability, serves as a measure of the extent to which collections of test results, called syndromes, contain information relative to faulty unit identification for various testing assignments. By analyzing a system's test assignment over tahges of the parameter values t, ts, and τ, the spectrum of diagnosis quality achievable in that system can be established. Fundamental interrelationships among these parameters are developed. Optimal designs of t/ts/τ-diagnosable systems are presented. The main result of this correspondence can be viewed as a master fault diagnosability characterization which from the perspective of usefulness of the syndrome space for correct diagnosis both unifies and expands the domain of hybrid fault diagnosabilities.

Diagnosis Without Repair for Hybrid Fault Situations

For a new class of fault situations called hybrid fault situations, we consider the fault diagnosing capabilities of systems which for testing/monitoring purposes can be viewed as being composed of independent units. The classical Preparata, Metze, and Chien model (PMC model) is used to specify the various testing assignments among the units. Hybrid fault situations are described as explicitly bounded combinations of permanently and intermittently faulty units. This new concept of a hybrid fault situation includes as special cases the all permanent fault case and the unrestricted intermittent fault case which have both been previously considered with PMC models. A general characterization of the so-called connection assignment of a PMC model is established for a diagnosing capability which is referred to as hybrid fault diagnosability without repair. This diagnosing capability is compatible with the well-known permanent fault diagnosability without repair concept, and the quality of this diagnosing capability is shown to be correct, but sometimes an incomplete diagnosis where the incompleteness is solely a consequence of intermittently faulty units. The characterization for hybrid fault diagnosability without repair is seen to encompass as extreme cases the previously known special characterizations for permanent and unrestricted intermittent diagnosability without repair. Fundamental interrelationships are determined among parameter bounds used to describe the hybrid fault cases which can be diagnosed for a given PMC model.