Diagnosis as a Variable Assignment Problem: a Case Study in Space Robot Fault Diagnosis

In the present paper we introduce the notion of Variable Assignment Problem VAP as an ab stract framework for characterizing diagnosis Components of the system to be diagnosed are put in correspondence with variables behav ioral modes of the components are the values of the variables and a diagnosis is a variable assignment which explains the observations of the diagnostic problem by considering the con straints put by the domain theory In order to have a concise representation of diagnoses and to reduce the search space we introduce the notion of scenario for representing a set of diagnoses The paper discusses the denition of preference criteria for ranking solutions and their use for guiding the heuristic search for di agnoses Experimental data are reported for the evaluation of such a heuristic search on a realworld diagnostic problem concerning the identication of faults in a space robot arm in this domain where a high number of diagnoses may be possible our approach allows one to get a concise representation of the large number of solutions and to dene e ective diagnostic strategies able to provide relevant information about fault localization and identication