Failure propagation trees for diagnosis in manufacturing systems

The diagnostic step of the error recovery process in manufacturing systems is discussed, and an algorithm for constructing and pruning a failure propagation tree is formalized. The methodology of building of failure propagation tree is proposed. This methodology is based on a hierarchical process plan, a precondition-postcondition model of manufacturing operations, and a classification of the failure reasons. The hierarchical operation model embodies the process plan, and the functional and structural classifications for each failure reason of every operation in the model. Based on the hierarchical operation model, the final failure propagation tree is generated or expanded by linking the operations in the model. The expansion process is accomplished by iteratively applying the expansion rule and priority rule to the operations in the hierarchical operation model