Functional Failure Diagnosis Method of Multi-state Manufacturing System Based on Extended Quality State Task Network

The core function of manufacturing system is to produce high quality and reliable products, and the fault diagnosis of running manufacturing system is an important prerequisite to ensure its healthy state. Previous studies mainly focused on physical fault diagnosis of independent production equipment in the manufacturing system, ignoring the dynamic quality state of its operating process. Furthermore, most manufacturers only focus on the dimensional conformance of the product, ignoring the functional fitness of WIP (work-in-process). Therefore, a functional failure diagnosis method for multi-state manufacturing systems based on extended quality state task network (EQSTN) is proposed. First, based on the stream of variation (SoV) theory and from the system engineering viewpoint of the operational principle of the multi-state manufacturing system, the dynamic operational mechanism of the manufacturing system is elaborated, and the connotation of its functional failure is clarified. Second, infant failure rate is used to extend the traditional quality state of QSTN to fitness quality state of products, and an EQSTN is proposed to comprehensively evaluate the functional state of multistate running manufacturing systems by integrating task execution state(T) and machine performance state(S),that is, mission reliablity, and above-mentioned extended quality state(Q),lay the foundation of functional failure diagnosis. Third, a functional fault diagnosis method is proposed based on EQSTN. Finally, taking the engine head as the research object, the effectiveness of the proposed method is verified.