Operational fault diagnosis of manufacturing systems

Among all kinds of possible faults in a manufacturing system, operational faults occur most often (about 70%). Efficient diagnosis of these faults is critical for improving the availability and productivity of the manufacturing system. This paper presents a hierarchical diagnosis model based on fault tree analysis (FTA) and two other diagnosis models, respectively, based on the logic and sequential control of manufacturing systems which are usually controlled by a programmable logical controller (PLC). With these models working together, the operational faults of a manufacturing system can be diagnosed completely. The models have been successfully applied to a PLC-controlled flexible manufacturing system (FMS) and have achieved good results.