A pragmatic approach to fault diagnosis in hydraulic circuits for automated machining: A case study

The paper deals with the problem of fault detection and isolation in machining centers, which are the basis of FMS’. The problem is of paramount importance since an effective diagnostic system can lead to a significant increase in the autonomy of an automated system. The paper considers a special case study: an hydraulic circuit which blocks and unblocks the pallet on the rotary table in a machining centre. On the one hand, a practical approach is to insert suitable error handling functions inside the control model. This is extremely easy and efficient to discover non-nominal behaviors, but it is useless to identify the root causes of such behaviors (faults). On the other hand, theoretical approaches are able to automatically synthesize an observer that is able to detect a fault when diagnosability conditions apply. Unfortunately, the diagnosability conditions do not always apply in real industrial applications, where some diagnostics analysis should be done anyway. Dually, when applicable, diagnosability may depend upon other rare events or even on some other faults, which may impair its practical applicability. The paper investigates the pragmatic use of known theoretical techniques with the special aim at providing the human operator with all the possible information in real applications.