Timed-automata based method for synthesizing diagnostic tests in batch processes

• A standardized methodology is proposed to construct timed automata.
• A systematic procedure is developed to enumerate all observable event traces.
• A generic synthesis approach is designed to build the test plan of any undiagnosable trace.
• This method is capable of distinguishing faults of the same type but with different intensities.

Hardware failures are inevitable but random events in the useful life of any batch chemical plant. If these incidents are not efficiently diagnosed, the consequences can be very serious. In general, two design measures may be implemented offline to enhance the overall diagnostic performance, i.e., installing sensors and/or stipulating test plans for online implementations. Since the former has already been studied extensively, the present study focuses only upon the latter. In a recent work, Kang and Chang (2014) proposed an effective method to conjecture diagnostic tests using the untimed automata. However, due to a lack of time-tracking mechanisms, the failure-induced behaviours cannot always be characterized adequately with such models. A systematic procedure-synthesis strategy is therefore developed in the present study by making use of the timed automata and the model-checking capabilities of existing software, e.g., UPPAAL ( Behrmann et al., 2006). All component models are first constructed, and all possible fault propagation scenarios and their observable event traces (OETs) are next enumerated exhaustively. The optimal test plan for every OET can then be established by generating the supervisory controller to improve diagnostic resolution. Extensive case studies have also been carried out in this work to confirm the validity and effectiveness of the proposed approach.