Contingency management in flexible manufacturing systems using modal state logic

Abstract Flexible manufacturing systems (FMSs), while offering a comprehensive answer to current demand for wide product diversity and short time to market, incur higher probability of functional failures due to the greater complexity of the system. Unless appropriate measures are taken, frequent failures will not only interrupt the operations of the system but also expose operating personnel to greater risks. Incorporating an appropriate contingency management capability in FMSs will enable the system to automatically recover from a failure and continue operating. Modal state logic provides a model-based control and monitoring methodology to trap and locate faults as well as to diagnose their causes. Modal state logic combines the notions of necessity and possibility from modal logic while operating within the finite state automata formalism. The framework for using modal state logic as a strategy in contingency management in FMSs is developed. This is considered to be a robust strategy as it is a nonprocedural approach that is not limited to what the controller designer predicts concerning system unreliability prior to system operations.