Non-blocking Supervisory Control of Timed Automata using Forcible Events

Paper in proceeding, 2020

Real-valued clocks make the state space of timed automata (TA) infinite. Conventional supervisory control synthesis techniques are only applicable to finite automata (FA). Therefore, to synthesize a supervisor for TA using conventional techniques, an abstraction of TA to FA is required. For many applications, the abstraction of real-time values results in an explosion in the finite state space. This paper presents a supervisory control synthesis technique applied directly to TA without any abstraction. The plant is given as a TA with a set of uncontrollable events and a set of forcible events that may preempt the passage of time. To obtain a non-blocking controlled system, a synthesis algorithm is proposed that delivers a supervisor (also as a TA) avoiding the blocking states. The algorithm works by (iteratively) strengthening the guards of edges labeled by controllable events and invariants of locations where time progress can be preempted by forcible events.