Timed transition automata and their ladder logic implementation

In this paper, a simplified version of timed automata, called timed transition automata (TTA), is proposed. TTA are an extension of untimed automata and are obtained by assigning integer time delay values to events. The proposed TTA are very useful for programmable logic controller (PLC) implementation of supervisory controllers with time delay functions. Supervisory controllers are obtained as in untimed systems by using Ramadge-Wonham framework and then they are refined by the assignment of time delay values to respected events. The implementation of timed transition is realized by using on delay timers of PLCs. The applicability of the proposed method is demonstrated by means of a manufacturing system consisting of two machines and one buffer.