Abstract: Abrupt failure of equipments in FMS is modeled by Petri nets, which can describe the behavior of malfunctioning equipment such as failure, recovery and rework with a failure place, a failure transition and a recovery transistion. Based on such modeling techniques, a new deadlock prevention method is presented, which controls elementary siphons only and makes dependent siphons P-invariant controlled by adjusting the control depth variables of elementary siphons. The structure of the resultant supervisors can be greatly simplified due to the fact that only the elementary siphons need to be explicitly controlled.

Key words: deadlock prevention, flexible manufacturing system(FMS), elementary siphon