Abstract
This paper addresses the deadlock avoidance problem in track systems in semiconductor fabrication. For the system without buffer space in it, the existing deadlock avoidance policies tend to be too conservative. Routing flexibility provides a chance to develop better ones, but makes their computation more complex. This paper models a track system using coloured resource-oriented Petri net (CROPN). Based on the model, a sufficient condition for deadlock-free operation and the corresponding control law are presented. This proposed policy is shown computationally efficient and less conservative than existing methods. An example is presented to demonstrate its application.