Necessary and sufficient conditions for deadlock-free operation in flexible manufacturing systems using a colored Petri net model

Concurrent competition for finite resources by multiple parts in flexible m anufacturing systems (FMS's) results in deadlock. This is an important issu e to be addressed in the operation of the system. A Petri net model, called colored resource-oriented Petri net (CROPN), is del-eloped in this paper. The concurrent resource contention and the important characteristics of the production processes necessary for deadlock control are well modeled by th is model. Based on the developed model, necessary and sufficient conditions and an efficient control law are presented for deadlock-free operation in FMS's. This control law is a policy of dynamic resource allocation. It dete rmines when a resource can be allocated to which job to avoid deadlock, Thi s control law allows as many active parts as possible to be in the system, while deadlock is totally avoided, This control law is easy to implement an d can be embedded into the real-time scheduler. A simple example is used to illustrate the application of the approach.