Research And Implement Of MES Scheduler Based On Petri Net With DCOM

The steady market is becoming easier to change because of variation and individuation of customers' demands. To fit in this circumstance, agile response and flexibility will be the great characteristics of manufactories in 21st century. The wise and practical strategy for our country in current situation is information integration and information combination of automation islands. For manufactories of "much variety and little batch" are so easily influenced by outside market, MES is very important as a linkage between upper management level and workshop. As the core part of MES, scheduling module is the engine for productivity in workshop according to the plan. In order to improve agility and flexibility, a logical scheduling is very essential for taking the best of resource and WIP management. As to academic research, most of scheduling optimizations belongs to NP-complete problems, and the system models are built on some kinds of ideal assumptions to the real world, the scheduling results are so rigid that it can't offer a solution to the dynamic events and turbulences. However, some dynamic events and turbulences are inevitable in manufactories of "much variety and little batch". Considering the gap between academic research and real world application, the characteristic of manufactories of "much variety and little batch", this paper discusses the abstraction and modeling of the workshop performance using colored Petri net characterizing definite description of DEDS. And rule bases are applied into the model to tackle the dynamic events and disturbances with dynamic scheduling. After analysis on agile response of MES and integration of its scheduling model, by adopting distributed component technology the workshop scheduling model was capsulated as a scheduler to realize the scheduling module of MES easier to be integrated and rapidly reused. Finally a prototype of scheduler is proposed.