Shop Scheduling with Time Lags Based on Petri Nets and Heuristic Search

The increasing demand for diversity and individuation of commodities in such a smart manufacturing age leads to new requirement for the flexibility and responsiveness of shop scheduling. This paper mainly deals with the scheduling in an industry computer main board production line which can be modeled as a job shop scheduling problem with time tag according to its real situation analysis. A new responsively heuristic search, combing with petri nets modeling and the heuristic L1 algorithm, is proposed to solve the problem. The method uses best first strategy to expand the scale of reachability graph, and then pruning techniques are applied to make sure that the solution complies with the request of time constraints. At the same time, the maximum degree of petri net concurrence approach is developed to accelerate the search process in case of the status explosion of petri nets. Experimental results are carried out to show the effectiveness and responsiveness of the method. Especially the concurrency strategy can reduce about 82.18% average percentage of the number of markings comparing with the one without concurrency consideration.