Dynamic Scheduling Algorithm for Batch Process Systems Based on Hybrid Petri Nets
Wu Yali¹,Zen Jianchao²,Wei Junhu¹,Sun Guoji¹
(1.Systems Engineering Institute,Xi'an Jiaotong University, Xi'an 710049,China; 2.Division of System Simulation and Computer Application, Taiyuan Heavy Machinery Institute)

Abstract: A hybrid Petri net named colored time constraint hybrid(CTCH) Petri net with the characteristic of dynamical scheduling in batch processes is proposed. The scheduling problem of batch processes is mapped as the solution of the optimal sequences of transitions in CTCH Petri net. Then taking the ultimate utilization of resources, that is the minimal make-sqan as the scheduling objective, a solution method of the optimal sequences of transitons in CTCH Petri nets for batch processes is presented according to the primary principle of the dynamic programming. The method defining time constraint area is discussed under the different intermediate storage policies. Finally, as an example the scheduling problem of steelmaking & continous-cast systemis simulated. The results show that when the scheduling result varies from the start time of each task and device or the dynamical continuous processes change,the scheduling results are different. Hence, this algorithm is verified to be effect.
Keywords: dynamic programming;CTCH Petri nets;process scheduling