Petri Net Decomposition Control Optimization

Automatic Manufacturing System(AMS)is a production process with less human interven-tion.Due to the lack of human intervention and unreasonable resource allocation,deadlocks can easily occur.In order to ensure the smoothly operation of the automated manufacturing system,the deadlock problems need to be resolved first.Petri net can be effectively used as a tool for modeling and analyzing manufacturing system.On the basis of the theory of Petri net,researchers have proposed various control methods for the deadlock problems in automated manufacturing systems.Generally,these control methods need to calculate the reachability graph or siphons of the Petri net models.Therefore,computational complexity is an issue that needs to be concerned.In addition,because certain permission behaviors of the system may be prohibited when designing the controller,it is also important to reduce the influence of the controller on the permission behavior of the system.This thesis aims at the problems of the existing decomposition control algorithm.From the perspective of structural analysis,taking S3PR(System of Simple Sequential Processes with Resources)as the model,the permissive behavior of the net model is studied.First of all,according to the existing decomposition control strategy,the reason for the legal markings lost is analyzed.It is found that some legal markings in the system are prohibited when some single direction running states are paired controlled.In order to avoid prohibiting these legal markings,this thesis improves the existing decomposition control algorithm,the main contents of the work are as follows:1.Aiming at the S3PR,this thesis analyzes its structure and calculates the reachability graph of the decomposed control model.By analyzing the decomposed control system,we find some legal markings are prohibited during the control.Analyzing these legal markings,it is found that when the single direction running states are paired,making the shared transition enabled markings will not cause deadlock,so the pairing should not be prohibited.For this problem of the single direction running states pairing,this thesis proposes a decomposition control optimization method.Compared with the existing decomposition control algorithm,this method can get more permissive behaviors.2.By redividing the single direction running states,the paired states that do not need to be considered can be effectively avoided.Hence the computation burden of the control method is optimized.