On Operation Control Of A Class Of Systems With Consumable Resources Based On Time Petri Nets

The control of the deadlock problems in the Automated Manufacturing System(AMS)is essential to the whole system's realization and operation.Petri nets are a kind of mathematical modeling and analysis tool that can intuitively and effectively carry out modeling,analysis,and deadlock control of AMS,so it is widely used in the theoretical research of the manufacturing systems.The existing research models based on Petri nets are mostly token conservation;that is,there is no operating system that consumes resources.At present,there are relatively few studies on the existence of consumable resource operating systems,and however,most manufacturing systems have resource consumption phenomena.Therefore,modeling and analysis of such systems is necessary.In a actual manufacturing system,it takes a certain amount of time to complete each process.To get closer to the researched systems with the phenomenon of resource consumption,this work adds the time factor to the net model with resource consumption.The influence of the time factor and the resource-consumption factor are considered in this work.This work abstracts the resource consumption phenomenon in a system by changing the weights of the directed arcs in the Petri nets and choosing to add the time factor to the transitions in the form of time interval to model the time-consuming phenomenon of completing the process.During the system's operation,not only will there be a problem of resource consumption,but each process will also consume a certain amount of time so that the modeling and analysis of the system will be more practical.The main tasks completed in this thesis are as follows:1.Use Petri nets to model and analyze the automated manufacturing systems with resource consumption factors,depict the way resources are consumed in the models and describe the method of judging and distinguishing the deadlock states.2.Analyze and select the time Petri nets and the time delay Petri nets,and finally select the time Petri nets that are more suitable for the actual systems' situation.Then the method of adding time is introduced.Through comparative analysis,their properties are analyzed with examples,respectively,and combined with the Petri nets with consumable resources,choose to add time to the change.In Petri nets,the transition is generally regarded as the operating actions in the manufacturing systems,and time is added to transition in the form of intervals so that the time ranges for the emissions of the transitions are limited.The operating process of the actual system can be simulated.Finally,several analysis methods are used to analyze the net model,and several methods are improved to make them apply to the resource consumption net models with the time factor.3.The definition of a new subclass of Petri nets combined with the resource consumption factor and the time factor is given,referred to as resource consumption time nets for short.First,the work analyze the proposed net models and compare their reachability graphs with ones of ordinary net models and resource consumption ones.It is found that the resource consumption factor and the time factor will increase the reachability and cause the expansion of the state space.The traditional reachability graph analysis method cannot consider the time factor,so this work adds the time factor to the reachability diagram,proposes the reachability class diagram,and gives the realization algorithm.Then the deadlock reachable classes in the reachable class graph are analyzed and classified,and the algorithm of reachable class classification is given.To control the deadlocks that need to be preverded,a method of the hierarchical priority of reachable classes is proposed.The implementation algorithm ensures that the net models will not enter a deadlock state without exhaustion of resources.Finally,according to the resource consumption systems,a solution algorithm for the optimal running path is given.