Research And Software Implementation Of A Class Of Variable Structure Petri Nets With Property Preserving

Petri nets can be represented graphically or described mathematically,which is an important tool for modeling and simulating systems in various fields.Traditional Petri net models can simulate the state of each component and the interaction process between components intuitively,but its description ability is limited for the system whose structure changes dynamically.Therefore,extending Petri net to model the variable structure systems has become an important research direction in the field of Petri nets.On the other hand,computer simulation by Petri nets usually requires special software tools and software,so it is necessary to develop corresponding Petri net modeling software for variable structure systems.In order to address the problems above,in this dissertation,by introducing variable structure modeling techniques into traditional Petri nets,a class of variable structure Petri nets named VS-PN is proposed,and the formal mathematical definition and the proof of property preservation are presented.Furthermore,a simulation platform is developed for the proposed variable structure Petri nets,which is used to realize the modeling and simulation of dynamic variable structure systems.The main contents of this dissertation are as follows:(1)A class of variable structure Petri nets called VS-PN is proposed.This type of Petri nets can maintain the boundedness,liveness and reversibility of the original Petri model before and after reconfiguration by limiting the left-hand and right-hand sides of the variable structure rules to the same type of property preserving net.Different from other variable structure Petri nets,VS-PN takes Petri net attributes of reconstructed elements as the limiting target,so that it not only avoids attribute verification after reconstruction,but also can match more types of reconfigurable elements.(2)A reconfigured algorithm for VS-PN is proposed,which can implement the variable structure modeling capability according to the predefined rules.The algorithm is based on the structural features of the reconstructed unit to determine the type and match the subnet,which makes it more versatile and easier to realize the repeated variable structure compared with other variable structure methods.(3)The simulation platform software for the proposed variable structure Petri nets is designed and implemented,which can support the modeling and simulation of basic variable structure systems.Compared with the previous variable structure tools,the interface of the software is more concise and the function is more complete.(4)In order to verify the modeling and simulation capability of the variable structure Petri nets proposed in this dissertation and test the developed simulation tool software tool,we give two actual cases of manufacturing systems and their modeling and simulation results.The results show that the proposed variable structure Petri nets can achieve the desired results.The proposed variable structure Petri nets and the corresponding software tool developed in this dissertation provide a new solution for the modeling and simulation of current variable structure systems,which can be applied in many fields,such as flexible manufacturing systems,systems biology and mobile communication.