Research On Model And Algorithm For Process State Net With Changeable Structure

The process planning and production scheduling are traditionally regarded as two independentprocedures, which often result in that the process planning is not usable in practical scheduling. TheIPPS (integrated process planning and scheduling) model is proposed for trying to solve the problem,where the flexible process route model which can completely reflect the logistics, state and controlinformation is one of the key technologies of IPPS. There are two challenges to build the flexibleprocess route model, i.e., the dynamics of logical relations between processes, and the combinationexplosion of intermediate states of products. Aiming at the combination explosion, the PSN (ProcessState Net) model is presented. Furthermore, considering the dynamics of process relations, thePSN-CS (Process State Net with Changeable Structure) model is proposed.In the present dissertation, systematic researches are carried through revolving around thePSN-CS. Building and optimizing the flexible process route model under the conditions of dynamicchanges of process relations and combination explosion of intermediate states of products, areinvestigated, and then the solution model of IPPS based on PSN-CS is built, and lastly the integratedscheduling based on this model when the processes are parallelizable is discussed. The main worksof the present dissertation are as follows:1. PSN modelAiming at the sharp growth of intermediate states of products, the PSN model of flexibleprocess route is put forward. The model uses the combination of some process states to represent theintermediate states of products by introducing the concept of process state, which avoids that eachintermediate state is represented by a node in the model. So the model effectively reduces thenumber of nodes and simplifies the model representation of flexible process route.2. PSN-CS ModelThe essence factors which result in the dynamic change of process logic relations are discussed,and the concepts of combination input arc of workpiece and combination enabling arc of workpieceare put forward, and then based on the two concepts, the PSN-CS model for flexible process route isproposed. The PSN-CS model effectively expresses the dynamic change of process relations withoutincreasing the number of nodes, thus lays the foundation for automatic generation of the flexibleprocess route model.3. Building and optimizing for PSN-CS modelThe workpieces are divided into the basic and special ones, and the extraction algorithm forbasic workpieces is given; it is pointed out that PSN-CS model should build just for basic workpieces,which simplifies the PSN-CS model from its structure. Then the algorithm is given for mapping process logic relationship to PSN-CS model. The optimization techniques for PSN-CS model areprovided from three aspects, i.e., experience rules, structure optimization and level optimization,which effectively reduce the solution space of IPPS problems.4. The application of PSN-CS ModelThe IPPS problem model is established based on PSN-CS. Generating and adjusting the specificprocess route of production tasks are discussed, and then the generation and adjustment algorithm ofprocess route is given. The GA (Genetic Algorithm) solution model for IPPS problems under thecondition of which process can be parallelizable, is researched, and the decoding procedure for GAis researched. At last, taking the wire harness production as an example, the harness IPPS prototypesystem has been developed.