| Virtual manufacturing technology was used extensively, because it could optimize product manufacturing process, and could avoid serious mistakes, before the actual manufacturing of the product, through simulating different manufacturing processes in the computer. However, because the software development of Virtual Manufacturing System (VMS) is very difficult, the application of VMS was hindered.This paper analyzed the two main building apporachs of virtual manufacturing system and reasons of their development efficiency. Then it was found that the data model, the interface specification and the simulation tools were important factors to the development efficiency.Research of Virtual Manufacturing Platform (VMP) includes many works. Based on analysis of VMP function and composition, this paper focused on formal development method, formal description and data specification of manufacturing models.No standard data model could be referred, no sharable data between different systems could be used and product model was in lack of engineering semantics. So in order to realize VMS rapid construction and data sharing, this paper thought that there was a need for standardization of manufacturing data. Compared with process-oriented and object-oriented methods, the system description according to formal method was stricter, accurater and clearer. So this paper used Z notation, a formal tool, to developt VMP and normalize the related data.Based on comprehensive analysis and summary on the specification steps and tools, this paper proposed a manufacturing-related data specification solution for VMP, and used Z notation to describe the manufacturing-related products, resources, process model, and designed related data text format according to these description.VMP proposed by this paper, will contribute to a new development mode of VMS, and will reduce the VMS development difficulty. Secondly, the use of formal methods will be helpful to the VMS development of high stability and high reliability. Moreover, the results of formal description and data specification, can realize data standardization of VMP, and can realize data sharing between different VMS. So the methods and results in this paper are valuable for VMS development and system integration.The main content of the paper is summarized as follows:(1) VMS formal description method using Z notation was studied, and a VMS development mode based on this formal method was put forward.The tools used by Process-Oriented and Object-Oriented development approach were natural language or graphical symbols, so it was possible that system description contained redundancy, errors and contradictions. For this shortcoming, this paper used formal technology, which is based on strict mathematics theory, to describe VMS. According to the general description procedure of Z, the higher level formal description of VMS at the viewpoint of set was studied. A development mode of VMS based on the manufacturing information metadata was put forward.(2) The formal specification technology of product model was studied.According to formal method, at the viewpoint of set, the product model was designed as a set, which contained general attribution, parts, assemblies, topological relationship, assembly relationship, mechanism constraint, precision and datum elements.In order to meet the demand of displayability, editability and engineering information of product model in VMS, a product model with engineering information was designed. In aspect of geometrical model, a based-feature model which combined CSG and B-rep was designed. It retained the product surface represent, added the modeling process represent, and designed a connection relation between them. The feature surface of the new product model could support the assembly relationship specification. The datum elements set could support engineering information specification, such as product dimension, form and position tolerance, fitness and surface roughness.In aspect of assembly relation, two methods were designed. One was called "assemle", which could describe the static position relationship of models, another was called "Link", which could describe the dynamic mechanism motion constraint. The "Link" method defined the motion constraint through definition of "PoseRelationship" and "MotionRelationship".In aspect of topological relationship, several key problems, such as Z specification of inclusion relation between parts and assemblies, Z specification of connection relation between CSG and B-rep, hierarchical relationship between B-rep models, were solved.Many types used in Z schema specification were defined from top to bottom.(3) The formal specification technology of resource model was studied.According to formal method, at the viewpoint of set, the resource model was designed as a set, which contained general attribution, parts and components assembly, topological relationships, control panels, operating control relations, moveable components, unmoveable components, function elements. Except for the section defined in chapter 3, abstract function, control panels and operation process specificatioin were studied.In aspect of control panel, the panel components were classified as output display, indicator, static text, turn button and button five types, according to function and form. The ControlPanel schema was defined on the basis of all components Z specification.In aspect of operation control process, a control process metamodel was put forward. According to the metamodel, all operation control processes consisted of CtrlPFlagNode, CtrlPConnector and CtrlPMoveNode three kinds of nodes. Every CtrlPMoveNode consisted of DriveAssembly, DrivenAssembly, MoveMode, RelavantData, FanIn and FanOut six elements. And a graphical tool for control process modeling was designed. The control process modeling method based on the metamodel made resource modeling easier and more understandalbe.In aspect of function specification, according to the demand of VMS face to manufacturing, resource function was designed as the abstract function, rules and states set. The assemblies were classified as ActiveMoveableAssembly, PassiveMoveable Assembly, ActiveStaticAssembly and PassiveStaticAssembly. In order to distinguish assembly ability and state, four states were designed for assembly. Thus specification problems of abstract function and state set were solved during using Z notatioin. (4) The formal specification technology of produce model was studied.According to formal method, at the viewpoint of set and state, the produce process model was designed as a set, which contained a manufacturing process for the same products with the same produce process.In aspect of manufacturing process, a manufacturing process metamodel was put forward facing to machining and assembly, based on analysis of Workflow process metamodel, "method study analysis technology" in production, and IDEF3 standard. According to the metamodel, a machining or assembly process model is a set, which consisted of StartNode, EndNode, TaskNode, ControlConnector and ObjectConnector. Every manufacturing process is made up of subprocesses and kernel elements, which contained Node and Connector. Node and Connector are both consisted of Product, Resource, RelavantData and Transition. The four composition would answer four questions respectively, that is what product was being processed, what device was being used, which way was being used and where the product would go after this process. The manufactuing activity is presented by TaskNode, which contained three FlagNodes and seven TaskNodes. And every TaskNode was corresponding to a device of FixResource. The Connector connected two nodes, and was classified ControlConnector and ObjectConnector. The ControlConnector represented the sequence of two nodes, and the ObjectConnector also represented the products transportation except for sequence. The device resources were classified as fixed resource and transport resource. The fixed resource connected a TaskNode, and the transport resource connected ObjectConnector.A graphical tool for manufacturing process modeling was designed, which is based on the activity network diagram. There were nine symbols in the graphical tool, four TaskNode symbols of which succeeded from "Flow process chart" of engineering analysis.The modeling examples of machining and assembly, proved the metamodel effectiveness.(5) The text format of product, production and produce model was designed for data sharing.VMS was in lack of shareable data, so in order to meet function demand of VMP and realize quick reconstruction and data sharing of VMS, the research work for data specification of manufacturing model was necessary.Data specification contained three steps; the first and second parts were finished by UML and Z. At the last step, a text format based on Z specification was designed.In short, in order to improve the development efficiency of VMS, it is necessary to study a VMP. This paper focuses on the formal development method, formal description and data specification of manufacturing models. A Z-based formal development method, which is helpful to high reliability and high safety system development, was put forward for VMS. This paper designed related manufacturing information model, and realized specification description by Z notation. The formal specification of manufacturing model would be beneficial to VMP. The manufacturing informatioin model text would be beneficial to data sharing between different systems, and to quick reconstruction of VMS. |
