Ontology Based Product Configuration Solution

The target of Mass Customization(MC) is to provide customized products and services with similar cost and speed of Mass Production(MP). Product configuration,which has been realized preliminarily in the Product Data Management(PDM) systems,is the key enabling technique for realizing MC,because it can form the customized product rapidly based on the pre-defined parts,subassembly sets and the constraint relationships among them.Nevertheless,the existing PDM systems support only document and design procedure management,with relatively weak functions in product structure modeling and configuration management,leading to a low effiency in acquiring the necessary product information in design,production and maintenance periods.Hence it is very important to build a uniform product information model to realize the integration of product configuration information so that,the economic benefits and the ability to adapt the changing market of an enterprise can be improved.In view of the above questions,the product configuration technology was researched in this paper. A three-layer configuration solution was proposed,and the detailed researchs of product configuration knowledge modeling,fuzzy configuration of subassemblies and multi-objective optimization of product configuration were presented respectively.A three-layer configuration solution was designed from product configuration modeling to optimization,which lays the foundation for the succeeded research in product configuration.By using a configurable product example this solving system was discussed,and the changing of solution spaces was researched.The input and output of each layer and re- lationships among three layers were discussed.Different acting roles and realizing functions of this solution system in configuration operational flow view and Bill of Material(BOM) view were demonstrated.The core framework of this three-layer configuration solution was established and the scheme for integrating the configuration system and other information systems of the users was designed.Modelling of the product configuration was studied,and the configuration ontology was designed,which realized the modeling of structure information of configurable product,constraint relationships and customized requirements.By proposing an ontology based product configuration knowledge model,the structuring method and orientation of the configuration ontology were analyzed.The terms related to the configuration ontology were classified and the detailed semantic representations were designed. The advantage of this ontology based product configuration knowledge model was analyzed.The information transformation between configuration ontology and outside data was researched.A case study was applied,which proved this configuration ontology is generic,and when using it in a special configuration area,the simple extention or inheritance was enough for representing.A case-reuse based fuzzy configuration method was proposed for configuring the middle layer of subassemblies.Predefined product structure information was used as the pre-condition and the conditional probability was used as the core formula.The definition of fuzzy configuration of product middle layer subassemblies was researched,and the advantages of this new method were concluded by comparing it with the traditional method of case-based reasoning(CBR).The mechanism of case-reuse based fuzzy configuration(CRFC) was researched in detail,including the application pre-condition,the upper consistency rule,the application mechanism of conditional probability,and the estimation method of judgment threshold as well as the specific analysis of algorithm flow chart.The CRFC algorithm was applied on a configuration case,and the result showed the validation and the advantages with repect to the CBR algorithm.A product configuration optimization method was proposed based on the Multi-Objective Genetic Algorithm(MOGA).Using the most minimized cost,most minimized lead-time and most balanced inventory as the three optimization objectives,the instance parts were configured after the middle subassembly layer configuration result was obtained.Detailed description definition and mathematic formula of multi-objective optimization of product configuration was discussed.The optimization objective functions and constraints matrix were designed.The mechanism of MOGA based product configuration optimization was researched,including the detailed design of Nondominated Sorting Genetic Algorithm-â…¡(NSGA-â…¡) based solution steps and population initialization coding method.The selection mechanism of population was designed detailedly.The three optimization objective functions were used as the fitness functions and the fitness punishment approach was designed for the constraints violated configurations. The definition of nondominated sorting was discussed and the classification method of nondominated ranks was designed.The niche division calculation formula and sorting method was designed.It was used for guaranteeing the diversity of population.The binary tournament selection was used based on the nondominated sorting and niche division,and the elitist strategy was used for preserving the lost of excellent individuals in the process of evolution. By copying,crossing over and mutating,new population was generated. The termination conditions were also improved with new algorithm to avoid the evolution converging too early.With these measures,the processing problem of mass complicated configuration data was solved.