Study On The Key Technologies Of Knowledge-based Cooperative CAPP System

Computer Aided Process Planning(CAPP) acts as the bridge between Computer Aided Design and Computer Aided Manufacturing, which has an important effect on the quality and cost of product development. In this dissertation, by analyzing contemporary manufacturing enterprises'requirements for CAPP functions, key technologies of knowledge based cooperative CAPP system have been investigated, such as domain model, knowledge integration, cooperative process planning and optimization ,and so on. The main contents and achievements of the dissertation are as follows:1. Firstly the dissertation presents the history, state of the art and research trend of CAPP. Then the problems which CAPP faces in practical applications are analyzed. Furthermore, the necessity to establish knowledge based cooperative CAPP system is put forward.2. The requirements of CAPP system for knowledge management and cooperative process planning are analyzed, and key techniques of knowledge based cooperative CAPP system are proposed in detail. Meanwhile, a multi-level model of cooperative process planning is presented. Then, the target, work flow and system structure of the knowledge based cooperative CAPP system are given.3. CAPP domain analyzing and modeling based on ontology have been studied.The role of ontology in domain analyzing is described, and an idea that ontology model and UML model are combined to describe CAPP domain is put forward. Then a multi-level domain ontology model is proposed, the domain ontology development principle is described, and the domain ontology development method is given. In addition, an extensive study on the development procedure of CAPP domain ontology is carried out. The mapping rules from ontology model to UML model are presented, so that the corresponding UML model can be obtained through the ontology model.4. CAPP knowledge integration and retrieval based on ontology have been studied. By analyzing the heterogeneous types of CAPP knowledge and integration requirements, a knowledge integration structure based on ontology is proposed, and presentation model of knowledge source, semantic mapping based on ontology, as well as interfacing criteria of CAPP knowledge have been explored particularly. Then a semi-automatic method to integrate heterogeneous CAPP knowledge based on ontology is put forward, and the key technologies are investigated as well. Furhermore, methods of CAPP knowledge retrieval based on ontology and semantic expansion are presented, and examples are given to verify the methods.5. Knowledge based cooperative process planning and optimization have been studied. A knowledge representation model based on ontology is given, and a knowledge share structure of cooperative process planning is proposed on the base of discussing the knowledge management and organization. Then a multi-view model of cooperative process planning workflow is given, and a process cooperation procedure model is proposed. Furhermore, the method of process knowledge utilization is described, and the synchronization mechanism, session mechanism, communication mechanism and control mechanism in process cooperative compilation are discussed particularly, and the resolution strategies are given respectively. Focusing on the optional process routes in the cooperative process planning, a layered process routes optimization strategy based on diploid genetic algorithm is proposed, and an example is given to verify the method.6. The basic composing and communication mechanism of J2EE components are described, and the development strategy and overall structure of the knowledge based cooperative CAPP system are given out. Some function modules are developed, such as ontology management module, CAPP knowledge module, process workflow management module, process cooperative compilation module and process route optimization module. The application instance of the developed system is described with detailed demonstrations.