Knowledge Reuse Method And Application In Digital Aircraft Sheet Metal Parts Manufacturing

The aircraft sheet metal forming process determines that sheet metal parts manufacturing is knowledge-intensive. How to reuse past "knowledge" to design the "information" of the parts' manufacturing elements is critical to develop the technology of Digital Aircraft Sheet metal parts Manufacturing (DASM). The purpose of this thesis is to set up knowledge reuse method in DASM and apply this method to develop DASM technology. The thesis includes:1. The knowledge-intensive features of the Aircraft Sheet metal parts Manufacturing (ASM) process are described. The architecture of the DASM system is built, and the system engineering method is adopted to construct the general problem-solving model in DASM. The knowledge which the main DASM problems rely mainly on to be solved is given.2. The concepts of knowledge and knowledge reuse are defined, and the knowledge reuse process is presented based on the analysis of knowledge life cycle. The knowledge reuse principle is analyzed and the frame of knowledge reuse method involving object modeling, knowledge modeling, knowledge utilization and knowledge management is established. The environment, the constitution of engineering design software and DASM workspace of applying knowledge reuse method are presented.3. The manufacturing-oriented multi-state model for sheet metal parts is further studied. The model structure is built on the basis of the hierarchy of state, feature, element and data. The definition order of the model states is exemplified. Tree-based structure feature model is built. A coding scheme with flexibility providing adequate description for aircraft sheet metal part is presented. The XML schema for sheet metal parts based on structure feature is set up to represent the geometric information. How to use multi-state model to compose ASM knowledge reuse method is analyzed.4. The ontology-based systematic ASM knowledge modeling method is proposed. ASM domain ontologies are constructed, and on the basis of that, the knowledge layer model is established from the top domain to basic type. Knowledge memory net is established to represent the relations among information elements based on knowledge, information and data layer. The knowledge element can be reconfigurable based on unchangeable topological feature in knowledge space. The approach to build knowledge base is presented. 5. The knowledge utilization process and way are described, and the knowledge retrieval process model is set up. The three-level knowledge retrieval method is proposed involving indexing based on knowledge system model, coding-based accurate matching approach, and GRA (Gray Relational Analysis)-based approximate matching approach. Some examples demonstrate the retrieval approaches. The retrieval method is applied to establish the knowledge-based engineering design decision methods for four typical ASM problems.6. The Aircraft Manufacturing Engineering design platform for Sheet metal parts (AMES) combining knowledge reuse and digital definition is built. The AMES design and development scheme is given. The systems of knowledge-based multi-state model design, fabrication order design and rubber pad hydroforming die design are introduced with an example. The application in an aircraft manufacturing factory shows that the developed technology can improve sheet metal parts' quality, shorten manufacturing time and lower manufacturing cost.