Design Of Automobile Wire Harness CAD System Based On Semantics

Wire harness technological design (WHTD) is an important step in automobile wire harness production process. To carry through WHTD quickly with CAD systems has been the goal for wire harness manufacturers. However, the generic CAD software is not good enough to meet the all-round requirements of WHTD. There are many large discrepancies between the software functions and actual demands. In this dissertation, the concept of engineering semantics is introduced, and the domain knowledge in automobile wire harness industry is summarized, and then a semantic-based CAD system for automobile wire harness is designed and developed, which enables users to carry out WHTD at a higher level and realize presenting users'design-intent and high-level semantic information in the design process. The research is mainly discussed in the following several respects:(1) A semantic model to keep all kinds of engineering semantic information in wire harness graph (WHG) is established. The features of WHG are summarized, and semantic information is classified into feature information, constraint information and management information. Besides, a semantic model representing WHG based on hierarchical architecture is established and the corresponding operation process model is given.(2) A semantic analysis-based connection relation design algorithm is presented, which can analyze WHG by means of connection loop extraction, topological structure transformation and later semantic analysis processing. Connection loop extraction algorithm realizes extracting all the connection loops from WHG. Topological structure transformation algorithm can verify the validity of connection points, and analyze the physical connection relationship of wires in connection loops. Later semantic analysis processing selects wire crimp terminals and generates wire harness technological files automatically.(3) An automatic wire harness pre-assembly planning method is presented by means of summarizing engineering semantic constraints in WHTD and establishing assembly incidence graph. This method realizes planning wire harness pre-assembly sequences through main-connector selection, the largest subassembly extraction and engineering semantic constraints detection without users'interaction.