Research On Key Techniques Of Feature-Based Reverse Engineering System For Modeling Of Aeroengine Pipelines

Pipeline system with complex layout and high design criterion play an important role in the aeroengine. Traditional design and data management is based on practical mockup for aeroengine pipeline system due to no original drawings or documentations. Reverse engineering is a process of constructing CAD model of a physical part from the measuring point data so that subsequent modifying, machining and inspecting processes may be implemented. The CAD model of aeroengine pipeline system reconstructed by reverse engineering can provides enormous benefit in improving the quality and efficiency of design, manufacture, analysis and data management. Research on such a typical system is valuable in the idea and technology to the similar complex industrial environments.In this dissertation, the concept and traditional methods of pipeline system is presented firstly. The basic theories including the definition, classification and representation of geometric feature based reverse engineering are studied systematically. The key techniques for CAD model reconstruction of aeroengine pipeline system are investigated and developed, including multi-view data registration, feature extraction, solid model reconstruction and theory of data segmentation. Main results achieved in dissertation are summarized as follows: Flowchart of modeling techniques based on feature for aeroengine pipeline system: First, the concept and characteristic of pipeline are analyzed. It outlines the present study status of reconstruction method for pipeline in domestic and abroad. The boundary surface of the pipelines is mainly composed of geometric regular surfaces, such as quadric surfaces, sweep surfaces and loft surfaces. Regular surfaces are extracted, which allow the most important feature parameters of the pipelines to be calculated. We present in this paper a method to obtain CAD models of the pipelines from measuring data. The models are based on two classification geometric features, surface-feature and section-feature, which are enough to reconstruct most parts of the pipeline system. The flowchart, architecture, and key techniques related to this methodology are studied. Multi-view data registration technique: Differential geometry properties of the surface are also essential elements of shape recovery methods. In this paper, we recall a few key notions of differential geometry firstly. Some estimation methods of local surface geometry properties for point data also are discussed and implemented. Afterwards, a multi-view registration method is presented, which is done by rough registration and accuracy registration. Rough registration can reduce the difference between models availably and make preparations for accuracy registration.In the process of accuracy registration, The registration algorithm based on L-BFGS-B are proposed.The experiments show this algorithm has better registration accuracy than traditional registration algoritms. Analysis and practical applications of mechanism for data segmentation:Though data segment technique has been researched for sever decades, there has been so lacking available theory to support segmentation algorithms. The mechanism on data segmentation process is investigated according to the principle of normal...