Research On Direct Processing Of Data Point Cloud Based On Dual Mapping And Artificial Neural Network

As an important approach in creative product design, reverse engineering(RE) has been aroused more and more attention and used widely in many areas such as machinery, aviation, aerospace and medical treatment etc. Reverse engineering is a novel integrated subject and technology coming up with the development of computer science, computational geometry and measuring technology. By using reverse engineering technology, the product development cycle can not only greatly been shorten. It is more importantly that the level of the world's advanced production technology can rapidly been catch up or exceeded as the technology secrets of the foreign advanced equipments and products were opened and the weaknesses of prototype product were found out. Together with CAD/CAE/CAM and the rapid prototyping and manufacturing (RPM), the better quality products can be designed and manufactured, and then the market will be seized quickly. Research on direct processing reconstruction of data point cloud digitized from sculptured surfaces is a focus and key one.Aiming to the features in this dissertation, some of the key issues involved in direct processing of data point cloud are studied and explored in depth digitized from the mechanical product characterized by sculptured surfaces based on dual mapping and artificial neural network, and the main research works and conclusions include:(1) Based on the geometric theory of curves and surfaces, the adaptive curvature continuous measurement method is proposed to ensure the measurement accuracy and speed when the mechanical product characterized by sculptured surfaces is measured on the contact coordinate measuring machines(CMM). The model of detection forward step and side span of the probe is presented and has good versatility and robustness. The adaptive curvature continuous expressions of higher order polynomial form and Bezier form are derived so that a better platform of systematic direct processing reconstruction of data point cloud digitized from sculptured surfaces is built.(2) The artificial neural network method is brought up to align and unify disorder data point cloud collected several times on CMM or laser scanners through repeatedly clamped. After a meticulous comparison of neural network structure is made in training and learning function among current five typical classes of 16 neural networks, the optimal segmentation and sequencing artificial neural networks are found and run functions, coefficients, initial value and the number of neurons in the hidden layers are selected. The neural network model is determined so quickly and accurately to identify and align several of data point clouds that the efficiency and the accuracy are enhanced.(3) Through the calculation model of point cloud density is established, the slicing parameters and direction are identified on data point cloud aligned and the best interactive slicing way is explored. Appropriate data structures are discussed in detail to store unordered data point cloud. Based on the theory of orthogonal projection, the algorithm model and method of dual mapping sequence are set up to search and locate quickly the nearest points of the current point studied in the slice, and then the calculation method of point vectors is acquired to improve the above sort algorithm in view of k-neighborhood theory. After the right sequence is finished within the data slice point and the subdivision method of adjacent section lines is analyzed, the overall 3D topology of scattered data point cloud is constructed by the triangular of the cross-section line subject to less data points without inanition and winding.(4) CNC machining is directly arranged on the triangular facets. Two mutual coupling processes are separated relatively in the generation of interference-free tool path and the interference detection. The model of interference detection is established in the process of CNC machining. The patterns and algorithms are derived suitable for ball-end cutter, flat cut and ring cut, and then the corresponding interference inspection procedures are achieved to check out the local and the global interference when machining on sculptured surfaces. Due to the method of the constant scallop height, the interference-free tool path is accomplished. The tool path is post-processed into the G code program so that sculptured surfaces are machined in order, accurate and fast.Finally based on double mapping and artificial neural network, a direct processing reconstruction system is developed for data point cloud digitized from sculptured surfaces by the combination of OpenGL graphics library using VC++. After the establishment of triangular facets, the CNC direct machining is arranged to skip the traditional surface reconstruction. The integration process of reverse design and CNC machining is integrated and speeded up in order to ensure the product quality and accuracy.