Research On Mechanical 3D Scheme Construction Method Based On Sketch Retrieval

The construction of mechanical 3D scheme based on sketch retrieval is one of the ways to realize the intelligent design of 3D scheme.In order to realize the intelligent transformation from scheme sketch to 3D model,this paper proposes a technical scheme which adopts scheme sketch enhancement,the classification of overall structure sketch and the internal primitive detection and recognition of mechanism sketch,and establishes the mapping relationship between scheme sketch and 3D model,so as to realize the rapid transformation from the classification results of scheme to 3D model.Based on the 3D design and development platform and the theory of spatial coordinate transformation,the parametric design and semi-automatic assembly of 3D model are studied.The main work of this paper is as follows.Firstly,the image enhancement of hand drawn sketch is realized.A sketch enhancement preprocessing system with the functions of noise reduction,sharpening and contrast enhancement is established.In this process,Scikit-image and Open CV image processing algorithm libraries are called and the median filtering algorithm,canny contour detection algorithm and histogram equalization algorithm are applied.Secondly,based on the graphic characteristics of parts and components,the graphics of common parts and basic components are used as basic primitives.The convolutional neural network is used to establish the classification and recognition models of overall structural sketches and the internal primitive detection and recognition models of mechanism sketches.The classification and recognition experiments of structural sketches and mechanism sketches are carried out,and the process of mapping 2D sketches to 3D models is given.Then,based on OpenCASCADE software platform,the parametric design method of3 D model is studied.Based on the theory of 3D space coordinate transformation and the principle of matching the parameters of 3D model and the position of spatial coordinate system,a semi-automatic assembly method of 3D model is proposed,and the semiautomatic assembly test of typical mechanism is carried out to realize the semi-automatic assembly function of 3D parts.On this basis,a mechanical 3D scheme design system based on sketch retrieval is preliminarily established,and the function design from simple sketch scheme recognition to 3D mapping is realized.