Research And Design Of 3D Scanning System For Mechanical Workpiece Based On Surface Structured Light

With the development of the industrial modernization,the level of manufacturing has been greatly improved,and the demand for spatial 3D information processing in the manufacturing industry has become a trend.Because of its non-contact,high speed,wide measurement range,and high measurement accuracy,the structured light 3D scanning method has been widely used in industrial production,cultural relics protection,reverse engineering,medical diagnosis,and other fields.It is the most promising non-contact 3D scanning method with potential for development and application.The paper conducted a large number of investigations on the equipment and technology of 3D scanning on the market.Combined with the specific requirements for the grabbing of mechanical workpieces in the project,taking into account technical feasibility,costs,and other requirements,the paper adopted a 3D scanning technology of surface-based structure light,studied and designs a prototype system for 3D scanning of mechanical workpieces as well.The system can reconstruct the 3D point cloud on the outer surface of the scanned object in a short time when the projector and the camera are accurately calibrated.The main research and design work of the paper is as follows:(1)the paper analyzes the overall framework design of the 3D scanning system,mainly including the hardware platform composition and software system function design,and designed a feasible method for synchronization function of the camera shoot-projector projection;(2)the paper analyzes the mathematical model of the camera and the projector in detail,and designs two calibration strategies for solving the internal and external parameters of the camera and the projector: the traditional calibration method and the calibration optimization method based on the corner neighborhood homography.The latter is more stable and easier to operate with guaranteed calibration accuracy;(3)the paper analyzes and compares the natural binary coding,the 100%gray-and-reversed Gray code,the phase shift method and other coding schemes,and the coding and decoding strategy of 100% gray-and-reversed Gray code combined with phase shift method is designed in the 3D scanning system.This strategy combines the advantages ofthe former with a high coding range and the latter with a high resolution.At the same time,the paper designs an effective method for extracting effective region and sub-pixel-level boundary detection in decoding,which improves the accuracy of decoding;(4)Based on the triangulation principle,two kinds of point cloud generation strategies are designed,which correspond to the two kinds of coding strategies of projection-only longitudinally encoded fringe patterns and the projected horizontally-longitudinally encoded fringe patterns.Two kinds of point cloud generation strategies have their own advantages.The former eliminates the projection time of horizontally encoded fringe patterns,while the latter eliminates iterative calculations.At the same time,the related point cloud processing methods were designed to initially process the original point clouds of the scanned mechanical workpieces;(5)the paper studies the performance parameters and scanning accuracy of the 3D scanning system,and analyzes the key factors affecting the scanning accuracy.At the same time,the paper puts forward a theoretical method for the optimization of point cloud generation for 3D scanning system.In the Ubuntu operating system,the paper implements independent C++ codes for each functional module involved in the 3D scanning system,and integrates them into a software system.It runs stably on a well-built hardware platform and scans the mechanical parts for a good scan effect.