Study Of Large Scale Parts Measurement Techniques Based On Flexible Three Coordinate Measuring Machine

At present, large scale and space coordinates measuring system with wide-range,high-precision and flexible has been used more and more widely in modern manufacturingindustry. In many fields of production and engineering, such as aviation, aerospace,electronics, automobile, shipbuilding, communication, nuclear industry, waterconservancy and hydropower, arms and other industries, all need accurate large scalemeasurement methods and instruments. In machinery industry, we need to transform thereal information of the product into CAD model through a certain way in order to reflectthe product appearance better and realize the innovation, so the reverse engineeringtechnology is applied.In this paper, the flexible three coordinate measuring machine and leapfrog balls areused to establish the measurement system to measure the large size parts. Through the useof flexible three coordinates measuring principle, the principle of leapfrog coordinatetransformation and the computer real-time control and processing technology to realize themeasurement of large size parts which is beyond the measurement range of the flexiblethree coordinate measuring machine. The point cloud data of the parts which is measuredusing the flexible three coordinate measuring machine are imported to the reverseengineering software Imageware, and their three-dimensional model are reconstructed,appearance characteristics are restored. The main job of this paper is as follows:The structure of the flexible three coordinates measuring system is analyzed. Usingthe Denavit-Hartenberg matrix method, the ideal mathematical model of the system isestablished. The error sources which influence the system accuracy are analyzed, and theerror mathematical model of the system is established.According to the principle of leapfrog coordinate transformation and methods, theleapfrog mathematical model is established, the coordinate transformation relationshipbetween new and old coordinate system after leapfrogging, and the general coordinatetransformation formula after number of times leapfrogging is derived. The translationalvector and rotation matrix is calculated. The precision of the rotation matrix is analyzed. The basic meaning of reverse engineering technology, application field anddevelopment trend is introduced. Using the reverse engineering software Imageware, thepoint cloud data which is measured with three to coordinate measuring machine is aligned,the curve and the surface is reconstructed, the parts of the three-dimensional model arerestored.