Research On NURBS Real Time Interpolation

At present most of the CAD systems have the function of modeling with free-formed curves and surfaces. Generally in order to machine the model created by free-formed surfaces many tiny line segments generate. It results in a larger NC data file. The drawback is that the surfaces machined by that means are not smooth because of the frequently changing of feed speed. The interpolation with free-formed curves has many advantages. It can get high speed, high efficiency and smoother surfaces. So it's significant to develop interpolaton with free-formed curve.NURBS provides a uniform expression of all curves. NURBS interpolation has been a hot research spot and a trend in numerical control filed. In order to meet the need of a corporation's new numerical system, the thesis does research on NURBS real-time interpolation arithmetic that has been integrated into motion card developed by our team. Meanwhile in order to solve the question of manufacture quality because of the tiny lines generated by CAD/CAM systems, the thesis does research on convert continueous tiny line interpolation to NURBS interpolation. Most of the research includes the following content.(1) Design the arithmetic of picking up cutter location points of tiny lines and dividing them into different sections based on the lengths and the angels of lines.(2) Fit the cutter location points with B-spine curves by arithmetics based on knot insertion and based knot removal. By this means tiny lines interpolation codes are converted into NURBS interpolation codes.(3) Develop the NURBS real time interpolation arithmetic that has function of looking up based on interpolation arithmetic of controling chord errors.(4) Integrate the NURBS real time interpolation arithmetic improved by many methods into DSP motion card and rectify the arithmetic in experiment.