A Interpolation Algorithm For Short Line Segments Based On Global Geometric Information

In high speed and high precision machining of complex surface,short line segments need to be fitted into splines.However,when fitting,only the position information of the end points of short line segments is very sensitive to the error of CAM software discrete part model.In addition,because the global geometric information of the model is not known during fitting,the fitting spline is not smooth on the whole,and the curvature fluctuation is large,resulting in frequent fluctuation of speed during processing and poor surface quality of processed parts.Therefore,the concept of global geometric information is proposed in this paper to extract useful geometric information from the global perspective and output it to guide the tangential calculation of short line segments and spline fitting.It is mainly divided into two types: tangential direction information and chord error information.To solve the problem of short line segment fitting curve at the junction of surface and plane combination and the edge of plane,a interpolation algorithm for short line segments based on tangential direction information is proposed.It mainly guides the tangential calculation of the endpoint of short line segment according to tangential direction information to make tangential calculation more accurate,and then conducts spline fitting based on this tangential direction.In the process of short line segment spline fitting,due to the lack of global information and in order to control the processing error,most fitting methods reduce the error to the optimal goal of fitting,which leads to the fitting spline too close to the short line segment and increases the curvature fluctuation of the spline.A interpolation algorithm for short line segments based on chord error information is proposed.By using the chord error information to optimize the tangential calculation of the end points of the short line segment,the fitted splines become fuller and smoother on the whole.In order to solve the problem of spline shape inaccuracy in short line segment blending due to lack of global information,a blending algorithm for short line segments based on chord error information is proposed.The control point calculation of blended spline is optimized according to the chord error information so as to make the shape of blended spline more reasonable.Finally,the above algorithms are integrated to form a interpolation algorithm for short line segments based on global geometric information.After that,the algorithm is verified by simulation and actual machining.Experimental results show that the algorithm can effectively solve the above fitting problems,and can effectively reduce the fluctuation of processing speed,and parts' surface quality is higher.