Research On Smooth Compression Of Small Line Segments And Parametric Curve Interpolation Method

Small line interpolation method can not realize high speed and high finish equality processing.Parametric curve interpolation method has been proved to compensate these defects theoredically.In this paper,methods of G01 codes smooth compression and parametric curve interpolation were studied.Smooth compression of small lines helps to reduce data quantity and obtain parametric curve paths.The interpolation curve fitting method can obtain high precision parametric path,and approximation fitting greatly compress the amount of data.The realization of local interpolation curve fitting method,which is fast for computer calculation,was deduced detailly.A complex tool path smooth compressing algorithm based on interpolation curve fitting of dominant points was proposed.Original data points were preprocessed to select the dominant points to generate a B-spline curve.Selection criteria are curvature threshold,the curvature maxima,the curve inflection point,the length mutation point before and the error maxima after Bezier curve fitting.The minimum speed points could be defined before parametric curve interpolation.Based on these points the curve was segmented into sub-curves,whose length was estimated simultaneously.The 7-stage S-type ACC/DEC principle was applied for each sub-curve of speed planning in the continuous time domain.The total interpolation time was periodized to output discrete speed values.In order to minimize the speed jump in conjuncture between two sub-curves,an approach of ACC/DEC time rescheduling was proposed here.To reduce the speed fluctuation caused by interpolating parameter calculation,the inverse quadratic interpolation?IQI?method,which needs no iteration and has high calculation precision,was implemented instead of normal way of 2-order Taylor expansion.Simulation results of a semi-butterfly curve show that the proposed algorithm can smoothly compress the trajectory points with a ratio over 2;the ACC/DEC time rescheduling and periodic discretization methods meet the dynamic performance of the machine tool,and the speed fluctuation reaches to 10^-6 level in parametric curve interpolating.