Research On Smooth Interpolation Method For High Speed Machining Path Of Continuous Small Line Segments

The traditional continuous small line interpolation method can not adapt to the high-speed machining of complex curves and surfaces.The phenomenon of speed sudden stop will appear at the corner of continuous small line segment of CNC machine tool,which will lead to severe vibration and impact of the machine tool,thus affecting the surface quality of parts.Trajectory smoothing and velocity planning between continuous small line segments is still one of the difficult problems in interpolation of continuous small line segments.In order to solve this problem,this thesis aims at the high-speed machining of continuous small line segments and the realization of high-order continuity of the trajectory,and takes the construction of smooth machining path and high-speed smooth tool movement as the main line to study the trajectory smoothing and speed planning in the machining process.In this thesis,the continuity of machining path is taken as the breakthrough point,and the mixed curve and linear corner path of the tool are deeply analyzed from two aspects of geometric continuity and parameter continuity.Combined with speed planning and forward-looking control,the smooth movement of the tool is realized.The main contents of this thesis are as followsFirstly,this thesis analyzes the current continuous small segment high-speed machining technology and research status,respectively introduces the path smoothing algorithm,acceleration and deceleration control algorithm and forward-looking control theory,and confirms the research from the perspective of realizing high-order continuous tool path.In addition,the basic principles of B-spline curve and PH curve,flexible acceleration and deceleration algorithm and forward-looking control are studied,which provides a solid theoretical basis for the subsequent construction of transition curve and speed planning.Secondly,from the perspective of geometric continuity,a high-speed interpolation algorithm based on G~3continuity is proposed.The algorithm synthesizes the constraints of the length and angle of the continuous small line segments,performs non-uniform B-spline curve fitting for the qualified small line segments,and uses PH curve interpolation for the corners between adjacent different types of line segments to construct G~3continuous tool path,so as to meet the requirements of high machining efficiency and smooth contour to a certain extent.In addition,the forward-looking control and S-curve acceleration and deceleration strategy based on jump limit are combined to smooth the speed planning.Compared with the non-uniform B-spline algorithm and p H curve algorithm,this algorithm improves the machining efficiency and contour accuracy.Finally,from the point of view of parameter continuity,a corner interpolation algorithm of p H curve based on C~3continuity is proposed.With the advantage that the arc length of PH curve can be calculated in real time,the online corner smoothing and interpolation algorithm can be realized,which can improve the processing efficiency.This path not only has the characteristics of high-order continuity,but also can ensure that the maximum deviation of the corner is within the constraint range.The Fifth Polynomial programming is used to plan the velocity of the trajectory.Compared with the PH curve algorithm based on C~2continuity,this algorithm can not only ensure the controllable contour error,but also ensure the smoothness of acceleration and jump,reduce the vibration of the machine tool to a certain extent,and optimize the processing efficiency.To sum up,the two directions of continuity in the process of continuous small line segment high-speed machining are deeply studied,the corresponding path fairing method and speed planning algorithm are put forward,and finally the whole machining path is satisfied with high-order continuity,and the smooth transition of tool path trajectory and speed is realized.