A Knee Point Smoothing Method for Discrete Machining Paths

Abstract

The invention relates to a method for smoothing an inflection point of a discrete processing path, and belongs to the field of high-speed high-performance numerical control processing. The method is characterized in that an externally tangent quintic B-spline curve with 9 control points is adopted to carry out smoothing processing on the inflection point of the discrete processing path, and problems of low speed and easy fluctuation in conventional discrete path inflection point processing are solved. The method comprises the steps of firstly constructing concrete forms of a characteristic polygon of a B-spline curve formed by the 9 control points and a node vector of the characteristic polygon with the aid of a vertex overlapping method and a convex-hull property, and back calculating the control points under the constraint of approximating to an error allowance value; then carrying out one-time correction on the control point by adopting a proportion regulating algorithm based on a length constraint of a transition section; and finally, and acquiring a quintic B-spline curve for inflection point smoothing according to the acquired characteristic polygon and the node vector. The method provided by the invention can enable the smoothed path to reach G1 continuity, and the smoothed curve has a greater curvature radius at the inflection point under the same error approximating condition compared with an internally tangent method.

Description

technical field [0001] The invention relates to a method for smoothing inflection points of discrete processing paths, belonging to the field of high-speed and high-performance numerical control processing. Background technique [0002] In NC machining, the discrete machining path is composed of many G0 continuous straight line segments. The path at the inflection point is described by a G0 straight line segment, which will lead to the discontinuity of the tangent vector and the curvature, which will cause the CNC system to start and stop frequently during the machining process, causing fluctuations in machining speed, decreased machining surface quality, and low machining efficiency. Therefore, the traditional discrete machining path is not suitable for high-speed and high-performance CNC machining. It is necessary to smooth the tool path at the inflection point. There are three requirements: 1) Ensure that the transition curve between the machining straight line and the in...

AI Technical Summary

Problems solved by technology

When the corners of two adjacent processing straight line segments at the inflection point are relatively sharp, that is, when the corners are small, the curvature of the smooth curve at the inflection point is still relatively large under the approximation error allowance, and the smoothing effect is relatively inconspicuous, and it is necessary to sacrifice the speed to ensure the processing quality, not conducive to high-speed machining

So far, the relevant literature has not well addressed the smoothing of paths with sharp inflection points

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