A global curvature continuous smoothing method for micro-segment processing

Abstract

The invention discloses a global curvature continuous smoothing method aiming at micro-line segment processing. Three times of NURBS curves are used to establish a knife position track model so that asecond derivative of a fitted curve of a knife position point is globally continuous. In an existing fitting method, a point which does not satisfy a fitting condition is reserved or processed simplyand a connection portion only adopts G0 or G1 continuity. In the invention, the above technical problem is solved. A three-point circle fitting method is used to estimate a fitting error of three continuous adjacent knife position points in a plurality of micro-line segments; a micro-line segment set with the fitting error which is less than or equal to a fitting error threshold is defined as anA-type micro-line segment set; the micro-line segment set with the fitting error which is greater than a fitting error threshold is defined as a B-type micro-line segment set; and for the A-type micro-line segment set, a data volume is compressed through using selection of key points and a head and tail second-order guide vector continuous interpolation fitting method. For the B-type micro-line segment set, rapid smoothing is achieved by using construction of the key points and the head and tail second-order guide vector continuous interpolation fitting method.

Description

technical field [0001] The invention relates to the technical field of numerical control in mechanical manufacturing engineering technology, in particular to a global curvature continuous smoothing method for micro-line segment processing. Background technique [0002] At present, with the development of modern manufacturing industry and the continuous improvement of people's design requirements, more and more complex parameter curves (surfaces) are applied to the solid modeling design of industrial products. Since most CAM software cannot directly generate non-uniform rational B Spline (NURBS) and other parametric curves make it possible to use a large number of micro-line segments to approximate the processing surface in practical applications, thereby realizing the processing of complex surfaces. However, the method of using micro-segments to process curves and surfaces will bring many disadvantages, such as: large amount of program, slow processing speed, large speed flu...

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Problems solved by technology

[0003] According to the summary of the existing technology, it is found that in the literature such as "A high-efficiency machining method for complex curved surface parts (ZL201610625772.3)", the least squares fitting method is used for the refined tool position points, which can ensure that the inside of the fitting curve The derivative is continuous, but because many line segments do not meet the fitting conditions and need to be retained, the joints between these line segments and other reserved line segments or fitting curves are only continuous at points (that is, "G0 continuous"), and their derivatives are discontinuous of

The literature "Jin Yu'an, He Yong, Fu Jianzhong. NURBS and Hermite mixed high-speed machining interpolation algorithm [J]. Journal of Zhejiang University (Engineering Science Edition), 2014 (4): 641-648." proposed to use NURBS curve and Hermite curve to micro The method of smoothing the line segment can ensure that the smoothed curve is continuous in the first order derivative (that is, "G1 continuous"), but it cannot guarantee the continuity of the curvature (that is, "G2 continuous"). In addition, it can satisfy all The method of direct fitting of all fitting points of the fitting condition is not conducive to data compression

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