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Indexed by:期刊论文

Date of Publication:2017-05-01

Journal:INTERNATIONAL JOURNAL OF MACHINE TOOLS & MANUFACTURE

Included Journals:SCIE、EI

Volume:116

Page Number:1-17

ISSN No.:0890-6955

Key Words:NURBS interpolator; Feedrate scheduling; Feedrate-sensitive region; Parametric interpolation; Contour error

Abstract:This paper presents a systematic NURBS interpolator with constant speed at feedrate-sensitive regions under drive and contour-error constraints to generate a smooth and contour-error bruited NURBS toolpath without a large feedrate variation, thus balancing the machining quality, precision, and efficiency. After introducing the concept of feedrate-sensitive regions, the scheduled feedrate in this paper keeps constant at most areas and only varies smoothly within partial of the transition regions, which is beneficial to the machining quality. The servo-lag induced contour error in real machining is considered as an additional constraint accompanied by the geometric and drive constraints during feedrate scheduling, so that the contour error can be bounded from the source, thus improving the machining precision. A 2nd-order Runge-Kutta parametric interpolation method with parameter compensation and transition-point feedrate correction, based on displacement-controlled feedrate generation, is presented for generation of not only the smooth feedrate profile without abrupt change at transition points between constant and variable speed regions, but also the degired interpolation points with an extremely small feedrate fluctuation. The proposed systematic interpolation method contains two blocks: offline pre-processor and online interpolator. The parameter-feedrate set of acceleration/deceleration-start points is created in the pre-processor such that the smooth feedrate profile and desired toolpath can be generated in the online interpolator without complex look-ahead algorithms. Performance of the presented interpolator are evaluated both by simulations and by experimental tests.