NURBS (Non-Uniform Rational B-Spline) interpolation method based on machine tool dynamics and curve characteristics

Abstract

The invention discloses an NURBS (Non-Uniform Rational B-Spline) interpolation method based on machine tool dynamics and curve characteristics, which adopts a constraint equation ZHYS considering integrative factors of machine tooling for controlling the feeding speed and the acceleration of the interpolation algorithm. The method consists of three links: pre-interpolation, prospective information processing and real-time interpolation, and comprises the following steps of: carrying out trigonometric function speed smoothing processing according to the corresponding speed mode; storing corresponding data after the trigonometric function speed smoothing processing; adopting the trigonometric function speed smoothing processing according to prospective information if entering an acceleration-deceleration region; and adopting a speed self-adapting method for calculation if not entering the acceleration-deceleration region, thus finally obtaining the coordinates and the feeding speed of interpolation points. The method of the invention has the advantages that the interpolation is always in the safe range of a machine tool, the whole interpolation movement process is smooth and stable through the trigonometric function speed smoothing processing, in addition, the tangential acceleration and the continuity of the tangential acceleration in the speed change region can be ensured, and the NURBS interpolation method has the important significance on the development of a high-speed and high-precision numerical control system.

Description

technical field [0001] The invention belongs to the technology of numerical control system, especially the technical field of motion control of numerical control machine tool or articulated robot. Background technique [0002] The main feature of Non-Uniform Rational B-Spline (NURBS curve for short) is the unification of the B-spline method for describing free-form curves and surfaces and the mathematical method for accurately representing quadratic curves and quadratic surfaces. Given the power and potential of NURBS in shape definition. In 1991, the International Organization for Standardization (ISO) formally promulgated the STEP standard for geometric definition of industrial products, which stipulates that NURBS is the only representation method for free-form curves and surfaces. A large number of free-form surfaces in industries such as aviation, shipbuilding, automobiles, and molds are described by NURBS curves. Research on NURBS interpolation technology is of great ...

AI Technical Summary

Problems solved by technology

The current NURBS interpolation algorithm in high-speed machining mainly has the following problems: constant feed interpolation is difficult to meet the requirements of high speed and high precision at the same time, and variable speed feed may lead to large changes in speed and acceleration, affecting machining stability and machining Accuracy; Insufficient consideration is given to the impact of the jerk with a relatively large mutation during the interpolation process, but in fact, in high-speed machining, a large jerk may cause tool vibration or even tool breakage; Insufficient consideration is given to the acceleration and deceleration performance of the machine tool, usually only considering The influence of tangential and normal acceleration along the path does not take into account the influence of each speed or acceleration decomposed on each axis of the machine tool; the calculation process of the acceleration and deceleration control method is more complicated, and the real-time performance of interpolation is not high

but without smoothing the velocity

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