Research On The Algorithm Of Nurbs Curve Interpolation And Speed Look-ahead In Motion Control System

In the motion control system,there are two main ways of continuous curve segmentation and parameter curve interpolation for complex curve path planning.It is expected to ensure high accuracy and stability while maintaining high feedrate.In this paper,the continuous line segment speed look-ahead algorithm and NURBS(Non-uniform rational B-splines)interpolation are studied.a NURBS curve bidirectional adaptive interpolation algorithm based on speed look-ahead optimization is proposed and Verifying the performance of the algorithm with simulation and experiments.Firstly,the design of continuous line segment speed look-ahead algorithm is studied.S-type acceleration/deceleration control is applied to speed planning and featuring classification for acceleration and deceleration characteristics.The transition speed of line segment connection point is optimized for angle constraint and length constraint,and the adaptive determination of the forward-looking interval is proposed.Secondly,the mathematical principle and foundation of the commonly used NURBS curve in parameter curve interpolation are introduced,and analyzing the interpolation principle of the parameter curve through combining the interpolation technique with the NURBS curve.An improved algorithm for the interpolation parameters of NURBS curves is given by introducing the numerical analysis method while considering the error limitation.Next,considering the feedrate limit of the feedrate extreme point generated by the NURBS curve due to the curvature change,the speed look-ahead optimization is given and the interpolation interval are divided.Because the NURBS curve deceleration point is difficult to predict and the curve length cannot be accurately described,the concept of positive and negative two-way interpolation is proposed.At the same time,the S-type acceleration/deceleration control is improved to dynamically and efficiently solve the actual maximum feedrate and meeting point of the two-way interpolation in the interpolation interval.And the defect of the traditional interpolation algorithms that only pay attention to the feedrate limit at the extreme point of the feedrate and ignore the overall feedrate limit is improved,achieving the feedrate is adaptively adjusted to meet all the constraints.The proposed algorithm is simulated by the example to visually reflect the improvement of the traditional interpolation algorithm.Finally,the algorithm function is realized in the independent multi-axis motion controller,and the experimental platform is built for experimental analysis to verify the excellent performance and applicability of the algorithm.The experimental results show that the proposed NURBS curve bidirectional adaptive interpolation algorithm can efficiently calculate the feedrate,accurately calculate the interpolation parameters,and output the interpolation data in real time to meet the accuracy,feedrate and stability requirements of the motion control system.