Title: A study of dynamics of feedrate system-based interpolator for NURBS curve

Authors: Yu Liu, Jie Liu, Zilong Deng

Addresses: Institute of Mechanical and Electronic Engineering School of Mechanical Engineering and Automation, Northeastern University, Box 319, Shenyang, 110819, China. ' Institute of Mechanical and Electronic Engineering School of Mechanical Engineering and Automation, Northeastern University, Box 319, Shenyang, 110819, China. ' Institute of Mechanical and Electronic Engineering School of Mechanical Engineering and Automation, Northeastern University, Box 319, Shenyang, 110819, China

Abstract: In this paper, the entire model of numerical control interpolator, servo unit and feedrate system is given and solved and a new interpolator is proposed. Firstly, according to adaptive feedrate trajectory planning algorithm, reference velocity of current interpolator period is calculated. According to the geometry characteristics, velocity limit is set based on the curvature. In every interpolation period, the dynamic equations are solved to gain the maximum needed torque if current reference velocity is transported to servo unit. If the needed torque is greater than maximum one that servo system can provide, a proper deceleration is applied to decrease the reference velocity. Lastly, first-order Taylor|s expansion approximation is employed to calculate the new interpolation point. This algorithm can adjust the feedrate where the curvature is greater relatively to meet the chord error satisfaction, and the velocity generated is smoother relatively. This algorithm can ensure the servo units can achieve the interpolation point in time, in case great error occurs.

Keywords: NURBS interpolation; machine tool dynamics; adaptive feedrate; chord error; curvature; NURBS curves; modelling; numerical control; NC interpolators; servo units; trajectory planning.

DOI: 10.1504/IJCAT.2011.042241

International Journal of Computer Applications in Technology, 2011 Vol.41 No.1/2, pp.117 - 124

Available online: 01 Sep 2011 *

Full-text access for editors Access for subscribers Purchase this article Comment on this article