Development and implementation for real-time lookahead interpolator by using Bezier curve to fit CNC continuous short blocks

Abstract

This paper describes the analysis of a command generator, i.e. interpolator, used for CNC machine motion control. The lookahead algorithm discussed in this paper involves circular contraction error, corner error and deceleration distance limit; hence, planning of a more rational feedrate profile across a series of blocks is made possible. With a prescribed precision, the feedrate and machining performance can be enhanced by looking ahead multi-blocks. To smooth out trajectory interpolation of continuous short blocks, hereafter referred to as CSBs, this paper presents cubic Bezier curve for fitting. Two criteria, the critical corner angle and the bi-chord error, determine if the cubic Bezier curve fits in interpolation. Results from simulation and testrun confirm advantages of cubic Bezier curve for real-time CSBs fitting.