Curve Fitting, Lookahead and Interpolation for Five-axis Tool Center Point Trajectory

• Main Authors: Nien-Tzu Yu, 俞念慈
• Other Authors: 林明宗
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/r2zzx8

碩士 === 國立虎尾科技大學 === 機械設計工程研究所 === 103 === In this paper, a feedrate scheduling algorithm with look-ahead and curve fitting functions is proposed to generate smooth five-axis tool center point (TCP) trajectory. The developed algorithm consists of two programs: block process and look-ahead process. In block process, break-points at the conjunction of block segments are first detected where the feedrates at the break-points are all set to zero. TCP commands between two break-points are fitted to a single block segment within a given tolerance or a C3 B-spline curve by using bi-chord error method. Corner feedrate respecting jerk continuity of three linear axes on TCP at each block corner are determined. The axis with maximum movement among linear axes on TCP and rotary axes is selected to be a master, and the ratios among the movements of the master and other axes are obtained. In look-ahead process, five-axis feedrate regulation formulation (FFRF) is utilized to evaluate the maximum velocity of master axis. Feedrate command is adjusted with the constraints of jerks and velocities of linear axes on TCP and rotary axes. S-shape acceleration/deceleration (ACC/DEC) method is used to achieve velocity smoothing and avoid the excitation of structure vibration. Finally, cutting experiments are performed to verify the efficiency of the proposed method on a desktop five-axis engraving machine. The experimental results demonstrate the proposed method can reduce contouring errors to half of that using Heidenhain controller.