基于重复控制的快速刀具伺服系统前馈补偿方法

Repetitive-control-based Feedforward Compensation Method for Fast Tool Servo System

快速刀具伺服(Fast tool servo,FTS)系统的跟踪性能直接影响其对光学微结构表面的加工精度和加工效率。为此提出基于重复控制的离线前馈补偿方法,该方法通过对跟踪误差进行分段在线学习和离线补偿,实现FTS系统对非周期参考轨迹的高速精密跟踪。在自制单轴FTS系统上进行对比跟踪测试,测试结果表明:相比于二自由度控制方法,提出的离线前馈补偿方法对随机均匀B样条曲线和复合频率正弦曲线的均方根跟踪误差分别减小94.47%和93.83%。此外,将该FTS系统与超精密车床联动在高转速下加工得到网格面和复眼透镜阵列,这两种表面的最大轮廓误差分别为93.59 nm和134.73 nm,表面粗糙度均小于5 nm。研究结果为基于FTS的光学微结构表面高效、高精加工提供了新方法和新思路。

The machining accuracy and efficiency of optical micro-structured surfaces depend on the tracking performance of fast tool servo(FTS)systems.Therefore,a feedforward compensation method based on repetitive controller(RC)is proposed to address this issue.For this method,the precise tracking of aperiodic reference trajectories is achieved for FTS systems by the online learning and offline compensation of the segmented tracking errors.The comparative tracking experiments are conducted on a self-developed monoaxial FTS system,and the experimental results show that the RMS tracking errors of the two degree-of-freedom control method are reduced by 94.47%and 93.83%via using the proposed method when tracking the random uniform B-spline curve and the muti-frequency sinusoidal curve,respectively.Furthermore,the grid surface and the compound eye lens array are machined under a high spindle speed with the proposed feedforward compensation method by integrating the FTS system into an ultraprecision lathe.The maximum contour error of the obtained two types of surfaces are 93.59 nm and 134.73 nm,respectively,and the surface roughness of both two surfaces is less than 5 nm.The results provide a novel method and a new idea for FTS systems to achieve the high efficiency and high precision machining of optical micro-structured surfaces.