基于软件误差修正的通用直线工作台的纳米级定位控制

提出了一种用于通用压电陶瓷线性马达(PLCM)驱动平台的纳米级定位数控方案,该平台上配有栅距20μm的线性光栅.传统的信号细分多数基于硬件电路,无法对纳米级误差进行灵活的调整.本项研究开发了基于Labview的数字控制系统,该系统具有失真波形的调整、1/4栅距脉冲计数、基于Lissajous圆环的波形细分、后传神经网络和PID控制以及平台的位置反馈控制等特征.介绍了定位控制的3个步骤,即用于长行程连续移动控制的AC模式,用于低速短行程的开关模式控制马达驱动,以及以压电激励方式使马达工作的DC模式,这些步骤能够实现几纳米的精确定位.在每种运动模式下采用了专门的信号处理技术.实验结果表明,此方法可以很容易地应用于线性平台,取得小于31 nm的定位精度,9 mm行程的标准误差小于30 nm.相比于原来移动台±1μm的重复性和±1μm/25 mm的精度,该数字控制系统能够将定位精度提高一个数量级.

Nanopositioning Control on a Commercial Linear Stage by Software Error Correction

A digital control scheme of nanopositioning is proposed on a commercially available piezo ceramic linear motor(PCLM) stage equipped with a linear grating of 20μm pitch. Conventional signal subdivision is mostly based on the liardware circuit, which lacks of flexible adjustment when the disturbances are in nanometer scale. This study has developed a LabVIEW-based digital control system, which features the following functions: adjustment of the distorted waveforms, pulse count to the quarter pitch, waveform subdivision by Lissajous circle, back propagation neural network and PID control, and the position feedback control of the stage. Three steps of positioning control are proposed, namely, the AC mode in continuous motion control for the long stroke, the gate mode to drive the motor in low velocities the short stroke, and the DC mode in which the motor works as a piezo actuator, enabling accurate positioning of a few nanometers. In each mode of motion, a particular signal process technique is employed. Experimental results show this method can easily apply to the studied linear stage to achieve the positioning accuracy within 31 nm and standard deviation within 30 nm for travels up to 9 mm. In comparison with the stage's original specifications of ± 1 μm repeatability and ± 1 μm/25 mm accuracy this digital control system can upgrade the precision to one order.