High precision locating control system based on
VCM for Talbot lithography
Jingwei Yao
a,b
, Lixin Zhao*
a,b
, Qian Deng
a,b
, Song Hu
a,b
a
Institution of optics and electronics, Chinese Academy of Sciences, Chengdu 610209, China
b
University of Chinese Academy of Sciences, Beijing 100039, China
ABSTRACT
Aiming at the high precision and efficiency requirements of Z-direction locating in Talbot lithography, a control system
based on Voice Coil Motor (VCM) was designed. In this paper, we built a math model of VCM and its moving
characteristic was analyzed. A double-closed loop control strategy including position loop and current loop were
accomplished. The current loop was implemented by driver, in order to achieve the rapid follow of the system current.
The position loop was completed by the digital signal processor (DSP) and the position feedback was achieved by high
precision linear scales. Feed forward control and position feedback Proportion Integration Differentiation (PID) control
were applied in order to compensate for dynamic lag and improve the response speed of the system. And the high
precision and efficiency of the system were verified by simulation and experiments. The results demonstrated that the
performance of Z-direction gantry was obviously improved, having high precision, quick responses, strong real-time
and easily to expend for higher precision.
Keywords: Talbot lithography, voice coil motor, PID control strategy, DSP
1. INTRODUCTION
With the development of technology, the materials with periodic micro-nano structure such as grating, aperture arrays,
are widely used in several important areas. As far, methods to product low-cost high-resolution periodic micro-nano
structures mainly rely on near-field lithography or interference. In recent years, a new method of lithography using
Talbot effect has come out in periodic micro-nano structure making, which attracts much interests because of its low-
cost, high-efficiency and high-resolution
[1]
. However, as the resolution increases, the focal depth of Taber lithography
will quickly decrease. Hence, accurate positioning the focal depth becomes the key point to enhance resolution of
Talbot lithography
[2]
.
The voice coil motor is a moving coil DC motor, which is a novel direct-drive motor based on the principle of Lorentz
force. The difference of voice coil motor from general linear motor is that it has the advantages of no hysteresis, high
response, small size, high resolution, good strength property and ease of control, etc., so that be more suitable for high
acceleration, high-frequency excitation, fast and precise positioning motion systems
[4-6]
. In this paper, we designed a
precision positioning system based on DSP controller and voice coil motor brake, which was adopted on Talbot
lithography for Z-direction precision positioning platform to achieve high-precision positioning.
2. MATHEMATICAL MODEL AND TRANSFER FUNCTION OF VOICE COIL MOTOR
Figure 1 shows the principle of voice coil motor, the coil can move around along the ferromagnetic cylinder. In the
travel range of the coil, a substantial uniform magnetic field is provided by a permanent magnet to the coil. When direct
current I is passed through the coil, according to the Lorentz force equation, we can obtain the electromagnetic force
suffered on the coil:
e
Proc. of SPIE Vol. 9685, 96850L · © 2016 SPIE · CCC code: 0277-786X/16/$18 · doi: 10.1117/12.2243616
Proc. of SPIE Vol. 9685 96850L-1