Design of a linear-motion dual-stage actuation system for precision control

Abstract

Actuators with high linear-motion speed, high positioning resolution and a long motionstroke are needed in many precision machining systems. In some current systems, voice coilmotors (VCMs) are implemented for servo control. While the voice coil motors may providethe long motion stroke needed in many applications, the main obstacle that hinders theimprovement of the machining accuracy and efficiency is their limited bandwidth.To fundamentally solve this issue, we propose to develop a dual-stage actuationsystem that consists of a voice coil motor that covers the coarse motion, and apiezoelectric stack actuator that induces the fine motion, thus enhancing the positioningaccuracy. The focus of this present research is the mechatronics design and synthesisof the new actuation system. In particular, a flexure hinge based mechanismis developed to provide a motion guide and preload to the piezoelectric stackactuator that is serially connected to the voice coil motor. This mechanism isbuilt upon parallel plane flexure hinges. A series of numerical and experimentalstudies are carried out to facilitate the system design and the model identification.The effectiveness of the proposed system is demonstrated through open-loopstudies and preliminary closed-loop control practice. While the primary goal of thisparticular design is aimed at enhancing optical lens machining, the concept andapproach outlined are generic and can be extended to a variety of applications.