Design and Development of Biaxial Nano-scale Positioning System
Date Issued
2010
Date
2010
Author(s)
Chen, Shao-Lun
Abstract
A biaxial long-stroke positioning system applied to the sample delivery in scanning probe microscopy (SPM) is designed and developed in this thesis. The biaxial nano-scale positioning system is built up by three subsystems, which include two linear actuators, two displacement sensors, and one positioning controller.
In order to achieve long-stroke and nano-scale positioning function, each linear actuator is driven by four shear motion mode (SMM) piezoelements on the inertial driving principle. And the flat-circular spring is applied to realize a frictionless rolling guide for the linear actuator and a stable actuating friction between the stage and the four piezolements.
For realizing a compact system, the tiny HOE pick-up head is chosen as the displacement sensor. And through equipping adequate objective lens and collimator lens its measurement resolution is enhanced. The derived output signal from the HOE pick up head, the focus error signal (FES), is well in linear proportion to the actuation displacement. The displacement signals and the driving voltages for actuators are all processed in the positioning controller. The inertial driving principle of the linear actuator is detailedly analyzed to study the relationship between main influential parameters and the positioning performance. Moreover, the positioning performance is also experimentally verified.
The maximum stroke for each linear actuator is 4 mm, and its stepping resolution is about 4.1 nm. The actuator can drive a maximum payload of 200g. And by the resonant driving frequency of 2 kHz, the actuator can achieve a maximum average step of 50 nm. The biaxial positioning system not only can produce fast and coarse positioning actuation through high driving voltage and frequency, but also can realize precision nano-scale positioning through low driving voltage and frequency. The positioning accuracy is mainly dependent on the displacement sensing performance of the HOE-pick up head, whose measurement resolution is 6.3 nm.
Subjects
Positioning system
Linear actuator
Shear motion mode (SMM) piezoelement
Inertial driving principle
Flat-circular spring guide
Holographic optic element (HOE)
Focus error signal (FES)
Type
thesis
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