Design and Control of a Precision Electromagnetic Positioner for Large Measurement-range Atomic Force Microscope
Date Issued
2011
Date
2011
Author(s)
Peng, Yuan-Zhi
Abstract
Conventional atomic force microscope suffers from the limitation of small scanning scale, due to the short travelling range of piezoelectric actuation. In this thesis, a large measurement-range AFM scanning stage which combines both fine positioners respectively with piezoelectric actuation and electromagnetic one is proposed. While the piezoelectric positioner provides high speed scanning in an 8 μm2 frame with nanometer resolution, the precision electromagnetic positioner is capable of scanning a large image and position samples in a 500 μm2 large field with at least 29 nm rms positioning error.
The overall stage consists of 4 pairs of electromagnetic actuator, monolithic serial flexure guidance, an eddy current damper, and a commercial xyz piezoelectric positioner. To do the AFM scanning, two pairs of parabolic compression springs in x- and y-axis are designed to enhance the decoupling structure and stiffness, as well as to compensate the loading in vertical direction. Moreover, obtaining the precise feedback signals from a 2-axis laser interferometer, an MIMO adaptive sliding mode controller, which is prior to three other conventional controllers, is used to overcome the unmodeled system uncertainties, coupling motion and external noises, including the scanning disturbances. Experiments and application results are presented, indicating the promising positioning and scanning ability of the proposed stage.
Subjects
precision motion control
electromagnetic actuation
adaptive sliding mode control
AFM
Type
thesis
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