Lyapunov Estimator for High-Speed Demodulation in Dynamic Mode Atomic Force Microscopy

In dynamic mode atomic force microscopy (AFM), the imaging bandwidth is governed by the slowest component in the open-loop chain consisting of the vertical actuator, cantilever, and demodulator. While the common demodulation method is to use a lock-in amplifier (LIA), its performance is ultimately b...

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Bibliographic Details
Published inIEEE transactions on control systems technology Vol. 26; no. 2; pp. 765 - 772
Main Authors Ragazzon, Michael R. P., Ruppert, Michael G., Harcombe, David M., Fleming, Andrew J., Gravdahl, Jan Tommy
Format Journal Article
LanguageEnglish
Published IEEE 01.03.2018
Subjects
Amplitude estimation
atomic force microscopy (AFM)
Bandwidth
Convergence
Demodulation
Dynamics
Force
Kalman filters
Lyapunov methods
nanopositioning
parameter estimation
phase estimation
Transfer functions
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Summary:In dynamic mode atomic force microscopy (AFM), the imaging bandwidth is governed by the slowest component in the open-loop chain consisting of the vertical actuator, cantilever, and demodulator. While the common demodulation method is to use a lock-in amplifier (LIA), its performance is ultimately bounded by the bandwidth of the postmixing low-pass filters. This brief proposes an amplitude and phase estimation method based on a strictly positive real Lyapunov design approach. The estimator is designed to be of low complexity while allowing for high bandwidth. In addition, suitable gains for high performance are suggested such that no tuning is necessary. The Lyapunov estimator is experimentally implemented for amplitude demodulation and shown to surpass the LIA in terms of tracking bandwidth and noise performance. High-speed AFM images are presented to corroborate the results.
ISSN:1063-6536
1558-0865
DOI:10.1109/TCST.2017.2692721