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Force Microscopes (force + microscopes)

Distribution by Scientific Domains
Engineering85%

Kinds of Force Microscopes

  • atomic force microscopes
    		•

    Selected Abstracts

    Identification, control and hysteresis compensation of a 3 DOF metrological AFM

    ASIAN JOURNAL OF CONTROL, Issue 2 2009
    Roel Merry
    Abstract Atomic Force Microscopes (AFMs) are widely used for the investigation of samples at the nanometer scale. The metrological AFM used in this work uses a 3 degrees-of-freedom (DOFs) stage, driven by piezo-stack actuators, for sample manipulation in combination with a fixed cantilever. The piezo-stack actuators suffer from hysteresis, which acts as a nonlinear disturbance on the system and/or can change the system dynamics. The contributions of this paper are the application of feedback control to all 3 DOFs of the metrological AFM and the design and application of a hysteresis feedforward for the asymmetric hysteresis present in the system. The amount of coupling between the DOFs is assessed by a non-parametric multiple-input-multiple-output (MIMO) identification. Since the dynamics appear to be decoupled in the frequency range of interest, feedback controllers are designed for each DOF separately. For the modeling of the asymmetric hysteresis an extended Coleman-Hodgdon model is proposed. This model is used for feedforward compensation of the hysteresis. The combination of feedback control for all DOFs and the asymmetric hysteresis feedforward enables the AFM to track scanning profiles within the sensor bound of 5,nm. Real-time imaging of the sample is possible with an accuracy of 2,nm. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [source]

    Image-based hysteresis modeling and compensation for an AFM piezo-scanner,

    ASIAN JOURNAL OF CONTROL, Issue 2 2009
    Yudong Zhang
    Abstract As an important component of Atomic Force Microscopes (AFM), a piezo-scanner exhibits some undesired nonlinear characteristics, among which the inherent hysteresis largely decreases positioning accuracy during scanning and nano-manipulation process. To alleviate this problem, an image-based approach is proposed in this paper to model and then compensate for the hysteresis behavior of the piezo-scanner. Specifically, some scanning images over standard samples are utilized to identify the parameters of the classical Preisach model (CPM) of hysteresis. On the basis of the obtained model, an inversion-based technique is adopted to design a compensator for the hysteresis of the piezo-scanner. The proposed algorithm presents such advantages as low cost and little complexity since no nanoscale position sensor is required to collect identification data. Some scanning and nano-imprinting results are included to demonstrate the performance of the proposed strategy. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [source]

    Accessing Time,Varying Forces on the Vibrating Tip of the Dynamic Atomic Force Microscope to Map Material Composition

    ISRAEL JOURNAL OF CHEMISTRY, Issue 2 2008
    Ozgur Sahin
    In dynamic atomic force microscopes the primary physical quantities being measured are the amplitude/phase or amplitude/frequency of the vibrating force probe. Topographic images with spatial resolutions down to the atomic scale can be obtained by mapping these measurements across the sample surface under feedback control. During the imaging process the vibrating tip is observing tip,sample interaction potentials (force,distance relationships) at every point on the surface. The interaction potential is a superposition of short- and long,distance interactions of various origins determined by the material compositions of the tip, sample, and the medium of imaging. In principle, measurement of tip,sample interaction potential should allow determination and mapping of material composition of the sample. However, a single measurement of amplitude/phase or amplitude/frequency in dynamic atomic force microscopes is not enough to characterize a complicated tip,sample interaction potential. Recent developments in the understanding of dynamics of the vibrating force probe (cantilever), together with specially designed cantilevers that utilize torsional vibrations in addition to conventional vertical vibrations, enable the recovery of tip,sample interaction potentials at a timescale less than a millisecond. Here, with theory and experiments, we discuss how these cantilevers recover the information about the tip,sample interaction forces and give an example of compositional mapping on a polymeric material system. [source]

    Measurements with a 2D Laser-Cantilever-Anemometer compared to an x-wire probe

    PROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2009
    Jaroslaw Puczylowski
    The 2D Laser-Cantilever-Anemometer (2D-LCA) was developed to measure flow velocities in two dimensions. A sensitive meausuring principle adopted from atomic force microscopes allows a spatial and temporal resolution comparable to modern x-wire anemometry. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    A comparison of control architectures for atomic force microscopes,

    ASIAN JOURNAL OF CONTROL, Issue 2 2009
    J. A. Butterworth
    Abstract We evaluate the performance of two control architectures applied to atomic force microscopes (AFM). Feedback-only control is a natural solution and has been applied widely. Expanding on that, combining feedback controllers with plant-injection feedforward filters has been shown to greatly improve tracking performance in AFMs. Alternatively, performance can also be improved by the use of a closed-loop-injection feedforward filter applied to the reference input before it enters the feedback loop. In this paper, we compare the plant-injection architecture with the closed-loop-injection architecture when used in controlling AFMs. In particular, we provide experimental results demonstrating the closed-loop-injection architecture yields better tracking performance of a raster scan. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [source]

    Semi-automatic tuning of PID gains for atomic force microscopes

    ASIAN JOURNAL OF CONTROL, Issue 2 2009
    Daniel Y. Abramovitch
    Abstract The control of a typical commercial Atomic Force Microscope (AFM) is through some variant on a Proportional, Integral, Derivative (PID) controller. Typically, the gains are hand tuned so as to keep the bandwidth of the system far below the first resonant frequency of the actuator. This paper shows a straightforward method of selecting PID gains from the actuator model so as to allow considerably higher bandwidths. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [source]