Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
Browse
2 results
Search Results
Master Thesis Nonlinear Controller Design for High Speed Dynamic Atomic Force Microscope System(Izmir Institute of Technology, 2018) Coşar, Alper; Balantekin, MüjdatIn this study, the performances of conventionally used PI controller and a nonlinear H∞ controller, are compared in the state-of-the-art High-Speed Dynamic Atomic Force Microscope (HS-AFM). The state-of-the-art HS-AFM system is modeled via MATLAB/ SIMULINK for four different cantilevers, i.e., small high-frequency and regular lowfrequency cantilevers used in air and liquid environments. For the modeled system, PI and H∞ controllers are designed and implemented by using both analytical methods and toolboxes available in MATLAB. Simulations are performed in ideal condition, and under exogenous effects such as noise, disturbance and parametric uncertainty. In ideal condition, achieved maximum frame rate, and the percentage of topography acquisition error with two controllers are calculated for each cantilever. Also, performances of controllers in the system are tested under exogenous effects. It is observed that with the H∞ controller, the topography of the selected sample can be obtained with up to 2 times less acquisition error. It is also observed that PI controller is better in disturbance rejection, but H∞ controller is more robust under the effect of noise. For each cantilever, similar results to the ideal condition is obtained in case of uncertainty. Most distinctive results are obtained with high-frequency cantilevers, as H∞ controller enables a 2 times higher frame rate (14.3 fps) compared to the PI controller (7.1 fps) with the same level of acquisition error in the state-of-the-art HS-AFM operated in liquid environment.Master Thesis Analysis of Cantilevers for High-Speed Atomic Force Microscopy(Izmir Institute of Technology, 2018) Brar, Harpreet Singh; Balantekin, MüjdatIn life sciences, High-Speed Atomic Force Microscopy (HS-AFM) is now widely accepted as a dynamic event visualizer for numerous biological samples such as live cells, membrane lipids, ATP-proteins, enzymatic reactions, DNA-protein interactions, etc. HSAFM’s unique ability to observe surface topography of the samples with height data and with a resolution of up-to a single atom makes it a prominent tool in Nano measurements. HS-AFM Imaging technique’s speed and response is limited by various factors including cantilever probes, operating environment, scanning techniques etc. Cantilevers are indispensable and integral part of HS-AFM Systems, thereby necessitating their own critical evaluations. Therefore, evaluation of various parameters like resonance frequency, stiffness and Q-factor of cantilevers is an active area of research. The simulated research work mimics the experimental conditions of HS-AFM operation in air and liquid environment. The damping mechanisms such as viscous and acoustic damping of the medium, squeeze film damping, and damping due to viscoelasticity of the material are included in the finite element simulations. High frequency soft cantilevers suitable for HS-AFM with the stiffness of ~1 N/m and with the first flexural eigenmode resonance frequency of ~1.5 MHz (in liquid) and ~5 MHz (in air) are studied. Numerous small rectangular and modified cantilevers of Silicon and Polymer (SU-8) materials with the length of ~5 to 10 μm, width of ~1 to 2.5 μm and thickness of ~0.1 to 0.6 μm are analyzed. Our aim in this research is to identify appropriate cantilever geometries and materials for HS-AFM applications.