Active Vibration Isolation Technologies for Scanning Probe Microscope
Date Issued
2004
Date
2004
Author(s)
Lan, Kuo-Jung
DOI
en-US
Abstract
This research investigates the Active Vibration Isolation (AVI) issues related with the Scanning Probe Microscope (SPM). AVI is gaining increased attention in the ultra high precision applications to effectively treat the unavoidable ground vibration. Particularly, it is critical for the optimum operation of the Molecular Measuring Machine (M3), a high-resolution, length-metrology instrument at the National Institute of Standards and Technology (NIST). NIST is investigating active vibration isolation as an approach to improving the M3 image resolution and measurement speed. The M3 system uses a Mallock suspension to establish a non-rotational constraint to the stage motion. The vibration isolation system has to work along with the Mallock geometry. The system is also a six-input-six-output system; therefore a design has to be followed to limit the controller structure to within the range where it can be implemented. This thesis describes the extension of the M3 Mallock isolation suspension from passive to six degrees-of-freedom (DOF) active vibration isolation. It also presents the full dynamic model of the AVI system with the Mallock suspension. A decoupling process is therefore proposed to decompose the axis dynamics. In the thesis system modeling is presented and experimental system identification is carried out for model verification. The thesis then compares the vibration isolation performance using a classical proportional-integral-derivative (PID) controller versus using a modified, model-based, Linear-Quadratic-Gaussian (LQG) controller. The thesis also designs a Sliding Model Controller (SMC) and Discrete Sliding Mode Controller (DSMC) to overcome the system nonlinearities. The experimental results show that the DSMC controller is more effective than the other controllers over the operating frequency band. The maximum attenuation of 15 dB is achieved within the active vibration isolation control bandwidth, and images taken with the M3 scanning tunneling microscope (STM) probe show the improved performance.
Subjects
掃瞄探針顯微鏡
掃瞄穿隧顯微鏡
順滑模態控制
主動振動抑制
離散順滑模態控制
Linear-Quadratic-Gaussian
Active Vibration Isolation
Scanning Probe Microscope
Sliding Model Controller
Discrete Sliding Mode Controller
scanning tunneling microscope
Type
thesis
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