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Master's Thesis

Grating Motor Control

Henrik Björk

Abstract

A monochromator is a part of a spectrometer in which the grating scans the different wavelengths over the exit slit. A full spectrum is generated as the grating scans over a predefined interval. The grating must accelerate to a set speed very fast, then keep the speed constant over a predefined interval, and break to reverse the scan. On top of this come disturbances from an optical filter, causing vibrations in the housing, which can be seen in the spectra if not corrected for in the control algorithm. A model-based control system composed of Proportional-Integral (PI) control, and Iterative Learning Control (ILC), is implemented on a Field-Programmable Gate Array, using LabVIEW. The proposed controller shows promising results, with closed loop rise time within given bounds, and reduced disturbance effects.


Master's Thesis ISRN LUTFD2/TFRT--5868--SE, Department of Automatic Control, Lund University, Sweden, December 2010.

 
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