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A Characteristic Analysis of the Laser Range Finder with Various Modulation Frequencies
Heesun Yoon,Jinpyo Hong,Huisung Kim,Kyihwan Park 제어로봇시스템학회 2008 제어로봇시스템학회 국제학술대회 논문집 Vol.2008 No.10
In the signal processing of phase demodulation, the maximum detecting distance and the sensor resolution are directly determined by the modulation frequency. To have higher resolution of distance in the laser range finder using the phase demodulation method, signal should be modulated with a high frequency. However, it is not easy to have higher resolution with long range detection. Because, the maximum detecting distance is restricted by the modulation frequency. It is advantageous to use a proper frequency which is suitable for the each purpose. Analytical and experimental results are presented to show how the modulation frequency affects to the results.
Yoon, Heesun,Cho, Jungyeon,Kim, Jongsoo American Astronomical Society 2016 The Astrophysical journal Vol.831 No.1
<P>Turbulent motions naturally produce density and magnetic-field fluctuations. Correlation between the two fluctuations is important for interpretation of observations, such as observations of the rotation measure (RM). In this paper, we study the effect of driving schemes on the density-magnetic-field correlation. In particular, we numerically investigate how the correlation time of driving affects the correlation between density and magnetic field. We perform compressible magnetohydrodynamic turbulence simulations at different sonic Mach numbers (M-s), using two different driving schemes-a finite-correlated driving and a delta-correlated driving. In the former, the forcing vectors change continuously with a correlation time comparable to the large-eddy turnover time. In the latter, the direction (and amplitude) of driving changes in a very short timescale. The finite-correlated driving results in strong anti-correlation between two fields when the sonic and the Alfvenic Mach numbers are similar to unity (i.e., when Ms similar to 1 and MA similar to 1 ,respectively). However, the anti-correlation becomes weaker and approaches zero for higher values of Ms or MA. The delta-correlated driving produces virtually no correlation between two fields when Ms similar to 1 and MA similar to 1, and produces more and more positive correlations as Ms or MA increases. We conjecture that two competing effects, tendency for achieving balance between the gas and the magnetic pressure and simultaneous compression of fluid and magnetic field, determine the correlation behavior. We also investigate how different driving schemes affect the Probability Density Function of three-dimensional density, dispersion measure, and RM.</P>
모바일 로봇 네비게이션을 위한 Lock-in Amplifier 방식의 레이저 거리 측정기
윤희선(Heesun Yoon),박기환(Kyihwan Park) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
Map building is the most important thing for the mobile robots navigation. It requires specific vision system such as CCD camera, range finding system, and many other things. Laser range finder has highly collimated beams can be obtained easily, thus achieving lateral resolution, and short wavelengths involved cause the light to be backscattered, rather than reflected by the target. For the signal processing, the Lock-in amplifier system is addressed in this paper. We used a diffused reflected beam to detect phase shift in this system. But this beam is minuteness signal so it can be easily buried in nose. Lock-in amplifier is used to measure the amplitude and phase of signals which are buried in noise.