Showing 2 results for Sh. Mohammad-Nejad
Sh. Mohammad-Nejad, M. Pourmahyabadi, A. Lajevardizadeh,
Volume 2, Issue 3 (October 2006)
Abstract
In this paper, the performance of a Ring Laser Gyro based inertial navigation is
investigated. Dynamic and stochastic modeling are applied to gyro simulation and
performance evaluation. In the dynamic model, some parameters such as scale factor and
environmental sensitivity have been determined, whereas in the stochastic model, the other
parameters such as random drift and measurement noise have been computed. The
performance of the system is evaluated for several inputs. Also, the parameter variation of
output noise as a result of changing the dither characteristics is analyzed.
S. Olyaee, Sh. Mohammad-Nejad,
Volume 3, Issue 3 (October 2007)
Abstract
A new heterodyne nano-displacement with error reduction is presented. The
main errors affecting the displacement accuracy of the nano-displacement measurement
system including intermodulation distortion error, cross-talk error, cross-polarization error
and phase detection error are calculated. In the designed system, a He-Ne laser having
three-longitudinal-mode is considered as the stabilized source. The free spectral range of
the 35cm laser cavity is about 435-MHz at 632.8-nm wavelength, which a secondary beat
frequency equal to 300-kHz is produced by combining the reference and measurement
beams. The resolution of the displacement measurement resulting from intermodulation
distortion, cross-talk and cross-polarization errors is limited to 18-pm. Also, the phase
detection uncertainty causes an error of only 5.9-pm in the displacement measurement.
Furthermore, frequency-path models of two- and three-longitudinal-mode laser
interferometers are modeled as the ac interference, ac reference, dc interference and optical
power terms. A comparison study between two- and three-longitudinal-mode laser
interferometers confirms that the performance of the designed system is considerably
improved.
