20-09-2014, 12:41 PM
Dynamic Analysis for bracket of FOG
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Abstract
Fiber Optical Gyroscope (FOG) is becoming
affordable for many applications such as vehicle navigation
and stabilization. Operating under the circumstance of which,
vibration can’t be ignored. This paper researched into the
characteristic of vibration of structure of FOG. Base on the
model analysis using ANSYS (finite element analysis software),
we did dynamic analysis for bracket of FOG. On the model
analysis, we got the frequencies and model shapes of bracket.
On the harmonic response analysis, we got the curves of
frequency response. We analyse the frequencies and model
shapes of bracket. At last, we brought forward the methods to
optimize the framework design of FOG.
THE DYNAMIC ANALYSIS OF THE BRACKET BY ANSYS
We have deduced the vibration equations, and analysed
the vibration characteristics of structure in the upper
segment. But the actual structure of system usually is very
complex, and can’t achieve the natural frequencies and
models by theory calculation. We use Pro/e and ANSYS to
model the bracket and do model analysis to it.
We build the models of the mechanical structure of FOG
in Pro/e, as the Fig. 1 shows.
OPTIMUM DESIGN OF THE BRACKET
From the analysis of the upper segment, the resonant
frequency of the bracket is higher than 200Hz. Although it
can meet the vibration request of warship environment, real
warship environment is emergence, various high frequency
vibration also possibility random emergence. In these
complicated usage environment, the resonant frequency of
306Hz is obviously lower. Therefore, when we analyse and
design the bracket carrying the coiling frameworks, we
should as far as possible put its resonant frequency higher
than the resonant frequency of warship. So the FOG can
avoid a resonance circumstance in the usage, in order to
reduce the modulation effect of the fiber optic coiling.
At the condition, that the shape and size of the bracket
isn’t changed, the wall thickness of bracket is increased
50%. Do dynamic analysis in the upper segment again. In
the model analysis, we find the resonant frequency of thebracket is increased. There are four resonant frequencies in
the 2000Hz, they are 384.12Hz、1151.7Hz、1433.4Hz、
1731.7Hz, and the model shapes have on variety change
than before. In the harmonic response analysis, the normal
direction has no improvement, but the acceleration response
of side direction is reduced than original design.
CONCLUSION
This paper does dynamic analysis for the bracket of
FOG by using ANSYS. We basically study the contribution
of the resonant frequency and model shape in different
directions, which can affect the bracket vibration. Discuss
the reason of the phenomenon, optimize the structure of the
bracket.
Above analysis result is subjected to various factor of
influence, such as the details of FEM model, fitted precision
and terminal condition etc. But the analysis result can reflect
the actual circumstance, can give very important reference
to the structure optimum design.