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The magnetic field sensitivity of the fiber coil is shown in Tab.1. It can be seen that the magnetic field sensitivity of the fiber coil whose fiber has been de-twisted is about 10.6% of that fiber without de-twist, so the fiber de-twist can effectively reduce the magnetic field sensitivity of the fiber coil.
No. Magnetic field sensitivity of the fiber coil /(°)·h−1·Gs−1 - Fiber without de-twist Fiber with de-twist 1 16.235 2 1.810 6 2 11.383 9 1.052 3 3 13.802 5 1.528 4 Average 13.807 2 1.463 8 Table 1. Magnetic field sensitivity of the fiber coil
The bias of the IFOG in different magnetic field strength is shown as Fig.6. We find that there is a linear relationship between the bias of IFOG and the magnetic field strength: the greater the magnetic field strength is, the greater the influence on the bias is, which is consistent with the theoretical analysis. When the shielding state is different, the magnetic field sensitivity of the fiber coil will differ greatly, as shown in Fig.6 and Tab.2. Compared to the fiber coil in state 1, the fiber coil in state 2 has a good shielding effectiveness, which can achieve to 34.8 dB, but as there is a gap in the connection, the magnetic field sensitivity of the fiber coil in state 2 can only reduce to 0.026 5 (°)·h−1·Gs−1, which cannot meet the requirements of high-precision IFOG. However, when the connection gap was welded by laser, as the fiber coil in state 3, the shielding effectiveness can be improved to 64 dB, and the magnetic field sensitivity of the fiber coil can be reduced to less than 0.000 4 (°)·h−1·Gs−1, which greatly improves the precision of the fiber coil in the magnetic field.
Axial Magnetic field sensitivity
of state 1 /(°)·h−1·Gs−1Magnetic field sensitivity
of state 2 /(°)·h−1·Gs−1Shielding effectiveness
of state 2Magnetic field sensitivity
of state 3 /(°)·h−1·Gs−1Shielding effectiveness
of state 3X 1.052 3 0.026 5 31.98 0.000 40 68.40 Y 0.584 4 0.018 1 34.83 0.000 31 64.70 Z 0.395 4 0.008 0 33.88 0.000 23 64.71 Notes: The fiber coil in state 1 was un-shielding; The fiber coil in state 2 was shielded by permalloy material, but the connection gap was not welded; The fiber coil in state 3 is shielded by permalloy material, and the connection gap was welded by laser. Table 2. Magnetic field sensitivities of the coil in different states
The bias of the IFOG in different temperatures is shown in Fig.7 and Tab.3. We can find that when the connection gap was welded by laser, the precision of the IFOG in different temperature can be improved by more than 7.5%.
States Uncompensated bias stability Compensated bias stability Connection gap unwelded 0.041 0 (°)/h 0.003 18 (°)/h Connection gap welded 0.036 5 (°)/h 0.002 94 (°)/h Performance improvements 11.0% 7.5% Table 3. Bias stability of the IFOG in the temperature of −40−60 ℃
Research on method of improving magnetic field adaptability of high-precision IFOG
doi: 10.3788/IRLA20200239
- Received Date: 2020-06-18
- Rev Recd Date: 2020-10-22
- Available Online: 2021-04-30
- Publish Date: 2021-04-30
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Key words:
- high-precision IFOG /
- magnetic field /
- connection gap /
- laser welding /
- de-twist
Abstract: The magnetic non-reciprocity error of fiber coil is one of the main factors that restrict the application of high-precision IFOG, and the error is related to the strength of magnetic field and the twist rate of fiber. The magnetic field sensitivity of fiber coil is more than 10 (°)·h−1·Gs−1 due to the twisting of the fiber, even if permalloy is used to shield the magnetic field, the shielding effectiveness can only reach about 30 dB, which cannot meet the requirements of high-precision IFOG. The influence of the connection gap between shielding materials on shielding effectiveness was analysed by an equivalent circuit model and finite element simulation, the influence of the twist rate on the magnetic field sensitivity was deduced by formula. Through these analyses, the improvements were proposed that changed the connection of shielding materials from screw connection to laser welding and made the fiber de-twist. Through the measurement of fiber de-twist, the magnetic field sensitivity of the fiber coil was reduced by 89.3%; Through the improvement of laser welding, the shielding effectiveness was improved from 31 dB to at least 64 dB, the magnetic field sensitivity was reduced from 0.026 5 (°)·h−1·Gs−1 to less than 0.000 4 (°)·h−1·Gs−1, and the bias stability of the IFOG in different temperature was improved by more than 7.5%. These improvements can improve the precision of the fiber coil in the magnetic field and temperature environment, meeting the performance requirement of high-precision IFOG.