Post by christina on Mar 4, 2024 2:36:42 GMT -5
full text: www.ericcointernational.com/application/magnetic-sensitivity-of-fog-imu.html
Inertial measurement unit (IMU) is the key of position and attitude system to obtain high-precision position and attitude information and realize high-precision airborne Earth observation. IMU with high-precision fiber optic gyro (FOG IMU) is sensitive to magnetic field due to Faraday effect of fiber coil, and the performance parameters of FOG zero bias and drift are deteriorated, thus the performance of IMU decreases. For FOG without taking any measures, its zero bias sensitivity is 104 (°)/(h·T), which can meet the requirements of general low-precision inertial measurement systems, but typical high-precision inertial navigation systems (such as POS) require FOG zero bias sensitivity of 1 ~ 10 (°)/(h·T), because of this, to achieve high precision IMU with FOG (FOG IMU), some technical measures must be taken to reduce the magnetic sensitivity of FOG.
1. Methods to reduce magnetic sensitivity
In the development stage of FOG, the technical measures to reduce magnetic sensitivity are mainly depolarization technology and advanced loop winding technology. Single-mode fiber can achieve lower magnetic field sensitivity than the polarization-preserving FOG through depolarization technology. The polarization-preserving gyro can suppress zero drift well because of its large linear bifold beam relative to the circular bifold beam induced by magnetic field. However, the main axis of polarization-preserving optical fiber has slow rotation in the drawing process, and it will also lead to torsion when winding optical fiber coil. Therefore, the Faraday effect in polarization-maintaining fiber is not completely zero. Using advanced winding technology to reduce the residual torsion of the coil and effectively control the tensioning force during the winding process, it can improve the quality of the polarity-maintaining coil and reduce the magnetic sensitivity. In addition, multiple compensators can be configured in the FOG scheme, the combined magnetic sensitivity of the compensators can be used to eliminate the magnetic sensitivity of the coil, and the FOG magnetic sensitivity can be reduced by using a new type of optical fiber with less magnetic sensitivity.
Inertial measurement unit (IMU) is the key of position and attitude system to obtain high-precision position and attitude information and realize high-precision airborne Earth observation. IMU with high-precision fiber optic gyro (FOG IMU) is sensitive to magnetic field due to Faraday effect of fiber coil, and the performance parameters of FOG zero bias and drift are deteriorated, thus the performance of IMU decreases. For FOG without taking any measures, its zero bias sensitivity is 104 (°)/(h·T), which can meet the requirements of general low-precision inertial measurement systems, but typical high-precision inertial navigation systems (such as POS) require FOG zero bias sensitivity of 1 ~ 10 (°)/(h·T), because of this, to achieve high precision IMU with FOG (FOG IMU), some technical measures must be taken to reduce the magnetic sensitivity of FOG.
1. Methods to reduce magnetic sensitivity
In the development stage of FOG, the technical measures to reduce magnetic sensitivity are mainly depolarization technology and advanced loop winding technology. Single-mode fiber can achieve lower magnetic field sensitivity than the polarization-preserving FOG through depolarization technology. The polarization-preserving gyro can suppress zero drift well because of its large linear bifold beam relative to the circular bifold beam induced by magnetic field. However, the main axis of polarization-preserving optical fiber has slow rotation in the drawing process, and it will also lead to torsion when winding optical fiber coil. Therefore, the Faraday effect in polarization-maintaining fiber is not completely zero. Using advanced winding technology to reduce the residual torsion of the coil and effectively control the tensioning force during the winding process, it can improve the quality of the polarity-maintaining coil and reduce the magnetic sensitivity. In addition, multiple compensators can be configured in the FOG scheme, the combined magnetic sensitivity of the compensators can be used to eliminate the magnetic sensitivity of the coil, and the FOG magnetic sensitivity can be reduced by using a new type of optical fiber with less magnetic sensitivity.