Study On Error And Compensation Methods Of Input Axis Misalignment Of FOG

Fiber optic gyroscope as a solid-state instrument has a lot of advantages such as long service life,light quality,small size,large dynamic range,wide precision coverage,impact resistance,etc.Because of these advantages the fiber optic gyroscope has become an ideal inertial device which can be widely used for new generation of Strapdown Inertial Navigation System(sins)and other applications.Along with the precision of fiber optic gyroscope,the stability of zero bias and scale factor has reached a higher level;therefore the effect of input axis misalignment angle of FOG is becoming increasingly prominent.Theoretical analysis and mathematical simulation show that 1.5 arc minutes of input axis misalignment angle drift(changed by temperature change)can lead to 0.0066 ° / h test error of bias,0.0123 ° / h test error of bias position,0.1 PPM of scale factor error,more than 1 arc minutes of the initial alignment error and Navigation positioning error with time exponential growth.Therefore,in order to enhance the level of optical fiber gyro and navigation accuracy effectively,the misalignment error of the input axis of FOG is studied in this paper.First,the thesis theoretical deduces the misalignment angle caused by spiral winding fiber ring.Through the analysis,we can conclude that the ideal quadrupole symmetric winding will not produce misalignment angle,many technological problems are the main cause of the misalignment Angle.Through theoretical analysis,we can take effective measures to reduce the misalignment error in production process.In the current environmental factors for application,temperature,stress release and vibration will cause misalignment angle error.Although irradiation and magnetic field will cause great influence to zero bias and scale factor,they won't produce misalignment angle error.Secondly,the paper analyses the influence of misalignment angle by theoretical analysis and mathematical simulation.The results showed that the input axis misalignment angle will not only seriously affect the accuracy of IMU,the performance of high precision fiber optic gyro will also be affected.Finally,this paper studied the suppression method of misalignment angle and the drift.Based on the current research,we continue the compensation methods for temperature error of input misalignment angle of FOG,analyzed its physical meaning and method error.We used stepwise regression analysis and experimental data to get the model of misalignment angle error.The compensation experimental results proved that the method is effective.However,this kind of compensation method requires three orthogonal axes angular velocity information as compensation input.Therefore the method has some limitations because it cannot be used for single axis fiber optic gyroscope.At present,the single axis fiber optic gyroscope is usually used for attitude measurement.In order to improve the accuracy for attitude measurement,this paper deduced a kind of method specially used for single axis fiber optic gyroscope.The study not only proved the feasibility for the compensation method but also pointed out the difficulties encountered in the application and the solutions.This paper showed that research indepth on the misalignment angle can help us get a comprehensive understanding on misalignment angle and its drift.It also can help us restrain the misalignment angle and its drift of FOG and improve the performance of FOG as well as the accuracy of IMU.