High-precision Hybrid Calibration Technology Of FOG-IMU

At present,after the high-precision FOG inertial measurement unit has been completed and delivered for a period of time after the factory calibration,the performance parameters of its internal inertial components may change.In addition,some system performance parameters such as internal arm parameters,time delay parameters,etc.are not taken into account in the factory calibration process.Therefore,this dissertation studies several major system p erformance parameters and proposes an off-site hybrid calibration method that includes system-level parameter error calibration,internal lever arm parameter calibration,and time delay parameter calibration.The purpose of the system-level calibration method is to reduce the reliance of the calibration process on the accuracy of the turntable.Therefore,a system-level calibration scheme based on the 18-position stop-and-turn roll path is proposed,and the results of the factory calibration can be accurately corrected.According to the basic measurement model of inertial and inertial errors,the Kalman filtering model is deduced at the system level,and the observability analysis and simulation tests under the uniaxial rotation path and the 18-position rolling path are performed respectively.Then the turntable test is performed.Finally,it is verified that the system-level calibration method under the proposed 18-position roll path can calibrate the accurate system parameter error.During the calibration test of the turntable,the fiber optic gyro inertial measurement unit always rotates along different axes to provide adequate excitation of the error parameters.Due to the presence of internal lever arm errors,frequent rotational movements can cause serious internal lever arm errors.In this paper,based on the traditional method of internal arm parameter calibration,an effective rocking rotation calibration scheme is designed.The rationality of the scheme is explained by theoretical study and compared with two different calibration paths.Both the observability analysis and the experimental results show that the proposed method can calibrate the parameters of the inner arm with higher accuracy.Finally,after the calibration results are compensated,the internal lever arm error is significantly suppressed.In an actual fiber optic gyro inertial measurement unit,there may be an asynchronous problem of the output signal time between each inertial device,especially in the environment of high dynamic rollover test,which will affect the speed update accuracy of the strap-down inertial navigation system.In this paper,the time-asynchronous errors between three accelerometers and gyros are fully considered.A time-delay parameter calibration method based on single-axis continuous rotation path is proposed.The Kalman filter is designed and the time delay parameter of effective calibration is designed.The simulation and turntable tests verify that the proposed scheme can accurately identify the three time dela y parameters between the accelerometers and the gyros,and finally realize the time synchronization of the system output signal,which will meet the application of high precision fiber optic gyro inertial measurement unit.