Self-calibration Method of Circular Grating Error in Rotary Inertial Navigation

To investigate the impact of circular grating measurement errors on attitude output accuracy in rotary inertial navigation systems (INS), this paper analyzes the main error sources of circular grating in INS. Specifically, the coaxial error of circular grating and inertial measurement unit, as well as the installation eccentricity error of circular grating, are examined and their error models are presented based on their physical characteristics. Next, a self-calibration method for circular grating errors is proposed using the high-precision angle measuring ability of the laser gyro in the IMU. This method does not require any external equipment and utilizes inertial navigation itself. Calibration of the coaxial error of circular grating is achieved through the orthogonal characteristics of three gyros in the IMU, while calibration of the installation eccentricity error is accomplished using the high-precision angle measuring of the IMU. Experimental results demonstrate the effectiveness of this self-calibration method, reducing the measurement error of circular grating from 35" to 5". This level of accuracy meets the requirements for self-calibration in high-precision inertial navigation.