In-Flight Calibration of Gyros and Star Sensor With Observability Analysis for SINS/CNS Integration

摘要

The in-flight or in-field calibration of gyro in terms of all-parameter errors and star sensor installation errors is vital for improving the hitting accuracy and quick reaction capability of the SINS/CNS Integration system for near-earth flight vehicles. This paper explores an in-flight or in-field decoupled four-position calibration method by analyzing the degree of observability of error states based on singular values. Using this approach, an effort is made to isolate individual error sources to prevent contamination by using the least number of tests. The observability matrix is decoupled into three categories of submatrix: the gyro-bias observability matrix, gyro-scale factor observability matrix, and the gyro-misalignments and star sensor installation error observability matrix. In this paper, it is suggested that the observability degree of gyro-bias is proportional to the integration time, while the other gyro errors and the star sensor installation errors are proportional to the angular increments. Covariance analysis with a Kalman filter is performed, which confirm these conclusions. Theoretical simulations showed a reduction in the gyro all-parameter errors and the star sensor installation errors variance and in the time required to achieve convergence with the angular increments of the three-axis direction in a few minutes.