On-orbit self-calibration method of non-coplanar gyros based on UDKF

For the on-orbit calibration problem of non-orthogonal gyros, the orthogonal gyros on-orbit calibration method used in flight was improved, and the non-coplanar gyros on-orbit sclf-calibration method was proposed. Firstly, the attitude propagating crror model of non-coplanar gyros was built, and then a UD decomposing Kalman filter (UDKF) was designed. The gyro constant bias was directly estimated, the gyro misalignment and scale factor crror was estimated indirectly on orbit with star tracker and gyro measurements. When the filter was designed, in order to realize the sequential processing of measurement update, the measurement noise dccoupling method was given. After filter designing, by using the vector norm constraint, the accuracy formulae were given to solve the misalignment and scale factor error from the indirect estimations. To illustrate the generality of this method, it was proved by formula derivation that the old method is a special case of this new method. In order to guide the design of calibration attitude maneuver, based on the analysis of observability, a simple rotation combination condition for system observability was given. Finally the mathematical simulation results show that this method is effective and the calibration accuracy of gyro misalignment is better than 0.01 degrees .