An attitude determination method based on UKF and Optimal REQUEST double filter

The Inertial Stellar Compass (ISC) attitude determination system, which is the combination of MEMS (Micro electromechanical Systems) gyros and CMOS APS star sensor, has low precision. Quaternion attitude estimate of UKF has higher attitude estimate precision, and it can also estimate gyro drift, but it needs high precision of attitude parameters as observes. Optimal REQUEST could deal with starlit vectors orderly and giving high precise of attitude parameters. For the mutual complement of two methods, the paper gets attitude parameters from Optimal REQUEST as observes to UKF and puts forward an attitude determination method based on UKF and Optimal REQUEST double filter. The results of simulation show that this method has higher precise of attitude estimate than EKF and Optimal REQUEST filter.