本文以姿态误差四元数与陀螺漂移误差之间的关系为基础，构建了系统状态方程；
The state equations of the system are established on the basis of the relation between attitude error quaternion and the gyro drift.
使用四元数的第二个理由，就是其可实现两个状态间的平滑插值。
The second argument that is commonly given for the use of quaternions is the possibility of smoothly interpolating between two orientations.
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