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初始对准时,通常是基于地球参考椭球,用正常重力公式计算重力矢量,而实际情况下地球内部质量分布不均匀,实际重力包含正常重力和重力扰动。重力扰动包括参考椭球面切线方向的分量(垂线偏差)和法线方向分量(重力异常)。研究重力扰动下的初始对准,导出了重力扰动下水平姿态误差角与垂线偏差大小等值。重力扰动下初始对准的方法是利用EGM2008地球重力场模型计算出对准点的重力扰动并从加速度计中剔除掉。仿真分析表明,补偿重力扰动后可提高初始对准精度。
The initial alignment is usually based on the Earth reference ellipsoid and the gravity vector is calculated using the normal gravity formula, whereas in the actual situation the mass distribution inside the Earth is not uniform. The actual gravity includes the normal gravity and the gravity disturbance. Gravitational disturbances include components (vertical deviation) and normal direction components (gravity anomalies) of the reference ellipsoid tangential direction. The initial alignment under gravity disturbance is studied, and the horizontal attitude error angle and vertical deviation magnitude under the gravity disturbance are derived. The initial alignment method under gravity perturbation is to calculate the gravity disturbance at the alignment point and remove it from the accelerometer using the EGM2008 Earth’s gravity field model. Simulation analysis shows that compensating for gravity disturbance can improve initial alignment accuracy.