针对四元数在飞行器姿态描述时存在冗余的问题，设计了把修正罗德里格参数（MRPs）作为描述姿态的一种全姿态描述方法，将加速度计和磁强计作为观测量，提出了基于平方根无迹卡尔曼滤波器(SRUKF)的姿态估计算法，针对外界环境对加速度计和磁强计的干扰问题，将专家系统引入SRUKF算法中，根据加速度及磁场信息实时调整滤波器的量测噪声矩阵，有效地提高了算法的抗干扰性。实验结果表明，该算法成功使系统的静态精度姿态角小于0.05°，航向角小于0.1°；动态精度姿态角小于0.5°，航向角小于1°，优化效果得到了明显改善。

In view of the shortage of redundancy when using quaternion to describe attitudethe Modified Rodrigues Parameters (MRPs)which is a threedimensional independent vectoris put forward for attitude estimation.The attitude estimation algorithm based on Square Root Unscented Kalman Filter (SRUKF) is established with the outputs of accelerometer and magnetometer as observation vectors.In order to avoid the accelerometer and magnetometer interference by environmentan expert system is introduced to the SRUKF algorithm.The expert system is designed to estimate the information of acceleration and magnetic field to adjust the measurement noise matrix.The experiment results indicate that the algorithm successfully makes the static attitude accuracy less than 0.05°and static heading accuracy less than 0.1°.And it makes the dynamic attitude accuracy less than 0.5°and dynamic heading accuracy less than 1°.The optimization effect is improved significantly.