Abstract: The initial self alignment for a kind of spacecraft which requires autonomous navigation from the launch phase is studied in this paper. Three classical self alignment methods of SINS including analytical coarse alignment, compass alignment and inertial frame based alignment are presented and analyzed. Firstly, the adaptability of these different methods in different scenes is analyzed, and then the influence of the measurement error characteristic of IMU is studied. Finally, an improved gyro compassing alignment method adapted to periodic shaking base is designed to solve the self alignment in the environment of slightly shaking launch vehicle. Through the Monte Carlo simulation under different IMU measurement noise combinations, the results and accuracy of the gyro compassing alignment method and inertial frame based alignment method are numerically analyzed, which provides a basis for the scheme selection in engineering practice.

Key words: SINS self alignment, analytical coarse alignment, compass alignment, inertial frame base alignment