New method of initial alignment with rotary-static process for rotary rocket

Considering from cost, the SINS of the rotary rocket is composed of low or medium precision gyroscope, so traditional methods are difficult to meet the requirements on alignment accuracy. A non-linear alignment method of rotating modulation for initial alignment is proposed based on the characteristics of the rotary rocket. Using this method, the random drifts of the Y-axis and Z-axis gyros get modulated, and the alignment accuracy can be improved. Because the gyro drifts can not be estimated simply through rotating modulation alignment, a new scheme of rotary & static initial alignment is put forward. In static alignment progress, the drifts of gyros can be well estimated by using the result of rotation alignment progress. The simulation results show that the attitude angle error of the SINS consisting of two 0.2 (°)/h gyros and one 0.01 (°)/h gyro is no more than 0.05° within 230 s after alignment, and the drifts of three gyros can be well estimated. This scheme is can be used in engineering practice.