Optical axis stabilization of semi-strapdown seeker based on disturbance observer

Based on the kinematics of semi-strapdown seeker, the framework coordinate of the seeker is established. The optical axis stability equation of semi-strapdown seeker is deduced by using attitude transformation matrix. Then, the stability control principle block diagram of semi-strapdown seeker is shown based on the stability equation. The main factors that influence the stabilization precision are pointed out, such as friction disturbance, velocity-measuring noise and missile disturbance. In order to improve the stabilization precision, disturbance observer was proposed in semi-strapdown seeker stability control. The low frequency external disturbance and high frequency velocity measurement noise are effectively restrained by the disturbance observer as shown in hardware-in-loop simulation, and optical axis stabilization precision is improved nearly 20 times and 5 times due to two different frequencies with same amplitude.