Stable Tracking Of Semi-strapdown Seeker Based On Biological Internal Model Theory

Seeker technology is critical for precise guided weapons.They can autonomously search,recognize and follow the target,and generate the command to guide the missile while flying towards the target.Therefore,the seeker performance can significantly affect the missile’s ability in a battle field.The semi-strapdown seeker is born to meet the demand of small guided ammunitions with high precisions.Choosing the bio-inspired ammunition as the research background,this paper focuses on the semi-strapdown seeker and other issues relative.Basing on the bio-inspired idea,which comes from the flying insects’ predation mechanism,this paper mainly focuses on dealing with two problems: one is the coupling between the stability control loop and the attitude loop of the missile body;and the other is that the strapdown stable control system cannot directly get the angular velocity of the antenna and the line of sight.This research is helpful for the development of the theory and technology related with bio-inspired ammunition.Major works are as follows.Firstly,the kinematic and dynamic model of semi-strapdown seeker is built for elaborating the difference between the strapdown based stability and rate gyro-based stability and analyzing how the coupling from the missile body and the seeker frame affect the frame angular velocity.Secondly the strapdown stability mechanism and the traditional angular velocity compensation method is introduced and the bio-inspired guidance method based on the predation of dragonflies are designed.The comparation of two different methods with same starting conditions proves that the bio-inspired method can realize the self-stabilization of the optical axis better and have better chasing results.Then the single-channel filter model is built for the angular tracking system.The line pf sight angular velocity is estimated based on a Kalman filter.The tracking error angle and the acceleration of the target after the filtering are got.Based on the biologic internal model and the predictive control theory,the generalized integration of the semi-strapdown seeker control and the attitude control is designed.Due to the existence of parasitic loop,the semi strapdown seeker is seriously coupled with the missile attitude,which affects the stability and tracking of seeker.These couplings can affect the stability and the guidance performance.The feasibility of the bio-inspired control method based on semi-strapdown seeker is proven.It is shown that the Kalman filter can accurately capture the angular velocity of LOS,which is useful for proportional navigation.The integrated design have better control performance.