Research On Guidance And Control Of Guided Munitions With Strapdown Seekers

The advantages of a strapdown seeker to a platform seeker are its simple structure,low cost and small volume,which leading it to be the hot topic of research.Since the strapdown seeker is mounted on a missile directly,instead of outputting LOS rate which could be utilized in guidance law,it could only output body line-of-sight(BLOS)angle.Based on strapdown guided munitions and replaces the physical platform with mathematical platform,this dissertation focuses on the following topics: decoupled algorithm derivation,nonlinear filter LOS rate estimation,guidance information formulation on spinning missiles,terminal impact angle and strapdown seeker’s field-of-view constrainted guidance law design,application simulation on aerial guided bombs.Firstly,the working principle of the strapdown laser seeker is interpreted,the output characteristics of strapdown seeker is introduced,the mathematical model of the strapdown seeker and the kinematics and dynamics equations of guided munitions are established.When attacking a stationary target with a missile with a strapdown seeker,the LOS angle and angular rate are induced,the state equation and observation equation in LOS coordination are formulated;when the target is moving,consider its acceleration as part of the noise and project missile’s acceleration in LOS coordination to body coordination,then extends system state dimensions and introduces missile-target range and closing velocity to accurately estimate guidance information.Utilizes UKF and CKF to simulate the attacks to stationary ground targets and slowly moving target.The results show that both algorithms could effectively extract guidance information,the data reveals that the precision of CKF is higher than UKF.As to spinning missiles mounted on strapdown seekers,through coordinations transformations,the LOS angle and angular rate information is induced.The state and observation equations are formulated.With UKF and CKF,the simulations and data analysis results show that both algorithms could effectively estimate related information,the precision of CKF is higher than UKF.Meanwhile,the sample time and filtering time are also influencing the effects.The adjoint method is adopted to analyze PNG;to deal with the situations that the field of view of strapdown seeker is narrower than platform seeker,when utilizing impact angle constraint guidance law or in a large scale target maneuver,the seeker could possibley lose the target,a logic switching guidance law is established and accomplishes multi-constraints guidance law design.Taking the short time of missile’s terminal guidance period,to convergents guidance parameters to the expected values when or before the missile hits the target,the nonsingular FTSM is utilized and a finite time convergence impact angle and LOS angular rate constrainted guidance law is designed,then combines it with the logic switching guidance law.Combined with aerial bombs with strapdown seekers,the simulations of designed guidance laws attacking ground stationary and moving targets with CKF are conductd in Matlab.The results show that the nonlinear BLOS rate estimation and multi-constraints guidance laws satisfy related technical demands and are applicable to project practices.