Study On The Stability Of The Strapdown Seeker

It is urgent to cut the cost, reduce the scale and gain the autonomy of thetactical missile recently, so the implementation of the strapdown seekers becomesnecessary. However, with the implementation of the strapdown seekers, newproblem comes along compares to the traditional used gimbaled seeker:(1)Measurement of the angular velocity in the inertial reference frame is unable to getdirectly;(2) The coupling between the missile body motion and the detectorinterferes the guiding of the missile, causes unstable guidance;(3) Noise isgenerated from the differential measurement;(4) The estimation of the angularvelocity is difficult, which is essential for the proportional navigation.In the dissertation, first, the frame of the strapdown seeker is modeled toanalyze the coupling from the missile body to the frame and evaluate theinterference of the nonlinear moment to the frame angular velocity steady error;Second, the principle of the strapdown stability is introduced along with the angularvelocity compensation algorithm, which are applied in a simulation; Third, thematched filtering and differential velocity measurement algorithms are introducedto get the optimized matched filter, so the best performance of the system can beensured. The robust control method is also applied to prevent the system from therisk caused by the parameters uncertainty. Moreover, the angular position isprocessed by the differential tracking algorithm, the outputs are used in thecomparison of filtering capability among the Finite Impulse Response (FIR) filter,the moving average filter and the second order low pass filter; Finally, based onsingle channel tracking model, the angular velocity of the line of sight is estimatedby both the adaptive Kalman filter and the particle filter, the estimated results arecompared to provide better approach to the strapdown seeker tracking.The results demonstrate of the interference comes from the coupling momentbetween the missile body and the frame; and the matched filter, robust control,tracking differential algorithm and moving average filter are able to enhance thestability of the seeker; furthermore, compare to the adaptive Kalman filter, theparticle filter is a better approach for the strapdown seeker tracking. The algorithmsin the dissertation are useful for the implementation of the strapdawn seeker.