Study on stability of strapdown seeker scale factor error parasitical loop

Strapdown seeker scale factor error will degrade the performance of the seeker. In order to analyze the effect of seeker scale error on parasitical loop stability and effective navigation ratio, in this paper the strapdown seeker scale factor error is analyzed and the model of the scale factor error is constructed, meanwhile the concept of the strapdown seeker scale factor error parasitical loop is presented. The effect of the scale factor error on the navigation ratio is analyzed and the plot of normalized effective ratio versus the equivalent scale factor error is given. Finally the stability of the strapdown seeker scale factor error parasitical loop is analyzed by employing the normalization method and Routh criteria. The critical stable boundary of the parasitical loop is obtained through digital simulation. The simulation results give the relationships between turning rate time constant T_a, guidance time constant T_g and the strapdown seeker scale factor error when the system is critical stable. Those research results are instructive to the missiles guidance engineers during the primary scheme design period.