Research on effect of seeker disturbance rejection rate with phase lag on stability of parasitical loop

In order to analyze the effect of disturbance rejection rate on stability of the guidance system, the conception of seeker disturbance rejection rate parasitical loop was presented. A model of parasitical loop of seeker disturbance rejection rate was established based on the phase lag of seeker disturbance rejection rate. When the parasitical loop is feedforward and feedback, the stability zone of the parasitical loop is obtained based on the Routh criteria and the normalized model. The effect of phase lag on stability zone was analyzed in complex frequency domain. Simulation results show that the phase lag of seeker disturbance rejection rate reduces the stability zone. The smallest stability zone occurs at about -140° phase lag instead of -180°. As a result , it is helpful for the engineers at the preliminary stage of missile design.