Effect of seeker disturbance rejection rate on stability of on-off control guidance loop

The influence of seeker's disturbance rejection rate on the stability of on-off guidance loop is analyzed. Firstly, a unified dynamics model for gyro-stabilized seeker and rate-gyro seeker is established by using equivalent transformation principle of loop. And then, equivalent Lure' model of on-off guidance loop with the isolation parasitic loop is built to analyze the stability of the on-off control system. It is concluded from comparisons that the describing function method is superior to Popov theory and simulation method in the aspects of system conservation and stability trend predication. So, the describing function method is utilized to analyze the stability of the parasitic loop. Furthermore, the influence of cable torque and friction torque on the stable range of parasitic loop under parameters of different vehicles and modulators is obtained. Finally, the lag compensation method is put forward for unstable parasitic loop to improve system's stability. Simulation results show that the limit cycle is not appeared again in the guidance loop under the vehicle's attitude disturbance. It avoids pulsed thruster repeatly switching. And, when the vehicle maneuvers to a track target, it saves fuel and assures the guidance accuracy simultaneously.