Effect of seeker disturbance rejection rate parasitic loop on performance of optimal guidance law

In order to study the effect of a seeker disturbance rejection rate parasitic loop on the performance of the optimal guidance law, a practical guidance law is obtained based on the minimum theory under the main maneuver mode of an aerial target. Engineering application strategies of the guidance law are presented in terms of the information measured by the missile, such as the target maneuver estimate strategy, time to go filter and target and missile maneuver time constant equivalent measure, etc. A model of the parasitic loop is established for a typical radar gimbaled seeker. Then its characteristics of disturbance rejection rate transfer function as well as their effect on guidance parameters are analyzed. Under typical random inputs, the miss distance is compared using the ajoint method and the nondimensional method between the optimal guidance law and proportional navigation guidance law. The simulation results show that the optimal guidance law is more sensitive to the effect of the parasitic loop. When the disturbance rejection rate is under 2%, the miss distance of the optimal guidance law may be smaller than that of the proportional navigation guidance law, even if the estimate information is significant and correct. If there is something wrong in the estimate information, when the disturbance rejection rate can be kept much smaller, the performance of the optimal guidance law is still superior to the proportional navigation guidance law. Compared with the proportional navigation guidance law, if the optimal guidance law is used to improve the performance of the missile, then the index of the disturbance rejection rate should be much stricter to reduce the effect of the parasitic loop.