Design And Implementation Of Guidance Laws For Intercepting Targets With Towed Decoys

The towed radar active decoy is an electronic device to provide radar jamming,and it is towed behind an aircraft via a fiber optic cable to protect aircraft from the tracking of attacking missiles.Basically,this kind of decoys relay and amplify the echo signals of targets,so the seeker of a missile often locks on the towed decoy or the energy center when the missile radar has detected signal sources of the target and the decoy at the same time,then a complete mission failure may result.Therefore,it is of great significance to carry out research in this field.This thesis establishes a relative motion model of the target and the decoy in three-dimensional space as the basis of the study at the very beginning.Then,two methods of designing guidance law against the target with a towed decoy are proposed from two different aspects.Firstly,the force analysis of the target-decoy system is carried out,and the Lagrange equation is used to establish the mathematical model of the relative motion of the target and the decoy in three-dimensional space.Meanwhile,the physical model of target and decoy is established by ADAMS.The simulation results of two models are compared to verify the accuracy of the mathematical model and the rationality of the assumptions adopted in the modeling process as well.The hypothesis lays a foundation for the following research.Secondly,a design method of guidance law based on information estimation is proposed.A high gain observer is used to estimate line-of-sight angle rate,and it is extended to estimate the acceleration of the target.Then the guidance laws are designed for the maneuvering target and the non-maneuvering target respectively,and they are implemented by using estimates of information obtained above.The simulation is conducted at the end to verify the accuracy of the information estimation.The last,the towed decoy is unable to provide radar jamming against the missile ahead of the target because of the decoy's conical blind zone.A variable structure guidance law is proposed to make missiles attack targets from the front hemispheres of the targets' directions.That is to say,it plans the trajectories of the missiles into the blind zones to avoid jamming.Then the navigation processes of attacking non-maneuvering targets with towed decoys in head-on and pursuit cases are simulated respectively.There is a saturated oscillation in acceleration command in pursuit case,and we analysis the reason of that and propose a method to solve the problem by using the composite guidance.The lead point proportional guidance law is designed for the initial guidance stage of the compound navigation process.The simulation of compound guidance law is conducted in the pursuit case again,and the simulation results verified the feasibility of the guidance law.