Research On Passive Positioning And Tracking Of Pure Angle Targets For Single Unmanned Aerial Vehicles

Target passive tracking need not transmit electromagnetic wave,so that it has advantages on good concealment and strong anti-interference ability and so on.Passive tracking will be the development trend of target tracking in the future battle field.In the complex high-tech battles,direction angles of target are one of the most reliable parameters,so angle-only target passive tracking has been widely studied.Compared with multi-observers,passive target location based on a single observer has good flexibility,avoiding space-time registration and data fusion.In order to solve the problems including incomplete observability without distance measurement,difficulty on target location and the divergence of location,this paper proposes a new solution based on elevation information.Meanwhile,a single UAV is used as the observer,and design method on the optimal UAV maneuver Trajectories is also given.Above target location theory and optimal UAV maneuver strategy can ensure the existence and uniqueness of the target state parameters,and also can improve the accuracy of target location and tracking.Firstly,for getting the angles between target and UAV,a camera is used to capture target,and the direction angles of target are calculated by video and pictures processing and coordinate transforms.The experiment about angles resolving proves the correctness of above theory,which can provide accurate angles for angle-only target passive location.Secondly,aiming to the problem that lack of distance between target and UAV results in difficulty of target locating,this paper proposed that elevation data act as auxiliary information to locate target.For the target on plane,its location can be got from the space geometrical relationship between target and UAV,which is brief and clear,and is not affected by target motion forms.For the target on undulate terrain,gradient sampling along line of sight is proposed.Then,calculate the value difference between height of gradient point and the corresponding elevation,and the absolute minimum of differences is regarded as the passive target location.EKF has been used to tracking target and improve the accuracy of tracking.Finally,in order to improve accuracy and possible divergence problems,meanwhile,considering the effect of UAV maneuver on estimating target state,one-step optimal UAV maneuver strategy has been proposed.It is based on FIM determinant maximum index,and two optimal trajectory equations are also shown.Combing with the elevation data,the location and tracking results shows higher accuracy for both of static and moving target with optimal UAV maneuver strategy.Simulation and experiment results verify the effectiveness of the proposed algorithm,and the filter tracking curves are stable and convergence.