Research On Time Difference Location Methods Of Radar Signal Using UAVs

Unmanned aerial vehicle(UAV)plays an extremely important role in the current military warfare because of their low cost,zero casualties,flexibility and sustainable operations.The passive TDOA positioning system requires only a single receiving channel for each observation station,which can minimize the load requirements of the positioning system,and has high positioning accuracy.It is widely used in military fields such as electronic countermeasures.In this thesis,the problem of time difference location of radar signals based on UAVs is studied.The main work of the thesis is as follows:(1)For solving the nonlinear TDOA location equation,Chan algorithm and Taylor series expansion method are studied respectively.For UAV with station error,the CRLB bound is deduced and the influence of station error on TDOA positioning accuracy is analyzed.The two-step weighted least squares method and Taylor series expansion method with stations' position error are further studied.In addition,the influence of UAVs station layout,baseline length and UAVs number on positioning accuracy is analyzed by simulation,which provides a basis for the follow-up study of UAVs path planning.(2)For solving the problem of target location and tracking based on time difference in UAVs,Kalman filtering algorithm and unscented Kalman filtering algorithm are studied.Combining the real-time location algorithm with the non-linear filtering algorithm to locate and track the fixed and moving targets,the positioning accuracy is further improved.In addition,the non-linear filtering algorithm is improved to adapt to the location scene with site error.Finally,the influence of time difference measurement error,site error and UAV group track on positioning accuracy are analyzed by simulation,and the effectiveness of the improved algorithm is verified.(3)For solving the problem that the trajectory of UAVs affects the accuracy of passive TDOA location,a three-dimensional real-time trajectory planning algorithm for UAVs based on TDOA location is studied.Firstly,according to the maneuverability constraints of UAVs,a discrete model of route planning is established.The problem of route planning of UAVs is transformed into the optimization of flight state control variables for each UAV at each moment.Extended Kalman filter is used to optimize the differential evolution algorithm by minimizing the trace of weighted CRLB matrix.For UAV flight altitude constraint and UAVs cooperative constraint,the penalty fitness function should be constructed as the optimization index.Then,the three-dimensional real-time route planning process of UAVs based on TDOA location is given.Finally,the algorithm is simulated and compared with the location scenario where the UAVs keep the initial station layout and heading,which verifies the validity of the trajectory planning algorithm.