Research On Relative Navigation Method Of UAVs Based On INS/VisNav

With the continuous development of science and technology,the function of the unmanned aerial vehicle(UAV)is more comprehensive and the application is more widely.The traditional single-drone mission model is difficult to adapt to the increasingly complex battlefield situation.Therefore,using multiple UAVs for cooperative formation is an important direction for the development of UAVs,and the relative navigation between UAVsis the key technology to support cooperative formation flight.In this thesis,the leader-follower formation is taken as an example,and the relative navigation method which based on the inertial navigation and VisNav is studied deeply.The main research contents are as follows:Firstly,investigate the research status of relative navigation at home and abroad,including relative navigation status,navigation filter status and nonlinear filter algorithm status,analyzes the advantages and disadvantages of relevant sensors,methods and applicable conditions,and gives the main content of the thesis.Secondly,the extended Kalman filter and cubature Kalman filter are studied in this thesis.The main steps of extended Kalman filter and cubature Kalman filter are given.According to the relative motion equation between the leader and the follower,the relative inertial navigation equation is established as the state equation.The measurement equation is founded according to the VisNav principle and the relative navigation state.Based on the state equation and measurement equation,the cubature Kalman filter algorithm is used to design the relative navigation filter.Finally,the relative navigation method based on multi-sensor information fusion is studied.Three different information fusion structures are given,including centralized,hierarchical and completely distributed.The information filtering theory is studied,and the cubature information filtering algorithm is deduced based on the spherical-radial cubature rule.Considering the wide application of GPS in UAVs,this thesis designs a relative navigation filter based on inertial navigation,VisNav and GPS using multi-sensor information fusion method.It not only improves the reliability of filter,but also reduces the relative navigation error.