Research And Implementation Of UAV Terrain Avoidance Navigation Algorithm

With the rapid development of science and technology,unmanned aerial vehicles(UAV)are widely used in military and civilian field,with increasing flying activity and accident rate.The situation will affect not only economic losses,but also final result in the war seriously.To ensure UAV safety in various tasks,navigation system is needed.Terrain avoidance navigation system is one of navigation system.The system includes algorithms of terrain matching and terrain avoidance.Terrain matching algorithm is the core of UAV positioning,it can provide efficient and accurate location information.To ensure the safety of UAV flight,terrain avoidance algorithm can provide effective path of terrain,threats and no-fly zone.It is the key that UAV need high efficient terrain matching and terrain avoidance capability to improve the efficiency of mission.The dissertation try to find a method to solve barriers or threats for UAV flight.Under the bad situation,UAV can change its flight path with the different of geographical environment,and can also avoidance terrain effectively.Finally,UAV can adjust flight path,return to the original track or replan a new flight route.In order to achieve the functions described above,the dissertation includes following contents:1.For positoning accurately,UAV need navigation system help.However,GPS belongs to United States and Inertial Navigation(IN)system has error accumulation problem,so UAV need Terrain Aided Navigation System(TANS)help.The core of TANS is reliability of terrain matching algorithm.So the dissertation studied two classical terrain matching algorithms named TERCOM and SITAN,trying to find a way to combinate two of them and to assure that algorithms can still work correctly with bigger initial error.2.Assuming offline reference routes were known,UAV needed terrain avoidance path information after positioning.However,only offline reference routes can not ensure UAV flight safety,online reference routs was needed too.So the dissertation studied a terrain avoidance algorithm which was based on tree-structure search,and tried to improve the algorithm to long-range UAV missions with more efficient and reliable.3.Considering the advance collection of geographical information may not complete when dealing with offline maps information would make UAV encounter sudden threat in the flight.Only using online terrain avoidance algorithm might be unable to work at the time.Based on tree-structure-search terrain avoidance algorithm,this dissertation found a improvement to solve the situation of sudden threat.4.Based on the large number of geographic information provided by the platform of EV-GLOBE Three-dimension Visual System,this dissertation completed many software functions,including making maps digital,matching terrain,avoidencing terrain,displaying flight track.According to the experiment results,combination of TERCOM and SITAN terrain matching algorithms could find UAV position quickly,improved terrain avoidance algorithm based on tree-structure search could provide avoidance routes effectively,and finally UAV got the optimal flight path completely.