Study On UAV Differential GNSS/SINS Combined Positioning

As a new high-tech,the unmanned aerial vehicle(UAV)has the advantages of competitive price,small size,light weight and the ability of low-altitude flight and no site limitation.By such advantages,UAV has become more and more popular in people's life and can be seen in many applications,such as aerial photogrammetry,inspection lines,agricultural plant protection,police reconnaissance,forest fire monitoring and so on.With the increasing number of industrial applications of UAV,Its existing integrated navigation and positioning methods can't provide the high-precision positioning required by industry applications.Therefore,it is necessary for UAV to conduct an in-depth study on the GPS/INS integrated navigation and positioning system and to improve the accuracy of navigation positioning.In order to follow the cutting edge of science and technology,the laboratory has purchased some UAVs for aerial photogrammetry.This paper takes the small electric fixed-wing UAV as the research object.The main research focuses on the GNSS and SINS of the UAV,attitude measurement and IMU inertial sensor error analysis,GNSS/SINS combined navigation positioning technology and positioning accuracy of UAV.Following is the main tasks:(1)Study on the principle and accuracy of the GNSS navigation and positioning of the UAV.The coordinate system of four GNSS is introduced and the mathematical conversion formula between each coordinate system is deduced.The error term of GNSS navigation is analyzed and the corresponding error correction method is proposed.The mathematical principle of single-point positioning used on UAV by GNSS pseudo-range is deduced.In order to improve the positioning accuracy of the GNSS navigation of UAV,a new method has been researched,which used the double-difference pseudo-range positioning.(2)Study on the UAV pose attitude measurement and airborne IMU error analysis.The four coordinate systems commonly used on UAV strap-down inertial navigation is introduced and the conversion formula between coordinate systems is deduced.The navigation equation of UAV SINS in geocentric inertial coordinate system,geocentric solid coordinate system and local horizontal coordinate system is introduced.The decomposing process of the UAV SINS navigation equation in the geocentric solid coordinate system is derived,and the conclusion that the UAV inertial sensor error causes the UAV pose measurement divergence is obtained.Then,the error term of the UAV inertial sensor is introduced.The Allan Variance used to identify the accidental error of the IMU's gyroscope and accelerometer is proposed.(3)Study on the principle and precision of GNSS/SINS combined navigation and positioning.The structure of GNSS/SINS loosely combined extended Kalman filter is designed and the UAV flight data is used to verify the accuracy of this algorithm.The GNSS/SINS tightly combined extended Kalman filter based on the double difference pseudo-range and the double difference pseudo-range rate is proposed.The experimental results showed that the DP-DPR algorithm can improve the accuracy of UAV combined navigation positioning.