Integration of RTK GPS and IMU for Accurate UAV Positioning - Integrasjon av RTK GPS og IMU for nøyaktig UAV-posisjonering
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Real-Time Kinematic GPS (RTK GPS) can provide centimeter accuracy and maybe used for high accuracy positioning of Unmanned Aerial Vehicles (UAVs).Inorder to compute its position a Global Navigation Satellite System (GNSS) receiverprocesses measurements of signals from GNSS satellites. The processing results ina delay before the position measurement is available to the UAV. If the UAV ishighly dynamic the delayed measurement will describe a past position, resulting in reduced accuracy. This thesis presents the hardware and software architecture of an integrated Real-Time Kinematic GPS/Inertial Navigation System (RTK GPS/INS) for UAV applicationsthat compensates for the time-delay. The RTK GPS system is constructedusing single-frequency GPS receivers and the open-source Real-Time KinematicLibrary (RTKLIB). The RTK GPS/INS navigation system is implemented in theDUNE(DUNE:Unied Navigation Environment)-framework running on the embeddedpayload computer of the UAV. The integration of RTK GPS and ineartial measurementsis performed by a nonlinear observer estimating the delayed states andrecovering the current states using inertial measurements. Hardware-in-the-Loopsimulations and experimental ights with the x8 Skywalker UAV are used to testthe navigation system.