AR-Marker/IMU Hybrid Navigation System for Tether-Powered UAV

Electrically powered unmanned aerial vehicles (UAV) are useful in performing inspection at various infrastructures or plants. A power supply through a tether cable is effective in extending flight time. During inspection activities, some or all satellites may be occluded. UAVs for inspection must be operated even in GPS-denied areas; therefore, a navigation system for GPS-denied areas is required. Depth information cannot be obtained correctly by a monocular camera. The ARToolkit, which is widely applied in augmented reality (AR), is not sufficient as a UAV navigation system. We have proposed a hybrid navigation method that integrates the ARToolkit and an inertial measurement unit (IMU). An analytic solution for both the worst and best estimation of yaw angle can be obtained by simple computation and helps remove outliers in measurements. From experimental results, it was proven that position estimation using the proposed method corresponded reasonably; however, it was necessary to correct the difference between the camera origin and the body’s center of gravity.