Abstract
Abstract. The demand for small Unmanned Aerial Vehicles (UAVs) is massively increasing these days, due to the wide variety of applications utilizing such vehicles to perform tasks that may be dangerous or just to save time, effort, or cost. Small UAVs navigation system mainly depends on the integration between Global Navigation Satellite Systems (GNSS) and Inertial Measurement Unit (INS) to estimate the Positions, Velocities, and Attitudes (PVT) of the vehicle. Without GNSS such UAVs cannot navigate for long periods of time depending on INS alone, as the low-cost INS typically exhibits massive accumulation of errors during GNSS absence. Given the importance of ensuring full operability of the UAVs even during GNSS signals unavailability, other sensors must be used to bound the INS errors and enhance the navigation system performance. This paper proposes an enhanced UAV navigation system based on integration between monocular camera, Ultra-Wideband (UWB) system, and INS. In addition to using variable EKF weighting scheme. The paper also investigates this integration in the case of low density of UWB anchors, to reduce the cost required for such UWB system infrastructure. A GoPro Camera and UWB rover were attached to the belly of a quadcopter, an on the shelf commercial drone (3DR Solo), during the experimental flight. The velocity of the vehicle is estimated with Optical Flow (OF) from camera successive images, while the range measurements between the UWB rover and the stationary UWB anchors, which were distributed on the field, were used to estimate UAV position.
Highlights
The demand of versatile small Unmanned Aerial Vehicles (UAVs) is increasing rapidly, due to the massive spread of applications that utilize such UAVs to accomplish different tasks in order to save cost, effort, time, or tasks that may expose people to danger
The camera is attached to the belly of the drone, the implemented Visual Odometry (VO) is based on the optical flow approach shown in (Heinrich, 2017), where features are detected in consecutive frames (30 FPS) through the Speeded Up Robust Features (SURF) detector (Bay et al, 2006), which has been chosen because of its low computational requirements
EXPERIMENT AND RESULTS The Flight extended for 186 seconds with 23 waypoints around the area of interest shown in Figure 3, the trajectory includes complex maneuvers to show the ability of the proposed approach to enhance the navigation performance during Global Navigation Satellite Systems (GNSS) signal outage even during harsh movements
Summary
The demand of versatile small UAVs is increasing rapidly, due to the massive spread of applications that utilize such UAVs to accomplish different tasks in order to save cost, effort, time, or tasks that may expose people to danger The Inertial Measurement Unit (IMU) used in this kind of UAVs (small/commercial) is based on low-cost Micro-ElectroMechanical Systems (MEMS) Since this kind of sensor typically accumulates a huge amount of errors during the navigation estimation process (mechanization), they can be used as standalone navigation solutions only for short time periods. (Tiemann and Wietfeld, 2017) integrated the Time Difference of Arrival (TDOA) through a tightly coupled scheme in a constrained indoor environment using three UAVs. The low power consumption and lightweight of UWB devices make them adequate to be used with small drones. This paper proposes the integration between a camera and a UWB system for outdoor UAV navigation when GNSS is not available, with variable weighting uncertainties EKF scheme This integration is investigated when the size of the UWB network is decreased by 33 % in order to reduce the overall cost of the system
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