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Unmanned Aerial Gliders form a subclass of fixed-wing Unmanned Aerial Vehicles which promise to offer sustained flight for a wide range of applications. Autonomous soaring allows these aircraft to detect and exploit rising air masses (thermals) without user input, which greatly simplifies their operation. While previous research has focused on the detection and exploitation of thermal updraft, the initial turn at the entry point into the thermal has been ignored. This paper explores the initial turn decision at the instant of thermal detection in order to improve soaring performance by flying directly into the thermal. A high-fidelity simulation of an off-the-shelf RC glider is constructed, along with the Weather Research and Forecasting model to capture realistic thermal convection. The effects of turn decisions on thermalling performance are examined through a large batch simulation on a Matlab/Simulink environment. Thermalling algorithms are subsequently integrated into the PX4 flight stack for Software-in-the-Loop simulations and flight tests using a Pixhawk flight controller. Simulated and experimental results demonstrate the importance of turn decisions for improved overall soaring performance. [ABSTRACT FROM AUTHOR]

This paper proposes a linear constrained model predictive control (MPC) to solve the path following problem for quadrotor unmanned aerial vehicles. In the controller, an augmented model is employed to completely eliminate the tracking error due to external disturbances imposed on the quadrotor. The proposed controller is capable of improving the trade-off between feasibility and performance of the system. By approximating the control input sequence in MPC with Laguerre function, the computational burden significantly decreases and the closed-loop performance improves. In addition, a prescribed stability procedure is applied to guarantee the asymptotic stability of the quadrotor error dynamics. Besides, the proposed method improves the numerical ill-conditioning problem in solving MPC, by modifying the position of the closed-loop system poles to lie inside the unit circle. In the simulation results, two scenarios for the quadrotor tracking problem are considered. The results demonstrate the capability and the effectiveness of the proposed control strategy in disturbance rejection, fast trajectory tracking and the quadrotor stability, while a desired performance is achieved. [ABSTRACT FROM AUTHOR]

Pose estimation for small unmanned aerial vehicles has made large improvements in recent years, leading to vehicles that use a suite of sensors to navigate and explore various environments. In particular, cameras have become popular due to their low weight and power consumption, as well as the large amount of data they capture. However, processing this data to extract useful information has proved challenging, as the pose estimation problem is inherently nonlinear and, depending on the cameras' field of view, potentially ill-posed. Results from the field of multi-camera egomotion estimation show that these issues can be reduced or eliminated by using multiple cameras positioned appropriately. In this work, we make use of these insights to develop a multi-camera visual pose estimator using ultra wide angle fisheye cameras, leading to a system that has many advantages over traditional visual pose estimators. The system is tested in a variety of configurations and flight scenarios on an unprepared urban rooftop, including landings and takeoffs. To our knowledge, this is the first time a visual pose estimator has been shown to be able to continuously track the pose of a small aerial vehicle throughout the landing and subsequent takeoff maneuvers. [ABSTRACT FROM AUTHOR]