Hybrid unmanned aircraft can significantly increase the potential of micro air vehicles, because they combine hovering capability with a wing for fast and efficient forward flight. However, these vehicles are very difficult to control, because their aerodynamics are hard to model and they are susceptible to wind gusts. This often leads to composite and complex controllers, with different modes for hover, transition and forward flight. In this paper, we propose incremental nonlinear dynamic inversion control for the attitude and position control. The result is a single, continuous controller, that is able to track the desired acceleration of the vehicle across the flight envelope. The proposed controller is implemented on the Cyclone hybrid UAV. Multiple outdoor experiments are performed, showing that unmodeled forces and moments are effectively compensated by the incremental control structure. Finally, we provide a comprehensive procedure for the implementation of the controller on other types of hybrid UAVs.

Abstract-This paper presents an algorithm for solving the problem of tracking smooth curves by a fixed wing unmanned aerial vehicle travelling with a constant airspeed and under a constant wind disturbance. The algorithm is based on the idea of following a guiding vector field which is constructed from the implicit function that describes the desired (possibly timevarying) trajectory. The output of the algorithm can be directly expressed in terms of the bank angle of the UAV in order to achieve coordinated turns. Furthermore, the algorithm can be tuned offline such that physical constraints of the UAV, e.g. the maximum bank angle, will not be violated in a neighborhood of the desired trajectory. We provide the corresponding theoretical convergence analysis and performance results from actual flights.

Abstract-In this paper we propose an algorithm for stabilizing circular formations of fixed-wing UAVs with constant speeds. The algorithm is based on the idea of tracking circles with different radii in order to control the inter-vehicle phases with respect to a target circumference. We prove that the desired equilibrium is exponentially stable and thanks to the guidance vector field that guides the vehicles, the algorithm can be extended to other closed trajectories. One of the main advantages of this approach is that the algorithm guarantees the confinement of the team in a specific area, even when communications or sensing among vehicles are lost. We show the effectiveness of the algorithm with an actual formation flight of three aircraft. The algorithm is ready to use for the general public in the open-source Paparazzi autopilot.

This study presents the effort given for the first prototype of a Long Endurance Mini UAV concept called Eternity. A multi-disciplinary conceptual aircraft design program called CDSGN is developed and used for the design of the Eternity. Unlike the traditional design methods that uses statistical data from the previous well-flown aircrafts, CDSGN analyses numerous aircraft candidates and simulates each candidate for the given mission definition and outputs the corresponding performance. The unique property of the presented design methodology comes from a computationally fast and physically accurate modelling of the aerodynamic characteristics of each candidate by using a modified version of a vortex lattice program called AVL from Mark Drela. Two types of configurations have been analysed for the Eternity design, conventional and flying-wing. A wide envelope of variable design parameters used for both configurations such as wing surface area, cruise speed, battery capacity, different airfoils, etc... Integration of solar cells, and the management of solar energy is also considered for every candidate. Only the wing span size has been limited to one meter. Additionally, the on-board avionics and payload weights and sizes are fixed for every candidate as they are independent of the design. Analyses by CDSGN concluded the dominance of the conventional configuration for the given long endurance mission performance both on solar and nonsolar conditions. Optimum wing surface area and the on-board battery energy found interactively by a post-filtering program developed in-house. A custom airfoil family, transitioning along the span, have been designed specifically for the corresponding local Reynolds number for specific spanwise locations. A wind-tunnel campaign is performed with a full-scale model and first flight tests have been performed in order to show the feasibility of long endurance flights. INTRODUCTIONEndurance performance enhancement of mini and micro UAVs has been a common interest which relies on many aspects of the design. Traditional conceptual design methods such as Raymer [9] and Roskam[10] generally leads the UAV design to a safe and robust selection which is not always sufficient to push the performance to its limits. The challenge of designing a mini-UAV for longendurance mission requires to think out of the box for the for the design method.The multidisciplinary nature of UAVs demand for a better understanding of the interactions between each discipline. Modeling of these interactions physically accurate and yet computationally fast becomes the main challenge for a new design method.This study will present the design optimization of a one-meter UAV, called Eternity, which shows the feasibility of an electric powered Long-Endurance MAV concept. The particular interest is on the developed CDSGN conceptual aircraft design tool specialized on MAV scale. Each of the subsystems (e.g. aerodynamics, structure, propulsion, control,...) modelled seperately in order to see their final effect on the p...

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