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This paper presents a vision-based tracking system for marine surface objects utilizing images captured in a fixed-wing unmanned aerial vehicle (UAV) with a retractable pan/tilt gimbal. A formula for calculating the North-East velocities of objects detected in the images is derived. The formula utilizes optical flow (OF) and compensates for the UAV and gimbal motions. It can be used together with...
This paper describes a control approach for transitioning VTOL UAVs controlled by differential thrust, allowing to fly in all flight phases spanning a continuous transition between hover and cruise flight. A quaternion based attitude controller makes use of an additional reference frame that is rotated by the transition angle with respect to the body-fixed frame. This approach allows intuitive control...
There is strong interest in Micro Aerial Vehicle (MAV) control architectures which are able to systematically respect physical limitations of the plant. Nonlinear Model Predictive Control (NMPC) inherits the required constraint handling abilities and is easy to reconfigure in case of plant degradation. This work presents a promising cascaded control architecture for multirotors for the task to follow...
The communication link integrity of an Unmanned Aerial System (UAS) is influenced by a number of factors, the most relevant being antenna radiation pattern and gain, receiver sensitivity, output power, terrain relief, aircraft's attitude and trajectory, and frequency band. The constraints are especially severe in the context of beyond line-of-sight and low altitude flight plan. This work presents...
This paper presents the design and simulation of an energy-based control strategy to stabilize a quadrotor described with unit quaternions and their axis-angle representation. The mathematical model is based on Euler-Lagrange formulation using a logarithmic mapping in the quaternion space. The proposed solution introduces a new approach: a quaternion-energy-based control, which introduces an energy...
This work presents the modeling and control of an aerial manipulator based on a quadrotor with a robotic arm using the dual quaternion approach. First the kinematic model of the complete system is obtained using dual quaternions to represent multiple rotations and translations, then the dynamic model is developed via the Newton-Euler formalism. A position control law is used to stabilize the vehicle...
This work focuses on the remote sensing of thermal updrafts under cumulus clouds for glider UAVs. Previous remote estimation techniques assume unlimited thermal lifespans under the clouds. Naturally occuring thermals are however of limited duration which increases the risk of an outlanding when utilizing these methods. By observing the evolution of the cloud's diameter, human glider pilots draw conclusions...
High altitude platforms, also known as pseudo-satellites, are envisioned as unmanned aircraft flying at altitudes above 15 km to provide observation, remote sensing or communication services. A challenging yet recurring requirement for such aicraft is to be able to perform long-endurance missions over multiple days or even weeks. A sophisticated onboard energy management system including solar panels...
This paper presents a novel method for wind characterization and mapping by using an Unmanned Aircraft System (UAS). The generation of a wind map is vital in energy-efficient trajectory planning of efficient trajectories and dynamic soaring applications to detect the shear layer. Firstly, two methods to estimate the parameters that define an unknown wind field (wind speed and direction) by using a...
This paper investigates the aerodynamic performance improvement of the Hydra Technologies S4 Unmanned Aerial System using a morphing wing concept. A part of the wing's upper surface is morphed, as function of the flight condition, in order to increase the S4's lift-to-drag ratio. The wing airfoil shape optimizations are performed using a hybrid Artificial Bee Colony and Broyden-Fletcher-Goldfarb-Shanno...
Multi-rotor Unmanned Aerial Vehicles make use of multiple propellers, mounted on arms, to produce the required lift. This article investigates the influence on propulsion system efficiency in hover due to the configuration of these propellers. Influence of pusher or puller configuration of the propeller, number of blades, shape and dimensions of the arm, coaxial and overlapping propellers, is presented...
A cooperative aircraft differential game where an Attacker missile pursues a Target aircraft is addressed. The Target aircraft cooperates with up to two Defender missiles which are launched in order to intercept the Attacker before the latter reaches the Target. The results in this paper build on the solution of a three agent differential game, where the three players are the Target, the Attacker,...
Long-time planning horizons are required to safely navigate one vehicle in the presence of another, possibly non-cooperative vehicle. They give rise to computational issues preventing the real-time implementation of safe navigation algorithms. In this paper, we consider two nonholonomic vehicles, of which one (blue) has the goal to enter the “tail” of the other (red). Neither the goal nor the navigation...
The UAVs business experiences currently a strong growth in particular thanks to the popularisation of its mini class (e.g. DJI Phantom, Parrot Bebop…). Nevertheless, there is still a need for more capable aircraft, mainly in terms of payload and endurance, in both military and civilian markets. This type of aircraft is historically known as the tactical class, which is a compromise between the affordability...
This paper presents a novel obstacle avoidance scheme for UAVs. This scheme is based on the use of a technique recently developed by one of the authors, which is based on a transformation of a variable constraint into an input saturation. In the case of obstacle avoidance, this saturation is designed so as to ensure a safe trajectory around the obstacles, offering a proof of this desired behavior...
In this paper, we present two novel guidance laws for an unmanned aerial vehicle (UAV) equipped with a fixed camera to track a mobile ground target. The system dynamics is established in the level local coordinate frame, removing the need of converting the target location information to the global inertial frame. The first guidance law is developed using backstepping technique requiring the estimation...
In this paper, a novel PID gain update law using linear least squares regression is introduced as an adaptive control method for autonomous helicopters. In addition, prediction analysis is conducted for error dynamics of the closed loop system using recursive linear least squares regression. Combining these two concepts with classical PID controller, an intelligent PID controller is obtained. A flight...
Two missile guidance laws viz. Pursuit Guidance (PG) and Trajectory Shaping (TS), have been adopted to aggressively follow curved, compact trajectories using a quadrotor. The concept of virtual target navigation has been utilized to generate the required curved trajectories. Simulations and flight tests have been performed using a quadrotor and the performance characteristics obtained have been compared...
This paper presents a framework that integrates vector field based motion planning techniques with an optimal path planner. The main motivation for this integration is the solution of UAVs' motion planning problems that are easily and intuitively solved using vector fields, but are very difficult to be even posed as optimal motion planning problems, mainly due to the lack of clear cost functions....
An Unmanned aerial vehicle (UAV) guidance law is addressed as an optimal regulator (LQR) problem. An adaptive optimal path following nomenclature is derived and defined. The state weighting matrix of the LQR is defined in term of intrinsic parameter error thereby enabling the guidance law to regulate the UAV disturbance errors effectively. The state weighing matrix is tuned using a genetic algorithm...
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