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We present a two step path planning algorithm for unmanned aerial vehicles (UAVs) with kinematic constraints in the presence of polygonal obstacles. We use a visibility graph representation for the environment and a Dubins vehicle approximation to model UAV kinematics. A modified Dijkstra's shortest path algorithm is developed as first step of our approach to plan paths for a UAV. The algorithm in...
This paper outlines a method of applying a linear disturbance observer to a small Unmanned Aerial System (UAS) to reduce the influence of unpredictable gusts on the non-linear aircraft dynamics. This work aims to show that by using a linear state-space model it is possible to estimate external disturbances and use the available control surfaces to alleviate the influence of gusts on aircraft dynamics...
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...
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 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...
A decentralized controller for target tracking and obstacle avoidance for a multi-agent system is proposed. The controller is based on a navigation function which is composed of a goal function, as the D-optimality criterion of the Fisher information matrix, and a constraint function, which generates repulsive force to the agents near the obstacle. The multi-agent system is modeled as a graph and...
In this paper, Aircraft Dynamics Model (ADM) augmentation for Remotely Piloted Aircraft System (RPAS) navigation and guidance is presented. This approach provides additional information suitable to compensate for the shortcomings of vision based navigation sensors and Micro-Electromechanical System Inertial Measurement Unit (MEMS-IMU) sensors for attitude determination tasks. The ADM virtual sensor...
Modeling and identification of an aerial vehicle will allow engineers to design and implement guidance and control systems using the mathematical model acquired on flight. Using the mathematical model, several improvements and benefits shall be obtained, such as designing control subsystem using Modern Control Theory; the expected results at the workbench test will correspond more accurately to the...
Unmanned stratospheric aircraft capable of staying aloft for long periods of time have become a topic of interest in the past years. Several problems are still to be solved to allow for a profitable commercial use of such aircraft. The inherent lightweight design leads to fragile structures with low payload capacities and a high wind sensitivity. The weather dependence significantly reduces the system's...
A system of networked computer components is described allowing realistic simulation and performance assessment of see-and-avoid algorithms for unmanned aircraft systems (UAS). Due to its realistic physics engine and relatively open architecture, the X-Plane flight simulator is adopted to simulate computer-generated traffic or an aircraft controlled by a human pilot. Using the UDP interface in X-Plane,...
Sense and Avoid (SAA) has been identified as one of the crucial technologies for UAV safety flight. The SAA systematic design is to develop a system with sensor configuration and SAA algorithms. Normally, the SAA system integration and test can be both expensive and dangerous without carefully system and algorithms development. In this paper, we proposed a software based SAA simulation framework for...
We propose to estimate steady and turbulent wind velocities and aerodynamic coefficients of a fixed-wing Unmanned Aerial Vehicle (UAV) by using frequency separation as well as kinematic, aerodynamic and wind models combined in an Extended Kalman Filter (EKF). With these estimates it is possible to calculate the angle of attack and the magnitude of the airspeed. Avoiding the need for prior knowledge...
This paper presents linear system identification results using noisy data from a six-degree-of-freedom aircraft simulation and data obtained from flight test of an Unmanned Aerial System using the recently developed novel Artificial Neural Network System Identification algorithm. The method uses an artificial neural network with a single input layer and single output layer to learn the elements of...
In this paper, a robust altitude control scheme is proposed for a mini-Quadrotor UAV system based on sliding mode controller with an integral action to eliminate the steady-state error induced by the boundary layer in order to achieve asymptotic convergence to the desired altitude with continuous control input. The proposed integral sliding mode controller is chosen to ensure the stability and robustness...
In this paper, we investigate the problem of the dynamics of a quadrotor unmanned aerial vehicle undergoing impact with its environment. This work is motivated by the fact that operation of UAVs (manual or autonomous) carries with it a significant risk of collision with surrounding objects, particularly in unknown, unstructured environments. To make small UAVs more viable and expand their autonomy,...
Time-domain aircraft system identification is applied to flight test data obtained using a motion capture system. Longitudinal aerodynamic force and moment time histories are obtained using the estimation-before-modeling approach, in which forces and moments are modeled as Gauss-Markov processes and estimated concurrently with the aircraft state histories using an extended Kalman filter. Quasi-steady...
Modern navies perform various missions such as maritime security, maritime interdiction, and counter piracy operations in addition to their traditional wartime duties. However, most warships are not built flexible enough to conduct these tasks. Unmanned Aircraft Systems (UAS) increase the flexibility of the warships and enhance mission success. The capabilities of the UAS determine how effective the...
This paper considers the problem of integrating unmanned aircraft into low altitude airspace above urban environments, including major terminal areas and helicopter landing sites. A simple set of data-driven modelling techniques are used to explore, visualise and assess existing air traffic in a manner more informative to the unmanned aircraft community. First, low altitude air traffic data sets (position...
From the beginning of 21th century, the quantities and types of Unmanned Aerial Systems (UAS) have grown enormously and they become to boost substitution for the manned systems. UAS are creating advancement with a massive potential to change military operations and also enabling the new civilian applications. The vital issue for the airspace designers and managers is how to integrate manned and unmanned...
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