There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Classifications, applications, and design challenges of drones: A review

Proceedings of the fifth annual workshop on Computational learning theory

Nowadays, Unmanned Aerial Vehicles (UAVs) are used in many different applications. Using systems of multiple UAVs is the next obvious step in the process of applying this technology for variety of ...

https://www.worldscientific.com/doi/pdf/10.1142/S2301385020500090

Multiple UAV Systems: A Survey

Micro- and nano air vehicles are defined as “extremely small and ultra-lightweight air vehicle systems” with a maximum wingspan length of 15 cm and a weight less than 20 grams. Here, we provide a review of the current state of the art and identify the challenges of design and fabrication. Different configurations are evaluated, such as fixed wings, rotary wings, and flapping wings. The main advantages and drawbacks for each typology are identified and discussed. Special attention is given to rotary-wing vehicles (helicopter concept); including a review of their main structures, such as the airframe, energy storage, controls, and communications systems. In addition, a review of relevant sensors is also included. Examples of existing and future systems are also included. Micro- and nano-vehicles with rotary wings and rechargeable batteries are dominating. The flight times of current systems are typically around 1 hour or less due to the limited energy storage capabilities of the used rechargeable batteries. Fuel cells and ultra capacitors are promising alternative energy supply technologies for the future. Technology improvements, mainly based on micro- and nanotechnologies, are expected to continue in an evolutionary way to improve the capabilities of future micro- and nano air vehicles, giving improved flight times and payload capabilities.

/pdf/micro-and-nano-air-vehicles-state-of-the-art-4bdbqcldt3.pdf

Micro- and Nano-Air Vehicles: State of the Art

This paper focuses on the quadrotor drag coefficient model and its estimation from flight tests. Precise assessment of such a model permits the use of a quadrotor as a sensor for wind estimation purposes without the need for additional onboard sensors. Firstly, the drag coefficient has been estimated in a controlled environment via wind generator and motion capture system. Later, the evolution of the coefficient is observed for various mass and fuselage shapes. Finally, an estimation method is proposed, based on the least-squares optimization, that evaluates the drag of the quadrotor directly from outdoor flight data. The latter leads the methodology towards easier adoption in other researchers’ systems without the need for complex and expensive flight testing facilities. The accuracy of the proposed method is presented both in simulation, based on a realistic flight dynamics model, and also for real outdoor flights.

Evaluation of drag coefficient for a quadrotor model

An experimental measurement on propeller forces and moments at high incidence was introduced. Test apparatus and data reduction process was discussed. Two sets of propellers were tested in SaBRe low speed wind tunnel: Graupner E-prop was used to validate the test-bench against known experiment; The second case, consisting of 3D-printed propellers, demonstrated variations in propeller aerodynamic efforts produced at high incidence angle for various advance ratios and blade pitch angles. The test also highlighted the importance of 3 dimensional effects such as stall delay in estimating propeller forces and moments at high incidence angle.

/pdf/experimental-analysis-of-propeller-forces-and-moments-at-2vgu0gpso6.pdf

Experimental Analysis of Propeller Forces and Moments at High Angle of Incidence

Piecewise Polynomial Model Identification using Constrained Least Squares for UAS Stall

The aim of this work is to estimate the average wind influencing a quadrotor drone only based on standard navigation sensors and equations of motion. It can be used in several situation, including atmospheric studies, trajectory planning under environmental constraints, or as a reference for studying flights in shear layer. For this purpose, a small quadrotor drone with spherical shape has been developed. Flight data are recorded from telemetry during indoor and outdoor flight tests and are post-processed. The proposed solution is based on a calibration procedure with global optimization to extract the drag model and a Kalman Filter for online estimation of the wind speed and direction. Finally, an on-board implementation of the real-time estimation is demonstrated with real flights in controlled indoor environment.

https://journals.sagepub.com/doi/pdf/10.1177/17568293211070824

Estimating wind using a quadrotor

In this study, robustness of panel method based path planning algorithm under wind disturbances is evaluated experimentally. Panel method, borrowed from fluid dynamics domain, is a numeric tool for calculating the potential field around arbitrarily shaped objects. Resultant potential field can be used for generating collision free trajectories for uncrewed aerial vehicles with convergence guarantee. Robustness of the proposed method is demonstrated during indoor experiments with a wind generator creating wind speed up to 7 m/s and also during outdoor experiments with wind speeds ranging between 3 - 5 m/s. Experiment results suggest that panel method based path planning scheme maintains its obstacle avoidance property under wind disturbances. 

/pdf/experimental-evaluation-of-robustness-of-panel-method-based-1g5xg91k.pdf

Murat Bronz

Papers

Evaluation of drag coefficient for a quadrotor model

Experimental Analysis of Propeller Forces and Moments at High Angle of Incidence

Piecewise Polynomial Model Identification using Constrained Least Squares for UAS Stall

Estimating wind using a quadrotor

Experimental Evaluation of Robustness of Panel-Method-Based Path Planning for Urban Air Mobility