Performance Improvement of Small UAVs Through Energy-Harvesting Within Atmospheric Gusts

Fixed-wing mini aerial vehicles usually at low altitudes often exposed to turbulent environments. Gust soaring is a flight technique of energy harvesting in such a complex and stochastic domain. Presented work shows the feasibility and benefits of exploiting non-stationary environment for a small UAV. Longitudinal dynamics trajectory is derived showing significant benefits in extended flight with sinusoidal wind profile. Optimization strategy for active control has been performed with the aim of obtaining most effective set of gains for energy retrieval. Moreover, three-dimensional multi-point model confirmed feasibility of energy harvesting in a more complex spatial wind field. Influence of unsteady aerodynamics is determined on overall energy gain along the flight path with active proportional control. Most contributing aerodynamic parameters are identified and suggested as basic objective function of an UAV design for energy harvesting in gusty environment. In addition, passive approach of control related to structural dynamics is investigated, pointing out its potential and possible improvements with aeroelastic tailoring

Performance improvement of small Unmanned Aerial Vehicles through gust energy harvesting

Fixed-wing miniature aerial vehicles usually fly at low altitudes that are often exposed to turbulent environments. Gust soaring is a flight technique of energy harvesting in such a complex and stochastic domain. The presented work shows the feasibility and benefits of exploiting a nonstationary environment for a small unmanned aerial vehicle. A longitudinal dynamics trajectory is derived, showing significant benefits in extended flight with a sinusoidal wind profile. An optimization strategy for active control is performed, with the aim of obtaining the most effective set of gains for energy retrieval. Moreover, a three-dimensional multipoint model confirms the feasibility of energy harvesting in a more complex spatial wind field. The influence of unsteady aerodynamics is determined on the overall energy gain along the flight path with active proportional control. The aerodynamic derivatives describing the contribution to lift by a change in angle of attack and elevator deflection are identified as the most contributing aerodynamic parameters for energy harvesting in a gusty environment, and are therefore suggested as a basic objective function of an unmanned aerial vehicle design for such a flight strategy

Application of a Switching Control Strategy to Extract Energy from Turbulence by a Fixed-wing UAV

The objective of this paper is to design a control law to allow a small fixed-wing Unmanned Aerial Vehicle to extract energy from atmospheric turbulence. From literature data the properties of atmospheric gusts at low altitude are discussed and a single point measurement is proved to be representative of the wind field. The longitudinal flight dynamics of the aircraft is analyzed and the phugoid mode is found to be the main driver of the energy extraction process. A switching controller that places the poles of the phugoid mode depending on the instantaneous variation of energy of the aircraft is designed. Statistical simulations show an increase of energy of the aircraft when this strategy is applied

Bioinspired Energy Harvesting from Atmospheric Phenomena for Small Unmanned Aerial Vehicles

This Paper discusses energy harvesting from atmospheric phenomena for small unmanned aerial vehicles, theoretically through simulations and practically through experimental flights. A comparison between different scenarios for flight within the sinusoidal wind profile is presented. A significant improvement in performance with active control of command surfaces has been found for an energy-harvesting mode when compared to autostabilization or fixed-stick flight. Moreover, a detailed decomposition of the stochastic wind profile generated from the Kaimal spectrum has shown which frequencies and magnitudes of wind time series have the highest contribution to the energy-transfer process. It is found that wind profiles with higher turbulence intensity potentially provide more energy for transfer to the aircraft. Furthermore, the Paper reveals a biologically inspired sensory system for wind field estimation. It describes the necessary equipment and control algorithms for the exploitation of atmospheric energy. Initial flight tests were performed to determine the average power consumption of the motor for altitude hold tasks and to evaluate the performance of sensors. Moreover, additional flights for autonomous exploitation of several atmospheric phenomena are presented and analyzed

Propulsive Performance for an Oscillating Airfoil Applied to Mini Air Vehicles

In the present work, the optimal control to maximize the energy harvesting through a sinusoidal vertical gust profile is investigated through 2D URANS simulations and wind tunnel tests of NACA 0015 wing. The control is defined by a harmonic pitching motion of the wing, with the main objective to determine the optimal control parameters represented by the optimal pitch amplitude and phase shift that maximize the energy harvesting efficiency. The computational fluid dynamics (CFD) based on the k-omega -SST turbulence model is implemented to find the optimal control parameters for a simultaneously heaving and pitching 2D wing. For the experimental investigation, a wind tunnel model is manufactured and used to perform the wind tunnel tests to prove the energy harvesting concept and validate the obtained CFD results. Since it wasn't feasible to generate sinusoidal vertical gust in the wind tunnel, the gust effect is modeled by a sinusoidal heaving motion of the wing. A robotic arm is used to perform the simultaneous heaving and pitching motions of the wing. The numerical results showed the significant effect of the control activation to increase the energy harvesting where an optimal efficiency of 67 % is achieved at a gust amplitude of 0,5 m/s and frequency of 0,4 Hz. It was also found that an increase in the amplitude of the sinusoidal gust profile brings significant increment in the amount of energy harvested. Wind tunnel tests proved the concept of energy harvesting and exhibit the same trends of efficiency variation with pitch amplitude as that obtained through the numerical simulations. The obtained results showed that the energy harvesting flight technique is very promising regarding the improvement of the performance of mini-UAVs

Bioinspired wind field estimation—part 1: Angle of attack measurements through surface pressure distribution

One of the major challenges of Mini-Unmanned Aerial Vehicle flight is the unsteady interaction with turbulent environment while flying in lower levels of atmospheric boundary layer. Following inspiration from nature we expose a new system for angle of attack estimation based on pressure measurements on the wing. Such an equipment can be used for real-time estimation of the angle of attack during flight or even further building of wind velocity vector with additional equipment. Those information can find purpose in control and stabilization of the aircraft due to inequalities seen by the wing or even for various soaring strategies that rely on active control for energy extraction. In that purpose, flying wing aircraft has been used with totally four span-wise locations for local angle of attack estimation. In-flight angle of attack estimation from differential pressure measurements on the wing has been compared with magnetic sensor with wind vane. The results have shown that pressure ports give more reliable estimation of angle of attack when compared to values given by wind vane attached to a specially designed air-boom. Difference in local angle of attack at four spanwise locations has confirmed spatial variation of turbulence in low altitude flight. Moreover, theoretical law of energy dissipation for wind components described by Kaimal spectrum has shown acceptable match with estimated ones

Avian-inspired energy-harvesting from atmospheric phenomena for small UAVs

Fixed-wing small, unmanned aerial vehicles (SUAVs) usually fly in atmospheric boundary layers that are often under the influence of turbulent environments. Inspired by nature's flyers, an application of an energy-harvesting flight strategy for increasing the energy state of the aircraft is presented. This paper provides basic longitudinal flight dynamic model exposing the physics behind the process. It shows significant power savings in flight with a sinusoidal and stochastic wind profile with active control of energy-harvesting. The active control based on optimized proportional gains was implemented for energy extraction from realistic atmospheric conditions, leading to significant energy savings for a 'bird-sized' vehicle. The paper reveals the equipment and necessary preparations for the flight test campaign. Moreover, it describes the design of a custom controller and its calibration in the wind tunnel against roll movements during pitching maneuvers. Finally, it investigates the benefits and potential of the automated process of energy-harvesting with simple proportional control through flight tests in a turbulent environment, validating the concept through the increased energy state of the aircraft

Local guidelines for drug treatment of patients with covid-19

© 2020, Serbian Medical Society. All rights reserved. Objective. Until now, there have been no guidelines for the use of drugs in patients with COVID 19 in the Republic of Serbia that have been authorized and published in the professional or scientific literature, or on the official websites of the Ministry of Health or healthcare institutions. The aim of this paper is to present a local guideline for the use of drugs in patients with COVID 19 and the process of its development and adoption. Methods. The guideline proposal was prepared by a working group based on the results of a systematic research of the medical literature, and quality control of found publications from the category “clinical practice guidelines”. The proposal of the working group was considered and adopted at the sessions of the Drug / Therapeutics Committee and the Quality Assurance Committee of the University Clinical Centre Kragujevac. Results. The guideline's recommendations are based on the type of patient, and all have the same degree of recommendation and the same quality of evidence on which they are based. Patient types are formed according to the severity of the disease and the need for respiratory support, as well as according to the risk of secondary bacterial infection. Conclusion. The local guideline to the use of drugs in patients with COVID 19 was developed and adopted in a short period of time, primarily due to the need for its urgent use. A revision of this guide is planned after 6 months from the moment of adoption

Assessing the Impact Fracture Method: Experimental Approach to the Functional Analysis of the Pointed Tools from the Mousterian Layers of Riparo Tagliente Rock Shelter

The aim of this research was to obtain an insight into the complex system of variables of impact fracture propagation without ignoring the non-impact damage. Using experimental approach, crucial data was collected that was necessary for the reliable interpretation of the damage that was further used for the interpretation of the damage identified on the pointed tools from Riparo Tagliente, and bringing up conclusions of their possible functionality. By adapting the experimental variables as close as possible to the variables of the archaeological material from Riparo Tagliente, four experiments have been executed. The first experiment was a hunting simulation using Mousterian points that were hafted into the foreshaft using two hafting approaches, vertical and diagonal, and were propelled into the dead animal target. Obtained results enhanced the reliability of the interpretation of the damage and establishing its causation on the archaeological material. Knapping damage was identified on the experimental points used in the first experiment, therefore the second experiment was established and executed in order to observe the variations and causations of the fractures that could be caused by knapping. The third experiment was also a hunting simulation that was executed to obtain an insight of the impact fractures propagation using Levallois points with slightly different hafting approach than the one that was used in the first experiment. The reliability of the results obtained by the third experiment was questioned because of the modern equipment usage and the scarce number of the experimental samples. Non-impact damage that was identified on the pointed tools from Riparo Tagliente was not ignored and the fourth experiment was executed for this purpose. The aim of the fourth experiment was getting an insight into the edge damage patterns that could be formed on the pointed tools by using them in cutting, scrapping and chopping activities. The results improved the interpretation of the edge damage patters identified on the pointed tools from the site of Riparo Tagliente. Using all of the experimentally obtained data the possible functionality of the pointed tools from Riparo Tagliente was established.It is concluded that the pointed tools from Riparo Tagliente were used as multiple functionality tools. Furthermore this research proposed that it is necessary to improve the methodology of the impact fracture research in order to avoid the further confusion of the damage interpretation.L’obiettivo di questa ricerca era ottenere un approfondimento all’interno del complesso sistema di variabili dell’impatto della propagazione delle fratture senza ignorare il danno da non impatto. Usando l’approccio sperimentale, sono stati raccolti i dati fondamentali che erano necessari per un’affidabile interpretazione del danno che sono stati ulteriormente usati per l’interpretazione del danno identificato sugli strumenti appuntiti proveniente da Riparo Tagliente, arrivando a conclusioni sulla loro possibile funzionalità. Adattando le variabili sperimentali il più vicino possibile alle variabili del materiale archeologico proveniente da Riparo Tagliente, sono stati effettuati quattro esperimenti. Il primo esperimento è consistito in una simulazione di caccia usando le punte Musteriane che erano fissate alla lancia, usando due approcci di fissaggio, verticale e diagonale, e che venivano lanciate mirando all’animale morto. I risultati ottenuti hanno evidenziato l’affidabilità dell’interpretazione del danno ed hanno stabilito la sua causa nel materiale archeologico. Il danno da scheggiatura è stato identificato sulle punte usate nel primo esperimento, nel frattempo il secondo esperimento è stato stabilito ed eseguito in modo da osservare le variazioni e le cause delle fratture che potevano essere causate dalla scheggiatura. Il terzo esperimento è consistito anche in una simulazione di caccia che è stata effettuata per approfondire l’impatto della propagazione delle fratture usando le punte di Levallois con un metodo di ancoraggio leggermente differente rispetto a quello usato nel primo esperimento. L’affidabilità dei risultati ottenuti dal terzo esperimento è stata messa in discussione a causa della strumentazione moderna impiegata e della scarsa quantità di provini sperimentali. Il danno da non impatto che è stato identificato sugli strumenti a punta provenienti da Riparo Tagliente non è stato ignorato e il quarto esperimento non è stato ignorato per questo motivo. L’obiettivo del quarto esperimento è consistito nell’ottenere un’osservazione sui segni causati dai danni ai bordi che si sarebbero potuti formare sugli strumenti a punta usandoli nel taglio, nella frantumazione, nella tritura. I risultati hanno implementato l’interpretazione dei segni causati dai danni ai bordi identificati sugli strumenti a punta provenienti dal sito di Riparo Tagliente. Usando tutti i dati ottenuti sperimentalmente è stata confermata la possibile funzionalità degli strumenti a punta provenienti dal sito di Riparo Tagliente. Si conclude che gli strumenti provenienti da Riparo Tagliente venissero utilizzati come strumenti multifunzionali. Inoltre questa ricerca ha suggerito che fosse necessario migliorare la metodologia della ricerca sull’impatto delle fratture in modo da evitare ulteriore confusione sull’interpretazione del danno

Amélioration de l'endurance des mini-drones grâce à la récupération d'énergie à partir de rafales atmosphériques

Cette thèse a pour but de découvrir la faisabilité et le potentiel de la récupération d'énergie à partir de rafales atmosphériques pour les micro et mini véhicules aériens sans pilote. L'atmosphère sert de grande source d'énergie pouvant être récoltée afin d'accroître la performance des petits UAV sous la forme d'une autonomie et d'une autonomie étendues. Il est bien connu que de nombreuses espèces d'oiseaux utilisent diverses techniques de vol pour obtenir des performances de vol étonnantes. Compte tenu du fait que les véhicules susmentionnés partagent la taille et la vitesse de vol avec des dépliants naturels, cette thèse peut être considérée comme une application des techniques de vol bio-inspirées pour les véhicules construits par l’homme. Cette étude de trois ans visait à établir une dérivation théorique des équations qui décrivent la dynamique de vol d'un aéronef en présence d'un environnement en rafales. La première réalisation a été la démonstration du mécanisme de récupération d'énergie et des paramètres d'influence à travers des simulations décrivant le vol en modèle de masse ponctuelle d'aéronef avec un contrôle optimisé de l'ascenseur en présence d'un profil de vent sinusoïdal et stochastique. La réalisation suivante est liée à un système sensoriel inspiré par la biologie qui utilise des mesures de pression des ailes pour estimer l’angle d’attaque local. Ce système particulier a été utilisé dans l’estimation du champ de vent, en tant que mécanisme décisif et protection contre le décrochage. Enfin, les dernières contributions sont liées à l’expérience et aux résultats obtenus lors d’essais en vol visant à prouver l’augmentation de l’état énergétique de l’avion lors des manœuvres de récupération d’énergie. La première campagne d'essais en vol a été réalisée avec un mini-UAV disponible dans le commerce équipé de sondes à trous multiples et d'un contrôleur conçu sur mesure. Cette campagne a démontré l’augmentation de l’état d’énergie dans un fort gradient de vent horizontal. La deuxième campagne d'essais en vol a été réalisée avec une aile volante équipée d'un système de détection de pression pour l'estimation du champ de vent. Cette campagne a également impliqué des économies supplémentaires sur la consommation d'énergie électrique lors des vols de récupération d'énergie.This thesis aims at discovering the feasibility and potential of energy-harvesting from atmospheric gusts for micro and mini unmanned aerial vehicles. The atmosphere serves as a great source of energy that can be harvested in order to increase performance of small UAVs in form of extended endurance and range. It is well known that many bird species use various flight techniques for achieving astonishing flight performances. Considering the fact that aforementioned vehicles share size and flight speed with natural flyers, this thesis can be considered as an application of bioinspired flight techniques for man made vehicles. This three-year study set out to establish a theoretical derivation of equations that describe flight dynamics of an aircraft in presence of gusty environment. The first achievement was demonstration of energy harvesting mechanism and influencing parameters through simulations that describe aircraft point mass model flight with optimized control of elevator in presence of sinusoidal and stochastic wind profile. The next achievement is related to a biologically inspired sensory system that uses wing pressure measurements for local angle of attack estimation. That particular system found purpose in wind field estimation, as decisive mechanism and stall protection. Finally, last contributions are related to experience and results gained from flight tests which aimed to prove increase in energy state of the aircraft while performing energy harvesting maneuvers. The first flight test campaign was performed with commercially available mini UAV equipped with multi-hole probes and custom designed controller. This campaign demonstrated the raise in energy state within strong horizontal wind gradient. The second flight test campaign was done with a flying wing equipped with pressure sensing system for wind field estimation. This campaign also involved additional insight savings in electrical power consumption during energy harvesting flights