Modélisation et asservissement du décollage vertical d’un drone aquatique à voilure fixe

Les nouvelles applications des petits drones volants prolifèrent grâce à leur récent gain de popularité. Un désavantage majeur de ces appareils est leur court temps de vol. Il est possible d’allonger la durée d’une mission d’un petit drone en effectuant une série de vols intermittents, possibles si l’appareil se pose sur un plan d’eau pour se recharger grâce à l’énergie solaire. La capacité de fonctionner dans les airs et sur l’eau ouvre également de nouveau champs d’application, comme les patrouilles maritimes et des suivis écologiques. L’appareil développé à l’Université de Sherbrooke, le SUWAVE, vise à combiner les avantages des petits drones volants à ceux des modèles hybrides, aquatiques et aériens. Contrairement à d’autres avions aquatiques, le SUWAVE effectue un décollage vertical à partir de l’eau. Le présent projet de recherche vise à mieux comprendre la dynamique d’une telle manoeuvre afin de concevoir le contrôle approprié pour garantir son succès, malgré les perturbations du vent et des vagues

Challenges in control and autonomy of unmanned aerial-aquatic vehicles

Autonomous aquatic vehicles capable of flight can deploy more rapidly, access remote or constricted areas, overfly obstacles and transition easily between distinct bodies of water. This new class of vehicles can be referred as Unmanned Aerial-Aquatic Vehicles (UAAVs), and is capable of reaching distant locations rapidly, conducting measurements and returning to base. This greatly improves upon current solutions, which often involve integrating different types of vehicles (e.g. vessels releasing underwater vehicles), or rely on manpower (e.g. sensors dropped manually from ships). Thanks to recent research efforts, UAAVs are becoming more sophisticated and robust. Nonetheless numerous challenges remain to be addressed, and particularly dedicated control and sensing solutions are still scarce. This paper discusses challenges and opportunities in UAAV control, sensing and actuation. Following a brief overview of the state of the art, we elaborate on the requirements and challenges for the main types of robots and missions proposed in the literature to date, and highlight existing solutions where available. The concise but wide-ranging overview provided will constitute a useful starting point for researchers undertaking UAAV control work

Small Unmanned Aerial Systems (sUAS) for environmental remote sensing: challenges and opportunities revisited

Hardin and Jensen (2011) presented six challenges to using small Unmanned Aerial Systems (sUAS) for environmental remote sensing: challenge of the hostile flying environment, challenge of power, challenge of available sensors, challenge of payload weight, challenge of data analysis, and challenge of regulation. Eight years later we revisit each of the challenges in the context of the current sUAS environment. We conclude that technological advances made in the interim (as applied to environmental remote sensing) have either (1) improved practitioner ability to respond to a challenge or (2) decreased the magnitude of the challenge itself. However, relatively short flight time remains a primary challenge to using sUAS in environmental remote sensing

Low Speed Flap-bounding in Ornithopters and its Inspiration on the Energy Efficient Flight of Quadrotors

Flap-bounding, a form of intermittent flight, is often exhibited by small birds over their entire range of flight speeds. The purpose of flap-bounding is unclear during low to medium speed (2 - 8 m/s) flight from a mechanical-power perspective: aerodynamic models suggest continuous flapping would require less power output and lower cost of transport. This thesis works towards the understanding of the advantages of flap-bounding and tries to employ the underlining principle to design quadrotor maneuver to improve power efficiency. To explore the functional significance of flap-bounding at low speeds, I measured body trajectory and kinematics of wings and tail of zebra finch (Taeniopygia guttata, N=2) during flights in a laboratory between two perches. The flights consist of three phases: initial, descending and ascending. Zebra finch first accelerated using continuous flapping, then descended, featuring intermittent bounds. The flight was completed by ascending using nearly-continuous flapping. When exiting bounds in descending phase, they achieved higher than pre-bound forward velocity by swinging body forward similar to pendulum motion with conserved mechanical energy. Takeoffs of black-capped chickadees (Poecile atricapillus, N=3) in the wild was recorded and I found similar kinematics. Our modeling of power output indicates finch achieves higher velocity (13%) with lower cost of transport (9%) when descending, compared with continuous flapping in previously-studied pigeons. To apply the findings to the design of quadrotor motion, a mimicking maneuver was developed that consisted of five phases: projectile drop, drop transition, pendulum swing, rise transition and projectile rise. The quadrotor outputs small amount (4 N) of thrust during projectile drop phase and ramps up the thrust while increasing body pitch angle during the drop transition phase until the thrust enables the quadrotor to advance in pendulum-like motion in the pendulum swing phase. As the quadrotor reaches the symmetric point with respect to the vertical axis of the pendulum motion, it engages in reducing the thrust and pitch angle during the rise transition phase until the thrust is lowered to the same level as the beginning of the maneuver and the body angle of attack minimized (0.2 deg) in the projectile rise phase. The trajectory of the maneuver was optimized to yield minimum cost of transport. The quadrotor moves forward by tracking the cycle of the optimized trajectory repeatedly. Due to the aggressive nature of the maneuver, we developed new algorithms using onboard sensors to determine the estimated position and attitude. By employing nonlinear controller, we showed that cost of transport of the flap-bounding inspired maneuver is lower (28%) than conventional constant forward flight, which makes it the preferable strategy in high speed flight (≥15 m/s)

Continuous Open Access Special Issue "Aircraft Design": Number 2/2020

Following the successful initial Special Issue on “Aircraft Design (SI-1/2017)”, this is already the second SI “Aircraft Design (SI-2/2020)”. Activities in the past showed that aircraft design may be a field too small to justify its own (subscription-based) journal. A continuous open access special issue may fill the gap. As such, the Special Issue “Aircraft Design” can be a home for all those working in the field who regret the absence of an aircraft design journal. SI-2/2020 contains seven papers; an Editorial: 1.) "Publishing in 'Aircraft Design' with a Continuous Open Access Special Issue" and six Original Research Articles about 2.) Amphibious Aircraft Developments, 3.) Design Space Exploration of Jet Engine Components, 4.) Study of Subsonic Wing Flutter, 5.) Design Optimization of a Blended Wing Body Aircraft, 6.) Discrete Mobile Control Surfaces, 7.) Electro-Impulse De-Icing Systems

FINE SCALE MAPPING OF LAURENTIAN MIXED FOREST NATURAL HABITAT COMMUNITIES USING MULTISPECTRAL NAIP AND UAV DATASETS COMBINED WITH MACHINE LEARNING METHODS

Natural habitat communities are an important element of any forest ecosystem. Mapping and monitoring Laurentian Mixed Forest natural communities using high spatial resolution imagery is vital for management and conservation purposes. This study developed integrated spatial, spectral and Machine Learning (ML) approaches for mapping complex vegetation communities. The study utilized ultra-high and high spatial resolution National Agriculture Imagery Program (NAIP) and Unmanned Aerial Vehicle (UAV) datasets, and Digital Elevation Model (DEM). Complex natural vegetation community habitats in the Laurentian Mixed Forest of the Upper Midwest. A detailed workflow is presented to effectively process UAV imageries in a dense forest environment where the acquisition of ground control points (GCPs) is extremely difficult. Statistical feature selection methods such as Joint Mutual Information Maximization (JMIM) which is not that widely used in the natural resource field and variable importance (varImp) were used to discriminate spectrally similar habitat communities. A comprehensive approach to training set delineation was implemented including the use of Principal Components Analysis (PCA), Independent Components Analysis (ICA), soils data, and expert image interpretation. The developed approach resulted in robust training sets to delineate and accurately map natural community habitats. Three ML algorithms were implemented Random Forest (RF), Support Vector Machine (SVM), and Averaged Neural Network (avNNet). RF outperformed SVM and avNNet. Overall RF accuracies across the three study sites ranged from 79.45-87.74% for NAIP and 87.31-93.74% for the UAV datasets. Different ancillary datasets including spectral enhancement and image transformation techniques (PCA and ICA), GLCM-Texture, spectral indices, and topography features (elevation, slope, and aspect) were evaluated using the JMIM and varImp feature selection methods, overall accuracy assessment, and kappa calculations. The robustness of the workflow was evaluated with three study sites which are geomorphologically unique and contain different natural habitat communities. This integrated approach is recommended for accurate natural habitat community classification in ecologically complex landscapes

The HAMMER: High altitude multiple mission environmental researcher

At the equator, the ozone layer ranges from 65,000 to 130,000+ feet which is beyond the capabilities of the ER-2, NASA's current high altitude reconnaissance aircraft. The Universities Space Research Association, in cooperation with NASA, is sponsoring an undergraduate program which is geared to designing an aircraft that can study the ozone layer at the equator. This aircraft must be able to satisfy four mission profiles. Mission one is a polar mission which ranges from Chile to the South Pole and back to Chile, a total range of 6000 n. mi. at 100,000 feet with a 2500 lb. payload. The second mission is also a polar mission with a decreased altitude of 70,000 feet and an increased payload of 4000 lb. For the third mission, the aircraft will take-off at NASA Ames, cruise at 100,000 feet carrying a 2500 lb. payload, and land in Puerto Montt, Chile. The final mission requires the aircraft to take-off at NASA Ames, cruise at 100,000 feet with a 1000 lb. payload, make an excursion to 120,000 feet, and land at Howard AFB, Panama. All three missions require that a subsonic Mach number is maintained due to constraints imposed by the air sampling equipment. The aircraft need not be manned for all four missions. Three aircraft configurations were determined to be the most suitable for meeting the above requirements. The performance of each configuration is analyzed to investigate the feasibility of the project requirements. In the event that a requirement can not be obtained within the given constraints, recommendations for proposal modifications are given