Shear Wind Estimation

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90724/1/AIAA-2011-6224-875.pd

Perpetual flight in flow fields

Tese de Doutoramento. Engenharia Electrotécnica e de Computadores. Faculdade de Engenharia. Universidade do Porto. 201

From albatross to long range UAV flight by dynamic soaring

In the domain of UAVs, endurance and range are key utility factors. However, small-sized UAVs are faced with serious limitations regarding energy storage options. A way to address this challenge is to seek for energy from the surrounding environment. One flight technique, called dynamic soaring, has been perfected by large seabirds like the albatross, which enables them to wander effortlessly in southern oceans. This thesis investigates the feasibility to find inspiration from the biological world in order to address the issue of limited endurance.First of all, an extensive literature background sums-up a range of technical aspects that can be learnt out of the flight of albatrosses. It reviews their morphology, flight performance and sensitivity to wind strength, their flight characteristics and energy expenditure management. Then, a methodology to simulate dynamic soaring flight is built-up by focusing first on adequate models for the vehicle and for the environment. It details the way those models are described quantitatively and qualitatively. As for the vehicle, a point mass model is chosen and applied to fixed-wing gliders of several scales, as well as to an albatross of generic dimensions. The environment is first modelled by classical boundary layer theory on a rather flat surface and then refined by taking into account specificity about the ocean boundary layer, such as varying roughness length and surface waves. Equations of motion are detailed for both points of views, earth-relative and air relative. This yields two different sets of equations of motion, eventually representing equivalent physics. An optimization problem is then set in order to determine, for the vehicle, how to extract energy from its environment. Variations in objective function and in constraints are described before presenting the numerical integration scheme which converts the optimization problem into that of finite-dimension. The solving tools and their specificity are presented, followed by a validation of the overallmethodology with a particular study case from the literature. Basic principles of dynamic soaring flight are explicated by using a specific closed-loop study case. Energy-harvesting mechanisms are disclosed locally and next integrated over the whole flight path. A further illustration of dynamic soaring is provided by relaxing some periodicity constraints and opening the trajectory. The specificity of the ocean boundary layer environment is finally implemented and a refined energy-harvesting strategy is presented. Air relative equations of motion are dimensionless so as to highlight specific dynamic soaring behaviours, in the case of a simplified linear wind profile and eventually by finding an appropriate non-dimensionalization for a logarithmic wind profile. Conditions of similarities between dimensionless solutions are described and some basic dynamic soaring characteristics are outlined. Finally, various dynamic soaring performance study case are computed. Optimized trajectories are implemented for the selected vehicles and compared on a required wind strength basis. The sensitivity of the required wind strength to the net flight heading as well as to the ground clearance and to the surface roughness length is determined by drawing performance charts. In order to enlarge the scope of favourable dynamic soaring conditions, thrust-augmented trajectories are considered. The range improvements offered by dynamic soaring are compared to a straight line case, for different wind strength and different net flight headings

An End-to-End Platform for Autonomous Dynamic Soaring in Wind Shear

Despite advancements in our understanding of flight in modern times, birds remain unmatched when it comes to maneuverability and energy efficiency in flight; in particular seabirds like the albatross are known to travel vast distances without stopping for food by performing an aerobatic maneuver called dynamic soaring. When the maneuver is executed in the presence of a wind field that varies in strength of direction, the albatross extracts kinetic energy from the field. In this dissertation, we present an end-to-end system designed to exploit wind as the albatross does. The system we designed consists of a gliding platform outfitted with sensors and computational hardware, an on-board software platform that enables autonomy, and a ground platform for monitoring mission performance and issuing commands.We contribute the design of an airframe, the Fox, capable of performing dynamic soaring at low altitudes (~400m above sea level). We validate the airframe against expected stressors (vibration, coefficient of lift, temperature, and communication signal strength), and show in simulation it can complete a dynamic soaring orbit in wind shear that varies in maximum wind speed from 8 to 12 m/s. We show that this airframe can reach speeds exceeding 40 m/s while soaring.We fit the airframe with a commercial off-the-shelf autopilot, as well as a custom on-board-computing (OBC) solution to provide the necessary facilities to enable autonomy. The OBC generates dynamic soaring trajectories that fit a wind-field map that is built as the aircraft is deployed and controls the Fox to follow them by sending commands to the autopilot using a sample-based controller scheme. This process is monitored by human operators on the ground via a portable ground station that is linked to the Fox via a radio antenna. Field tests are presented that validate real-world controller performance against simulated results.Finally, we present a learning controller that learns from and out-performs the sample-based controller in simulation. While not field tested, we believe a self-optimizing controller of this form is necessary to enable autonomy of a soaring aircraft subject to extended mission durations.While dynamic soaring field tests were not pursued in this work, we hope this dissertation will be a blueprint for future researchers to finally achieve autonomous soaring

Airframe assembly, systems integration and flight testing of a long endurance electric UAV

The need to adopt new techniques and practices in the Aerospace Industry branch is a consequence of technological development. The present work aims to study the use of solar power as a main energy source in the aviation, in this case for a flight of long endurance of an unmanned air vehicle. This master thesis follows on previous works of the LEEUAV, where it was done the design and construction of a long endurance unmanned aerial system. Thus, the main objective of this work is the systems integration, flight testing and concepts validation. LEEUAV, a prototype of 4.5 meters’ wingspan and ultralight structure partially covered by solar cells was designed to fulfil a continuous flight mission of at least 8 hours on the equinox. The 5.42Kg remotely piloted aircraft was successfully tested showing the agreement with theoretical calculations already made. The longest flight achieved lasted more than 8.5 hours’ resulting in a total distance travelled of more than 75 km. In order to validate the airworthiness concept of the LEEUAV several flight tests were performed and their respective data (static and total pressure, air temperature, ground speed and pitch angle) was collected for further analysis, using a flight controller with multiple sensors on board. The results obtained allowed to study the general performance of the aircraft, the main defects, agreement with the theoretical results as well as determine the real values of aerodynamic coefficients (????, ????), through a reading and processing flight data algorithm in Software MATLAB. Finally, some future expectations for upcoming work are suggested in order to make the LEEUAV an Unmanned Aerial Vehicle of reference.A necessidade de adoção de novas técnicas e práticas no ramo da Indústria Aeronáutica é uma consequência do desenvolvimento tecnológico. O presente trabalho aborda o uso de energia solar como principal fonte de energia na aviação, com enfoque num voo de grande autonomia de uma aeronave não tripulada. Esta tese de mestrado surge na sequência de trabalhos anteriores relativos ao LEEUAV, nos quais se efetuou o projeto e construção de uma aeronave não tripulada de grande autonomia. Assim, o principal objetivo deste trabalho é a integração de sistemas, testes de voo e validação de conceitos. O UAV Solar LEEUAV é um protótipo de 4.5 metros de envergadura e de estrutura ultraleve parcialmente coberto de células fotovoltaicas sendo projetado para cumprir uma missão de voo contínuo de pelo menos 8h no equinócio. O avião de 5.42kg foi testado com sucesso mostrando a concordância com os cálculos teóricos já elaborados. O voo mais longo conseguido foi de 3.13 horas correspondendo a uma distância total percorrida de 96.265 km. De modo a validar o conceito de aeronavegabilidade do LEEUAV foram efetuados vários voos de teste e recolhidos dados de voo (pressão estática e dinâmica, temperatura do ar, velocidade no solo e ângulo de arfagem) para posterior análise, utilizando um controlador de voo com múltiplos sensores a bordo. A análise dos resultados obtidos permitiu precisar o desempenho geral da aeronave, os principais defeitos, concordância com os resultados teóricos assim como determinar os valores reais dos coeficientes aerodinâmicos (???? , ????) através de um algoritmo de leitura e processamento de dados de voo, em Software MATLAB. Por fim, são referidas algumas sugestões para o desenvolvimento de novos trabalhos com o objetivo de tornar O LEEUAV num veículo aéreo não tripulado de referência

A Biomimetic, Energy-Harvesting, Obstacle-Avoiding, Path-Planning Algorithm for UAVs

This dissertation presents two new approaches to energy harvesting for Unmanned Aerial Vehicles (UAV). One method is based on the Potential Flow Method (PFM); the other method seeds a wind-field map based on updraft peak analysis and then applies a variant of the Bellman-Ford algorithm to find the minimum-cost path. Both methods are enhanced by taking into account the performance characteristics of the aircraft using advanced performance theory. The combined approach yields five possible trajectories from which the one with the minimum energy cost is selected. The dissertation concludes by using the developed theory and modeling tools to simulate the flight paths of two small Unmanned Aerial Vehicles (sUAV) in the 500 kg and 250 kg class. The results show that, in mountainous regions, substantial energy can be recovered, depending on topography and wind characteristics. For the examples presented, as much as 50% of the energy was recovered for a complex, multi-heading, multi-altitude, 170 km mission in an average wind speed of 9 m/s. The algorithms constitute a Generic Intelligent Control Algorithm (GICA) for autonomous unmanned aerial vehicles that enables an extraction of atmospheric energy while completing a mission trajectory. At the same time, the algorithm automatically adjusts the flight path in order to avoid obstacles, in a fashion not unlike what one would expect from living organisms, such as birds and insects. This multi-disciplinary approach renders the approach biomimetic, i.e. it constitutes a synthetic system that “mimics the formation and function of biological mechanisms and processes.

One-shot Manufacturing Techniques Developed for Carbon Fiber Prepreg Components

The need for faster and more accurate manufacturing methods for composite parts continues to grow. Co-curing composite structures can decrease manufacturing time by eliminating secondary operations such as grinding, jigging, bonding, and fastening while creating lighter and more accurate parts. As a demonstrator for co-curing techniques, a six-meter carbon fiber wing for a high-altitude and high-speed dynamically soaring unmanned aerial vehicle (UAV) was designed and manufactured in one cure cycle. Two wing-skin molds were created using low density tooling board, with the mold geometry directly machined into the material, reducing tool manufacturing time and cost. An aluminum insert was used to create a trailing edge cavity while maintaining a simple parting line of the wing tool. Three removable forms made of polystyrene foam inside of the wing cavity were used to position six internal webs and, after curing and removal of the forms, resulted in a hollow wing with internal webs. The resulting wings showed some defects in the wing skins but overall produced structurally sound parts.Expanding on the previous co-curing techniques, a 1.1-meter carbon fiber horizontal stabilizer with internal structure and an elevator connected by a composite flexure was designed and manufactured in one cure cycle. The stabilizer is used in a high-altitude and high-speed dynamically soaring unmanned aerial vehicle (UAV). The top skin is used as the flexure, creating a seamless top surface between the stabilizer and elevator. Three removable forms made of polystyrene foam were used inside the stabilizer to position a spar web and center rib, which after curing and removal of the forms resulted in a hollow stabilizer with an internal web and rib. The resulting stabilizers showed minor defects in the wing skins but overall produced structurally sound parts.The demonstrators showed the great potential for creating complex composite parts and assemblies using only a single cure cycle while needing little finishing work and no secondary bonding, resulting in high precision at relatively low cost.Utilizing the components produced, the JetStreamer was able to be assembled and flown in Weldon, The JetStreamer is believed to be the largest unmanned aircraft to demonstrate dynamic soaring

WindBots: A Concept for Persistent In-Situ Science Explorers for Gas Giants

This report summarizes the study of a mission concept to Jupiter with one or multiple Wind Robots able to operate in the Jovian atmosphere, above and below the clouds - down to 10 bar, for long durations and using energy obtained from local sources. This concept would be a step towards persistent exploration of gas giants by robots performing in-situ atmospheric science, powered by locally harvested energy. The Wind Robots, referred in this report as WindBots (WBs), would ride the planetary winds and transform aeolian energy into kinetic energy of flight, and electrical energy for on-board equipment. Small shape adjustments modify the aerodynamic characteristics of their surfaces, allowing for changes in direction and a high movement autonomy. Specifically, we sought solutions to increase survivability to strong/turbulent winds, and mobility and autonomy compared to passive balloons

A survey of free software for the design, analysis, modelling, and simulation of an unmanned aerial vehicle

The objective of this paper is to analyze free software for the design, analysis, modelling, and simulation of an unmanned aerial vehicle (UAV). Free software is the best choice when the reduction of production costs is necessary; nevertheless, the quality of free software may vary. This paper probably does not include all of the free software, but tries to describe or mention at least the most interesting programs. The first part of this paper summarizes the essential knowledge about UAVs, including the fundamentals of flight mechanics and aerodynamics, and the structure of a UAV system. The second section generally explains the modelling and simulation of a UAV. In the main section, more than 50 free programs for the design, analysis, modelling, and simulation of a UAV are described. Although the selection of the free software has been focused on small subsonic UAVs, the software can also be used for other categories of aircraft in some cases; e.g. for MAVs and large gliders. The applications with an historical importance are also included. Finally, the results of the analysis are evaluated and discussed—a block diagram of the free software is presented, possible connections between the programs are outlined, and future improvements of the free software are suggested. © 2015, CIMNE, Barcelona, Spain.Internal Grant Agency of Tomas Bata University in Zlin [IGA/FAI/2015/001, IGA/FAI/2014/006

An aircraft and provide information about flight performance and local microclimate

Includes abstract.Includes bibliographical referencesThe application of using Unmanned Aerial Vehicles (UAVs) to locate thermal updraft currentsis a relatively new topic. It was first proposed in 1998 by John Wharington, and, subsequently, several researchers have developed algorithms to search and exploit thermals. However, few people have physically implemented a system and performed field testing. The aim of this project was to develop a low cost system to be carried on a glider to detect thermals effectively. A system was developed from the ground up and consisted of custom hardware and software that was developed specifically for aircraft. Data fusion was performed to estimate the attitude of the aircraft; this was done using a direction cosine (DCM) based method. Altitude and airspeed data were fused by estimating potential and kinetic energy respectively; thus determining the aircraft’s total energy. This data was then interpreted to locate thermal activity. The system comprised an Inertial Measurement Unit (IMU), airspeed sensor, barometric altitude sensor, Global Positioning System (GPS), temperature sensor, SD card and a realtime telemetry link. These features allowed the system to determine aircraft position, height, airspeed and air temperature in realtime. A custom-designed radio controlled (RC) glider was constructed from composite materials in addition to a second 3.6 m production glider that was used during flight testing. Sensor calibration was done using a wind tunnel with custom designed apparatus that allowed a complete wing with its pitot tube to be tested in one operation. Flight testing was conducted in the field at several different locations over the course of six months. A total of 25 recorded flights were made during this period. Both thermal soaring and ridge soaring were performed to test the system under varying weather conditions. A telemetry link was developed to transfer data in realtime from the aircraft to a custom ground station. The recorded results were post-processed using Matlab and showed that the system was able to detect thermal updrafts. The sensors used in the system were shown to provide acceptable performance once some calibration had been performed. Sensor noise proved to be problematic, and time was spent alleviating its effects