Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: In recent years, the use of airships has become popular for observation purposes since they provide a cost effective alternative to other aircraft. For this project a lateral and longitudinal flight control system are required for waypoint navigation flight of an 8m long, non-rigid airship. The airship’s actuators include a rudder, elevator and a propulsion system which can be vectored longitudinally. Two airship models are evaluated for this project. A chosen model is linearised and a modal analysis is done. The modal analysis is compared to a previous modal study done on the YEZ-2A airship and is found to compare well. Each airship mode is discussed and the linear behaviour is compared to the behaviour of the non-linear model. A fuzzy logic controller design approach was undertaken for the design of speed, heading and height controllers. These non-linear controllers were designed for the non-linear model, due to the following reasons: Fuzzy logic controllers show tolerance to model inaccuracies. Complexity of design is simple. Controllers can be adjusted intuitively. Fuzzy logic controllers can be combined with conventional control techniques. Simulation results showed adequate lateral and longitudinal performance, even when subjected to light wind conditions and disturbances. The inertial measuring unit implemented in a previous project is used and additional hardware is designed and implemented for the control of the airship’s actuators. Several improvements are made to the groundstation software to allow for activation of different controllers as well as for setting up the desired flight plan. The controller performance is tested through flight tests and shows adequate performance as well as controller potential. Although further work is still required for improving the controllers’ performance, this thesis acts as a platform for future research. / AFRIKAANSE OPSOMMING: In die afgelope paar jaar het die gebruik van die lugskepe gewild geword vir waarnemings doeleindes aangesien dit ’n koste effektiewe alternatief vir ander lugvaartuie bied. In hierdie projek word ’n laterale en longitudinale beheerstelsel benodig vir merker navigasie vlugte met ’n 8m lang, nierigiede lugskip. Die lugskip se aktueerders sluit in ’n rigtingroer, hoogteroer asook ’n aandrywing stelsel wat oorlangs gestuur kan word. Vir hierdie projek is twee lugskip modelle geïmplementeer. Die gekose model is gelineariseer en ’n modale analise is gedoen. Die modale analise is met ’n vorige modale studie vir die YEZ-2A lugskip vergelyk en wys soortegelyke linieêre gedrag. Die lugskip modusse is bespreek en die linieêre gedrag word met die gedrag van die nie-linieêre model vergelyk. Daar is op ’n fuzzy logiese beheerder ontwerp besluit vir die ontwerp van spoed, rigting en hoogte beheerders. Hierdie nie-linieêre beheerders is ontwerp vir die nie-linieêre model a.g.v. die volgende redes: Fuzzy logiese beheerders toon toleransie vir modellering of meetfoute. Kompleksiteit van die ontwerp is eenvoudig. Beheerders kan intuïtief aangepas word. Fuzzy logiese beheerders kan met konvensionele beheertegnieke gekombineer word. Simulasie resultate toon voldoende werkverrigtinge, selfs in die teenwoordigheid van ligte wind sowel as ander versteurings. Die inersiële metings eenheid, wat geïmplementeer is in ’n vorige projek, is gebruik en addisionele hardeware vir die beheer van die lugskip is aktueerders is ontwerp en geïmplementeer. Talle verbeterings is aangebring aan die grondstasie sagteware vir die aktiveer van die beheerders sowel as die uitleg van die gekose vlugplan. Die beheerders se werksverrigtinge is getoets gedurende vlugtoetse en toon voldoende beheer vermoë sowel as beheerder potensiaal. Alhoewel verdere werk steeds nodig is vir die verbetering van die beheerders, dien hierdie tesis as ’n platform vir toekomstige navorsing.

Airships provide an eco-friendly and cost-effective means to suit sustained airborne operations. Smaller autonomous airships are highly susceptible to adverse atmospheric conditions owing to their under-actuated, underpowered and bulky size relative to other types of unmanned aerial vehicles (UAVs). To mitigate these limitations, careful considerations of the size and shape must be made at the design stage. This research presents a methodology for obtaining an optimized shape of a semi-rigid airship. Rapid descent of the LTA ship is achieved by means of a moving gondola attached to a rigid keel mounted under the helium envelope from the bow to the mid-section of the hull. The study entails the application of a robust hybrid genetic algorithm (HGA) for the multi-disciplinary design and optimization of an airship capable of rapid descent, with lower drag and optimum surface area. A comprehensive sensitivity analysis was also performed on the basis of algorithmic parameters and atmospheric conditions. With the help of HGA, a semi-rigid airship capable of carrying a payload of 0.25 kg to 1.0 kg and capable of pitching at right angles is conceptually designed. The algorithm is also tested on commercially available vehicles to validate the results. In multi-objective optimization problems (MOOPs), the significance of different objectives is dependent on the user.

With devastating natural disasters on the rise, technological improvements are needed in the field of search and rescue (SAR). Unmanned aerial vehicles (UAVs) would be ideal for the search function such that manned vehicles can be prioritized to distributing first-aid and ultimately saving lives. One of the major reasons that UAVs are under utilized in SAR is that they lack a long flight endurance which compromises their effectiveness. Dirigibles are well suited for SAR missions since they can hover and maintain lift without consuming energy and can be easily deflated for packaging and transportation. This research focuses on extending flight endurance of small-scale airship UAVs through improvements to the infrastructure design and flight trajectory planning. In the first area, airship design methodologies are reviewed leading to the development and experimental testing two hybrid fuel-electric power plants. The prevailing hybrid power plant design consists of a 4-stroke 14cc gasoline engine in-line with a brushless DC motor/generator and variable pitch propeller. The results show that this design can produce enough mechanical and electrical power to support 72 hours of flight compared to 1-4 hours typical of purely electric designs. A power plant configuration comparison method was also developed to compare its performance and endurance to other power plant configurations that could be used in dirigible UAVs. Overall, the proposed hybrid power plant has a 600% increase in energy density over that of a purely electric configuration. In the second area, a comprehensive multi-objective cost function is developed using spatially variable wind vector fields generated from computational fluid dynamic analysis on digital elevations maps. The cost function is optimized for time, energy and collision avoidance using a wavefront expansion approach to produce feasible trajectories that obey the differential constraints of the airship platform. The simulated trajectories including 1) variable vehicle velocity, 2) variable wind vector field (WVF) data, and 3) high grid resolutions were found to consume 50% less energy on average compared to planned trajectories not considering one of these three characteristics. In its entirety, this research addresses current UAV flight endurance limitations and provides a novel UAV solution to SAR surveillance.

Subject of this diploma thesis is design of cargo airship. The thesis concerns analysis of problem and concept design vision of cargo airship exterior.

With the recent advances in the field of unmanned aerial vehicles, many applications have been identified. In tasks that require high-payload-to-weight ratios, flight times in the order of days, reduced noise and/or hovering capabilities, lighter-than-air vehicles present themselves as a competitive platform compared to fixed-wing and rotor based vehicles. The limiting factor in their widespread use in autonomous applications comes from the complexity of the control task. The so-called airships are highly-susceptible to aerodynamic forces and pose complex nonlinear system dynamics that complicate their modeling and control. Model-free control lends itself well as a solution to this type of problem, as it derives its control policies using input-output data, and can therefore learn complex dynamics and handle uncertain or unknown parameters and disturbances. In this work, two multi-input multi-output algorithms are presented on the basis of optimal control theory. Leveraging results from reinforcement learning, a single layer, partially connected neural network is formulated as a value function appropriator in accordance with Weierstrass higher-order approximation theorem. The so-called critic-network is updated using gradient descent methods on the mean-squared error of the temporal difference equation. In the single-network controller, the control policy is formulated as a closed form equation that is parameterized on the weights of the critic-network. A second controller is proposed that uses a second single-layer partially connected neural network, the actor-network, to calculate the control action. The actor-network is also updated using gradient descent on the squared error of the temporal difference equation. The controllers are employed in a highly realistic simulation airship model in nominal conditions and in the presence of external disturbances in the form of turbulent wind. To verify the validity and test the sensitivity of the algorithms to design parameters (the initialization of certain terms), ablation studies are carried out with multiple initial parameters. Both of the proposed algorithms are able to track the desired waypoints in both the nominal and disturbed flight tests. Furthermore, the performance of the controllers is compared to a modern, state-of-the-art multi-input multi-output controller. The two proposed controllers outperform the comparison controller in all but one flight test, with up to four fold reduction in the integral absolute error and integral time absolute error metrics. On top of the quantitative improvements seen in the proposed controllers, both controllers demonstrate a reduction in system oscillation and actuator chattering with respect to the comparison algorithm.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Aerostats and Stratolites could play a major role in expanding current satellite and other technologies in the near future. A study was made on the development of aerostat platforms and the current state of Stratolite development. The aim was to develop an airship system that is capable of maintaining a specific position regardless of the presence of wind. The various applications of such a geostationary platform are discussed. A dynamic model of an airship was developed and a simulation was implemented in software. This was done to study the possibility of developing aerostats like these. A tethered airship system was developed and built to demonstrate that it is possible to control the position of an airship. The airship system uses current technology in an unique combination to fulfil the requirement of remaining stationary despite the influence of wind. Various control system design techniques were used to implement the controllers. Linear models of the airship system were identified practically and used to design the controllers. The controllers were tested in simulation as well as practically and the results of these tests are given. It was concluded that there exists potential for the development of Stratolite systems, although there exists a fair amount of challenges and obstacles that would need to be overcome before this technology could be implemented. / AFRIKAANSE OPSOMMING: Aerostats en Stratolites kan ’n besondere rol speel in die uitbreiding van huidige sateliet- en ander aardwaarnemingstoepassings. ’n Studie is gemaak oor die ontwikkeling van Aerostat platforms en die huidige stand van Stratolite ontwikkeling. Die mikpunt was om ’n lugskipstelsel te ontwikkel wat in staat is om ’n spesifieke posisie te handhaaf ten spyte van die invloed van wind. Die verskeidenheid van toepassings, waarvoor so ’n geostasionêre platform gebruik kan word, word genoem. ’n Dinamiese model van ’n lugskip is ontwikkel en die stelsel is in sagteware gesimuleer. Dit is gedoen om die moontlikheid te ondersoek om sulke Aerostats in die toekoms te ontwikkel. ’n Lugskipstelsel, wat aan die grond geanker word met ’n kabel, is ontwerp en gebou. Die stelsel is gedemonstreer en daar is bewys dat dit moontlik is om die posisie van die lugskip te beheer. Die lugskip gebruik huidige tegnologie wat in ’n unieke kombinasie saamgevoeg is om te illustreer dat dit moontlik is vir die lugskip om stasionêr te bly ten spyte van wind. Verskeie beheerstelsels ontwerptegnieke is gebruik om die beheerders mee te implementeer. Lineêre modelle van die lugskip is prakties geïdentifiseer en is gebruik om die beheerders te ontwerp. Die lugskip se beheerders is in simulasie sowel as prakties getoets en die resultate van hierdie toetse word gegee. Die projek bevestig dat daar ’n potensiaal bestaan vir die praktiese ontwikkeling van Stratolite stelsels. Daar is egter ’n hele paar uitdagings en probleme wat eers uit die weg geruim sal moet word, voordat hierdie tegnologie ’n alledaagse werklikheid sal word.

Diploma thesis concerns with design of a lookout airship. The work tries to find a solution to a problem, how to connect technology, ergonomics and aesthetics into design of new product. Analysis of complete dilemma leads to a new design of an airship, which should become a valuable aircraft for transporting passangers, travelling and flying untraditional sightseeing flights

Although there have been oscillations in airship interest since their use in the early 1900s, technological advancements and the need for more flexible and environmentally friendly transportation modes have caused a stream of study and surge in airship development in recent years. For companies and governments to understand how airships can be incorporated into their fleets to fulfil new or existing mission types, system design space exploration is an important step in understanding airships, their uses, and their design parameters. A decision support system (DSS), Design Exploration of Lighter-Than-Air Systems (DELTAS), was developed to help stakeholders with this task. DELTAS allows users to design airships and missions to determine how a design will perform in the scenario. Simulations can also be run for a given mission to find the Pareto-optimal designs for user-defined ranges of high-level airship design parameters. A case study is provided that demonstrates how DELTAS can be used to explore the airship design space for three specified missions. These three mission case studies show how design of experiments is important to more thoroughly cover the design space and to find and understand the relationships between airship design variables that lead to optimal mission times and costs. This research also explores the impacts of introducing an airship into operation. Engineered products have economic, environmental, and social impacts, which comprise the major dimensions of sustainability. This paper seeks to determine the interaction between design parameters when social impacts are incorporated into the concept development phase of the systems design process. Social impact evaluation is increasing in importance similar to what has happened in recent years with environmental impact consideration in the design of engineered products. Concurrently, research into new airship design has increased. Airships have yet to be reintroduced at a large scale or for a range of applications in society. Although airships have the potential for positive environmental and economic impacts, the social impacts are still rarely considered. This paper presents a case study of the hypothetical introduction of airships in the Amazon region of Brazil to help local farmers transport their produce to market. It explores the design space in terms of both engineering parameters and social impacts using a discrete-event simulation to model the system. The social impacts are found to be dependent not only on the social factors and airship design parameters, but also on the farmer-airship system, suggesting that socio-technical systems design will benefit from integrated social impact metric analysis. This thesis seeks to demonstrate how computer-aided engineering tools can be used to predict social impacts, to more effectively explore a system's design space, and to optimize the system design for maximum positive impact, using the modern airship as a case study.

The Unmanned Aerial Vehicle (UAV) has over the last years become an increasingly prevalent technology in several sectors of modern society. Many UAVs are today used in a wide series of applications, from disaster relief to surveillance. A recent initiative by the Swedish Sea Rescue Society (SSRS) aims to implement UAVs in their emergency response. By quickly deploying drones to an area of interest, an assessment can be made, prior to personnel getting there, thus saving time and increasing the likelihood of a successful rescue operation. An aircraft like this, that will travel great distances, have to rely on a navigation system that does not require an operator to continuously see the vehicle. To travel to its goal, or search an area, the operator should be able to define a travel route that the UAV follows, by feeding it a series of waypoints. As an initial step towards that kind of system, this thesis has developed and tested the concept of waypoint navigation on a small and slow airship/blimp, in a simulated indoor environment. Mainly, two commonly used navigation algorithms were tested and compared. One is inspired by a sub-category of machine learning: reinforcement learning (RL), and the other one is based on the rapidly exploring random tree (RRT) algorithm. Four experiments were conducted to compare the two methods in terms of travel distance, average speed, energy efficiency, as well as robustness towards changes in the waypoint configurations. Results show that when the blimp was controlled by the best performing RL-based version, it generally travelled a more optimal (distance-wise) path than the RRT-based method. It also, in most cases, proved to be more robust against changes in the test tracks, and performed more consistently over different waypoint configurations. However, the RRT approach usually resulted in a higher average speed and energy efficiency. Also, the RL algorithm had some trouble navigating tracks where a physical obstacle was present. To sum up, the choice of algorithm depends on which parameters are prioritized by the blimp operator for a certain track. If a high velocity and energy efficiency is desirable, the RRT-based method is recommended. However, if it is important that the blimp travels as short a distance as possible between waypoints, and a higher degree of consistency in its performance is wanted, then the RL-method should be used. Moving forward from this report, toward the future implementation of both methods in rescue operations, it would be reasonable to analyze their performance under more realistic conditions. This can be done using a real indoor airship. Looking at how hardware that do not exceed the payload of the blimp can execute both methods and how the blimp will determine its position and orientation is recommended. It would also be interesting to see how different reward function affect the performance of the blimp. / Den obemannade luftfarkosten (UAV) har under de senaste åren blivit en teknik vars användning blivit allt vanligare i flera sektorer av det moderna samhället. Olika sorters UAV robotar associeras idag med en omfattande serie användningsområden, från katastrofhjälp till övervakning. Ett nyligen påbörjat initiativ från svenska sjöräddningssällskapet (SSRS) syftar till att implementera drönare i deras utryckningar. Genom att snabbt sända drönare till platsen i fråga, kan en bedömning göras innan personal kommer dit, vilket sparar tid och ökar sannolikheten för en framgångsrik räddningsaktion. En farkost som denna, som kommer att resa långa sträckor, måste förlita sig på ett navigationssystem som inte kräver att en operatör kontinuerligt ser farkosten. För att resa till sitt mål, eller söka av ett område, bör operatören kunna definiera en resväg som drönaren följer genom att ge den en serie vägpunkter. Som ett inledande steg mot den typen av system har denna uppsats utvecklat och testat begreppet vägpunktsnavigering på ett litet och långsamt luftskepp/blimp, i en simulerad inomhusmiljö. Huvudsakligen testades och jämfördes två vanligt förekommande navigationsalgoritmer. En inspirerad av en underkategori till maskininlärning: förstärkningsinlärning (RL), och den andra baserad på rapidly exploring random tree (RRT) algoritmen. Fyra experiment utfördes för jämföra båda metoderna med avseende på färdsträcka, medelhastighet, energieffektivitet samt robusthet gentemot ändringar i färdpunktskonfigurationerna. Resultaten visar att när blimpen kontrollerades av den bästa RL-baserade versionen åkte den generellt en mer avståndsmässigt optimal väg än när den RRT-baserade metoden användes. I de flesta fallen visade sig även RL-metoden vara mer robust mot förändringar i testbanorna, och presterade mer konsekvent över olika vägpunktskonfigurationer. RRT-metoden resulterade dock vanligtvis i en högre medelhastighet och energieffektivitet. RL-algoritmen hade också problem med att navigera banor där den behövde ta sig runt ett hinder. Sammanfattningsvis beror valet av algoritm på vilka parametrar som prioriteras av blimpoperatören för en viss bana. Om en hög hastighet och energieffektivitet är önskvärd rekommenderas den RRT-baserade metoden. Men om det är viktigt att blimpen reser så kort avstånd som möjligt mellan färdpunkterna, och har en jämnare prestanda, bör RL-metoden användas. För att ta nästa steg, mot en framtida implementering av båda metoder i räddningsoperationer, vore det rimligt att analysera deras prestanda under mer realistiska förhållanden. Detta skulle kunna göras inomhus med ett riktigt luftskepp. Författarna rekommenderar att undersöka om hårdvara som inte överstiger blimpens maxlast kan utföra båda metodernas beräkningar och hur blimpen bestämmer sin position och orientering. Det skulle också vara intressant att se hur olika belöningsfunktioner påverkar blimpens prestanda.

Orientadores: Paulo Augusto Valente Ferreira, Ely Carneiro de Paiva / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-04T03:59:44Z (GMT). No. of bitstreams: 1 Faria_BrunoGuedes_M.pdf: 2340545 bytes, checksum: 440ff7a9aa46f5a39514e81423363750 (MD5) Previous issue date: 2005 / Resumo: Nos últimos anos tem-se observado um crescente interesse de empresas e instituições de pesquisa pelo desenvolvimento de veículos robóticos, dotados de diferentes níveis de capacidade de operação autônoma, objetivando a execução de diversas tarefas. Dentro deste contexto o CenPRA, Centro de Pesquisas Renato Archer, propôs o Projeto AURORA. O Projeto AURORA (Autonomous Unmanned Remote mOnitoring Robotic Airship) tem como seu principal objetivo o desenvolvimento de protótipos de veículos aéreos tele-operados, e a obtenção de veículos telemonitorados, através do desenvolvimento de sistemas com graus de autonomia crescentes. Para que se possam agregar níveis crescentes de autonomia ao veículo, é essencial incrementar seu sistema de controle e navegação de maneira gradativa. Por esse motivo o aprimoramento das estratégias de controle do sistema é essencial. Assim, é primordial possuir um modelo fidedigno do sistema físico em questão, pois somente dessa forma é possível elaborar leis de controle e testá-las imediatamente em simulação antes de partir para os ensaios práticos no veículo real. Além disso, um modelo adequado é essencial para a simulação do vôo do dirigível de forma a permitir a análise preliminar de seu comportamento diante de uma nova missão. O principal objetivo deste trabalho é a implementação e validação de metodologias para a identificação do modelo dinâmico longitudinal do dirigível. Foram abordadas três metodologias para a identificação do modelo dinâmico do dirigível: a identificação estacionária, que identifica os coeficientes aerodinâmicos do dirigível a partir de um vôo estacionário, a identificação dinâmica, que identifica esses coeficientes e a dinâmica linearizada do veículo a partir de um vôo com entradas de perturbação conhecidas e, finalmente, a identificação por meio de estratégias evolutivas, que procura otimizar alguns parâmetros do modelo dinâmico. As três metodologias foram testadas, validadas e comparadas através de ensaios de simulação, utilizando-se o simulador do dirigível AS800 do Projeto AURORA / Abstract: In recent years many research institutions and companies have been demonstrating a growing interest in the development of unmanned aerial vehicles with different autonomous operation levels in order to allow for the performance of many types of tasks. Within this context, CenPRA (Renato Archer Research Center) proposed the Project AURORA. Project AURORA (Autonomous Unmanned Remote Monitoring Robotic Airship) aims at the development of unmanned airships remotely operated with a view to the creation of an autonomous flight airship by the incorporation of increasing levels of autonomy. In order to increase the vehicle autonomy level, the development of a proportionally enhanced control and navigation systems is essential. It is extremely important to have a very accurate model of the physical airship system, given that this is the only way to design control laws for the vehicle and test them in simulation before performing actual flight tests. Moreover, an accurate model is essential to predict the vehicle behavior in simulation before any real flight demanding a new type of mission. The definition of identification methodologies for the AS800 airship system identification is the main scope of this work. Three methodologies were considered to allow the airship dynamic model identification: stationary identification, which identifies aerodynamic coefficients from stationary stabilized flight conditions; dynamic identification, which identifies these coefficients and the vehicle linear dynamics from the application of known inputs into the system; and, finally, through evolution strategies, which uses an evolutionary approach for the optimization of the aerodynamic coefficients of the dynamic model. All the methodologies were tested, validated and compared through simulation experiments by using the AS800 airship simulator of the Project AURORA / Mestrado / Automação / Mestre em Engenharia Elétrica