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The last decade has seen significant advances in the development of Vertical takeoff and landing (VTOL) unmanned aerial vehicles (UAVs). The emergence of enabling technologies, in addition to the practical usefulness of such systems has driven their development to a point where numerous technology demonstrators and commercial products are now in existence. Of particular interest has been the development of small scale, VTOL UAVs commonly referred to as mini and micro-VTOL UAVs. The versatility and agility of such vehicles offers great potential for the use in clustered, urban environments. Despite recent advancements, the autonomous navigation of VTOL UAVs remains a very challenging research area. The dynamics of VTOL UAVs are heavily nonlinear, underactuated and non-minimum phase. This, coupled with the aggressive maneuvers that such vehicles are expected to execute provides a stimulating problem in dynamic control. This is particularly true in the case of micro-VTOL UAVs. The fast, nonlinear nature of these systems render classical, linear control approaches inadequate. The past twenty years has seen great interest in the development of nonlinear control strategies. This has led to the emergence of a number of standard design tools, most notably feedback linearisation and Lyapunov-based, backstepping approaches. Such design techniques offer a framework for the derivation of model based control laws capable of achieving global stabilisation and trajectory tracking control for heavily nonlinear systems. Recently, there has been significant interest in the application of such nonlinear control paradigms for the stabilisation and control of VTOL UAVs. The aim of this thesis is to further the application and analysis of nonlinear control design techniques for the control of VTOL UAVs. In particular, focus is placed on Lyapunov-based, backstepping-type control approaches. The first half of this thesis investigates Lyapunov-based control strategies that cast the closed-loop VTOL dynamics into a globally stable, cascade structure. This work was directly inspired by, and builds on, a variety of previously published works. Firstly, an alternative design approach to that previously published is presented, resulting in an improved closed-loop dynamic structure. Although inspired by the VTOL system, this idea may be generalised for the control of a broad class of systems, and is presented as such. A singularity issue arising in the cascade control of VTOL vehicles is then investigated, and a novel approach to overcome this issue is formulated. The second half of this thesis is dedicated to the trajectory tracking control of VTOL UAVs at velocities where the influence of aerodynamics is significant. In general, the aerodynamic models of VTOL UAVs are heavily nonlinear and poorly known. The use of such models in a backstepping framework that uses explicit differentiation of these models for dynamic inversion is questioned, due to the potential sensitivity of such nonlinear models. Consequently, an alternative approach utilising coupled filters to avoid such sensitivity issues is proposed. All control designs formulated in this thesis are accompanied by proofs guaranteeing their global stability, and numerical simulations demonstrating their time domain response characteristics. / http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1298413 / Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 2007

Unmanned vehicles are often used in time-critical missions such as reconnaissance or search and rescue. To this end, this thesis provides autonomous localization and mapping tools for 1/R² sources. A "1/R²" source is one in which the received intensity of the source is inversely proportional to the square of the distance from the source. An autonomous localization algorithm is developed which utilizes a particle swarm particle ltering method to recursively estimate the location of a source. To implement the localization algorithm experimentally, a command interface with Virginia Tech's autonomous helicopter was developed. The interface accepts state information from the helicopter, and returns command inputs to drive the helicopter autonomously to the source. To make the use of the system more intuitive, a graphical user interface was developed which provides localization functionality as well as a waypoint navigation outer-loop controller for the helicopter. This assists in positioning the helicopter and returning it home after the the algorithm is completed. An autonomous mapping mission with a radioactive source is presented, along with a localization experiment utilizing simulated sensor readings. This work is the rst phase of an on-going project at the Unmanned Systems Lab. Accordingly, this thesis also provides a framework for its continuation in the next phase of the project. / Master of Science

Un concept innovant d'aéronef convertible a été imaginé pour des applications de drone tactique. La sustentation en mode hélicoptère est assurée par un rotor situé dans le nez de l'appareil et entraîné en rotation par des hélices montées sur ses pales. Le rotor s'arrête en vol pour faire office de plan canard et ses hélices propulsent l'appareil en mode avion. Une aile fixe est ajoutée dans la queue de l'appareil, dans le flux du rotor, pour soulager la charge de ce dernier quand il est arrêté. Ainsi, le design des hélices n'est plus surdimensionné pour sustenter l'appareil en mode hélicoptère, la dimension du rotor n'est plus limitée par le fonctionnement en mode avion et la majorité des systèmes est utilisée dans les deux modes, ce qui réduit la puissance nécessaire, le poids et la trainée aérodynamique. La faisabilité de ce concept a été démontrée au cours de ces travaux de thèse. Cette dernière comprend l'analyse du comportement du système rotor, l'étude des interactions entre les appendices aérodynamiques en vol stationnaire et le contrôle au cours de la transition entre vol stationnaire et vol horizontal. Les gains en performance de ce concept par rapport aux drones tactiques existants, en termes d'autonomie et de masse de charge utile embarquée, ont été évalués dans le cadre d'une étude de conception amont. Par ailleurs, le principe de rotor propulsé par hélice a été repris et exploité dans un nouveau concept breveté qui pallie les défauts inhérents aux drones multirotors. Ces derniers se révèlent, en effet, intrinsèquement peu fiables en raison de la complémentarité de leurs différents systèmes propulsifs. / An innovative concept of convertible aircraft, conceived primarily for tactical UAV applications, is proposed as part of this thesis. The lift in helicopter mode is provided by a rotor located in the nose of the aircraft and driven in rotation by propellers mounted on its blades. The rotor stops in flight to act as a canard and its propellers propel the whole aircraft into airplane mode. A fixed wing is added to the tail, in the rotor flow, to alleviate the latter’s load when it is stopped. This removes the previous need for oversized propellers necessary to sustain the aircraft in helicopter mode. The size of the rotor is also no longer limited by airplane operations and almost all the UAV’s systems are used in both modes. This has the great advantage of reducing the required power, the weight and the aerodynamic drag. The feasibility of this concept has been demonstrated throughout the thesis work which includes rotor system behaviour analysis, the study of interactions between the different hovering aerodynamic systems and the design of the control during the transition between hover and horizontal flights.The performance gains of this concept over existing tactical drones, in terms of autonomy and on-board payload mass, were evaluated as part of conceptual design study. A model has been produced in order to demonstrate the feasibility of the concept’s production. The propeller-driven rotor principle, developed in this thesis, was carried over and implemented in a new patented concept which overcomes the inherent defects of multi-rotor drones.

The usage of unmanned aerial vehicles in applications such as terrain mapping and surveillance is proliferating in the modern world. This project aims to investigate the feasibility, in terms of payload capacity and stability, of small scale winged aircraft that have the ability to lift and land vertically, while also being able to transition to normal forward flight using wings for primary lift. The prototype aircraft was built with the limitation of using only one lift-producing motor that would be responsible for both vertical take-off and landing, and the horizontal propulsion in forward flight. The prototype was built primarily using 3D-printed plastic with an electric ducted fan as the method of propulsion. Internal ducting was used to redirect airflow downwards, from the only propulsion source to achieve vertical lift at a standstill. The final iteration of the aircraft successfully performed multiple hovers over 30 seconds long but did not have wings to test a transition to forward flight. Lifting capacity was low but the concept proposed in this thesis holds promise for further development and optimization. / Användningen av obemannade luftfarkoster för tillämpningar såsom terrängkartläggning och övervakning ökar i den moderna världen. Detta projekt syftar till att undersöka lämpligheten, i termer av lastkapacitet och stabilitet, för småskaliga vingade luftfarkoster som har förmågan att lyfta och landa vertikalt, samtidigt som de kan övergå till normal framåtflygning med vingar för primär lyftkraft. Prototypen av luftfarkosten byggdes med begränsningen att endast en lyftproducerande motor skulle användas, som skulle vara ansvarig för både vertikal lyftning och horisontell framdrivning vid framåtflygning. Prototypen byggdes främst med 3D-utskrivna plastkomponenter med en elektrisk innesluten fläkt som källa för dragkraft. Interna luftkanaler användes för att omdirigera luftflödet nedåt, från den enda lyftproducerande motorn, för att uppnå vertikal lyftkraft vid ett stillastående. Den slutliga versionen av luftfarkosten utförde flera svävningar i över 30 sekunder, men farkosten hade inga vingar för att testa övergången till framåtflygning. Lastkapaciteten var låg, men konceptet som föreslogs i denna avhandling är lovande för vidare utveckling och optimering.

As aeronaves do tipo multirrotor vêm sendo utilizadas como plataforma padrão para o estudo da motricidade e percepção espacial. A capacidade de decolagem e aterrissagem de modo vertical, bem como sua navegação horizontal são desafios de investigação na área de controle. Isto demanda a obtenção do modelo matemático do conjunto de propulsão eletromecânico. Assim, surge a necessidade de compreender e modelar matematicamente a dinâmica deste sistema de forma a otimizar, posteriormente, o seu controle. Portanto, o objetivo deste trabalho é obter o modelo matemático do sistema de propulsão eletromecânico, usando para tal a teoria de identificação de sistemas. A metodologia utilizada consiste na compreensão do sistema de propulsão e construção da plataforma de testes para a coleta de dados. Seguida da aplicação de testes de estacionariedade para a análise dos dados, e cálculo das funções de autocorrelação e autocorrelação parcial para determinação da estrutura e ordem do modelo. Posteriormente, os parâmetros são estimados pelo método de mínimos quadrado estendido. Por fim, pela comparação da simulação do modelo com os dados da plataforma e a análise residual, o modelo é validado. Diante disso, conclui-se que o modelo proposto é capaz de descrever as características do sistema de propulsão eletromecânico e poderá contribuir para novas técnicas de controle. / 111 f.

When considering the operation of an Unmanned Aerial Vehicle (UAV) or an Unmanned Ground Vehicle (UGV), such problems as landing site estimation or robot path planning become a concern. Deciding if an area of terrain has a level enough slope and a wide enough area to land a Vertical Take Off and Landing (VTOL) UAV or if an area of terrain is traversable by a ground robot is reliant on data gathered from sensors, such as cameras. 3-D models, which can be built from data extracted from digital cameras, can help facilitate decision making for such tasks by providing a virtual model of the surrounding environment the system is in. A stereo vision system utilizes two or more cameras, which capture images of a scene from two or more viewpoints, to create 3-D point clouds. A point cloud is a set of un-gridded 3-D points corresponding to a 2-D image, and is used to build gridded surface models. Designing a stereo system for distant terrain modeling requires an extended baseline, or distance between the two cameras, in order to obtain a reasonable depth resolution. As the width of the baseline increases, so does the flexibility of the system, causing the orientation of the cameras to deviate from their original state. A set of tools have been developed to generate 3-D point clouds from rigid and flexible stereo systems, along with a method for applying corrections to a flexible system to regain distance accuracy in a flexible system. / Master of Science

A non switching, non linear, quaternion based attitude P2 controller, together with a sensitivitynormalizing function for the control surfaces has been simulated and implemented on a flying fixedwing with non vectored engines. In simulations the controller worked well in all flight modes,hovering, transition and flying, and also rejected a simple wind disturbance in all modes. Thefirst implementation on hardware did not work due to programming errors causing crashes withunrepairable damages. The second aircraft was built out of a piece of plywood to further simplifythe testing and tolerate more crashes. A flat plate, a flying piece of plywood, is not a proper airfoiland so has no effects due to camber. It is therefore easier to both simulate and tune. The controllerworked acceptable in reality, but does need further tuning. Due to time constraints the weighingof airflow inside and outside the propeller wash could not be fully determined resulting in differentgain in the different flight modes, but initial estimation of the parameters were enough to achieverobust, stable hovering transitioning and flying even in winds stronger than 5m/s.The controllerwas not implemented on an EcoSoar due to time constraints, but the proof of concept flying pieceof plywood proved the controller feasible for future embedding in a modified EcoSoar. A VTOLcapable EcoSoar could be used for critical deliveries in for example the medical field in Malawiwhere suboptimal infrastructure is hindering progress. The need for medical supplies around therural parts of Malawi is great but roads and services are not capable yet. Since a VTOL flyingwing with delivery capabilities can be both cheap to build, and deliver supplies to areas withoutan airfield, it could accelerate development in Malawi and thus greatly increase quality of life forhumans.

This report summarizes the task of conceptually designing an UAV suited for agricultural observation of Swedish farmland. The design of the UAV was divided into two parts. This report focuses on the flight mechanics, performance analysis, and cost analysis of the UAV, whereas the other part centers around the aerodynamic performance. Therefore, some elements, such as the wing selection, will not be subject to discussion in this report. A set of different requirements were posed, such as having a flight time longer than two hours, being able to between 5-10 m/s, able to perform vertical take-off and landing, fly at a maximum of 100 meters, and weighing less than 5 kg. By using different sources of literature, reasonable assumptions, and Matlab analytics, a UAV was designed that met all constraints demanded. The cost analysis yielded a result that was reasonable, which overall makes this conceptual UAV a realistic product that could be manufactured using the project design.