Traditional wireless site surveys produce a heat-map of link strength or quality over a target area, usually on the ground plane. In recent years research has gone into using aerial drones in network attack and surveillance, making three dimensional awareness of wireless coverage areas of interest. A multi-rotor drone and data collection module were built and tested as part of this research. Site assessments were conducted both in open space and near structures. Collected data was interpolated across the target area, and visualized as points and contours. These visualizations were exported to a Keyhole Markup Language (KML) for visualization in context. Resulting visualizations proved to be beneficial in identifying the coverage area of both authorized and rogue access points.

In recent years, the interest in quadcopters as a robotics platform for autonomous photography has increased. This is due to their small size and mobility, which allow them to reach places that are difficult or even impossible for humans. This thesis focuses on the design of an autonomous quadcopter videographer, i.e. a quadcopter capable of capturing good footage of a specific subject. In order to obtain this footage, the system needs to choose appropriate vantage points and control the quadcopter. Skilled human videographers can easily spot good filming locations where the subject and its actions can be seen clearly in the resulting video footage, but translating this knowledge to a robot can be complex. We present an autonomous system implemented on a commercially available quadcopter that achieves this using only the monocular information and an accelerometer. Our system has two vantage point selection strategies: 1) a reactive approach, which moves the robot to a fixed location with respect to the human and 2) the combination of the reactive approach and a POMDP planner that considers the target's movement intentions. We compare the behavior of these two approaches under different target movement scenarios. The results show that the POMDP planner obtains more stable footage with less quadcopter motion.

Investigation of complex multirotor aerodynamic phenomena via wind tunnel experimentation is becoming extremely important with the rapid progress in advanced distributed propulsion VTOL concepts. Much of this experimentation is being performed in large, highly advanced tunnels. However, the proliferation of this class of vehicles extends to small aircraft used by small businesses, universities, and hobbyists without ready access to this level of test facility. Therefore, there is a need to investigate whether multirotor vehicles can be adequately tested in smaller wind tunnel facilities. A test rig for a 2.82-pound quadcopter was developed to perform powered testing in the Cal Poly Aerospace Department’s Low Speed Wind Tunnel, equipped with a 3-foot tall by 4-foot wide test section. The results were compared to data from similar tests performed in the U.S. Army 7-by 10-ft Wind Tunnel at NASA Ames. The two data sets did not show close agreement in absolute terms but demonstrated similar trends. Due to measurement uncertainties, the contribution of wind tunnel interference effects to this discrepancy in measurements was not able to be properly quantified, but is likely a major contributor. Flow visualization results demonstrated that tunnel interference effects can likely be minimized by testing at high tunnel speeds with the vehicle pitched 10-degrees or more downward. Suggestions towards avoiding the pitfalls inherent to multirotor wind tunnel testing are provided. Additionally, a modified form of the conventional lift-to-drag ratio is presented as a metric of electric multirotor aerodynamic efficiency.

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An original approach for measuring wind speed and direction by the use ofdrones was proposed and compared to an existing one. The original approach allowed the drone to drift with the wind and use the translatory velocity for input into a non-linear estimator, while the existing approach used a stationary hovering drone and its tilt for input to an estimator. A simulation environment was set up in Simulink and Matlab and validated using outputs from previous researchers performing similar tasks. The first test exposed the two approaches to wind tunnel-like environment with a strictly horizontal wind, while the second test used real wind data collected on-board a meteorological research vessel. Results showed that the original approachperformed better for estimating both direction and speed, but it required a largearea to drift in during operation. / En egen teknik för att mäta vindhastighet och vindrikting med en drönare föreslogs och jämfördes med en befintlig teknik. Det egna sättet tillät drönaren att driva med vinden och använde dess egna hastighet för att estimera vinden, medan den existerande tekniken höll drönarens position konstant och estimerade vinden med hjälp av farkostens lutning. En simuleringsmiljö inrättades i Simulink och Matlab som validerades medhjälp av resultat från tidigare liknande forskning. Det första testet som genomfördes exponerade de två tillvägagångsätten för vindtunnel-liknande förhållanden, medan det andra testet använde verklig vinddata som samlats in ombordett meteorologiskt forskningsfartyg. Resultaten visade att den egna teknikenproducerade noggrannare upskattningar av både vindhastighet och riktning,men krävde betydligt större fritt flygrum.

This thesis presents the design, modeling, and control of a fully-actuated multi-rotor unmanned aerial vehicle (UAV). Unlike conventional multi-rotors, which suffer from two degrees of underactuation in their propeller plane, the choice of an unconventional propeller configuration in the new drone leads to an even distribution of actuation across the entire force-torque space. This allows the vehicle to produce any arbitrary combination of forces and torques within a bounded magnitude and hence execute motion trajectories unattainable with conventional multi-rotor designs. This system, referred to as the \omninospace, decouples the position and attitude controllers, simplifying the motion control problem. Position control is achieved using a PID feedback loop with gravity compensation, while attitude control uses a cascade architecture where the inner loop follows an angular rate command set by the outer attitude control loop. A novel model is developed to capture the disturbance effects among interacting actuator airflows of the \omninospace. Given a desired actuator thrust, the model computes the required motor command using the current battery voltage and thrusts of disturbing actuators. A system identification is performed to justify the use of a linear approximation for parameters in the model to reduce its computational footprint in real-time implementation. The \omni benefits from two degrees of actuation redundancy resulting in a control allocation problem where feasible force-torques may be produced through an infinite number of actuator thrust combinations. A novel control allocation approach is formulated as a convex optimization to minimize the \omnis energy consumption subject to the propeller thrust limits. In addition to energy savings, this optimization provides fault tolerance in the scenario of a failed actuator. A functioning prototype of the \omni is built and instrumented. Experiments carried out with this prototype demonstrate the capabilities of the new drone and its control system in following various translational and rotational trajectories, some of which would not be possible with conventional multi-rotors. The proposed optimization-based control allocation helps reduce power consumption by as much as 6\%, while being able to operate the drone in the event of a propeller failure. / Thesis / Master of Applied Science (MASc)

Studien handlade om att belysa hur UAV:s kan komma till nytta i meteorologisk forskning och att ta reda på hur bra drönare är på att mäta meteorologiska storheter. Drönare, som också kallas UAV:s (Unmanned Aerial Vehicle) är mindre obemmanade luftfartyg som kan flyga autonomt eller fjärrstyras. Idag används drönare alltmer i meteorologi vilket beror mycket på den tekniska utvecklingen. Exempel på meteorologiska applikationer är mätning av vindhastighet och koncentrationen av koldioxid i luften som kan användas för att studera de lägsta atmosfäriska skikten. Storheter som mättes i detta projekt var vindhastighet, vindriktning, temperatur och relativ fuktighet på olika höjder. Mätningarna gjordes två gånger i en mätstation i Marsta, som ligger utanför Uppsala. Efteråt jämfördes datan från drönaren med data från en instrumenterad mast vid väderstationen. Resultaten visade att drönarens vindprofiler stämde ganska väl överens med mastens vindprofiler och den logaritmiska vindlagen. Under den första fältmätningen uppskattade drönaren att vindhastigheten var 8.13 ± 1.33 m/s vid hovring på tio meters höjd medan masten angav 8.41 ± 0.958 m/s. Drönarens mätvärden för vindriktningen var ibland bra och ibland mindre bra. Mätvärdena för temperaturen och den relativa fuktigheten avvek med upp mot 1 ◦C respektive 10 procentenheter. / The aim of this report was to study how UAV:s can be applied in meteorological research and find out how good drones are at measuring meteorological parameters. A drone, also known as an UAV (Unmanned Aerial Vehicle) is a smaller unmanned aircraft that can fly autonomously or under remote control. Today, drones are used more frequently in meteorology, mostly due to the recent technological development. Examples of meteorological applications include measurements of wind speed and the amount of carbon dioxide in the air which can be used to analyze the lower parts of the atmosphere. In this project, the wind speed and its direction, the temperature and the relative humidity were measured at different heights. The measurements took place twice in Marsta which is a field station outside Uppsala. Then, the data from the drone was compared to the data from a weather tower at the instrumented station. The results showed that the drone’s wind profiles were relatively similar to the profiles according to the tower and the logarithmic wind profiles. For instance, during the first flight the drone estimated the wind speed to be 8.13 ± 1.33 m/s while hovering ten metres above the ground. The tower measured 8.41 ± 0.958 m/s at the same height. The drone’s estimations of the wind direction were sometimes accurate and sometimes not accurate. The temperature and relative humidity however was different by 1 ◦C and ten percentage units respectively.

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Orientador: Prof. Dr. Wagner Tanaka Botelho / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Ciência da Computação, 2017. / Os avanços tecnológicos realizados na robótica móvel ao longo do tempo requereram o estudo e desenvolvimento de robôs cada vez mais autônomos e complexos, capazes de se adaptarem aos ambientes e condições que lhe são impostas. Contudo, dependendo do objetivo a alcancar, torna-se mais efetivo a utilização de uma maior quantidade de robos menores e mais simples, com capacidade cooperativa, resultando em um sistema escalavel e menos suscetývel a falhas gerais, denominado Sistema Multirrobotico (SMR). Tendo um SMR como objeto de estudo principal, este trabalho consiste no desenvolvimento de uma arquitetura multirrobotica descentralizada para o controle de posição e formação utilizando quadricopteros. A arquitetura é composta por n quadricopteros virtuais, implementados no software de simulação Gazebo e um quadricoptero real. O Robot Operating System (ROS) controla todos os quadricopteros, alem de gerenciar a comunicação entre os agentes roboticos. Um ponto importante é que, visando a diminuição dos custos do projeto, foi utilizado apenas um quadricoptero real, uma vez que somente um é necessário para validar a integração entre os mundos virtual e real. Para o controle de posição e formação foram propostos modelos matematicos que determinam as trajetorias dos n quadricopteros em formação linear, formação de figuras poligonais com troca de posição e formação de figuras poligonais com troca de posição e ponto de referencia movel. Nas simulações, foi possivel observar o deslocamento dos quadic'opteros em formação, validando os modelos matematicos. Por'em, no experimento real, a trajetoria no controle de formação foi parcialmente observada devido a alguns problemas apresentados na estrutura do quadricoptero e tambem por não possuir um sistema de sensoriamento no ambiente real. Apesar desses problemas, a integração entre os mundos virtual e real também foi validada. / The technological advances made in mobile robotics over time have required the study and development of robots that are increasingly autonomous and complex, capable of adapting to the environments and conditions that are imposed on them. However, depending on the goal to be achieved, it becomes more e.ective to use a larger number of smaller and simpler robots with cooperative capability, resulting in a scalable system that is less susceptible to general failures, called Multi-Robot Systems (MRS). Considering a MRS as the main study, the main target in this work is to develop a descentralized multi-robot architecture for position control using quadcopters. The architecture consists of n virtual quadcopters, implemented on the Gazebo simulation software and a real quadcopter. The Robot Operating System (ROS) controls all quadcopters as well as managing communication between them. In order to reduce the project costs, only one real quadcopter was used, since it is enough to validate the integration between the virtual and real worlds. The mathematical models were proposed to calculate the paths of the quadcopters in linear formation, formation of polygonal figures with rotation and formation of polygonal figures with rotation and mobile reference point. In the simulations, it was possible to observe the displacement of the quadcopters in formation, validating the mathematical models. However, in the real experiment, the trajectory in the formation control was partially observed due to some limitations presented on the quadcopter structure. Also, the sensing system was not available in the real environment. Despite these problems, the integration between the virtual and real worlds has also been validated.