| 11. |
- Behar, Etienne
(författare)
-
Solar Wind Dynamics within The Atmosphere of comet 67P/Churyumov-Gerasimenko
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, we explore the dynamics of the solar wind as it perme-ates and flows through a tenuous cometary atmosphere, with a focuson the interaction observed at comet 67P/Churyumov–Gerasimenko.Seven comets had already been visited by nine different probes when the European spacecraft Rosetta reached comet Churyumov–Gerasimenko in August 2014. The mission was however the first to orbit its host comet, which it did for a total duration of more than two years, corre-sponding to a large part of the comet’s orbit around the Sun. This en-abled to study how the dynamics of the plasma environment evolvedas the comet itself was transformed from one of the smallest obstaclesto the solar wind in the Solar System when far away from the Sun, toa well-established magnetosphere at perihelion.Most of our efforts tackle the early part of this transformation, when the creation of new-born cometary ions starts to induce significant disturbances to the incident flow. During this stage, a kinetic descrip-tion of the interaction is necessary, as the system of interest cannot be reduced to a hydrodynamic problem. This contrasts with the situation closer to the Sun, where a fluid treatment can be used, at Churyumov–Gerasimenko as well as at previously visited comets.Rosetta was not a mission dedicated to plasma studies, however. It directly translates into a limited spatial coverage of the cometary plasma environment, which by its nature extends over several spatial scales. An approach solely based on the analysis of in-situ data cannot properly address the major questions on the nature and physics of the plasma environment of Churyumov–Gerasimenko. This thesis there-fore largely exploits the experimental–analytical–numerical triad of approaches. In Chapters 3 and 4 we propose simple models of the ion dynamics and of the cometary plasma environment, and these are tested against experimental and numerical data. Used together,they give a global description of the solar wind ion dynamics through the cometary atmosphere, that we explore in the 2-dimensional and 3-dimensional cases (Chapter 5). In Chapter 6, we propose a view onthe interaction and its fluid aspects when closer to the Sun.
|
|
| 12. |
- Brethes, Anaïs
(författare)
-
An integrated study of geological, magnetic and electromagnetic data for mineral exploration in the Jameson Land Basin, central East Greenland
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Jameson Land Basin, located in central East Greenland, initiated in Devonian time with the collapse of the over-thickened Caledonian Orogen. The basin developed during different phases of rifting from the late Paleozoic to the Mesozoic and has accumulated between 16-18 km of sediments. In Paleogene time, the basin was affected by intense magmatism due to the opening of the North Atlantic Ocean c. 55 Ma ago. Due to a significant uplift in Miocene time, the sedimentary sequence is well exposed along the basin margins, revealing numerous mineral occurrences hosted within almost the entire stratigraphic succession. The major types of mineralization comprise: (1) intrusion-related Mo (± Pb, Zn, Cu, Ag) mineralization associated with Paleogene intrusive complexes; (2) stratabound and/or stratiform Cu, Pb, Zn, (Ag) within Upper Permian and Triassic clastic and marine sedimentary formations; (3) stratabound and structurally controlled Pb-Zn, Cu, Ba, (Sr) mineralization in Upper Permian carbonates; and (4) structurally-controlled Pb, Zn, Cu (±Sb, Bi, Ag, Au) vein-type mineralization within Caledonian and Paleozoic rocks.It is well acknowledged that structures such as faults, thrusts, detachments, shear zones and associated fracture systems play an important role as fluid conduits connecting metal sources and sites of mineral precipitation. In particular, previous studies showed that mineral occurrences within the East Greenland Caledonides are closely related to lineaments and intrusions. In this context, the Crusmid-3D project was initiated in 2014, aiming at establishing the links between the crustal structures and the mineral occurrences in the Jameson Land Basin using a combination of geological and geophysical data. The interest for mineral exploration in the area led exploration companies and institutions to carry out magnetic and electromagnetic surveys, and the data derived from these constitute the base of this study.This thesis provides a detailed structural interpretation of aeromagnetic data in the Jameson Land Basin where several magnetic trends associated with Tertiary dikes and sills as well as with reactivated Paleozoic and Triassic faults were delineated. These data, in combination with a literature review and compilation of the mineral occurrences in the Jameson Land Basin, allowed highlighting seven prospective areas for structurally-controlled base metal mineralization.New structural data from geological fieldwork, drilling results and geophysical data (magnetic, electromagnetic and seismic data) along the eastern margin of the basin allowed a new interpretation of the geometry of the Triassic rift in East Greenland, represented by NE-SW-trending basins and highs segmented by NW-SE-trending transfer zones. It can be correlated with its European conjugate margin, displaying analogies with the Triassic Froan and Helgeland Basins in the Norwegian offshore and with the Papa and West Shetlands Basins north of the Shetland Islands.The proposed structural model of the Triassic rift was further investigated using 3D-geologically-constrained inversion of magnetic data in order to refine the architecture of the eastern margin of the Jameson Land Basin. Modelling results confirmed the presence of a shallow westward dipping peneplained crystalline basement in the southern part of the area while the northern part is characterized by faulted blocks, which accommodated relatively thick red bed sedimentary sequences, thereby representing a good potential source of base metals.Furthermore, Induced Polarization (IP) effects observed in airborne time-domain electromagnetic data acquired in the eastern margin of the basin were investigated using Self-Organizing Maps (SOM). The analysis of the shape and amplitude of the transient response curves using the SOM allowed identifying four areas where the transient curve patterns exhibit strong IP effects. These are shown to be collocated with Tertiary sills and dikes, clay-altered rocks as well as with a sulfide-bearing brecciated granite and with Triassic stratigraphic horizons hosting disseminated base metal sulfides.
|
|
| 13. |
- Calner, Tommy
(författare)
-
Persistent musculoskeletal pain : A web-based activity programme for behaviour change, does it work? Expectations and experiences of the physiotherapy treatment process
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis concerned persons with persistent musculoskeletal pain in primary health care and had three aims. The first aim was to evaluate the effects of a web-based programme for behaviour change. The second aim was to create and evaluate a multimodal intervention. The third aim was to explore and describe expectations andexperiences of the physiotherapy treatment process.In Study I, we evaluated the effects of a web-based activity programme for behaviour change added to multidisciplinary rehabilitation (MDR) in primary health care. Ninety-nine participants were randomized to 1) MDR with an additional web-based programme, and 2) MDR. Outcome measures were work ability, pain intensity, pain-relate disability and health-related quality of life. There were no significant effects of the web-based programme for any outcome measure at 4 or 12 months. In conclusion, this study provides no support for adding a self-guided web-based programme to MDR in primary health care.In Study II, we evaluated first the web-based programme from Study I compared to the waiting list. Effect measures were workability, pain intensity, disability and self-efficacy. Thereafter, we evaluated the effects and process of a novel multimodal intervention consisting of the web-based programme with additional individual counselling, and individually tailored physiotherapy treatment. Ten participants were included in the study. Effects were evaluated using a Single Subject Experimental Design (SSED) and the process was evaluated by interviews with the participants and log data of usage of the modalities. There were no conclusive effects of the self-managed web-based programme as compared to the waiting list. The SSED analyses of the multimodal intervention showed promising short-term results regarding disability and pain intensity, but no conclusive results for work ability or self-efficacy. The multi-modal intervention process seemed successfully implemented, and the importance of physiotherapy and, to some extent counselling, was emphasized by the participants. In conclusion, the newly designed multimodal intervention in primary health care seemed feasible and showed some promising short-term effects, while the implementation of a self-managed web-based programme as a single intervention seemed without effect.In Study III, qualitative interviews were conducted with ten participants to explore their expectations of physiotherapy. Data were analysed with qualitative content analysis and the findings described a multi-faceted picture of the participants’ expectations, encompassing several aspects regarding the treatment process and outcome. Regarding the treatment process, participants expected a good dialogue, to be confirmed as individuals, and to get an explanation for their pain. The participants expected tailored training with frequent follow-ups and their expectations of outcome ranged from hope of the best possible results to being realistic or resigned.In Study IV, qualitative interviews were conducted with 11 participants to explore their experiences in physiotherapy treatment. Data were analysed with qualitative content analysis. The findings show how the participants described how they used knowledge, awareness, movements and exercises learned from the physiotherapy treatment to develop strategies to manage pain and the process of acceptance. There were experiences involving the importance of establishing an alliance with the physiotherapist, based on trust and with a continuous dialogue. When exercises, activities and other treatment modalities were individualized, participants were actively involved in the process. This was rewarding but was also considered an effort and a challenge. The physiotherapist’s initiatives and actions were considered important for incentive and support.In conclusion, we found no effects of the web-based activity programme on behaviour change for persons with persistent musculoskeletal pain. The newly designed multi-modal intervention in primary health care seemed feasible and showed some promising short-term effects. Expectations of physiotherapy treatment were multi-faceted, encompassing both process and outcome. After finishing physiotherapy, the participants described how they used knowledge, awareness, movements and exercises learned from the physiotherapy treatment to develop strategies to manage pain and the process of acceptance. The importance of alliance and incentives for activities throughout the physiotherapy treatment process were also described.
|
|
| 14. |
- Carvalho, Lara, 1978-
(författare)
-
Opportunities to broaden biomass feedstocks in thermochemical conversion technologies
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Global environmental concerns are motivating a growing interest in broadening the biomass feedstock base in several energy sectors, including (i) the domestic heating sector, presently dominated by stem wood combustion, and (ii) biofuel production, presently dominated by edible crops. The objective of this thesis is to investigate new opportunities to broaden the biomass feedstock in thermochemical conversion technologies. The performance of different feedstocks was therefore investigated for (i) heat production in small-scale combustion systems and (ii) biofuel production in large-scale gasification-based plants. The selected feedstocks were agricultural residues, forest wood, pyrolysis liquid and industrial by-products, such as lignin, black liquor, crude glycerol and fermentation residues.The alkali metals content in biomass has an important role in combustion and gasification. Alkali metals can cause ash-related problems in small-scale combustion systems, while they can catalyse gasification reactions thus increasing conversion efficiency. Keeping this effect in mind, the present investigation was based on combustion tests with pelletised agricultural residues (non-woody feedstocks with ash contents of 3-8 wt% on a dry basis) to evaluate their combustion feasibility in several small-scale appliances. Moreover, the potential techno-economic benefits of alkali addition in gasification-based biofuel plants were investigated in two different systems: (i) stand-alone biofuel plant operated with wet-alkali-impregnated forest residues and alkali-rich lignin as well as (ii) biofuel plant integrated with a Kraft pulp mill operated with black liquor (an inherently alkali-rich feedstock) mixed with different blend ratios of pyrolysis liquid, crude glycerol or fermentation residues (co-gasification concept). The techno-economic analysis in large-scale entrained-flow-gasification-based biofuel plants was made with the help of simulation tools.The combustion tests have shown that high alkali feedstocks lead to problems with ash accumulation and slag formation in small-scale appliances. The results indicated that non-woody feedstocks can only be burned in appliances adapted to manage high ash content feedstocks. Effective ash cleaning and enhanced combustion controlling mechanisms are relevant characteristics to have in appliances when using these feedstocks. It has been shown that four out of the seven selected feedstocks can be burned in small-scale appliances, while fulfilling the legal European requirements (EN 303-5:2012) in terms of combustion efficiency and emissions. The nitrogen content and ash composition were shown to be important parameters to evaluate whether a feedstock can be utilised in small-scale combustion appliances.The techno-economic investigations of the gasification-based biofuel plants have shown that alkali impregnation is an attractive option to increase energy performance and downstream biofuel production. The economic assessment has indicated that alkali impregnation does not significantly increase biofuel production costs, while it allows the application of a new syngas cleaning system that can significantly reduce biofuel production costs. The present study has shown that the vi co-gasification concept has also techno-economic benefits as a result of the (i) alkali content in black liquor and (ii) economy-of-scale effects. These benefits can be enhanced by choosing energy-rich and low-cost blend-in feedstocks. The gasification-based biofuel production routes hereby investigated exhibit a good economic performance since biofuel required selling prices were economically competitive with other biofuel production routes as well as with taxed gasoline.
|
|
| 15. |
- Chapman, David, 1972-
(författare)
-
Urban design of winter cities : Winter season connectivity for soft mobility
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- All across the world the form of the built environment is playing a crucial role as enabler or inhibitor for urban outdoor activity such as soft mobility. Urban form can make it more attractive for people to be mobile outdoors and playing a role in the public life, or it can put people off venturing outside. For winter cities, a question for urban design is how we can design environments that are attractive for outdoor activity in the winter season as well as summer and additionally how will climate change influence these aspects.The reason for studying this is the importance of understanding how, in relation to urban form, weather, seasonal variations, and climate change influences human outdoor activity. In this study the focus on outdoor activity is problematised around the concern that people spend a low percentage of their time outdoors in winter conditions. For society, the problem is that this trend and the related low levels of physical activity are associated with a range of health issues.To study this the main question for this research is what attracts and hinders soft mobility during the winter season and how can this knowledge underpin new considerations about urban design for connectivity in winter cities? To address this, the research methods focused on document studies, surveys, mental mapping, photo elicitation and semi-structured discussions.The study works at three scientific levels. Firstly, it seeks to understand the interrelationship between the built environment and people’s outdoor activity in winter. Secondly, it attempts to understand how connectivity for soft mobility in winter is being affected by weather and climate change. Thirdly, it seeks new ways of thinking about how the urban form can be designed to increase outdoor soft mobility in winter.The discussion and conclusions focused on the argument that in winter settlements, the winter season can alter spatial patterns and settlement organisation. Here it was argued that in these settlements the winter season can be an aspect of urban morphology and can be part of the process of shaping the public realm and its connectivity for soft mobility in winter.
|
|
| 16. |
- Dadhich, Siddharth, 1987-
(författare)
-
Automation of Wheel-Loaders
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Automation and tele-remote operation of mobile earth moving machines is desired for safety and productivity reasons. With tele-operation and automation, operators can avoid harsh ergonomic conditions and hazardous environments with poor air quality, and the productivity can in principle be improved by saving the time required to commute to and from work areas. Tele-remote operation of a wheel-loader is investigated and compared with manual operation, and it is found that the constrained perception of the machine is a challenging problem with remote operations. Real-time video transmission over wireless is difficult, but presents a way towards improving the remote operator’s quality of experience. To avoid glitches in the real-time video, arising from variable wireless conditions, the use of SCReAM (Self-Clocked Rate Adaptation for Multimedia) protocol is proposed. Experiments with a small scale robot over LTE show the usefulness of SCReAM for time-critical remote control applications. Automation of the bucket-filling step in the loading cycle of a wheel-loader has been an open problem, despite three decades of research. To address the bucket-filling problem, imitation learning has been applied using expert operator data, experiments are performed with a 20-tonne Volvo L180H wheel-loader and an automatic bucket-filling solution is proposed, developed and demonstrated in field-tests. The conducted experiments are in the realm of small data (100 bucket-filling examples), shallow time-delayed neural-network (TDNN), and a wheel-loader interacting with a non-stationary pile-environment. The total delay length of the TDNN model is found to be an important hyperparameter, and the trained and tuned model comes close to the performance of an expert operator with slightly longer bucket-filling time. The proposed imitation learning trained on medium coarse gravel succeeds in filling buckets in a gravel cobble pile. However, a general solution for automatic bucket-filling needs to be adaptive to possible changes in operating conditions. To adapt an initial imitation model for unseen operating conditions, a reinforcement learning approach is proposed and evaluated. A deterministic actor-critic algorithm is used to update actor (control policy) and critic (policy evaluation) networks. The experiments show that by use of a carefully chosen reward signal the models learns to improve and maximizes bucket weights in a gravel-cobble pile with only 40 bucket-filling trials. This shows that an imitation learning based bucket-filling solution equipped with a reinforcement learning agent is well suited for the continually changing operating conditions found in the construction industry. The results presented in this thesis are a demonstration of the use of artificial intelligence and machine learning methods for the operation of construction equipment. Wheel-loader OEMs can use these results to develop an autonomous bucket-filling function that can be used in manual, tele-remote or fully autonomous operations.
|
|
| 17. |
- De Lauretis, Maria, 1987-
(författare)
-
Multiconductor transmission lines wideband modeling : A delay-rational Green’s-function-based method
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The performance of variable-frequency drives (VFDs) commonly used in energy production plants can be severely affected by electromagnetic (EM) noise in the form of conducted disturbances.A VFD is composed of an inverter, a motor, and a connecting power cable. The insulated-gate bipolar transistor (IGBT) technology and the pulse-width modulation (PWM) technique, used in the inverter, amplified the role of the power cable, which experiences the so-called “high-frequency” or “transmission line” effects, such as reflections, crosstalk, and distortion. Therefore, a complete EM assessment of a VFD requires an accurate and computationally efficient mathematical model of the cable, which can be studied as a multiconductor transmission line (MTL). Accordingly, we developed the “delay-rational Green’s-function-based” (DeRaG) model that should overcome the main limitations of the existing methods in the literature. In the DeRaG model, the impedance (or admittance) matrix is the sum of a rational series and a so-called hyperbolic part realized by hyperbolic functions. The rational series consists of poles and residues and can be truncated to a suitable size by a delay extraction technique. The hyperbolic part retains the primary information of the high-frequency behaviors, such as attenuation and propagation delays, of a line; thus, the DeRaG model is a wideband model. The DeRaG model is independent of the terminations and sources of the line and enables a delayed state-space representation; it can also account for EM interference. Nevertheless, an EM assessment of a complex system can be performed only using a calculator and proper software. Most of the advanced models for MTLs have been adapted for SPICE-like transient solvers. However, power electronics applications are commonly simulated by using software packages such as Simulink that are optimized for system-level simulations. We thus proposed the implementation of the DeRaG model both in SPICE and in Simulink to embrace a larger group of users and applications. The Simulink implementation was notably proven to be extremely simple and easy to describe. In addition, we focused on the hyperbolic part to qualitatively assess the behavior of an MTL. Our investigation resulted in an outstanding outcome; namely, we provided the distortionless condition for MTLs, whereas the distortionless condition was previously defined only for single-conductor transmission lines as the well-known Heaviside condition. In conclusion, the DeRaG model is a wideband model for the EM analysis of generic transmission lines that is suitable for system-level simulations required in power electronics applications and offers new insights into the physics of the system.
|
|
| 18. |
- Derhamy, Hasan
(författare)
-
Architectural Design Principles For Industrial Internet of Things
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- As society has progressed through periods of evolution and revolution, technology hasplayed a key role as an enabler. In the same manner that mechanical machines of the1800’s drove the industrial revolution, now digitalized machines are driving another one.With this recognition of a fourth industrial revolution, the Industry 4.0 initiative wasfounded. One of the drivers of Industry 4.0 is the Industrial Internet of Things (IIoT).The IIoT is a consequence of widely present computing ubiquity and interconnected-ness. Software has become a crucial tool of almost all industries from bakeries and arts to manufacturing facilities and banking. Programming is now a required competenceand used by a variety of professions. It is not only about algorithm development, it has become more about engineering and integrating existing designs and tools. This impacts the way software is architected and drives a large body of research in the area.Software solutions are becoming more distributed, not only over multiple processes, but over heterogeneous hardware and business domains. Computing platforms could bemobile or geographically separated over large distances, exposing the solutions to network disturbances, performance degradation and security vulnerabilities.Hence, IIoT introduces complexity on a scale previously unseen in the software in-dustry. Software architecture must accommodate these heterogeneous domains and com-petencies and handle the increasing levels of complexity.This thesis proposes an architectural style for designing IIoT software architectures.The popular Service Oriented Architecture (SOA) style is not sufficient to define a com-plete architecture for IIoT applications. SOA fundamental principles are defined as loose coupling, lookup and late binding. The proposed architecture style extends these SOA principles with autonomy, specialization, data at its source and first person perspective. It preserves the benefits of SOA that models functionalities as reusable services with standardized interfaces. Thus, the proposed style helps to capture the heterogeneity of IIoT (e.g. systems, capabilities, domains, competencies etc.), while handling challenges imposed by it. The style also captures resource constraints of IIoT platforms; distri-bution of application logic across IIoT; dependence between services within IIoT; and presentation of the solution in various stakeholder perspectives.The IIoT generates large amounts of data that is subsequently stored, analysed, archived and eventually fed back into the product life cycle. Centralization of data has well known challenges. This thesis proposes a method of information extraction based on the principle of data at its source. Such data preserves implicit context, reducing the burden of semantic data within the system. Desired information is expressed through dynamic (runtime) queries. Using the queries, a path is created to retrieve the requested data. It alleviates the need for data to be stored in intermediary nodes; data remains atthe source. Thus, IIoT applications extract information and present it to requesting sys-tems without redundant source related context. This helps with issues of data ownership, access control and stale data.Another IIoT challenge tackled in this work is decentralization of Manufacturing Execution System (MES). It is motivated by a need to mitigate the impact of vulnerable shared networks on the factory floor; and by business requirements to reduce dependence on local factory infrastructure. This thesis explores a solution where functions of MES are distributed to the workstations that enables them to operate autonomously. Such autonomous workstations utilize the proposed Intelligent Product, Workflow Managerand Workflow Executor systems. Thus, MES can be decentralized to edge nodes as envisioned by Industry 4.0.
|
|
| 19. |
- Eppanapelli, Lavan Kumar
(författare)
-
Experimental investigation of snow metamorphism at near-surface layers
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Snow metamorphism is a direct objective in many snow research areas, and its charac-terisation is a major challenge in areas including winter road maintenance, detection of icing on wind turbine blades, and snow quality mapping for skiing. A common effect of snow metamorphism is compaction, which can be investigated from the associated vari-ations in physical properties of snow. While the relation between snow metamorphism and physical properties of snow is fairly well-known, a method to quantify this relationis not extensively researched. This experimental based thesis focuses on the relationship between the physical properties of snow and its degree of metamorphism. The link isestablished and investigated by quantifying near-infrared (NIR) reflectance measure-ments and analysing the microtomographic data. Three experimental approaches are developed to record the NIR reflectance measurements and to understand the influence of compaction at near-surface layers of a snowpack. In addition, an X-ray microtomogra-phy (micro-CT) system is used to visualise the behaviour of snow microstructure during compaction. In this thesis, snow experienced compaction via aging, the melting-freezing process, uniaxial loading, settling and infiltration of liquid water.A numerical tool based on the well-established Discrete Ordinates Radiative Trans-fer (DISORT) method is used to solve the radiative transfer equation (RTE) for aplane-parallel and semi-infinite snowpack. The numerical solver takes the reflectance measurements as input and returns the coefficients of a first order Legendre phase function of an investigated snowpack at a given wavelength of light. The results from the solver show consistency and strong correlation between the Legendre coefficient sand the physical properties of snow. Furthermore, the physical properties of snow such as specific surface area (SSA) and liquid water content (LWC) were estimated via parameterisation where the reflectance data is used as input. The results suggest that the parameterisation of LWC can provide a qualitative estimate of the LWC in a snowpack, while the parameterisation of SSA provides a quantitative estimate of the snow SSA. As a next step, the influence of compaction on snow microstructure is investigated from three-dimensional (3D) images obtained using the micro-CT system. In this case, compaction is initiated by applying uniaxial load on a snow sample and the effect of compaction is analysed based on digital volume correlation (DVC) and porosity distribution. The micro-CT observations further emphasise that near-surface layers of a snowpack experience a higher degree of impact during compaction.In summary, this thesis presents experimental methods to quantify the link between snow compaction at near-surface layers, and the physical properties of snow. The mode observations show that the estimated Legendre coefficients can provide qualitative descriptions of snow grain distribution and surface texture. The parameterisation methods can provide the details about the LWC and the SSA of a snowpack. Further, the observations from the micro-CT study suggest that grains breakage and recrystallisation are the prevailing effects of snow compaction. All observations in this thesis are helpful in understanding the metamorphism in a snowpack for relevant research areas.
|
|
| 20. |
- Fresk, Emil
(författare)
-
The Core of Aerial Robotic Workers : Generalized Modeling, Estimation, and Control
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis we are going to explore what the operational core, both mathematically and algorithmically, of an Aerial Robotic Worker consists of, in order to estimate its egomotion and parameters, and adaptively control the aerial vehicle. Moreover, the aim of this thesis is to be a condensed reference for the corresponding areas of aerial robotics, in order to provide a stable and complete foundation on which one can continue research on. The areas that are covered in this Thesis are: 1) the fundamental modeling of the generalized aerial vehicle, where the kinematics, sensors and motor/thrust models will be presented together with simplified models for the motor characteristics, which will form the basis for all the future derivations, 2) how to model, calibrate and compensate for the errors existing in, and induced into, cheap accelerometers and gyroscopes, as these sensors constitute the aerial platform's core sensor suite as the inertial sensor. Successful methodologies and results are presented and evaluated to show that the cost of calibration can be dramatically reduced without loss of accuracy nor mechanical complexity. 3) How to perform inertial sensor driven egomotion and parameter estimation to lay the foundation for adaptive control strategies, where specific weight will be put on the successful development of a new profound sensory system which has the possibility to replace GPS in robotics applications, while also being able to perform indoors and in GPS denied environments, and which was the core of the localization module done in the AEROWORKS project, enabling the full, high accuracy localization around tall, GPS interfering infrastructure. And finally 4) how to utilize the estimation in low and high-level adaptive controllers, where specific results on how to successfully compensate for the movement of the center of gravity, together with the reduction of thrust over time due to declining battery voltage. Moreover we will explore the use case of Aerial Robotic Workers in real life applications and we will identify and comment on potential future directions of these aerial robotic systems and the impact theses can have in both research and society.
|
|
