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  • 127251.
    Öberg, Johnny
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Kumar, Anshul
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Hemani, Ahmed
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Kumar, Shashi
    Indian Institute of Technology.
    Specification and Synthesis of Exception Handling in Grammar-based Hardware Synthesis1998In: Journal of Electrical Engineering and Information Science, Korea, Vol. 3, no 6, p. 724-735Article in journal (Refereed)
  • 127252.
    Öberg, Johnny
    et al.
    KTH, Superseded Departments, Electronic Systems Design.
    Kumar, Anshul
    Jantsch, Axel
    KTH, Superseded Departments, Electronic Systems Design.
    An Object-Oriented Concept for Intelligent Library Functions1998In: Proceedings of the Eleventh International Conference on VLSI Design, 1998Conference paper (Refereed)
  • 127253.
    Öberg, Johnny
    et al.
    KTH, School of Information and Communication Technology (ICT), Electronic, Computer and Software Systems, ECS.
    Mellander, Roger
    ABB Research.
    Zahrai, Said
    ABB Research.
    The ABB NoC: A Deflective Routing 2x2 Mesh NoC targeted for Xilinx FPGAs2008In: Proceedings of FPGAWorld 2008, 2008Conference paper (Refereed)
  • 127254.
    Öberg, Johnny
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    O'Nils, M
    Jantsch, Axel
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Postula, A
    Hemani, Ahmed
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Grammar-based design of embedded systems2001In: Journal of systems architecture, ISSN 1383-7621, E-ISSN 1873-6165, Vol. 47, no 3-4, p. 225-240Article in journal (Refereed)
    Abstract [en]

    Grammars define syntax of languages and as such have not been commonly considered as methods for design, despite well-known applications in computer science. Only in recent years grammar-based design has become a promising research field and the first commercial tools have appeared on the market. This paper reviews the basic concepts of applying grammars to electronic design - in particular to the device driver synthesis of communication protocols for embedded software, to the design of custom-hardware, and to the virtual prototyping of DSP systems. The paper shows the power of these methods, presents the latest research results and discusses future developments in this field.

  • 127255.
    Öberg, Johnny
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Plosila, Juha
    Ellervee, Peeter
    Automatic synthesis of asynchronous circuits from synchronous RTL descriptions2005In: Norchip 2005, Proceedings, 2005, p. 200-205Conference paper (Refereed)
    Abstract [en]

    As the dimensions of ASICs shrink down to the nanometer regime, the variability of the process parameters will increase. This variability threatens to make it extremely difficult to distribute a synchronous clock. all over the chip. Another option would be to replace critical synchronous parts with asynchronous counterparts with the same functionality. The main problems are, first, there is no established tool-flow that makes it easy for a designer to design an asynchronous circuits, and, second, there are no established design automation tools, except a few experimental ones. In addition, most designers today are trained to design synchronous circuits and have to be retrained. In this paper we present a method that solves all three of these problems, i.e., it allows a designer to start in the synchronous domain, and then automatically transform the synchronous representation of the circuit into an asynchronous one.

  • 127256.
    Öberg, Johnny
    et al.
    KTH, School of Information and Communication Technology (ICT), Electronic Systems.
    Robino, Francesco
    KTH, School of Information and Communication Technology (ICT), Electronic Systems.
    A NoC Generator for the Sea-of-Cores Era2011In: Proceedings of FPGAWorld 2011, 2011Conference paper (Refereed)
  • 127257.
    Öberg, Johnny
    et al.
    KTH, School of Information and Communication Technology (ICT), Electronic Systems.
    Robino, Francesco
    KTH, School of Information and Communication Technology (ICT), Electronic Systems.
    A NoC system generator for the Sea-of-Cores era2011In: 8th FPGAworld Conference - Academic Proceedings 2011, 2011, p. 35-40Conference paper (Refereed)
    Abstract [en]

    Multi-core systems are getting bigger. The number of cores is doubling every 18 months, in corollary with the reformulated Moore's law. Soon, the number of cores that can be integrated together in a system will be so large, that it is appropriate to talk about a new SoC design paradigm, the Sea-of-Cores era. This development will not end, even when CMOS cannot be made any smaller. Instead, with the development of Through-Silicon Vias (TSVs), chips will be stacked in 3D, promising continuous scaling for a very long time ahead. As systems grow, programming and debugging of them will become harder. Methods for generating the systems from higher-level specifications will be necessary to manage design complexity. Also, there will be so many processors to be programmed, that the SW also will have to be automatically generated and distributed, much in the same way as a synthesis and place & route tool is doing today for HW. In this paper, we present a NoC generator that can generate an arbitrarily large Multi-core platform from an XML configuration file, targeted for single-chip FPGA platforms. The NoC generator also generates a device driver prototype together with a small test program that can be used as a template for creating larger programs.

  • 127258.
    Öberg, Kim
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Hed, Yvonne
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Joelsson Rahmn, Isabella
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Kelly, Jonathan
    Löwenhielm, Peter
    Malkoch, Michael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Dual-purpose PEG scaffolds for the preparation of soft and biofunctional hydrogels: the convergence between CuAAC and thiol-ene reactions2013In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 49, no 62, p. 6938-6940Article in journal (Refereed)
    Abstract [en]

    Orthogonally functionalized PEGs displaying alkenes and azides have been prepared and their dual-purpose scaffolding potential was exploited via click chemistry for controlled insertion of bio-relevant moieties as well as facile fabrication of soft, non-toxic and degradable hydrogels.

  • 127259.
    Öberg, Kim
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Ropponen, Jarmo
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Kelly, Jonathan
    Löwenhielm, Peter
    Berglin, Mattias
    Malkoch, Michael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Templating Gold Surfaces with Function: A Self-Assembled Dendritic Monolayer Methodology Based on Monodisperse Polyester Scaffolds2013In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, no 1, p. 456-465Article in journal (Refereed)
    Abstract [en]

    The antibiotic resistance developed among several pathogenic bacterial strains has spurred interest in understanding bacterial adhesion down to a molecular level. Consequently, analytical methods that rely on bioactive and multivalent sensor surfaces are sought to detect and suppress infections. To deliver functional sensor surfaces with an optimized degree of molecular packaging, we explore a library of compact and monodisperse dendritic scaffolds based on the nontoxic 2,2-bis(methylol)propionic acid (bis-MPA). A self-assembled dendritic monolayer (SADM) methodology to gold surfaces capitalizes on the design of aqueous soluble dendritic structures that bear sulfur-containing core functionalities. The nature of sulfur (either disulfide or thiol), the size of the dendritic framework (generation 1-3), the distance between the sulfur and the dendritic wedge (4 or 14 angstrom), and the type of functional end group (hydroxyl or mannose) were key structural elements that were identified to affect the packaging densities assembled on the surfaces. Both surface plasmon resonance (SPR) and resonance-enhanced surface impedance (RESI) experiments revealed rapid formation of homogenously covered SADMs on gold surfaces. The array of dendritic structures enabled the fabrication of functional gold surfaces displaying molecular covering densities of 0.33-2.2 molecules.nm(-2) and functional availability of 0.95-5.5 groups.nm(-2). The cell scavenging ability of these sensor surfaces for Escherichia coli MS7fim+ bacteria revealed 2.5 times enhanced recognition for G3-mannosylated surfaces when compared to G3-hydroxylated SADM surfaces. This promising methodology delivers functional gold sensor surfaces and represents a facile route for probing surface interactions between multivalently presented motifs and cells in a controlled surface setting.

  • 127260.
    Öberg, Kim
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Simonsson, Johanna
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    System design choices in smartautonomous networked irrigation systems2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Wireless Sensor Networks are often deployed in great numbers spanning large,

    sometimes hard to reach and hostile, areas with the aim of monitoring environmental

    conditions through the use of different sensors. Due to decreasing costs of ownership

    (e.g. non-proprietary protocols), recent advances in processor, radio, and memory

    technologies and the engineering of increasingly smaller sensing devices, the

    availability and area of application for wireless sensor networks have steadily been

    increasing.

    Sigma Technology Development Stockholm AB raised the question as to whether a

    wireless sensor network, running an open-source operating system and communicating

    over IPv6, could be used in the field of smart autonomous irrigation? The company also

    required a proof-of-concept system for demonstration purposes and to identify if the

    design choices made were suitable for an actual implementation.

    There are numerous of design decisions that have to be made when constructing an

    irrigation system: the back-end set-up, which irrigation algorithms to use, what hardware

    to choose and how to communicate? This thesis therefore focuses on the overall

    system design of a wireless sensor network in the field of irrigation and highlights the

    trade-offs being made and their pros and cons.

    Two improvements related to the existing technology and the proof-of-concept system

    are presented in this thesis. Firstly, the recommendation to use clustered self-healing

    routing despite claimed power consumption issues. Secondly, a new technique to

    minimize power consumption, by dynamically changing the sleep interval on the sensor

    nodes with the help of weather data. Furthermore, the proof-of-concept system is

    constructed and analysed to assess whether the system design choices made are valid

    for a real-life deployment.

  • 127261.
    Öberg, Lena-Maria
    et al.
    Mid Sweden University.
    Amcoff-Nyström, Christina
    Mid Sweden University.
    Hrastinski, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Learning.
    Mozelius, Peter
    Mid Sweden University.
    Interaction and group work in blended synchronous higher education: exploring effects on learning outcomes, satisfaction and retention2019In: Proceedings of the 18th European Conference on e-Learning, 2019Conference paper (Refereed)
  • 127262.
    Öberg, Lukas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology and Design.
    Lindahl, Mikael
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology and Design.
    Systemanalys av plattbroar: En jämförelse inom FE-modellering och balk-/platteori2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Abstract

    When Eurocodes was introduced, there was a requirement where the calculations had to take into consideration whether it's a slab or beam bridge. This means that calculations had to be made with softwares including plate theory.

    The object of this study is a slab bridge with endshields. The bridge is 66.95 meters long with a 14.38-meter-wide deck made of concrete. The deck is mounted on abutments with bearings and intermediate supports where the columns are fixed to the deck.

    The purpose of this study is to investigate if bridges defined as plates can be calculated using beam theory, as well as examining different modeling techniques in an attempt to evaluate how this will affect the results.

    A model using shell elements is established in BRIGADE/Plus and compared to a model in Strip Step 3 made out of beam elements. A base-model is also created in BRIGADE/Plus and is compared to the following modeling changes:

    • Couplings between supports and the plate, “point to surface” or “point to point”.
    • The bridge is modeled without wings to study the impact of the wings.
    • The bridge is modeled without columns to study the impact of the columns.

    When comparing the values obtained from the two different software’s regarding deadweight, the results were almost identical. This indicates that Strip Step 3 is a suitable tool for verifying models made in BRIGADE/Plus. When studying the results from load-combination 6.10.b (the combination used for dimensioning) small differences can be seen between the softwares. This concludes that it may be reasonable to use Strip Step 3 for this type of bridges. However, there are major differences between the software at the traffic load which should be considered.

    In order to simplify the modeling process ties between points (nodes) should be used. However, the results obtained over the supports must be ignored due to unrealistic values. When studying the impact of wings/columns it was confirmed that a difference of 10 % appeared. Modeling without wings/columns is not more time efficient either, with that in mind wings and columns should be used when modeling.

     

    Keywords: Plate theory, Beam theory, Strip Step 3, BRIGADE/Plus, FE-modeling

  • 127263.
    Öberg Löfstrand, Leonard
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology and Design.
    Lagerstam, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology and Design.
    Optimering av stämprivningstider: - En kvantitativ undersökning om stämprivningstider avbostadsbjälklag2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    When casting a residential floor, formwork and shore removal is an important element. There aresome doubts in the industry about when and how to remove the shores. There are instructionsavailable but they are often outdated and difficult to interpret. As a result, they are often notfollowed. Appliances such as measuring equipment and simulation software are available but areused sparingly. To avoid accidents and to ensure that the strength of the concrete is sufficientwithout appliances, excessive time margins are used. This will most likely result in unnecessarily longshoring times.During the course of the work, the subject will be studied in detail to create a clear picture of howthe many different factors of the casted floor influence each other. The purpose is to propose asuitable time to remove the shores. This is done in order to determine if there is improvementpotential, partly to improve the working environment, but also to review the instructions of theapproach.The methods used to reach the result are:• Study of the documents describing the procedure of shoring and reshoring• Calculate the compressive strength of the concrete with the device “BI Distant”• Simulate the compressive strength of the concrete in the program Hett 11.• Interviews by experts in the industry.The results show that the shores could theoretically be removed earlier compared to when they areusually removed in practice. One reason for this is that drying times are governing during theproduction. This means that increased concrete qualities and faster curing times than those thatwere planned, were used in construction, particularly at low temperatures. The conclusion is thatthere is an improvement potential in this area. Reshoring can be done only a few days after castingunder good conditions. The advantages of this are that the number of shores can be reduced. Thisleads to reduced rents, and the accessibility for the subsequent professionals and operations can beimproved.

  • 127264.
    Öberg, Magnus
    et al.
    KTH, Superseded Departments, Electronics.
    Kjebon, Olle
    KTH, Superseded Departments, Electronics.
    Lourdudoss, Sebastian
    KTH, Superseded Departments, Electronics.
    Nilsson, Stefan
    KTH, Superseded Departments, Electronics.
    Bäckbom, Lena
    KTH, Superseded Departments, Electronics.
    Streubel, Klaus
    KTH, Superseded Departments, Electronics.
    Wallin, Johan
    KTH, Superseded Departments, Electronics.
    Increased modulation bandwidth up to 20 GHz of a detuned-loaded DBR laser1994In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 6, no 2, p. 161-163Article in journal (Refereed)
    Abstract [en]

    A small signal amplitude modulation bandwidth of 20 GHz has been obtained with a three-section tunable DBR laser fabricated with semi-insulating current blocking layers grown by hydride VPE. The modulation bandwidth and laser linewidth are strongly dependent on the position of the lasing mode relative to the Bragg reflection peak.

  • 127265.
    Öberg, Martin
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    A Method to Obtain Straight Crack Fronts During Pre-Cracking of Compact Tension Specimens2013In: Journal of Testing and Evaluation, ISSN 0090-3973, E-ISSN 1945-7553, Vol. 41, no 5, p. 858-862Article in journal (Refereed)
    Abstract [en]

    A common problem during pre-cracking of compact tension (CT) specimens is skewed crack fronts. It is also one of the most common reasons for which tests according to, for instance, ASTM E1820-11: Standard Test Method for Measurement of Fracture Toughness, Annual Book of ASTM Standards, ASTM International, West Conshohocken, PA, 2012, do not give valid results. This problem is normally a result of the fact that specimens and fixtures are not perfectly aligned, even when the testing setup meets the requirements of ASTM standards. In the present investigation, aluminum bushings have been used to rearrange the loads transferred from the testing machine to the specimens. Geometrical errors were deliberately introduced to the testing setup so that the specimens were asymmetrically loaded. The introduced errors were, however, within the tolerances of ASTM standards. Steel specimens with two different notch types, Chevron and straight notches, were tested, both with and without aluminum bushings. The specimens were pre-fatigued and thereafter broken under monotonic loading. The specimen crack lengths were measured and validated according to ASTM E1820-11. The results related to pre-fatigued specimens with aluminum bushings were shown to be valid, whereas the results for specimens without bushings did not meet the ASTM standards requirements.

  • 127266.
    ÖBERG, MIKAELA
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Sustainability and Industrial Dynamics.
    A Study of the Implementation, Maintenance and Continual Improvement of an Information Security Management System2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The high adoption rate of cloud computing technology is changing the strategic, operational and functional aspects of businesses. Though, as cloud computing is seeing massive global investment, the vast concentration of resources and information argues for new sources of vulnerabilities and challenges for the cloud computing adopters. Hence, the cloud computing technology is argued to see its full potential once solid information security is established.

    There has been a palpable development of theories, guidelines and standards of how to implement, maintain and continually improve a security information management system. The outcome has resulted in recognized standards. However, the comprehensiveness and the complexity to implement, maintain and continually improve a security information management system remain. Therefore, this study aimed to investigate how cloud computing oriented firms succeed with the realization of an information security management system. This was done by identifying frameworks and processes used by cloud computing oriented organizations.

  • 127267.
    Öberg, Ola
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630).
    ABBORÖS fas 1: Odling av abborre i recirkulerande system i Östergötlands och Kalmars skärgårdar2008Report (Other academic)
    Abstract [en]

    The project ABBORÖS started in fall 2006. The aim was to study the possibility to farm perch in the archipelago in a way that meets both the requirements from the goals of environmental pro-tection for the Baltic Sea as well as the economical demands put upon a commercial business. The new questions addressed in this project are how perch can be farmed in Sweden and how to perform aquaculture in closed systems in the archipelago. New is also a systematic use of compe-tence of local fishermen to develop a sustainable aquaculture system. ABBORÖS is a joint ven-ture between the Royal Institute of Technology and eight fisherman families from the Swedish South East coast. The project is divided into two parts, the first with a budget of 1.3 million € started in October 2006 and finished in February 2008. The second part runs from June 2008 to June 2010 with a preliminary budget of 2.3 million €. During the project 10 people are having work opportunities and after the project the expectation is that 15-20 people will be engaged in this kind of aquaculture. The project will develop methods for how Perch can be cultivated in a recirculating systems in the archipelago, how much water that can be reused and how much of the nutrient loss that can be caught for alternative use compared to traditional net cage fish farm-ing. During the first year test systems with floating ponds constructed in fibre glass-armed PVC tarpaulin was built at different locations together with local fishermen, who were contracted as technicians. The fishermen joined together in the company Stannafisk AB with the ambitions to build eight ongrowing units with a yearly production capacity of 30 tons each and together con-struct a hatchery and a filleting plant. By farming perch the restaurants could be more evenly supplied during the year than by wild catch which gives mainly supply in springtime. This would create a possibility to make a living on a known product in a vanishing profession. By placing the ongrowing units in the vicinity of the families residential buildings, the energy and time used for transport can be kept to a minimum. The following years the systems will be operated at different conditions for optimization. The parameters addressed are fish density, cohort size, pond size, oxygen supply, sludge removal and ammonia removal. A final goal is to compare price and taste of cultured and wild caught Perch. Know-how of aquaculture techniques and juvenile production has been built with the help of a network of international experts during the first part of the pro-ject. The participants have increased their competence and their ability to cooperate. They have also installed a base structure for six farming units and built a capacity of fish production to 15 % of the proposed size at the end of the project. This implies that they are well prepared to make experiments in full scale during the second part of the project. After the first year approximately 200 000 perch are hold in the six units. The first fishes are expected to reach a market size of 400 grams three summers after hatching, which means in September 2008. For the Royal Institute of Technology and other interested research groups engagement in the project gives admission to a field laboratory with technicians for experiments and research on aquaculture and environmental technology.

  • 127268.
    Öberg, Ola
    KTH, Superseded Departments, Land and Water Resources Engineering.
    Assessment of sediment contaminants from ceramic production, a case study of Farstaviken2001Licentiate thesis, comprehensive summary (Other scientific)
  • 127269.
    Öberg, Philip
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management.
    Risk- and needs assessment of real estate property2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This studie highlights the challenges faced by the insurance broker in the process of assessing risk and needs for the real estate owner. It is also a guideline of how the broker could act to perform the assessment accordingly. The study aims to establish a foundation of how the process might be structured and those critical aspects of it. An area not yet researched.

    The studie is founded on theoretical as well as empirical data based upon evidence from literary and scientifical sources respectively interviews and real estate owner’s insurance documents.

    Generally speaking, the insurer and real estate owner relationship is one filled with asymmetric information. The asymmetric information leads to an increased risk of adverse selection and moral hazard for the insurer and a possibility of fault insurance for the insured. An insurance broker is often hired in order to independently perform a risk- and needs assessment to identify the risks and present the fitting insurance policy for the insured. The assessment mainly surrounds an analysis of the risks associated with the operations, real estate and property with purpose of estimating the claims frequency and consequence. As for the unexperienced broker this process could be challenging to perform at such veracity and quality which is required to be safe and sound both in front of the insured as well as the law.

  • 127270.
    Öberg, Sebastian
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematics (Div.).
    Homotopy Theory and TDA with a View Towards Category Theory2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis contains three papers. Paper A and Paper B deal with homotopy theory and Paper C deals with Topological Data Analysis. All three papers are written from a categorical point of view.

    In Paper A we construct categories of short hammocks and show that their weak homotopy type is that of mapping spaces. While doing this we tackle the problem of applying the nerve to large categories without the use of multiple universes. The main tool in showing the connection between hammocks and mapping spaces is the use of homotopy groupoids, homotopy groupoid actions and the homotopy fiber of their corresponding Borel constructions.

    In Paper B we investigate the notion of homotopy commutativity. We show that the fundamental category of a simplicial set is the localization of a subset of the face maps in the corresponding simplex category. This is used to define ∞-homotopy commutative diagrams as functors that send these face maps to weak equivalences. We show that if the simplicial set is the nerve of a small category then such functors are weakly equivalent to functors sending the face maps to isomorphisms. Lastly we show a connection between ∞-homotopy commutative diagrams and mapping spaces of model categories via hammock localization.

    In Paper C we study multidimensional persistence modules via tame functors. By defining noise systems in the category of tame functors we get a pseudo-metric topology on these functors. We show how this pseudo-metric can be used to identify persistent features of compact multidimensional persistence modules. To count such features we introduce the feature counting invariant and prove that assigning this invariant to compact tame functors is a 1-Lipschitz operation. For 1-dimensional persistence, we explain how, by choosing an appropriate noise system, the feature counting invariant identifies the same persistent features as the classical barcode construction.

  • 127271.
    Öberg, Sebastian
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematics (Div.).
    Modeling mapping spaces with short hammocks2014Licentiate thesis, monograph (Other academic)
    Abstract [en]

    We construct a category of short hammocks and show that it has the weak homotopy type of mapping spaces. In doing so we tackle the problem of applying the nerve to large categories without the use of multiple universes. We also explore what the mapping space is. The main tool in showing the connection between hammocks and mapping spaces will be the use of homotopy groupoids, homotopy groupoid actions and the homotopy fiber of their corresponding bar constructions.

  • 127272.
    Öberg, Sebastian
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematics (Div.).
    Rigidifying homotopy commutative diagramsManuscript (preprint) (Other academic)
    Abstract [en]

    In this paper we investigate functors indexed by simplex categories that send certain face maps to weak equivalences. We explain why such functors can be regarded as homotopy commutative diagrams. The key question we consider is related to rigidifications of such functors: under what circumstances is such a functor weakly equivalent to a functor that send these face maps to isomorphisms? We show that if the simplicial set is the nerve of a small category then such an homotopy commutative diagram can indeed be rigidified. We conjecture that this is also true whenever the simplicial set is a quasi-category. Lastly we show a connection between our homotopy commutative diagrams and mapping spaces of model categories via hammock localization.

  • 127273.
    Öberg, Viktor
    KTH, School of Information and Communication Technology (ICT).
    Adding DRAM and SRAM support for the NoC Generator2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    A NoC generator tool that generate an arbitrarily large Multi-core platform, targeted for single-chip FPGA platforms was developed in 2011 by Johnny Öberg and Francesco Robino in the department of electronic system, KTH, Sweden. In the current implementation of the platform, only on-chip memory is supported. However, the size of the data the system needs to handle is often too large to fit in those memories. Thus, external memory access to both SRAM and SDRAM on the FPGA board is needed. Adding external memories to an FPGA system takes a lot of time and hard studies in the Altera platform handbooks. Adding this feature to the NoC generator would save a lot of time for the platform developers

    In this thesis, an example design using external memories is analysed to obtain the necessary information needed to update the NoC generator to support SRAM and SDRAM.

  • 127274.
    Öberg, Viktor
    KTH, School of Chemical Science and Engineering (CHE).
    Macroalgae as a renewable resource: Extraction and Characterization of the Major Components in Saccharina Latissima2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A fractionation strategy was developed that made it possible to extract alginate, mannitol, laminarin and cellulose under various conditions from the brown algae Saccharina Latissima (previously known as Laminara Saccharina). The algae were harvested on the west coast of Sweden in the late summer of 2013. After extraction, the alginate and mannitol samples were identified and characterized using 1H nuclear magnetic resonance (1H NMR), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). The yield of alginate (in its sodium salt form) was estimated to be around 18,5 %, and the yield of mannitol was around 9 %. Mild hydrolysis and 1H NMR was performed on the alginate to estimate the ratio of mannuronic and guluronic acids, i.e. the M/G-ratio. The M/G-ratio was calculated to be around 1 for neutral batches and around 1,1 for batches extracted at low or high pH. Laminarin was identified and characterized by 1H NMR, FT-IR, TGA, size exclusion chromatography (SEC) and ion chromatography (IC). Approximately 12 % laminarin was extracted. Cellulose was identified and characterized by FT-IR and IC, and the yield was approximately 2,5 to 3,5 %.

    A three-level statistical factorial screening of the parameters temperature and pH was also performed using multiple linear regression (MLR) from 6 responses: the alginate, laminarin, cellulose, mannitol and total yield as well as the M/G-ratio. However, the yields of alginate, cellulose and mannitol were not possible to assess due to divergent data points. High temperature (75 °C) and pH 2 or 12 degrades alginate, thus decreasing the yield. The screening of laminarin yield showed that a decrease in pH had a significant positive effect. The screening of total yield indicated a negative effect when temperature was increased from 40 °C to 75 °C. At 3 or 40 °C, the M/G-ratio was significantly lower at neutral pH compared to those at pH 2 or 12. At 75 °C and pH 12, a degradation decreased the M/G-ratio to 0,83.

  • 127275.
    Öbom, Anton
    et al.
    KTH, School of Computer Science and Communication (CSC).
    Bratteby, Adrian
    KTH, School of Computer Science and Communication (CSC).
    Maskininlärning för att förutspå churn baserat på diskontinuerlig beteendedata2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report is about examining the fields of machine learning and digital marketing, using machine learning as a tool to predict churn in a new domain of companies that do not track their customers extensively, i.e where behaviour data is discontinuous. 

    To predict churn relatively simple out of the box models, such as support vector machines and random forests, are used to achieve an acceptable outcome. To be on par with the models used for churn prediction in subscription based services, this report concludes that more research has to be done using more effective evaluation metrics.

    Finally it is presented how these discoveries can be commercialized and the business related benefits of using churn prediction for the employer Sellpy.

  • 127276.
    Ödborn Jönsson, Linnéa
    KTH, School of Industrial Engineering and Management (ITM), Learning.
    Mapping re-growth following chemotherapy in high-risk neuroblastoma: The research process in laboratory work2019Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aim of the current study is to study characteristics of high-risk cancer cells within the childhood disease neuroblastoma (NB) by mapping regrowth after treatment with the chemotherapy doxorubicin (doxo). The cell-line SK-N-BE(2)-C (BE(2)-C) was used as a model. Results from a previous study by Hultman et al., (2018) have indicated that while a majority of BE(2)-C cells could be shown resilient to a 1 μM dose of doxorubicin (doxo), only a very small fractions had the capacity for immediate replication following a single or double treatment of doxo (“remaining replicating cells”; RRC). The current study aims to investigate if RRC are responsible for regrowth. Cultured BE(2)-C cells were exposed to doxo and labelled with the nucleoside analogues EdU (5-ethynyl-2’-deoxyuridine) and BrdU (5-bromo-2-deoxyuridine). The results from the current study indicated that the RRC subpopulation might not be responsible for regrowth since the nucleoside labelling was not shown to be present in the cells of the regrowing colonies. However, technical challenges, e.g. the settings of thresholds for EdU and BrdU detection, in combination with the dilution of DNA markers in replication, call for further studies using additional methods, e.g. isotope markers, in order to firmly conclude that other subpopulation(s) than the RRC population are responsible for regrowth.

    Apart from studying cell populations responsible for regrowth, a pilot study was performed including another combination of treatment using an ATM-inhibitor (KU-60019) together with the chemotherapy doxo. There were some measurement points missing, but the current results indicate that regrowth is postponed when the ATM-inhibitor is added in combination with single or double treatment of doxo.

    The research procedures and processes involved in this thesis, are similar to those included in the syllabi for the natural science subjects for the upper secondary school. This underlines the importance of studying inquiry and laboratory work. A literature review was performed, analysing current research on open-and closed ended laboratory work. Ten research articles were collected and characterized by natural science subject, type of laboratory style (open or closed) and student learning competences. Findings from the current study indicate that open-ended laboratory work promotes student interest in the subject. The learning competences problem-solving ability and procedure ability are most commonly studied in laboratory work based on the results from the current study.

  • 127277.
    Ödborn, Sofia
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    The Science of Deodorants2019Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Deodorants are cosmetic products that are consumed by people regularly and globally. In this thesis, the opportunities to develop a deodorant for the Swedish cosmetics brand IDUN Minerals AB is investigated. The deodorant market in Swedish pharmacies, deodorant formulation and deodorant packaging are studied. Furthermore, controversial ingredients, such as synthetic aluminum compounds, are explored.

    The scientific aspects of using synthetic aluminum compounds, which are used as antiperspirant in deodorants, are investigated. There is a general fear that they may increasethe risk of developing breast cancer. However, after a full review of exciting scientific evidence, it is clear that there is currently no study that can prove or disprove the suspicions. The use of aluminum-based antiperspirants therefore continues to be a controversial topic.

    The conclusion of this thesis is that there is a market opening for IDUN Minerals, especially since they aim for a synthetic aluminum-free, unperfumed and preservative-free deodorant. Furthermore, it is concluded that a Nordic Swan Ecolabel would make their product uniquein its product category. Lastly, it is determined that traditional plastic packaging is more accessible and possesses many favorable properties, but that bioplastics should be further researched.

  • 127278.
    Ödegaard Jacobsson, Sofia
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Deepening User Engagement on an Esports Platform Using Gamification: A Multi-Conceptual Study2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In recent years, the global interest in esports has grown exponentially, opening up for new technologies and products to be developed. One example is esports platforms which serve players with a common place to carry out their esports-related activities. This study utilizes current research about motivation and user engagement to develop three conceptual design proposals aiming to showcase how appropriate gamification components could be incorporated into an esports platform in order to deepen user engagement. These conceptual designs are evaluated by conducting a focus group, in which the participants had expert knowledge in the fields of esports, user experience, technology, and game design. Based on the results, conceptual design guidelines are established, and two final conceptual designs are proposed. With these two final designs, this study aims to contribute to and inspire future design work within the field of gamification and esports.

  • 127279.
    Ödling, Andreas
    KTH, School of Information and Communication Technology (ICT).
    Analysis and Optimisation of Communication Links for Signal Processing Applications2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    There are lots of communication links and standards currently being employed to build systems today. These methods are in many way standardised, but far from everyone of them are. The trick is to select the communication method that best suit your needs. Also there is currently a trend that things have to be cheaper and have shorter time to market. That leads to more Component Off The Shelf (COTS) systems being build using commodity components.

    As one part of this work, Gigabit Ethernet is evaluated as a COTS-solution to building large, high-end systems. The computers used are running Windows and the protocol used over Ethernet will be both TCP and UDP. In this work an attempt is also made to evaluate one of the non-standard protocols, the Link Port protocol for the TigerSHARC 20X-series, which is a narrow-bus, doubledata- rate protocol, able to provide multi-gigabit-per-second performance.

    The studies have shown lots of interesting things, e.g. that using a standard desktop computer and network card, the theoretical throughput of TCP over Gigabit Ethernet can almost be met, reaching well over 900 Mbps. UDP performance gives on the other hand birth to a series of new questions about how to achieve good performance in a Windows environment, since it is constantly outperformed by the TCP connections.

    For the Link Port assessment a custom built IP block is made that is able to support the protocol in full speed, using a Xilinx Virtex 6 FPGA. The IP block is verified through simulation against a model of the Link Port protocol. It is also shown that the transmitter of the IP block is able to send successfully to the receiver IP block. The IP block that is created, is evaluated against some competing multi-gigabit protocols to show it in comparison, and it is a rather small IP block, capable of handling all transactions on the bus as long as data is provided by its host.

  • 127280.
    Ödling, David
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    A metaheuristic for vehicle routing problems based on reinforcement learning2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The vehicle routing problem is an old and well-studied problem that arise in last mile logistics. The rapid increase of e-commerce, in particular with an increasing the demand for time scheduled home deliveries on the customer’s terms, is making the problem ever more relevant. By minimizing the cost and environmental impact, we have the setting for mathematical problem called the vehicle routing problem with time windows.

    Since the problem is NP-Hard, heuristic methods are often used. In practice, they work very well and typically offer a good tradeoff between speed and quality. However, since the heuristics are often tailormade to fit the needs of the underlying problem, no known algorithm dominates the other on all problems.

    One way to overcome the need for specialization is to produce heuristics that are adaptive. In this thesis, an offline learning method is proposed to generate an adaptive heuristic using local search heuristics and reinforcement learning.

    The reinforcement learning agents explored in this thesis are situated in both discrete and continuous state representations. Common to all state spaces are that they are inspired by human-crafted reference models where the last action and the result of that action define the state. Four different reinforcement learning models are evaluated in the various environments.

    By evaluating the models on a subset of the Solomon benchmark instances, we find that all models but one improve upon a random baseline. The average learner from each of the successful models was slightly worse than the human crafted baseline. However, the best among the generated models was an actor-critic based model which outperformed the best human baseline model.

    Due to the scalar objective function, the results are not directly comparable to the Solomon benchmark results with hierarchal objectives. None the less, the results are encouraging as a proof of principle with results in line with the human crafted baseline. The results indicate two clear paths for further work. First, applying the formulation to more complex environments with more actions and more powerful state spaces. Secondly, investigate models based on stochastic policies and recurrent neural networks to cope with the inherently partially observed environment.

  • 127281.
    Ödling, David
    et al.
    KTH, School of Engineering Sciences (SCI).
    Österlund, Arvid
    KTH, School of Engineering Sciences (SCI).
    Factorisation of Latent Variables in Word Space Models: Studying redistribution of weight on latent variables2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The ultimate goal of any DSM is a scalable and accurate representation of lexical semantics.

    Recent developments due to Bullinaria & Levy (2012) and Caron (2001) indicate that the accuracy of such models can be improved by redistribution of weight on the principal components. However, this method is poorly understood and barely replicated due to the computational expensive dimension reduction and the puzzling nature of the results. This thesis aims to explore the nature of these results. Beginning by reproducing the results in Bullinaria & Levy (2012) we move onto deepen the understanding of these results, quantitatively as well as qualitatively, using various forms of the BLESS test and juxtapose these with previous results. 

    The main result of this thesis is the verification of the 100% score on the TOEFL test and 91.5% on a paradigmatic version of the BLESS test. Our qualitative tests indicate that the redistribution of weight away from the first principal components is slightly different between word categories and hence the improvement in the TOEFL and BLESS results. While we do not find any significant relation between word frequencies and weight distribution, we find an empirical relation for the optimal weight distribution.

    Based on these results, we suggest a range of further studies to better understand these phenomena.

  • 127282.
    Ödlund, Kim
    KTH, School of Industrial Engineering and Management (ITM), Industrial Ecology (moved 20130630).
    Grönt bränsle i Västerås kommun2002Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This report deals with what the effect would be if the municipality of Västerås changed theirway of producing energy, to hopefully reduce the amount of pollution. An ex antecomparison of two alternatives/scenarios for the projected situation in year 2013 isperformed. The reason for this is that Målbild Västerås (a vision for the city of Västerås)deals with that year. The first alternative, called the zero alternative, shows how big theemissions would be if the power plant continued to produce energy by the burning of coaland oil. The other alternative, called the green fuel, describes how the big the emissionswould be if the power plant substitutes some of the coal with a locally grown energy cropcalled Salix. Emissions that have been treated in this report have been limited to covercarbon dioxide and nitrogen emissions.

    When Salix is produced it is impossible to harvest every year, but every 3-5 years dependingon the weather and location of the field. Because of that both the results from harvestingevery third year and harvesting every fifth year are shown in the report. To get a bettercomparison between the two alternatives the growing of regular crops has been included inthe zero alternative.

    You can clearly see that great environmental profits in NOx and carbon dioxide can begained by introducing the bio fuel. Carbon dioxide emissions are reduced by more than 100times in such a alteration. NOx emissions are between 4-6 times lower in the bio fuelalternative than in the zero alternative. In all calculations though there are an uncertaintywith varying size. With this uncertainty in mind you should be careful before to largeconclusions are drawn from the reduction of NOx emissions. I you look at the emissionswithin Västerås municipality the emissions are lowered in both alternatives, but still you cansee that introduction of the bio fuel clearly has the lowest emissions compared to the zeroalternative.

  • 127283.
    Ödmark, Victoria
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Building and Real Estate Economics.
    Samhällsfastigheter som investeringstrend: Hur kan priset motiveras utifrån det man vet om framtida kassaflöden?2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    There is currently a trend in the willingness to invest in public property, i.e. properties where different types of community services are provided. The advantage of this type of investment is that owners can sign long leases with tenants such as municipalities, counties and the state, providing secure cash flows and low vacancy risk. The investment market for public properties is relatively new to private operators as these properties have previously been owned almost exclusively by the municipality and county. Today, for various reasons, the municipalities and counties have decided to sell their properties and rent them back from specialized property owners.

    The study aims to identify the uncertainties/risks that are associated with investment and management of public properties, with a special focus on care properties in Sweden. An investment calculation and a sensitivity analysis were made through studies of three care property transactions in 2011 and interviews with the participating actors. The calculation and analysis have been the basis for the conclusions drawn.

    Investing in public real estate has proven to be a relatively stable and safe investment. The net operating income of the long leases that contribute to the investment could be considered as being paid back during the first contract period, assuming that no unexpected costs arise. The main risks that exist in these properties is salvage value risk due to severe alternative use for these tenant adjusted buildings, technical risk as the properties need to maintain standard and essential functions and at last political/legal risk where changes in demography, environmental laws, regulations and requirements affect public property development.

    Companies that invest in public real estate are usually focused on this type of investment, which through enhanced capabilities in the area contributes to a good and long-term relationship with tenants. Furthermore, the players involved have a rather homogeneous view of delegation of responsibility, contract structure and so on. Moreover, the demographic development in the country shows a high demand for public buildings in the future and especially in nursing and care homes.

  • 127284.
    Öfverholm, Ingmar
    KTH, Superseded Departments, Architecture and Townplanning.
    Livscykelkontnader i den tidiga projekteringsfasen1998Doctoral thesis, monograph (Other scientific)
  • 127285.
    Öfverholm, Rebecka
    KTH, School of Computer Science and Communication (CSC).
    Towards Functional Relation Learning with a Physical Robot.2012Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The objective of this project is to investigate the possibility of a robot learning a model for functional spatial relations through interaction with its environment. As a proof of concept I examine the two relations "location control" and "support" for pairs of objects, relations which are integral components of the spatial preposition "on". A simulated environment with a model of a robot arm is set up using the OpenRAVE framework. The robot manipulates objects in the scene to test for each relation, generating data used to train a logistic regression classifier with the Sparse Bayesian modelling approach. The results suggest that the functional relation learning with a physical robot is feasible, despite limitations caused by both the physics engine and by the difficulties of grasping.

  • 127286.
    Ögren, Niklas
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Selecting/realization of Virtual Private Networks with Multiprotocol Label Switching or Virtual Local Area Networks2002Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Many reports have been written about the techniques behind Virtual Private Networks (VPN) and Multi Protocol Label Switching (MPLS). They usually deal with the low level design of the software implementing a specific technique. The initial products are usually not mature enough to run in a large network or have to be adjusted in some way to fit.

    This report investigates the different ways of implementing strict layer 2 Virtual Private Networks in an existing nation-wide Gigabit Ethernet. The infrastructure in use, as well as the hardware, has to be used without major changes. Since 1998/1999, when MPLS first started in the laboratories, development has continued. Today it is possible to introduce MPLS or tunneled national virtual local area network into an existing network. This requires high speed, fault tolerant, and stable hardware and software.

    Going beyond the separation of traffic at layer 3 using Virtual Private Networks, i.e., IPSec, we can tunnel layer 2 traffic through a network. Although the first layer 3 VPN products are already in use, layer 2 VPNs still need to be evaluated and brought into regular use. There are currently two ways of tunneling VLANs in a core network: tunneled VLANs (or as Extreme Networks calls them, VMANs) and MPLS.

    This project showed that it is possible to start with a VLAN-only solution, and then upgrade to MPLS to solve scalability issues. The VMAN solution can not be used at Arrowhead, since there are too many disadvantages in the way Extreme Networks has implemented it. However, a mix of tunneling VMAN in a VLAN core is possible, and enables customer tagging of VLANs in a Layer 2 VPN. Furthermore, the testing of EAPS and per-VLAN Spanning Tree Protocol turned out well, and showed that EAPS should not be used when there is more than one loop.

  • 127287.
    Ögren, Patric
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Entrepreneurship and innovation.
    Högberg, Kristoffer
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Entrepreneurship and innovation.
    En ”marknadsundersökning” genom att iterera fram till ett värdeskapande koncept2013Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A business concept has been developed into a marketplace. The marketplace is a web and mobile application whose purpose is to create value out of resources' bookable time slots which today generally have low occupation rates at activity facilities within sports, culture and entertainment.

    The marketplace is intended to bring together a wide range of low occupation rate time slots for different activity types, with types of activities that friends typically do together an ordinary day. The idea is to build a strong brand for the marketplace with the clear message that "the marketplace provides a wide range of affordable offerings for sports and spare time activities, if you choose to adjust your schedule to fit the facilities' low occupation rate time slots". In addition, the marketplace should have functionality that makes it easier for end-users to find a time slot through the marketplace that fits everyone, by synchronizing the various options of activities and time slots preferences that people within a group of friends are interested in. The marketplace is supposed to be targeted to people with flexible schedules, especially self-employed, students and seniors. There is a good potential for a third party to run such a marketplace and specialize in creating value out of low occupation rate time slots. However, the business concept does not prevent the facilities themselves to make efforts which lead to increased occupation rates at time slots with low occupation rates. Furthermore, the facilities are rather supposed to use the marketplace as a complement to their existing booking systems. Based on the examined activity facilities, there is a good potential to increase a facility's turnover with approximately 330 000 SEK yearly.

    The business concept has been developed by doing a market research based on a technical product which initially was designed as a booking system with different product development opportunities and various potential customer segments to address. The market research was done iteratively by using the project management methodology Lean Startup combined with qualitative market research techniques from Innovation Games.

  • 127288.
    Ögren, Petter
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Formations and Obstacle Avoidance in Mobile Robot Control2003Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This thesis consists of four independent papers concerningthe control of mobile robots in the context of obstacleavoidance and formation keeping.

    The first paper describes a new theoreticallyv erifiableapproach to obstacle avoidance. It merges the ideas of twoprevious methods, with complementaryprop erties, byusing acombined control Lyapunov function (CLF) and model predictivecontrol (MPC) framework.

    The second paper investigates the problem of moving a fixedformation of vehicles through a partiallykno wn environmentwith obstacles. Using an input to state (ISS) formulation theconcept of configuration space obstacles is generalized toleader follower formations. This generalization then makes itpossible to convert the problem into a standard single vehicleobstacle avoidance problem, such as the one considered in thefirst paper. The properties of goal convergence and safetyth uscarries over to the formation obstacle avoidance case.

    In the third paper, coordination along trajectories of anonhomogenuos set of vehicles is considered. Byusing a controlLyapunov function approach, properties such as boundedformation error and finite completion time is shown.

    Finally, the fourth paper applies a generalized version ofthe control in the third paper to translate,rotate and expanda formation. It is furthermore shown how a partial decouplingof formation keeping and formation mission can be achieved. Theapproach is then applied to a scenario of underwater vehiclesclimbing gradients in search for specific thermal/biologicalregions of interest. The sensor data fusion problem fordifferent formation configurations is investigated and anoptimal formation geometryis proposed.

    Keywords:Mobile Robots, Robot Control, ObstacleAvoidance, Multirobot System, Formation Control, NavigationFunction, Lyapunov Function, Model Predictive Control, RecedingHorizon Control, Gradient Climbing, Gradient Estimation.

  • 127289.
    Ögren, Petter
    Swedish Defence Research Agency (FOI).
    Improved predictability of reactive robot control using Control Lyapunov Functions2008In: 2008 IEEE/RSJ INTERNATIONAL CONFERENCE ON ROBOTS AND INTELLIGENT SYSTEMS, VOLS 1-3, CONFERENCE PROCEEDINGS, 2008, p. 1274-1279Conference paper (Refereed)
    Abstract [en]

    Model based robot control approaches are often designed to allow the verification of certain system properties such as safety or goal convergence. However, designing such controllers is often very time consuming, and most of the time it is not possible to add additional control objectives without jeopardizing the previously proved system properties.

  • 127290.
    Ögren, Petter
    Swedish Defence Research Agency (FOI), Sweden.
    Increasing Modularity of UAV Control Systems using Computer Game Behavior Trees2012In: AIAA Guidance, Navigation, and Control Conference 2012, 2012Conference paper (Refereed)
    Abstract [en]

    In this paper, we argue that the modularity, reusability and complexity of Unmanned Aerial Vehicle (UAV) guidance and control systems might be improved by using a Behavior Tree (BT) architecture. BTs are a particular kind of Hybrid Dynamical Systems (HDS), where the state transitions of the HDS are implicitly encoded in a tree structure, instead of explicitly stated in transition maps. In the gaming industry, BTs have gained a lot of interest, and are now replacing HDS in the control architecture of many automated in-game opponents. Below, we explore the relationship between HDS and BTs. We show that any HDS can be written as a BT and that many common UAV control constructs are quite naturally formulated as BTs. Finally, we discuss the positive implications of making the above mentioned state transitions implicit in the BTs.

  • 127291.
    Ögren, Petter
    Swedish Defence Research Agency (FOI).
    Split and Join of Vehicle Formations doing Obstacle Avoidance2004In: 2004 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS 1- 5, PROCEEDINGS, 2004, p. 1951-1955Conference paper (Refereed)
    Abstract [en]

    In this paper, we study a scenario where a set of vehicles having different origins and/or destinations move in a common region. The goal is to have the vehicles join and leave formations in a completely decentralized manner. When a vehicle traveling along its own path finds itself moving close to another vehicle it automatically switches into follower mode. The vehicle stays in follower mode as long as the path of the other vehicle is beneficial to it. If, at some point, the leader is not moving towards the destination of the follower, the follower leaves the leader and head of on its own. We address this problem for a group of dynamic unicycle robots. Incorporating the split and join capability into a Receding Horizon Control approach to obstacle avoidance we are able to show safety as well as convergence of all vehicles to their destinations under general nonconvex obstacle assumptions. We illustrate the method with a simulation example

  • 127292.
    Ögren, Petter
    et al.
    Swedish Defence Research Agency (FOI).
    Backlund, Adam
    Swedish Defence Research Agency (FOI).
    Harryson, Tobias
    Swedish Air Force, Air Combat School .
    Kristensson, Lars
    Swedish Defence Research Agency (FOI).
    Stensson, Patrik
    Swedish Air Force, Air Combat School.
    Autonomous UCAV Strike Missions using Behavior Control Lyapunov Functions2006Conference paper (Refereed)
    Abstract [en]

    An autonomous Unmanned Combat Aerial Vehicle (UCAV) carrying out a surveillance or strike mission must be able to handle situations where the different mission objectives are in conflict and a tradeoff must be made, e.g. when the time of arrival is in conflict with the prescribed safety distance to an enemy surface to air missile (SAM) site. This paper describes a framework called Behavior Control Lyapunov Functions (BCLF), to handle such tradeoffs. The framework combines the natural idea of different control behaviors for different mission objectives, suggested in the Behavior Based robotics approach, with the mathematical transparency of Control Lyapunov Functions (CLF) from control theory. First, each behavior is represented by a scalar function with certain CLF-like properties, describing to what extent that mission objective is satisfied. The operator then edits a priority table reflecting the order of importance between different objectives, as well as different levels of satisfaction. Based on the table and the current levels of satisfaction the algorithm decides which objectives should be focused on right now, and which should currently be ignored. Finally, the current high priority objectives are transformed into recommended subsets of the available control choices, and passed to the controller. The paper is concluded with simulation examples illustrating the approach.

  • 127293.
    Ögren, Petter
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Robotics, perception and learning, RPL.
    Colledanchise, Michele
    KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP.
    Behavior Trees in Robotics and AI: An Introduction2018 (ed. First)Book (Refereed)
    Abstract [en]

    Behavior Trees (BTs) provide a way to structure the behavior of an artificial agent such as a robot or a non-player character in a computer game.  Traditional design methods, such as finite state machines, are known to produce brittle behaviors when complexity increases, making it very hard to add features without breaking existing functionality.  BTs were created to address this very problem, and enables the creation of systems that are both modular and reactive. Behavior Trees in Robotics and AI: An Introduction provides a broad introduction as well as an in-depth exploration of the topic, and is the first comprehensive book on the use of BTs.

  • 127294.
    Ögren, Petter
    et al.
    KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP.
    Egerstedt, M
    Hu, X
    A Control Lyapunov Function Approach to Multi-Agent Coordination2001Conference paper (Refereed)
    Abstract [en]

    In this paper, the multiagent coordination problem is studied. This problem is addressed for a class of robots for which control Lyapunov functions can be found. The main result is a suite of theorems about formation maintenance, task completion time, and formation velocity. It is also shown how to moderate the requirement that, for each individual robot, there exists a control Lyapunov function. An example is provided that illustrates the soundness of the method

  • 127295.
    Ögren, Petter
    et al.
    KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP.
    Egerstedt, M
    Hu, X
    A control Lyapunov function approach to multi-agent coordination2002In: IEEE transactions on robotics and automation, ISSN 1042-296X, Vol. 18, no 5, p. 847-851Article in journal (Refereed)
    Abstract [en]

    In this paper, the multiagent coordination problem is studied. This problem is addressed for a class of robots for which control Lyapunov functions can be found. The main result is a suite of theorems about formation maintenance, task completion time, and formation velocity. It is also shown how to moderate the requirement that, for each individual robot, there exists a control Lyapunov function. An example is provided that illustrates the soundness of the method

  • 127296.
    Ögren, Petter
    et al.
    KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP.
    Egerstedt, M
    Hu, X
    Reactive mobile manipulation using dynamic trajectory tracking2000Conference paper (Refereed)
    Abstract [en]

    A solution to the trajectory tracking problem for mobile manipulators is proposed, that allows for the base to be influenced by a reactive, obstacle avoidance behavior. Given a trajectory for the gripper to follow, a tracking algorithm for the manipulator is designed, and at the same time the base motions are generated in such a way that the base is coordinated with the gripper. Furthermore, it is shown that the method allows arbitrary upper and lower bounds on the gripper-base distance to be set and this can be achieved without introducing deadlocks into the system. The solution also ensures that the control effort, spent on slow base motions, is kept small

  • 127297.
    Ögren, Petter
    et al.
    KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP.
    Fiorelli, E
    Leonard, N.E.
    Formations with a Mission: Stable Coordination of Vehicle Group Maneuvers2002Conference paper (Refereed)
    Abstract [en]

    In this paper we present a stable coordination strategy for vehicle formation missions that involve group translation, rotation, expansion and contraction. The underlying coordination framework uses artificial potentials and virtual leaders. Symmetry in the framework is exploited to partially decouple the mission control problem into a formation management subproblem and a maneuver management subproblem. The designed dynamics of the virtual leaders play a key role in both subproblems: the direction of motion of the virtual leaders is designed to satisfy the mission while the speed of the virtual leaders is designed to ensure stability and convergence properties of the formation. The latter is guaranteed by regulating the virtual leader speed according to a feedback measurement of an appropriate formation error function. The coordination strategy is illustrated in the context of adaptive gradient climbing missions.

  • 127298.
    Ögren, Petter
    et al.
    Swedish Defense Research Agency.
    Fiorelli, Eddie
    Princeton University.
    Leonard, Naomi
    Princeton University.
    Cooperative Control of Mobile Sensor Networks: Adaptive Gradient Climbing in a Distributed Environment2004In: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 49, no 8, p. 1292-1302Article in journal (Refereed)
  • 127299.
    Ögren, Petter
    et al.
    KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP.
    Leonard, N
    Obstacle Avoidance in Formation,2003Conference paper (Refereed)
    Abstract [en]

    In this paper, we present an approach to obstacle avoidance for a group of unmanned vehicles moving in formation. The goal of the group is to move through a partially unknown environment with obstacles and reach a destination while maintaining the formation. We address this problem for a class of dynamic unicycle robots. Using Input-to-State Stability we combine a general class of formation-keeping control schemes with a new dynamic window approach to obstacle avoidance in order to guarantee safety and stability of the formation as well as convergence to the goal position. An important part of the proposed approach can be seen as a formation extension of the configuration space obstacle concept. We illustrate the method with a challenging example.

  • 127300.
    Ögren, Petter
    et al.
    Mech. & Aerosp. Eng. Dept., Princeton Univ., NJ, USA.
    Leonard, Naomi Ehrich
    Mech. & Aerosp. Eng. Dept., Princeton Univ., NJ, USA.
    A Convergent Dynamic Window Approach to Obstacle Avoidance2005In: IEEE Transactions on robotics, ISSN 1552-3098, E-ISSN 1941-0468, Vol. 21, no 2, p. 188-195Article in journal (Refereed)
    Abstract [en]

    The dynamic window approach (DWA) is a well-known navigation scheme developed by Fox et al. and extended by Brock and Khatib. It is safe by construction, and has been shown to perform very efficiently in experimental setups. However, one can construct examples where the proposed scheme fails to attain the goal configuration. What has been lacking is a theoretical treatment of the algorithm's convergence properties. Here we present such a treatment by merging the ideas of the DWA with the convergent, but less performance-oriented, scheme suggested by Rimon and Koditschek. Viewing the DWA as a model predictive control (MPC) method and using the control Lyapunov function (CLF) framework of Rimon and Koditschek, we draw inspiration from an MPC/CLF framework put forth by Primbs to propose a version of the DWA that is tractable and convergent.

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