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  • 122051.
    Ótão Pereira, Pedro Miguel
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. KTH Royal Inst Technol, Sch Elect Engn, SE-10044 Stockholm, Sweden..
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre. KTH Royal Inst Technol, Sch Elect Engn, SE-10044 Stockholm, Sweden..
    Lyapunov-based Generic Controller Design for Thrust-Propelled Underactuated Systems2016In: 2016 EUROPEAN CONTROL CONFERENCE (ECC), IEEE , 2016, p. 594-599Conference paper (Refereed)
    Abstract [en]

    We present a controller for an underactuated system which is driven by a one dimensional linear acceleration/thrust along a direction vector, by a time-varying gravity, and by the angular acceleration of the direction vector. We propose state and time-dependent control laws for the linear and angular accelerations that guarantee that the position of the system is steered to the origin. The proposed control law depends on (i) a bounded control law for a double integrator system; and (ii) on a Lyapunov function that guarantees asymptotic stability of the origin for the double integrator system when controlled with the previous bounded control law. As such, the control law forms a family of control laws depending on (i) and (ii). The complete state space of the system, under the proposed control laws, has two equilibria, and by proper control design, a trajectory of the system is guaranteed to converge to only one of those. The overall design provides a common framework for controlling different systems, such as quadrotors and slung load transportation systems.

  • 122052.
    Ótão Pereira, Pedro Miguel
    et al.
    KTH, School of Electrical Engineering (EES).
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering (EES).
    Nonlinear Pose Tracking Controller for Bar Tethered to Two Aerial Vehicles with Bounded Linear and Angular Accelerations2017In: 2017 IEEE 56th Annual Conference on Decision and Control, CDC 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 4260-4265Conference paper (Refereed)
    Abstract [en]

    We consider a system composed of a bar tethered to two aerial vehicles, and develop a controller for pose tracking of the bar, i.e., a controller for position and attitude tracking. Our first control step is to provide an input and a state transformations which convert the system vector field into one that highlights the cascaded structure of the problem. We then design a controller for the transformed system by exploring that cascaded structure. There are three main contributions: i) we provide bounds on the linear and angular acceleration of the bar that guarantee well-posedness of the controller, and such bounds can be used when selecting the gains and saturations of bounded controllers for both three dimensional and unit vector double integrators; ii) the proposed control law includes a degree of freedom which can be used to regulate the relative position between the aerial vehicles; and iii) the proposed control law for the throttle guarantees that the cascaded structure of the problem is preserved. Simulations are presented which validate the proposed algorithm.

  • 122053.
    Ótão Pereira, Pedro Miguel
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Computer Science and Communication (CSC), Centres, Centre for Autonomous Systems, CAS.
    Stability of load lifting by a quadrotor under attitude control delay2017In: Proceedings - IEEE International Conference on Robotics and Automation, Institute of Electrical and Electronics Engineers Inc. , 2017, p. 3287-3292Conference paper (Refereed)
    Abstract [en]

    We propose a control law for stabilization of a quadrotor-load system, and provide conditions on the control law's gains that guarantee exponential stability of the equilibrium. The system is composed of a load and an unmanned aerial vehicle (UAV) attached to each other by a cable of fixed length, which behaves as a rigid link under tensile forces; and the control input is composed of a three dimensional force requested to the UAV, which the UAV provides with or without delay. Given the proposed control law, we analyze the stability of the equilibrium in two separate parts. In the first, the system is modeled assuming that the UAV provides the requested control input without delay, and we verify that the equilibrium is exponentially stable. In the second part, the UAV is modeled as possessing an attitude inner loop, and we provide a lower bound on the attitude gain for which exponential stability of the equilibrium is preserved. An integral action term is also included in the control law, which compensates for battery drainage or model mismatches, such as an unknown load mass. We present experiments for different scenarios that demonstrate and validate the robustness of the proposed control law.

  • 122054.
    Ótão Pereira, Pedro Miguel
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Dimarogonas, Dino V.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Family of controllers for attitude synchronization in S22016In: Proceedings of the IEEE Conference on Decision and Control, IEEE conference proceedings, 2016, p. 6761-6766Conference paper (Refereed)
    Abstract [en]

    In this paper we study a family of controllers that guarantees attitude synchronization for a network of elements in the unit sphere domain, i.e., S2. We propose distributed continuous controllers for elements whose dynamics are controllable (i.e., control with torque as command), and which can be implemented by each individual agent without the need of a common global orientation frame among the network, i.e., it requires only local information that can be measured by each individual agent from its own orientation frame. The controllers are specified according to arbitrary distance functions in S2, and we provide conditions on those distance functions that guarantee that i) a synchronized network of agents is locally asymptotically stable for an arbitrary connected network topology; ii) a synchronized network can be achieved for almost all initial conditions in a tree graph network. We also study the equilibria configurations that come with specific types of network graphs. The proposed strategies can be used in attitude synchronization of swarms of fully actuated rigid bodies, such as satellites.

  • 122055.
    Ótão Pereira, Pedro Miguel
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Herzog, M.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Dimarogonas, Dimos
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Slung load transportation with a single aerial vehicle and disturbance removal2016In: 24th Mediterranean Conference on Control and Automation, MED 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, p. 671-676Conference paper (Refereed)
    Abstract [en]

    We present a trajectory tracking controller for a quadrotor-load system, composed of a single load and a single unmanned aerial vehicle connected by a cable or rope. The load is modeled as a point mass while the aerial vehicle is assumed to be fully actuated, with thrust and attitude of the quadrotor as inputs to the system quadrotor-load. We assume there is a constant input disturbance at the thrust input, and a disturbance estimator is presented that guarantees that asymptotic tracking is guaranteed in the presence of such a disturbance. The load and the aerial vehicle are connected by a cable of fixed length that behaves as a rigid link under tensile forces, and as a non-rigid link when under compressive forces. The proposed controller guarantees that the cable is always under tensile forces, provided that the position trajectory to be tracked satisfies some mild conditions. The system quadrotor-load can be transformed into a form that resembles that of systems describing underactuated aerial vehicles, and for which a variety of control strategies have been proposed. In particular, we propose a controller based on a backstepping procedure in conjunction with a bounded double integrator controller. We present simulations validating the proposed control algorithm, and some preliminary experimental results are also presented.

  • 122056.
    Ótão Pereira, Pedro Miguel
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. KTH Royal Inst Technol, Sch Elect Engn, SE-10044 Stockholm, Sweden..
    Roque, Pedro
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. KTH Royal Inst Technol, Sch Elect Engn, SE-10044 Stockholm, Sweden..
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. KTH Royal Inst Technol, Sch Elect Engn, SE-10044 Stockholm, Sweden..
    Asymmetric Collaborative Bar Stabilization Tethered to Two Heterogeneous Aerial Vehicles2018In: 2018 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA), IEEE Computer Society, 2018, p. 5247-5253Conference paper (Refereed)
    Abstract [en]

    We consider a system composed of a bar tethered to two unmanned aerial vehicles (UAVs), where the cables behave as rigid links under tensile forces, and with the control objective of stabilizing the bar's pose around a desired pose. Each UAV is equipped with a PID control law, and we verify that the bar's motion is decomposable into three decoupled motions, namely a longitudinal, a lateral and a vertical. We then provide relations between the UAVs' gains, which, if satisfied, allows us to decompose each of those motions into two cascaded motions; the latter relations between the UAVs' gains are found so as to counteract the system asymmetries, such as the different cable lengths and the different UAVs' weights. Finally, we provide conditions, based on the system's physical parameters, that describe good and bad types of asymmetries. We present experiments that demonstrate the stabilization of the bar's pose.

  • 122057.
    Ótão Pereira, Pedro Miguel
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    V. Dimarogonas, Dimos
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Technical Report:: Attitude Synchronization in S2Manuscript (preprint) (Other academic)
    Abstract [en]

    In this paper we study a family of controllers that guarantees attitude synchronization for a network of elements in the unit sphere domain, i.e. S<sup>2</sup>. We propose distributed continuous controllers for elements whose dynamics are controllable (i.e. control with torque as command), and which can be implemented by each individual agent without the need of a common global orientation frame among the network, i.e. it requires only local information that can be measured by each individual agent from its own orientation frame. The controllers are specified according to arbitrary distance functions in S<sup>2</sup>, and we provide conditions on those distance functions that guarantee that i) a synchronized network of agents is locally asymptotically stable for an arbitrary network topology; ii) a synchronized network can be achieved for almost all initial conditions in a tree graph network. We also study the equilibria configurations that come with specific types of network graphs. The proposed strategies can be used in attitude synchronization of swarms of fully actuated rigid bodies, such as satellites.

  • 122058.
    Ótão Pereira, Pedro Miguel
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Zanella, Riccardo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Decoupled Design of Controllers for Aerial Manipulation with Quadrotors2016In: 2016 IEEE/RSJ INTERNATIONAL CONFERENCE ON INTELLIGENT ROBOTS AND SYSTEMS (IROS 2016), 2016, p. 4849-4855Conference paper (Refereed)
    Abstract [en]

    In this paper, we model an aerial vehicle, specifically a quadrotor, and a load attached to each other by a rigid link. We assume a torque input at the joint between the aerial vehicle and the rigid link is available. After modeling, we decouple the system dynamics in two separate subsystems, one concerning the position of the center of mass, which we control independently from the chosen torque input; and a second subsystem, concerning the attitude of the rigid link, which we control by appropriately designing a torque control law. Differential flatness is used to show that controlling these two separate systems is equivalent to controlling the complete system. We design control laws for the quadrotor thrust, the quadrotor angular velocity and the torque input, and provide convergence proofs that guarantee that the quadrotor follows asymptotically a desired position trajectory while the manipulator follows a desired orientation. Simulation and experimental works are presented which validate the proposed algorithms.

  • 122059.
    Öberg, Christian
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. 8912104273.
    Thermal Cycling, Creep- and Tensile Testing of Cast Exhaust Materials at Elevated Temperatures2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    An exhaust manifold of a truck engine is subjected to tough conditions. As the truck is started, operated and shut down, it becomes subjected to thermal cycling up to around 800°C. At such high temperatures, corrosion, fatigue and creep are active degradation mechanisms. As can be imagined, the interplay between the three complicates materials selection. It is desired to have a versatile grade of high durability which is not too expensive. At the moment, a ferritic, ductile cast iron designated SiMo51 is used for the application. However, due to the rough conditions, it is considered to be on the verge of its operational limit. As a consequence, there is an ongoing search for candidate materials. In this study, the ductile cast irons SiMo51, SiMo1000, D5S and the cast steel HK30 have been included.

    In the past, there have been several studies describing corrosion and fatigue of the cast materials used for exhaust manifolds. However, on the subject of creep of cast materials, little is known. The present study aims to reveal creep tendencies of cast materials and to do it in several ways. More precisely, three creep-testing methods were employed: the conventional constant-load creep-test, the “Sequential tensile test (STT)” and “Stress relaxations with thermal cycling (SRTC)”. The first one is the traditional one. It is tedious, usually lasting months or years. The second one is a tensile test in which the strain rate is changed in sequences as specimen deformation proceeds. Here, the idea is that a slow tensile test is not different from a conventional creep test. In the third one, stress relaxations are provoked as a specimen is thermally cycled in a locked state. Since stress relaxations are a consequence of creep deformation, the relaxation data gathered from isothermal holds can be directly compared to results from the isothermal constant-load creep-test and STT. When thermally cycled in a locked state, the materials display a loop character in σ, ε and T which provides extensive information about the mechanical properties over the selected temperature interval.

    In a logarithmic Norton plot, the creep strain rate is plotted as a function of stress. By plotting STT-data in such Norton plots, it was shown that the creep behaviour of the included materials is well represented by Norton’s law. Furthermore, it was found that the creep strain rates and stress relaxations, measured during isothermal holds in SRTC, in several cases show perfect coincidence with tensile test data obtained through STT. At 700°C, data from all three tests were inserted in the same Norton plot. At higher stress levels, the SRTC-curve follows the STT-curve and at lower stresses, when the creep regime is entered, it bends down and unites with data obtained by the constant-load creep tests. Additionally, it was seen that a relatively high degree of pre-deformation can give a critical stress below which creep deformation stops completely.

  • 122060.
    Öberg, Christian
    et al.
    KTH, School of Industrial Engineering and Management (ITM). 8912104273.
    Tjernberg, Anders
    Scania CV.
    Rablbauer, Ralf
    Volkswagen.
    Jonsson, Stefan
    KTH, School of Industrial Engineering and Management (ITM).
    Monotonic and Cyclic Creep of Exhaust Manifold Materials and their effects on Predicted Thermo-mechanical Fatigue LifeManuscript (preprint) (Other academic)
    Abstract [en]

    Creep properties of SiMo51, SiMo1000, Ni-resist D5S and HK30, materials used for exhaust manifolds in heavy-duty diesel-engines, are examined by three methods; sequential tensile tests at high temperature, varying the strain rate; relaxation of stresses and strains during isothermal holds of thermal cycling with fixed grips; and traditional creep testing. The results for tensile tests and relaxations coincide while the creep tests show values, one order of magnitude lower.

    The creep can be modelled by Norton’s law and the cyclic influence, including strain reversals, is low. Simulations with/without taking creep into account show that predicted fatigue life for an exhaust manifold, subjected to engine tests with cycling between hot and cold gases, generally increase, with a few exceptions in some points, and that critical spots of low fatigue life are removed because of reduced mean stresses.

  • 122061.
    Öberg, Christian
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Zhu, B. H.
    Jonsson, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Plastic deformation and creep of two ductile cast irons, simo51 and simo1000, during thermal cycling with large strains2018In: 11th International Symposium on the Science and Processing of Cast Iron, SPCI-XI 2017, Trans Tech Publications, 2018, Vol. 925, p. 361-368Conference paper (Refereed)
    Abstract [en]

    Cyclic deformations of two ferritic, ductile cast irons, SiMo51 and SiMo1000, were studied in air and Ar using a new method, SRTC (stress relaxation with thermal cycling). Locked specimens were thermally cycled up to 800 °C with isothermal holds, varying temperature interval, heating/cooling rates and hold times. A description of the mechanical response to thermal cycling of a locked specimen is given.

  • 122062.
    Öberg, Christian
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. 8912104273.
    Zhu, Baohua
    Scania CV.
    Jonsson, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Plastic deformation and creep of two ductile cast irons, SiMo51 and SiMo1000, during thermal cycling with large strainsIn: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752Article in journal (Refereed)
    Abstract [en]

    Cyclic deformations of two ferritic, ductile cast irons, SiMo51 and SiMo1000, were studied in air and Ar using a new method, SRTC (stress relaxation with thermal cycling). Locked specimens were thermally cycled up to 800 °C with isothermal holds, varying temperature interval, heating/cooling rates and hold times. A description of the mechanical response to thermal cycling of a locked specimen is given.

  • 122063.
    Öberg, Emma
    KTH, School of Chemical Science and Engineering (CHE).
    Investigation of mineral oils as a compatibilizer between metallocene polyolefins and rosin resins in hot melt adhesives2016Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Limning är en gammal fogningsteknik som har många olika användningsområden. Marknaden för limmer växer, smältlim förväntas ha stor tillväxt även med hårdare miljölagstiftning då appliceringen av limmet sker utan lösningsmedel.

    För att ta fram och tillverka lim används idag polymerer i stor utsträckning. Metallocen polyolefin (mPO) är en typ av polymer som används i limmer på grund av dess utmärkta prestanda som uppnås genom en smal molekylviktsdistribution (MWD). Detta gör det lätt att tillverka limmer med önskade egenskaper. Den här typen av polymerer tenderar dock att vara opolära vilket gör att de är inkompatibla med tallhartser, som ger klibbighet till limmet, eftersom tallhartserna har en högre poläritet.

    Mineraloljor används i limmer som mjukgörare, men används också i vissa fall för att öka kompabiliteten i olika typer av limmer. Därför har det undersökts om de kan användas i limmer med mPO och tallharts för att öka kompabiliteten.

    ”Cloud point”-tester och reologistudier har utförts för att undersöka om kompabiliteten påverkades av tillsatt mineral olja. Peel tester har också utförts för att mäta limegenskaperna för formuleringarna av smältlim.

    Resultaten visar att även om formuleringarna av smältlim har relativt låg peel styrka, så ökade kompabiliteten signifikant mellan mPO och tallhartser vid användning av mineraloljor.

  • 122064.
    Öberg, Fredrik
    et al.
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH, Music Acoustics.
    Askenfelt, Anders
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH, Music Acoustics.
    Acoustical and perceptual influence of duplex stringing in grand pianos2012In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 131, no 1, p. 856-871Article in journal (Refereed)
    Abstract [en]

    This study investigates the acoustical and perceptual influence of the string parts outside the speaking length in grand pianos (front and rear duplex strings). Acoustical measurements on a grand piano in concert condition were conducted, measuring the fundamental frequencies of all main and duplex strings in the four octaves D4-C8. Considerable deviations from the nominal harmonic relations between the rear duplex and main string frequencies, as described by the manufacturer in a patent, were observed. Generally the rear duplex strings were tuned higher than the nominal harmonic relations with average and median deviations approaching _50 cent. Single keys reached +190 and -100 cent. The spread in deviation from harmonic relations within trichords was also substantial with average and median values around 25 cent, occasionally reaching 60 cent. Contributions from both front and rear duplex strings were observed in the bridge motion and sound. The audibility of the duplex strings was studied in an ABX listening test. Complete dampening of the front duplex was clearly perceptible both for an experiment group consisting of musicians and a control group with naive subjects. The contribution from the rear duplex could also be perceived, but less pronounced.

  • 122065.
    Öberg, Gustav
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology and Design.
    Erfarenhetsåterföring: En väg till bättre anbud2013Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis has been done in collaboration with JM Entreprenad, a wholly owned subsidiary of JM AB. JM AB is one of Sweden's largest construction companies. The task has been to assist JM Entreprenad Region Hus with an investigation concerning how the experience feedback between Calculus Department and Production is working and to make suggestions for improvements.

    Experience feedback comprises collecting and reusing the experience and knowledge which comes from different parts of the organization and to use this knowledge as a basis for improvement of future work.

    There is currently no established procedures for how this experience feedback shall be carried out which is a shortcoming in the organization. To change this, the company should strive to become a learning organization and establish clear procedures for how this work shall be organized.

  • 122066.
    Öberg Hed, Kim
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Advanced polymeric scaffolds for functional materials in biomedical applications2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Advancements in the biomedical field are driven by the design of novel materials with controlled physical and bio-interactive properties. To develop such materials, researchers rely on the use of highly efficient reactions for the assembly of advanced polymeric scaffolds that meet the demands of a functional biomaterial. In this thesis two main strategies for such materials have been explored; these include the use of off-stoichiometric thiol-ene networks and dendritic polymer scaffolds. In the first case, the highly efficient UV-induced thiol-ene coupling (TEC) reaction was used to create crosslinked polymeric networks with a predetermined and tunable excess of thiol or ene functionality. These materials rely on the use of readily available commercial monomers. By adopting standard molding techniques and simple TEC surface modifications, patterned surfaces with tunable hydrophobicity could be obtained. Moreover, these materials are shown to have great potential for rapid prototyping of microfluidic devices. In the second case, dendritic polymer scaffolds were evaluated for their ability to increase surface interactions and produce functional 3D networks. More specifically, a self-assembled dendritic monolayer approach was explored for producing highly functional dendronized surfaces with specific interactions towards pathogenic E. coli bacteria. Furthermore, a library of heterofunctional dendritic scaffolds, with a controllable and exact number of dual-purpose azide and ene functional groups, has been synthesized. These scaffolds were explored for the production of cell interactive hydrogels and primers for bone adhesive implants. Dendritic hydrogels decorated with a selection of bio-relevant moieties and with Young’s moduli in the same range as several body tissues could be produced by facile UV-induced TEC crosslinking. These gels showed low cytotoxic response and relatively rapid rates of degradation when cultured with normal human dermal fibroblast cells. When used as primers for bone adhesive patches, heterofunctional dendrimers with high azide-group content led to a significant increase in the adhesion between a UV-cured hydrophobic matrix and the wet bone surface (compared to patches without primers).

  • 122067.
    Öberg, Helena
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Brinck, Tore
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Fragment molecular orbital study of the cAMP-dependent protein kinase catalyzed phosphoryl transfer: a comparison with the differential transition state stabilization method2016In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 22, p. 15153-15161Article in journal (Refereed)
    Abstract [en]

    The importance of key residues to the activity of the cAMP-dependent protein kinase catalyzed phosphoryl transfer and to the stabilization of the transition state of the reaction has been investigated by means of the fragment molecular orbital (FMO) method. To evaluate the accuracy of the method and its capability of fragmenting covalent bonds, we have compared stabilization energies due to the interactions between individual residues and the reaction center to results obtained with the differential transition state stabilization method (Szarek, et al., J. Phys. Chem. B, 2008, 112, 11819-11826) and observe, despite a size difference in the fragment describing the reaction center, near-quantitative agreement. We have also computed deletion energies to investigate the effect of virtual deletion of key residues on the activation energy. These results are consistent with the stabilization energies and yield additional information as they clearly capture the effect of secondary interactions, i. e. interactions in the second coordination layer of the reaction center. We find that using FMO to calculate deletion energies is a powerful and time efficient approach to analyze the importance of key residues to the activity of an enzyme catalyzed reaction.

  • 122068. Öberg, J.
    et al.
    Andersson, Evert
    Determining the deterioration cost for railway tracks2009In: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit, ISSN 0954-4097, E-ISSN 2041-3017, Vol. 223, no 2, p. 121-129Article in journal (Refereed)
    Abstract [en]

    The cost of maintaining and renewing railway tracks affected by traffic-dependent deterioration is considerable. It is important not only to have proper maintenance regimes, but also to have knowledge of the interaction between vehicles and track in order to reduce the deterioration of both. In a joint project between Banverket (Swedish Rail Administration) and KTH (Royal Institute of Technology, Stockholm), a model for track deterioration is developed, considering track settlement, component fatigue, abrasive wear, and rolling contact fatigue of rails. The basis of the model is taken from what is considered as state-of-the-art knowledge. The model is used as a basis for a proposed new track access charging regime for Banverket, able to differ between vehicle types based on their characteristics and tendency to deteriorate the tracks. The model is implemented in an Excel (R) environment and applied to Swedish mainline traffic and vehicles. Using representative vehicle characteristics in determining track deterioration, it is predicted that there are large differences between different vehicles regarding their deterioration of the tracks. The model predicts axle load, unsprung mass, and wheelset steering capability as decisive for track deterioration. The model is believed to predict realistic results also for heavy-haul rail operations.

  • 122069. Öberg, J.
    et al.
    Ellervee, P.
    Mokhtari, M.
    Jantsch, A.
    KTH, School of Information and Communication Technology (ICT), Electronic Systems.
    Design of a 1 GIPS Peak Performance Processor using GaAs Technology1994In: Proceedings of the IEEE NORCHIP Conference, 1994Conference paper (Refereed)
  • 122070. Öberg, J.
    et al.
    Isoaho, J.
    Ellervee, P.
    Jantsch, A.
    KTH, School of Information and Communication Technology (ICT), Electronic Systems.
    Hemani, A.
    BABBAGE - A Rule based Tool for Synthesis of Hardware Systems1994In: Proceedings of the IEEE NORCHIP Conference, 1994Conference paper (Refereed)
  • 122071.
    ÖBERG, JENNY
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Industrial Management.
    STENLÖF, ELIN
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Industrial Management.
    What role to play in strategy implementation?: Constructive interplay between middle and frontline managers2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Purpose: The purpose of this research was to study the interplay between middle managers (MMs) and front-line managers (FLMs) in strategy implementation (SI). To successfully manage and run a complex technology corporation a well-performed strategy is essential. By comparing MMs’ and FLMs’ different views and responsibilities in the SI process, both theoretical and empirical. Methodology: Theoretical material regarding leadership, middle and front-line manager roles and responsibilities, as well the strategy implementation process, obstacles and success factors are compared in the study. Supplemented by a general pilot study and primary interviews covering their view of the SI-process, obstacles and leverages, leadership, and their roles description. In total, ten pilot interviews and 12 primary interviews have been conducted, with MMs and FLMs, equally represented. Findings: In large, the main findings regarding the creation of a dynamic interplay between MMs and FLMs were three identified key attributes. Firstly, success in the SI process and constructive dynamic require a clear distribution of tasks and responsibilities between MMs and FLMs or the key responsibilities in the process. Secondly, select key people for the SI process, picked from different levels in the organization with different viewpoint and expertise. Making sure that there are total transparency and knowledge sharing between all key members and organizational levels. This will enable a greater involvement and commitment in the SI-process. Finally, to create a successful SI-process and a dynamic interplay between MMs and FLMs, strategic work must be rewarded equally compared to operational excellence and product-development efforts.

  • 122072.
    ÖBERG, JOAKIM
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Applied Mechanical Engineering (KTH Södertälje).
    GHAZI, SAREM
    KTH, School of Industrial Engineering and Management (ITM), Applied Mechanical Engineering (KTH Södertälje).
    Värdeflödesanalys av en produktionsverkstad2013Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
  • 122073.
    Öberg, Johan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology and Design.
    Wiege, Erik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology and Design.
    Moisture risks with CLT-panels subjected to outdoor climate during construction: focus on mould and wetting processes2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    When going through relevant research, moisture safety guidelines and talking to builders, moisture experts and architects it is clear - and not surprising - that water and wood make no easy combination. The experiences from building with cross laminated timber (CLT) differ from building sites and there are good and bad examples building without weather protection.

    In this study the moisture influence on CLT is analyzed. CLT is a type of massive wood with glued lamellas, increasing usage worldwide as structural elements in buildings. The bulk of the work is performed in the hygrothermal calculation tool WUFI(™). Focus is on the wetting process and the evaluation of mould risk from rain loads during production in Nordic climates. Subsequent drying after built into walls and floors is also evaluated.

    A vast literature survey is performed in order to compare and select material data for modelling CLT. Following the simulation work, moisture content, mould growth and volumetric distortion are judged both with and without weather protection. Results are also compared to measurement data from field tests.

    It is found that short building times are crucial, some weather protection is required all year around and early planning and constructing for moisture safety are crucial. The benefits of prefabrication and short building times using CLT should be exploited. If there is a risk of rainfall exceeding 10-20 mm, arrangements to divert rain loads should be undertaken. If the expected rain loads are above 40 mm or if the building time exceeds 2 weeks, a roof cover will be required. At air humidities averaging 80% and yearly rain exceeding 1200 mm, a complete building cover is recommended. A controlled environment may be expensive, but it speeds up production and shortens drying time.

  • 122074.
    Öberg, John
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology and Design.
    Ståhlfors, Andreas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology and Design.
    Materialegenskaper och dimensioneringsmetodik för vattenledningar: En sammanställning av de material som förekommer i Norrvattens ledningsnät samt dimensioneringsverktyg för plastledningar2012Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis has been conducted in response to a request by Norrvatten for an objective report concerning the materials used in their water supply infrastructure, with a focus on the typical damages linked to specific materials or manufacturing processes. Through interviews with well-informed experts we have received indications that the knowledge regarding the materials used in Norrvatten’s water pipes and said materials’ properties have declined over time, as the older generation of construction planners have left behind a knowledge gap.

    The purpose of the report is to give a good insight into the materials used in Norrvatten’s water supply infrastructure (specifically the pipes used). We claim that a knowledge of the materials used is necessary to analyze the correlation between leakage statistics and the properties of the materials used in the infrastructure.

    The level of information available varies between the different materials. This is mainly caused by the structure of the material and the difficulty in depicting a clear and objective picture of it. The materials and their information are divided into separate chapters to make it easier for the reader to understand the picture we are trying to create.

    Another important chapter in this report is the description of the methods of installation we have chosen to work with; these methods are buried pipelines but also two trenchless methods which are lining and pipe bursting. In reality many more methods that the ones described here exist, but many methods are similar and the ones presented here are those that are most commonly used. This chapter is directly linked to our dimensioning model for pipe replacements concerning strength in regard to earth pressure and traffic load, but also the tensile that occur primarily in the trenchless methods. The dimensionality model is constructed as an Excel document where the user – through utilizing some basic parameters – fills out the document and automatically receives results regarding whether or not the new pipes will withstand the stress it is exposed to.

    Based on the correlation between damage statistics and the use of different materials in the pipe infrastructure we attempt to provide an accurate picture of which materials we deem to be, generally speaking, the most appropriate to make use of.

     

  • 122075.
    Öberg, Johnny
    KTH, Superseded Departments, Electronic Systems Design.
    An Adaptable Environment for Improved High-Level Synthesis1996Licentiate thesis, monograph (Other academic)
  • 122076. Öberg, Johnny
    BABBAGE - A Rule-Based Tool for Synthesis of Hardware Systems1994In: Proceedings of NUTEK programkonferens Ramprogrammet Inbyggda System, 1994, p. 53-61Conference paper (Other academic)
  • 122077.
    Öberg, Johnny
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Clocking Strategies for Networks-on-Chip2003In: Networks-on-Chip / [ed] Axel Jantsch, Kluwer Academic Publishers, 2003, p. 153-172Chapter in book (Refereed)
  • 122078. Öberg, Johnny
    Espresso-based Estimation Methods in the ProGram Compiler1999Report (Other academic)
  • 122079.
    Öberg, Johnny
    KTH, Superseded Departments, Electronic Systems Design.
    ProGram: a grammar-based method for specification and hardware synthesis of communication protocols1999Doctoral thesis, comprehensive summary (Other scientific)
  • 122080. Öberg, Johnny
    SpaceBall-1G: Pipelined 1 GHz Cache Memories in GaAs1995Report (Other academic)
  • 122081.
    Öberg, Johnny
    KTH, School of Information and Communication Technology (ICT), Electronics.
    Synthesis of VLIW accelerators from formal descriptions in a real-time multi-core environment2017In: 14th FPGAworld Conference, FPGAworld 2017 - Academic Proceedings 2017, Association for Computing Machinery (ACM), 2017, p. 23-29Conference paper (Refereed)
    Abstract [en]

    Designing, programming and design space exploration of predictable Real-Time systems on Heterogeneous Multi-Core platforms is a very complex task. The increasing validation costs and time-to-market pressure creates a desire to build systems that are correct by construction. Formal description based on Model of Computations (MoCs) is a convenient way to create high-level models of such systems. The MoCs provide abstraction and high level modeling through a clear set of rules based on mathematics, which can be used as input for system synthesis. A formal synthesis flow would then ensure that the resulting real-time system is both predictable and correct by construction, provided that all transformations used in the flow can be verified/trusted. In this paper we show how a Real-Time computation node in an MPSoC system, described using the Synchronous MoC, can be transformed into a VLIW accelerator. The created accelerator is incorporated as a computation node in a heterogeneous multi-core system implemented on an FPGA.

  • 122082.
    Öberg, Johnny
    KTH, Superseded Departments, Alfvén Laboratory.
    Tuning of JET Transmission Line/Antenna System During ICRH1993Independent thesis Advanced level (degree of Master (Two Years)), 12 credits / 18 HE creditsStudent thesis
  • 122083.
    Öberg, Johnny
    et al.
    KTH, Superseded Departments, Electronic Systems Design.
    Düring, Morgan
    Millberg, Mikael
    Evaluating the Efficacy of utilizing a Protocol Grammar for Modeling of a Processor Architecture: A Case Study2002In: Proceedings of NORCHIP, 2002, p. 309-315Conference paper (Refereed)
  • 122084.
    Öberg, Johnny
    et al.
    KTH, Superseded Departments, Electronic Systems Design.
    Eles, Petru
    Linköpings Tekniska Högskola.
    Hemani, Ahmed
    KTH, Superseded Departments, Electronic Systems Design.
    Kuchcinski, Krzystof
    Linköpings Tekniska Högskola.
    Peng, Zebo
    Linköpings Tekniska Högskola.
    Specifying Local Timing Constraints for HLS Pur­pose1994Report (Other academic)
  • 122085.
    Öberg, Johnny
    et al.
    KTH, Superseded Departments, Electronic Systems Design.
    Eles, Petru
    Linköpings Tekniska Högskola.
    Hemani, Ahmed
    KTH, Superseded Departments, Electronic Systems Design.
    Kuchcinski, Krzystof
    Linköpings Tekniska Högskola.
    Peng, Zebo
    Linköpings Tekniska Högskola.
    Specifying Local Timing Constraints in VHDL for HLS of Digital Systems1995In: Proceedings of the 6th Swedish Workshop on Copmuter System Architecture, 1995Conference paper (Refereed)
  • 122086.
    Öberg, Johnny
    et al.
    KTH, Superseded Departments, Electronic Systems Design.
    Eles, Petru
    Linköpings Tekniska Högskola.
    Hemani, Ahmed
    KTH, Superseded Departments, Electronic Systems Design.
    Kuchcinski, Krzysztof
    Linköpings Tekniska Högskola.
    Peng, Zebo
    Linköpings Tekniska Högskola.
    Specifying Local Timing Constraints for HLS of Dig­ital Systems in VHDL1996In: Proceedings of APCHDL, 1996, p. 145-149Conference paper (Refereed)
  • 122087.
    Öberg, Johnny
    et al.
    KTH, Superseded Departments, Electronic Systems Design.
    Ellervee, Johnny
    Revolver: A high-performance MIMD architecture for collision free computing1998Conference paper (Refereed)
  • 122088.
    Öberg, Johnny
    et al.
    KTH, Superseded Departments, Electronic Systems Design.
    Ellervee, Peeter
    Transition graph representation of FSM and its application to state minimization in the ProGram compiler1998Report (Other academic)
  • 122089.
    Öberg, Johnny
    et al.
    KTH, Superseded Departments, Electronic Systems Design.
    Ellervee, Peeter
    Hemani, Ahmed
    Grammar-based Modelling of Clock Protocols for Low Power Implemen­tations: A Case Study1998Conference paper (Refereed)
  • 122090.
    Öberg, Johnny
    et al.
    KTH, Superseded Departments, Electronic Systems Design.
    Ellervee, Peeter
    Jantsch, Axel
    Using the Revolver Architecture for Data Processing in Heterogeneous Systems2001Report (Other academic)
  • 122091.
    Öberg, Johnny
    et al.
    KTH, Superseded Departments, Electronic Systems Design.
    Ellervee, Peeter
    KTH, Superseded Departments, Electronic Systems Design.
    Jantsch, Axel
    KTH, Superseded Departments, Electronic Systems Design.
    Hemani, Ahmed
    KTH, Superseded Departments, Electronic Systems Design.
    BABBAGE - A Rule basedtool for synthesis of hardware systems1994In: Proc. of IEEE NORCHIP’94, 1994Conference paper (Refereed)
  • 122092.
    Öberg, Johnny
    et al.
    KTH, Superseded Departments, Electronic Systems Design.
    Ellervee, Peeter
    KTH, Superseded Departments, Electronic Systems Design.
    Kumar, Anshul
    KTH, Superseded Departments, Electronic Systems Design.
    Hemani, Ahmed
    KTH, Superseded Departments, Electronic Systems Design.
    Comparing Conventional HLS with Grammar-Based Hardware Synthesis: A Case Study1997In: Proc. of IEEE NORCHIP, 1997Conference paper (Refereed)
  • 122093.
    Öberg, Johnny
    et al.
    KTH, School of Information and Communication Technology (ICT), Electronic Systems.
    Ellervee, Peeter
    Kumar, Anshul
    Hemani, Ahmed
    Comparing Conventional HLS with Grammar-Based Hardware Synthesis: A Case Study1997Conference paper (Refereed)
  • 122094.
    Öberg, Johnny
    et al.
    KTH, Superseded Departments, Electronic Systems Design.
    Ellervee, Peeter
    Mokhtari, Mehran
    Jantsch, Axel
    SpaceBall-1G: A 32-bit 1 GIPS Peak Performance MIMD CPU Targeted for GaAs1995Report (Other academic)
  • 122095.
    Öberg, Johnny
    et al.
    KTH, Superseded Departments, Electrical Systems.
    Ellervee, Peeter
    Mokhtari, Mehran
    Jantsch, Axel
    KTH, Superseded Departments, Electrical Systems.
    Hemani, Ahmed
    A 1 GIPS Peak Performance Multi-Threaded Processor Core Using Interleaved Processing And A Revolving register File Targeted for GaAs1995Conference paper (Refereed)
  • 122096.
    Öberg, Johnny
    et al.
    KTH, Superseded Departments, Electronic Systems Design.
    Isoaho, Jouni
    Tampere University of Technology, Signal Processing Laboratory.
    Ellervee, Peeter
    KTH, Superseded Departments, Electronic Systems Design.
    Jantsch, Axel
    KTH, Superseded Departments, Electronic Systems Design.
    Hemani, Ahmed
    KTH, School of Information and Communication Technology (ICT), Electronic Systems.
    A rule-based approach for improving allocation of filter structures in HLS1996In: Ninth International Conference on VLSI Design, 1996. Proceedings, IEEE conference proceedings, 1996, p. 133-139Conference paper (Refereed)
    Abstract [en]

    A rule based allocator for improving synthesis of filter systems is presented. The principles of the Enhanced AIlocation Rule Language Interpreter (EARLI) are presented. Possible transformations, optimisations and how to express them in EARLI are discussed. Experiments show that relative area gains ranging from 5 to 44%, depending on the chosen target technology, can be achieved using the designers knowledge about the design class. Experiments also indicate that employing direct mapping of CDFG subgraphs onto preoptimised RTL-level macroblocks would have resulted in a relative area gain of 500%. The macroblock had only 16% of the area produced by the HLS-tool

  • 122097.
    Öberg, Johnny
    et al.
    KTH, Superseded Departments, Electronic Systems Design.
    Jantsch, Axel
    Orthogonal High-Level Synthesis from Grammar-based Specifications2001Report (Other academic)
  • 122098.
    Öberg, Johnny
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Kumar, A
    Hemani, Ahmed
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Grammar-based hardware synthesis from port-size independent specifications2000In: IEEE Transactions on Very Large Scale Integration (vlsi) Systems, ISSN 1063-8210, E-ISSN 1557-9999, Vol. 8, no 2, p. 184-194Article in journal (Refereed)
    Abstract [en]

    A protocol defines how systems communicate, There are two ways of specifying the protocol, the language of communication, One way is to specify the automaton that recognizes the language, and this is the approach taken by SDL, etc. The other more abstract way is to specify the grammar of the language and let a tool synthesize the automaton, Directly specifying the automaton makes the specification implementation dependent in two ways: the time behavior is specified in terms of states, and the width of the inputs and outputs is fixed, By specifying the grammar, the specification is potentially independent of both these implementation details and allows design space exploration in these dimensions. This paper presents a grammar-based language, called ProGram, that supports a port-size independent specifications methodology and its application to parts of the Operation and Maintenance protocol, a typical application from the ATM world. The methodology has also been applied to another test set of example designs and compared to standard RTL synthesis and HLS in order to evaluate the quality of the produced designs.

  • 122099.
    Öberg, Johnny
    et al.
    KTH, Superseded Departments, Electronic Systems Design.
    Kumar, Anshul
    Hemani, Ahmed
    Enhanced Synthesis Strategies to cope with Exception Handling in Pro­Gram1998Report (Other academic)
  • 122100.
    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.
    Grammar-based hardware synthesis from port-size independent specifications2000In: IEEE Transactions on Very Large Scale Integration (vlsi) Systems, ISSN 1063-8210, E-ISSN 1557-9999, Vol. 8, p. 184-194Article in journal (Refereed)
    Abstract [en]

    A protocol defines how systems communicate. There are two ways of specifying the protocol, the language of communication. One way is to specify the automaton that recognizes the language, and this is the approach taken by SDL, etc. The other more abstract way ss to specify the grammar of the language and let a tool synthesize the automaton. Directly specifying the automaton makes the specification implementation dependent in two ways: the time behavior is specified in terms of states, and the width of the inputs and outputs is fixed. By specifying the grammar, the specification is potentially independent of both these implementation details and allows design space exploration in these dimensions. This paper presents a grammar-based language, called Program, that supports a port-size independent specifications methodology and its application to parts of the Operation and Maintenance protocol, a typical application from the ATM world. The methodology has also been applied to another test set of example designs and compared to standard RTL synthesis and HLS in order to evaluate the quality of the produced designs.

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