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  • 1.
    Ahlmark, Daniel Innala
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Haptic Navigation Aids for the Visually Impaired2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Assistive technologies have improved the situation in society for visually impaired individuals.The rapid development the last decades have made both work and education much more accessible. Despite this, moving about independently is still a major challenge, one that at worst can lead to isolation and a decreased quality of life. To aid in the above task, devices exist to help avoid obstacles (notably the white cane), and navigation aids such as accessible GPS devices. The white cane is the quintessential aid and is much appreciated, but solutions trying to convey distance and direction to obstacles further away have not made a big impact among the visually impaired. Onefundamental challenge is how to present such information non-visually. Sounds and synthetic speech are typically utilised, but feedback through the sense of touch (haptics) is also used, often in the form of vibrations. Haptic feedback is appealing because it does not block or distort sounds from the environment that are important for non-visual navigation. Additionally, touch is a natural channel for information about surrounding objects, something the white cane so successfully utilises. This doctoral thesis explores the question above by presenting the development and evaluations of dierent types of haptic navigation aids. The goal has been to attain a simple user experience that mimics that of the white cane. The idea is that a navigation aid able to do this should have a fair chance of being successful on the market. Theevaluations of the developed prototypes have primarily been qualitative, focusing on judging the feasibility of the developed solutions. They have been evaluated at a very early stage, with visually impaired study participants.Results from the evaluations indicate that haptic feedback can lead to solutions that are both easy to understand and use. Since the evaluations were done at an early stage in the development, the participants have also provided valuable feedback regarding design and functionality. They have also noted many scenarios throughout their daily lives where such navigation aids would be of use.The thesis document these results, together with ideas and thoughts that have emerged and been tested during the development process. This information contributes to the body of knowledge on dierent means of conveying information about surrounding objects non-visually.

  • 2.
    Ahlmark, Daniel Innala
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    The Development of a Virtual White Cane Using a Haptic Interface2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    For millions of visually impaired individuals worldwide, independent navigation is a major challenge. The white cane can be used to avoid obstacles close-by, but it does not aid in navigation as it is difficult to get a large-scale view of the environment. Technological aids have been developed, notably ones based on GPS, but they have not been widely adopted. This thesis approaches the problem from different perspectives. Firstly, current navigation aids are examined from a user-interaction perspective, leading to some design guidelines on how to present spatial information non-visually. Secondly, a prototype of a new navigation aid (the Virtual White Cane) is proposed, and a field trial with visually impaired participants is described. The idea behind the Virtual White Cane is to utilise the intuitive way humans avoid obstacles by touch, and specifically to leverage the experience white cane users already have. This is accomplished by scanning the environment with a laser rangefinder, and presenting the range information using a haptic interface. The regular white cane is easy to use because it behaves like an extended arm, and so does the Virtual White Cane, albeit working at a much greater distance than the regular cane. A field trial with six experienced white cane users was conducted to assess the feasibility of this kind of interaction. The participants carried out a trial procedure where they traversed a prepared environment using the Virtual White Cane. They did not receive extensive training prior to the trial, the point being that if the Virtual White Cane behaves like a regular one, it should be quick to learn for a white cane user. The results show that spatial information can be feasibly conveyed using a haptic interface. This is demonstrated by the ease with which the field trial participants familiarised themselves with the system, notably adopting a similar usage pattern. In interviews that were conducted following the trial procedures, the participants expressed interest in the idea and thought that being a white cane user helped them use the Virtual White Cane. Despite knowing how to operate the system, the participants found locating objects to be difficult. An extended training period would likely have made this easier, but this problem could also be lessened by understanding what model parameters (such as the length of the virtual cane) should be used.

  • 3.
    Ahlmark, Daniel Innala
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Fredriksson, Håkan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Hyyppä, Kalevi
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Den seende rullstolen2011Conference paper (Other academic)
    Abstract [en]

    In its current form, the white cane has been used by visually impaired people for almost a hundred years. It is an intuitive device that helps visually impaired people navigate independently. For people who, in addition to a visual impairment, also have impaired movement, this independence is not as certain. If a wheelchair or a walker is needed, human assistance might be a necessity.MICA (Mobile Internet Connected Assistant) is a computerized wheelchair that has been equipped with a laser rangefinder that can measure the distance to obstacles in the environment. This information has been used to make the wheelhair able to drive on its own, avoiding obstacles, so that users unable to drive a wheelchair themselves are able to use it.The latest addition to MICA - a virtual white cane - allows visually impaired wheelchair users to virtually touch obstacles in their environment, and thus navigate in a similar way to those using a regular white cane. This is accomplished by generating a simplified 3D model based on the data acquired from the laser rangefinder, and sending this data to a haptic device, allowing users to feel the 3D model.The virtual white cane is still in an early development stage. The first test drive of MICA with the virtual white cane (together known as "The Sighted Wheelchair") was performed on 2011-05-10. A short video called "The Sighted Wheelchair" can be found on YouTube.Future work will focus on developing the software that communicates with the laser rangefinder and the haptic device to improve the user experience. Efforts will also be made to overcome the limitations of the laser rangefinder, improving the 3D model.

  • 4.
    Ahlmark, Daniel Innala
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Fredriksson, Håkan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Hyyppä, Kalevi
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Obstacle Avoidance Using Haptics and a Laser Rangefinder2013In: 2013 IEEE Workshop on Advanced Robotics and its Social Impacts: Tokya, Japan, 7-9 Nov 2013, Piscataway, NJ: IEEE Communications Society, 2013, 76-81 p.Conference paper (Refereed)
    Abstract [en]

    In its current form, the white cane has been used by visually impaired people for almost a century. It is one of the most basic yet useful navigation aids, mainly because of its simplicity and intuitive usage. For people who have a motion impairment in addition to a visual one, requiring a wheelchair or a walker, the white cane is impractical, leading to human assistance being a necessity. This paper presents the prototype of a virtual white cane using a laser rangefinder to scan the environment and a haptic interface to present this information to the user. Using the virtual white cane, the user is able to "poke" at obstacles several meters ahead and without physical contact with the obstacle. By using a haptic interface, the interaction is very similar to how a regular white cane is used. This paper also presents the results from an initial field trial conducted with six people with a visual impairment.

  • 5.
    Ahlmark, Daniel Innala
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Hyyppä, Kalevi
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Presentation of Spatial Information in Navigation Aids for the Visually Impaired2015In: Journal of Assistive Technologies, ISSN 1754-9450, E-ISSN 2042-8723, Vol. 9, no 3, 174-181 p.Article in journal (Refereed)
    Abstract [en]

    Purpose: The purpose of this article is to present some guidelines on how different means of information presentation can be used when conveying spatial information non-visually. The aim is to further the understanding of the qualities navigation aids for visually impaired individuals should possess.Design/methodology/approach: A background in non-visual spatial perception is provided, and existing commercial and non-commercial navigation aids are examined from a user interaction perspective, based on how individuals with a visual impairment perceive and understand space.Findings: The discussions on non-visual spatial perception and navigation aids lead to some user interaction design suggestions. Originality/value: This paper examines navigation aids from the perspective of non-visual spatial perception. The presented design suggestions can serve as basic guidelines for the design of such solutions.

  • 6.
    Ahlmark, Daniel Innala
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Prellwitz, Maria
    Luleå University of Technology, Department of Health Sciences, Health and Rehab.
    Röding, Jenny
    Luleå University of Technology, Department of Health Sciences, Health and Rehab.
    Nyberg, Lars
    Luleå University of Technology, Department of Health Sciences, Health and Rehab.
    Hyyppä, Kalevi
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    An Initial Field Trial of a Haptic Navigation System for Persons with a Visual Impairment2015In: Journal of Assistive Technologies, ISSN 1754-9450, E-ISSN 2042-8723, Vol. 9, no 4, 199-206 p.Article in journal (Refereed)
    Abstract [en]

    Purpose– The purpose of this paper is to describe conceptions of feasibility of a haptic navigation system for persons with a visual impairment (VI). Design/methodology/approach– Six persons with a VI who were white cane users were tasked with traversing a predetermined route in a corridor environment using the haptic navigation system. To see whether white cane experience translated to using the system, the participants received no prior training. The procedures were video-recorded, and the participants were interviewed about their conceptions of using the system. The interviews were analyzed using content analysis, where inductively generated codes that emerged from the data were clustered together and formulated into categories. Findings– The participants quickly figured out how to use the system, and soon adopted their own usage technique. Despite this, locating objects was difficult. The interviews highlighted the desire to be able to feel at a distance, with several scenarios presented to illustrate current problems. The participants noted that their previous white cane experience helped, but that it nevertheless would take a lot of practice to master using this system. The potential for the device to increase security in unfamiliar environments was mentioned. Practical problems with the prototype were also discussed, notably the lack of auditory feedback. Originality/value– One novel aspect of this field trial is the way it was carried out. Prior training was intentionally not provided, which means that the findings reflect immediate user experiences. The findings confirm the value of being able to perceive things beyond the range of the white cane; at the same time, the participants expressed concerns about that ability. Another key feature is that the prototype should be seen as a navigation aid rather than an obstacle avoidance device, despite the interaction similarities with the white cane. As such, the intent is not to replace the white cane as a primary means of detecting obstacles.

  • 7.
    Ahlmark, Daniel Innala
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Prellwitz, Maria
    Luleå University of Technology, Department of Health Sciences, Health and Rehab.
    Röding, Jenny
    Luleå University of Technology, Department of Health Sciences, Health and Rehab.
    Nyberg, Lars
    Luleå University of Technology, Department of Health Sciences, Health and Rehab.
    Hyyppä, Kalevi
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Virtuell vit käpp för den seende rullstolen2013Conference paper (Other academic)
  • 8.
    Ahlmark, Daniel Innala
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    van Deventer, Jan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Hyyppä, Kalevi
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Hand-held navigation aid for visually impaired using haptic feedback2014Conference paper (Other academic)
    Abstract [en]

    The white cane is used by many visually impaired individuals as the primary aid for avoiding obstacles. In this it is unparalleled, but it cannot provide a large-scale view of the surroundings the way vision does. This makes navigating independently a challenge for the visually impaired. We are developing the Virtual White Cane (VWC), a device that uses sensors and haptic technologies to complement the limited view of the cane. Sensors makes it possible to probe obstacles far beyond the range of the white cane, and haptic feedback is familiar to users of the regular cane. The purpose of this device is to act as a complement to the standard cane, providing information about the surroundings that are beyond the cane's reach. This kind of extended view not only helps in anticipating obstacles, but also to navigate. The presentation will focus on the hardware of the currently developed prototype, in addition to some initial user experiences.

  • 9.
    Aitomäki, Yvonne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Berglund, Linn
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Noël, Maxime
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Linder, Tomas
    Löfqvist, Torbjörn
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Light scattering in cellulose nanofibre suspensions: Model and experiments2016In: Computers in Chemistry Proceeding from ACS National Meeting San Diego: Proceeding from ACS National Meeting San Diego, American Chemical Society (ACS), 2016, 122- p., CELL 235Conference paper (Other academic)
    Abstract [en]

    Here light scattering theory is used to assess the size distribution in a suspension of cellulose as it is fibrillated from micro-scaled to nano-scaled fibres. A model based on Monte carlo simulations of the scattering of photons by different sizes of cellulose fibres was used to predict the UV-IF spectrum of the suspensions. Bleached cellulose hardwood pulp was tested and compared to the visually transparent tempo-oxidised hardwood cellulose nanofibres (CNF) suspension. The theoretical results show that different diameter size classes exhibit very different scattering patterns. These classes could be identified in the experimental results and used to establish the size class dominating the suspension. A comparison to AFM/microscope size distribution was made and the results indicated that using the UV-IF light scattering spectrum maybe more reliable that size distribution measurement using AFM and microscopy on dried CNF samples. The UV-IF spectrum measurement combined with the theoretical prediction can be used even at this initial stage of development of this model to assess the degree of fibrillation when processing CNF.

  • 10. Aitomäki, Yvonne
    et al.
    Löfqvist, Torbjörn
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Estimating suspended fibre material properties by modelling ultrasound attenuation2006In: Mathematical Modeling of Wave Phenomena: conference on mathematical modeling of wave phenomea, Växjö, Sweden, 14 - 19 August 2005 / [ed] Börje Nilsson; Louis Fishman, Melville, NY: American Institute of Physics (AIP), 2006, 250-259 p.Conference paper (Refereed)
    Abstract [en]

    An analytical model for use in the inverse problem of estimating material properties of suspended fibres from ultrasonic attenuation has been developed. The ultrasound attenuation is derived theoretically from the energy losses arising when a plane wave is scattered and absorbed off an infinitely long, isotropic, viscoelastic cylinder. By neglecting thermal considerations and assuming low viscosity in the suspending fluid, we can make additional assumptions that provide us with a tractable set of equations that can be solved analytically. The model can then be to used in inverse methods of estimating material properties. We verify the model with experimentally obtained values of attenuation for saturated Nylon fibres. The experimental results from Nylon fibres show local peaks in the attenuation which are thought to be due to the resonant absorption at the eigenfrequencies of the fibres. The results of the experiments show that the model is sufficiently sensitive to detect differences in different types of Nylon. Applications for suspended fibre characterization can be found in the paper manufacturing industry.

  • 11. Aitomäki, Yvonne
    et al.
    Löfqvist, Torbjörn
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Material property estimates from ultrasound attenuation in fibre suspensions2009In: Ultrasonics, ISSN 0041-624X, E-ISSN 1874-9968, Vol. 49, no 4-5, 432-437 p.Article in journal (Refereed)
    Abstract [en]

    An investigation of a new method for measuring fibre material properties from ultrasonic attenuation in a dilute suspension of synthetic fibres of uniform geometry is presented. The method is based on inversely solving an ultrasound scattering and absorption model of suspended fibres in water for the material properties of the fibres. Experimental results were obtained from three suspensions of nylon 66 fibres each with different fibre diameters. A forward solution to the model with reference material values is compared to experimental data to verify the model's behaviour. Estimates of the shear and Young's modulus, the compressional wave velocity, Poisson's ratio and loss tangent from nylon 66 fibres are compared to data available from other sources. Experimental data confirms that the model successfully predicts that the resonance features in the frequency response of the attenuation are a function of diameter. Consistent estimated values for the compressional wave velocity and the Poisson's ratio were found to be difficult to obtain but in combination gave values of shear modulus within previously reported values and with low sensitivity to noise. Young's modulus was underestimated by 54% but was consistent and had low sensitivity to noise. The underestimation is believed to be caused by the assumption of isotropic material used in the model. Additional tests on isotropic fibre would confirm this. Further analysis of the model sensitivity and the reasons for the resonance features are required.

  • 12.
    Aitomäki, Yvonne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Löfqvist, Torbjörn
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Sounding Out Paper Pulp: Ultrasound Spectroscopy of Dilute Viscoelastic Fibre Suspensions Acoustics and Ultrasonics2006Conference paper (Other academic)
    Abstract [en]

    A model of attenuation of ultrasound in fibre suspensions is compared to a model of backscattering pressure from submersed cylinders subjected to a sound wave. This analysis is carried out in the region where the wavelength is of the same order as that of the diameter of the fibre. In addition we assume the cylinder scatterer to have no intrinsic attenuation and the longitudinal axis of the scatterer is assumed to be perpendicular to the direction of propagation of the incident wave. Peaks in the frequency response of both the backscattering pressure, expressed in the form of a form function, and the attenuation are shown to correspond. Similarities between the models are discussed. Since the peaks in the form function are due to resonance of the cylinder, we infer that the peaks in the attenuation are also due to resonance. The exact nature of the waves causing the resonance are still unclear however the first resonance peaks are related to the shear wave and hence the shear modulus of the material. The aim is to use the attenuation model for solving the inverse problem of calculating paper pulp material properties from attenuation measurements. The implications of these findings for paper pulp property estimation is that the supporting fluid could, if possible, be matched to density of that of pulp fibres and that the estimation of material properties should be improved by selecting a frequency range that in the region of the first resonance peaks.

  • 13.
    Aitomäki, Yvonne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Löfqvist, Torbjörn
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Delsing, Jerker
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Estimating material properties of solid and hollow fibers in suspension using ultrasonic attenuation2013In: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, ISSN 0885-3010, E-ISSN 1525-8955, Vol. 60, no 7, 1424-1434 p.Article in journal (Refereed)
    Abstract [en]

    Estimates of the material properties of hollow fibers suspended in a fluid using ultrasound measurements and a simple, computationally efficient analytical model are made. The industrial application is to evaluate the properties of wood fibers in paper pulp. The necessity of using a layered cylindrical model (LCM) as opposed to a solid cylindrical model (SCM) for modeling ultrasound attenuation in a suspension of hollow fibers is evaluated. The two models are described and used to solve the inverse problem of estimating material properties from attenuation in suspensions of solid and hollow polyester fibers. The results show that the measured attenuation of hollow fibers differs from that of solid fibers. Elastic properties estimates using LCM with hollow-fiber suspension measurements are similar to those using SCM with solid-fiber suspension measurements and compare well to block polyester values for elastic moduli. However, using the SCM with the hollow-fiber suspension did not produce realistic estimations. In conclusion, the LCM gives reasonable estimations of hollow fiber properties and the SCM is not sufficiently complex to model hollow fibers. The results also indicate that the use of a distributed radius in the model is important in estimating material properties from fiber suspensions.

  • 14.
    Aittamaa, Simon
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Programming embedded real-time systems: implementation techniques for concurrent reactive objects2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    An embedded system is a computer system that is a part of a larger device with hardware and mechanical parts. Such a system often has limited resources (such as processing power, memory, and power) and it typically has to meet hard real-time requirements. Today, as the area of application of embedded systems is constantly increasing, resulting in higher demands on system performance and a growing complexity of embedded software, there is a clear trend towards multi-core and multi-processor systems. Such systems are inherently concurrent, but programming concurrent systems using the traditional abstractions (i.e., explicit threads of execution) has been shown to be both difficult and error-prone. The natural solution is to raise the abstraction level and make concurrency implicit, in order to aid the programmer in the task of writing correct code. However, when we raise the abstraction level, there is always an inherent cost. In this thesis we consider one possible concurrency model, the concurrent reactive object approach that offers implicit concurrency at the object level. This model has been implemented in the programming language Timber, which primarily targets development of real-time systems. It is also implemented in TinyTimber, a subset of the C language closely matching Timber’s execution model. We quantify various costs of a TinyTimber implementation of the model (such as context switching and message passing overheads) on a number of hardware platforms and compare them to the costs of the more common thread-based approach. We then demonstrate how some of these costs can be mitigated using stack resource policy. On a separate track, we present a feasibility test for garbage collection in a reactive real-time system with automatic memory management, which is a necessary component for verification of correctness of a real-time system implemented in Timber

  • 15.
    Aittamaa, Simon
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Eriksson, Johan
    Lindgren, Per
    Uniform scheduling of internal and external events under SRP-EDF2010In: Annual International Conference on Real-Time and Embedded Systems ( RTES 2010): 1-2 November 2010, Mandarin Orchard Hotel, Singapore, 2010Conference paper (Refereed)
    Abstract [en]

    With the growing complexity of modern embedded real-time systems, scheduling and managing of resources has become a daunting task. While scheduling and resource management for internal events can be simplified by adopting a commonplace real-time operating system (RTOS), scheduling and resource management for external events are left in the hands of the programmer, not to mention managing resources across the boundaries of external and internal events. In this paper we propose a unified system view incorporating earliest deadline first (EDF) for scheduling and stack resource policy (SRP) for resource management. From an embedded real-time system view, EDF+SRP is attractive not only because stack usage can be minimized, but also because the cost of a pre-emption becomes almost as cheap as a regular function call, and the number of preemptions is kept to a minimum. SRP+EDF also lifts the burden of manual resource management from the programmer and incorporates it into the scheduler. Furthermore, we show the efficiency of the SRP+EDF scheme, the intuitiveness of the programming model (in terms of reactive programming), and the simplicity of the implementation.

  • 16.
    Albano, Michele
    et al.
    CISTER, ISEP/INESC-TEC Polytechnic Institute of Porto.
    Barbosa, Paulo Miguel
    CISTER, ISEP/INESC-TEC Polytechnic Institute of Porto.
    Silva, Jose
    CISTER, ISEP/INESC-TEC Polytechnic Institute of Porto.
    Duarte, Roberto
    CISTER, ISEP/INESC-TEC Polytechnic Institute of Porto.
    Ferreira, Luis Lino
    CISTER, ISEP/INESC-TEC Polytechnic Institute of Porto.
    Delsing, Jerker
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Quality of Service on the Arrowhead Framework2017In: 2017 IEEE 13th International Workshop on Factory Communication Systems (WFCS), Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2017Conference paper (Refereed)
    Abstract [en]

    Quality of Service (QoS) is an important enabler for communication in industrial environments. The Arrowhead Framework was created to support local cloud functionalities for automation applications by means of a Service Oriented Architecture. To this aim, the framework offers a number of services that ease application development, among them the QoSSetup and the Monitor services, the first used to verify and configure QoS in the local cloud, and the second for online monitoring of QoS. This paper describes how the QoSSetup and Monitor services are provided in a Arrowhead-compliant System of Systems, detailing both the principles and algorithms employed, and how the services are implemented. Experimental results are provided, from a demonstrator built over a real-time Ethernet network.

  • 17. Alrifaiy, Ahmed
    et al.
    Borg, Johan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Lindahl, Olof
    Ramser, Kerstin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    A lab-on-a-chip for hypoxic patch clamp measurements combined with optical tweezers and spectroscopy: first investigations of single biological cells2015In: Biomedical engineering online, ISSN 1475-925X, E-ISSN 1475-925X, Vol. 14, 36Article in journal (Refereed)
    Abstract [en]

    The response and the reaction of the brain system to hypoxia is a vital research subject that requires special instrumentation. With this research subject in focus, a new multifunctional lab-on-a-chip (LOC) system with control over the oxygen content for studies on biological cells was developed. The chip was designed to incorporate the patch clamp technique, optical tweezers and absorption spectroscopy. The performance of the LOC was tested by a series of experiments. The oxygen content within the channels of the LOC was monitored by an oxygen sensor and verified by simultaneously studying the oxygenation state of chicken red blood cells (RBCs) with absorption spectra. The chicken RBCs were manipulated optically and steered in three dimensions towards a patch-clamp micropipette in a closed microfluidic channel. The oxygen level within the channels could be changed from a normoxic value of 18% O 2 to an anoxic value of 0.0-0.5% O 2. A time series of 3 experiments were performed, showing that the spectral transfer from the oxygenated to the deoxygenated state occurred after about 227 ± 1 s and a fully developed deoxygenated spectrum was observed after 298 ± 1 s, a mean value of 3 experiments. The tightness of the chamber to oxygen diffusion was verified by stopping the flow into the channel system while continuously recording absorption spectra showing an unchanged deoxygenated state during 5400 ± 2 s. A transfer of the oxygenated absorption spectra was achieved after 426 ± 1 s when exposing the cell to normoxic buffer. This showed the long time viability of the investigated cells. Successful patching and sealing were established on a trapped RBC and the whole-cell access (Ra) and membrane (Rm) resistances were measured to be 5.033 ± 0.412 M Ω and 889.7 ± 1.74 M Ω respectively.

  • 18.
    Andersson, Ulf
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Bortolin, Gianantonio
    Volvo CE.
    Backén, Staffan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Estimation of side-slip angles of a Volvo A25E articulated all-wheel drive hauler based on GPS/INS measurements2011In: Proceedings of SAE 2011 Commercial Vehicle Engineering Congress and Exhibition, Society of Automotive Engineers, Incorporated , 2011Conference paper (Refereed)
    Abstract [en]

    Traction control for off-road vehicles such as articulated all-wheel drive haulers is of great importance to improve the vehicle performance. A well-known method to reduce the slip and thereby improve the traction is to engage differential locks in the driveline of the vehicle. The drawbacks of differential locks engaged are for instance increased wear, increased fuel consumption but also reduced turnability of the vehicle. Therefore, the differentials should be locked only when necessary, ideally only when slip occurs or is about to occur. A number of methods to detect slip has been reported in the literature. Some of them utilize dynamical models of the vehicle where side-slip angles are important inputs. This paper describes an off-line estimator for the side-slip angles of an articulated vehicle based on measurements from Global Positioning System (GPS) and Inertial Navigation System (INS). The current implementation is a proof of concept and the intention is to develop a system that can be used as a reference for on-line estimators. By comparing measurements from two GPS/INS units, mounted on the front and rear part of the vehicle, it is possible to estimate the side-slip angles of both the front and rear part. The method has been tested on a Volvo A25E articulated all-wheel drive hauler equipped with two high precision GPS/INS units (NovAtel's SPAN-CPT). Tests have been performed when driving on asphalt, gravel and snow. The results from the tests are discussed.

  • 19.
    Andersson, Ulf
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Mrozek, Kent
    Åström, Kalle
    Hyyppä, Kalevi
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Path design and control algorithms for articulated mobile robots1997In: Proceedings of the International Conference on Field and Service Robotics / [ed] Alexander Zelinsky, 1997, 405-411 p.Conference paper (Refereed)
  • 20. Antonini, G.
    et al.
    Ekman, Jonas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Ruehli, A.E.
    Accuracy and stability enhancement of PEEC models for the time and frequency domain2006In: EMC Europe 2006 Barcelona: [International Symposium on Electromagnetic Compatibility ; September 4 - 8, 2006, Barcelona, Spain] / [ed] Ferran Silva, Barcelona: Universidad Politécnica de Cataluña , 2006Conference paper (Refereed)
  • 21.
    Antonini, G.
    et al.
    Università Degli Studi di l'Aquila.
    Miscione, G.
    Università Degli Studi di l'Aquila.
    Ekman, Jonas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    PEEC modeling of automotive electromagnetic problems2008In: Applied Computational Electromagnetics Society Newsletter, ISSN 1056-9170, Vol. 23, no 1, 39-50 p.Article in journal (Refereed)
    Abstract [en]

    This paper presents the combination of the nonorthogonal Partial Element Equivalent Circuit (PEEC) models and interconnect structures through a macromodel approach for the analysis of automotive electromagnetic problems. The applications are within automotive computational electromagnetics due to the typical combination of cable harnesses and chassis structures. It is shown that PEEC-based solvers are capable of handling electrically large problems with high geometrical complexity for detailed analysis in both the time- and frequency- domain with attached multi-conductor transmission lines.

  • 22. Antonini, G.
    et al.
    Miscione, G.
    Ekman, Jonas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Anttu, Peter
    PEEC modeling of automotive electromagnetic problems2006In: Proceedings of the International Conference of Numerical Analysis and Applied Mathematics: official conference European Society of Computational Methods in Sciences and Engineering (ESCMSE) / [ed] T. E. Simos, John Wiley & Sons, 2006Conference paper (Refereed)
  • 23.
    Antonini, Giulio
    et al.
    Department of Electrical Engineering, University of L’Aquila.
    Delsing, Jerker
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Ekman, Jonas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Orlandi, Antonio
    Department of Electrical Engineering, University of L’Aquila.
    Ruehli, Albert
    IBM T.J. Watson Research Center, Yorktown Heights.
    PEEC development road map 20072007Report (Other academic)
    Abstract [en]

    A road map for the long term development of the partial element equivalent circuit (PEEC) method is presented. Emerging areas are pointed out together with a solution strategy. Special attention is given to speed up approaches, mesh generation, and time domain stability. The purpose with the road map is to facilitate a unified development of the method into an electromagnetic modeling method suitable for incorporation in integrated analysis tools for engineers for electromagnetic compatibility and electromagnetic interference purpose.

  • 24.
    Antonini, Giulio
    et al.
    Department of Electrical Engineering, University of L’Aquila.
    Ekman, Jonas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Ruehli, Albert
    IBM T.J. Watson Research Center, Yorktown Heights.
    Parallel waveform relaxation and matrix solution for large PEEC model problems2007In: 2007 IEEE Electrical Performance of Electronic Packaging, IEEE Communications Society, 2007, 241-244 p.Conference paper (Refereed)
    Abstract [en]

    Excessive compute time is becoming a key problem for high performance system modeling as the complexity of the electromagnetic and circuit models are increasing. At the same time the PEEC models are locally becoming more complex with the increased importance of dielectric and skin-effect losses. Fortunately, parallel processing removes the restriction on the availability of compute resources. In this paper,we consider a combined approach where WR is used for the predominant weak coupling while a Gaussian matrix solver is used for the parallelization of the strongly coupled parts of the overall system.

  • 25.
    Antonini, Giulio
    et al.
    Department of Electrical Engineering, University of L’Aquila.
    Ekman, Jonas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Ruehli, Albert E.
    IBM T.J. Watson Research Center, Yorktown Heights.
    Waveform relaxation for the parallel solution of large PEEC model problems2007In: 2007 IEEE International Symposium on Electromagnetic Compatibility: workshop and tutorial notes : July 8-13, 2007 Honolulu, Hawaii., Piscataway, NJ: IEEE Communications Society, 2007Conference paper (Refereed)
    Abstract [en]

    The solution of large 3D electromagnetic models is important for the modeling of a multitude of EMC, PI and SI problems. In this paper, we explore new algorithms for the parallel solution of large time domain 3D electromagnetic problems. Our approach is to use a volume Partial Element Equivalent Circuit (PEEC) electromagnetic formulation in combination with a Waveform Relaxation (WR) algorithm. In WR, we split the system into smaller subsystems and we break weak couplings so that the problem can be solved iteratively. WR has been used to solve a multitude of different problems. It is especially suited for parallel processing due to its favorable compute time to communication ratio. We consider a specific example for the application of WR to PEEC models.

  • 26.
    Antonini, Giulio
    et al.
    University of L’Aquila.
    Ekman, Jonas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Scogna, Antonio Ciccomancini
    University of L’Aquila.
    Ruehli, Albert E.
    IBM Research Division, Yorktown Heights, NY.
    A comparative study of PEEC circuit elements computation2003In: IEEE International Symposium on Electromagnetic Compatibility: symposium record : Boston, August 18-22, 2003, Piscataway, NJ: IEEE Communications Society, 2003, 810-813 p.Conference paper (Refereed)
    Abstract [en]

    A key use of the PEEC method is the solution of combined electromagnetic and circuit problems as they occur in many situations in todays very large scale integrated circuits (VLSI) and systems. An important aspect of this approach is the fast and accurate computation of PEEC circuit matrix elements, the partial inductances and normalized coefficients of potential. Recently, fast multipole methods (FMM) have been applied to the PEEC method in the frequency domain as a way to speed up the solution. In this paper, we consider the fast evaluation of the PEEC circuit matrix elements by two different methods, a matrix version of the (FMM) PEEC method and a method, which we call the fast multi-function (FMF) PEEC approach. In this technique, the matrix coefficients are evaluated using analytical functions approximation of the coefficients in combination with a proper choice of numerical quadrature formulas.

  • 27.
    Axell, Erik
    et al.
    Swedish Defence Research Agency, Department of Robust Telecommunications.
    Eklöf, Fredrik M.
    Swedish Defence Research Agency, Department of Robust Telecommunications.
    Alexandersson, Mikael
    Swedish Defence Research Agency, Department of Robust Telecommunications.
    Johansson, Peter
    Swedish Defence Research Agency, Department of Robust Telecommunications.
    Akos, Dennis
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Jamming detection in GNSS receivers: Performance evaluation of field trials2013In: Proceedings of the 26th international technical meeting of the Satellite Division of The Institute of Navigation, ION GNSS+ 2013, Sept. 16 - 20, 2013, Nashville Convention Cener, Nashville, Tennessee, Manassas, VA: Institute of Navigation, The , 2013, Vol. 3, 2542-2551 p.Conference paper (Refereed)
    Abstract [en]

    In this work, we evaluate the detection performance of a number of commercial interference detectors and, in addition, of a detector that uses the automatic gain control (AGC) levels as test statistic. The AGC detector has been implemented on a Novatel GPS receiver and on a Universal Software Radio Peripheral (USRP). The evaluations are based on actual measurements of GPS signals and different types of jamming signals, which have been performed at the Vidsel test range in northern Sweden. The AGC detector was shown to work well for all types of jamming signals, in particular the one implemented on the USRP. The Chronos CTL-3500 was also shown to perform quite well for all kinds of signals, although not as good as the USRP with an AGC detector. Quite surprisingly, the J-alert was only able to detect the wideband (20 MHz) signal but not the narrow band (<2MHz) signals. By contrast, the jamming indicator on the Ublox 6 receiver was only able to detect a slowly varying modulated CW (MCW) signal, but not the signals with larger bandwidth (2 and 20 MHz). We confirmed that C/N0-based detectors could work well in a static scenario, but are not suitable in a dynamic scenario, since they cannot distinguish between decreased GPS signal strength (e.g. indoors) and an increased interference level.

  • 28.
    Axell, Erik
    et al.
    Swedish Defence Research Agency, Department of Robust Telecommunications.
    Eklöf, Fredrik M.
    Swedish Defence Research Agency, Department of Robust Telecommunications.
    Alexandersson, Mikael
    Swedish Defence Research Agency, Department of Robust Telecommunications.
    Johansson, Peter
    Swedish Defence Research Agency, Department of Robust Telecommunications.
    Akos, Dennis
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Jamming detection in GNSS receivers: Performance evaluation of field trials2015In: Navigation, ISSN 0028-1522, E-ISSN 2161-4296, Vol. 62, no 1, 73-82 p.Article in journal (Refereed)
    Abstract [en]

    We evaluate the detection performance of several commercial interference detectors and of a detector that uses the automatic gain control (AGC) level as a test statistic. The evaluations are based on actual measurements of GPS signals and different types of jamming signals, and were performed at the Vidsel test range in northern Sweden.The AGC detector and the Chronos CTL-3500 were shown to work well for all types of jamming signals. The J-alert was able to detect a wideband (20 MHz) signal but not the narrow band (<2 MHz) signals. By contrast, the jamming indicator on a Ublox 6H receiver was only able to detect a slowly varying modulated CW signal, but not signals with larger bandwidth (>2 MHz). We confirmed that C/N0-based Android application detectors could work well in static scenarios but are not suitable in dynamic scenarios, since they cannot distinguish between decreased GPS signal strength and increased interference

  • 29.
    Backén, Staffan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Likelihood of detection and computational complexity of GPS acquisition algorithms2009In: Proceedings of the 22nd international technical meeting of the Satellite Division of the Institute of Navigation, ION GNSS 2009: Sept. 22 - 25, 2009, Savanna Convention Center, Savannah, Georgia, Manassas, Va: Institute of Navigation, The , 2009, 3153-3160 p.Conference paper (Refereed)
    Abstract [en]

    A key parameter of GNSS receiver performance is the sensitivity, meaning how weak signals the receiver can acquire and track. For acquisition, this is typically measured by the minimum signal strength that can be detected with a certain probability. In this paper, a novel method of computing the probability of detection is presented. In contrast with prevailing techniques, it takes receiver parameters such as correlator and doppler spacing into account when computing the probability distribution function. The likelihood of data bit switches inside the correlation window is also considered in a similar fashion. The method is demonstrated both on a traditional correlator architecture, and on two different FFT based acquisition algorithms, coherent and non-coherent. Further, the computational complexity of the different algorithms is evaluated for a general computing platform. The combination of these two methods provide valuable insight into the problem of minimizing power consumption while maximizing sensitivity for software based GNSS receivers.

  • 30.
    Backén, Staffan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    On dynamic array processing for GNSS software receivers2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis presents contributions in the field of satellite navigation with a focus on array processing and related implementation issues. For readers not familiar with GNSS, it also includes a brief overview of satellite navigation.Compared to the state of the art only ten years ago, modern GNSS receivers are very capable. One reason for this improvement is advances in the semiconductor industry that have increased both the available processing power and the energy efficiency. An active research community have also made important contributions resulting in more sophisticated algorithms. To improve receiver performance even further, auxiliary sensors such as gyros and accelerometers are becoming increasingly common. A related option involves using an antenna with several physical elements. This is known as an antenna array and is often used for radar, sonar and telecommunication applications. Array processing can also be used for GNSS and as such it is the primary focus of this thesis. An array allows for exploration of the spatial domain, in other words a receiver that may differentiate between signals depending on the direction of arrival. For GNSS, where interference and multipath (signal reflection off, for example, buildings or the ground) may be significant sources of error, this is an attractive solution. Although array processing have been the subject of extensive research efforts within other fields, there are several remaining issues with regards to how these techniques can be implemented in a GNSS receiver.With regards to array processing there are also properties unique to GNSS, such as multiple signal sources at known positions, that have not been explored sufficiently in previous efforts. In this thesis we show how these properties can be exploited to improve receiver performance in dynamic scenarios. In short, the orientation of the antenna platform is estimated accurately (typical variance around 1°) using beamforming techniques. This information is then used to achieve a better estimate of the radio environment by allowing for longer integration periods when estimating the covariance matrices. A better estimate of the covariance matrices directly translates into improved receiver performance, especially so in areas of moderate levels of multipath/interference.Further, a method to calibrate GNSS array antennas using real signals is investigated in detail. Instead of resorting to electromagnetic simulations that requires precise knowledge about the antenna and installation factors, or RF chamber measurement that is expensive, it is shown how the array antenna can be calibrated using live signals. The accuracy of the resulting model is verified using real data.Also, the first implementation of an RF record and replay system is presented. With such a system data can be recorded in a specific environment, generally a time consuming task, and later played back into the antenna input of any GNSS receiver. Such systems are nowadays commercially available and have proven very useful for testing and validation of GNSS receivers. Throughout the thesis, the required receiver architecture and practical viability of the proposed algorithms are considered.

  • 31.
    Backén, Staffan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Towards dynamic array processing for GNSS software receivers2007Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Since the very first Global Positioning System satellite was launched in 1978, Global Navigation Satellite Systems (GNSS) have developed into a world wide utility, providing everyone with an affordable method for determining accurate position and time. However, the system is susceptible to multipath (when the signal is reflected off a surface), interference (other signals in the same frequency band) and attenuation (for example canopies blocking some of the signal energy). Array processing of GNSS signals have lately drawn quite a bit of attention from the research community, where issues (susceptibility to interference, multipath and attenuation) can be mitiged to some degree. GNSS baseband processing is generally implemented in hardware (digital logic), although software based processing are swiftly gaining popularity among researchers. This thesis discusses the implementation of a software based GNSS array processing system with an emphasis on hardware, calibration and initial signal detection. Low cost, ASIC based front-ends are examined with regards to phase and gain stability, and are found to meet the requirements for array processing of GNSS signals. An antenna calibration technique using live GNSS signals (as opposed to anechoic chamber measurements) is proposed, where the predictable orbits and geometric diversity of GNSS are exploited. A system capable of replaying recorded narrow band GNSS signals into any low cost receiver is also discussed. Finally, efficient methods to acquire GNSS signals using an antenna array system are proposed.

  • 32.
    Backén, Staffan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Akos, Dennis
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Antenna array calibration using live GNSS signals2006In: Proceedings of the third ESA Workshop on Satellite Navigation User Equipment Technologies: NAVITEC 2006, 2006Conference paper (Refereed)
    Abstract [en]

    An anechoic chamber free approach to GNSS antenna array gain and phase calibration is proposed and evaluated for a stationary array. The constellation change of the satellites was used to measure the variations in gain and phase over two twelve hour periods. The results was compared to an array calibrated using traditional methods in an anechoic chamber. It is shown that the method agrees well with the traditional method. Care was taken to make sure interference and multipath levels were low.The processing is performed using acquisition and tracking loop software implemented in Matlab. The IF data is recorded with a multi front end recording system.

  • 33.
    Backén, Staffan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Akos, Dennis
    GNSS antenna arrays: hardware requirements for algorithm implementation2006Conference paper (Refereed)
  • 34.
    Backén, Staffan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Akos, Dennis
    GNSS antenna arrays: hardware requirements for algorithm implementation2006Report (Other academic)
    Abstract [en]

    GNSS antenna arrays and beam forming/nulling have long been studied from an algorithm perspective. However, the hardware and implementation design issues are not as well understood. A low cost data collection platform for continuous recording of eight simultaneous IF streams are presented with an analysis of its performance. Also, the requirements on front end components are examined, specifically their impact on array processing versus single antenna processing. Focus is exclusively on digital beam forming as that is the only feasible approach for advanced algorithm implementation, and differences between traditional receiver architectures and a software defined radio approach will be emphasized. It is found that simultaneous recording of multiple IF streams allows for great flexibility in the field of antenna array processing for GNSS. Also, commercial off the shelf components shows sufficient performance, although care must be taken regarding issues such as phase consistency and cross talk between front ends.

  • 35.
    Backén, Staffan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Akos, Dennis
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Nordenvaad, Magnus Lundberg
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Post-processing dynamic GNSS antenna array calibration and deterministic beamforming2008In: Proceedings of the 21th International Technical Meeting of the Satellite Division of the Institute of Navigation: ION GNSS 2008, 2008, Vol. 3, 1311-1319 p.Conference paper (Refereed)
    Abstract [en]

    An array processing GNSS (Global Navigation Satellite System) receiver may provide increased accuracy, reliability and integrity by forming beams towards satellites and nulls towards interference or reflective surfaces. Also, software defined receivers have proven themselves versatile and provide a convenient environment to implement novel algorithms.This paper first describes the gain/phase calibration of a seven element custom array antenna and proceeds to compare the single antenna performance to that of the performance attained by forming beams towards the satellites. IF (Intermediate Frequency) data, high rate samples representing the received signal in a narrow band around the GPS L1 frequency, from an array antenna have been recorded both in an environment with open sky conditions and also in more challenging areas (central Boulder, Colorado). Simultaneously, data from a high quality GPS based INS was recorded in order to obtain accurate estimates of position/ orientation. Calibration of the system (including antennas and front-ends) was performed using data from the benign environment, and based on this information, deterministic beams were formed towards the satellites using data from the semi-urban dataset. The single antenna accuracy was then compared to the position obtained by processing after forming beams.

  • 36.
    Backén, Staffan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Akos, Dennis
    Wilson, Steve G.
    University of Boulder at Colorado.
    RF replay system for narrowband GNSS if signals2011In: IEEE Transactions on Aerospace and Electronic Systems, ISSN 0018-9251, E-ISSN 1557-9603, Vol. 47, no 1, 586-595 p.Article in journal (Refereed)
    Abstract [en]

    Although GNSS RF signal simulators have long possessed the capability to generate scenarios they are, for example, not yet able to model a realistic scenario with complex multipath. Software defined receivers bridge the gap between simulated and real data to the extent that they may offer a replay capability, where a data set is first recorded to disk and later can be processed several times. Unfortunately, the recorded data generally can not be used by other GNSS receivers, making receiver to receiver comparisons difficult and time consuming.This paper describes a system capable of replaying recorded IF data into any narrow bandwidth L1 GNSS receiver, including an evaluation of the difference (position, timing and SNR) between live and replayed data using a high sensitivity, consumer grade receiver. The performance of the replayed data set was found to match that of the live data.

  • 37.
    Backén, Staffan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Nordenvaad, Magnus Lundberg
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Akos, Dennis
    A novel software defined research receiver architecture2009In: Proceedings of the 13th IAIN World Congress: Stockholm, 27-30 October 2009, Nordic Institute of Navigation , 2009Conference paper (Refereed)
    Abstract [en]

    Software defined receivers (SDR) are an increasingly important tool within the GNSS research community as the high level of flexibility offer a significant advantage over traditional hardware implementations. Over the last decade, software receivers have been used to investigate techniques as diverse as bi-static radar (additional correlators), multipath mitigation techniques, GPS/INS integration and array processing.Mentioned above are only a few examples of features that could be required of an SDR, other include support for new signals (Galileo, GPS L5), multiple data file formats, high sensitivity and support for very long data sets. The large number of available features should ideally be coupled with program simplicity (such that other people can understand the program) and efficiency. This paper discusses these issues and proposes several solutions such asgeneralized data buffers (that is trivial to extend for new data formats) and a unified tracking structure (regardless of signal modulation). Examples are given using a Matlab implementation based on the Borre/Akos book Ä Software-Defined GPS and Galileo Receiver", however with significant modifications. Where critical, Java is used to increase performance while maintaining cross platform compatibility. Near real-time operation is available under optimal circumstances and the receiver currently supports GPS C/A- and GPS P-code signals.

  • 38.
    Barabash, Victoria
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Ejemalm, Johnny
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Kuhn, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Milz, Mathias
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Molin, Sven
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Johansson, Jonny
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Westerberg, Lars-Göran
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Masters Programs in Space Science and Engineering in Northern Sweden2017Conference paper (Refereed)
  • 39.
    Barraza, Sergio Martin Del Campo
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Towards autonomous condition monitoring sensor systems2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Rolling element bearings are used to carry load and reduce friction between moving parts in rotating machines, which play a central role in society and industry, for example in the transportation and energy sectors. It is essential to monitor and maintain the condition of bearings such that machines can operate efficiently and any failures resulting in unplanned stoppages are avoided. Therefore, bearings with embedded sensing capabilities are becoming increasingly common, which makes it possible to consider bearings to be sensor systems that can monitor the condition of rotating machines. However, the task of automatically analyzing the signals is challenging because machines are different and evolve over time; moreover, the complexity of the signals, machines and possible failure modes is high and costly to accurately predict and model. Therefore, the use of unsupervised machine learning methods for the automated analysis of such signals and the detection of abnormal operational conditions is an interesting subject worth further exploration.Previous work has strongly depended on static features defined by human experts and thresholds that characterize abnormal operational conditions. Furthermore, machine learning methods typically depend on such static features to classify the faults and various operational conditions of the machine. This approach is challenging when reusing a method for different applications and environments, wherein similar features and thresholds can have different meanings. This problem is typically solved by reconfiguring or redesigning the condition monitoring system, thereby constraining the applicability and efficiency of the method.In this licentiate thesis, I investigate unsupervised methods for feature learning and anomaly detection. In particular, I focus on vibration signals, which contain information about both the bearing condition and the condition of the machine.The considered model represents the signal as a linear superposition of noise and atomic waveforms of arbitrary shape, amplitude and position. The atomic waveforms are adapted to each signal and machine using an unsupervised probabilistic optimization method and are considered features of the machine and physical processes exciting the signal. This model can automatically adapt the features to different environmental and operational conditions, thereby forming the basis for the development of a condition monitoring system that requires a minimum of manual configuration. Additionally, the model produces sparse codes that decrease the sensor data rate and, in principle, simplify the task of analyzing and communicating complex sensor information in resource-constrained embedded sensor systems.The thesis outlines an implementation of a sparse representation and dictionary learning method that is applied to vibration signals. I describe how signal analysis is performed using typical static pre-defined features and contrast this analysis with an analysis based on features that are automatically derived from the signal. In particular, the analysis focuses on the evolution of the vibration signal and the features when a fault develops within the ball bearing of a rotating machine. The evolution rate of learned features is defined and proposed as an interesting quantity for an autonomous condition monitoring process, and a first step towards an FPGA implementation of the method is presented.

  • 40.
    Barraza, Sergio Martin Del Campo
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Albertsson, Kim
    Luleå University of Technology, Professional Support, IT-Service.
    Nilsson, Joakim
    Engineering Physics student at the Luleå University of Technology.
    Eliasson, Jens
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Sandin, Fredrik
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    FPGA prototype of machine learning analog-to-feature converter for event-based succinct representation of signals2013In: IEEE International Workshop on Machine Learning for Signal Processing, Piscataway, NJ: IEEE Signal Processing Society, 2013, 6661996Conference paper (Refereed)
    Abstract [en]

    Sparse signal models with learned dictionaries of morphological features provide efficient codes in a variety of applications. Such models can be useful to reduce sensor data rates and simplify the communication, processing and analysis of information, provided that the algorithm can be realized in an efficient way and that the signal allows for sparse coding. In this paper we outline an FPGA prototype of a general purpose "analog-to-feature converter", which learns an overcomplete dictionary of features from the input signal using matching pursuit and a form of Hebbian learning. The resulting code is sparse, event-based and suitable for analysis with parallel and neuromorphic processors. We present results of two case studies. The first case is a blind source separation problem where features are learned from an artificial signal with known features. We demonstrate that the learned features are qualitatively consistent with the true features. In the second case, features are learned from ball-bearing vibration data. We find that vibration signals from bearings with faults have characteristic features and codes, and that the event-based code enable a reduction of the data rate by at least one order of magnitude.

  • 41.
    Barraza, Sergio Martin Del Campo
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Sandin, Fredrik
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Sparse feature learning for condition monitoring2014Conference paper (Other academic)
  • 42.
    Barraza, Sergio Martin Del Campo
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Sandin, Fredrik
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Towards zero-configuration condition monitoring based on dictionary learning2015In: Proceedings of the 23rd European Signal Processing Conference (EUSIPCO 2015): Aug. 31 2015-Sept. 4 2015, Nice, Piscatataway, NJ: IEEE Communications Society, 2015, 1306-1310 p., 7362595Conference paper (Refereed)
    Abstract [en]

    Condition-based predictive maintenance can significantly improve overall equipment effectiveness provided that appropriate monitoring methods are used. Online condition monitoring systems are customized to each type of machine and need to be reconfigured when conditions change, which is costly and requires expert knowledge. Basic feature extraction methods limited to signal distribution functions and spectra are commonly used, making it difficult to automatically analyze and compare machine conditions. In this paper, we investigate the possibility to automate the condition monitoring process by continuously learning a dictionary of optimized shift-invariant feature vectors using a well-known sparse approximation method. We study how the feature vectors learned from a vibration signal evolve over time when a fault develops within a ball bearing of a rotating machine. We quantify the adaptation rate of learned features and find that this quantity changes significantly in the transitions between normal and faulty states of operation of the ball bearing.

  • 43.
    Beckman, Claes
    et al.
    Department of Communications systems, School of ICT, Royal Institute of Technology, Kista.
    Borg, Johan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Johansson, Jonny
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Tecsor, Irina
    Department of Communications systems, School of ICT, Royal Institute of Technology, Kista.
    Design considerations for the EISCAT-3D phased array antenna2014In: 2014 8th European Conference on Antennas and Propagation: (EuCAP); The Hague; Netherlands, 6 -11 April 2014, Piscataway, NJ: IEEE Communications Society, 2014, 1700-1704 p.Conference paper (Refereed)
    Abstract [en]

    This paper presents a background and an overview of the initial design considerations for phased array antenna being designed for the New Generation multi-static, incoherent-scatter radar station - EISCAT-3D - in Northern Scandinavia. Its anticipated electrical, mechanical and environmental design requirements are given both by the physics as well as by the extreme climate in the subarctic region of northern Scandinavia

  • 44.
    Berglund, Tomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Estimating geometric primitives using 3D range data1999Report (Other academic)
    Abstract [en]

    Master's Thesis at the Department of Mathematics and at the Division of Robotics at the Department of Computer Science and Electrical Engineering, Luleå University of Technology, Sweden

  • 45.
    Berglund, Tomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Path-planning with obstacle-avoiding minimum curvature variation B-splines2003Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    We study the general problem of computing an obstacle-avoiding path that, for a prescribed weight, minimizes the weighted sum of a smoothness measure and a safety measure of the path. We consider planar curvature-continuous paths, that are functions on an interval of a room axis, for a point-size vehicle amidst obstacles. The obstacles are two disjoint continuous functions on the same interval. A path is found as a minimizer of the weighted sum of two costs, namely 1) the integral of the square of arc- length derivative of curvature along the path (smoothness), and 2) the distance in L2 norm between the path and the point-wise arithmetic mean of the obstacles (safety). We formulate a variant of this problem in which we restrict the path to be a B-spline function and the obstacles to be piece-wise linear functions. Through implementations, we demonstrate that it is possible to compute paths, for different choices of weights, and use them in practical industrial applications, in our case for use by the ore transport vehicles operated by the Swedish mining company Luossavaara-Kiirunavaara AB (LKAB). Assuming that the constraint set is non-empty, we show that, if only safety is considered, this problem is trivially solved. We also show that properties of the problem, for an arbitrary weight, can be studied by investigating the problem when only smoothness is considered. The uniqueness of the solution is studied by the convexity properties of the problem. We prove that the convexity properties of the problem are preserved due to a scaling and translation of the knot sequence defining the B-spline. Furthermore, we prove that a convexity investigation of the problem amounts to investigating the convexity properties of an unconstrained variant of the problem. An empirical investigation of the problem indicates that it has one unique solution. When only smoothness is considered, the approximation properties of a B-spline solution are investigated. We prove that, if there exists a sequence of B-spline minimizers that converge to a path as the number of B-spline basis functions tends to infinity, then this path is a solution to the general problem. We provide an example of such a converging sequence.

  • 46.
    Berglund, Tomas
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Erikson, Ulf
    Luleå tekniska universitet.
    Jonsson, Håkan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Mrozek, Kent
    Navigator AB.
    Söderkvist, Inge
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Automatic generation of smooth paths bounded by polygonal chains2001In: CIMCA 2001: 2001 international conference on computational intelligence for modelling, control & automation : 9-11 July 2001, Las Vegas, Nevada, USA : proceedings / [ed] M. Mohammadian, CIMCA , 2001, 528-535 p.Conference paper (Refereed)
  • 47.
    Berglund, Tomas
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Greppe, Anders
    Thorén, Johan
    Papp, John
    Curve and surface fitting to measured data with a B-spline approach1999Report (Other academic)
    Abstract [en]

    Report in the Project course in Mathematics, MAM088, 1998/1999. Department of Mathematics, Luleå University of Technology, Sweden

  • 48.
    Berglund, Tomas
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Jonsson, Håkan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Söderkvist, Inge
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    The problem of computing an obstacle-avoiding minimum variation B-spline2003Report (Other academic)
    Abstract [en]

    We study the problem of computing a planar curve restricted to lie between two given polygonal chains such that the integral of the square of arc- length derivative of curvature along the curve is minimized. We introduce the Minimum Variation B-spline problem which is a linearly constrained optimization problem over curves defined by B-spline functions only. An empirical investigation indicates that this problem has one unique solution among all uniform quartic B-spline functions. Furthermore, we prove that, for any B-spline function, the convexity properties of the problem are preserved subject to a scaling and translation of the knot sequence defining the B-spline.

  • 49.
    Berglund, Tomas
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Synnergren, Per
    Luleå tekniska universitet.
    Söderkvist, Inge
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Estimation of curl in paper: an industrial application combining shape measurement and least squares modeling2000In: Proceedings / International Conference on Trends in Optical Nondestructive Testing: Lugano, Switzerland, May 3-6, 2000 / [ed] Pramod K. Rastogi; D. Inaudi, Lugano: Ecole Polytechnique Fédérale de Lausanne , 2000, 23-33 p.Conference paper (Refereed)
    Abstract [en]

    If a sheet of paper is subjected to humidity changes and have structural variations through its thickness such as gradients of fibre orientation, density and filler content, the sheet will curl and hence assume a cylindrical shape. Curl is a quality problem that makes the paper less suitable for printing. We propose a method to measure curl that can be used for automated analysis of the paper quality. The shape of the curled paper is measured from the perspective difference in a stereoscopic camera system, which is viewing an irregular pattern that is projected onto the specimen. The perspective difference is calculated by a correlation algorithm, a technique often referred to as digital speckle photography. The most interesting quality parameters are the magnitude of curl, which is defined as the inverse of the radius of curvature and also the orientation of the curled paper. These parameters are estimated by performing a least squares fit of a cylindrical shape to the three-dimension...

  • 50. Bernhart, Martin
    et al.
    Bonvicino, Valentino
    Boschan, Eva
    Brotzenberger, Heinz
    Delsing, Jerker
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Dewert, Francis
    Futukawa, Michio
    Rosmalen, Renée Janssen van
    Kapor, Slobodan
    Mounce, Richard
    Serracanta, Francisco
    Vercamer, Pascal
    Approach to the management of contaminated gas sites1997In: Proceedings World Gas Conference 1997, World Gas Union , 1997Conference paper (Refereed)
1234567 1 - 50 of 800
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