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  • 1.
    Abid, Fahim
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Busatto, Tatiano
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rönnberg, Sarah
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Intermodulation due to interaction of photovoltaic inverter and electric vehicle at supraharmonic range2016In: 2016 17th International Conference on Harmonics and Quality of Power, Piscataway. NJ, 2016, p. 685-690, article id 7783471Conference paper (Refereed)
    Abstract [en]

    Advent of power electronic switching is introducing more and more non-linear loads in the low voltage grid. Besides harmonic current generation in the frequency range below 2 kHz, these non-linear loads are also responsible for current emission in the range of 2 kHz to 150 kHz, commonly known as supraharmonic emission. Supraharmonic currents mainly flow between nearby appliances and heavily influence the overall emission of neighboring devices. This paper presents an analysis of supraharmonic interaction between a photovoltaic inverter and an electric vehicle. It has been noticed that intermodulation distortion arises as a result of interaction between different switching frequencies used by the devices. Later, additional household equipment were added to photovoltaic and electric vehicle to observe their effect on intermodulation distortion. All the measurements were conducted in a controlled laboratory environment imitating a domestic customer.

  • 2.
    Abrahamsson, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Optimal drift och dimensionering avbanmatningssystem: Slutrapport Elektraprojekt2016Report (Other academic)
  • 3.
    Abrahamsson, Lars
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Belea, Radu
    Atkins Sverige AB.
    Klerfors, Bertil
    Chalmers Technical University.
    Schütte, Thorsten
    STRI AB.
    Warner, Bruce
    ABB Switzerland Ltd.
    Modern methods for balancing of single phase loads when feeding a.c. Electrified railways2017In: Eb - Elektrische Bahnen, ISSN 0013-5437, Vol. 115, no 6-7, p. 378-384Article in journal (Refereed)
    Abstract [en]

    Conventional compensation circuits for phase balancing of single phase AC railways for 50 or 60 Hz have high cost for the associated transformers. A new version of the classical Steinmetz scheme, using three single phase transformers connected as a W with the phase angles -60°, 0° and +60°, can reuse the two standard single phase transformers of a V-connected feeding station with a third identical transformer added. Power factor compensation can easily be included. For neutral sections between different feeding systems, a neutral section converter is proposed

  • 4.
    Ackeby, Susanne
    et al.
    STRI AB.
    Ohlsson, Lars
    Falbygdens Energi AB.
    Etherden, Nicholas
    STRI.
    Regulatory Aspects of Energy Storage in Sweden2013Conference paper (Refereed)
    Abstract [en]

    This paper highlights the possibilities and limitations of investing in energy storage for use at distribution level under the existing regulatory framework in Sweden. The paper further gives a brief overview of possible applications and ownership models for energy storage in a distribution grid. It was concluded that it is allowed for a network operator to own an energy-storage installation; there are however restrictions in the use of the installation for trade in electricity. A general observation from the study was that there are uncertainties in the interpretation of the laws and regulations due to the complete absence of experience in the use of grid-size energy storage.

  • 5.
    Adjrad, M.
    et al.
    University of Leeds.
    Aguado, L.E.
    Advanced Digital Institute.
    Daly, M.
    University of Leeds.
    Kemp, A.
    University of Leeds.
    Junered, Marcus
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Lindström, J.
    Luleå tekniska universitet.
    Akos, Dennis
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Mangin, F.
    France Developpement Conseil.
    Interference monitoring for GNSS bands in indoor and urban environments2007In: Proceedings of the 20th International Technical Meeting of the Satellite Division of the Institute of Navigation: ION GNSS 2007, Institute of Navigation, The , 2007, Vol. 4, p. 1211-1220Conference paper (Refereed)
    Abstract [en]

    A collaborative research project between the University of Leeds and Luleå University of Technology, Sweden, has taken place aiming to characterize the man-made noise in urban and indoor environments in the Galileo allocated frequency bands: E5 (1191.795 ± 25.575 MHz), E6 (1278.75 ± 20 MHz), and L1 (1575.42 ± 16 MHz), obviously, also covering the GPS L1 and L5 bands. This project has been co-funded by the European GNSS Supervisory Authority (EGSA), with funding from the 6th Framework Program of the European Community for research and technological development. The project includes the development of two receiver systems: the first instrument is based on the use of a spectrum analyzer (SA-based instrument), a wideband GNSS antenna, and a front-end capable of capturing each Galileo band separately using appropriate filtering and switches. The second instrument addresses the issues of cost and portability, providing interference detection and alarm triggering without the need for complex instrument. This is accomplished using low cost components in a small form factor where the instrument is based on a core GNSS front-end. This instrument will only cover the L1/E1 band. The interference measurement is obtained by combining the information from the automatic gain control (AGC) voltage that controls the AGC amplifier gain and the spectrum analysis of the analogue-to-digital converter (ADC) output raw data. The AGC information will be very important for detecting the presence of wideband interference signals where this will be difficult using spectrum analysis (in contrast to the case to narrowband interference signals). Control and data logging from both instruments are performed using a laptop computer where the spectrum analyzer traces and the FE-based instrument data are recorded for offline analysis via a suite of MATLAB® scripts. This paper describes the spectrum survey conducted at various indoor and urban locations, operationally significant to GNSS, in the North of the UK. The survey sites were selected to obtain geographically diverse measurement results and provide a general representation of the spectral environment. In addition, the temporal variation of man-made noise (MMN) is considered, this latter being correlated with the human activity at the measurement site, by performing the measurements day and night, weekdays and weekends.

  • 6.
    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.

  • 7.
    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.

  • 8.
    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.

  • 9.
    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, p. 76-81Conference 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.

  • 10.
    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, p. 174-181Article 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.

  • 11.
    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, p. 199-206Article 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.

  • 12.
    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)
  • 13.
    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.

  • 14.
    Aitomäki, Yvonne
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Online fibre property measurements: foundations for a method based on ultrasound attenuation2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis presents the foundations of a method for estimating fibre properties of pulp suitable for online application in the pulp and paper industry. In the pulp and paper industry, increased efficiency and greater paper quality control are two of the industry's main objectives. It is proposed that online fibre property measurements are a means of achieving progress in both of these objectives. Optical based systems that provide valuable geometric data on the fibres and other pulp characteristics are commercially available. However, measurements of the elastic properties of the fibres are not currently implemented using these systems. To fill this gap an ultrasound based system for measuring the elastic properties of the wood fibres in pulp is proposed. Ultrasound propagation depends on the elastic properties of a solid. Hence attenuation measurements from suspensions of fibres depend on their elastic properties. The method is based on solving the inverse problem where the output is known and the objective is to establish the inputs. In this case, attenuation is measured and a model of attenuation based on ultrasound scattering is developed. A search algorithm is used for finding elastic properties that minimize the error between the model and measured attenuation. The results of the search are estimates of the elastic properties of the fibres in suspension. The results show resonance peaks in the attenuation, in the frequency region tested, for fibres with radii of the order of 10 microns. These peaks are found in both the measured and modelled attenuation spectra. Further investigation of these resonances suggests that they are due to modes of vibration in the fibre where the fibre modelled as an infinitely long cylinder. These resonances are shown to aid in the identification of the elastic properties. The attenuation is found to depend heavily on the geometry of the fibres. Hence fibre geometry, which can be obtained from online optical fibre measurement system, provides the key to extracting the elastic properties from the attenuation signal. Studies are also carried out on the effect of viscosity on attenuation as well as the differences in attenuation between hollow and solid synthetic fibres in suspensions. The measurement method is also applied to hardwood and softwood Kraft pulps. The results of these studies show that using the model derived in the thesis and attenuation measurements, estimates of the elastic properties can be obtained. The elastic property estimates for synthetic fibres agree well with values from other methods. The elastic property estimates for pulps require further validation due to the difficulty in comparing between different testing methods and different types of pulp. The conclusions, based on the work so far and under three realisable conditions, are that the shear modulus and the transverse Young's modulus of pulp fibres can be measured. Once these conditions are met a system based on this method can be implemented. By doing this the industry would benefit from the increase in paper quality control and energy saving such system could provide.

  • 15.
    Aitomäki, Yvonne
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Towards a measurement of paper pulp quality: ultrasonic spectroscopy of fibre suspensions2006Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    For the paper and pulp industry in Sweden and Finland to remain competitive against countries with lower overheads, they have to constantly strive to improve the quality and the efficiency of the manufacturing processes. One of the ways of doing this is to introduce sensors that will provide valuable online feedback on the characteristics of the pulp so that adjustments can be made to optimise the manufacturing process. The measurement method proposed in this thesis is based on ultrasound, since it is rapid, inexpensive, non-destructive and non-intrusive. Thus could be done online. Since ultrasound propagation and attenuation depends on the material properties through which is propagates, it has the potential to provide measurements of material properties such as pulp fibre density and elasticity. The aim of this thesis is to investigate the possibility of using ultrasound to measure pulp fibre material properties. The idea is to solve the inverse problem of estimating these properties from attenuation measurements and to establish the degree of accuracy to which this can be done. Firstly a model is developed and is tested with synthetic fibres to establish is validity. It is then used to solve the inverse problem of estimating material properties from attenuation measurements, again with synthetic fibres, to test the accuracy to which these properties can be estimated. Resonance peaks in the frequency response of the attenuation were found. On closer investigation it was established that the location of these peaks in the frequency domain is sensitive to the diameter of the fibres and their material properties. If the diameter is known, these peaks improve the accuracy of the estimation process. The results of the estimation process for synthetic fibre suspensions show values for the shear modulus are within known ranges but the estimation of Poisson's ratio and Young's modulus is poor. Improving the model or the estimation procedure may lead to better results. For the method as it is to have application in the paper and pulp industry there are certain conditions that need to be fulfilled. These are that we find peaks in the frequency response of the attenuation in pulp, know the diameter distribution of the fibres and the hollow nature of the fibres does not significantly alter the results. We can then, potentially, be able to establish the shear modulus of the pulp fibres. If the shear modulus is a factor in paper quality, we may be close to an online measurement of paper pulp quality using ultrasonic spectroscopy. Improving the model may allow us to estimate further properties and take into account the fibres being hollow. The thesis consists of two parts. The first part includes an overview of the pulp and paper industry and current testing methods, background theory on which the model is based and an overview of the model that is used in predicting ultrasound attenuation. There then follows a summary of the work done, some addition points are raised in the discussion before drawing conclusions. Finally we discuss what needs to be done to take this further. The second part contains a collection of four papers describing the research.

  • 16.
    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, p. 122-, article id 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.

  • 17. 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, p. 250-259Conference 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.

  • 18. 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, p. 432-437Article 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.

  • 19.
    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.

  • 20.
    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, p. 1424-1434Article 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.

  • 21.
    Akos, Dennis
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Ene, A.
    Stanford University.
    Thor, Jonas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    A prototyping platform for multi-frequency GNSS receivers2003In: ION GPS/GNSS Proceedings, Institute of Navigation, The , 2003Conference paper (Refereed)
    Abstract [en]

    The future satellite positioning/navigation systems (i.e. GPS and Galileo) will provide civil signals on multiple frequencies, similar to those currently available for military purposes only. This paper presents a direct RF sampling front end design well suited for multiple frequency satellite navigation receiver design. No frequency downconversion is necessary; rather the particular frequency bands of interest are intentionally aliased using a wide band analog-to-digital converter (ADC). The resulting samples are passed to the memory space of a host PC for storage, and are saved to disk for eventual processing of the multiple frequency transmissions. The present paper describes the design of the front-end, validates its concept with collected data, and discusses the variations on the design of a generic multiple frequency GPS front end. Methods for processing the data obtained by the front end design are also presented.

  • 22.
    Akos, Dennis
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    From, Markus
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Karlsson, Mattias
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Larsson, Kjell
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Receiver measured time in the VDL mode 4 system2000In: IEEE 2000 Position Location and Navigation Symposium: San Diego, California, March 13 - 16, 2000, Piscataway, NJ: IEEE Communications Society, 2000, p. 309-316Conference paper (Refereed)
    Abstract [en]

    This paper details an investigation into the receiver measured time (RMT) concept of VDL Mode 4, basically the ability to derive estimates of time from the transmission of the VDL Mode 4 signals themselves. The RMT concept is based on determining the accurate time of transmission by measuring the time of arrival (TOA) of a received signal. The reverse aspect, or that of user position, can also be computed in the same manner and all computed simulations hold for errors in position. If synchronized time is available, or can be derived, then the user position can be computed based on signals from known transmitter locations. A complete, end-to-end RMT simulation model for the Gaussian filtered frequency shift keying (GFSK) and differential 8-phase shift keying (D8PSK) modulation techniques has been developed in which various transmitters, channels and receiver models as well as an RMT measurement system have been included. The timing results, which are included, are described in terms of two-sigma errors as a function of signal-to-noise ratios (SNRs). The performance varies for the different receiver structures over the typical operation region and for a 1-bit differential GFSK detector the two-sigma error is as low as 0.40 microseconds, corresponding to a ranging error of approximately 120 meters. When incorporating co-channel interference (CCI), multipath and Doppler frequency shifts the RMT performance has been shown to decrease in terms of higher two-sigma errors

  • 23.
    Akos, Dennis
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Stockmaster, Michael
    Rockwell Collins, Cedar Wells.
    Tsui, James B.Y.
    Wright-Patterson Air Force Base, Dayton.
    Caschera, Joe
    Wright-Patterson Air Force Base, Dayton.
    Direct bandpass sampling of multiple distinct RF signals1999In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 47, no 7, p. 983-988Article in journal (Refereed)
    Abstract [en]

    A goal in the software radio design philosophy is to place the analog-to-digital converter as near the antenna as possible. This objective has been demonstrated for the case of a single input signal. Bandpass sampling has been applied to downconvert, or intentionally alias, the information bandwidth of a radio frequency (RF) signal to a desired intermediate frequency. The design of the software radio becomes more interesting when two or more distinct signals are received. The traditional approach for multiple signals would be to bandpass sample a continuous span of spectrum containing all the desired signals. The disadvantage with this approach is that the sampling rate and associated discrete processing rate are based on the span of spectrum as opposed to the information bandwidths of the signals of interest. Proposed here is a technique to determine the absolute minimum sampling frequency for direct digitization of multiple, nonadjacent, frequency bands. The entire process is based on the calculation of a single parameter-the sampling frequency. The result is a simple, yet elegant, front-end design for the reception and bandpass sampling of multiple RF signals. Experimental results using RF transmissions from the US Global Positioning System-Standard Position Service (GPS-SPS) and the Russian Global Navigation Satellite System (GLONASS) are used to illustrate and verify the theory

  • 24.
    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), 2017, article id 7991959Conference 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.

  • 25.
    Alepuz, Javier Pérez
    et al.
    University of Alicante.
    Emami, Reza
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Pomares, Jorge
    University of Alicante.
    Direct image-based visual servoing of free-floating space manipulators2016In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 55, p. 1-9Article in journal (Refereed)
    Abstract [en]

    This paper presents an image-based controller to perform the guidance of a free-floating robot manipulator. The manipulator has an eye-in-hand camera system, and is attached to a base satellite. The base is completely free and floating in space with no attitude control, and thus, freely reacting to the movements of the robot manipulator attached to it. The proposed image-based approach uses the system's kinematics and dynamics model, not only to achieve a desired location with respect to an observed object in space, but also to follow a desired trajectory with respect to the object. To do this, the paper presents an optimal control approach to guiding the free-floating satellite-mounted robot, using visual information and considering the optimization of the motor commands with respect to a specified metric along with chaos compensation. The proposed controller is applied to the visual control of a four-degree-of-freedom robot manipulator in different scenarios.

  • 26.
    Alfieri, Luisa
    et al.
    Department of Engineering, University of Naples Parthenope, Centro Direzionale of Naples.
    Bracale, Antonio
    Department of Engineering, University of Naples Parthenope, Centro Direzionale of Naples.
    Carpinelli, Guido
    Department of Electrical Engineering and Information Technology, University of Naples Federico II.
    Larsson, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Accurate assessment of waveform distortions up to 150 kHz due to fluorescent lamps2017In: 2017 6th International Conference on Clean Electrical Power: Renewable Energy Resources Impact, ICCEP 2017, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 636-644, article id 8004756Conference paper (Refereed)
    Abstract [en]

    Fluorescent lamps are among the most diffuse electrical components that introduce significant waveform distortions in low voltage distribution systems. These distortions involve a wide range of frequencies (i.e., from 0 kHz to 150 kHz), and spectral components characterized by a non-uniform behavior in time and frequency domains. Early IEC standards covered formally only the range from 0 kHz to 9 kHz, defining grouping and group total harmonic distortion both for the low-frequencies (i.e., from 0 kHz to 2 kHz) and for frequencies ranging from 2 kHz to 9 kHz. Recently, the IEC standards have suggested to extend the grouping, previously defined for the range from 2 kHz to 9 kHz, also to the range from 9 kHz to 150 kHz. In this paper, the waveform distortions of a variable number of fluorescent lamps were quantified by applying the main Power Quality indices currently available for such devices. Indices are evaluated using both the IEC method and an hybrid method proposed recently in the relevant literature, i.e., the sliding-window Wavelet-Modified ESPRIT method. Numerical applications on measured data show the waveform distortion levels versus the number of lamps, quantifying also the different performances of the aforesaid spectral analysis methods

  • 27.
    Alfieri, Luisa
    et al.
    Department of Electrical Engineering and Information Technology, University of Naples Federico II, Italy.
    Bracale, Antonio
    Department of Engineering, University of Naples Parthenope, Centro Direzionale of Naples.
    Larsson, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    New Power Quality Indices for the Assessment of Waveform Distortions from 0 to 150 kHz in Power Systems with Renewable Generation and Modern Non-Linear Loads2017In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 10, no 10, article id 1633Article in journal (Refereed)
    Abstract [en]

    The widespread use of power electronics converters, e.g., to interface renewable generation systems with the grid or to supply some high-efficiency loads, has caused increased levels of waveform distortions in the modern distribution system. Voltage and current waveforms include spectral components from 0 kHz to 150 kHz, characterized by a non-uniform time-frequency behavior. This wide interval of frequencies is currently divided into "low-frequency" (from 0 kHz to 2 kHz) and "high-frequency" (from 2 kHz to 150 kHz). While the low-frequencies have been exhaustively investigated in the relevant literature and are covered by adequate standardization, studies for the high-frequencies have been addressed only in the last decade to fill current regulatory gaps. In this paper, new power quality (PQ) indices for the assessment of waveform distortions from 0 kHz to 150 kHz are proposed. Specifically, some currently available indices have been properly modified in order to extend their application also to wide-spectrum waveforms. In the particular case of waveform distortions due to renewable generation, numerical applications prove that the proposed indices are useful tools for the characterization of problems (e.g., overheating, equipment malfunctioning, losses due to skin effects, hysteresis losses or eddy current losses) in cases of both low-frequency and high-frequency distortions

  • 28. 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, article id 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.

  • 29.
    Alvarez, Manuel
    et al.
    Universidad Simón Bolívar, Caracas.
    Bermúdez, Juan
    Universidad Simón Bolívar, Caracas.
    Marginal pricing via penalty factors in the Venezuelan hydrothermal system2006In: 2006 IEEE PES Transmission and Distribution Conference and Exposition: Latin America, TDC'06, Piscataway, NJ: IEEE Communications Society, 2006, article id 4104756Conference paper (Refereed)
    Abstract [en]

    The work shown next deals with the definition of nodal marginal prices, in the context of an economic dispatch solution with transmission losses. The losses are incorporated through penalty factors obtained from line distribution factors, using a linearization process. This study is applied to the hydrothermal venezuelan system, considering plants with regulation capability and run-of-river dams. The objective function to be minimized includes present and future thermal costs. In addition, a discussion is given about the correct location of the slack node, in order to get similar results to these associated to an OPF solution. © 2006 IEEE.

  • 30.
    Alvarez, Manuel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rönnberg, Sarah
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Zhong, Jin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Gil-de-Castro, Aurora
    University of Cordoba, Electronics and Electronic Technology Area, University of Cordoba.
    A Smart Distribution Toolbox for Distribution System Planning2015Conference paper (Refereed)
    Abstract [en]

    The distribution system planner should be able to coordinate smart grid solutions in order to find cost effective expansions plans. These plans should be able to deal with new added system uncertainties from renewable production and consumers while guaranteeing power quality and availability of supply. This paper proposes a structure for distribution systems planning oriented to help the planner in deciding how to make use of smart solutions for achieving the described task. Here, the concept of a system planning toolbox is introduced and supported with a review of relevant works implementing smart solutions. These are colligated in a way that the system planner can foresee what to expect with their combined implementation. Future developments in this subject should attempt to theorize a practical algorithm in an optimization and decision making context.

  • 31.
    Alvarez Perez, Manuel Alejandro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Stochastic Planning of Smart Electricity Distribution Networks2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The penetration of intermittent Distributed Generation (DG) brought additional uncertainty to the system operation and planning. To cope with uncertainties the Distribution System Operator (DSO) could implement several strategies. These strategies range from the inclusion of smart technologies which will increment system’s flexibility and resiliency, to improvements in forecasting, modeling, and regulatory pledge that will facilitate the planning activity. Regardless of the nature of the solutions, they could be collected in a sort of toolbox. The planner will access the toolbox to conform cost effective plans, better able to deal with any uncertainty. The present work will address the problem of distribution system planning under uncertainties, considering smart solutions along with traditional reinforcements, in the short-term lead time up to 3 years ahead. The work will be focused on three aspects that are the cornerstones of this work:

     • A planning facilitating strategy: Distribution Capacity Contracts (DCCs).

     • A flexibility enabler technology: Energy Storage.

     • A binding methodology: Multistage Stochastic Programming. Stochastic dual dynamic programming (SDDP). 

    Under the present directive of the European Parliament concerning common rules for the internal market in electricity, distribution companies are not allowed to own DG but entitled to include it as a planning option to differ investment in traditional grid reinforcements. An evaluation of the regulatory context will lead this work to consider DCCs as a planning alternative available in the toolbox. The impact of this type of contract on the remuneration of the DG owner will be assessed in order to provide insight on its willingness to participate. The DCCs might aid the DSO to defer grid i ii investments during planning stages and to control the network flows during operation. 

    Given that storage solutions help to match in time production from intermittent sources with load consumption, they will play a major role in dealing with uncertainties. A generic storage model (GSM) based on a future cost piecewise approximation will be developed. This model inspired by hydro-reservoirs will help assessing the impact of storage in planning decisions. This model will be tested by implementing it in short-term hydro scheduling and unit commitment studies. 

    To trace a path towards the future of this research work, a discussion on the planning problem formulation, under consideration of the lead time, the expansion options, the smart strategies, and the regulatory framework will be presented. Special focus will be given to multistage stochastic programming methods and in particular to the SDDP approach.

  • 32.
    Alvarez Perez, Manuel Alejandro
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rönnberg, Sarah
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bermúdez, Juan
    Universidad Simón Bolívar.
    Zhong, Jin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. The University of Hong Kong.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    A Generic Storage Model Based on a Future Cost Piecewise-Linear Approximation2017In: IEEE Transactions on Smart Grid, ISSN 1949-3053, E-ISSN 1949-3061Article in journal (Refereed)
    Abstract [en]

    This work presents a generic storage model (GSM) inspired by the scheduling of hydraulic reservoirs. The model for steady state short-term (ST) operational studies interlaces with the long-term (LT) energy scheduling through a piecewise-linear Future Cost Function (FCF). Under the assumption that a Stochastic Dual Dynamic Programming (SDDP) approach has been used to solve the energy schedule for the LT, the FCF output from that study will be processed to obtain an equivalent marginal opportunity cost for the storage unit. The linear characteristic of a segment of the future cost function (FCF) will allow a linear modeling of the storage unit production cost. This formulation will help to coordinate the renewable resource along with storage facilities in order to find the optimal operation cost while meeting end-point conditions for the long-term plan of the energy storage. The generic model will be implemented to represent a battery storage and a pumped-hydro storage. A stochastic unit commitment (SUC) with the GSM will be formulated and tested to assess the day-ahead scheduling strategy of a Virtual Power Plant (VPP) facing uncertainties from production, consumption, and market prices.

  • 33.
    Alvarez Perez, Manuel Alejandro
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rönnberg, Sarah
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bermúdez, Juan
    Universidad Simón Bolívar.
    Zhong, Jin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    A Hydro-Reservoir Generic Storage Model for Short-Term Hydrothermal Coordination2017In: IEEE PES PowerTech Manchester 2017: towards and beyond sustainable energy systems, 2017, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2017, article id 7980882Conference paper (Refereed)
    Abstract [en]

    This work presents a linear solution for the short-term hydro-thermal scheduling problem linked to long-term conditions through a piecewise-linear Future Cost Function (FCF). Given end-point conditions to conform long-term water releases, and given actual reservoir conditions, a segment of a pre-built piecewise future cost function will be chosen. The linear characteristic of the FCF segment will allow a linear modeling of the hydro-power plant, in a similar fashion as a thermal unit with an equivalent marginal opportunity cost. A short-term hydro thermal coordination problem will be formulated considering parallel and cascaded hydro-reservoirs. Three study cases involving different reservoir configurations and scenarios will be computed to test the model. The results of this model mimics coherently the future-cost hydro-thermal coordination problem for the different configurations tested. Given similarities with other forms of energy storage, a new theoretical model for generic storage will be proposed and discussed.

  • 34.
    Alvarez Perez, Manuel Alejandro
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rönnberg, Sarah
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bermúdez, Juan
    Department of Energy Conversion and Transport, Simón Bolívar University.
    Zhong, Jin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Reservoir-Type Hydropower Equivalent Model Based on a Future Cost Piecewise Approximation2018In: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 155, p. 184-195Article in journal (Refereed)
    Abstract [en]

    The long-term (LT) scheduling of reservoir-type hydropower plants is a multistage stochastic dynamic problem that has been traditionally solved using the stochastic dual dynamic programming (SDDP) approach. This LT schedule of releases should be met through short-term (ST) scheduling decisions obtained from a hydro-thermal scheduling that considers uncertainties. Both time scales can be linked if the ST problem considers as input the future cost function (FCF) obtained from LT studies. Known the piecewise-linear FCF, the hydro-scheduling can be solved as a one-stage problem. Under certain considerations a single segment of the FCF can be used to solve the schedule. From this formulation an equivalent model for the hydropower plant can be derived and used in ST studies. This model behaves accordingly to LT conditions to be met, and provides a marginal cost for dispatching the plant. A generation company (GENCO) owning a mix of hydro, wind, and thermal power will be the subject of study where the model will be implemented. The GENCO faces the problem of scheduling the hydraulic resource under uncertainties from e.g. wind and load while determining the market bids that maximize its profit under uncertainties from market prices. A two-stage stochastic unit commitment (SUC) for the ST scheduling implementing the equivalent hydro model will be solved.

  • 35.
    Alvarez Perez, Manuel Alejandro
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rönnberg, Sarah
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Cossent, Rafael
    Universidad Pontificia de Comillas.
    Zhong, Jin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Regulatory Matters Affecting Distribution Planning With Distributed Generation2017In: CIRED - Open Access Proceedings Journal, E-ISSN 2515-0855, Vol. 2017, no 1, p. 2869-2873Article in journal (Refereed)
    Abstract [en]

    Under the present European directive concerning common rules for the internal market in electricity, distribution companies are not allowed to own distributed generation (DG) but encouraged to include it as a planning option to defer investment in traditional grid reinforcements. Distribution system operators (DSOs) have used the provision of capacity contracted to DG as a viable alternative under current regulatory arrangements. Here, the topics bonding DSOs and DG owners under the present regulation will be explored and a planning structure that considers distribution capacity contracts as a planning option will be proposed. This will serve as a road map for DSOs to implement its preferred planning tools in an optimisation context, considering costs of investment, reliability, operation, and capacity provision while complying with current regulation.

  • 36.
    Alvarez Perez, Manuel Alejandro
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rönnberg, Sarah
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Cossent, Rafael
    Universidad Pontificia de Comillas.
    Zhong, Jin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Remuneration Assessment of a VPP Providing Distribution Capacity Services2017In: IEEE PES PowerTech Manchester 2017: towards and beyond sustainable energy systems, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2017, article id 7980881Conference paper (Refereed)
    Abstract [en]

    A Distribution System Operator (DSO) might consider a capacity contract as a planning alternative to defer grid investments. A Virtual Power Plant (VPP) might be able to provide such capacity and change its production as requested by the DSO. This article presents an assessment of the impact of this type of distribution capacity contract (DCC) on VPP's remuneration. This assessment is done by comparing the optimal production / bidding strategy which maximize its profit, under presence or absence of these contracts. The impact of intermittent generation and storage while evaluating these scenarios will be investigated as well. A stochastic unit commitment will be used to determine the VPP's strategy under uncertainties from wind power, load, market prices, and the requested power by the DSO. The model showed that the VPP involvement in distribution capacity contracts can improve its remuneration when certain types of Distributed Energy Resources (DER) are used to provide the service.

  • 37.
    Andersson, Marcus
    et al.
    Luleå tekniska universitet.
    Rönnberg, Sarah
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lundmark, Martin
    Larsson, Anders
    Wahlberg, Mats
    Bollen, Math
    Interfering signals and attenuation: potential problems with communication via the power grid2006In: Proceedings of Nordic Distribution and Asset Management Conference: NORDAC 2006, 2006Conference paper (Refereed)
    Abstract [en]

    This paper will give a general overview of the potential problems associated with remote-meter reading via the power grid and describe some of the technologies available. A comparison will be made between the power grid as a communication channel and other, dedicated and shared, channels. Examples will be given of practical cases in which the communication channel does not function in the intended way.

  • 38.
    Andersson, Mathias
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    EMC robot1997Report (Other academic)
  • 39.
    Andersson, Tobias
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Analysis of 3D surface data for on-line determination of the size distribution of iron ore pellet piles on conveyor belt2007Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Size measurement of iron ore pellets in industry is usually performed by manual sampling and sieving techniques. The manual sampling is performed infrequently and is inconsistent, invasive and time-consuming. Iron ore pellet's sizes are critical to the efficiency of the blast furnace process in the production of steel. Overly coarse pellets affect the blast furnace process negatively, however this affect can be minimized by operating the furnace with different parameters. An on-line system for measurement of pellet sizes would improve productivity through fast feedback and efficient control of the blast furnace. Also, fast feedback of pellet sizes would improve pellet quality in pellet production. Image analysis techniques promise a quick, inexpensive, consistent and non-contact solution to determining the size distribution of a pellet pile. Such techniques capture information of the surface of the pellet pile which is then used to infer the pile size distribution. However, there are a number of sources of error relevant to surface analysis techniques. The objective of this thesis is to address and overcome aspects of these sources of error relevant to surface analysis techniques. The research problem is stated as: How can the pellet pile size distribution be estimated with surface analysis techniques using image analysis? This problem is addressed by dividing the problem into sub-problems. The focus of the presented work is to develop techniques to overcome, or minimize, two of these sources of error; overlapped particle error and profile error. Overlapped particle error describes the fact that many pellets on the surface of a pile are only partially visible and a large bias results if they are sized as if they were smaller entirely visible pellets. No other researchers make this determination. Profile error describes the fact that only one side of an entirely visible pellet can be seen making it difficult to estimate pellets size. Statistical classification methods are used to overcome these sources of error. The thesis is divided into two parts. The first part contains an introduction to the research area together with a summary of the contributions, and the second part is a collection of four papers describing the research.

  • 40.
    Andersson, Tobias
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Estimating particle size distributions based on machine vision2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis contributes to the field of machine vision and the theory of the sampling of particulate material on conveyor belts. The objective is to address sources of error relevant to surface-analysis techniques when estimating the sieve-size distribution of particulate material using machine vision. The relevant sources of error are segregation and grouping error, capturing error, profile error, overlapping-particle error and weight-transformation error. Segregation and grouping error describes the tendency of a pile to separate into groups of similarly sized particles, which may bias the results of surface-analysis techniques. Capturing error describes the varying probability, based on size, that a particle will appear on the surface of the pile, which may also bias the results of surface-analysis techniques. Profile error is related to the fact that only one side of an entirely visible particle can be seen, which may bias the estimation of particle size. Overlapping-particle error occurs when many particles are only partially visible, which may bias the estimation of particle size because large particles may be treated as smaller particles. Weight-transformation error arises because the weight of particles in a specific sieve-size class might significantly vary, resulting in incorrect estimates of particle weights. The focus of the thesis is mainly on solutions for minimizing profile error, overlapping-particle error and weight-transformation error.In the aggregates and mining industries, suppliers of particulate materials, such as crushed rock and pelletised iron ore, produce materials for which the particle size is a key differentiating factor in the quality of the material. Manual sampling and sieving techniques are the industry-standard methods for estimating the size distribution of these particles. However, as manual sampling is time consuming, there are long response times before an estimate of the sieve-size distributions is available. Machine-vision techniques promise a non-invasive, frequent and consistent solution for determining the size distribution of particles. Machine-vision techniques capture images of the surfaces of piles, which are analyzed by identifying each particle on the surface of the pile and estimating its size. Sampling particulate material being transported on conveyor belts using machine vision has been an area of active research for over 25 years. However, there are still a number of sources of error in this type of sampling that are not fully understood. To achieve a high accuracy and robustness in the analysis of captured surfaces, detailed experiments were performed in the course of this thesis work, towards the development and validation of techniques for minimizing overlapping-particle error, profile error and weight-transformation error. To minimise overlapping-particle error and profile error, classification algorithms based on logistic regression were proposed. Logistic regression is a statistical classification method that is used for visibility classification to minimize overlapping-particle error and in particle-size classification to minimize profile error. Commonly used size- and shape-measurement methods were evaluated using feature-selection techniques, to find sets of statistically significant features that should be used for the abovementioned classification tasks. Validation using data not used for training showed that these errors can be overcome.The existence of an effect that causes weight-transformation error was identified using statistical analysis of variance (ANOVA). Methods to minimize weight-transformation error are presented herein, and one implementation showed a good correlation between the results using the machine-vision system and manual sieving results.The results presented in this thesis show that by addressing the relevant sources of error, machine vision techniques allow for robust and accurate analysis of particulate material. An industrial prototype was developed that estimates the sieve-size distribution of iron-ore pellets in a pellet plant and crushed limestone in a quarry during ship loading. The industrial prototype also enables product identification of crushed limestone to prevent the loading of incorrectly sized products.

  • 41. Andersson, Tobias
    et al.
    Thurley, Matthew
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Minimizing profile error when estimating the sieve-size distribution of iron ore pellets using ordinal logistic regression2011In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 206, no 3, p. 218-226Article in journal (Refereed)
    Abstract [en]

    Size measurement of pellets in industry is usually performed by manual sampling and sieving techniques. Automatic on-line analysis of pellet size based on image analysis techniques would allow non-invasive, frequent and consistent measurement. We evaluate the statistical significance of the ability of commonly used size and shape measurement methods to discriminate among different sieve-size classes using multivariate techniques. Literature review indicates that earlier works did not perform this analysis and selected a sizing method without evaluating its statistical significance. Backward elimination and forward selection of features are used to select two feature sets that are statistically significant for discriminating among different sieve-size classes of pellets. The diameter of a circle of equivalent area is shown to be the most effective feature based on the forward selection strategy, but an unexpected five-feature classifier is the result using the backward elimination strategy. The discrepancy between the two selected feature sets can be explained by how the selection procedures calculate a feature's significance and that the property of the 3D data provides an orientational bias that favours combination of Feret-box measurements. Size estimates of the surface of a pellet pile using the two feature sets show that the estimated sieve-size distribution follows the known sieve-size distribution.

  • 42.
    Andersson, Tobias
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Thurley, Matthew
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Visibility classification of rocks in piles2008In: Digital Image Computing: Techniques and Applications: DICTA 2008 ; [Conference on Digital Image Computing: Techniques and Applications] ; 1 - 3 December 2008, Canberra, Australia ; proceedings, IEEE Communications Society, 2008, p. 207-213Conference paper (Refereed)
    Abstract [en]

    Size measurement of rocks is usually performed by manual sampling and sieving techniques. Automatic on-line analysis of rock size based on image analysis techniques would allow non-invasive, frequent and consistent measurement. In practical measurement systems based on image analysis techniques, the surface of rock piles will be sampled and therefore contain overlapping rock fragments. It is critical to identify partially visible rock fragments for accurate size measurements. In this research, statistical classification methods are used to discriminate rocks on the surface of a pile between entirely visible and partially visible rocks. The feature visibility ratio is combined with commonly used 2D shape features to evaluate whether 2D shape features can improve classification accuracies to minimize overlapped particle error.

  • 43.
    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, p. 405-411Conference paper (Refereed)
  • 44.
    Anthony, Niklas
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Emami, Reza
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Institute for Aerospace Studies, University of Toronto.
    Asteroid engineering: The state-of-the-art of Near-Earth Asteroids science and technology2018In: Progress in Aerospace Sciences, ISSN 0376-0421, E-ISSN 1873-1724, Vol. 100, p. 1-17Article in journal (Refereed)
    Abstract [en]

    This paper presents a comprehensive review of the science and technology of accessing near-Earth asteroids (NEAs), or making them accessible, for obtaining both information and resources. The survey is divided into four major groups of NEA study, namely a) discovery (population estimation and detection), b) Exploration (identification and characterization), c) deflection and redirection, and d) mining (prospecting, excavation, processing, refining, storage.). Recent research and development advancements from both industry and academia are discussed in each group, and certain specific future directions are highlighted. Some concluding remarks are made at the end, including the need for creating new educational programs to train competent engineers and researchers for the taskforce in the new field of asteroid engineering in near future

  • 45. 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)
  • 46.
    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, p. 39-50Article 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.

  • 47. 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)
  • 48.
    Antonini, Giulio
    et al.
    University of L'Aquila (Italy).
    De Lauretis, Maria
    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.
    Miroshnikova, Elena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    On the passivity of the Delay-Rational Green’s-function-based model for Transmission Lines2018In: Trends in Mathematics, Research Perspectives, 2018Conference paper (Refereed)
  • 49.
    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.

  • 50.
    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, p. 241-244Conference 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.

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