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  • 1.
    Abd Alrahman, Chadi
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Evaluation of a PVT Air Collector2015Independent thesis Advanced level (degree of Master (Two Years)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Hybrid Photovoltaic Thermal (PVT) collectors are an emerging technology that

    combines PV and solar thermal systems in a single solar collector producing heat and

    electricity simultaneously. The focus of this thesis work is to evaluate the performance of

    unglazed open loop PVT air system integrated on a garage roof in Borlänge. As it is

    thought to have a significant potential for preheating ventilation of the building and

    improving the PV modules electrical efficiency. The performance evaluation is important

    to optimize the cooling strategy of the collector in order to enhance its electrical efficiency

    and maximize the production of thermal energy. The evaluation process involves

    monitoring the electrical and thermal energies for a certain period of time and investigating

    the cooling effect on the performance through controlling the air mass flow provided by a

    variable speed fan connected to the collector by an air distribution duct. The distribution

    duct transfers the heated outlet air from the collector to inside the building.

    The PVT air collector consists of 34 Solibro CIGS type PV modules (115 Wp for each

    module) which are roof integrated and have replaced the traditional roof material. The

    collector is oriented toward the south-west with a tilt of 29 ᵒ. The collector consists of 17

    parallel air ducts formed between the PV modules and the insulated roof surface. Each air

    duct has a depth of 0.05 m, length of 2.38 m and width of 2.38 m. The air ducts are

    connected to each other through holes. The monitoring system is based on using T-type

    thermocouples to measure the relevant temperatures, air sensor to measure the air mass

    flow. These parameters are needed to calculate the thermal energy. The monitoring system

    contains also voltage dividers to measure the PV modules voltage and shunt resistance to

    measure the PV current, and AC energy meters which are needed to calculate the

    produced electrical energy. All signals recorded from the thermocouples, voltage dividers

    and shunt resistances are connected to data loggers. The strategy of cooling in this work

    was based on switching the fan on, only when the difference between the air duct

    temperature (under the middle of top of PV column) and the room temperature becomes

    higher than 5 °C. This strategy was effective in term of avoiding high electrical

    consumption by the fan, and it is recommended for further development. The temperature

    difference of 5 °C is the minimum value to compensate the heat losses in the collecting

    duct and distribution duct.

    The PVT air collector has an area of (Ac=32 m2), and air mass flow of 0.002 kg/s m2.

    The nominal output power of the collector is 4 kWppv (34 CIGS modules with 115

    Wppvfor each module). The collector produces thermal output energy of 6.88 kWth/day

    (0.21 kWth/m2 day) and an electrical output energy of 13.46 kWhel/day (0.42 kWhel/m2

    day) with cooling case. The PVT air collector has a daily thermal energy yield of 1.72

    kWhth/kWppv, and a daily PV electrical energy yield of 3.36 kWhel /kWppv. The fan energy

    requirement in this case was 0.18 kWh/day which is very small compared to the electrical

    energy generated by the PV collector. The obtained thermal efficiency was 8 % which is

    small compared to the results reported in literature for PVT air collectors. The small

    thermal efficiency was due to small operating air mass flow. Therefore, the study suggests

    increasing the air mass flow by a factor of 25. The electrical efficiency was fluctuating

    around 14 %, which is higher than the theoretical efficiency of the PV modules, and this

    discrepancy was due to the poor method of recording the solar irradiance in the location.

    Due to shading effect, it was better to use more than one pyranometer.

  • 2.
    Andersson, Jonas
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Intelli-lamp, ett intelligent ljussystem som kommunicerar trådlöst2007Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [sv]

    Interactive Institute’s Power Studio i Eskilstuna har ett projekt som heter AWARE. AWARE är ett designorienterat forskningsprojekt som syftar till att öka människors medvetenhet om hur elenergi används i vardagen, speciellt i hemmen. Målet är att uppmärksamma människor om deras elanvändning samt ge de ett medel att kunna kontrollera och göra deras elanvändning mer effektiv. Som en del i AWARE ska en intelligent bärbar armatur som är batteridriven tas fram som ska få människor att tänka på att elenergi inte är något konstant och outtömligt. Det ska finnas visuella effekter som på ett bra sätt kan väcka dessa tankar. Vid laddning av dessa armaturer kan t.ex. ett svagt pulserande ljus användas för att ge effekten av att armaturen tankas med elenergi. Detta examensarbete bygger på att producera två prototyper av dessa armaturer som kan kommunicera trådlöst med varandra. Examensarbetet resulterade i två stycken fungerande prototyper. Dessa prototyper klarar av att kommunicera och styra varandra och utgör en enkel plattform för vidare utveckling. Med lite mer arbete kommer prototyperna

  • 3.
    Arnberg, Jerker
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Zigbee för längre avstånd2006Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [sv]

    I dag går utvecklingen av trådlösa nätverk snabbt framåt. Zigbee är en helt ny teknik som bygger på IEEE 802-15-4 standarden. Zigbee utvecklades av the Zigbee Alliance som består av en rad stora elektronikföretag. Zigbee är en teknik som inriktar sig på låg energiförbrukning och låg kostnad. Tekniken är tänkt att användas för att ställa in och läsa av sensorer av olika slag. Denna rapport är ett resultat av ett examensarbete som går ut på att utreda om Zigbee tekniken kan användas för lite längre avstånd. Arbetet resulterade i två demoapplikationer för ett enkel zigbee system, och färdigskriven kod för en möjlighet att använda Zigbee för länge avstånd.

  • 4.
    Ashraf, Ali Junaid
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    DC Motor Speed Control via Fuzzy / Pole Placement / PI Controller2010Independent thesis Advanced level (degree of Master (Two Years)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report presents a new way of control engineering. Dc motor speed controlled by three controllers PID, pole placement and Fuzzy controller and discusses the advantages and disadvantages of each controller for different conditions under loaded and unloaded scenarios using software Matlab. The brushless series wound Dc motor is very popular in industrial application and control systems because of the high torque density, high efficiency and small size. First suitable equations are developed for DC motor. PID controller is developed and tuned in order to get faster step response. The simulation results of PID controller provide very good results and the controller is further tuned in order to decrease its overshoot error which is common in PID controllers. Further it is purposed that in industrial environment these controllers are better than others controllers as PID controllers are easy to tuned and cheap. Pole placement controller is the best example of control engineering. An addition of integrator reduced the noise disturbances in pole placement controller and this makes it a good choice for industrial applications. The fuzzy controller is introduce with a DC chopper to make the DC motor speed control smooth and almost no steady state error is observed. Another advantage is achieved in fuzzy controller that the simulations of three different controllers are compared and concluded from the results that Fuzzy controller outperforms to PID controller in terms of steady state error and smooth step response. While Pole placement controller have no comparison in terms of controls because designer can change the step response according to nature of control systems, so this controller provide wide range of control over a system. Poles location change the step response in a sense that if poles are near to origin then step response of motor is fast. Finally a GUI of these three controllers are developed which allow the user to select any controller and change its parameters according to the situation.

  • 5.
    Brännlund, Stig
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Implementering av felprediktering och frekvenshopp i ett 2,4 GHz radiosystem2008Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [sv]

    Maxicap AB är ett företag som utvecklar och tillverkar elektronisk utrustning för bland annat olika mätuppgifter. Målet med detta examensjobb var att undersöka och implementera en stabil trådlös dataöverföringsmetod med den utrustning som Maxicap ville använda. Detta skulle åstadkommas/testas genom att sända temperatursensorvärden trådlöst med Nordic Semiconductor’s sändtagare (eng. transceiver) styrda av Atmel’s mikrokontrollers. Arbetet fokuserade på att få till denna stabila trådlösa överföring genom att implementera frekvenshoppning och datapaketskontroll på datatrafiken inom det fria 2,4 GHz ISM-bandet. All den C-kod som utvecklades i detta arbete är skriven för att vara lättanpassad till flera olika modeller av mikrokontrollers inom Atmel’s produktserie samt att kunna användas till andra liknande projekt. Koden är väldokumenterad med kommentarer vid varje funktionsblock som beskriver vad funktionerna gör och hur de skall användas. Arbetet resulterade i två fungerande prototyper. En enhet känner av temperaturen i luften och skickar sedan detta temperaturvärde trådlöst till enhet nummer två. Detta värde samt några inställningsvärden för mottagaren visas sedan på den enhetens display.

  • 6.
    Edholm, Anders
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Improvements of the ability to foresee raisedConductivity due to expected increase oftemperature in cooling media2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report investigates the possibility to use a different algorithm for predictingthe conductivity [2] in HVDC pure water cooling systems.The study shows that it is possible to use a different algorithm that will raise theaccuracy and reliability significantly.

  • 7.
    Ekholm, Johan
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Utveckling och prov av en 50 kJ elektrisk pulsgenerator2009Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [sv]

    Detta arbete beskriver en elektrisk pulsgenerator, dess konstruktion och ingående komponenter. Särskild uppmärksamhet ägnas åt det triggade gnistgapet och triggpulsgeneratorn. Gnistgapets konstruktion beskrivs. En SPICE-modell utvecklas för gnistgapets urladdningskanal. Urladdningskanalens egenskaper simuleras. Simulerad och fotograferad kanalradie jämförs. Några genomförda försök beskrivs kort, däribland det katastrofala och avslutande försöket. Det avslutande försöket analyseras. Avslutningsvis avhandlas några tänkbara utbyggnader och förbättringar.

  • 8.
    Erik, Nerback
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Stegmotorstyrd rotortilt för användning vid mätning av antenners riktningskaraktäristik2006Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [sv]

    Radioantenner tillverkas med olika egenskaper för att passa olika applikatoner. En av dessa egenskaper är antennens riktningskaraktäristik. Hur antennen skall konstrueras för att få den eftersträvade riktningskaraktäristiken kan beräknas. För att kontrollera att antennens faktiska riktningskaraktäristik överensstämmer med den beräknade kan antennens riktningskaraktäristik mätas. Företaget Detectus AB utvecklar idag ett mätsystem för att mäta antenners riktningskaraktäristik och presentera denna i form av ett tredimensionellt polärdiagram. Rapporten beskriver det examensarbete som genomförts i syfte att utveckla hårdvara med tillhörande styrsystem för mätsystemet. En prototyp för den rotortilt som skall rotera och tilta antennen under mätningen har utvecklats. Till denna rotortilt har också mjukvara för styrning av rotations- och tiltrörelsernas stegmotorer tagits fram. Vidare arbete innefattar att implementera en nödstoppsfunktion samt en referenssökningsfunktion för rotortilten. Vidare arbete innefattar också att utveckla mjukvara för mätsystemet.

  • 9.
    Erkers, Anders
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Avbrottsstyrd hexkodsmonitor: Programmering av Mikroprocessor Philips LPC22922007Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [sv]

    Research Elektronics är ett företag som utvecklar elektroniska system. I sina lösningar använder de bl.a. Siemens C500 Mikroprocessorer. Företaget planerar nu att gå över till Philips LPC 2292 som bygger på en 32-bitars ARM-kärna. Denna mikroprocessor har högre prestanda och är mer kostnadseffektiv. Uppgiften bestod av att göra ett monitorprogram som bl.a. kan ladda in och köra andra program i mikroprocessorn samt undersöka och redigera innehållet i minnen och register. Programmet ska användas till test och utveckling av andra program till den aktuella mikroprocessorn. Tanken med denna monitor är att den ska ha liknande funktion och utseendet som en monitor som Research redan använder för mikroprocessorn Siemens c500 serie, för att dessa ska kunna gå över till att använda den nya mikroprocessorn på samma sätt som den nuvarande. Tanken med programmet är att det ska vara en grund som Research senare ska kunna modifiera och utveckla under deras arbete. Programmet har skrivits i assembler för att programmera nära hårdvaran. Resultatet blev ett program med de funktioner som i förväg var bestämda.

  • 10.
    Faheem, Muhammad
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    A GUI for online presentation of steel and steelmaking ladle temperature data and simulation.2009Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [en]

    Continuous casting is a casting process that produces steel slabs in a continuous manner with steel being poured at the top of the caster and a steel strand emerging from the mould below. Molten steel is transferred from the AOD converter to the caster using a ladle. The ladle is designed to be strong and insulated. Complete insulation is never achieved. Some of the heat is lost to the refractories by convection and conduction. Heat losses by radiation also occur. It is important to know the temperature of the melt during the process. For this reason, an online model was previously developed to simulate the steel and ladle wall temperatures during the ladle cycle. The model was developed as an ODE based model using grey box modeling technique. The model’s performance was acceptable and needed to be presented in a user friendly way. The aim of this thesis work was basically to design a GUI that presents steel and ladle wall temperatures calculated by the model and also allow the user to make adjustments to the model. This thesis work also discusses the sensitivity analysis of different parameters involved and their effects on different temperature estimations.

  • 11.
    Göransson, Åke
    et al.
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Sohlberg, Björn
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Tracking Low Velocity Vehicles from Radar Measurements2003In: Proceedings of the IASTED International Conference Circuits, Signals and Systems, Cancun, Mexico, 2003Conference paper (Refereed)
  • 12.
    Ismail, Furrukh
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Photovoltaic Process Development and innovative Techniques2011Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Photovoltaic processing is one of the processes that have significance in semiconductor process line. It is complicated due to the no. of elements involved that directly or indirectly affect the processing and final yield. So mathematically or empirically we can’t say assertively about the results specially related with diffusion, antireflective coating and impurity poisoning. Here I have experimented and collected data on the mono-crystal silicon wafers with varying properties and outputs. Then by using neural network with available experimental data output required can be estimated which is further tested by the test data for authenticity. One can say that it’s a kind of process simulation with varying input of raw wafers to get desired yield of photovoltaic mono-crystal cells.

  • 13.
    Jaramillo Cantu, Hector
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Alphanumeric LCD infrared control via computer’s parallel port2006Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    The present work will explain a method to achieve a remote controlled (via IR LED) alphanumeric Liquid Crystal Display. In modern times, the remote access of different devices has become quite popular, therefore, the aim of this project is to provide a useful tool that will integrate common and easy to access devices. The system includes a C language based user interface, an assembly language code for the AT89C51ED2 microcontroller instructions and some digital electronic circuits needed for the driving and control of both the LCD and the infrared communication, as well as the PC with a parallel port. The interaction of all the devices provides a whole system that can be helpful in different applications, or it can be separated into each one of its different stages to take the best advantage as possible.

  • 14.
    Karim, Sanaz
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Open Issues in Control of Automotive R744 Air-Conditioning Systems2007Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    In this thesis, one of the current control algorithms for the R744 cycle, which tries to optimize the performance of the system by two SISO control loops, is compared to a cost-effective system with just one actuator. The operation of a key component of this system, a two stage orifice expansion valve is examined in a range of typical climate conditions. One alternative control loop for this system, which has been proposed by Behr group, is also scrutinized. The simulation results affirm the preference of using two control-loops instead of one loop, but refute advantages of the Behr alternate control approach against one-loop control. As far as the economic considerations of the A/C unit are concerned, using a two-stage orifice expansion valve is desired by the automotive industry, thus based on the experiment results, an improved logic for control of this system is proposed. In the second part, it is investigated whether the one-actuator control approach is applicable to a system consisting of two parallel evaporators to allow passengers to control different climate zones. The simulation results show that in the case of using a two-stage orifice valve for the front evaporator and a fixed expansion valve for the rear one, a proper distribution of the cooling power between the front and rear compartment is possible for a broad range of climate conditions.

  • 15.
    Nordpers, Lars-Göran
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Simuleringsverktyg som hjälpmedel vid optimering av signalavstånd inom järnväg: Simulation tool as a help for optimization of signal distances on a railway track2006Independent thesis Basic level (degree of Bachelor)Student thesis
  • 16.
    Persson, Tanja
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Analys av den elektriska fältbild som omger genomföringen SMART GOB 750.2015Independent thesis Basic level (degree of Bachelor), 10 HE creditsStudent thesis
    Abstract [en]

    ABB Components wants to develop a bushing that is based on a new technology

    called SMART. The purpose of the new bushing is to reduce the cost of

    materials, warehousing and freight costs. The new technology will change the

    electric field image surrounding the bushing and the electrical field inside the

    capacitor body, which has to be re-examined. Two proposals for capacitor

    bodies was designed and their electric field image analyzed according to the

    design criterias set by ABB Components. The field image for the two proposals

    were subsequently compared with the field image of an existing model, GOB

    750's to see if the field image would be radically altered.

    The simulations indicate that although the field images for the bushings based

    on the new technology looks different compared to the convetional bushing, the

    electric field image is for the most part below the limits set by ABB Components.

    For some of the tests the field strengths are even lower than its predecessor.

    However, there are some simulations that have field strenghts that are above the

    limits which makes it difficult to say if the bushing will pass the voltage levels it

    will be exposed to during its lifetime. The critical simulations can only be verified

    by building a prototype and testing it.

  • 17.
    Pålsson, Rolf
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Studie av subsynkron interaktion (SSTI) mellan ett HVDC system med spänningsstyva strömriktare och en närliggande generator2006Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [sv]

    Syftet med examensarbetet är att studera den subsynkrona interaktionen (subsynchronous torsional interaktion, SSTI) mellan ett HVDC system med spänningsstyva strömriktare och en närliggande generator. Studien utförs med hjälp av datorsimuleringar och fokuserar på att studera dämpkaraktäristiken för SSTI. Studien ska visa hur faktorer såsom den överförda effektens storlek och riktning, vald driftmod och kraftsystemets kortslutningseffekt påverkar dämpkaraktäristiken. Rapporten beskriver subsynkron oscillation (SSO) och tillvägagångssättet vid en SSTI undersökning. En kort introduktion till HVDC Light ges. Studien visar att HVDC Light ökar dämpningen för det frekvensområde som är intressant. Resultaten presenteras som diagram med beräknad dämpkaraktäristik.

  • 18.
    Samuelsson, Pär
    et al.
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Halvarsson, Björn
    Carlsson, Bengt
    Cost-efficent operation of a denitrifying activated sludge process2007In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 41, no 11, p. 2325-2332Article in journal (Refereed)
    Abstract [en]

    In this paper, the choice of optimal set-points and cost minimizing control strategies for the denitrification process in an activated sludge process are treated. In order to compare different criterion functions, simulations utilizing the COST/IWA simulation benchmark are considered. By means of operational maps the results are visualized. It is found that it is easy to distinguish set-point areas where the process can be said to be efficiently controlled in an economic sense. The characteristics of these set-point areas depend on the chosen effluent nitrate set-point as well as the distribution of the different operating costs. It is also discussed how efficient control strategies may be accomplished.

  • 19.
    Samuelsson, Pär
    et al.
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Sohlberg, Björn
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Comparison of Grey-Box ODE Models for Ladle Heat Transfer and Steel Temperature Losses2009In: SteelSim09, 3rd International Conference on Simulation and Modelling of Metallurgical Processes in Steelmaking, Leoben, Österrike, 2009Conference paper (Refereed)
    Abstract [en]

    Most steelmaking ladle modelling strategies are based either on pure physical modelling or statistical relations. In this paper, a relatively simple model for steel temperature and ladle temperatures based on ordinary differential equations is presented and compared with a number of more complex ODE models. The model is semi-physical since the model structure is obtained mainly from physical relations, but the model parameters are calibrated using collected process data and a systematic calibration methodology. A main objective has been to obtain a model suitable for on-line purposes. Different model expansions are compared to the reference model. It is found that a simple model structure gives a good trade off between accuracy and complexity.

  • 20.
    Samuelsson, Pär
    et al.
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Sohlberg, Björn
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Modelling Heat Transfer in Multilayered Ladles: a survey2007In: Proceedings / 2nd International Conference of Simulation and Modelling of Metallurgical Processes in Steelmaking, Steelsim 2007 / [ed] Ludwig, Andreas, Graz, 2007Conference paper (Refereed)
  • 21.
    Samuelsson, Pär
    et al.
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Sohlberg, Björn
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    ODE-based modelling and calibration of temperatures in steelmaking ladles2010In: IEEE Transactions on Control Systems Technology, ISSN 1063-6536, E-ISSN 1558-0865, Vol. 18, no 2, p. 474-479Article in journal (Refereed)
    Abstract [en]

    This brief considers modelling of steel and wall temperatures in steelmaking ladles used as liquid steel transportation vessels. Two measurement campaigns in order to collect data for model calibration and validation were conducted at the facilities of a Swedish stainless steel manufacturer. The process data were utilized in order to calibrate and validate an ordinary differential equation (ODE) model using a grey-box approach. The grey-box approach is justified since model structure and parameters are only partially known and few data are available for calibration. It is concluded that even though the model structure is non-complicated, the model shows promising accuracy for the steel temperature estimation. The model will be further evaluated in online simulations at the steel mill.

  • 22.
    Samuelsson, Pär
    et al.
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Sohlberg, Björn
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    On-line Simulation of Heat Transfer Models for Steelmaking Ladles Using ODE Model2009In: Proceedings of Steelsim 2009, Leoben, Österrike, 2009Conference paper (Refereed)
    Abstract [en]

    This paper describes the on-line implementation and evaluation of a model describing heat transfer in steelmaking ladles. The implemented model is based on ordinary differential equations which ensures a short computation time. Model calibration was performed utilizing a grey-box approach using real process data in order to describe the specific ladles used by a Swedish steel manufacturer. The main purpose has been to design and implement a simulation prototype for on-line simulation in the steel mill. To evaluate the model and the implementation, simulation of 14 steel charges was performed in real-time in the steel mill. Further evaluation of different models and different conditions is needed, although the performed experiment seems promising.

  • 23.
    Samuelssona, Pär
    et al.
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Halvarsson, Bjorn
    Carlsson, Bengt
    Cost-efficient operation of a denitrifying activated sludge process2007In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 41, no 11, p. 2325-2332Article in journal (Refereed)
    Abstract [en]

    In this paper, the choice of optimal set-points and cost minimizing control strategies for the denitrification process in an activated sludge process are treated. In order to compare different criterion functions, simulations utilizing the COST/IWA simulation benchmark are considered. By means of operational maps the results are visualized. It is found that it is easy to distinguish set-point areas where the process can be said to be efficiently controlled in an economic sense. The characteristics of these set-point areas depend on the chosen effluent nitrate set-point as well as the distribution of the different operating costs. It is also discussed how efficient control strategies may be accomplished.

  • 24.
    Snel, Daniel
    et al.
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Mattsson, Stefan
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Utveckling och analys av en PIC-mikrokontrollers möjligheter att kommunicera via TCP/IP2006Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [sv]

    Sterners Specialfabrik AB tillverkar bland annat mynt- och biljettautomater. För att underlätta felsökning, underhåll, avläsning av statistik med mera på en automat är det lämpligt att detta utförs på en PC över Internet. Det innebär att automaten inte behöver besökas då dessa uppgifter skall utföras. Examensarbetet går ut på att få en PIC mikrokontroller att kommunicera med en användare vid en PC över internet. För detta krävs att en TCP/IP stack implementeras på PICmikrokontrollern. Arbetet ledde till en fungerande demoapplikation som klarar av att kommunicera över TCP/IP. Demoapplikationen innehåller diverse olika funktioner för att demonstrera hur en automat skulle kunna styras och övervakas.

  • 25.
    Sohlberg, Björn
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Control of a pickling process using a grey box model2007In: Automation in Mining, Mineral and Metal Processing, Quebec, 2007Conference paper (Refereed)
    Abstract [en]

    This paper deals with model predictive control using a grey box model. The process is modelled using a priori information and unknown parts are described as general continuous nonlinear functions, which are approximated by means of Taylor series including higher order terms. In the Taylor series, the partial derivatives are estimated from measured data by minimising the maximum likelihood function. The grey box model is used to design and tune a model predictive controller to control the pickling process. The process is a bottle neck in the production line and the simulation shows that the production can be increased approximately 15 % by using the controller.

  • 26.
    Sohlberg, Björn
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Grey box modelling for model predictive control of a heating process2003In: Journal of Process Control, ISSN 0959-1524, E-ISSN 1873-2771, Vol. 13, no 3, p. 225-238Article in journal (Refereed)
  • 27.
    Sohlberg, Björn
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Grey Box Modelling of a Pickling Process using Taylor Serial Expansion2006In: SYSID 2006, 14th IFAC Symposium on System Identification, 2006, Newcastle, Australia, 2006Conference paper (Refereed)
    Abstract [en]

    This paper deals with a case study of grey box modelling where known parts are modelled using a priori information and unknown parts are described as general continuous nonlinear functions, which are approximated by means of Taylor series including higher order terms. In the Taylor series, the partial derivatives are estimated from measured data by minimising the maximum likelihood function. This approach is used to keep the number of estimated parameters low. The modelling procedure follows a structured approach including; basic modelling, data acquisition, model calibration, expanded modelling, stochastic modelling and model appraisal.

  • 28.
    Sohlberg, Björn
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Hybrid grey box modelling of a pickling process2005In: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 13, no 9, p. 1093-1102Article in journal (Refereed)
    Abstract [en]

    This paper deals with grey box modelling of an industrial process, in which known parts are modelled using a priori information and significant unknown parts are described as general continuous nonlinear functions. The modelling procedure follows a structured approach, which includes basic modelling, data acquisition, model calibration, hybrid expanded modelling, stochastic modelling and model appraisal. The general functions are approximated by means of the Taylor series including higher order terms, where the partial derivatives are estimated from measured data by minimising the maximum likelihood function. The Taylor series approach is used to keep the number of estimated parameters low in comparison with other nonlinear black box identification methods. The model is suitable for formulating algorithms to control the process, for example, a model predictive controller. The model can also be used to simulate various different production situations in order to improve the capacity of the total production line. Further, the relevant parts of the Taylor series can be used to explain in what way unknown process parts influence the behaviour of the process and give ideas for further investigation concerning the studied process

  • 29.
    Sohlberg, Björn
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Monitoring and Failure Diagnosis of a Steel Strip Process1998In: IEEE Transactions on Control Systems Technology, ISSN 1063-6536, E-ISSN 1558-0865, Vol. 6, no 2, p. 294-303Article in journal (Refereed)
    Abstract [en]

    This paper deals with condition monitoring and failure diagnosis of a steel strip rinsing process. Modelling and identification of the process is based on a priori knowledge about the process and data from the process. Some parts of the process wear out slowly. It is not possible to measure the wear with any transducers. In the model, the worn parts are modelled explicitly and estimated on-line by an Extended Kalman Filter. The parameter estimation is used for supervision and as an advisory system for the process operators to decide which worn parts should be changed at the next planned stop. In addition to the normal wear, other types of abrupt failures may suddenly occur. It is not possible to detect these failures directly and the failures will give a biased parameter estimate and mislead the process operators into thinking, that a part subject to wear should be changed although it is performing well. Therefore, the condition monitoring system is complemented with a fault detection and diagnosis system, which distinguishes normal wear from sudden abrupt failures.

  • 30.
    Sohlberg, Björn
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Supervision and Control for Industrial Processes: Using Grey Box Models, Predictive Control and Fault Detection Methods1998Book (Other academic)
    Abstract [en]

    Within the process industry, many economic benefits can be achieved by controlling industrial processes at a supervisory level. From an engineering viewpoint, this means using increasingly sophisticated techniques and state-of-the-art theory to optimise process through put and deliver ever more exacting property specifications. Supervision and Control for Industrial Processes considers ways of improving and developing processes using these new methods. In particular, the book demonstrates the use of the grey box modelling method to find an appropriate process model which can be used for control, fault detection and isolation at a supervisory level. This publication will be of particular interest to engineers and graduate students involved in the areas of process control, supervision of industrial processes and failure diagnosis.

  • 31.
    Sohlberg, Björn
    et al.
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Aloto, Y.
    Erdogan, A.
    Erdogan, E.
    Model based fault detection and isolation by fault parameter elimination2010Conference paper (Refereed)
    Abstract [en]

    This paper deals with model based fault detection and isolation of a pickling process within the steel industry. The model is based on the grey box methodology and reflects the physical behaviour of the process. Possible faults are included in the model as parameters, which are estimated on line. The estimation is based on minimizing a loss function using past data from a defined moving time window. The procedure of finding the faults starts by estimate all defined fault parameters. One fault parameter is removed from the set of prospective list of faults by removing the parameter with the smallest saliency. The saliency is defined as the quote between the parameter estimate and the corresponding element of the inverse of the hessian matrix. The parameter with the smallest saliency gives a measure of the relevance of the estimated parameters relative all estimated parameters. The procedure is repeated until all fault parameters are eliminated from the list. To isolate the faults, the Akaike's Information Criterion (AIC) is used to detect faults. This gives the threshold when a fault relevant parameter is removed from the list of prospective faults. © 2010 IFAC.

  • 32.
    Sohlberg, Björn
    et al.
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Jacobsen, Elling W.
    Grey Box Modelling – Branches and Experiences2008In: IFAC World Conference / [ed] Sohlberg, Björn, Seoul, South Korea, 2008Conference paper (Other academic)
    Abstract [en]

    This paper deals with methods and experiences of incorporating a priori knowledge into mathematical models of industrial processes and systems. Grey box modelling has been developed in several directions and can be grouped into branches depending on the way a priori knowledge is handled. In this paper we divide the groups into the following branches; constrained black box identification, semi-physical modelling, mechanistic modelling and hybrid modelling. Experiences from case studies demonstrate the different branches of grey box modelling procedures. In the applications, the grey box models have been used for model based control, soft sensors, process supervision and failure detection

  • 33.
    Sohlberg, Björn
    et al.
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Sernfält, Mats
    Grey Box Modelling for River Control2002In: Journal of Hydroinformatics, ISSN 1465-1734, Vol. 4, no 4, p. 265-280Article in journal (Refereed)
    Abstract [en]

    This paper deals with modelling and identification of a river system using physical insights about the process, experience of operating the system and information about the system dynamics shown by measured data. These components, together, form a linear model structure in the state space form. The inputs of the prospective model are physical variables, which are not directly measured. However, the model inputs can be found by a nonlinear transformation of measured variables. Unknown parameters of the model are estimated from measured data. The modelling work focuses on the principle of parsimony, which means the best model approach is the simplest one that fit the purpose of the application. The goal of the model is to control the water level of the river where the water flow is mainly determined by the demand for energy generation produced by the hydropower stations along the river. The energy requirement increases in the morning and decreases in the evening. These flow variations, caused by the energy demand, have to be compensated by controlling the power plants downstream, in such a way that the water level between the power stations is guaranteed. Simulation of the control system by using an adaptive model predictive controller shows that the water levels vary less and can be maintained at a higher level than during manual control. This means that more electric power can be produced with the same amount of water flow.

  • 34. Spännar, Jan
    et al.
    Wide, Peter
    Sohlberg, Björn
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    A method for measuring strip temperature in the steel industry2005In: IEEE Transactions on Instrumentation and Measurement, ISSN  0018-9456, Vol. 51, no 6Article in journal (Refereed)
    Abstract [en]

    In the steel industry, there are many processes that include measuring and control of temperatures. With higher demand on quality, increased production, and effective energy consumption, the use of noncontact temperature measuring techniques has increased. After the cooling section in a continuous annealing-pickling line, the strip temperature is estimated by using the grey box technique. Temperatures are measured in the cavity between the strip and the roller using radiation thermometers. A model is made for estimating strip temperature using the measured temperatures and knowledge of the physics of the process.

  • 35. Spännar, Jan
    et al.
    Wide, Peter
    Sohlberg, Björn
    Dalarna University, School of Technology and Business Studies, Electrical Engineering.
    Estimation of a Non-Measurable Variable Using Grey Box Modelling2001In: IEEE Instrumentation and Measurement Technology Conference / [ed] Sohlberg, Björn, Budapest, 2001Conference paper (Refereed)
    Abstract [en]

    In the steel industry, there are many processes that include measuring and control of temperatures. With higher demand on quality, increased production and effective energy consumption the use of non-contact temperature measuring techniques has increased. A model is developed for estimating strip temperature using measured temperatures and knowledge of physics of the process.

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