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  • 1.
    Alonso-Fernandez, Fernando
    et al.
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), CAISR - Center for Applied Intelligent Systems Research.
    Bigun, Josef
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), CAISR - Center for Applied Intelligent Systems Research.
    Eye Detection by Complex Filtering for Periocular Recognition2014In: 2nd International Workshop on Biometrics and Forensics (IWBF2014): Valletta, Malta (27-28th March 2014), Piscataway, NJ: IEEE Press, 2014, article id 6914250Conference paper (Refereed)
    Abstract [en]

    We present a novel system to localize the eye position based on symmetry filters. By using a 2D separable filter tuned to detect circular symmetries, detection is done with a few ID convolutions. The detected eye center is used as input to our periocular algorithm based on retinotopic sampling grids and Gabor analysis of the local power spectrum. This setup is evaluated with two databases of iris data, one acquired with a close-up NIR camera, and another in visible light with a web-cam. The periocular system shows high resilience to inaccuracies in the position of the detected eye center. The density of the sampling grid can also be reduced without sacrificing too much accuracy, allowing additional computational savings. We also evaluate an iris texture matcher based on ID Log-Gabor wavelets. Despite the poorer performance of the iris matcher with the webcam database, its fusion with the periocular system results in improved performance. ©2014 IEEE.

  • 2.
    ALRimawi, Mohammed
    Halmstad University, School of Information Technology.
    Doppler Wheel for Emulation of Automotive Radar Target2019Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Automotive radar is an emerging field of research and development. Technological ‎advancements in this field will improve safety for vehicles, pedestrians, and ‎bicyclists, and enable the development of autonomous vehicles. Usage of the ‎Automotive radar is expanding ‎in car and road areas to reduce collisions and ‎accident. Automotive radar ‎developers face a problem to test their radar sensor in ‎the street since there are a lot of interferences ‎signals, noise and unpredicted ‎situations. This thesis provides a part of the solution for this problem by designing a ‎device can demonstrate a different speeds value. This device will help the developer ‎to test their radar sensor inside an anechoic chamber room that provides accurate ‎control of the environmental conditions. This report shows how to ‎build the ‎measuring setup device, step by step to demonstrate the people and vehicle’s speed ‎‎in the street by a Doppler emulator using the wheel for millimetre FWMC radar. ‎Linear speed system needs a large space for testing, but using the rotational wheel ‎allow the developer to test the radar sensor in a small area. It begins with the wheel ‎design specifications and the relation between the ‎rotational speed (RPM) of the ‎wheel and the Doppler frequency. The Doppler ‎frequency is changed by varying the ‎speed of the wheel. Control and power circuit ‎was carefully designed to control the ‎wheel speed accurately. All the measuring ‎setup device parts were assembled in one ‎box. Also, signal processing was done by ‎MATLAB to measure the Doppler frequency ‎using millimetre FMCW radar sensor. ‎The measuring setup device was tested in the ‎anechoic chamber room for different speeds. the ‎manual and automatic tests show ‎good results to measure the different wheel speeds ‎with high accuracy.‎

  • 3.
    Araujo, Hugo
    et al.
    Universidade Federal de Pernambuco, Recife, PE, Brazil.
    Carvalho, Gustavo
    Universidade Federal de Pernambuco, Recife, PE, Brazil.
    Sampaio, Augusto
    Universidade Federal de Pernambuco, Recife, PE, Brazil.
    Mousavi, Mohammad Reza
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Centre for Research on Embedded Systems (CERES).
    Taromirad, Masoumeh
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS).
    A Process for Sound Conformance Testing of Cyber-Physical Systems2017In: 2017 IEEE International Conference on Software Testing, Verification and Validation Workshops (ICSTW) / [ed] Randall Bilof, Los Alamitos, CA: IEEE Computer Society, 2017, p. 46-50, article id 7899032Conference paper (Refereed)
    Abstract [en]

    We present a process for sound conformance testing of cyber-physical systems, which involves functional but also non-functional aspects. The process starts with a hybrid model of cyber-physical systems in which the correct behavior of the system (at its interface level) is specified. Such a model captures both discrete behavior and evolution of continuous dynamics of the system in time. Since conformance testing inherently involves comparing continuous dynamics, the key parameters of the process are (1) the conformance bounds defining when two signals are sufficiently close to each other, and (2) the permitted error margin in the conformance analysis introduced by sampling of continuous signals. The final parameter of this process is (3) finding (and adjusting) the sampling rate of the dynamic behavior. In the specified process, we provide different alternatives for fixing the error margin of the conformance testing if the sampling rate is fixed, establishing the sampling rate if the error margin is fixed and finding conformance bounds once the sampling rate and the error margin are fixed. © 2017 IEEE.

  • 4.
    Bengtsson, Ola
    et al.
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS).
    Baerveldt, Albert-Jan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS).
    Localization in changing environments - Estimation of a covariance matrix for the IDC algorithm2001In: Proceedings 2001 IEEE/RSJ International Conference on Intelligent Robots and Systems. Expanding the Societal Role of Robotics in the the Next Millennium (Cat. No.01CH37180): Volume 4 of 4, Piscataway, N.J.: IEEE, 2001, p. 1931-1937Conference paper (Refereed)
    Abstract [en]

    Previously we have presented a new scan-matching algorithm, based on the IDC - Iterative Dual Correspondence- algorithm, which showed a good localization performance even in the case of severe changes in the environment. The Problem of the IDC-algorithm is that there is no good way to estimate the covariance matrix of the position estimate, which prohibits an effective fusion with other position estimates from other sensors, e.g by means of the Kalman filter. In this paper we present a new way to estimate the covariance matrix, by estimating the Hessian matrix of the error function that is minimized by the IDC scan-matching algorithm. Simulation results show that the estimated covariance matrix correspond well to the real one.

  • 5.
    Blomqvist, Daniel
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE).
    Byttner, Stefan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Intelligent systems (IS-lab).
    Rögnvaldsson, Thorsteinn
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Intelligent systems (IS-lab).
    Holmberg, Ulf
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Intelligent systems (IS-lab).
    Different Strategies for Transient Control of the Air-Fuel Ratio in a SI Engine2000In: SAE transactions : journal of fuels and lubricants, Warrendale, Pa.: Society of automotive engineers (SAE) , 2000, Vol. 109Conference paper (Refereed)
    Abstract [en]

    This paper compares several strategies for air-fuel ratio tran-sient control. The strategies are: A factory-standard look-up table based system (a SAAB Trionic 5), a feedback PI controller with and without feed-forward throttle correction, a linear feed-forward control algorithm, and two nonlinear feed- forward algorithms based on artificial neural networks. The control strategies have been implemented and evaluated in a SAAB 9000 car during a transient driving test, consisting of an acceleration in the second gear from an engine speed of 1500 rpm to 3000 rpm. The best strategies are found to be the neural network based ones, followed by the table based factory system. The two feedback PI controllers offer the poorest performance.

  • 6.
    Byttner, Stefan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS). Chalmers University of Technology, Göteborg, Sweden.
    Algorithms for ion current based sensing of combustion variability and pressure peak position2003Licentiate thesis, comprehensive summary (Other academic)
  • 7.
    Byttner, Stefan
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Intelligent systems (IS-lab).
    Holmberg, Ulf
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Intelligent systems (IS-lab).
    Closed-loop control of EGR using ion currents2008In: Proceedings of the 27th IASTED International Conference on Modelling, Identification, and Control, MIC / [ed] L. Bruzzone, Anaheim: ACTA Press, 2008, p. 7-Conference paper (Refereed)
    Abstract [en]

    Two virtual sensors are proposed that use the spark-plug based ion current sensor for combustion engine control. The first sensor estimates combustion variability for the purpose of controlling exhaust gas recirculation (EGR) and the second sensor estimates the pressure peak position for control of ignition timing. Use of EGR in engines is important because the technique can reduce fuel consumption and NOx emissions, but recirculating too much can have the adverse effect with e.g. increased fuel consumption and poor driveability of the vehicle. Since EGR also affects the phasing of the combustion (because of the diluted gas mixture with slower combustion) it is also necessary to control ignition timing otherwise efficiency will be lost. The combustion variability sensor is demonstrated in a closed-loop control experiment of EGR on the highway and the pressure peak sensor is shown to handle both normal and an EGR condition.

  • 8.
    Byttner, Stefan
    et al.
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), CAISR - Center for Applied Intelligent Systems Research.
    Holmberg, Ulf
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS).
    Ion Current Based Control of Combustion Variability2003Conference paper (Other academic)
  • 9.
    Byttner, Stefan
    et al.
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Intelligent systems (IS-lab).
    Rögnvaldsson, Thorsteinn
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Intelligent systems (IS-lab).
    Wickström, Nicholas
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Intelligent systems (IS-lab).
    Estimation of combustion variability using in-cylinder ionization measurements2001Conference paper (Refereed)
    Abstract [en]

    This paper investigates the use of the ionization current to estimate the Coefficient of Variation for the Indicated Mean Effective Pressure, COV(IMEP), which is a common variable for combustion stability in a spark-ignited engine. Stable combustion in this definition implies that the variance of the produced work, measured over a number of consecutive combustion cycles, is small compared to the mean of the produced work. The COV(IMEP) is varied experimentally either by increasing EGR flow or by changing the air-fuel ratio, in both a laboratory setting (engine in dynamometer) and in an on-road setting. The experiments show a positive correlation between COV(Ion integral), the Coefficient of Variation for the integrated Ion Current, and COV(IMEP), when measured under low load on an engine in a dynamometer, but not under high load conditions. On-road experiments show a positive correlation, but only in the EGR and the lean burn case. An approach based on individual cycle classification for real-time estimation of combustion stability is discussed. © Copyright 2001 Society of Automotive Engineers, Inc.

  • 10.
    Byttner, Stefan
    et al.
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), CAISR - Center for Applied Intelligent Systems Research.
    Rögnvaldsson, Thorsteinn
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), CAISR - Center for Applied Intelligent Systems Research.
    Wickström, Nicholas
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), CAISR - Center for Applied Intelligent Systems Research.
    Strategies for handling the fuel additive problem in neural network based ion current interpretation2001Conference paper (Refereed)
    Abstract [en]

    With the introduction of unleaded gasoline, special fuel agents have appeared on the market for lubricating and cleaning the valve seats. These fuel agents often contain alkali metals that have a significant impact on the ion current signal, thus affecting strategies that use the ion current for engine control and diagnosis, e.g., for estimating the location of the pressure peak. This paper introduces a method for making neural network algorithms robust to expected disturbances in the input signal and demonstrates how well this method applies to the case of disturbances to the ion current signal due to fuel additives containing sodium. The performance of the neural estimators is compared to a Gaussian fit algorithm, which they outperform. It is also shown that using a fuel additive significantly improves the estimation of the location of the pressure peak. © 2001 Society of Automotive Engineers, Inc.

  • 11.
    Camelo, Guilherme Antonio
    et al.
    Federal University of Rio Grande do Sul, Porto Alegre, Brazil.
    Recena Menezes, Maria Luiza
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS). Federal University of Rio Grande do Sul, Porto Alegre, Brazil.
    Pinheiro Sant'Anna, Anita
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS).
    Vicari, Rosa Maria
    Federal University of Rio Grande do Sul, Porto Alegre, Brazil.
    Pereira, Carlos Eduardo
    Federal University of Rio Grande do Sul, Porto Alegre, Brazil.
    Control of Smart Environments Using Brain Computer Interface Based on Genetic Algorithm2016In: Lecture Notes in Computer Science, ISSN 0302-9743, E-ISSN 1611-3349, Vol. 9622, p. 773-781Article in journal (Refereed)
    Abstract [en]

    This work deals with the development of an interface to control a smart conference room using passive BCI (Brain Computer Interface). It compares a genetic algorithm developed in a previous project to control the smart conference room with a random control algorithm. The system controls features of the conference room such as air conditioner, lightning systems, electric shutters, entertainment devices, etc. The parameters of the algorithm are extracted from users biosignal using Emotiv Epoc Headset while the user performs an attention test. The tests indicate that the decisions made by the genetic algorithm lead to better results, but in a single execution cannot be considered an effective optimization algorithm. © Springer-Verlag Berlin Heidelberg 2016.

  • 12.
    Dincay, Berkan
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).
    GPS/Optical Encoder Based Navigation Methods for dsPIC Microcontroled Mobile Vehicle2010Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    Optical encoders are being widely suggested for precise mobile navigation. Combining such sensor information with Global Positioning System (GPS) is a practical solution for reducing the accumulated errors from encoders and moving the navigational base into global coordinates with high accuracy.

    This thesis presents integration methods of GPS and optical encoders for a mobile vehicle that is controlled by microcontroller. The system analyzed includes a commercial GPS receiver, dsPIC microcontroller and mobile vehicle with optical encoders. Extended kalman filtering (EKF), real time curve matching, GPS filtering methods are compared and contrasted which are used for integrating sensors data. Moreover, computer interface, encoder interface and motor control module of dsPIC microprocessor have been used and explained.

    Navigation quality on low speeds highly depends greatly upon the processing of GPS data. Integration of sensor data is simulated for both EKF and real time curve matching technique and different behaviors are observed. Both methods have significantly improved the accuracy of the navigation. However, EKF has more advantages on solving the localization problem where it is also dealing with the uncertainties of the systems.

  • 13.
    Emanuelsson, Herman
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE).
    Sjunnesson, Emil
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE).
    Fjärrstyrt kamerafäste: HE Remote2013Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    At times when it is not suited to stand by a video camera can be resolved with a remote controlled camera mount. Examples of occasions is due to lack of space at a concert, a solemn ceremony in which someone must stand awkwardly  to to get good image, out in nature where animals shall be filmed without being frightened away or when you have staff shortages, a tight budget and need to control multiple cameras simultaneously. The systems that are available in the amateur market today have different functionality and is not fitting for the above problem or have very limited range and cannot connect to a mobile application.

    This project aims to develop a cost-effective and customized solution for the above problem by developing a remote-controlled camera mount in semi-professional segment where you through a controller and at a later stage with a mobile application controls the camera angle and rotation also called tilt and pan.

    The differences between this and existing solutions are that by using Bluetooth technology can control both the controller and later on also with a mobile application, the reason why it must be able to control both is that it is not always allowed to use cell phones in all environments where you want to film and therefore have a wider range of applications for camera mounting.

  • 14.
    Englund, Cristofer
    et al.
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Intelligent systems (IS-lab).
    Verikas, Antanas
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Intelligent systems (IS-lab).
    Ink feed control in a web-fed offset printing press2008In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 39, no 9-10, p. 919-930Article in journal (Refereed)
    Abstract [en]

    Automatic and robust ink feed control in a web- fed offset printing press is the objective of this work. To achieve this goal an integrating controller and a multiple neural models-based controller are combined. The neural networks-based printing process models are built and updated automatically without any interaction from the user. The multiple models-based controller is superior to the integrating controller as the process is running in the training region of the models. However, the multiple models-based controller may run into generalisation prob- lems if the process starts operating in a new part of the input space. Such situations are automatically detected and the integrating controller temporary takes over the process control. The developed control configuration has success- fully been used to automatically control the ink feed in the web-fed offset printing press according to the target amount of ink. Use of the developed tools led to higher print quality and lower ink and paper waste.

  • 15.
    Eriksson, Hanna
    et al.
    Halmstad University, School of Information Technology.
    Gustafsson, Eric
    Halmstad University, School of Information Technology.
    Flexibelt ställdon2016Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
  • 16.
    Gustavsson, Martin
    et al.
    Halmstad University, School of Information Technology.
    Frimodig, Viktor
    Halmstad University, School of Information Technology.
    Virtual Prototyping and Physical Validation of an Inverted Pendulum: "Sea-Calf Bot"2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The work is motivated by the goal of linking reality and model, and to see if there is an opportunity to develop an inexpensive educational tool for training in cyber-physical systems.

    This project has investigated the possibilities to build a cheap inverted pendulum with controller and connect this with the modeling language Acumen. Acumen models is used for comparison with the actual prototype.

    To solve these problems has a 3D printer been used to create hardware, Arduino UNO for control and Raspberry Pi for enable communication with Acumen over WLAN.

    The result was a cheap inverted pendulum, which can be built for a cost around 750 SEK. Graphs created in Acumen and from data collected from sensors can be analyzed.

    With a model of the inverted pendulum system, the results show that Acumen can be used in the development of cyber-physical systems. There are differences between model and reality but also similarities.

  • 17.
    Hellring, Magnus
    et al.
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS).
    Holmberg, Ulf
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS).
    A Comparison of Ion Current Based Algorithms for Peak Pressure Position Control2001In: SAE technical paper series, ISSN 0148-7191, article id 2001-01-1920Article in journal (Refereed)
    Abstract [en]

    Combustion timing control of SI engines can be improved by feedback of the peak pressure position (PPP). However, pressure sensors are costly, and therefore, nonintrusive and cheap ion-current ’soft sensors’ have been suggested. Three different algorithms have been proposed that extract information about PPP from the ion current signal. In this paper, these approaches are compared with respect to accuracy, operational range, implementation aspects, as well as sensitivity to engine load and inlet air humidity. Copyright © 2001 Society of Automotive Engineers, Inc.

  • 18.
    Hellring, Magnus
    et al.
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS).
    Holmberg, Ulf
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS). Ulf.Holmberg@ide.hh.se.
    An ion current based peak-finding algorithm for pressure peak position estimation2000In: SAE technical paper series, ISSN 0148-7191, article id 2000-01-2829Article in journal (Refereed)
    Abstract [en]

    In this paper a novel ion current based estimation scheme for the in-cylinder pressure peak position (PPP) is proposed. A reliable estimate is constructed by appropriate signal processing based on local curvatures of the post flame phase of the ion current. The peak-finding algorithm is simple and easy to implement in an engine control unit for feedback control of the combustion phasing. Results on real data, sampled onboard a commercial car are presented. Further, the performance of the algorithm is compared to two state of the art algorithms for PPP estimation from the ion current. The comparison shows that the algorithm presented in this paper outperforms its competitors. Copyright © 2000 Society of Automotive Engineers, Inc.

  • 19.
    Henriksson, Kim
    et al.
    Halmstad University, School of Information Technology.
    Hellström, Patrik
    Halmstad University, School of Information Technology.
    Vidareutveckling av granulat 3d-skrivare2017Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The average 3d-printer has a relatively small print surface which limits the sizeof the prints themselves and there is a void on the market for printers that can printparts as big as, for instance, a car bumper . This project aims to further advancethe construction of a large 3d-printer started by previous students at Halmstad University and focuses at print quality and accuracy.

  • 20.
    Hillberg, Erik
    Halmstad University, School of Information Technology.
    BlackBox: Integration mellan Solceller och Vindkraftverk2018Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In society today the production of energy has aimed its focus towards the resources that are renewable as a result of their ability to avoid negative effects of the environment. In the future it is desired to have replaced the current market entirely with these options which generates a demand to optimize these resources and their capabilities to produce energy. The current situation of production require separate systems to generate energy from a solar system and windmills which is a clear economic disadvantage.  Therefore it is highly desired to establish a solution to combine these two systems into one where they can generate energy collectively, this would result in the possibility to avoid unnecessary costs when these are desiderated to combine. Through development and executed testing’s a prototype has been created to counter this demand which will be presented in this thesis along with the positive effects this will have on the market of energy production concerning the environment as well as financially. The prototype has been created with the possibility to integrate a windmill into a solar system. Tests have been conducted in order to ensure that the project goals have been achieved. Through the execution of this project it has been determined that integration between a solar system and a windmill is feasible without major expenses.

  • 21.
    Holmberg, Ulf
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).
    Comments on “A Revisit to the Gain and Phase Margins ofLinear Quadratic Regulators”2001In: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 46, no 9, p. 1508-1509Article in journal (Refereed)
    Abstract [en]

    In the above paper, an example is given, showing that the LQ controller gives an arbitrary small gain margin with respect to variations of the open-loop plant. As a remedy, a dynamic-state feedback is proposed which is claimed to give an arbitrary large gain margin. This is incorrect. In fact, the proposed dynamic state feedback controller does not even stabilize the nominal system.

  • 22.
    Holmberg, Ulf
    et al.
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS).
    Valentinotti, S.
    Institut d 'Automatique, Ecole Polytechnique Federale de Lausanne, Switzerland.
    Bonvin, D.
    Institut d 'Automatique, Ecole Polytechnique Federale de Lausanne, Switzerland.
    An identification-for-control procedure with robust performance2000In: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 8, no 10, p. 1107-1117Article in journal (Refereed)
    Abstract [en]

    A data-driven controller design procedure is proposed in this paper. The controller is based on both an estimated plant model and its estimated uncertainty described by an ellipsoid in parameter space. Desired performance is specified by the speed and the damping of the modeled response. The unmodeled response is rejected by requiring robust performance with respect to a generalized stability region. Moreover, estimation of a disturbance model enables further rejection of the unmodeled response. The methodology is applied to a nonlinear and unstable magnetic suspension system. High performance is achieved for various specifications over a large operational range.

  • 23.
    Juneby, Hans
    et al.
    Halmstad University, School of Information Technology.
    Can, Mikael
    Halmstad University, School of Information Technology.
    Newtons andra vagn2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    A problem of basic physics education in schools is that gravitation constantly interferes with experiments and demonstrations, making it difficult for students to understand Newton's first and second laws. The goal of this project is to improve the physics education in colleges and universities. To solve the problem we created a demonstration system that effectively demonstrates an inertial reference frame and Newton's second law by driving a specially designed train with constant velocity or constant acceleration. Students are able to perform three different experiments which are controlled via a webpage or by remote control, and analyse the output through plotted graphs. After extensive testing, the train and experiments proved successful and we concluded that physics education can be effectively improved with the help of practical experiments that students themselves can perform.

  • 24.
    Kleyko, Denis
    et al.
    Luleå University of Technology, Luleå, Sweden.
    Hostettler, Roland
    Aalto University, Helsinki, Finland.
    Lyamin, Nikita
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Centre for Research on Embedded Systems (CERES).
    Birk, Wolfgang
    Luleå University of Technology, Luleå, Sweden.
    Wiklund, Urban
    Umea Univ, Dept Biomed Engn & Informat, Umea, Sweden..
    Osipov, Evgeny
    Luleå University of Technology, Luleå, Sweden.
    Vehicle Classification using Road Side Sensors and Feature-free Data Smashing Approach2016In: 2016 IEEE 19th International Conference on Intelligent Transportation Systems (ITSC), Piscataway: IEEE , 2016, p. 1988-1993, article id 7795877Conference paper (Refereed)
    Abstract [en]

    The main contribution of this paper is a study of the applicability of data smashing - a recently proposed data mining method - for vehicle classification according to the "Nordic system for intelligent classification of vehicles" standard, using measurements of road surface vibrations and magnetic field disturbances caused by passing vehicles. The main advantage of the studied classification approach is that it, in contrast to the most of traditional machine learning algorithms, does not require the extraction of features from raw signals. The proposed classification approach was evaluated on a large dataset consisting of signals from 3074 vehicles. Hence, a good estimate of the actual classification rate was obtained. The performance was compared to the previously reported results on the same problem for logistic regression. Our results show the potential trade-off between classification accuracy and classification method's development efforts could be achieved.

  • 25.
    Lee, Jean-Philip
    et al.
    Halmstad University, School of Information Technology.
    Andersson, Johan
    Halmstad University, School of Information Technology.
    Diab Control System2018Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In order to control a system or process a PID-regulator is often used although they can be difficult to tune so that they give the system a preferred behaviour. The goal with this project is to tune a PID-controller that controls the temperature of a large water tank. The initial systems temperature fluctuates around the set temperature by +/- 1◦C and our goal is to reduce it to +/- 0.5◦C. The project will use the parametric method of a step response in order to evaluate the systems behaviour into a transfer function model that can be PID-tuned.

    The system was modeled into a a first order model that matches the heating and cooling separately although not together since they have different time constants. Therefore a second order model was made. This model did not match the collected data very good but is used to get a better understanding of the system and figure out what kind of parameters that are required in order to create a better matching model.

    The final conclusion is that in order to get a matching transfer function of the plant a second order model or higher must be uses and also that more data distributed along more parameters need to be logged in order to understand the entire system behaviour.

  • 26.
    Madagalam, Mallikarjun
    Halmstad University, School of Information Technology. Lund University.
    Pulse Energy Stabilization of a Femtosecond Laser Pulse Chain2016Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
  • 27.
    Mak, Spencer
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE).
    Bjäde, Mattias
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE).
    Design and Implementation of Cooperative Adaptive Cruise Control2011Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    With limited road infrastructure and increasing number of vehicles on the road, an intelligent transport system is needed to increase the throughput in traffic and minimize traffic jams in highly populated areas. The purpose of this project is to design and implement a control system that is capable of driving and following the preceding vehicle autonomously in the longitude direction only. The vehicle is also equipped with a vehicle to vehicle communication unit. With this information, all vehicles on the road can communicate with each other and are able to achieve shorter distances between vehicles and damp any disturbance caused by upstream traffic. A general structure on Cooperative Adaptive Cruise Control (CACC) is created by studying the research from The Netherlands Organization for Applied Scientific Research (TNO). A string stability criterion is used to determine if the system is suitable of driving in a platoon, where a string of vehicles are following a lead vehicle. This system is then implemented in a Volvo S60 and has participated in the 2011 Grand Cooperative Driving Challenge hosted in The Netherlands. The results show that the system has ability to increase throughput and damp disturbance on the upstream traffic by communicating with the other vehicles ahead. The system is also robust and simple enough to earn the 2nd place in the competition.

  • 28.
    MALEKRAH, MEHDI
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab.
    Electrical and Optical Charactristics of InP Nanowire Photodetectors2010Independent thesis Advanced level (degree of Master (One Year)), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    In this project Fourier Transform Infrared Spectroscopy is used to investigate a new kind of photodiode that is based on nanowires. The photo current and I-V curves for different temperatures, different applied biases, in darkness and illumination condition have been studied. The experiment was conducted in the temperature range from 78 K (-195ºC) to 300 K (27ºC). These photo diodes are designed to work on NIR wavelengths. The results show some excellent properties, such as high break down voltage, and that is an important advantage for photo detectors, low and constant reverse saturation current (Is). The results show some defects, most of them come from fabrication. The design of the sample is also discussed.

  • 29.
    Mastrorilli, Andrea
    et al.
    Halmstad University, School of Information Technology.
    Holmgren, Josefin
    Halmstad University, School of Information Technology.
    Paddle stirrer to a reverberation chamber2019Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Halmstad University is currently equipped with an Echo-free chamber to perform EMC testing, but no reverberation chamber. The construction of a paddle stirrer to be utilized in Halmstad University would drastically reduce the time required to perform EMC testing, since reverberation chambers are more efficient than Echo-free chambers for these kind of tests. The goal of this project was to design and develop a paddle stirrer structure and a control system able to rotate the stirrer to specific repeatable absolute angles with an accuracy of a tenth of a degree,holding a mass up to 70kg and rotating a mass up to 20 kg distributed on a 1x1m surface. To achieve this goal the system has been designed using a metal base structure, bearings to hold the lower shaft in its axes reducing its friction, a stepper motor connected to the gears to increase its holding torque, a magnetic rotary encoder and a control system with a double feedback from interrupts and from the encoder to improve the accuracy and reliability of the system. The resultis a completely working prototype, which fulfils all the requirements except for the speed. The target speed has not been achieved due to the insufficient holding torque of the available stepper motor.

  • 30.
    Moggi, E.
    et al.
    DIBRIS, Genova Univ., v. Dodecaneso 35, Genova, 16146, Italy.
    Farjudian, A.
    University of Nottingham Ningbo, China.
    Duracz, Adam
    Rice University, Houston, TX, United States.
    Taha, Walid
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Centre for Research on Embedded Systems (CERES).
    Safe & robust reachability analysis of hybrid systems2018In: Theoretical Computer Science, ISSN 0304-3975, E-ISSN 1879-2294, Vol. 747, p. 75-99Article in journal (Refereed)
    Abstract [en]

    Hybrid systems—more precisely, their mathematical models—can exhibit behaviors, like Zeno behaviors, that are absent in purely discrete or purely continuous systems. First, we observe that, in this context, the usual definition of reachability—namely, the reflexive and transitive closure of a transition relation—can be unsafe, i.e., it may compute a proper subset of the set of states reachable in finite time from a set of initial states. Therefore, we propose safe reachability, which always computes a superset of the set of reachable states. Second, in safety analysis of hybrid and continuous systems, it is important to ensure that a reachability analysis is also robust w.r.t. small perturbations to the set of initial states and to the system itself, since discrepancies between a system and its mathematical models are unavoidable. We show that, under certain conditions, the best Scott continuous approximation of an analysis A is also its best robust approximation. Finally, we exemplify the gap between the set of reachable states and the supersets computed by safe reachability and its best robust approximation. © 2018 The Authors

  • 31.
    Nguyen, Tuananh
    et al.
    Halmstad University, School of Information Technology.
    Szabo, David
    Halmstad University, School of Information Technology.
    LEGO-Modell av Watt-balansvåg2016Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Within the near future there is a plan to reconstruct the InternationalSystem of Units (SI) where the seven base units; kilogram, meter, second,mol, candela, ampere and kelvin, will no longer serve as the foundation ofthe system. Instead all SI-units will be realized by using a number ofcarefully chosen fundamental constants of nature, which have been givenfixed values threw reproducible methods. The kilogram is presently theonly base unit still represented by a physical object. One of the leadingmethods in the pursuit of redefining the kilogram is called a Watt Balance.The concept of a Watt Balance is based on the comparison of mechanicalpower and electrical power, with the common factor between mechanicaland electrical units being Plancks constant. The National Institute ofStandards and Technology (NIST) in the USA have designed a WattBalance LEGO-model used for demonstrations. At SP Sveriges TekniskaForskningsinstitut a reconstruction of the LEGO-model was considered tobe an interesting way of starting to build a level of competence around theredifinition of the kilogram. By using the LEGO-model, SPs purpose alsoinvolves the ability to explain and demonstrate the concept of a WattBalance to authorities, companies and future innovation partners. Thepurpose of the project described in this thesis was to improve an ongoingreconstruction of the LEGO-model at SP by reducing a systematicmeasurement error at 15-20% over actual mass. Using a scientific method,theories to the causes of error were formed and tested threw systematicmeasurements. Based on the result, the systematic error have beenreduced from 15-20% over to approximately 0-4% under the actual mass.The reason for the remaining systematic error is considered being relatedto an uncertainty in the measurement of a relation between a magneticflux and an electric coil. The result from the measurement is based on theinduced voltage in a coil with a velocity calculated from the voltageoutput produced by a shadow sensor. The error is presumed to be relatedto both voltage measurements. A more comprehensive analysis regardingthe sample time and resolution of the device used in the voltagemeasurements, could improve the LEGO-model further.

  • 32.
    Okhtilev, Michael
    et al.
    St.-Petersburg Institute for Informatics and Automation, 39, 14th Line, Spiiran, St. Petersburg, 199178, Russian Federation.
    Sokolov, Boris
    St.-Petersburg Institute for Informatics and Automation, 39, 14th Line, Spiiran, St. Petersburg, 199178, Russian Federation.
    Vinel, Alexey
    St.-Petersburg Institute for Informatics and Automation, 39, 14th Line, Spiiran, St. Petersburg, 199178, Russian Federation.
    Zaichik, Eugene
    St.-Petersburg Institute for Informatics and Automation, 39, 14th Line, Spiiran, St. Petersburg, 199178, Russian Federation.
    Information and telecommunication intellectual monitoring technology and system for complex technical objects under dynamic conditions in real time2009In: NESTER 2009: Networked Embedded and Control System Technologies: European and Russian R&D Cooperation, Proceedings / [ed] Pascoal, A, Ufnarovsky, V, Setubal: INSTICC Press, 2009, p. 17-25Conference paper (Refereed)
    Abstract [en]

    The aim of the investigation is to develop methods, models and algorithms of synthesis and intellectualization of monitoring technology and system oriented to concurrent on-line user software assurance for all sorts of measuring information specifying states of complex technical objects under dynamic conditions in real time. This aim should be achieved by here suggested artificial intelligent information technology. The basis of this artificial intelligent information technology is flow computing models exploitable by state hipping (constraint programming) in real time and in territorially distributed computing network. At the same time each network node represents artificial intelligent agent. Furthermore, the problem of efficient information transmission between the complex technical objects and monitoring systems by means of contemporary wireless technologies is considered.

  • 33.
    Petersson, Daniel
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Intelligent systems (IS-lab).
    Johansson, Jonas
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Intelligent systems (IS-lab).
    Holmberg, Ulf
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Intelligent systems (IS-lab).
    Åstrand, Björn
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Intelligent systems (IS-lab).
    Torque Sensor Free Power Assisted Wheelchair2007In: ICORR '07: 2007 IEEE 10th International Conference on Rehabilitation Robotics : June 12-15, Noordwijk, The Netherlands, Piscataway, N.J.: IEEE Press, 2007, p. 151-157Conference paper (Refereed)
    Abstract [en]

    A power assisted wheelchair combines human power, which is delivered by the arms through the pushrims, with electrical motors, which are powered by a battery. Todays electric power assisted wheelchairs use force sensors to measure the torque exerted on the pushrims by the user. This leads to rather expensive and clumsy constructions. A new design, which only relies on velocity feedback, thus avoiding the use of expensive force sensors in the pushrims, is proposed in this paper. The control design is based on a simple PD-structure with only two design parameters easily tuned to fit a certain user; one parameter is used to adjust the amplification of the user’s force and the other one is used to change the lasting time of the propulsion influence. Since the new assisting control system only relies on the velocity, the torque sensor free power assisted wheelchair will besides giving the user assisting power also give an assistant, which pushes the wheelchair, additional power. This is a big advantage compared to the pushrim activated one, where this benefit for the assistant is not possible.

  • 34.
    Sant'Anna, Anita
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Intelligent Systems´ laboratory.
    Salarian, Arash
    Oregon Health and Science Univeristy.
    Wickström, Nicholas
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Intelligent Systems´ laboratory.
    A new measure of movement symmetry in early Parkinson's disease patients using symbolic processing of inertial sensor data2011In: IEEE Transactions on Biomedical Engineering, ISSN 0018-9294, E-ISSN 1558-2531, Vol. 58, no 7, p. 2127-2135Article in journal (Refereed)
    Abstract [en]

    Movement asymmetry is one of the motor symptoms associated with Parkinson's Disease (PD). Therefore, being able to detect and measure movement symmetry is important for monitoring the patient's condition.

    The present paper introduces a novel symbol based symmetry index calculated from inertial sensor data. The method is explained, evaluated and compared to six other symmetry measures. These measures were used to determine the symmetry of both upper and lower limbs during walking of 11 early-to-mid-stage PD patients and 15 control subjects. The patients included in the study showed minimal motor abnormalities according to the Unified Parkinson's Disease Rating Scale (UPDRS).

    The symmetry indices were used to classify subjects into two different groups corresponding to PD or control. The proposed method presented high sensitivity and specificity with an area under the Receiver Operating Characteristic (ROC) curve of 0.872, 9\% greater than the second best method. The proposed method also showed an excellent Intraclass Correlation Coefficient (ICC) of 0.949, 55\% greater than the second best method. Results suggest that the proposed symmetry index is appropriate for this particular group of patients.

  • 35.
    Svensson, Wolfgang
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).
    Holmberg, Ulf
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).
    An Autonomous Control System for a Prosthetic Foot Ankle2006In: 4th IFAC Symposium on Mechatronic Systems (2006), International Federation of Automatic Control (IFAC) , 2006, p. 856-861Conference paper (Refereed)
    Abstract [en]

    When walking on inclined ground the biological foot adjusts the ankle angle accordingly. Prosthetic foot users have often a limited range of motion in their ankle which makes walking on hills uncomfortable. This paper describes a system which can autonomously correct the ankle angle to the inclination. The ground angle is estimated using an accelerometer. The angle foot blade to heel is then adjusted with a DC-motor. Since the controller only activates the motor when the foot is lifted and thus not loaded, a small powered system can be used.

  • 36.
    Svensson, Wolfgang
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Intelligent systems (IS-lab).
    Holmberg, Ulf
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Intelligent systems (IS-lab).
    Ankle-Foot-Orthosis Control in Inclinations and Stairs2008In: 2008 IEEE Conference on Robotics, Automation and Mechatronics, Piscataway, N.J.: IEEE Press, 2008, p. 301-306Conference paper (Refereed)
    Abstract [en]

    A control procedure is proposed for an ankle-footorthosis (AFO) for different gait situations, such as inclinations and stairs. This paper presents a novel AFO control of the ankle angle. A magneto-rheological damper was used to achieve ankle damping during foot down and locking at swing, thereby avoiding foot slap as well as foot drop.

    The controller used feedback from the ankle angle only. Still it was capable of not only adjusting damping within a gait step but also changing control behavior depending on level walking, ascending and descending stairs. As a consequence, toe strike was possible in stair gait as opposed to heel strike in level walking.

    Tests verified the expected behavior in stair gait and in level walking where gait speed and ground inclinations varied. The self-adjusted AFO is believed to improve gait comfort in slopes and stairs.

  • 37.
    Svensson, Wolfgang
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Intelligent systems (IS-lab).
    Holmberg, Ulf
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Intelligent systems (IS-lab).
    Ground angle estimator from an ankle foot orthosis based on strain sensing and Fourier series2008In: IEEE International Conference on Mechatronics and Automation, 2008. ICMA 2008, Piscataway, N.J.: IEEE Press, 2008, p. 203-206Conference paper (Refereed)
    Abstract [en]

    A ground angle estimation technique for use on ankle-foot-orthosis AFO, during gait is proposed. Strain gauge sensors were mounted on a foot orthosis in order to give information about strain in the sagittal plane. The ankle angle of the orthosis was fixed. Strain characteristics were therefore changed when walking on slopes. It was investigated if strain information could be used for detection of inclination and estimation of inclination angle. With a Fourier series representation of the strain during a gait cycle, ground angle at different walking speeds and inclinations could be estimated with similar accuracy as previous studies using kinematically based estimators. This indicates that embedded strain sensors can be used for online control of future orthoses with inclination adaptation.

  • 38.
    Svensson, Wolfgang
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE).
    Holmberg, Ulf
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).
    Stair Gait Classification from Kinematic Sensors2007In: Rehabilitation Robotics / [ed] Sashi S. Kommu, Wien: I-Tech Education and Publishing KG, 2007, p. 523-534Chapter in book (Other academic)
    Abstract [en]

    Gait measurement is of interest for both orthopedists and biomechanical engineers. It is useful for analysis of gait disorders and in design of orthotic and prosthetic devices.

    In this chapter an algorithm is presented to suit estimation of one foot angle in the sagital plane, independent on gait conditions. Only one gyro is used during swing and two accelerometers are needed for calibration during stance. Also, the sensor placement at the front foot avoids the need for heel strike for stance transition. Stair walking can therefore be studied. From the estimated swing trajectory three different gait conditions: up stair, horizontal and down stair are classified.

  • 39.
    Svensson, Wolfgang
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Intelligent systems (IS-lab).
    Salomonsson, Tommy
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Intelligent systems (IS-lab).
    Holmberg, Ulf
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Intelligent systems (IS-lab).
    Foot orthosis strain sensing in hill walking2007In: ICORR '07: 2007 IEEE 10th International Conference on Rehabilitation Robotics : June 12-15, Noordwijk, The Netherlands, Piscataway, N.J.: IEEE Press, 2007, p. 700-703Conference paper (Refereed)
    Abstract [en]

    An embedded measurement system for foot orthosis during gait is proposed. In this paper strain gauge sensors are mounted on a foot orthosis in order to give information about strain in the sagital plane. The ankle angle of the orthosis is fixed. Strain characteristics are therefore changed when walking on slopes. It is investigated if strain information can be used for detection of inclination and estimation of inclination angle. Also walking speed influence is studied. It is shown that strain sensing only gives significant information about up hill walking. At a known walking speed ground angle can be estimated for up hill walking.

  • 40.
    Thunberg, Johan
    et al.
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS).
    Lyamin, Nikita
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Centre for Research on Embedded Systems (CERES).
    Sjöberg, Katrin
    Scania, Södertälje, Sweden.
    Vinel, Alexey
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Centre for Research on Embedded Systems (CERES).
    Vehicle-to-Vehicle Communications for Platooning: Safety Analysis2019In: IEEE Networking Letters, ISSN 2576-3156Article in journal (Refereed)
    Abstract [en]

    Vehicle-to-vehicle (V2V) communication is the key technology enabling platooning. This paper proposes an analytical framework that combines the characteristics of V2V communication (packet loss probabilities and packet transmission delays) with the physical mobility characteristics of vehicles (speed, distance between vehicles and their brake capacities). First, we present the feasible region of communications delays which guarantees safe emergency braking in platooning scenarios. Second, we derive a bound on the probability of safe braking. The presented framework is applied to understand the performance of the state-of-the-art V2V communication protocol for platooning.

  • 41.
    Thunberg, Johan
    et al.
    Luxembourg Centre for Systems Biomedicine, University of Luxembourg, Luxembourg.
    Markdahl, Johan
    Luxembourg Centre for Systems Biomedicine, University of Luxembourg, Luxembourg.
    Bernard, Florian
    Max-Planck-Institute for Informatics, Saarland Informatics Campus, Germany.
    Goncalves, Jorge
    Systems Biomedicine, University of Luxembourg, Luxembourg.
    A lifting method for analyzing distributed synchronization on the unit sphere2018In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 96, p. 253-258Article in journal (Refereed)
    Abstract [en]

    This paper introduces a new lifting method for analyzing convergence of continuous-time distributed synchronization/consensus systems on the unit sphere. Points on the d-dimensional unit sphere are lifted to the (d+1)-dimensional Euclidean space. The consensus protocol on the unit sphere is the classical one, where agents move toward weighted averages of their neighbors in their respective tangent planes. Only local and relative state information is used. The directed interaction graph topologies are allowed to switch as a function of time. The dynamics of the lifted variables are governed by a nonlinear consensus protocol for which the weights contain ratios of the norms of state variables. We generalize previous convergence results for hemispheres. For a large class of consensus protocols defined for switching uniformly quasi-strongly connected time-varying graphs, we show that the consensus manifold is uniformly asymptotically stable relative to closed balls contained in a hemisphere. Compared to earlier projection based approaches used in this context such as the gnomonic projection, which is defined for hemispheres only, the lifting method applies globally. With that, the hope is that this method can be useful for future investigations on global convergence.

  • 42.
    Thunberg, Johan
    et al.
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Centre for Research on Embedded Systems (CERES).
    Markdahl, Johan
    Luxembourg Centre for Systems Biomedicine, University of Luxembourg, Luxembourg.
    Goncalves, Jorge
    Luxembourg Centre for Systems Biomedicine, University of Luxembourg, Luxembourg.
    Dynamic controllers for column synchronization of rotation matrices: A QR-factorization approach2018In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 93, p. 20-25Article in journal (Refereed)
    Abstract [en]

    In the multi-agent systems setting, this paper addresses continuous-time distributed synchronization of columns of rotation matrices. More precisely, k specific columns shall be synchronized and only the corresponding k columns of the relative rotations between the agents are assumed to be available for the control design. When one specific column is considered, the problem is equivalent to synchronization on the (d−1)-dimensional unit sphere and when all the columns are considered, the problem is equivalent to synchronization on SO(d). We design dynamic control laws for these synchronization problems. The control laws are based on the introduction of auxiliary variables in combination with a QR-factorization approach. The benefit of this QR-factorization approach is that we can decouple the dynamics for the k columns from the remaining d−k ones. Under the control scheme, the closed loop system achieves almost global convergence to synchronization for quasi-strong interaction graph topologies.

  • 43.
    Uddman Jansson, Oscar
    et al.
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Centre for Research on Embedded Systems (CERES).
    Shahanoor, Golam
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), CAISR - Center for Applied Intelligent Systems Research.
    Evaluation of string stability during highway platoon merge2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Automated vehicles are considered to be the future solution to reduce

    traffic congestion and to increase road safety. The Adaptive Cruise

    Control (ACC) has been introduced as Advance Driver Assistance System

    (ADAS) to improve road network utilization. However, complex

    traffic situations are still resolved by human drivers. Vehicular communication

    has been introduced to interconnect different nodes in

    the transport system for example vehicles, infrastructure, and vulnerable

    road users. Communication enables improved local awareness of

    the road users and the potential to further improve the performance

    is increased. In this study, a popular ACC algorithm, the notion of

    string stability and the concept of Cooperative Adaptive Cruise Control

    (CACC) are discussed. A new CACC algorithm is proposed focusing

    on maintaining platoon string stability during different traffic

    situations. The performance of the controller is compared with one

    of the most accepted ACC algorithms. The proposed controller was

    implemented in a real world cooperative highway merge scenario.

    The collected data was presented and appraised under three different

    evaluation criteria. The controller has shown low downstream

    error propagation in simulation and in real world experiment it successfully

    maintained string stability during highway platooning and

    merging scenarios.

  • 44.
    Wei, Jieqiang
    et al.
    ACCESS Linnaeus Centre School of Electrical Engineering, KTH Royal Institute of Technology, Stockholm, Sweden.
    Zhang, Silun
    School of Engineering Sciences, KTH Royal Institute of Technology, Stockholm, Sweden..
    Adaldo, Antonio
    ACCESS Linnaeus Centre School of Electrical Engineering, KTH Royal Institute of Technology, Stockholm, Sweden.
    Thunberg, Johan
    Halmstad University, School of Information Technology. Luxembourg Centre for Systems Biomedicine, University of Luxembourg, Luxembourg.
    Hu, Xiaoming
    Division of Optimization and Systems Theory Department of Mathematics, KTH Royal Institute of Technology, Stockholm, Sweden.
    Johansson, Karl Henrik
    ACCESS Linnaeus Centre School of Electrical Engineering, KTH Royal Institute of Technology, Stockholm, Sweden.
    Finite-Time Attitude Synchronization With Distributed Discontinuous Protocols2018In: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 63, no 10, p. 3608-3615Article in journal (Refereed)
    Abstract [en]

    The finite-time attitude synchronization problem is considered in this paper, where the rotation of each rigid body is expressed using the axis-angle representation. Two discontinuous and distributed controllers using the vectorized signum function are proposed, which guarantee almost global and local convergence, respectively. Filippov solutions and nonsmooth analysis techniques are adopted to handle the discontinuities. Sufficient conditions are provided to guarantee finite-time convergence and boundedness of the solutions. Simulation examples are provided to verify the performances of the control protocols designed in this paper. 

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