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  • 8901.
    Öberg, Per
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, The Institute of Technology.
    Nyberg, Peter
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, The Institute of Technology.
    Nielsen, Lars
    Linköping University, The Institute of Technology.
    A New Chassis Dynamometer Laboratory for Vehicle Research2013In: SAE International Journal of Passenger Cars - Electronic and Electrical Systems, ISSN 1946-4614, E-ISSN 1946-4622, Vol. 6, no 1, p. 152-161Article in journal (Refereed)
    Abstract [en]

    In recent years the need for testing, calibration and certification of automotive components and powertrains have increased, partly due to the development of new hybrid concepts. At the same time, the development within electrical drives enables more versatile chassis dynamometer setups with better accuracy at a reduced cost. We are developing a new chassis dynamometer laboratory for vehicle research, aiming at extending a recently commercially available dynamometer, building a new laboratory around it, and applying the resulting facility to some new challenging vehicle research problems. The projects are enabled on one hand by collaboration with the dynamometer manufacturer, and on the other hand on collaboration with automotive industry allowing access to relevant internal information and equipment. The test modes of the chassis dynamometer are under development in a joint collaboration with the manufacturer. The laboratory has been operational since September 2011 and has already been used for NVH-analysis for a tire pressure indication application, chassis dynamometer road force co-simulation with a moving base simulator, co-surge modeling and control for a 6-cylinder bi-turbo engine, and traditional engine mapping. We are also looking at projects with focus on look-ahead control, as well as clutch and transmission modeling and control, and driving cycle related research.

  • 8902.
    Ödlund, Erika
    Linköping University, Department of Electrical Engineering.
    Virtual instrumentation: Introduction of virtual2007Independent thesis Basic level (professional degree), 20 points / 30 hpStudent thesis
    Abstract [en]

    The Large Hadron Collider (LHC) is the next large particle accelerator developed at CERN, constructed to enable studies of particles. The acceleration of the particles is carried out using magnets operating at about 1.9 K, a temperature achieved by regulating flow of superfluid helium. For economical reasons, control of the helium flow is based on feedback of virtual flow meter (VFT) estimates instead of real instrumentation.

    The main purpose of this work is to develop a virtual flow meter with the possibility to estimate the flow by means of two different flow estimation methods; the Samson method that has previously been tested for the LHC, and the Sereg- Schlumberger method that has never before been implemented in this environment.

    The virtual flow meters are implemented on PLCs using temperature and pressure measurements as input data, and a tool for generating the virtual flow meters and connect them to the appropriate physical instrumentation has also been developed.

    The flow through a valve depends, among others, on some pressure and temperature dependent physical properties that are to be estimated with high accuracy. In this project, this is done by bilinear interpolation in twodimensional tables containing physical data, an approach that turned out to be more accurate than the previously used method with polynomial interpolation.

    The flow measurement methods have been compared. Since they both derive from empirical studies rather than physical relations it is quite futile to find theoretical correspondencies, but the simulations of the mass flows can be compared. For low pressures, the results are fairly equal but they differ more for higher pressures. The methods have not been validated against true flow rates since there were no real measurements available before the end of this project.

  • 8903.
    Öfjäll, Kristoffer
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, Faculty of Science & Engineering.
    Adaptive Supervision Online Learning for Vision Based Autonomous Systems2016Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Driver assistance systems in modern cars now show clear steps towards autonomous driving and improvements are presented in a steady pace. The total number of sensors has also decreased from the vehicles of the initial DARPA challenge, more resembling a pile of sensors with a car underneath. Still, anyone driving a tele-operated toy using a video link is a demonstration that a single camera provides enough information about the surronding world.  

    Most lane assist systems are developed for highway use and depend on visible lane markers. However, lane markers may not be visible due to snow or wear, and there are roads without lane markers. With a slightly different approach, autonomous road following can be obtained on almost any kind of road. Using realtime online machine learning, a human driver can demonstrate driving on a road type unknown to the system and after some training, the system can seamlessly take over. The demonstrator system presented in this work has shown capability of learning to follow different types of roads as well as learning to follow a person. The system is based solely on vision, mapping camera images directly to control signals.  

    Such systems need the ability to handle multiple-hypothesis outputs as there may be several plausible options in similar situations. If there is an obstacle in the middle of the road, the obstacle can be avoided by going on either side. However the average action, going straight ahead, is not a viable option. Similarly, at an intersection, the system should follow one road, not the average of all roads.  

    To this end, an online machine learning framework is presented where inputs and outputs are represented using the channel representation. The learning system is structurally simple and computationally light, based on neuropsychological ideas presented by Donald Hebb over 60 years ago. Nonetheless the system has shown a cabability to learn advanced tasks. Furthermore, the structure of the system permits a statistical interpretation where a non-parametric representation of the joint distribution of input and output is generated. Prediction generates the conditional distribution of the output, given the input.  

    The statistical interpretation motivates the introduction of priors. In cases with multiple options, such as at intersections, a prior can select one mode in the multimodal distribution of possible actions. In addition to the ability to learn from demonstration, a possibility for immediate reinforcement feedback is presented. This allows for a system where the teacher can choose the most appropriate way of training the system, at any time and at her own discretion.  

    The theoretical contributions include a deeper analysis of the channel representation. A geometrical analysis illustrates the cause of decoding bias commonly present in neurologically inspired representations, and measures to counteract it. Confidence values are analyzed and interpreted as evidence and coherence. Further, the use of the truncated cosine basis function is motivated.  

    Finally, a selection of applications is presented, such as autonomous road following by online learning and head pose estimation. A method founded on the same basic principles is used for visual tracking, where the probabilistic representation of target pixel values allows for changes in target appearance.

  • 8904.
    Öfjäll, Kristoffer
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, The Institute of Technology.
    LEAP, A Platform for Evaluation of Control Algorithms2010Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Most people are familiar with the BRIO labyrinth game and the challenge of guiding the ball through the maze. The goal of this project was to use this game to create a platform for evaluation of control algorithms. The platform was used to evaluate a few different controlling algorithms, both traditional automatic control algorithms as well as algorithms based on online incremental learning.

    The game was fitted with servo actuators for tilting the maze. A camera together with computer vision algorithms were used to estimate the state of the game. The evaluated controlling algorithm had the task of calculating a proper control signal, given the estimated state of the game.

    The evaluated learning systems used traditional control algorithms to provide initial training data. After initial training, the systems learned from their own actions and after a while they outperformed the controller used to provide initial training.

  • 8905.
    Öfjäll, Kristoffer
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, The Institute of Technology.
    Online Learning for Robot Vision2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In tele-operated robotics applications, the primary information channel from the robot to its human operator is a video stream. For autonomous robotic systems however, a much larger selection of sensors is employed, although the most relevant information for the operation of the robot is still available in a single video stream. The issue lies in autonomously interpreting the visual data and extracting the relevant information, something humans and animals perform strikingly well. On the other hand, humans have great diculty expressing what they are actually looking for on a low level, suitable for direct implementation on a machine. For instance objects tend to be already detected when the visual information reaches the conscious mind, with almost no clues remaining regarding how the object was identied in the rst place. This became apparent already when Seymour Papert gathered a group of summer workers to solve the computer vision problem 48 years ago [35].

    Articial learning systems can overcome this gap between the level of human visual reasoning and low-level machine vision processing. If a human teacher can provide examples of what to be extracted and if the learning system is able to extract the gist of these examples, the gap is bridged. There are however some special demands on a learning system for it to perform successfully in a visual context. First, low level visual input is often of high dimensionality such that the learning system needs to handle large inputs. Second, visual information is often ambiguous such that the learning system needs to be able to handle multi modal outputs, i.e. multiple hypotheses. Typically, the relations to be learned  are non-linear and there is an advantage if data can be processed at video rate, even after presenting many examples to the learning system. In general, there seems to be a lack of such methods.

    This thesis presents systems for learning perception-action mappings for robotic systems with visual input. A range of problems are discussed, such as vision based autonomous driving, inverse kinematics of a robotic manipulator and controlling a dynamical system. Operational systems demonstrating solutions to these problems are presented. Two dierent approaches for providing training data are explored, learning from demonstration (supervised learning) and explorative learning (self-supervised learning). A novel learning method fullling the stated demands is presented. The method, qHebb, is based on associative Hebbian learning on data in channel representation. Properties of the method are demonstrated on a vision-based autonomously driving vehicle, where the system learns to directly map low-level image features to control signals. After an initial training period, the system seamlessly continues autonomously. In a quantitative evaluation, the proposed online learning method performed comparably with state of the art batch learning methods.

    List of papers
    1. Autonomous Navigation and Sign Detector Learning
    Open this publication in new window or tab >>Autonomous Navigation and Sign Detector Learning
    Show others...
    2013 (English)In: IEEE Workshop on Robot Vision(WORV) 2013, IEEE , 2013, p. 144-151Conference paper, Published paper (Refereed)
    Abstract [en]

    This paper presents an autonomous robotic system that incorporates novel Computer Vision, Machine Learning and Data Mining algorithms in order to learn to navigate and discover important visual entities. This is achieved within a Learning from Demonstration (LfD) framework, where policies are derived from example state-to-action mappings. For autonomous navigation, a mapping is learnt from holistic image features (GIST) onto control parameters using Random Forest regression. Additionally, visual entities (road signs e.g. STOP sign) that are strongly associated to autonomously discovered modes of action (e.g. stopping behaviour) are discovered through a novel Percept-Action Mining methodology. The resulting sign detector is learnt without any supervision (no image labeling or bounding box annotations are used). The complete system is demonstrated on a fully autonomous robotic platform, featuring a single camera mounted on a standard remote control car. The robot carries a PC laptop, that performs all the processing on board and in real-time.

    Place, publisher, year, edition, pages
    IEEE, 2013
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-86214 (URN)10.1109/WORV.2013.6521929 (DOI)978-1-4673-5647-3 (ISBN)978-1-4673-5646-6 (ISBN)
    Conference
    IEEE Workshop on Robot Vision (WORV 2013), 15-17 January 2013, Clearwater Beach, FL, USA
    Projects
    ELLIITETTCUASUK EPSRC: EP/H023135/1
    Available from: 2012-12-11 Created: 2012-12-11 Last updated: 2016-06-14
    2. Online Learning of Vision-Based Robot Control during Autonomous Operation
    Open this publication in new window or tab >>Online Learning of Vision-Based Robot Control during Autonomous Operation
    2015 (English)In: New Development in Robot Vision / [ed] Yu Sun, Aman Behal and Chi-Kit Ronald Chung, Springer Berlin/Heidelberg, 2015, p. 137-156Chapter in book (Refereed)
    Abstract [en]

    Online learning of vision-based robot control requires appropriate activation strategies during operation. In this chapter we present such a learning approach with applications to two areas of vision-based robot control. In the first setting, selfevaluation is possible for the learning system and the system autonomously switches to learning mode for producing the necessary training data by exploration. The other application is in a setting where external information is required for determining the correctness of an action. Therefore, an operator provides training data when required, leading to an automatic mode switch to online learning from demonstration. In experiments for the first setting, the system is able to autonomously learn the inverse kinematics of a robotic arm. We propose improvements producing more informative training data compared to random exploration. This reduces training time and limits learning to regions where the learnt mapping is used. The learnt region is extended autonomously on demand. In experiments for the second setting, we present an autonomous driving system learning a mapping from visual input to control signals, which is trained by manually steering the robot. After the initial training period, the system seamlessly continues autonomously. Manual control can be taken back at any time for providing additional training.

    Place, publisher, year, edition, pages
    Springer Berlin/Heidelberg, 2015
    Series
    Cognitive Systems Monographs, ISSN 1867-4925 ; Vol. 23
    National Category
    Computer Vision and Robotics (Autonomous Systems)
    Identifiers
    urn:nbn:se:liu:diva-110891 (URN)10.1007/978-3-662-43859-6_8 (DOI)978-3-662-43858-9 (ISBN)978-3-662-43859-6 (ISBN)
    Available from: 2014-09-26 Created: 2014-09-26 Last updated: 2018-01-11Bibliographically approved
    3. Biologically Inspired Online Learning of Visual Autonomous Driving
    Open this publication in new window or tab >>Biologically Inspired Online Learning of Visual Autonomous Driving
    2014 (English)In: Proceedings British Machine Vision Conference 2014 / [ed] Michel Valstar; Andrew French; Tony Pridmore, BMVA Press , 2014, p. 137-156Conference paper, Published paper (Refereed)
    Abstract [en]

    While autonomously driving systems accumulate more and more sensors as well as highly specialized visual features and engineered solutions, the human visual system provides evidence that visual input and simple low level image features are sufficient for successful driving. In this paper we propose extensions (non-linear update and coherence weighting) to one of the simplest biologically inspired learning schemes (Hebbian learning). We show that this is sufficient for online learning of visual autonomous driving, where the system learns to directly map low level image features to control signals. After the initial training period, the system seamlessly continues autonomously. This extended Hebbian algorithm, qHebb, has constant bounds on time and memory complexity for training and evaluation, independent of the number of training samples presented to the system. Further, the proposed algorithm compares favorably to state of the art engineered batch learning algorithms.

    Place, publisher, year, edition, pages
    BMVA Press, 2014
    National Category
    Computer Vision and Robotics (Autonomous Systems)
    Identifiers
    urn:nbn:se:liu:diva-110890 (URN)10.5244/C.28.94 (DOI)1901725529 (ISBN)
    Conference
    British Machine Vision Conference 2014, Nottingham, UK September 1-5 2014
    Note

    The video contains the online learning autonomous driving system in operation. Data from the system has been synchronized with the video and is shown overlaid. The actuated steering singnal is visualized as the position of a blue dot. The steering signal predicted by the system is visualized by a green circle. During autonomous operation, these two coincide. When the vehicle is controlled manually (training), the word MANUAL is displayed in the video.The first sequence evaluates the ability of the system to stay on the road during road reconfiguration. The results of the first sequence indicate that the system primarily reacts to features on the road, not features in the surrounding area. The second sequence evaluates the multi-modal abilities of the system. After initial training, the vehicle follows the outer track, going straight in the two three-way junctions. By forcing the vehicle to turn right at one intersection, by means of a short application of manual control, a new mode is introduced. When the system later reaches the same intersection, the vehicle either turns or continues straight ahead depending on which of the two modes is the strongest. The ordering of the modes depends on slight variation in the approach to the junction and on noise.The third sequence is longer, evaluating both multi-modal abilities and effects of track reconfiguration. Container: MP4Codec: h264 1280x720

    Available from: 2014-09-26 Created: 2014-09-26 Last updated: 2018-01-11Bibliographically approved
    4. Combining Vision, Machine Learning and Automatic Control to Play the Labyrinth Game
    Open this publication in new window or tab >>Combining Vision, Machine Learning and Automatic Control to Play the Labyrinth Game
    2012 (English)In: Proceedings of SSBA, Swedish Symposium on Image Analysis, 2012, 2012Conference paper, Published paper (Other academic)
    Abstract [en]

    The labyrinth game is a simple yet challenging platform, not only for humans but also for control algorithms and systems. The game is easy to understand but still very hard to master. From a system point of view, the ball behavior is in general easy to model but close to the obstacles there are severe non-linearities. Additionally, the far from flat surface on which the ball rolls provides for changing dynamics depending on the ball position.

    The general dynamics of the system can easily be handled by traditional automatic control methods. Taking the obstacles and uneven surface into account would require very detailed models of the system. A simple deterministic control algorithm is combined with a learning control method. The simple control method provides initial training data. As thelearning method is trained, the system can learn from the results of its own actions and the performance improves well beyond the performance of the initial controller.

    A vision system and image analysis is used to estimate the ball position while a combination of a PID controller and a learning controller based on LWPR is used to learn to steer the ball through the maze.

    National Category
    Computer Vision and Robotics (Autonomous Systems)
    Identifiers
    urn:nbn:se:liu:diva-110888 (URN)
    Conference
    Swedish Symposium on Image Analysis for 2012, March 8-9, Stockholm, Sweden
    Available from: 2014-09-26 Created: 2014-09-26 Last updated: 2018-01-11Bibliographically approved
  • 8906.
    Öfjäll, Kristoffer
    et al.
    Visionists AB, Gothenburg, Sweden.
    Felsberg, Michael
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, Faculty of Science & Engineering.
    Approximative Coding Methods for Channel Representations2018In: Journal of Mathematical Imaging and Vision, ISSN 0924-9907, E-ISSN 1573-7683, Vol. 60, no 6, p. 929-940Article in journal (Refereed)
    Abstract [en]

    Most methods that address computer vision prob-lems require powerful visual features. Many successfulapproaches apply techniques motivated from nonparametricstatistics. The channel representation provides a frameworkfornonparametricdistributionrepresentation.Althoughearlywork has focused on a signal processing view of the rep-resentation, the channel representation can be interpretedin probabilistic terms, e.g., representing the distribution oflocal image orientation. In this paper, a variety of approxi-mative channel-based algorithms for probabilistic problemsare presented: a novel efficient algorithm for density recon-struction, a novel and efficient scheme for nonlinear griddingof densities, and finally a novel method for estimating Copuladensities. The experimental results provide evidence that byrelaxing the requirements for exact solutions, efficient algo-rithms are obtained

  • 8907.
    Öfjäll, Kristoffer
    et al.
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, The Institute of Technology.
    Felsberg, Michael
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Biologically Inspired Online Learning of Visual Autonomous Driving2014In: Proceedings British Machine Vision Conference 2014 / [ed] Michel Valstar; Andrew French; Tony Pridmore, BMVA Press , 2014, p. 137-156Conference paper (Refereed)
    Abstract [en]

    While autonomously driving systems accumulate more and more sensors as well as highly specialized visual features and engineered solutions, the human visual system provides evidence that visual input and simple low level image features are sufficient for successful driving. In this paper we propose extensions (non-linear update and coherence weighting) to one of the simplest biologically inspired learning schemes (Hebbian learning). We show that this is sufficient for online learning of visual autonomous driving, where the system learns to directly map low level image features to control signals. After the initial training period, the system seamlessly continues autonomously. This extended Hebbian algorithm, qHebb, has constant bounds on time and memory complexity for training and evaluation, independent of the number of training samples presented to the system. Further, the proposed algorithm compares favorably to state of the art engineered batch learning algorithms.

  • 8908.
    Öfjäll, Kristoffer
    et al.
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, The Institute of Technology.
    Felsberg, Michael
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Combining Vision, Machine Learning and Automatic Control to Play the Labyrinth Game2012In: Proceedings of SSBA, Swedish Symposium on Image Analysis, 2012, 2012Conference paper (Other academic)
    Abstract [en]

    The labyrinth game is a simple yet challenging platform, not only for humans but also for control algorithms and systems. The game is easy to understand but still very hard to master. From a system point of view, the ball behavior is in general easy to model but close to the obstacles there are severe non-linearities. Additionally, the far from flat surface on which the ball rolls provides for changing dynamics depending on the ball position.

    The general dynamics of the system can easily be handled by traditional automatic control methods. Taking the obstacles and uneven surface into account would require very detailed models of the system. A simple deterministic control algorithm is combined with a learning control method. The simple control method provides initial training data. As thelearning method is trained, the system can learn from the results of its own actions and the performance improves well beyond the performance of the initial controller.

    A vision system and image analysis is used to estimate the ball position while a combination of a PID controller and a learning controller based on LWPR is used to learn to steer the ball through the maze.

  • 8909.
    Öfjäll, Kristoffer
    et al.
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, The Institute of Technology.
    Felsberg, Michael
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Integrating Learning and Optimization for Active Vision Inverse Kinematics2013In: Proceedings of SSBA, Swedish Symposium on Image Analysis, 2013, 2013Conference paper (Other academic)
  • 8910.
    Öfjäll, Kristoffer
    et al.
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, The Institute of Technology.
    Felsberg, Michael
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Online Learning and Mode Switching for Autonomous Driving from Demonstration2014In: Proceedings of SSBA, Swedish Symposium on Image Analysis, 2014, 2014Conference paper (Other academic)
  • 8911.
    Öfjäll, Kristoffer
    et al.
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, Faculty of Science & Engineering.
    Felsberg, Michael
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, Faculty of Science & Engineering.
    Online learning of autonomous driving using channel representations of multi-modal joint distributions2015In: Proceedings of SSBA, Swedish Symposium on Image Analysis, 2015, Swedish Society for automated image analysis , 2015Conference paper (Other academic)
  • 8912.
    Öfjäll, Kristoffer
    et al.
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, The Institute of Technology.
    Felsberg, Michael
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, The Institute of Technology.
    Online Learning of Vision-Based Robot Control during Autonomous Operation2015In: New Development in Robot Vision / [ed] Yu Sun, Aman Behal and Chi-Kit Ronald Chung, Springer Berlin/Heidelberg, 2015, p. 137-156Chapter in book (Refereed)
    Abstract [en]

    Online learning of vision-based robot control requires appropriate activation strategies during operation. In this chapter we present such a learning approach with applications to two areas of vision-based robot control. In the first setting, selfevaluation is possible for the learning system and the system autonomously switches to learning mode for producing the necessary training data by exploration. The other application is in a setting where external information is required for determining the correctness of an action. Therefore, an operator provides training data when required, leading to an automatic mode switch to online learning from demonstration. In experiments for the first setting, the system is able to autonomously learn the inverse kinematics of a robotic arm. We propose improvements producing more informative training data compared to random exploration. This reduces training time and limits learning to regions where the learnt mapping is used. The learnt region is extended autonomously on demand. In experiments for the second setting, we present an autonomous driving system learning a mapping from visual input to control signals, which is trained by manually steering the robot. After the initial training period, the system seamlessly continues autonomously. Manual control can be taken back at any time for providing additional training.

  • 8913.
    Öfjäll, Kristoffer
    et al.
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, The Institute of Technology.
    Felsberg, Michael
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Weighted Update and Comparison for Channel-Based Distribution Field Tracking2015In: COMPUTER VISION - ECCV 2014 WORKSHOPS, PT II, Springer, 2015, Vol. 8926, p. 218-231Conference paper (Refereed)
    Abstract [en]

    There are three major issues for visual object trackers: modelrepresentation, search and model update. In this paper we address thelast two issues for a specic model representation, grid based distributionmodels by means of channel-based distribution elds. Particularly weaddress the comparison part of searching. Previous work in the areahas used standard methods for comparison and update, not exploitingall the possibilities of the representation. In this work we propose twocomparison schemes and one update scheme adapted to the distributionmodel. The proposed schemes signicantly improve the accuracy androbustness on the Visual Object Tracking (VOT) 2014 Challenge dataset.

  • 8914.
    Öfjäll, Kristoffer
    et al.
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, Faculty of Science & Engineering.
    Felsberg, Michael
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, Faculty of Science & Engineering. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Robinson, Andreas
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, Faculty of Science & Engineering.
    Visual Autonomous Road Following by Symbiotic Online Learning2016In: Intelligent Vehicles Symposium (IV), 2016 IEEE, 2016, p. 136-143Conference paper (Refereed)
    Abstract [en]

    Recent years have shown great progress in driving assistance systems, approaching autonomous driving step by step. Many approaches rely on lane markers however, which limits the system to larger paved roads and poses problems during winter. In this work we explore an alternative approach to visual road following based on online learning. The system learns the current visual appearance of the road while the vehicle is operated by a human. When driving onto a new type of road, the human driver will drive for a minute while the system learns. After training, the human driver can let go of the controls. The present work proposes a novel approach to online perception-action learning for the specific problem of road following, which makes interchangeably use of supervised learning (by demonstration), instantaneous reinforcement learning, and unsupervised learning (self-reinforcement learning). The proposed method, symbiotic online learning of associations and regression (SOLAR), extends previous work on qHebb-learning in three ways: priors are introduced to enforce mode selection and to drive learning towards particular goals, the qHebb-learning methods is complemented with a reinforcement variant, and a self-assessment method based on predictive coding is proposed. The SOLAR algorithm is compared to qHebb-learning and deep learning for the task of road following, implemented on a model RC-car. The system demonstrates an ability to learn to follow paved and gravel roads outdoors. Further, the system is evaluated in a controlled indoor environment which provides quantifiable results. The experiments show that the SOLAR algorithm results in autonomous capabilities that go beyond those of existing methods with respect to speed, accuracy, and functionality. 

  • 8915.
    Öfjäll, Kristoffer
    et al.
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, The Institute of Technology.
    Michael, Felsberg
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, The Institute of Technology.
    Rapid Explorative Direct Inverse Kinematics Learning of Relevant Locations for Active Vision2013In: IEEE Workshop on Robot Vision(WORV) 2013, IEEE conference proceedings, 2013, p. 14-19Conference paper (Refereed)
    Abstract [en]

    An online method for rapidly learning the inverse kinematics of a redundant robotic arm is presented addressing the special requirements of active vision for visual inspection tasks. The system is initialized with a model covering a small area around the starting position, which is then incrementally extended by exploration. The number of motions during this process is minimized by only exploring configurations required for successful completion of the task at hand. The explored area is automatically extended online and on demand.To achieve this, state of the art methods for learning and numerical optimization are combined in a tight implementation where parts of the learned model, the Jacobians, are used during optimization, resulting in significant synergy effects. In a series of standard experiments, we show that the integrated method performs better than using both methods sequentially.

  • 8916.
    Öhlin, Andreas
    Linköping University, Department of Electrical Engineering, Computer Engineering. Linköping University, Faculty of Science & Engineering.
    Real-Time Multi-Dimensional Fast Fourier Transforms on FPGAs2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis presents a way of performing multi dimensional FFT in a continuousflow environment by calculating the FFT of each dimension separately ina pipeline. The result is a three dimensional pipelined FFT implemented on aStratix III FPGA. It can calculate the three dimensional FFT of a data set containing2563 samples with a word size of 32 bits. The biggest challenge and themain part of the work are the data permutations in between the one dimensionalFFT modules, this part of the design make use of an external DDR2 SDRAMas well as on-chip BRAM to store and permute data between the modules. Theevaluations show that the design is hardware efficient and the latency is relativelylow and determined to be 84.2 ms.

  • 8917.
    Öhman, Andreas
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems.
    Jonsson, Oskar
    Linköping University, Department of Electrical Engineering, Vehicular Systems.
    Simulering och implementering av ett elektriskt motorsystem för minimering av hastighetvariationer2018Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Syftet med examensarbetet är att utse en lämplig ersättare för en motor i en av Saab Dynamics produkter. Den tidigare motorn är en synkronmotor av typen hysteresmotor och nu söks en billigare lösning med liknande prestanda. Applikationen kräver att motorn från stillastående ska kunna accelereras till 600 varv per minut på maximalt 0,5 sekunder. Efter 0,5 sekunder ska medelhastigheten per varv maximalt avvika med 0,2 promille. I utveckling av en ny lösning ingår val av motortyp, styrelektronik och givare samt design av regleralgoritmer. I rapporten beskrivs ett antal motorer som kan vara lämpliga ersättare till den tidigare motorn samt deras styrkor och svagheter. Sedan följer en undersökning och implementation av en av de lämpliga kandidaterna, en borstlös likströmsmotor. Val av givare och styrteknik för den motortypen beskrivs och motorns lämplighet undersöks i en modell skapad i Mathworks Simulinkmiljö där ett reglersystem implementeras. Simuleringar visa att den valda motorn är lämplig för en praktisk implementation. Slutligen beskrivs konstruktionen av en testuppställning som innefattar motor, givare och styrteknik implementerad i en processor som ställer ut strömmen till motorn för att uppnå önskad hastighet. Uppställningen uppfyller kravet i testkörningar och i den bästa körningen är hastighetsvariationerna 7,4 gånger mindre än det specificerade kravet.

  • 8918.
    Öhman, Fredrik
    Linköping University, Department of Electrical Engineering.
    Modulgenerator för Matchade Transistorpar2005Independent thesis Basic level (professional degree)Student thesis
    Abstract [sv]

    Detta examensarbete syftar till att implementera en modulgenerator som automatiskt genererar ett matchat differentialpar. Detta för att enkelt kunna generera detta vanlig förekommande byggblock utan att behöva rita om allt från grunden.

    Modulgeneratorn som konstruerats klarar att skapa upp till 2x2 transistor block matchad layout med eller utan sköld. Programmet skapar med hjälp av indata från konstruktören en skräddarsydd layout som kan användas som byggblock i integrerade kretsar.

    Examensarbetet är slutfört och har genomgått omfattande testning

    The aim of this thesis is to implement a module generator that automatically generates a matched differential pair. That is, to easily create new pairs without having to draw everything from scratch.

    The module generator is able to create matched layouts with up to 2x2 transistor blocks with or without a guard-ring. The program uses a number of input parameters from the user to customize the layout. Hence, the generated blocks can be used in a large range of analog integrated circuits.

  • 8919.
    Öhr, Jonas
    et al.
    ABB, Sweden.
    Moberg, Stig
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Wernholt, Erik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Hanssen, Sven
    ABB, Sweden.
    Pettersson, Jens
    ABB, Sweden.
    Persson, Sofie
    ABB, Sweden.
    Sander-Tavallaey, Shiva
    ABB, Sweden.
    Identification of Flexibility Parameters of 6-axis Industrial Manipulator Models2006In: Proceedings of the 2006 International Conference on Noise and Vibration Engineering, 2006, p. 3305-Conference paper (Refereed)
    Abstract [en]

    A method for identification of flexibility parameters of a 18 DOF (degrees offreedom) robot prototype model is proposed. Experiments show the strengthof the method and the results indicates that flexibilities in the bearings and thearms, taken together, are of the same order as the flexibilities in the gears.

  • 8920.
    Öhr, Jonas
    et al.
    ABB, Sweden.
    Moberg, Stig
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Wernholt, Erik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Hanssen, Sven
    ABB, Sweden.
    Pettersson, Jens
    ABB, Sweden.
    Persson, Sofie
    ABB, Sweden.
    Sander-Tavallaey, Shiva
    ABB, Sweden.
    Identification of Flexibility Parameters of 6-axis Industrial Manipulator Models2006Report (Other academic)
    Abstract [en]

    A method for identification of flexibility parameters of a 18 DOF (degrees offreedom) robot prototype model is proposed. Experiments show the strengthof the method and the results indicates that flexibilities in the bearings and thearms, taken together, are of the same order as the flexibilities in the gears.

  • 8921.
    Öhrn, Philip
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control.
    Åstrand, Markus
    Linköping University, Department of Electrical Engineering, Automatic Control.
    Direct Lift Control of Fighter Aircraft2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Direct lift control for aircraft has been around in the aeronautical industry for decades but is mainly used in commercial aircraft with dedicated direct lift control surfaces. The focus of this thesis is to investigate if direct lift control is feasible for a fighter aircraft, similar to Saab JAS 39 Gripen, without dedicated control surfaces.

    The modelled system is an aircraft that is inherently unstable and contains nonlinearities both in its aerodynamics and in the form of limited control surface deflection and deflection rates. The dynamics of the aircraft are linearised around a flight case representative of a landing scenario. Direct lift control is then applied to give a more immediate relation from pilot stick input to change in flight path angle while also preserving the pitch attitude.

    Two different control strategies, linear quadratic control and model predictive control, were chosen for the implementation. Since fighter aircraft are systems with fast dynamics it was important to limit the computational time. This constraint motivated the use of specialised methods to speed up the optimisation of the model predictive controller.

    Results from simulations in a nonlinear simulation environment supplied by Saab, as well as tests in high-fidelity flight simulation rigs with a pilot, proved that direct lift control is feasible for the investigated fighter aircraft. Sufficient control authority and performance when controlling the flight path angle were observed. Both developed controllers have their own advantages and which strategy is the most suitable depends on what the user prioritises. Pilot workload during landing as well as precision at touch down were deemed similar to conventional control.

  • 8922.
    Öijerholm, Mikael
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, Department of Electrical Engineering.
    Aspects of the choice of sampling frequency in the control system of a gas turbine2009Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    At Siemens, plcs are used to control the gas turbines, and to execute the code in the plcs cyclic interrupts are used. If the execution time for the interrupt becomes close to the cyclic time of the interrupt the load of the plc increases. High load levels can lead to situations were segments of code are not executed on time or even not executed at all. In this thesis an analysis of the regulators used to govern a gas turbine has been performed. The purpose of the analysis is to study the performance of the regulators for different cycle times with the aim to be able to reduce the load by sampling more slowly.

    To determine the load contribution from each regulator a review of the regulators and their execution times has been made. For the analysis the Matlab program Simulink has been used to make models of the regulators, which have then been sampled at different rates. With this information it is possible to determine for which cycle times each regulator has accepetable performance and how much load each regulator contributes with. A save of load of approximately 2 percent can be obtained without loosing too much performance.

  • 8923.
    Öjerteg, Theo
    Linköping University, Department of Electrical Engineering.
    Design and implementation of test a tool for the GSM traffic channel.2002Independent thesis Basic level (professional degree)Student thesis
    Abstract [en]

    Todays’ systems for telecommunication are getting more and more complex. Automatic testing is required to guarantee quality of the systems produced. An actual example is the introduction of GPRS traffic in the GSM network nodes. This thesis investigates the need and demands for such an automatic testing of the traffic channels in the GSM system. A solution intended to be a part of the Ericsson TSS is proposed. One problem to be solved is that today’s tools for testing do not support testing of speech channels with the speech transcoder unit installed. As part of the investigation, a speech codec is implemented for execution on current hardware used in the test platform. The selected speech codec is the enhanced full rate codec, generating a bitstream of 12.2 kbit/s, and gives a good trade-off between compression and speech quality. The report covers the design of the test tool and the implementation of speech codec. Particularly performance problems in the implementation of the encoder will be addressed.

  • 8924.
    Önnegren, Anna
    Linköping University, Department of Electrical Engineering.
    Feldetektering för diagnos med differentialgeometriska metoder -en implementering i Mathematica2004Independent thesis Basic level (professional degree)Student thesis
    Abstract [en]

    Diagnosis means detection and isolation of faults. A model based diagnosis system is built on a mathematical model of the system. The difficulty when constructing the diagnosis system depends om how the model is formulated. In this report, a method is described that rewrites the model on such a form that the construction of the diagnosis algoritm is easy. The model is transformed by two state space transformations and the result will be a system on state space form where one part of the system becomes easy to supervise.

    The main part of the report describes the procedure to create these transformations, which can be done in seven steps, based on differential geometric methods.

    The aim of this masters thesis was to create an implementation in Mathematica (a computer tool for symbolic formula manipulation) of the creation of the two transformations and the system transformation. The created functions are described and examples of these are given.

    A further aim was to evaluate if Mathematica could be a good support to rewrit a model. This was done by studying examples, and on the basis of the examples, identify difficult and easy steps.

    The program has shown to be a good aid. Two of the seven steps have been identified as difficult and proposals for improvements have been given.

  • 8925.
    Öresjö, Per
    Linköping University, Department of Electrical Engineering.
    A High Speed Sigma Delta A/D-Converter for a General Purpose RF Front End in 90nm-Technology2007Independent thesis Basic level (professional degree), 20 points / 30 hpStudent thesis
    Abstract [en]

    In this report a transistor-level design of a GHz Sigma-Delta analog-to-digital converter for an RF front end is proposed. The design is current driven, where the integration is done directly over two capacitances and it contains no operational amplifiers.

    The clock frequency used for verification was 2.5 GHz and the output band-width was 10 MHz. The system is flexible in that the number of internal bits can be scaled easily and in this report a three-bit system yielding an SNR of 76.5 dB as well as a four-bit system yielding an SNR of 82.5 dB are analyzed.

  • 8926.
    Örn, Daniel
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, Faculty of Science & Engineering.
    Szilassy, Martin
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, Faculty of Science & Engineering.
    Dil, Bram
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, Faculty of Science & Engineering.
    Gustafsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, Faculty of Science & Engineering.
    A Novel Multi-Step Algorithm for Low-Energy Positioning Using GPS2016In: Fusion 2016, 19th International Conference on Information Fusion: Proceedings, 2016, p. 1469-1476Conference paper (Refereed)
    Abstract [en]

    GPS is widely used for localization and tracking, however traditional GPS receivers consume too much energy for many applications. This paper implements and evaluates the performance of a low-energy GPS prototype. The main difference is that a traditional GPS needs to sample signals transmitted by satellites for 30 seconds to estimate its position. Our prototype reduces this time by three orders of magnitude and it can compute positions from only 2 milliseconds of data. We present a new algorithm that increases robustness by filtering on estimated residuals instead of using an altitude database. In addition, we show that our new algorithm works with both fixed and moving targets. The solution consists of (1) a portable device that samples the GPS signal and (2) a server that utilizes Doppler navigation and Coarse Time Navigation to estimate positions. We performed tests in a wide variety of environments and situations. These tests show that our prototype provides a median positioning error of roughly 40 meters even when the GPS receiver is moving at 80 kilometres per hour.

  • 8927.
    Örn, Sara
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Realistic Multi-Cell Interference Coordination in 4G/LTE2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In the LTE mobile system, all cells use the same set of frequencies. This means that a user could experience interference from other cells. A method that has been studied in order to reduce this interference and thereby increase data rate or system throughput is to coordinate scheduling between cells. Good results of this have been found in different studies. However, the interference is generally assumed to be known. Studies using estimated interference and simulating more than one cluster of cells have found almost no gain.

    This thesis will focus on how to use information from coordinated scheduling and other traffic estimates to do better interference estimation and link adaption. The suggested method is to coordinate larger clusters and use the coordination information, as well as estimates of which cells will be transmitting, to make estimates of interference from other cells. The additional information from interference estimation is used in the link adaptation. Limitations in bandwidth of the backhaul needed to send data between cells are considered, as well as the delay it may introduce. A limitation of the scope is that MIMO or HetNet scenarios have not been simulated.

    The suggested method for interference estimation and link adaptation have been implemented and simulated in a system simulator. The method gives a less biased estimate of SINR, but there are no gains in user bit rate. The lesser bias is since the method is better at predicting high SINR than the base estimate is. The lack of gains regarding user bit rate may result from the fact that in the studied scenarios, users where not able to make use of the higher estimated SINR since the base estimate is already high.

    The conclusion is that the method might be useful in scenarios where there are not full load, but the users either have bad channel quality or are able to make use of very high SINR. Such scenarios could be HetNet or MIMO scenarios, respectively.

  • 8928.
    Örtenberg, Alexander
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Parallelization of DIRA and CTmod Using OpenMP and OpenCL2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Parallelization is the answer to the ever-growing demands of computing power by taking advantage of multi-core processor technology and modern many-core graphics compute units. Multi-core CPUs and many-core GPUs have the potential to substantially reduce the execution time of a program but it is often a challenging task to ensure that all available hardware is utilized. OpenMP and OpenCL are two parallel programming frameworks that have been developed to allow programmers to focus on high-level parallelism rather than dealing with low-level thread creation and management. This thesis applies these frameworks to the area of computed tomography by parallelizing the image reconstruction algorithm DIRA and the photon transport simulation toolkit CTmod. DIRA is a model-based iterative reconstruction algorithm in dual-energy computed tomography, which has the potential to improve the accuracy of dose planning in radiation therapy. CTmod is a toolkit for simulating primary and scatter projections in computed tomography to optimize scanner design and image reconstruction algorithms. The results presented in this thesis show that parallelization combined with computational optimization substantially decreased execution times of these codes. For DIRA the execution time was reduced from two minutes to just eight seconds when using four iterations and a 16-core CPU so a speedup of 15 was achieved. CTmod produced similar results with a speedup of 14 when using a 16-core CPU. The results also showed that for these particular problems GPU computing was not the best solution.

  • 8929.
    Örtenberg, Alexander
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Medicine and Health Sciences.
    Magnusson, Maria
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Science & Engineering. Linköping University, Faculty of Medicine and Health Sciences.
    Sandborg, Michael
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Alm Carlsson, Gudrun
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Malusek, Alexandr
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences.
    PARALLELISATION OF THE MODEL-BASED ITERATIVE RECONSTRUCTION ALGORITHM DIRA2016In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 169, no 1-4, p. 405-409Article in journal (Refereed)
    Abstract [en]

    New paradigms for parallel programming have been devised to simplify software development on multi-core processors and many-core graphical processing units (GPU). Despite their obvious benefits, the parallelisation of existing computer programs is not an easy task. In this work, the use of the Open Multiprocessing (OpenMP) and Open Computing Language (OpenCL) frameworks is considered for the parallelisation of the model-based iterative reconstruction algorithm DIRA with the aim to significantly shorten the code’s execution time. Selected routines were parallelised using OpenMP and OpenCL libraries; some routines were converted from MATLAB to C and optimised. Parallelisation of the code with the OpenMP was easy and resulted in an overall speedup of 15 on a 16-core computer. Parallelisation with OpenCL was more difficult owing to differences between the central processing unit and GPU architectures. The resulting speedup was substantially lower than the theoretical peak performance of the GPU; the cause was explained.

  • 8930.
    Öst, Gustav
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Search path generation with UAV applications using approximate convex decomposition2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This work focuses on the problem that pertains to area searching with UAVs. Specifically developing algorithms that generate flight paths that are short with- out sacrificing flyability. For instance, very sharp turns will compromise flyability since fixed wing aircraft cannot make very sharp turns. This thesis provides an analysis of different types of search methods, area decompositions, and combi- nations thereof. The search methods used are side to side searching and spiral searching. In side to side searching the aircraft goes back and forth only making 90-degree turns. Spiral search searches the shape in a spiral pattern starting on the outer perimeter working its way in. The idea being that it should generate flight paths that are easy to fly since all turns should be with a large turn radii. Area decomposition is done to divide complex shapes into smaller more manage- able shapes. The report concludes that with the implemented methods the side to side scanning method without area decomposition yields good and above all very reliable results. The reliability stems from the fact that all turns are 90 degrees and that algorithm never get stuck or makes bad mistakes. Only having 90 degree turns results in only four different types of turns. This allows the airplanes behav- ior along the route to be predictable after flying the first four turns. Although this assumes that the strength of the wind is a greater influence than the turbulences effect on the aircraft’s flight characteristics. This is a very valuable feature for an operator in charge of a flight. The other tested methods and area decompositions often yield a shorter flight path, however, despite extensive adjustments to the algorithms they never came to handle all cases in a satisfactory manner. These methods may also generate any kind of turn at any time, including turns of nearly 180 degrees. These turns can lead to an airplane missing the intended flight path and thus missing to scan the intended area properly. Area decomposition proves to be really effective only when the area has many protrusions that stick out in different directions, think of a starfish shape. In these cases the side to side algo- rithm generate a path that has long legs over parts that are not in the search area. When the area is decomposed the algorithm starts with, for example, one arm of the starfish at a time and then search the rest of the arms and body in turn. 

  • 8931.
    Östberg, Gustav
    Linköping University, Department of Electrical Engineering.
    A Comparative Study of Efficient Power Amplifiers in CMOS2008Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    During later years communication schemes for handheld devices have increased in complexity due to the desire to increase the throughput, i.e. the amount of information sent over a medium simultaneously. Increasing throughput can be accomplished, not only by modulating the phase or frequency, but also the amplitude. This leads to tougher requirements on the power amplifier. The conventional power amplifiers, which have the ability to follow the envelope of the carrier, are inefficient. This thesis aims to compare two old but revived architectures which exploit high-efficiency amplifiers and still have a linear relationship between the input and output. The architectures; the Polar Linearization Technique and Outphasing share the same foundation. Based on literature, the polar technique have been more successful of employing examples fufilling communication standards. The polar technique is also more versatile regarding power combiners, distortion correction and alternative implementations. The simulations performed in this thesis results show that the polar amplifier is less sensitive to process variations and has higher maximum efficiency. On the other hand, the outphasing topology have the highest linearity figures.

  • 8932.
    Österberg, Johan
    et al.
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    Ekblom, Carl-David
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    USB 2.0 Audio device2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The main task of this project were to develop, hardware and software that could stream audio data via USB 2.0. This project were based on XMOS, USB 2.0 design. In this project we have brought an idea to reality in the form of a finished product. This with verification help from engineers on Syncore technologies. Under the development process the functionality surrounding component databases, provided by Altium designer, were to be evaluated. To be mentioned is that Altium designer was the software used to develop the PCB in this project. After many hours spent developing, we finally got the hardware and software to behave in the way it was suppose to do. That is, to be able to stream audio data from a high-resolution source(PC/MAC/unit with S/PDIF out, maximum resolution 24-bit 192 kHz). This to both S/PDIF and analog stereo out via RCA-connectors. The sound quality from a possible subjective point of view is very good and we are happy with the result. We think that the functionality surrounding component databases are convenient in many applications. Not just the fact that you easily can generate an up to date pricing of all components used in a project, you can also shorten the development process. This because the developer don't have to recreate schematic symbols and footprints that has already been created. Which of course was the fundamental idea behind the database functionality. These are just a few examples of its advantages. To be considered is the fact that the administration surrounding the component databases can be very time consuming. To take full advantage of Altium designers functionalities we think that it needs a dedicated administrator that maintains the database repository.

  • 8933.
    Östlund, Eric Chung Anders
    Linköping University, Department of Electrical Engineering.
    From vision to prototype: Virtual road racing2005Independent thesis Basic level (professional degree)Student thesis
    Abstract [en]

    Riding a stationary exercise bike regularly can lead to many health benefits such as stronger muscles, higher metabolism and reduced body fat percentage to mention a few. The biggest drawback is that training on a stationary exercise bike can be immensely boring with no stimulation or amusement factor.

    This thesis presents the development of a prototype, a road racing simulator that makes training on an exercise bike more stimulating. The prototype consists of an exercise bike and a computer game. It also features a network option, making it possible to race other users, multi player style. The purpose is to make home training on the exercise bike more amusing, enjoyable and maybe even challenging.

    The focus in this report lies mainly on the graphics and network parts but all steps in producing the prototype are described so the reader can get a complete picture of the project.

  • 8934.
    Östlund, Pierre
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Design, implementation och simulering av ett MAC-protokoll för mobila trådlösa sensornätverk2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Trådlösa sensornätverk byggs upp av trådlösa sensorer, som gemensamt arbetar för att lösa en viss uppgift. Ett exempel på en sådan uppgift kan vara insamling av pollennivåer i luften över en stor yta. Sensornoderna vidarebefordrar datan sinsemellan tills den når en datainsamlingsnod någonstans i nätverket där den sedan lagras och efterbehandlas. Generellt gäller att sensornoder är små, billiga, kommunicerar trådlöst och har en väldigt lång livslängd. Traditionellt sett har sen- sornoder också antagits vara statiska (stillastående), vilket medför begränsningar om noderna bärs av exempelvis människor eller monteras på fordon.

    I detta examensarbete presenteras matmac , ett mac-protokoll som designats för att hantera mobila noder i trådlösa sensornätverk. En referensimplementa- tion av matmac har implementerats i operativsystemet Contiki och utvärderats med varierande konfigurationsparametrar, rörelsehastigheter och dataintensitet i simulatorn Cooja. Resultatet från utvärderingen visar att mekanismerna för mo- bilitetshantering i matmac främjar sensornodernas förmåga att pålitligt överföra data trots att de är mobila. 

  • 8935.
    Östman, Christian
    et al.
    Linköping University. Linköping University, Department of Electrical Engineering.
    Forsberg, Anna
    Linköping University. Linköping University, Department of Electrical Engineering.
    Support System for Landing with an Autonomous Unmanned Aerial Vehicle2009Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    There are a number of ongoing projects developing autonomous vehicles, both helicopters and airplanes. The purpose of this thesis is to study a concept for calculating the height and attitude of a helicopter. The system will be active during landing. This thesis includes building an experimental setup and to develop algorithms and software.

    The basic idea is to illuminate the ground with a certain pattern and in our case we used laser pointers to create this pattern. The ground is then filmed and the images are processed to extract the pattern. This provides us with information about the height and attitude of the helicopter. Furthermore, the concept implies that no equipment on the ground is needed. With further development the sensor should be able to calculate the movement of the underlying surface relative to the helicopter. This is very important when landing on a moving surface, e.g. a ship at sea.

    To study the concept empirically an experimental setup was constructed. The setup provides us with the necessary information to evaluate how well the system could perform in reality. The setup is built with simple and cheap materials. In the setup an ordinary web camera and laser pointers that are avaliable for everyone have been used.

  • 8936.
    Östman, Martin
    Linköping University, Department of Electrical Engineering.
    Video Coding Based on the Kantorovich Distance2004Independent thesis Basic level (professional degree)Student thesis
    Abstract [en]

    In this Master Thesis, a model of a video coding system that uses the transportation plan taken from the calculation of the Kantorovich distance is developed. The coder uses the transportation plan instead of the differential image and sends it through blocks of transformation, quantization and coding.

    The Kantorovich distance is a rather unknown distance metric that is used in optimization theory but is also applicable on images. It can be defined as the cheapest way to transport the mass of one image into another and the cost is determined by the distance function chosen to measure distance between pixels. The transportation plan is a set of finitely many five-dimensional vectors that show exactly how the mass should be moved from the transmitting pixel to the receiving pixel in order to achieve the Kantorovich distance between the images. A vector in the transportation plan is called an arc.

    The original transportation plan was transformed into a new set of four-dimensional vectors called the modified difference plan. This set replaces the transmitting pixel and the receiving pixel with the distance from the transmitting pixel of the last arc and the relative distance between the receiving pixel and the transmitting pixel. The arcs where the receiving pixels are the same as the transmitting pixels are redundant and were removed. The coder completed an eleven frame sequence of size 128x128 pixels in eight to ten hours.

  • 8937.
    Östring, Måns
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Closed Loop Identification of the Physical Parameters of an Industrial Robot2001In: Proceedings of the Third Conference on Computer Science and Systems Engineering, 2001, p. 191-198Conference paper (Other academic)
    Abstract [en]

    This paper discusses experimental identication of a flexible robot under strong feedback. Black-box models are compared with physically parameterized models. The parameters in the physical models and the blackbox models are identified from the input-output data using prediction error methods. We also investigate the importance of noise models when performing identication under strong feedback. The robot that we use is a commercial ABB robot, IRB 1400.

  • 8938.
    Östring, Måns
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Closed Loop Identification of the Physical Parameters of an Industrial Robot2001In: Proceedings of the 32nd International Symposium on Robotics, 2001Conference paper (Refereed)
    Abstract [en]

    This paper discusses experimental identication of a flexible robot under strong feedback. Black-box models are compared with physically parameterized models. The parameters in the physical models and the blackbox models are identified from the input-output data using prediction error methods. We also investigate the importance of noise models when performing identification under strong feedback. The robot that we use is a commercial ABB robot, IRB 1400.

  • 8939.
    Östring, Måns
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Closed Loop Identification of the Physical Parameters of an Industrial Robot2000Report (Other academic)
    Abstract [en]

    This paper discusses experimental identication of a flexible robot under strong feedback. Black-box models are compared with physically parameterized models. The parameters in the physical models and the blackbox models are identified from the input-output data using prediction error methods. We also investigate the importance of noise models when performing identication under strong feedback. The robot that we use is a commercial ABB robot, IRB 1400.

  • 8940.
    Östring, Måns
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Identification, Diagnosis, and Control of a Flexible Robot Arm2002Licentiate thesis, monograph (Other academic)
    Abstract [en]

    The most important factors in manufacturing are quality, cost, and productivity. The trend is towards lighter robots with increased mechanical flexibilities, and therefore there is a need to include the flexibilities in the robot models to obtain good performance of the robot. The core theme in this thesis is modeling and identification of the physical parameters of an ABB IRB 1400 industrial robot. The approximation made is that the robot arm can be described using a finite number of masses connected by springs and dampers. It has been found that a three-mass model gives a reasonably good description of the robot when moving around axis one. The physical parameters of this model are identified using off-line and on-line algorithms. The algorithms are based on prediction error methods. For the on-line identication the Matlab System Identifiation Toolbox is used. For the on-line identication the algorithm used is a modified version of a recursive prediction error method to cope with continuous time models. The models are then used in diagnosis and control. Two ways of doing diagnosis using on-line identification are investigated. Estimating some of the physical parameters of the robot arm recursively makes it possible to monitor important aspects of the system such as friction and load. LQG control of the flexible robot arm is also studied with the aim of good disturbance rejection. Aspects that have been studied are unstable regulators and the use of accelerometers.

  • 8941.
    Östring, Måns
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    On Modeling, Fault Detection and Fault Isolation of Valve and Pipe System2000Report (Other academic)
    Abstract [en]

    Valve and pipe systems are used in many areas. Often there is redundancy in the system. If one valve breaks it may be possible to lead the gas (or fluid) another way. To do this automatically we have to be able to detect and isolate faults. In this report, we show a way to use discrete event dynamical system models for analyzing where to put sensors in a valve and pipe system.

  • 8942.
    Östring, Måns
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Svante
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Recursive Identification of Physical Parameters in a Flexible Robot Arm2002Report (Other academic)
    Abstract [en]

    Recursive identification of physically parameterized models of continuous time systems is considered. As an example a model of a single link flexible robot arm is considered. The aim of the identification is to generate on-line estimates of physical parameters that can be used for, e.g., diagnosis purposes. For evaluation the algorithm is applied to data from an industrial robot, and three important parameters are identified using only measurements of the motor angle.

  • 8943.
    Östring, Måns
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Svante
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Norrlöf, Mikael
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Closed-Loop Identification of an Industrial Robot Containing Flexibilities2001Report (Other academic)
    Abstract [en]

    Closed-loop identification of an industrial robot of the type ABB IRB 1400 is considered. Data are collected when the robot is subject to feedback control and moving around axis one. Both black-box and physically parameterized models are identified. A main purpose is to model the mechanical flexibilities. It is found that a model consisting of three-masses connected by springs and dampers gives a good description of the dynamics of the robot.

  • 8944.
    Östring, Måns
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Svante
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Norrlöf, Mikael
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Closed-Loop Identification of an Industrial Robot Containing Flexibilities2003In: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 11, no 3, p. 291-300Article in journal (Refereed)
    Abstract [en]

    Closed-loop identification of an industrial robot of the type ABB IRB 1400 is considered. Data are collected when the robot is subject to feedback control and moving around axis one. Both black-box and physically parameterized models are identified. A main purpose is to model the mechanical flexibilities. It is found that a model consisting of three-masses connected by springs and dampers gives a good description of the dynamics of the robot.

  • 8945.
    Östring, Måns
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Tjärnström, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Norrlöf, Mikael
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Modeling of Industrial Robot for Identification, Monitoring and Control2002In: Proceedings of the 2002 International Symposium on Advanced Control of Industrial Processes, 2002Conference paper (Refereed)
    Abstract [en]

    In this paper we study the problem of a modeling, identifying, and monitoring an industrial robot. We start by showing how a robot can be modeled in increasing degree of accuracy using high end tools such as MathModelica. This model can be transformed semi-automatically into a minimal state-space form which in turn can be used for identification. Moreover, the physically connected equations can be identified recursively, making it possible to monitor critical parts of the robot. When attached to a well trimmed detection scheme this provides a big help for operators, who easily can track problems with the process.

  • 8946.
    Östring, Måns
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Tjärnström, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Norrlöf, Mikael
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Modeling of Industrial Robot for Identification, Monitoring and Control2002Report (Other academic)
    Abstract [en]

    In this paper we study the problem of a modeling, identifying, and monitoring an industrial robot. We start by showing how a robot can be modeled in increasing degree of accuracy using high end tools such as MathModelica. This model can be transformed semi-automatically into a minimal state-space form which in turn can be used for identification. Moreover, the physically connected equations can be identified recursively, making it possible to monitor critical parts of the robot. When attached to a well trimmed detection scheme this provides a big help for operators, who easily can track problems with the process.

  • 8947.
    Özdogan, Özgecan
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Björnson, Emil
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Larsson, Erik G.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Massive MIMO With Spatially Correlated Rician Fading Channels2019In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 67, no 5, p. 3234-3250Article in journal (Refereed)
    Abstract [en]

    This paper considers multi-cell massive multiple-input multiple-output systems, where the channels are spatially correlated Rician fading. The channel model is composed of a deterministic line-of-sight path and a stochastic non-line-of-sight component describing a practical spatially correlated multipath environment. We derive the statistical properties of the minimum mean squared error (MMSE), element-wise MMSE, and least-square channel estimates for this model. Using these estimates for maximum ratio combining and precoding, rigorous closed-form uplink (UL) and downlink (DL) achievable spectral efficiency (SE) expressions are derived and analyzed. The asymptotic SE behavior, when using the different channel estimators, are also analyzed. The numerical results show that the SE is higher when using the MMSE estimator than that of the other estimators, and the performance gap increases with the number of antennas.

  • 8948.
    Özdogan, Özgecan
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Björnson, Emil
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Larsson, Erik G
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Uplink Spectral Efficiency of Massive MIMO with Spatially Correlated Rician Fading2018In: 2018 IEEE 19TH INTERNATIONAL WORKSHOP ON SIGNAL PROCESSING ADVANCES IN WIRELESS COMMUNICATIONS (SPAWC), IEEE , 2018, p. 216-220Conference paper (Refereed)
    Abstract [en]

    This paper considers the uplink (UL) of a multicell Massive MIMO (multiple-input multiple-output) system with spatially correlated Rician fading channels. The channel model is composed of a deterministic line-of-sight (LoS) path and a stochastic non-line-of-sight (NLoS) component describing a spatially correlated multipath environment. We derive the statistical properties of the minimum mean squared error (MMSE) and least-square (LS) channel estimates for this model. Using these estimates for maximum ratio (MR) combining, rigorous closed-form UL spectral efficiency (SE) expressions are derived. Numerical results show that the SE is higher when using the MMSE estimator than the LS estimator, and the performance gap increases with the number of antennas. Moreover, Rician fading provides higher achievable SEs than Rayleigh fading since the LoS path improves the sum SE.

  • 8949.
    Özdogan, Özgecan
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Björnson, Emil
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Zhang, Jiayi
    Beijing Jiaotong Univ, Peoples R China.
    Cell-Free Massive MIMO with Rician Fading: Estimation Schemes and Spectral Efficiency2018In: 2018 CONFERENCE RECORD OF 52ND ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS, AND COMPUTERS, IEEE , 2018, p. 975-979Conference paper (Refereed)
    Abstract [en]

    As the cell sizes in cellular networks shrink, the inter-cell interference becomes more of an issue. Instead of operating each cell autonomously, we can connect all the access points (APs) together to form a cell-free massive MIMO (multiple-input multiple-output) system that can alleviate interference by spatial processing. Previous studies have focused on Rayleigh fading channels, but in densely deployed systems, it is likely that some of the users will have line-of-sight (LoS) propagation to some of the APs. In this paper, we model this by arbitrarily distributed Rician fading channels. Two types of channel estimators are considered: a classical least-square (LS) estimator and a Bayesian minimum mean square error (MMSE) estimator. We derive closed-form spectral efficiency (SE) expressions for the uplink (UL) and downlink (DL) when using each of these estimators for maximum ratio (MR) processing. The performance difference is evaluated numerically to figure out under which conditions it is beneficial to know the channel statistics when estimating a channel.

  • 8950.
    Özkan, Emre
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, Faculty of Science & Engineering.
    Fritsche, Carsten
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, Faculty of Science & Engineering.
    Gustafsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, Faculty of Science & Engineering.
    Online EM algorithm for joint state and mixture measurement noise estimation2012In: 15th International Conference on Information Fusion (FUSION), 2012, IEEE , 2012, p. 1935-1940Conference paper (Refereed)
    Abstract [en]

    In this study, we aim to estimate the unknown multi-modal measurement noise distribution of nonlinear state space models. The unknown noise distribution is modeled as a mixture of exponential family of distributions. We use the Expectation-Maximization (EM) method in order to jointly estimate the unknown parameters as well as the states. The online version of the EM algorithm is implemented by using particle filtering techniques. The resulting algorithm is a noise adaptive particle filter which is applicable to many sensor models having multi-modal noise distributions with unknown parameters.

176177178179180 8901 - 8950 of 8965
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