liu.seSearch for publications in DiVA
Change search
Refine search result
3456789 251 - 300 of 8965
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 251.
    Anderson, Kristin
    Linköping University, The Institute of Technology. Linköping University, Department of Electrical Engineering, Information Theory.
    Cost-Distortion Measures for Broadcast Encryption2005In: NordSec 2005. Student session,2005, 2005Conference paper (Other academic)
    Abstract [en]

    In a typical broadcast encryption scenario, a sender wishes to securely transmit messages to a subset of receivers, the intended set, using a broadcast channel. Several schemes for broadcast encryption exist and they allow the sender to reach a privileged set of receivers and by the use of encryption block all others from receiving the message. Most of the existing broadcast encryption literature assumes that the intended set and the privileged set are equal but this is not always necessary. In some applications a slight difference between the intended and the privileged set may be tolerated if the cost of transmitting the message decreases sufficiently. It has been suggested that a few free-riders, users not in the intended set but in the privileged set, may be allowed in some scenarios. In rare cases the opposite could also be possible, that is some users are in the intended set but not in the privileged set. Our approach is to use the information theoretic concept of distortion to measure the discrepancy between the intended and the privileged sets. As a cost measure we use the average number of transmissions required to send one message. As an example of the use for these measures we have developed three simple algorithms that aim to lower the cost by adding some distortion; one greedy algorithm and two versions of an algorithm based on randomness. By simulations we have compared them using our cost and distortion measures. The subset difference (SD) scheme has been used as the underlying broadcast encryption scheme. The greedy algorithm is not tightly bound to the SD scheme while the two randomness-based algorithms take some use of the properties of the SD scheme.

  • 252.
    Anderson, Kristin
    Linköping University, The Institute of Technology. Linköping University, Department of Electrical Engineering, Information Theory.
    Performance of the Subset Difference Scheme for Broadcast Encryption2004Report (Other academic)
    Abstract [en]

    This report considers the subset difference scheme for broadcast encryption and the number of broadcast transmissions required when using this scheme. For cases where the privileged users are gathered in a few groups we derive the worst case number of transmissions. We also present an upper bound for the number of transmissions based on the number of transitions between privileged and nonprivileged users in the user set.

  • 253.
    Anderson, Kristin
    Linköping University, Department of Electrical Engineering, Information Theory. Linköping University, The Institute of Technology.
    Tree Structures in Broadcast Encryption2005Licentiate thesis, monograph (Other academic)
    Abstract [en]

    The need for broadcast encryption arises when a sender wishes to securely distribute messages to varying subsets of receivers, using a broadcast channel, for instance in a pay-TV scenario. This is done by selecting subsets of users and giving all users in the same subset a common decryption key. The subsets will in general be overlapping so that each user belongs to many subsets and has several different decryption keys. When the sender wants to send a message to some users, the message is encrypted using keys that those users have. In this thesis we describe some broadcast encryption schemes that have been proposed in the literature. We focus on stateless schemes which do not require receivers to update their decryption keys after the initial keys have been received; particularly we concentrate on the Subset Difference (SD) scheme.

    We consider the effects that the logical placement of the receivers in the tree structure used by the SD scheme has on the number of required transmissions for each message. Bounds for the number of required transmissions are derived based on the adjacency of receivers in the tree structure. The tree structure itself is also studied, also resulting in bounds on the number of required transmissions based on the placement of the users in the tree structure.

    By allowing a slight discrepancy between the set of receivers that the sender intends to send to and the set of receivers that actually can decrypt the message, we can reduce the cost in number of transmissions per message. We use the concept of distortion to quantify the discrepancy and develop three simple algorithms to illustrate how the cost and distortion are related.

  • 254.
    Anderson, Kristin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Electrical Engineering, Information Theory.
    Claesson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Electrical Engineering, Information Theory.
    Ingemarsson, Ingemar
    Linköping University, Department of Electrical Engineering.
    Broadcast Encryption and Group Codes2004Report (Other academic)
    Abstract [en]

    We consider the subset difference scheme for broadcast encryption and count the number of required transmissions when using this scheme. The subset scheme organizes receivers in a tree structure and we note that isomorphic trees yield the same number of required transmissions. We then study the group properties of isomorphism classes of trees. Finally we formulate some research questions for further study of the performance of the subset difference scheme.

  • 255.
    Anderson, Kristin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Electrical Engineering, Information Theory.
    Claesson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Electrical Engineering, Information Theory.
    Löfvenberg, Jacob
    Linköping University, The Institute of Technology. Linköping University, Department of Electrical Engineering, Information Theory.
    Effects of User Adjacency in the Subset Difference Scheme for Broadcast Encryption2005In: Radiovetenskap och Kommunikation, RVK05,2005, 2005Conference paper (Refereed)
    Abstract [en]

    We consider the broadcast encryption problem where one sender wishes to transmit messages securely to a selected set of receivers using a broadcast channel, as is the case in digital television for example. Specifically, we study the subset difference scheme for broadcast encryption and the number of broadcast transmissions required when using this scheme. The effects of adjacency in the user set are considered and we introduce the notion of transitions in the user set as a means to quantify the adjacency. We present upper and lower bounds for the number of transmissions based on the number of transitions between privileged and nonprivileged users in the user set. For cases where the privileged users are gathered in a few groups we derive the maximum number of transmissions.

  • 256.
    Anderson, Kristin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Electrical Engineering, Information Theory.
    Claesson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Electrical Engineering, Information Theory.
    Löfvenberg, Jacob
    Linköping University, The Institute of Technology. Linköping University, Department of Electrical Engineering, Information Theory.
    Ingemarsson, Ingemar
    The Algebraic Structure of a Broadcast Encryption Scheme2005In: Radiovetenskap och Kommunikation, RVK05,2005, 2005Conference paper (Refereed)
    Abstract [en]

    In this paper we consider the subset difference scheme for broadcast encryption and count the number of required broadcast transmissions when using this scheme. The subset difference scheme organizes receivers in a tree structure and we note that isomorphic trees yield the same number of required broadcast transmissions. Based on the isomorphism the trees can be partitioned into classes. We suggest to use the vast amount of tools available from the theory of groups to analyze the subset difference scheme and therefore we formulate the mappings between isomorphic trees using concepts from group theory. Finally we identify some research issues for further study of the performance of the subset difference scheme using group theory.

  • 257.
    Anderson, Sören
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    On Optimal Dimension Reduction for Sensor Array Signal Processing1993In: Signal Processing, ISSN 0165-1684, E-ISSN 1872-7557, Vol. 30, no 2, p. 245-256Article in journal (Refereed)
    Abstract [en]

    The computational complexity for direction-of-arrival estimation using sensor arrays increases very rapidly with the number of sensors in the array. One way to lower the amount of computations is to employ some kind of reduction of the data dimension. This is usually accomplished by employing linear transformations for mapping full dimension data into a lower dimensional space. Different approaches for selecting these transformations have been proposed. In this paper, a transformation matrix is derived that makes it possible to theoretically attain the full-dimension Cramér-Rao bound also in the reduced space. A bound on the dimension of the reduced data set is given, above which it is always possible to obtain the same accuracy for the estimates of the source localizations, using the lower-dimension data, as that achievable by using the full dimension data. Furthermore, a method is devised for designing the transformation matrix. Numerical examples, using this design method, are presented, where the achievable performance of the (optimal) Weighted Subspace Fitting method with full dimension data is compared to the performance obtained with reduced dimension data. The problem of estimating parameters of sinusoidal signals from noisy data is also addressed by a direct application of the results derived herein.

  • 258.
    Andersson, Adam
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, The Institute of Technology.
    Range Gated Viewing with Underwater Camera2005Independent thesis Basic level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The purpose of this master thesis, performed at FOI, was to evaluate a range gated underwater camera, for the application identification of bottom objects. The master thesis was supported by FMV within the framework of “arbetsorder Systemstöd minjakt (Jan Andersson, KC Vapen)”. The central part has been field trials, which have been performed in both turbid and clear water. Conclusions about the performance of the camera system have been done, based on resolution and contrast measurements during the field trials. Laboratory testing has also been done to measure system specific parameters, such as the effective gate profile and camera gate distances.

    The field trials shows that images can be acquired at significantly longer distances with the tested gated camera, compared to a conventional video camera. The distance where the target can be detected is increased by a factor of 2. For images suitable for mine identification, the increase is about 1.3. However, studies of the performance of other range gated systems shows that the increase in range for mine identification can be about 1.6. Gated viewing has also been compared to other technical solutions for underwater imaging.

  • 259.
    Andersson, Amanda
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control.
    Näsholm, Elin
    Linköping University, Department of Electrical Engineering, Automatic Control.
    Fast Real-Time MPC for Fighter Aircraft2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The main topic of this thesis is model predictive control (MPC) of an unstable fighter aircraft. When flying it is important to be able to reach, but not exceed the aircraft limitations and to consider the physical boundaries on the control signals. MPC is a method for controlling a system while considering constraints on states and control signals by formulating it as an optimization problem. The drawback with MPC is the computational time needed and because of that, it is primarily developed for systems with a slowly varying dynamics.

    Two different methods are chosen to speed up the process by making simplifications, approximations and exploiting the structure of the problem. The first method is an explicit method, performing most of the calculations offline. By solving the optimization problem for a number of data sets and thereafter training a neural network, it can be treated as a simpler function solved online. The second method is called fast MPC, in this case the entire optimization is done online. It uses Cholesky decomposition, backward-forward substitution and warm start to decrease the complexity and calculation time of the program.

    Both methods perform reference tracking by solving an underdetermined system by minimizing the weighted norm of the control signals. Integral control is also implemented by using a Kalman filter to observe constant disturbances. An implementation was made in MATLAB for a discrete time linear model and in ARES, a simulation tool used at Saab Aeronautics, with a more accurate nonlinear model.

    The result is a neural network function computed in tenth of a millisecond, a time independent of the size of the prediction horizon. The size of the fast MPC problem is however directly affected by the horizon and the computational time will never be as small, but it can be reduced to a couple of milliseconds at the cost of optimality.

  • 260.
    Andersson, Anders
    Linköping University, Department of Electrical Engineering.
    Implementation, validation and evaluation of an ESC system during a side impact using an advanced driving simulator2009Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The objective of this thesis is to implement a basic, yet realistic, ESC system into the VTI simulator environment. This system is then validated to assure that it is working properly and provides a realistic behavior.

    The implemented ESC system is used in a study, where the ESC system could be turned on and off, to evaluate the benefits of an ESC system after a side impact. This study shows that an ESC system may aid the driver in such a critical situation when the driver is unaware that a side impact will occur. With the ESC system active no driver lost control while with the system inactive there were five drivers that lost control, but deviations in initial speed give statistical difficulties, thus more tests are needed. In the case where the driver knows that an impact will occur the ESC system showed to stabilize the automobile faster and it is shown that an expected improvement in stabilization time is between 40 to 62 percent. It was also seen during this part of the scenario that 2 percent loss of control occurred with an active ESC system and 45 percent without.

  • 261.
    Andersson, Anders
    et al.
    Linköping University, Department of Electrical Engineering.
    Hallgren, Daniel
    Linköping University, Department of Electrical Engineering.
    Passive Aircraft Altimetry using GPS as a Bistatic Radar: A simulation model2003Independent thesis Basic level (professional degree)Student thesis
    Abstract [en]

    A common way to measure height in aerial vehicles is to use a radar height altimeter (RHM). Since the RHM transmits radar pulses that can be detected, a passive alternative would be desirable in military applications. The idea to use reflected signals from the Global Positioning System (GPS) as a bistatic radar, has been established over the last years. The GPS signals are already present and would not reveal aeroplanes in covert operations.

    In this thesis, the use of reflected GPS signals as a bistatic, passive altimeter is examined. A simulation model has been developed and implemented, and simulations using the model have been done. Different types of ground cover have been investigated, both water and land types, with varying reflectivity and scattering behaviour. For larger terrain variations, e.g. mountains and valleys, a ground elevation database has been used. Furthermore, several parameters, like the antenna coverage and the satellite elevation angle, have been varied and the result of this examined.

    The results of these simulations show that measuring height is possible for bothsea and land surfaces. The accuracy depends on several error factors, like a bias originating from surface roughness and measurement errors due to noise in the receiver. The simulations also show that the most important design parameter is the antenna, which must be designed to give a sufficiently large SNR, capture the specular reflection and avoid unwanted reflections.

  • 262.
    Andersson, Anders
    et al.
    Statens väg- och transportforskningsinstitut, Fordonsteknik och simulering, FTS, Linköping, Sweden.
    Kharrazi, Sogol
    Statens väg- och transportforskningsinstitut, Fordonsteknik och simulering, FTS, Linköping, Sweden.
    Lind, Simon
    Statens väg- och transportforskningsinstitut, Fordonsteknik och simulering, FTS, Linköping, Sweden.
    Myklebust, Andreas
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, The Institute of Technology.
    Parameterization procedure of a powertrain model for a driving simulator2016In: Advances in Transportation Studies, ISSN 1824-5463, Vol. 1, p. 99-112Article in journal (Refereed)
    Abstract [en]

    The automotive industry is facing a major challenge to reduce environmental impacts. As a consequence, the increasing diversity of powertrain configurations put a demand on testing and evaluation procedures. One of the key tools for this purpose is simulators. In this paper a powertrain model and a procedure for parameterizing it, using chassis dynamometers and a developed pedal robot are presented. The parameterizing procedure uses the on-board diagnostics of the car and does not require any additional invasive sensors.

    Thus, the developed powertrain model and parameterization procedure provide a rapid non- invasive way of modelling powertrains of test cars. The parameterizing procedure has been used to model a front wheel drive Golf V with a 1.4L multi-fuel engine and a manual gearbox. The achieved results show a good match between simulation results and test data. The powertrain model has also been tested in real-time in a driving simulator.

  • 263.
    Andersson, Anders
    et al.
    Vehicle Technology and Simulation, VTI, Linköping, Sweden.
    Nyberg, Peter
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, The Institute of Technology.
    Sehammar, Håkan
    Vehicle Technology and Simulation, VTI, Linköping, Sweden.
    Öberg, Per
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, The Institute of Technology.
    Vehicle Powertrain Test Bench Co-Simulation with a Moving Base Simulator Using a Pedal Robot2013In: SAE International Journal of Passenger Cars - Electronic and Electrical Systems, ISSN 1946-4614, E-ISSN 1946-4622, Vol. 6, no 1, p. 169-179Article in journal (Refereed)
    Abstract [en]

    To evaluate driver perception of a vehicle powertrain a moving base simulator is a well-established technique. We are connecting the moving base simulator Sim III, at the Swedish National Road and Transport Research Institute with a newly built chassis dynamometer at Vehicular Systems, Linköping University. The purpose of the effort is to enhance fidelity of moving base simulators by letting drivers experience an actual powertrain. At the same time technicians are given a new tool for evaluating powertrain solutions in a controlled environment. As a first step the vehicle model from the chassis dynamometer system has been implemented in Sim III. Interfacing software was developed and an optical fiber covering the physical distance of 500 m between the facilities is used to connect the systems. Further, a pedal robot has been developed that uses two linear actuators pressing the accelerator and brake pedals. The pedal robot uses feedback loops on accelerator position or brake cylinder pressure and is controlled via an UDP interface. Results from running the complete setup showed expected functionality and we are successful in performing a driving mission based on real road topography data. Vehicle acceleration and general driving feel was perceived as realistic by the test subjects while braking still needs improvements. The pedal robot construction enables use of a large set of cars available on the market and except for mounting the brake pressure sensor the time to switch vehicle is approximately 30 minutes.

  • 264.
    Andersson, Anton
    Linköping University, Department of Electrical Engineering.
    On Generating Complex Numbers for FFT and NCO Using the CORDIC Algorithm2008Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This report has been compiled to document the thesis work carried out by Anton Andersson for Coresonic AB. The task was to develop an accelerator that could generate complex numbers suitable for fast fourier transforms (FFT) and tuning the phase of complex signals (NCO). Of many ways to achieve this, the CORDIC algorithm was chosen. It is very well suited since the basic implementation allows rotation of 2D-vectors using only shift and add operations. Error bounds and proof of convergence are derived carefully The accelerator was implemented in VHDL in such a way that all critical parameters were easy to change. Performance measures were extracted by simulating realistic test cases and then compare the output with reference data precomputed with high precision. Hardware costs were estimated by synthesizing a set of different configurations. Utilizing graphs of performance versus cost makes it possible to choose an optimal configuration. Maximum errors were extracted from simulations and seemed rather large for some configurations. The maximum error distribution was then plotted in histograms revealing that the typical error is often much smaller than the largest one. Even after trouble-shooting, the errors still seem to be somewhat larger than what other implementations of CORDIC achieve. However, precision was concluded to be sufficient for targeted applications.

  • 265.
    Andersson, Christian
    Linköping University, Department of Electrical Engineering.
    Simulering av filtrerade skärmfärger2005Independent thesis Basic level (professional degree), 20 points / 30 hpStudent thesis
    Abstract [en]

    This report present a working model for simulation of what happens to colors displayed on screens when they are observed through optical filters. The results of the model can be used to visually, on one screen, simulate another screen with an applied optical filter. The model can also produce CIE color difference values for the simulated screen colors. The model is data driven and requires spectral measurements for at least the screen to be simulated and the physical filters that will be used. The model is divided into three separate modules or steps where each of the modules can be easily replaced by alternative implementations or solutions. Results from tests performed show that the model can be used for prototyping of optical filters even though the tests of the specific algorithms chosen show there is room for improvements in quality. There is nothing that indicates that future work with this model would not produce better quality in its results.

  • 266.
    Andersson, Conny
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Design of the Modelica Library VehProLib with Non-ideal Gas Models in Engines2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis covers the reconstruction and the redesign of the modeling library VehProLib,which is constructed in the modeling language Modelica with help of the modeling toolWolfram SystemModeler. The design choices are discussed and implemented. This thesisalso includes the implementation of a turbocharger package and an initial study of the justificationof the ideal gas law in vehicle modeling. The study is made with help of Van derWaals equation of states as a reference of non-ideal gas model. It will be shown that for themean-value-engine-model, the usage of ideal gas law is justified.

  • 267.
    Andersson, Daniel
    et al.
    Linköping University, Department of Electrical Engineering.
    Sköld, Patrik
    Linköping University, Department of Electrical Engineering.
    Evaluation of a diagnostic tool for use during system development and operations2007Independent thesis Basic level (professional degree), 20 points / 30 hpStudent thesis
    Abstract [en]

    Rodon is a diagnostic tool developed by Sörman. SAAB’s interest in Rodon regards the possibility to use the tool for development and operations of aircraft systems. The main goal of this thesis was to evaluate the capacity of Rodon and determine how SAAB can use the diagnostic tool during development and operations.

    The tool uses model based diagnosis with artificial intelligence for fault isolation which is a powerful approach. If Rodon is introduced at SAAB, then detailed models of systems will be necessary to create, including the nominal behavior of the system and different faulty behaviors. In order to achieve high quality fault isolation, it is necessary to have complete and consistent models. To be able to use all applications that Rodon feature for a modeled system, preferable characteristics are that the model should be static, have discrete control signals, and have well defined system behavioral modes.

    During development of a system Rodon can be used to improve and easy the work for failure analysis, guidance of sensor placements, evaluation of tests, generation of decision structures, and fault isolation. Since design of tests during development is a desirable application that Rodon does not have, two different methods are presented that utilizes Rodon to generate all possible limit checking tests.

    In conclusion, Rodon can be very useful in several different aspects if introduced, but benefits gained by using Rodon will have to be compared to the labor cost of creating good models.

  • 268.
    Andersson, David
    Linköping University, Department of Electrical Engineering.
    Diversifying Demining: An Experimental Crowdsourcing Method for Optical Mine Detection2008Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis explores the concepts of crowdsourcing and the ability of diversity, applied to optical mine detection. The idea is to use the human eye and wide and diverse workforce available on the Internet to detect mines, in addition to computer algorithms.

    The theory of diversity in problem solving is discussed, especially the Diversity Trumps Ability Theorem and the Diversity Prediction Theorem, and how they should be carried out for possible applications such as contrast interpretation and area reduction respectively.

    A simple contrast interpretation experiment is carried out comparing the results of a laymen crowd and one of experts, having the crowds examine extracts from hyperspectral images, classifying the amount of objects or mines and the type of terrain. Due to poor participation rate of the expert group, and an erroneous experiment introduction, the experiment does not yield any statistically significant results. Therefore, no conclusion is made.

    Experiment improvements are proposed as well as possible future applications.

  • 269.
    Andersson, David
    et al.
    Linköping University, Department of Electrical Engineering.
    Fjellström, Johan
    Linköping University, Department of Electrical Engineering.
    Vehicle Positioning with Map Matching Using Integration of a Dead Reckoning System and GPS2004Independent thesis Basic level (professional degree)Student thesis
    Abstract [en]

    To make driving easier and safer, modern vehicles are equipped with driver support systems. Some of these systems, for example navigation or curvature warning systems, need the global position of the vehicle. To determine this position, the Global Positioning System (GPS) or a Dead Reckoning (DR) system can be used. However, these systems have often certain drawbacks. For example, DR systems suffer from error growth with time and GPS signal masking can occur. By integrating the DR position and the GPS position, the complementary characteristics of these two systems can be used advantageously.

    In this thesis, low cost in-vehicle sensors (gyroscope and speedometer) are used to perform DR and the GPS receiver used has a low update frequency. The two systems are integrated with an extended Kalman filter in order to estimate a position. The evaluation of the implemented positioning algorithmshows that the system is able to give an estimated position in the horizontal plane with a relatively high update frequency and with the accuracy of the GPS receiver used. Furthermore, it is shown that the system can handle GPS signal masking for a period of time.

    In order to increase the performance of a positioning system, map matching can be added. The idea with map matching is to compare the estimated trajectory of a vehicle with roads stored in a map data base, and the best match is chosen as the position of the vehicle. In this thesis, a simple off-line map matching algorithm is implemented and added to the positioning system. The evaluation shows that the algorithm is able to distinguish roads with different direction of travel from each other and handle off-road driving.

  • 270.
    Andersson, Elin
    Linköping University, Department of Electrical Engineering, Computer Vision.
    Thermal Impact of a Calibrated Stereo Camera Rig2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Measurements performed from stereo reconstruction can be obtained with a high accuracy with correct calibrated cameras. A stereo camera rig mounted in an outdoor environment is exposed to temperature changes, which has an impact of the calibration of the cameras.

    The aim of the master thesis was to investigate the thermal impact of a calibrated stereo camera rig. This was performed by placing a stereo rig in a temperature chamber and collect data of a calibration board at different temperatures. Data was collected with two different cameras and lensesand used for calibration of the stereo camera rig for different scenarios. The obtained parameters were plotted and analyzed.

    The result from the master thesis gives that the thermal variation has an impact of the accuracy of the calibrated stereo camera rig. A calibration obtained in one temperature can not be used for a different temperature without a degradation of the accuracy. The plotted parameters from the calibration had a high noise level due to problems with the calibration methods, and no visible trend from temperature changes could be seen.

  • 271.
    Andersson, Emma
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Intuitive Mission Handling with Automatic Route Re-planning using Model Predictive Control2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The system for mission handling in the Gripen fighter aircraft, and in its ground supporting system, consists for example of ways to plan mission routes, create mission points and validate performed missions. The system is complex and for example, the number of different mission points used increases due to changing demands and needs. This master thesis presents suggestions for improvements and simplifications for the mission handling system, to make it more intuitive and more friendly to use. As a base for the suggestions, interviews with pilots from Saab, TUJAS and FMV have been conducted, this is to obtain opinions and ideas from those using the system and have deep knowledge about it.

    Another possible assistance and improvement is to provide the possibility of on-line automatic re-planning of the mission route in case of obstacles. MPC (Model Predictive Control) has been used to estimate the obstacle’s flight path,and calculate a new route to the next mission point which does not conflict with the estimated enemy’s path. This system has been implemented in Matlab and the concept is demonstrated with different test scenarios where the design parameters (prediction horizon and penalty in the cost function) for the controller are varied, and stationary and moving obstacles are induced.

  • 272.
    Andersson, Erik
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Modelling of Cranking Behaviour in Heavy Duty Truck Engines2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In modern heavy duty trucks the battery is a central component. Its traditional role as an energy source for engine cranking has been extended to include powering a number of elec- trical components on the truck, both during driving and during standstill. As a consequence of this it is important to know how much a battery in use has aged and lost in terms of ca- pacity and power output. The difficulty in measuring these factors on a battery in use causes problem, since heavy duty truck batteries are often replaced too early or too late, leading to unnecessary high replacement costs or truck standstill respectively.

    The overall goal of the effort, of which this thesis is a part, is to use a model of the cranking behaviour of a heavy duty truck engine, which depends on the battery condition, to estimate the ageing and wear of a heavy duty truck battery. This thesis proposes a modelling approach to model the components involved in engine cranking.

    In the thesis work, system identification is made of the systems forming part of the cranking of a heavy duty truck engine. These components are the starter battery, the starter motor and its electrical circuit and the internal combustion engine. Measurement data has been provided by Scania AB for the evaluation of the models. The data has been collected from crankings of a heavy duty diesel engine at different temperatures and battery charge levels. For every cranking lapse the battery voltage and current have been measured as well as the engine rotational speed.

    A starter battery model is developed and evaluated. The resulting battery model is then incorporated into two different engine cranking models, Model 1 and Model 2, including a starter motor model and an internal combustion engine model apart form the battery model. The two cranking models differ in several aspects and their differences and resulting evalu- ations are discussed.

    The battery model is concluded to be sufficiently accurate during model verification, however the two cranking models are not. Model 2 is verified as more correct in in its output than Model 1, but neither is sufficiently accurate for their purpose. The conclusion is drawn that the modelling approach is sound but development of Model 2 is needed before the model can be used in model-based condition estimation. 

  • 273.
    Andersson, Erik
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    Omkonstruktion och arkitekturbyte av autopilot för obemannade farkoster2012Independent thesis Basic level (university diploma), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    This thesis has been written at Linköping University for the company Instrument Control Sweden AB (ICS).

    ICS is a small company located in Linköping that develops software and hardware for Unmanned Aerial Vehicles, UAV. At present, ICS has a fully functional autopilot called EasyPilot but they want to reduce the autopilot’s size to make it more attractive.

    The purpose of this thesis was to investigate if it was possible to reduce the size of the autopilot and how, in that case, it would be done. It was also necessary to examine whether the old processors should be replaced by new ones and how hard it would be to convert the old software to these new processors.

    To succeed with the goals many of the old components had to be changed for new, smaller ones. Some less necessary parts were also completely removed. The results showed that the size could be reduced quite a bit, exactly how much is hard to say since no PCB-layout were done.

    By doing some programming tests on the new components it could be shown that some parts of the old code could be reused on the new design. It was mainly algorithms and other calculations. However, a lot of new code still had to be written in order to successfully convert the old software to the new hardware. 

  • 274.
    Andersson, Erik
    et al.
    Linköping University, Department of Electrical Engineering, Electronics System.
    Olsson, Christian
    Linköping University, Department of Electrical Engineering, Electronics System.
    Linearization of Power Amplifier using Digital Predistortion, Implementation on FPGA2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The purpose of this thesis is to linearize a power amplifier using digital predistortion. A power amplifier is a nonlinear system, meaning that when fed with a pure input signal the output will be distorted. The idea behind digital predistortion is to distort the signal before feeding it to the power amplifier. The combined distortions from the predistorter and the power amplifier will then ideally cancel each other. In this thesis, two different approaches are investigated and implemented on an FPGA. The first approach uses a nonlinear model that tries to cancel out the nonlinearities of the power amplifier. The second approach is model-free and instead makes use of a look-up table that maps the input to a distorted output. Both approaches are made adaptive so that the parameters are continuously updated using adaptive algorithms. First the two approaches are simulated and tested thoroughly with different parameters and with a power amplifier model extracted from the real amplifier. The results are shown satisfactory in the simulations, giving good linearization for both the model and the model-free technique. The two techniques are then implemented on an FPGA and tested on the power amplifier. Even though the results are not as well as in the simulations, the system gets more linear for both the approaches. The results vary widely due to different circumstances such as input frequency and power. Typically, the distortions can be attenuated with around 10 dB. When comparing the two techniques with each other, the model-free method shows slightly better results.

  • 275.
    Andersson, Fredrik
    Linköping University, Department of Electrical Engineering.
    Determining recording time of digital soundrecordings using the ENF criterion2009Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In forensic investigations, verification of digital recordings is an important as-pect. There are numerous methods to verify authentication of recordings, but itis difficult to determine when the media was recorded. By studying the electricalnetwork frequency, one can find a unique signature and then match the recordingto this signature. By matching a recorded signal to a database, which contains allnecessary information, one can find the time when the recording was made.

  • 276.
    Andersson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems.
    Andersson, Hampus
    Linköping University, Department of Electrical Engineering, Vehicular Systems.
    Numerical Optimal Control of Hybrid Electric Trucks: Exhaust Temperature, NOx Emission and Fuel Consumption2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The controls for a parallel hybrid electric truck are optimized using numerical optimal control. Trade-offs between catalyst light-off times, NOx emission and fuel consumption have been investigated for cold starts at two operating points, as well as temperature differences between conventional and hybrid powertrains during WHTC (World Harmonized Transient Cycle). A model describing the temperature dynamics of the aftertreatment system is implemented as well as temperature-based deNOx performance for both Cu-Zeolite and Fe-Zeolite catalysts. Control is performed in a piecewise linear fashion, resulting in a total of 23 states including control signals. It is shown that high temperatures can be a larger threat to catalyst performance when running the WHTC than low temperatures, for both conventional and hybrid powertrains. Furthermore, decreasing the light-off time of the catalyst does not always lead to decreased NOx emission, instead there is a trade-off between light-off time and NOx emission. It is found that there are controls that will realize decreased NOx emission for a hybrid truck during cold starts at the expense of increased fuel consumption.

  • 277.
    Andersson, Helena
    Linköping University, Department of Electrical Engineering.
    Genus och informationsteknologi2004Independent thesis Basic level (professional degree)Student thesis
    Abstract [en]

    This thesis discusses how the education in the Master of Engineering program can change to become more into line for the students needs, especially for the women, both directly in the education situation and later in their occupational roles. This is done using a gender perspective. Both the education and the occupation today is characterised by masculine norms and values. The education lacks gender perspective and is created by men, for men. The thesis gives concrete proposals on how to change two existing courses to better fit the students. Some of the most important changes are to make the goals of the courses more accessible and visible for the students, make sure that both men and women occurs in teaching positions and have course literature written by women as well as men.

  • 278.
    Andersson, Henrik
    Linköping University, Department of Electrical Engineering, Vehicular Systems.
    Model Based Control of Throttle, EGR and Wastegate: A System Analysis of the Gas Flows in an SI-Engine2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Due to governmental requirements on low exhaust gas emissions and the drivers request of fast response, it is important to be able to control the gas flow in a spark ignited engine accurately. The air into the cylinder is directly related to the torque generated by the engine. The technique with recirculation of exhaust gases (EGR) affect the air flow into the cylinder and increase the complexity of the control problem. In this thesis a mean value model for a spark ignited engine has been created. The basis was a diesel model from Linköping University that has been modified and parameterized with data from a test cell. The model has been used to study the gas exchange system with respect to the dynamic behaviors and nonlinearities that occur when the three actuators (throttle, wastegate and EGR-valve) are changed. Based on this analysis, some different control strategies have been developed and tested on the model. The presented results show that different control strategies give different behaviors and there is a trade-off between fast torque response and high precision for controlling the EGR-ratio. A control strategy is proposed containing two main feedback loops, prefiltering of the reference signal and a feedforward part.

  • 279.
    Andersson Holmström, Simon
    Linköping University, Department of Electrical Engineering, Computer Engineering.
    Adaptive TDC: Implementation and Evaluation of an FPGA2015Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    Time to digital converter (TDC) is a digital unit that measures the time interval between two events.This is useful to determine the characteristics and patterns of a signal or an event. In this thesis ahybrid TDC is presented consisting of a tapped delay line and a clock counter principle.

    The TDC is used to measure the time between received data in a QKD application. If the measuredtime does not exceed a certain value then data had been sent without any interception. It is alsopossible to use TDCs in other fields such as laser-ranging and time-of-flight applications.

    The TDC consists of two carry chains, an encoder, a FIFO and a counter for each channel, anAXI-module and a control unit to generate command signals to all channels that are implemented.The time is measured by sampling the signal that has propagated through the carry chain and from thissample encode the propagation length.

    In this thesis a TDC is implemented that has a 10 ns dead time and a resolution below 28 psin a four channel mode. The propagation variation is approximately two percent of the total valueduring testing. For the implementation an FPGA-board with a Zynq XC7Z020 SoC is used withSystemVerilog that is a hardware describing language (HDL).

  • 280.
    Andersson Hultgren, Jonas
    Linköping University, Department of Electrical Engineering, Information Coding.
    Metoder för förbättrad rumsuppfattning i körsimulatorer2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Today, driving simulators are a very important resource for conducting studies whichconcern driver behavior and perception. Full control of the scenario andenvironment, costs and safety are all factors which makes simulator studiespreferable over real world studies.

    One issue for driving simulators is that the image is projected onto a twodimensionalscreen, which limits the driver's ability to correctly estimate distanceand speed. It is commonly known that distance and velocity are underestimated indriving simulators.

    The goal of this thesis was to find methods that could lead to better distanceestimation in driving simulators and in this project motion parallax and shadowswere implemented and tested, focusing mainly on the former.At the end of the project, a simulator study was conducted to evaluate the effect ofmotion parallax. Ten participants made two runs each in VTI's Simulator III facility,one with motion parallax enabled and one with it disabled. The scenario that tookplace during the two runs consisted of several overtaking situations and a speedperception test.

    The results from the simulator study showed that the participants tended to positionthemselves farther from the road center line when motion parallax was active insituations when the field of view was obscured by preceding vehicles.

  • 281.
    Andersson, Ingemar
    Linköping University, Department of Electrical Engineering. Linköping University, The Institute of Technology.
    Cylinder pressure and ionization current modeling for spark ignited engines2002Licentiate thesis, monograph (Other academic)
  • 282.
    Andersson, Ingemar
    et al.
    Chalmers.
    Eriksson, Lars
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, The Institute of Technology. Linköping University, Department of Electrical Engineering.
    A Parametric Model for Ionization Current in a Four Stroke SI Engine2009In: JOURNAL OF DYNAMIC SYSTEMS MEASUREMENT AND CONTROL-TRANSACTIONS OF THE ASME, ISSN 0022-0434, Vol. 131, no 2, p. 021001-Article in journal (Refereed)
    Abstract [en]

    A model for the thermal part of an ionization signal is presented that connects the ionization current to cylinder pressure and temperature in a spark ignited internal combustion engine. One strength of the model is that, after calibration, it has only two free parameters: burn angle and initial kernel temperature. By fitting the model to a measured ionization signal, it is possible to estimate both cylinder pressure and temperature, where the pressure is estimated with good accuracy. The model approach is validated on engine data. Cylinder pressure and ionization current data were collected on a Saab four-cylinder spark ignited engine for a variation in ignition timing and air-fuel ratio. The main result is that the parametrized ionization current model can be used to estimating combustion properties as pressure, temperature, and content of nitric oxides based on measured ionization currents. The current status of the model is suitable for off-line analysis of ionization currents and cylinder pressure. This ionization current model not only describes the connection between the ionization current and the combustion process, but also offers new possibilities for engine management system to control the internal combustion engine.

  • 283.
    Andersson, Ingemar
    et al.
    Chalmers.
    Eriksson, Lars
    Linköping University, Department of Electrical Engineering, Vehicular Systems.
    Ion Current Interpretation for Sensing and Control of Combustion Stability1999In: Second conference on Computer Science and Systems Engineering in Linköping, 1999, p. 119-124Conference paper (Refereed)
  • 284.
    Andersson, Ingemar
    et al.
    Chalmers.
    Eriksson, Lars
    Linköping University, Department of Electrical Engineering, Vehicular Systems.
    Ion Sensing for Combustion Stability Control of a Spark Ignited Direct Injected Engine2000In: Electronic Engine Controls: Controls, 2000, Vol. SP-1500Conference paper (Refereed)
    Abstract [en]

    The combustion stability of a direct injected spark ignited engine depends on the injection timing and it is desirable to have a controller that minimizes the combustion variability. A novel approach for determining combustion stability in stratified mode is presented that rely on the ionization current and enables closed loop control of the injection timing. The coefficient of variation for IMEP is used as a measure of combustion stability and a connection between maximum torque and low combustion variability is pointed out. The coefficient of variation of the ion current integral is well correlated with the coefficient of variation for IMEP. Furthermore, it is shown how the integral of the ion current together with COV(ion integral) can be used to determine the combustion stability and to distinguish high combustion stability from misfire.

  • 285.
    Andersson, Ingemar
    et al.
    Fordonssystem Department of Electrical Engineering, Linköpings universitet.
    Frisk, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Electrical Engineering, Vehicular Systems.
    Diagnosis of Evaporative Leaks and Sensor Faults in a Vehicle Fuel System2001In: IFAC Workshop: Advances in Automotive Control,2001, 2001, p. 629-634Conference paper (Refereed)
    Abstract [en]

    This paper describes a vacuum-decay based evaporative leak detection procedure for vehicle fuel systems. A physical model for an evaporative system is proposed containing parts for fuel evaporation, leakage flow and canister flow. Two methods for detecting evaporative leakages based on the model is presented. Both methods can detect a 0.5 mm diameter leakage in a laboratory environment. Keywords: purge system, fault diagnosis, fault detection, model based diagnosis 1. INTRODUCTION According to regulations for emissions from vehicles, fuel vapor leakage from the fuel tank must be detected. Fuel vapor is always generated in the fuel tank, the amount depends on ambient conditions like temperature and movement of the tank. Filling fuel also causes extra vapor to be generated. The fuel vapor may cause an over pressure that may push vapor out of the tank. Also, as fuel is consumed an under-pressure develops in the tank and it is required to level the fuel-tank gas pressure with ambi.

  • 286.
    Andersson, Isak
    et al.
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    Karlsson, Melki
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    Body Coupled Communication: Ändring av prototypkort2014Independent thesis Basic level (university diploma), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    Communication using the human body as a transmission medium, the capacitive coupling between the skin and sensor, has been an active research area for PAN (Personal Area Network) since Thomas Guthrie Zimmerman introduced the technique in 1995. The reason for this is to examine the benefits and uses of a communication method that does not emit RF signals and thus reduce the risk of unauthorized interception.

    This report describes a thesis that examines the possibility of elimination of USB to UART converter on Microchip BodyCom through software USB-stack and combine this with Body Coupled Communication functionality in a single microcontroller. Furthermore, studies on if the application code in Body Coupled Communication transmitters can be modified to extend functionality.

    It was given in the conditions that microcontrollers from Microchip should be used, furthermore, low price and low power consumption were important, especially for the transmitter. The method for achieving this has been the use of Microchip BodyCom development kit with USB Microchip low pin count development kit and Microchip USB firmware framework.

    The result was that the USB- to UART-converter could be integrated with Microchip BodyCom, using software USB-stack and a modified program code for BodyCom in a single microcontroller.

    Only your imagination sets the limits for Body Coupled Communication can be used for. For example, it would be possible to exchange electronic business cards by a handshake or open a locked door only by using the handle.

  • 287.
    Andersson, Johan
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    A framework for evaluation of iterative learning control2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In many industrial applications robots are used for heavy and repetitive tasks. For these applications iterative learning control (ILC) is a way to capture the repetitive nature and use it to improve some kind of reference tracking.

    In this master thesis a framework has been developed to help a user getting started with ILC. Some hands-on examples are given on how to easily use the framework. The transition from the far more common discrete time domain to the continuous time domain used by the framework is eased by tuning theory. The achievable performance is demonstrated with the help of the built-in plot functions of the framework.

  • 288.
    Andersson, Johan
    Linköping University, Department of Electrical Engineering, Vehicular Systems.
    Automated Fault Tree Generation from Requirement Structures2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The increasing complexity of today’s vehicles gives drivers help with everything from adaptive cruisecontrol to warning lights for low fuel level. But the increasing functionality also increases the risk offailures in the system. To prevent system failures, different safety analytic methods can be used, e.g.,fault trees and/or FMEA-tables. These methods are generally performed manually, and due to thegrowing system size the time spent on safety analysis is growing with increased risk of human errors. If the safety analysis can be automated, lots of time can be saved.

    This thesis investigates the possibility to generate fault trees from safety requirements as wellas which additional information, if any, that is needed for the generation. Safety requirements are requirements on the systems functionality that has to be fulfilled for the safety of the system to be guaranteed. This means that the safety of the truck, the driver, and the surroundings, depend on thefulfillment of those requirements. The requirements describing the system are structured in a graphusing contract theory. Contract theory defines the dependencies between requirements and connectsthem in a contract structure.

    To be able to automatically generate the fault tree for a system, information about the systems failure propagation is needed. For this a Bayesian network is used. The network is built from the contract structure and stores the propagation information in all the nodes of the network. This will result in a failure propagation network, which the fault tree generation will be generated from. The failure propagation network is used to see which combinations of faults in the system can violate thesafety goal, i.e., causing one or several hazards. The result of this will be the base of the fault tree.

    The automatic generation was tested on two different Scania systems, the fuel level displayand the dual circuit steering. Validation was done by comparing the automatically generated trees withmanually generated trees for the two systems showing that the proposed method works as intended. The case studies show that the automated fault tree generation works if the failure propagationinformation exists and can save a lot of time and also minimize the errors made by manuallygenerating the fault trees. The generated fault trees can also be used to validate written requirementsto by analyzing the fault trees created from them.

  • 289.
    Andersson, Johan
    Linköping University, Department of Electrical Engineering.
    Rekommendationer för införande av public key infrastructure2002Independent thesis Basic level (professional degree)Student thesis
    Abstract [en]

    The use of insecure networks -such as the Internet- to send and receive information has made the need for preventing unauthorised people reading it yet more important. One of the easiest way to do this is through public key cryptography. However, the problem with this solution is how to tie a specific public key to a certain subject. This is solved by letting a trusted third party issue a certificate that holds, as a minimum, the name of the subject and the subject's public key along with the issuer's digital signature on the information. The rules we make for issuing, revoking and verifying of certificates and the entities that are being used to do so are called PKI - Public Key Infrastructure. In this thesis we shall se what PKI really is in a more detailed way and which entities it constitutes of. We will also investigate some of the areas in which we could make use of it, for instance secure e-mail and virtual private networks. Next, we will look into some of the drawbacks with PKI and what you should think of in order to aviod these. Finally, we'll give recommendations for the implementation itself. As for the theory of cryptography, the basics is presented to the interested reader in a separate appendix.

  • 290.
    Andersson, Johan
    et al.
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Wyckman, Oscar
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Modeling of Fuel Dynamics in a Small Two-Stroke Engine Crankcase2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    For any crankcase scavenged two-stroke engine, the fuel dynamics is not easily predicted. This is due to the fact that the fuel has to pass the crankcase volume before it enters the combustion chamber. This thesis is about the development of a model for fuel dynamics in the crankcase of a small crankcase scavenged two-stroke engine that gives realistic dynamic behavior.

    The crankcase model developed in this thesis has two parts. One part is a model for wall wetting and the other part is a model for concentration of evaporated fuel in the crankcase. Wall wetting is a phenomenon where fuel is accumulated in fuel films on the crankcase walls. The wall wetting model has two parameters that have to be tuned. One is for the fraction of fuel from the carburetor that is not directly evaporated and one parameter is for the evaporation time of the fuel film.

    The thesis treats tuning of these parameters by running the model with input data from measurements. Since not all input data are possible to measure, models for these inputs are also needed. Hence, development of simple models for air flows, fuel flow, gas mixing in the exhaust and the behavior of the λ-probe used for measurements are also treated in this thesis.

    The parameter estimation for the crankcase model made in this thesis results in parameters that corresponds to constant fraction of fuel from the carburetor that evaporates directly and a wall wetting evaporation rate that increases with increasing engine speed. The parameter estimation is made with measurements at normal operation and three specific engine speeds. The validity of the model is limited to these speeds and does not apply during engine heat-up.

    The model is run and compared to validation data at some different operation conditions. The model predicts dynamic behavior well, but has a bias in terms of mean level of the output λ. Since this mean value depends on the relation between input air and fuel flow, this bias is probably an effect of inaccuracy in the simple models developed for these flows.

  • 291.
    Andersson, Jonny
    Linköping University, Department of Electrical Engineering.
    Automatic test vector generation and coverage analysis in model-based software development2005Independent thesis Basic level (professional degree), 20 points / 30 hpStudent thesis
    Abstract [en]

    Thorough testing of software is necessary to assure the quality of a product before it is released. The testing process requires substantial resources in software development. Model-based software development provides new possibilities to automate parts of the testing process. By automating tests, valuable time can be saved. This thesis focuses on different ways to utilize models for automatic generation of test vectors and how test coverage analysis can be used to assure the quality of a test suite or to find "dead code" in a model. Different test-automation techniques have been investigated and applied to a model of an adaptive cruise control system (ACC) used at Scania. Source code has been generated automatically from the model, model coverage and code coverage has therefore been compared. The work with this thesis resulted in a new method to create test vectors for models based on a combinatorial test technique.

  • 292.
    Andersson, K. Ola
    Linköping University, Department of Electrical Engineering. Linköping University, The Institute of Technology.
    Studies on performance limitations in CMOS DACs2002Licentiate thesis, monograph (Other academic)
    Abstract [en]

    The digital-to-analog converter (DAC) is a bottle neck in broadband communication systems. High update rates are required in combination with high accuracy. In this work, we study factors that limit the performance of current-steering DACs, focusing on the linearity properties of DACs for telecommunication applications like digital subscriber lines (DSL).

    There are many different sources of nonlinear behavior in current-steering DACs. Static errors dominate the low-frequency behavior, whereas the high-frequency behavior is dominated by dynamic errors. The static errors are mainly caused by mismatch between components and finite output resistance in the current sources. The dynamic nonlinearity caused by parasitic capacitance in transistors and wires is of special interest in this work. Two closely related types of models of this dynamic nonlinearity were developed.

    The linearity requirements on the converters for high-speed telecommunication applications can be hard to meet using a straightforward approach. Various methods for improving the linearity of DACs are studied in this work. Some of the methods, like dynamic element matching (DEM) and a novel differential DAC architecture, rely on redundant coding to improve the linearity. Two methods utilizing models of the dynamic nonlinearity caused by the parasitic capacitance in the current sources were also developed. One of the methods utilizes a feedback similar to delta-sigma modulation to spectrally shape the distortion. The other method is a type of predistortion where the input is modified in order to yield an improved output that is closer to the desired output, compared with using the original input.

    CMOS technology is popular for implementation of integrated circuits. Two main advantages of CMOS, compared with, e.g., bipolar technology, is low cost and the possibility of designing circuits with relatively low power consumption.

    CMOS is also the preferred technology for implementing large systems on a single chip with both analog and digital blocks. Three different current-steering CMOS DACs were developed in this work, and are presented in the thesis. Measurement results show close resemblance with the simulation results obtained from the developed models.

  • 293.
    Andersson, Karl
    Linköping University, Department of Electrical Engineering.
    Modellering av kontrollenhet för JAS39 Gripens hjälpkraftsystem2007Independent thesis Basic level (professional degree), 20 points / 30 hpStudent thesis
    Abstract [en]

    Simulation is an important tool for verification and validation. Time and money can be saved using simulation instead of flight tests. Achieving satisfying results demands precise models. A new model for JAS39 Gripen’s auxiliary power and engine starting system, APESS, is presented. The objective of this thesis is to develop a more accurate model of APESS and its control unit, APECU. The model was created in MATRIXX. Models are created in MATRIXX using a graphical interface. In MATRIXX, it is possible to generate C-code which is a useful feature.

    Models for the APECU, APU, valves and sensors has been created. The models are then tested and verified using data from test flights.

    The result is a more accurate model for SYSIM. The created control unit model can be used in Easy5. Simulation in MATRIXX has become a useful educational tool.

    One model for three purposes will decrease the amount of nesesary work each system or model update brings. Keeping the model description up to date is also easier.

  • 294.
    Andersson, Kenneth
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Medical Informatics.
    Andersson, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Johansson, Peter
    ISY LiTH.
    Forchheimer, Robert
    Linköping University, Department of Electrical Engineering.
    Knutsson, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Motion compensation using backward prediction and prediction refinement2003In: Signal Processing: Image Communication, ISSN 0923-5965, Vol. 18, no 5, p. 381-400Article in journal (Refereed)
    Abstract [en]

    This paper presents new methods for use of dense motion fields for motion compensation of interlaced video. The motion estimation is based on previously decoded field-images. The motion is then temporally predicted and used for motion compensated prediction of the field-image to be coded. The motion estimation algorithm is phase-based and uses two or three field-images to achieve motion estimates with sub-pixel accuracy. To handle non-constant motion and the specific characteristics of the field-image to be coded, the initially predicted image is refined using forward motion compensation, based on block-matching. Tests show that this approach achieves higher PSNR than forward block-based motion estimation, when coding the residual with the same coder. The subjective performance is also better.

  • 295.
    Andersson, Kenneth
    et al.
    Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Johansson, Peter
    Linköping University, Department of Electrical Engineering, Image Coding. Linköping University, The Institute of Technology.
    Forchheimer, Robert
    Linköping University, Department of Electrical Engineering, Image Coding. Linköping University, The Institute of Technology.
    Knutsson, Hans
    Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Backward-forward motion compensated prediction2002In: Proceedings of ACIVS 2002 (Advanced Concepts for Intelligent Vision Systems), Ghent, Belgium, September 9-11, 2002, 2002, p. 260-267Conference paper (Refereed)
    Abstract [en]

    This paper presents new methods for use of dense motion fields for motion compensation of interlaced video. The motion is estimated using previously decoded field-images. An initial motion compensated prediction is produced using the assumption that the motion is predictable in time. The motion estimation algorithm is phase-based and uses two or three field-images to achieve motion estimates with sub-pixel accuracy. To handle non-constant motion and the specific characteristics of the field-image to be coded, the initially predicted image is refined using forward motion compensation, based on block-matching. Tests show that this approach achieves higher PSNR than forward block-based motion estimation, when coding the residual with the same coder. The subjective performance is also better.

  • 296.
    Andersson, Kim
    Linköping University, Department of Electrical Engineering.
    Pressure Monitoring and Fault Detection of an Anti-g Protection System2010Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    When flying a fighter aircraft such as the JAS 39 Gripen, the pilot is exposed to high g-loads. In order to prevent the draining of blood from the brain during this stress an anti-g protection system is used. The system consists of a pair of trousers, called the anti-g trousers, with inflatable bladders. The bladders are filled with air, pressing tightly on to the legs in order to prevent the blood from leaving the upper part of the body.

    The purpose of this thesis is to detect if the pressure of the anti-g trousers is deviating from the desired value. This is done by developing a detection algorithm which gives two kinds of alarm. One is given during minor deviations using a CUSUM test, and one is given at grave deviations, based on different conditions including residual, derivative and time. The thresholds, in which between the pressure should lie in a faultless system, are calculated from the g-load value. The thresholds are based upon given static guidelines for the pressure tolerance area and are modified in order to adapt to the estimated dynamics of the system.

    The values of the input signals, pressure and g-load, were taken from real flight sessions. The validation has been performed using both faultless and faulty flight sequences, with low false alarm rate and no missed detections. All together the detection system is considered to work well.

  • 297.
    Andersson, Magnus
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Experimental Design and Updating of Finite Element Models1997Licentiate thesis, monograph (Other academic)
    Abstract [en]

    This thesis deals with two partly related topics: model updating and actuator/sensor placement concerning finite element (FE) models of large, flexible mechanical structures.

    The importance of accurate dynamical FE models of mechanical structures in, e.g., aviation/aerospace applications are steadily increasing. For instance, a sufficient accurate model may reduce the expenses for ground vibration testing and wind-tunnel experiments substantially. It is therefore of high industrial interest to obtain accurate models of flexible structures. One approach is to improve a parameterized, initial FE model using measurements of the real structure, so-called model updating. For a fast, successful model updating, three requirements must be fulfilled. The model updating must be computationally cheap, which requires an efficient model reduction technique. The cost function describing the deviation between the model output and the measurements must have good convexity properties so that an estimation of the parameters corresponding to the global optimum is likely to be obtained. Finally, the optimization methods must be reliable. A novel mode-pairing free cost function is presented, and together with a proposed general procedure for model updating, a cheap model updating formulation with good parameter estimation properties is obtained.

    Actuator and sensor placement is a part of the experimental design. It is performed in advance of the vibrational experiment in order to ensure high quality measurements. Using a nominal FE model of the structure, an actuator/sensor placement can be made. Actuator/sensor placement tasks are generally discrete, non-convex optimization problems of high complexity. One is therefore restricted to the use of sub-optimal algorithms in order to fulfill time and memory storage requirements. A computationally cheap algorithm for general actuator/sensor placement objectives are proposed. A generalization of an actuator/sensor placement criterion for model updating, and a novel noise-robust actuator placement criterion for experimental modal analysis are proposed.

  • 298.
    Andersson, Magnus
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Model Updating - Identification of Mechanical Structures using Finite Element Models1996In: Proceedings of Reglermöte 1996, 1996, p. 51-55Conference paper (Other academic)
  • 299.
    Andersson, Magnus
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Noise Robust Actuator Placement on Flexible Structures1997Report (Other academic)
    Abstract [en]

    A novel criterion for placement of actuators on flexible mechanical structures is presented. Using simulated "measured modes" obtained from the model, the proposed criterion maximizes the correlation of the measured modes and the normal modes. The measured modes deviate from the normal modes due to damping, measurement noise and process noise. The statistical properties of the criterion are investigated. In simulations the computed actuator locations on a small aircraft-like model shows increased robustness properties against damping, for an acceptable loss of correlation. A computationally cheap actuator placement algorithm is proposed.

  • 300.
    Andersson, Magnus
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology. SAAB AB, Sweden.
    Abrahamsson, Tom
    SAAB AB, Sweden.
    Avoiding Mode Pairing when Updating Finite Element Models1997Report (Other academic)
    Abstract [en]

    Updating nite element models of complex mechanical structures requires some extra considerations. It is stressed that the two most important aspects on updating finite element models are parameter estimation properties and computational expenses. A novel mode-pairing free model updating formulation is found to hav egood parameter estimation properties. The computational expenses are reduced with a semi-fixed modal basis, kept fixed during several iterations.

3456789 251 - 300 of 8965
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf