Change search
Refine search result
23456 201 - 250 of 279
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • 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.
  • 201. Nordebo, Sven
    et al.
    Claesson, Ingvar
    Dahl, Mattias
    On the Use of Remes Multiple Exchange Algorithm for Linear--Phase FIR Filters with General Specifications2000In: IEEE Transactions on Education, ISSN 0018-9359, E-ISSN 1557-9638, Vol. 43, no 4, p. 460-463Article in journal (Refereed)
  • 202. Nordebo, Sven
    et al.
    Claesson, Ingvar
    Dahl, Mattias
    Optimum Array Design by Semi--Infinite Quadratic Programming1999Conference paper (Refereed)
  • 203. Nordebo, Sven
    et al.
    Claesson, Ingvar
    Zang, Zhuquan
    Optimum Window Design by Semi-Infinite Quadratic Programming1999In: IEEE Signal Processing Letters, ISSN 1070-9908, E-ISSN 1558-2361, Vol. 6, no 10, p. 262-265Article in journal (Refereed)
  • 204. Nordebo, Sven
    et al.
    Dahl, Mattias
    Claesson, Ingvar
    Complex approximation with applications to antenna array pattern synthesis2001Conference paper (Refereed)
  • 205. Nordebo, Sven
    et al.
    Dahl, Mattias
    Claesson, Ingvar
    Complex Chebyshev Approximation Using Conventional Linear Programming2000Conference paper (Refereed)
  • 206. Nordebo, Sven
    et al.
    Zang, Zhuquan
    Application of Infinite Dimensional Linear Programming to FIR Filter Design with Time Domain Constraints1998Conference paper (Refereed)
    Abstract [en]

    Previously the envelope-constrained filtering problem was formulated as designing an FIR filter such that the filter's L2 norm is minimized subject to the constraint that its response to a specified input pulse lies within a prescribed envelope. In this paper, we recast this filter design problem as a frequency-domain L infinity optimization problem with time-domain constraints. Motivations for solving this problem are given. Then recently developed infinite dimensional linear programming techniques are used for the design of the required FIR filter. For illustration, we apply the approach to a numerical example which deals with the design of an equalization filter for a digital transmission channel.

  • 207. Nordebo, Sven
    et al.
    Zang, Zhuquan
    Semi-Infinite Linear Programming: A Unified Approach to Digital Filter Design with Time- and Frequency-domain Specifications1999In: IEEE transactions on circuits and systems. 2, Analog and digital signal processing (Print), ISSN 1057-7130, E-ISSN 1558-125X, Vol. 46, no 6, p. 765-775Article in journal (Refereed)
    Abstract [en]

    Using the recently developed semi-infinite linear programming techniques and Caratheodory's dimensionality theory, we present a unified approach to digital filter design with time and/or frequency-domain specifications. Through systematic analysis and detailed numerical design examples, we demonstrate that the proposed approach exhibits several salient features compared to traditional methods: 1) using the unified approach, complex responses can be handled conveniently without resorting to discretization; 2) time-domain constraints can be included easily; and 3) any filter structure, recursive or nonrecursive, can be employed, provided that the frequency response can be represented by a finite-complex basis. More importantly, the solution procedure is based on the numerically efficient simplex extension algorithms. As numerical examples, a discrete-time Laguerre network is used in a frequency-domain design with additional group-delay specifications, and in a H-infinity-optimal envelope constrained filter design problem. Finally, a finite impulse response phase equalizer is designed with additional frequency domain H-infinity, robustness constraints.

  • 208. Nordebo, Sven
    et al.
    Zang, Zhuquan
    Claesson, Ingvar
    A Semi-Infinite Quadratic Programming Algorithm with Applications to Array Pattern Synthesis2001In: IEEE transactions on circuits and systems. 2, Analog and digital signal processing (Print), ISSN 1057-7130, E-ISSN 1558-125X, Vol. 48, no 3, p. 225-232Article in journal (Refereed)
  • 209. Nordholm, Jörgen
    et al.
    Nordholm, Sven
    Mohammed, Abbas
    Claesson, Ingvar
    Blind Adaptive spatial Equalisation in S-UMTS-system1999Conference paper (Refereed)
    Abstract [en]

    Today there is an increasing demand for a higher data rate in both the existing and future mobile communication system. With higher data rate, the InterSymbol Interference (ISI) problem will also increase. In this paper, a Spatial Normalised Adaptive Constant Modulus Algorithm (SA-NCMA) equaliser will be presented that will compensate for the ISI problem.

  • 210. Nordholm, Sven
    et al.
    Claesson, Ingvar
    Grbic, Nedelko
    Optimal and Adaptive Microphone Arrays for Speech Input in Automobiles2001In: Microphone Arrays: Signal Processing Techniques and Applications / [ed] Ward, Michael S. Brandstein and Darren B., Springer Verlag , 2001, p. 307-330Chapter in book (Other academic)
    Abstract [en]

    In this chapter, speech enhancement and echo cancellation for hands-free mobile telephony is discussed. A number of microphone array methods have been tested and results from car measurements are given. Traditional methods such as linearly constrained beamforming and generalised sidelobe cancellers are discussed as well as array gain optimisation methods. An in-situ calibrated method which gives an over all improved performance is also presented. Algorithms such as LS and NLMS are used to find optimal weights. The improved performance using an LS-method is shown. This has however limitations in realtime implementations because of the numerical complexity. By introducing subband processing these limitations can be avoided. The results show a noise suppression of approximately 18 dB and hands-free loudspeaker suppression of the same order.

  • 211. Nordholm, Sven
    et al.
    Leung, Ye Hong
    A Theoretical Study of Generalised Sidelobe Cancellers in an Isotropic Noise Field1999Conference paper (Refereed)
  • 212. Nordholm, Sven
    et al.
    Nordberg, Jörgen
    Claesson, Ingvar
    Beamforming and Interference Cancellation for Capacity Gain in mobile Networks2000In: Annals of Operations Research, ISSN 0254-5330, E-ISSN 1572-9338, Vol. 98, no 1-4, p. 235-253Article in journal (Refereed)
    Abstract [en]

    The growth of wireless communication continues. There is a demand for more user capacity from new subscribers and new services such as wireless internet. In order to meet these expectations new and improved technology must be developed. A way to increase the capacity of an existing mobile radio network is to exploit the spatial domain in an efficient way. An antenna array adds spatial domain selectivity in order to improve the Carrier-to Interference ratio (C/I) as well as Signal-to-Noise Ratio (SNR). An adaptive antenna array can further improve the C/I by suppressing interfering signals and steer a beam towards the user. The suggested scheme is a combination of a beamformer and an interference canceller. The proposed structure is a circular array consisting of K omni-directional elements and combines fixed beamforming with interference cancelling. The fixed beamformers use a weight matrix to form multiple beams. The interference cancelling stage suppresses undesired signals, leaking into the desired beam. The desired signal is filtered out by the fixed beamforming structure. Due to the side-lobes, interfering signals will also be present in this beam. Two alternative strategies were chosen to cancel these interferers; use the other beamformer outputs as inputs to an adaptive interference canceller; or regenerate the outputs from the other beamformer outputs and generate clean signals which are used as inputs to adaptive interference cancellers. Resulting beamformer patterns as well as interference cancellation simulation results are presented. Two different methods have been used to design the beamformer weights, Least Square (LS) and minimax optimisation. In the minimax optimisation a semi-infinite linear programming approach was used. Although the optimisation plays an essential role in the performance of the beamformer, this paper is focused on the application rather then the optimisation methods.

  • 213.
    Numminen, Michael
    Blekinge Institute of Technology, Department of Telecommunications and Signal Processing.
    Aktiv bullerdämpning i entreprenadmaskin1998Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [sv]

    En mätserie utfördes på en entreprenadmaskin där entreprenadmaskinen var en tandemvält. Data som spelades in på en DAT-bandspelare var motorns rotationsfrekvens, valsarnas vibrationer samt ljudfältet i kabinen. Den insamlade datamängden analyserades m.a.p dess spektra samt ljudnivåer. Vidare predikterades resultat till implementering av det adaptiva systemet ur dessa insamlade data. Viss laboration utfördes på en modell av det adaptiva systemet m.h.a insamlade data. En implementation av det adaptiva systemet utfördes på entreprenadmaskinen samt en slutlig mätserie gjordes en analys av prestandan.

  • 214.
    Persson, Albin
    et al.
    Blekinge Institute of Technology, Department of Telecommunications and Signal Processing.
    Karlsson, Jimi
    Blekinge Institute of Technology, Department of Telecommunications and Signal Processing.
    Device and Service Discovery in Bluetooth Networks2002Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    In view of Bluetooth?s growing popularity a lot of research is being done to improve the performance of Bluetooth. Most of the research being performed prerequisites that a connection has already been made. Due to the frequency hopping spread spectrum used by Bluetooth the connection establishment is not as easy as it seams. Two processes have been derived to bridge the frequency discrepancies between devices, inquiry and page. In this thesis, we study the inquiry and page processes and the time it takes to complete a connection with no, one or two voice channels present at the initiating device. We have found the times to complete the processes to be lengthy at best, unreasonably long if there is voice traffic present. Through optimisation, we have decreased the mean time to connect. We propose some changes to the default values of a few time outs and variables, which yields a substantial improvement in performance, especially in the case when there is voice traffic present. The changes are in the software only, no changes in hardware are necessary. After a connection is made a client may want to start using the services of the device it is connected to. This is another topic of this thesis. Bluetooth does not provide means of accessing a service, only discovering it. Thus, there is the need for higher-level protocols for accessing services. We have investigated some of the service discovery protocols currently available.

  • 215. Persson, Per
    Annealing Based Optimization Methods for Signal Processing Applications2003Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis, a class of combinatorial optimization methods rooted in statistical mechanics and their use in signal processing applications will be discussed. The thesis consists of two separate parts. The first part deals with the rationale for my work and also covers the background information necessary to put the second part, which consists of a number of papers, in context. There are (at least) two sides to an optimization problem---the problem statement arising from an application or a design and the selection of an algorithm to solve the problem. In this work the problem statements are practical problems, of combinatorial nature, frequently encountered in signal processing and the algorithms of choice are annealing based algorithms, founded in statistical mechanics. From my work, it is my experience that solving a particular problem often leads to new developments on the part of the algorithm which, in turn, open up possibilities to apply the modified algorithm to a new set of problems, leading to a continuously improving algorithm and a growing field of applications. The included papers deal with the application of annealing optimization methods to the problems of configuring active noise and vibration control systems, digital filter design and adaptive filtering. They also describe the successive development of a highly efficient entropy-directed deterministic annealing (EDDA) optimization algorithm detailed in the final paper.

  • 216. Persson, Per
    et al.
    Johansson, Sven
    Håkansson, Lars
    Claesson, Ingvar
    Lateral Vibration Reduction in a Train Car Using Active Control Technologies2001Conference paper (Refereed)
    Abstract [en]

    The problem of low-frequency lateral train-car vibration is an important issue surrounding the design of high-speed trains. Passive solutions such as stiffening the car chassis are impractical because of the weight increase. Semi-passive solutions, such as modifying the structural dynamics of the carbody through non-rigid coupling of heavy underfloor equipment does not incur a weight penalty, but does not sufficiently reduce the vibrations. However, computer simulations based on signals derived from a dynamic computer model of a train car indicates that the incorporation of an active control system, in addition to the semi-passive approach, is likely to give a substantial reduction in the lateral vibration level. The paper addresses some design aspects and different controller structures for the active control system. The adaptive controller is based either on feedforward or feedback control strategy. Results from computer simulations indicate that a feedback system would function as well as a multiple-reference feedforward system. However, by using a robust feedback-LMS controller the complexity of the control system may be reduced substantially. The control results illustrate an attenuation of the lateral train-car vibration by up to 15 dB.

  • 217. Persson, Per
    et al.
    Johansson, Sven
    Håkansson, Lars
    Claesson, Ingvar
    Samuels, Timothy
    Feedback-LMS control of lateral vibration in a train car2001Conference paper (Refereed)
    Abstract [en]

    The problem of low-frequency lateral train-car vibration is an important issue surrounding the design of high-speed trains. Passive solutions such as stiffening the car chassis are impractical because of the weight increase. Semi-passive solutions, such as modifying the structural dynamics of the carbody through non-rigid coupling of heavy underfloor equipment does not incur a weight penalty, but does not sufficiently reduce the vibrations. However, computer simulations based on signals derived from a dynamic computer model of a train car indicates that the incorporation of a multiple-reference feedforward active control system, in addition to the semi-passive approach, is likely to effect a substantial reduction in the lateral vibration level. The complexity of the control system may be reduced by using a robust feedback-LMS controller. Results from computer simulations indicate that a feedback system would function as well as, and potentially better than, a feedforward system. The control results illustrate attenuation of the lateral train-car vibration of up to 15 dB.

  • 218. Persson, Per
    et al.
    Lagö, Thomas L
    Claesson, Ingvar
    Active vibration reduction in a light weight high speed train bogie1999Conference paper (Refereed)
    Abstract [en]

    Vibration-induced noise in the car of train is of great interest since low weight is important, but makes the structure more resonant. One excitation source is the sleeper frequency which gives rise to a periodic excitation. This paper describes an approach to isolate the vibrations caused by the sleepers in such a way that the noise inside the cabin is reduced. An LMS algorithm with four inertial mass actuators fitted to the bogie with control microphones placed in the cabin. The tests were performed on an experimental light weight bogie fitted to a test car, in both lab environment and in full scale tests on track at full speed (200 km/h).

  • 219. Persson, Per
    et al.
    Lagö, Thomas L
    Norberg, Arvid
    Active Control of Sleeper-induced Sound in a High Speed Train1999Conference paper (Refereed)
    Abstract [en]

    Vibration-induced noise in train cars is an area that receives a great deal of interest at the moment. Due to economical and environmental issues, manufacturers are cutting the weight-budget for future trains to achieve a lower total life-cycle cost. This has a negative impact on the interior noise and passenger comfort and to be competitive new methods to reduce the negative side effect are sought. This paper describes an active control approach to isolating the car from bogie vibrations in such a way that the noise inside the car is reduced. An active control system with four inertial mass actuators fitted to an experimental light weight bogie were used to control bogie vibrations and noise inside the car. Several tests were performed in both a lab environment and on track at full speed.

  • 220. Persson, Per
    et al.
    Nordebo, Sven
    Claesson, Ingvar
    A Multi-Mode Mean Field Annealing Technique to Design Recursive Digital Filters2001In: IEEE transactions on circuits and systems. 2, Analog and digital signal processing (Print), ISSN 1057-7130, E-ISSN 1558-125X, Vol. 48, no 12, p. 1151--1154Article in journal (Refereed)
    Abstract [en]

    The Multi-Mode Mean Field Annealing (MM-MFA) approach to combinatorial optimization is introduced as a tool to design recursive (IIR) digital filters with discrete coefficients. As an application example demonstrating the potential of the method we consider the design of structurally passive IIR digital filters realized as the sum of two allpass functions. The new design technique facilitates the solution of non-trivial filter design problems such as satisfying a general frequency specification by solving a combinatorial optimization problem over discrete coefficients and a max-norm cost. The final solution is not guaranteed to be a globally optimal solution but the convergence time is short enough to allow interactive design even for large problems.

  • 221. Persson, Per
    et al.
    Nordebo, Sven
    Claesson, Ingvar
    An Adaptive Filtering Algorithm using Mean Field Annealing Techniques2002Conference paper (Refereed)
    Abstract [en]

    We present a new approach to discrete adaptive filtering based on the mean field annealing algorithm. The main idea is to find the discrete filter vector that minimizes the matrix form of the Wiener-Hopf equations in a least-squares sense by a generalized mean field annealing algorithm. It is indicated by simulations that this approach, with complexity O(M^2) where M is the filter length, finds a solution comparable to the one obtained by the recursive least squares (RLS) algorithm but without the transient behavior of the RLS algorithm. Further advantages of the proposed algorithm over other methods such as the recursive least-squares algorithm are that the filter coefficients are always limited and that it facilitates fast recovery after an abrupt system change.

  • 222. Persson, Per
    et al.
    Nordebo, Sven
    Claesson, Ingvar
    Blekinge Institute of Technology, Department of Signal Processing.
    Design of Digital Filters with General Hardware Constraints by Mean Field Annealing2001Conference paper (Refereed)
    Abstract [en]

    The mean field annealing (MFA) algorithm is presented as an efficient tool to design digital filters with discrete coefficients and hardware constraints. As an application example the algorithm is used to design a finite wordlength digital filter with a simple hardware constraint. The ability of the deterministic MFA algorithm to approximate the mean behavior of the stochastic simulated annealing algorithm is indicated by numerical results.

  • 223. Persson, Per
    et al.
    Nordebo, Sven
    Claesson, Ingvar
    Design of discrete coefficient FIR filters by a fast entropy-directed deterministic annealing algorithm2005In: IEEE Transactions on Signal Processing, ISSN 1053-587X , Vol. 52, no 3, p. 1006-1014Article in journal (Refereed)
    Abstract [en]

    In this paper, we present an entropy-directed deterministic annealing optimization algorithm and show its applicability to the problem of designing digital filters with discrete coefficients, each implemented as a sum of signed power-of-two terms and additional general hardware constraints. The algorithm is based on analogies from statistical mechanics and is related to the well-known mean field annealing algorithm. It utilizes estimates of conditional entropy to prune the problem during the optimization, thereby reducing the computational time by 30 to 50%. In conjunction with a scheme to compute the value of the objective function as a sequence of updates, this approach leads to a very fast algorithm. As an application example demonstrating the potential of the new method, we consider the design of digital filters with discrete coefficients consisting of a minimum number of signed power-of-two terms. © 2005 IEEE.

  • 224. Persson, Per
    et al.
    Nordebo, Sven
    Claesson, Ingvar
    Hardware Efficient Digital Filter Design by Multi-Mode Mean Field Annealing2001In: IEEE Signal Processing Letters, ISSN 1070-9908, E-ISSN 1558-2361, Vol. 8, no 7, p. 193-195Article in journal (Refereed)
    Abstract [en]

    The multi-mode mean field annealing (MM-MFA) approach is introduced as an efficient tool to design digital filters with discrete coefficients, each implemented as a sum of signed power-of-two terms, and additional general hardware constraints. As an application example demonstrating the potential of the new method we consider the design of a linear phase non-recursive (FIR) filter with a least squares criterion and minimum number of power-of-two terms.

  • 225. Pettersson, Linus
    Vibration Analysis of a Boring Bar2002Report (Other academic)
    Abstract [en]

    In boring operations the vibrations are a cumbersome part of the manufacturing process. This report puts the vibrations under scrutiny and the vibrations were measured both in the cutting speed direction and the cutting depth direction. The cutting process seems to be a time varying process and contains nonstationary as well as nonlinear parameters that are not under control. The experiments showed that the vibrations were usually dominated by the first resonance frequency in either of the two directions of the boring bar. Sample probability density estimates of the vibration records points to that the probability densities are varying from sinusiodal probability shape to gaussian shape. They also indicate that shape of the two directions could be of different probability density function from the same vibration record. Stationarity tests show, besides that the processes usually are nonstationary, that it is possible to extract short time stationary segments within a vibration record. The problem with force modulation in rotary machinery, which appears as side band terms is the spectrum, is also addressed. Furthermore, the resonance frequencies of the boring bar are correlated to an approximate theoretical beam model. The theoretical calculation of the boring bar deflection corresponds well with the experimental results from the modal analysis and the operating deflection shape analysis.

  • 226. Pettersson, Linus
    Vibrations in Metal Cutting: Measurement, Analysis and Reduction2002Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Vibration and noise in metal cutting are ubiquitous problems in the workshop. The turning operation is one kind of metal cutting that exhibits vibration related problems. Today the industry aims at smaller tolerances in surface finish. Harder regulations in terms of the noise levels in the operator environment are also central. One step towards a solution to the noise and vibration problems is to investigate hat kind of vibrations that are present in a turning operation. The vibrations in a boring operation have been put under scrutiny in the first part of this thesis. Analytical models have been compared with experimental results and he vibration pattern has been determined. The second part of the thesis deals with active vibration control in external turning operations. By embedding a piezo-ceramic actuator and an accelerometer into a tool holder it was possible to obtain a solution that can be fitted in a standard lathe. The control system consists of the active tool holder, a control system based on the filtered-X LMS algorithm and an amplifier designed for capacitive loads. The vibration level using this technique can be reduced by as much as 40 dB during an external turning operation.

  • 227. Pettersson, Linus
    et al.
    Adolfsson, Stefan
    Bolmsjö, Gunnar
    Claesson, Ingvar
    Detection in a Robotised Short Circuting GMA Welding using Neural Networks1999Conference paper (Refereed)
    Abstract [en]

    Today it is both time and cost consuming to check the quality of a weld when it is done off-line by an experienced weld operator. Therefor the need for an automatic detection is urgent in order to reduce production costs. There are systems for monitoring the quality of a weld commercially available but there is still some research that has to be done in this area in order to increase the reliability. The method presented in this paper is neural network based and considers short circuiting GMA welding, but there is no obstacle for this solution to work on other types of robotised welding. By presenting the weld voltage to a neural network, the network is able to detect defects in the weld joint. Testresults have shown that the detection rate is 100 percent and false alarms are nonexisting.

  • 228. Pettersson, Linus
    et al.
    Håkansson, Lars
    Claesson, Ingvar
    Olsson, Sven
    Active Control of Boring Bar Vibrations in Cutting Operations2002Conference paper (Refereed)
    Abstract [en]

    Internal turning or boring operations have a history of being a cumbersome manufacturing process. The manufacturing industries are facing tougher tolerances of their product surfaces and a desire to process hard to cut materials and therefore the vibrations must be kept to a minimum. An increase in the productivity is also interesting from a production point of view. When cutting in pre-drilled holes the boring bar is usually long and slender and is thereby inclined to vibrate destructively concerning the machining result. The knowledge of the vibrations involved in boring operations and active control of external turning operations, have given a good basis for the active control solution in boring operations. The active control solution is based on a standard boring bar with an embedded piezo ceramic actuator placed at the peak modal strain of the boring bar. An accelerometer is also included in the design, mounted as close as possible to the cutting tool. The control algorithm is a filtered X LMS algorithm built on a feedback approach since the original excitation, the cutting process, cannot be observed directly. Preliminary results show reduction of the vibration in the boring bar by up to 30dB.

  • 229. Pettersson, Linus
    et al.
    Håkansson, Lars
    Claesson, Ingvar
    Olsson, Sven
    Active Control of Internal Turning Operations Using a Boring Bar2002Conference paper (Refereed)
    Abstract [en]

    Vibrations in internal turning or boring operations are usually a cumbersome part of the manufacturing process. The manufacturing industries are having problems with these kinds of cutting operations. When cutting in pre-drilled holes the cross sectional area of the boring bar is limited at the same time as it is long. Since a general boring bar is long and slender it is sensitive to external excitation and thereby inclined to vibrate. The vibration problem affects the surface finish in particular. The demand for smaller and smaller tolerances of the surface finish leads to that the manufacturing industry seeks for a solution to the boring bar vibration problem. The tool life is also likely to be influenced by the vibrations involved in a cutting operation. Another problem in boring operations is the high noise level in the cutting process. The noise level in the environment of the operators is today more and more regulated, especially in the western world. Active vibration control will reduce the amount of vibrations in the cutting operations. Since the noise is induced by the vibration of the boring bar, the noise level will also be reduced due to the cancellation of the noise source. Preliminary results show reduction of vibrations in the boring bar by up to 30dB.

  • 230. Pettersson, Linus
    et al.
    Håkansson, Lars
    Claesson, Ingvar
    Olsson, Sven
    Active Control of Machine-Tool Vibration in a CNC Lathe Based on an Active Tool Holder Shank with Embedded Piezo Ceramic Actuators2001Conference paper (Refereed)
    Abstract [en]

    In the turning operation chatter or vibration is a frequent problem affecting the result of the machining, and, in particular, the surface finish. Tool life is also influenced by vibration. Severe acoustic noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. These problems can be reduced by active control of machine-tool vibration. However, machine-tool vibration control systems are usually not applicable to a general lathe and turning operation. The physical features and properties of the mechanical constructions or solutions involved regarding the introduction of secondary vibration usually limit their applicability. An active control solution for a general lathe application has been developed. It is based on a standard Industry tool holder with an embedded piezo ceramic actuator and an adaptive feedback controller. The adaptive controller is based on the well known filtered-x LMS-algorithm. It enables substantial reduction of the vibration level by up to 40 dB at 3.4 kHz.

  • 231. Pettersson, Linus
    et al.
    Håkansson, Lars
    Claesson, Ingvar
    Olsson, Sven
    Active Control of Machine-Tool Vibration in Cutting Operations in a General Lathe2001Conference paper (Refereed)
    Abstract [en]

    In the general lathe the turning operation chatter or vibration is a frequent problem affecting the result of the machining, and, in particular, the surface finish. Tool life is also influenced by vibration. Severe acoustic noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. These problems can be reduced by active control of machine-tool vibration. In a general lathe the physical features and properties of an ctive control system usually limit their applicability. By using piezo ceramic actuators some constraints regarding the mechanical construction of the active tool holder can be circumvented. An active control solution for a general lathe application has been developed. It is based on a standard industry tool holder with an embedded piezo ceramic actuator and an adaptive feedback controller. The adaptive controller is based on the well known filtered-x LMS-algorithm. It enables substantial reduction of the vibration level by up to 40 dB at 3.4 kHz.

  • 232. Pettersson, Linus
    et al.
    Håkansson, Lars
    Claesson, Ingvar
    Olsson, Sven
    Active Control of Machine-Tool Vibration in Cutting Operations using Piezo Ceramic Actuators2001Conference paper (Refereed)
  • 233. Pettersson, Linus
    et al.
    Håkansson, Lars
    Claesson, Ingvar
    Olsson, Sven
    Adaptive Control of Machine-Tool Vibration Based on an Active Tool Holder Shank with an Embedded Piezo Ceramic Actuator2001Conference paper (Refereed)
    Abstract [en]

    In the turning operation chatter or vibration is a common problem affecting the result of the machining, and, in particular, the surface finish. Tool life is also influenced by vibration. Severe acoustic noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. These problems can be reduced by active control of machine-tool vibration. However, machine-tool vibration control systems are usually not applicable to a general lathe and turning operation. The physical features and properties of the mechanical constructions or solutions involved regarding the introduction of secondary vibration usually limt their applicability. An adaptive active control solution for a general lathe application has been developed. It is based on a standard industry tool holder shank with an embedded piezo ceramic actuator and an adaptive feedback controller. The adaptive controller is based on the well known filtered-x LMS-algorithm. It enables substantial reduction of the vibration level by up to 40 dB at 3.4 kHz.

  • 234. Popescu, Adrian
    IP QoS: The Challenge of Building Efficient Networks2002Other (Other academic)
    Abstract [en]

    The tutorial is about the main challenges in developing the new Internet. Different aspects related to IP QoS are analyzed. Furthermore, a theoretical case-study on resource engineering for supporting Service Level Agreements (SLAs) on IP networks is used to support the analysis.

  • 235. Popescu, Adrian
    Traffic Self-Similarity2001Other (Other academic)
    Abstract [en]

    The tutorial is about traffic self-similarity. It is a review of basic concepts in traffic self-similarity. It is about definitions of self-similarity, key properties, measurements, models, generation of synthetic traces, revealing of specific properties in self-similar traffic, origins as well as performance impacts

  • 236. Popescu, Adrian
    et al.
    Ayani, Rassul
    Modeling and Analysis of Multi-Access Mechanisms in SUPERLAN1999In: Network Systems Design / [ed] Gelenbe, Erol; Bagchi, Kallol K.; Zobrist, George W., Gordon and Breach Science Publishers , 1999, p. 47-68Chapter in book (Other academic)
    Abstract [en]

    Today, new multi-Gbps LANs are designed to support a wide range of applications generating isochronous and nonisochronous traffic at arbitrary bit rates. The growing demand for high bandwidth networking, under increasing performance constraints, has posed fundamental challenges to LAN design and implementation. Three fundamental bottlenecks exist in a multi-Gbps LAN environment that must be handled in order to achieve optimal performance. These are: opto-electronic bottleneck, service bottleneck, and processing bottleneck. A novel architectural solution is proposed to open up these bottlenecks. Total network throughput of about 20 Gbps is achievable. Performance modeling, analysis and evaluation is reported for a class of Medium Access Protocols (MAC) for isochronous traffic. The performance results show good and very good performance for this solution.

  • 237. Popescu, Adrian
    et al.
    Jena, Ajit K.
    Nilsson, Arne A.
    Modeling and Evaluation of Internet Applications2003Conference paper (Refereed)
    Abstract [en]

    The paper presents a modeling and evaluation study of the characteristics of SMTP and HTTP applications in terms of user behavior, nature of contents transferred and application layer protocol exchanges. Results are reported on measuring, modeling and analysis of application level traces collected, at client and server ends, from different environments such as university networks and commercial Frame Relay networks. The methodologies used for capturing traffic flows and for modeling are reported. Statistical models have been developed for diverse parameters of applications, which can be useful for building synthetic workloads for simulation and benchmarking purposes. Both applications possess a session oriented structure. Within each session, a number of transactions may occur, and this number has been modeled as well.

  • 238. Popescu, Adrian
    et al.
    Jena, Ajit K.
    Nilsson, Arne A.
    Resource Engineering for Internet Applications2003Conference paper (Refereed)
    Abstract [en]

    The focus of the paper is on resource engineering for supporting Service Level Agreements (SLAs) in IP networks. We review some of the recent developments in Internet service architecture and protocol developments as well as some of the most important challenges still to be considered. An important performance metrics that must be considered in developing the new Internet is regarding the delay and the delay variation/jitter. Connected with this, a case-study is reported on end-to-end delay performane in a simple model for best-effort Internet where the bandwidth is not a commodity. The case-study is based on a client-server simulation model. The client and the server nodes are running applications like HTTP and SMTP, and they are placed in two sites separated by an Internet cloud. Performance issues of Short Range Dependence (SRD) and Long Range Dependence (LRD) traffic under different resource control regimes are compared. The results highlight the importance of the queueing delay at the WAN ingress point, which is due to the significant bandwidth differences that may exist, in this case, between the LAN and WAN link layers. The results also highlight the role TCP window size and Frame Relay Permanent Virtual Channel (FR PVC) control mechanisms play in the provision of delay performance for Internet services.

  • 239. Pruthi, Parag
    et al.
    Ilie, Dragos
    Popescu, Adrian
    Application Level Performamce of Multimedia Services1999Conference paper (Refereed)
    Abstract [en]

    Quality of Service (QoS) is a difficult term to define for multimedia applications. The main reason is that both audio and video quality are subjective and difficult to quantify. Much work has been done in the past to map the subjective quality of video and audio into measurable quantities. Unfortunately, when it comes to IP environments, not much experience and mathematical work exists that can be used to define robust metrics for measurement of QoS. In this paper, we report on measurements of multimedia QoS and try to map subjective criteria to discrete measurables in terms of packet loss rates, packet delays, and other quantities. We report the results of measurements done at the application level and show how network characteristics affect the perceived quality of multimedia applications. In particular, we analyze the application traffic generated by MBone clients in a distributed network education scenario. In order to measure the traffic, we have implemented software on a non-intrusive probe developed by NIKSUN INC.\footnote{http://www.niksun.com} that can accurately monitor all traffic from a variety of networks. We have developed MBone aware software modules which can not only play back the recorded streams but also provide the essential statistics in real-time. We report in detail the results of our study of a particular end-to-end MBone session.

  • 240. Pruthi, Parag
    et al.
    Ilie, Dragos
    Popescu, Adrian
    Application level performance of multimedia services1999Conference paper (Refereed)
    Abstract [en]

    Quality of Service (QoS) is a difficult term to define for multimedia applications. The main reason is that bath audio and video quality are subjective and difficult to quantify. Much work has been done in the past to map the subjective quality of video and audio into measurable quantities. Unfortunately, when it comes to IP environments, not much experience and mathematical work exists that can be used to define robust metrics for measurement of QoS. In this paper, we report on measurements of multimedia QoS and try to map subjective criteria to discrete measurables in terms of packet loss rates, packet delays, and other quantities. We report the results of measurements done at the application level and show how network characteristics affect the perceived quality of multimedia applications. In particular, we analyze the application traffic generated by MBone clients in a distributed network education scenario. In order to measure the traffic, we have implemented software on a non-intrusive probe developed by NIKSUN INC.* that can accurately monitor all traffic from a variety of networks. We have developed MBone aware software modules which can not only play back the recorded streams but also provide the essential statistics in real-time. We report in detail the results of our study of a particular end-to-end MBone session.

  • 241.
    Rosendahl, Michael
    et al.
    Blekinge Institute of Technology, Department of Telecommunications and Signal Processing.
    Scicluna, David
    Blekinge Institute of Technology, Department of Telecommunications and Signal Processing.
    Active Noise Control In Truck Cabin2002Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    The thesis is based on examinations of sound fields in a truck cabin. The main technical issue was to investigate how an active noise control system would work in a truck cabin, and also how effective it would be.

  • 242.
    Rosengren, Per
    et al.
    Blekinge Institute of Technology, Department of Telecommunications and Signal Processing.
    Nilsson, Andreas
    Blekinge Institute of Technology, Department of Telecommunications and Signal Processing.
    Bumblebee Killer1999Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    A common problem in GSM terminals is an interfering signal nicknamed the “Bumblebee”. This interference is generated by the switching nature of TDMA cellular telephony, the radio circuits are switched on and off with the radio access rate. In GSM, this frequency is approximately 217 Hz, This frequency and its harmonics get into the analog microphone signal, and produce a very annoying periodic noise in the uplink speech. This thesis contains a study of four differerent software solutions, to suppress this interference. These four different methods are denoted, Notch filter, Matched filter, Correlators and Interpolation in frequency. It is shown that the best result is achieved with the Correlatars. Since the frequency comlponents of the Bumblebee are well known, it is possible to estimate the phase and the amplitude of these with Correlators. This is done by correlating the microphone signal with sinusoids having the same frequencies as the Bumblebee, hence the name Correlators. By generating sinusoids with these phase and amplitude estimates, and then subtracting them from the microphone signal, the Bumblebee is suppressed. Since it is subtracted in the time domain it is also possible to consider a recurring pause in the interference caused by the so called idle frame in the transmission.

  • 243. Samuels, Timothy
    et al.
    Persson, Per
    Johansson, Sven
    Håkansson, Lars
    Claesson, Ingvar
    Active control of lateral vibration in a structurally modified train car2000Conference paper (Refereed)
    Abstract [en]

    As trains are continually designed for higher speeds the problem of railcar vibration grows worse. Lateral vibrations in a train car are noticeable to passengers if the frequency contents are lower than approximately 20 Hz, and complaints of nausea are not uncommon. The passive solution of stiffening the car chassis to shift the vibrational frequencies higher results in inflated manufacturing and running costs, and opposes higher travel speeds due to increased weight. Semi-passive solutions, such as modifying the structural dynamics of the carbody by decoupling heavy underfloor equipment, do not sufficiently reduce the vibrations. However, by appending a multi-reference feedforward active vibration controller, a substantial reduction in the lateral vibration level is to be expected. Based on a dynamic computer model of a train car simulating the lateral vibration, which uses as input bogie acceleration data measured on a running train, multiple-input/single-output coherence spectra were estimated to determine a suitable set of reference signals to an active control system. A dual-reference controller implies a theoretical maximum attenuation of 28 dB at the objective frequency of 10 Hz. Control simulations are carried out using different reference signal combinations. Preliminary results indicate lateral vibration attenuation on the order of 15 dB.

  • 244. Samuels, Timothy
    et al.
    Sommerfeldt, Scott D.
    Incorporation of loudness measures in evaluation of the perceived effectiveness of active noise control1999Conference paper (Refereed)
  • 245. Sjösten, Per
    et al.
    Johansson, Sven
    Claesson, Ingvar
    Nordebo, Sven
    Considerations on Large Applications of Active Noise Control, Part I: Theory2003In: Acta Acoustica united with Acustica, ISSN 1610-1928, E-ISSN 1861-9959, Vol. 89, no 5, p. 822-833Article in journal (Refereed)
    Abstract [en]

    The application of active noise or vibration control to a real situation is usually a great challenge. The step from computer simulations, or even lab studies, to the actual implementation is often much larger than first expected. This is especially true for multiple-error, multiple-output control, in which careful planning and a very great deal of preparatory work is crucial to the success of the project. The present paper is the first in a series of two, that treat the process of preparing and evaluating an active noise control system. Part I gives a general discussion on proposed methods from a theoretical standpoint. Part II describes the application of these methods in practical measurements in an aircraft application. The emphasis is on multiple-error, multiple-output control but the general guidelines haves proven to be useful even in small applications. The discussion covers some acoustical aspects as well as the signal processing view. A method, based on simulated annealing using the metropolis sampler is suggested for searching the suboptimal positions for the control sources and sensors, including a thorough discussion on the preparation of input data for the optimisation process. Finally, a version of the complex lms algorithm, normalised individually for each actuator, is discussed.

  • 246. Sjösten, Per
    et al.
    Johansson, Sven
    Nordebo, Sven
    Claesson, Ingvar
    A Practical, Fast and Cost-efficient Algorithm Multiple Input, Multiple Output Active Noise Control Applications2001Conference paper (Refereed)
    Abstract [en]

    Active noise control has proven to be an efficient solution to low frequency noise problems in many different applications. A large part of these applications are concerned with harmonic noise control and typically require control systems with several inputs and outputs. As the systems grow, the demand for processor capacity increases rapidly, resulting in large and expensive hardware platforms. As multiple-input, multiple-output noise control is restricted to the control of periodic noise, a controller structure that is adapted to the signal type may significantly reduce the requirements on the hardware capacity. This paper discusses a complex, time-domain controller that is designed for the control of harmonic components. The structure of the controller is simple, easily implemented and can easily be extended to handle any number of noise references and any number of harmonics. The convergence properties of a multiple-input, multiple-output control system depends largely on the acoustic coupling between the active sources and the control sensors. To get accurate and stable control it is necessary to use normalization, i.e. a weighting function that optimizes the controller for each control source. With the presented controller structure, the use of normalization is straightforward and a number of different approaches for normalization is discussed as well as examples from practical inplementations.

  • 247. Sjösten, Per
    et al.
    Johansson, Sven
    Persson, Per
    Claesson, Ingvar
    Considerations on Large Applications of Active Noise Control, Part II: Experimental Results2003In: Acta Acoustica united with Acustica, ISSN 1610-1928, E-ISSN 1861-9959, Vol. 89, no 5, p. 834-843Article in journal (Refereed)
    Abstract [en]

    This paper treats the practical aspects of the prediction, implementation and verification of an active noise control system. The system was implemented in a mock-up of a Saab 340 propeller aircraft. A search algorithm, based on simulated annealing using the metropolis sampler was used to determine the positions for the control sources and sensors. The sound field was generated by a specially designed noise simulation system, using 12 individually controlled loudspeakers and a DSP--based signal generator. A version of the individually normalized complex lms algorithm was implemented for the control of the sound field. The prediction and verification of the active control system, was made in 20 evaluation positions, distributed at ear level above the seats. This is the second paper in a series of two, concerning the preparation, selection and verification of an active noise control system. Part I contains a theoretical treatment with some general guidelines for the implementation. Paper II is focused on the practical aspects of the implementation and verification.

  • 248. Svensson, Anders
    CAC When The Future Is Known1999Conference paper (Refereed)
  • 249. Svensson, Anders
    Call Admission Control Using Future Information1999Conference paper (Refereed)
  • 250.
    Svensson, Christine
    et al.
    Blekinge Institute of Technology, Department of Telecommunications and Signal Processing.
    Strandberg, Susanne
    Blekinge Institute of Technology, Department of Telecommunications and Signal Processing.
    Reporting Management för den interna rapporterings processen med hjälp av verktyget Tivoli Decision Support: TDS2001Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [sv]

    Rapporten inleds med en beskrivning av WM-datas Network Management struktur och Reporting Management behov. Därefter följer en beskrivning av de två analys tekniker Datamining och On Line Analytical Processing (OLAP) vilka är de mest använda databasbaserade tekniker. Verktyget Tivoli Decision Support (TDS) är ett stödssystem som ska underlätta för beslutsfattare inom organisationen. TDS baseras på OLAP ? tekniken och rapporten visar avslutningsvis de möjligheter som verktyget ger avseende WM-datas Reporting Management.

23456 201 - 250 of 279
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • 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