[final] Sähkötekniikan korkeakoulu / ELEC

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    Overmodulation and six-step mode for observer-based V/Hz control
    (2023-02-03) Iaderosa, Angelica; Tiitinen, Lauri; Sähkötekniikan korkeakoulu; Hinkkanen, Marko
    This thesis deals with the control of electrical machines in the overmodulation range. The goal is to have a stable control system able to exploit the full potential voltage of the inverter. After a brief explanation of the system model, the overmodulation algorithm is described. This method allows to have a smooth transition between the linear operation to the extreme operating condition in which the maximum voltage is produced. A synchronized PWM approach is adopted in order to reduce the harmonic spectrum throughout the whole operation. A scalar control based on a flux observer is considered thanks to its stability and its compatibility with the maximum voltage operation. Results show the feasibility of the overall system, six-step mode is able to increase the reachable speed while lowering the currents.
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    User Position-Based Loudspeaker Correction
    (2021-12-13) Lindfors, Joel; Liski, Juho; Sähkötekniikan korkeakoulu; Välimäki, Vesa
    In this thesis, a novel loudspeaker correction system is presented and studied.This correction system uses the location of the user to determine the calibrationparameters. Conventional loudspeaker correction uses a static equalizer to correctfor the coloration of the loudspeaker system at all times. However, the response ofthe loudspeaker changes dynamically with the location of the user. By correctingfor the loudspeaker’s response at multiple locations and changing the calibration inreal-time based on the user’s location, we expect a less colored frequency responsecompared to no applied calibration or conventional calibration methods. Thedeveloped method,User Position-Based LoudspeakerCorrection (UC), producesa flatter frequency response than that of no applied calibration: in one of themeasurement conditions the averages of the ranges of the frequency response (thedifference between the largest and the smallest decibel value) went from 10.3 dBin the non-corrected setting to 4.7 dB in the UC setting. Further, it is shownto outperform a conventional method of correcting for the frequency responseof each point in space by using calibration derived from measurements from apredetermined listening position. The average of the ranges with the conventionalmethod of calibration in the aforementioned listening condition was 6.8 dB. Finally,by interpolating the EQ gains for the calibration from a set of measurements for thesuggested correction method, the system’s resolution could be increased with theresulting calibration still outperforming the conventional correction method. Theaverages of the ranges for the interpolation methods in the aforementioned listeningcondition were around 6.1 dB varying approximately 0.1 dB with the method.
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    Network coding coefficients for compute-and-forward
    (2014) Zacharda, Marek; Pääkkönen, Joonas; ; Sähkötekniikan ja automaation laitos; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Farkas, Peter
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    Game theory applied to networking
    (2013) Casas Bonet, Marc; Costa-Requena, Jose; Tietoliikenne- ja tietoverkkotekniikan laitos; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Kantola, Raimo
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    Effect of advanced receivers on performance of cellular systems
    (2012) Minguez Garcia, David; Del Carpio Vega, Luis Felipe; Tietoliikenne- ja tietoverkkotekniikan laitos; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Tirkkonen, Olav
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    Carbon nanotubes and silver nanowires at millimeter wave frequencies
    (2012) Nefedova, Irina; Lioubtchenko, Dmitri; Radiotieteen ja -tekniikan laitos; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Räisänen, Antti
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    A non-intrusive appliance load monitoring system for identifying kitchen activities
    (2011) Valero Pérez, Maria; Harmo, Panu; Automaatio- ja systeemitekniikan laitos; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Montoro Manrique, Germán
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    Antenna array receiver switching synchronization for indoor positioning systems using WLAN technology
    (2011) Kis, Levente Robert; Signaalinkäsittelyn ja akustiikan laitos; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Richter, Andreas
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    MEMS thin film adhesion testing
    (2011) Baby, Anu; Grigoras, Kestutis; Mikro- ja nanotekniikan laitos; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Franssila, Sami
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    Development of multi-link geometry-based MIMO channel model
    (2010) Palacios Morales, Alvaro; Poutanen, Juho; Radiotieteen ja -tekniikan laitos; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Vainikainen, Pertti
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    Modelling the user effect of mobile terminal antennas based on equivalent circuit - focus on frequency shifting
    (2010) Martinez Navarrete, Laura; Holopainen, Jari; Radiotieteen ja -tekniikan laitos; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Laitinen, Tommi
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    Limited feedback for multiuser MIMO in LTE
    (2010) Del Val Conejos, Maria; Koivisto, Tommi; Elektroniikan, tietoliikenteen ja automaation tiedekunta; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Wichman, Risto
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    Spatial Inference in Large-Scale Sensor Networks using Multiple Hypothesis Testing and Bayesian Clustering
    (2019-05-06) Gölz, Martin; Koivunen, Visa; Muma, Michael; Sähkötekniikan korkeakoulu; Koivunen, Visa
    In this thesis, we address the problem of statistical inference in large-scale sensor networks observing spatially varying fields. First, we revisit traditional single-sensor hypothesis testing. We then present a multiple hypothesis framework to model spatial fields occurring in a multitude of practical signal processing applications. Observing and monitoring phenomena that occur within a spatial field is essential to a variety of applications. This includes tasks, such as, detecting occupied radio spectrum in shared spectrum environments, identifying regions of poor air quality in environmental monitoring, smart buildings and different Internet of Things (IoT) applications. Many of these practical problems can be modeled using a multiple hypothesis testing framework, with the goal of identifying homogeneous spatial regions within which a defined null hypothesis (e.g. pollution remaining at tolerable level, radio spectrum being unoccupied) is in place, and regions where alternative hypotheses are true. These regions can be formed assessing observations made by multiple sensors placed at distinct locations. To be scalable for largescale sensor networks, we suggest to compute local test statistics, such as, p-values at each individual sensor to avoid communication overhead due to a large number of sensors exchanging their raw measurement data. Individual test statistics are fed to a Fusion Center (FC), which performs the inference. At the FC, statistical inference is performed with a propose a method referred to as “Spatial Inference based on Clustering of p-values (SPACE-COP)” that uses multiple hypothesis testing and Bayesian clustering to detect occurring phenomena of interest within the spatial field. The method identifies homogeneous regions in a field based on similarity in decision statistics and locations of the sensors. The number of clusters, each of which is associated to a hypothesis, is determined by a newly derived Bayesian cluster enumeration criterion that is based on the statistical model that has been derived in this project. An EM-algorithm is developed to compute the probabilities that associate sensors with clusters. We present two different decision criteria, for maximum performance (SPACE-COP) and control of false discoveries (FDR SPACE-COP). The performance of the proposed methods is studied in a series of simulation examples and compared to competitors from the literature. Simulation results demonstrate the validity of proposed SPACE-COP methods also for cases in which the assumption on underlying spatial shape of alternative areas was clearly violated and true alternative areas followed arbitrary and even non-convex shapes. In summary, the derived algorithms are applicable to large-scale sensor networks to perform statistical inference and identify homogeneous regions in an observed phenomenon or field where the null hypothesis does not hold.
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    Adaptive loudness compensation in audio reproduction
    (2019-05-06) Fierro, Leonardo; Rämö, Jussi; Sähkötekniikan korkeakoulu; Välimäki, Vesa
    This work involves the study of the psychoacoustic phenomenon of nonlinear and frequency dependent loudness perception, its modeling, and the use of digital filters to introduce an adaptive compensation based on the reproduction level. Music and sound are mixed and mastered at a particular loudness level, which is usually louder than the level they are commonly played at. This implies a change in the perceived spectral balance of the audio source, which is largest in the bass and sub-bass ranges. As the volume setting in music reproduction is decreased, a loudness compensation filter can be designed to introduce an appropriate boost, so that the low frequencies are still heard well and the perceived spectral balance is preserved. This thesis describes a loudness compensation function derived from the standard equal-loudness level contours and its implementation via a digital first-order shelving filter, and it documents a formal listening test, designed and conducted to validate the accuracy of such a method. The research work was carried out between October 2018 and January 2019, during a visiting period at the Aalto University, Espoo, Finland.
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    Analysis of Nonidealities in Undersampling SAR ADCs
    (2018-08-20) Mattersdorfer, Clemens; Unnikrishnan, Vishnu; Sähkötekniikan korkeakoulu; Ryynänen, Jussi
    With the foreseeable adaptation of 5 G networks and its increasing use, blockers are becoming more common on their frequency bands. This gives rise to the need of wideband blocker-detection circuits for frequencies up to 6 GHz. The use of under- sampling SAR ADCs to detect blockers has already been demonstrated [1], however the performance showed to be lower than expected. The objective of this work is to investigate nonidealities appearing in SAR ADCs, when used as under-sampling converter. Therefore, a behavioral model of a SAR ADC has been built in Verilog-A, and an accompanying toolchain in Matlab has been devel- oped to assess the impact of system parameter variations on the dynamic performance figures (SNR, SNDR,...). The utilization of a behavioral model also allows an isolated view on otherwise interdependent phenomena, besides reducing the simulation time. System simulations show the effect of various system parameter variations on the converter performance. The conclusions drawn from behavioral simulations have been verified by inserting 65 nm technology transistors into the behavioral model. The sampling error appearing at slow switch transition times has also been investigated. It has been concluded, that the SAR ADC performance is primarily limited by the track-and-hold circuit, as the finite transition time from track- to hold-state causes the fast changing input signal to be averaged nonlinearly, instead of being sampled almost ideally.
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    Torque control for a flux-switching permanent-magnet motor based on FEM data
    (2018-08-20) Donazzolo, Riccardo; Hinkkanen, Marko; Sähkötekniikan korkeakoulu; Hinkkanen, Marko
    Flux-switching permanent-magnet (FSPM) motors development became important to the manufacturing companies due to their high torque density and robustness. Moreover the control methods for electric motors are in continuous evolution in order to minimize the losses caused by the drives and to optimize the computational costs. In this final project a 2.2-kW FSPM machine is considered. The aim of this project is to estimate the parameters from FEM data and to use them to parametrize the motor and the control system. All these data are first computed with a FEM software. Then a simplified parameterization that neglects the cross-coupling and saturation is used for the control system. Particularly, the collected data are also needed in order to build the look-up tables for the reference calculation, essential for having an efficient control design with a low computational cost. In order to obtain maximum torque taking into account the current and voltage limits, the maximum torque per ampere (MTPA), maximum torque per volt (MTPV) and field weakening (FW) strategies are employed. The final simulation scheme is a control system with a simple parameterization and a plant model which includes saturation and cross-coupling. Hence the error caused by the neglected saturation and the performance of the control system are analyzed.
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    Measurements on a flux intensifying interior permanent magnet motor for an optimal torque control
    (2018-06-18) Comin, Andrea; Hinkkanen, Marko; Sähkötekniikan korkeakoulu; Hinkkanen, Marko
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    Second-order optical nonlinearity in Gallium(II)–Selenide
    (2018-03-26) Grüßing, Soenke; Wang, Yadong; Sähkötekniikan korkeakoulu; Sun, Zhipei
    Nonlinear optics of two-dimensional (2D) layered materials is currently at the centre of significant research effort. This final project is to investigate several aspects of second-order optical nonlinearity phenomena in atomically-thin Gallium(II)–Selenide (GaSe). The work includes the preparation of thin-layered GaSe samples via mechanical exfoliation and the subsequent investigation of their nonlinear optical properties via multi-photon microscopy (MPM) and a pump-probe setup. The scientific objective of the work is to understand the frequency-dependent nonlinear optical responses in atomically thin GaSe devices. The power dependent second harmonic generation (SHG) and sum-frequency (SFG) are measured. Four-wave mixing (FWM) was observed for the first time in GaSe. These results pave the way to fully understanding various nonlinear optical responses in GaSe.
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    Real-time control system for a permanent magnet synchronous machine
    (2018-02-12) Squarcio, Daniele; Musolino, Francesco; Sähkötekniikan korkeakoulu; Belahcen, Anouar
    In the last decades there has been an always increasing demand for reducing the dependence on fossil fuel. The transportation sector is very crucial since it produces roughly more than one third of the overall pollution. The biggest change that is happening in this sector is the increasing number of electric and hybrid vehicles that circulate on the streets. Considering all these aspects is easy to forecast that electric motors will play an even more important role in the future. In this context, a key role is played by the electronic systems, also known as controllers, devoted to convert the electrical energy from the fixed form available into the specific form that is required by the motors. Nowadays, to achieve gather flexibility more and more systems are replacing analog control with digital control. Anyway, the problem with digital control is the high level of inefficiency in the computational effort, linked to the fact they are very demanding considering the amount of data to be processed and stored. The computational efficiency of the control algorithm is very important because directly affects the efficiency of the whole system. In this context of digital control constantly evolving to achieve the best compromise between flexibility and efficiency is inserted this thesis work. The goal is to develop a new control strategy for the IPM (Internal Permanent Magnets) motor. To achieve the goal the starting point was the implementation of the model for the controller and the motor in Matlab-Simulink environment. The simulation session investigates if the results obtained by the Matlab-Simulink model are in agreement with the theoretically estimated values. In the next phase, the model developed was adapted to work properly in the dSPACE environment, used to control the motor in real-time. Are reported also the tests in the laboratory to measure all the fundamental variables as current, speed, flux, directly on the motor and compare these measures with the results obtained in the simulation step. The results confirm the improvements expected from this new technique. Therefore, its use allows to improve the overall efficiency, it guarantees also an increase in the speed of the control and reduces the number of variables that have to be stored. The achievement of these goals leads also to a reduction of the useless rotor movements linked to delays along the feedback path. As a result, losses are minimized and output energy is maximized.
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    Implementation of an automated eye-in-hand scanning system using Best-Path planning
    (2017-10-23) Rebull I Mestres, Jordi; Racca, Mattia; Sähkötekniikan korkeakoulu; Kyrki, Ville