Before a mobile can commence services it needs to have access to a base station. The access method is often referred to as random access (RA). One way to measure the performance of the RA procedure is the access delay (AD) of the mobiles, where AD is the time from which a mobile wants to start a RA attempt until it has received access. There are different approaches to optimize the RA procedure. Manual optimization is possible but costly. Automated optimization is preferable because of the lower costs and the possibility to change configuration fast in the base station when the operational conditions change. This thesis focuses on automated optimization of the RA procedure with regard to AD. A controllability and observability study of AD is first presented in this thesis. The controllability study shows that AD can be controlled by a number of RA parameters, whereas the observability study show that AD cannot always be correctly observed. The next part of this thesis presents a controller synthesis, where three different controllers are presented to control a specified percentile of AD. It is shown, through experiments, that the controllers derived can be used to optimize the RA procedure with regard to AD.

Detta projekt är ett examensarbete för kandidatexamen som är obligatorisk för alla studenter. För att ta ut examen måste jag lämna en skriftlig rapport om vad jag har gjort. Redovisa simuleringar och mätningar på olika kretsar.  I mitt fall var jag intresserad på att studera hur varvtalet på en likströmsmotor kan regleras med hjälp av olika metoder.  Detta är mycket utmanande för mig eftersom jag inte har sett så många lösningar på detta problem.  Jag kommer att använda kunskap, teknik och komponenter från Kraftelektronik för att utföra mitt arbete.  Det blir mycket intressant att med dagens utveckling av tekniken se hur olika metoder kan användas för att undersöka hur kraftelektronik kan användas i kontroll av varvtal, frekvens och rotationsriktning av elektriska maskiner.

<p>Active Radio Frequency Identification (Active RFID) is a wireless automated technology used to identify, track, process and share information about an object or from the environment. As microcontrollers and radio frequency transponders are smaller in size, more power efficient, and less expensive, this technology is growing and starting to expand significantly through all the industries. The main purpose of with this project was to reduce the ower consumption of the active tags. This master thesis presents a functional TDMA based protocol which was designed and developed for a specific tracking system application.</p>

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<p>This report describes the scientific work of designing and manufacturing an intelligent controller module prototype for automobile trailer connections. The functions of the module are both to drive the lamps and detect failures. The module also contains functions to handle other functions of the trailer. To learn about controller modules the group does extensive feasibility study.</p><p>The group receives three already existing modules, the functions of the three modules are studied and tested in the lab, this is done too get a overview of the construction. The method used I called reversed engineering, a way of constructing by analyzing constructions already done.</p><p>When the modules are analyzed, the functions of the prototype are tested and designed without copying the analyzed modules. The components that the analyzed modules are containing are also studied.</p><p>The requirement specification contains the functions of the prototype to bee constructed.</p><p>The work results in a working prototype of controller module that is planed too bee used as a base in the construction work of future modules.</p>

<p>MobileReader är en mobil RFID (Radio Frequency Identification) applikation. Syftet med denna applikation är att skapa en RFID-läsare som skall gå att bära med sig ute på fältet. I första hand kommer läsaren att kunna läsa passiva RFID-taggar på Lågfrekvens-bandet (LF) samt att vara anpassad för nyare mobiltelefoner av tillverkaren Sony Ericsson. Detta examensarbete resulterade i ett program avsett för en Atmel ATmega16 mikroprocessor. Mikroprocessorn tar emot data från en befintlig LF-läsare via ett protokoll vid namn Wiegand 44. Den inlästa datan paketeras in i ett PDU-paket, Protocol Data Unit, vilket är det protokoll som mobiltelefoner använder för att skicka SMS mellan MS, Mobile System, och BS, Base System.</p> / <p>MobileReader is a mobile RFID (Radio Frequency Identification) application. The purpose of this application is to create a reader, that can be carried out in the field. This project will concentrate on reading passive RFID-tags on the Lowfrequency band (LF) and will be customized for a newer mobile phone manufactured by Sony Ericsson. This has resulted in a program written for the Atmel ATmega16 microcontroller. The microcontroller receives data from an already existing LF-reader using the Wiegand 44 protocol. The data will be converted into a PDU-packet, Protocol Data Unit, which is the protocol used by mobile phones to send SMS between MS, Mobile System, and BS, Base System.</p>

<p>Degradation of XLPE insulated power cables by water-trees is a primary cause of failure of these cables. The detection of water-trees and information about the severity of the degradation can be obtained with off-line measurement using dielectric spectroscopy. In many situations only a limited part of the cable may be degraded by the water-trees. In such a situation a method for localization of this water-treed section would be desirable. On-voltage Time Domain Reflectometry (TDR) diagnostics proved to be capable of localizing the water-tree degraded sections of the cable. The possibility of using on-voltage TDR as a diagnostic method opens up as a further step for the development of an on-line TDR method where the diagnostics are performed using pre-mounted sensors on the operating power cable. The benefits with such a method are: ability to perform diagnostics without disconnecting the cable from a power grid; the diagnostics performed during a longer period of time could give an extra information; no need for an external high-voltage supply unit.</p><p>In this thesis the sensors for the on-line TDR are investigated in terms of sensitivity and bandwidth. High frequency models were built and the simulation results in frequency and time domains were verified by measurements. Results of the on-voltage TDR measurements on the degraded XLPE cables in laboratory as well as on-site are presented.</p><p>The on-line TDR system and the results of a four-days on-line measurement sequence are presented. Variations due to load cycling of the cable were observed, where an increase in the cable temperature cause an increase of the pulse propagation velocity in the cable.</p><p>A method has been developed for high frequency characterization of power cables with twisted screen wires, where the measurements are performed using inductive strip sensors. This technique allows the high frequency parameters of the selected section of the cable to be extracted. The high frequency parameters are extracted from frequency domain measurements of S-parameters as well as from TDR measurements.</p> / QC 20100709

<p>The wind power industry has experienced a large growth the past years. The growth mainly focus on a growing market, better economical conditions for wind power because of political decisions and the development of large wind turbines and offshore farms. A goal is to increase reliability for turbines. The topic is even more important for offshore farms where service is difficult and expensive.</p><p>The answer for the wind power industry, for better maintenance management and increased reliability, could be Condition Monitoring Systems (CMS). Such systems are commonly used in other industries. They continuously monitor the performance of the wind turbine parts e.g. generator, gearbox and transformer, and help determine the best time for a specific maintenance work. How these systems could support the wind power user is investigated in this report.</p><p>The further step could be to implement CMS as a part of Reliability Centered Maintenance (RCM).RCM is a structured approach that focus on reliability aspects when determining maintenance plans, that is to find a balance between preventive- and corrective maintenance. Preventive maintenance is maintenance carried out before failures occur and corrective maintenance is maintenance carried out after failures occur.</p><p>Condition Monitoring can consist of e.g. vibration analysis and oil analysis. In these two different analyses there are several methods that can be used. The components that are of interest of condition monitoring are the gearbox, generator and the main shaft. The component of most interest, and that it has been shown is a critical component due to its impact on system availability, is the gearbox.</p><p>Life Cycle Cost (LCC) analyses have been made to calculate if it is profitable to implement CMS. The total cost, LCC including additional costs for implementing CMS, is compared for different alternative maintenance strategies. For a single turbine onshore versus an average turbine offshore in three strategies, and for a farm offshore where maintenance is planned using CMS in three strategies. The LCC without costs for CMS is called the basic case.</p><p>The first three strategies studied for the separate turbine onshore gave the following results when a CMS cost is added to the basic case; to compensate for the additional cost the preventive maintenance has to be decreased by 23 %. To compensate for the additional cost the preventive and corrective maintenance together have to be decreased by 3,5 %. The same results for the farm offshore, where an average turbine was observed, were 4,5 % and 2,5 % respectively. Decreased corrective maintenance is needed to motivate CMS, at least for the turbine onshore.</p><p>The following three strategies studied for the farm offshore gave the following results: a change from corrective maintenance to preventive maintenance with 47 % would be enough to make CMS profitable. The availability would not have to be increased with more than 0,43 % to get a reduction in cost for production loss that would cover the cost for CMS.</p>

<p>Stator insulation is a critical to the reliability of electrical generators and motors. It is common industrial practice to use electrical measurement of partial discharges (PD) and some form of current-voltage measurement as part of the condition assessment of stator insulation at maintenance times. Extension of these methods by the recently investigated methods of high-voltage dielectric spectroscopy (HV-DS) and variable frequency phase- resolved partial discharge analysis (VF-PRPDA) may offer r usefully increased information about the condition of a stators insulation while requiring less power from the test voltage source than with conventional power-frequency measurements.</p><p>HV-DS and VF-PRPDA have independent variables of the amplitude and frequency of a sinusoidal voltage applied to the insulation system. The dependent variables are the smooth currents of HV-DS and the discharge pulse charges of VF-PRPDA; these may be analysed in many ways, typically as complex capacitance, the harmonic spectrum of currents when there is PD activity or other non-linearities in the insulation system, and various measures of PD pulse distribution.</p><p>The methods provide complementary information and have a common need of a variable frequency high voltage driving source. This makes the simultaneous use of these methods a matter of interest, as further information can be gained without extra time and with a total equipment size and cost smaller than that of both separate systems. </p><p>In this thesis, results are presented from several directions of work relevant to the application of the low frequency diagnostic methods, HV-DS and VF-PRPDA, to machine insulation.</p><p>The contribution to measured frequency domain dielectric response from the current into the non-linear stress grading of stator end-windings has been studied from physical and numerical models. As well as the effecects on the dielectric response (complex capacitance), the harmonic spectrum of the current into the grading, and the distribution and waveform of the potential along the grading is shown from the numerical models. The frequency and amplitude dependent response of the stress-grading is of importance due to its significacant contribution to the measured dielectric response of a whole stator and to the harmonic currents due to other non-linear phenomena such as partial discharge currents.</p><p>Short dielectric response measurements have been made on a complete hydro-generator before and after a period of maintenance, giving a better idea of the practical limitations that time constraints and a large test-object put on possible amplitudes and frequencies for driving the test object.</p><p>Two new epoxy-mica stator coils have been studied with both DS and VF-PRPDA before and after accelerated thermal aging, as a preliminary step for seeing what changes can be detected electrically and for studying how the PD and DS methods differer in their measurement of PD.</p>

<p>The object of this thesis is to develop a cost effective direct-driven wind generator suited for offshore wind turbines. As the generator price is a complicated function dependent on many parameters, the emphasis is mainly put on reduction of the weight of active materials, such as copper, laminated steel, permanent magnets, and electrical insulation. The higher specific torque and power density of a transverse flux permanent magnet (TFPM) machine in comparison to conventional radial-flux machines make it a promising solution for direct-driven wind turbine generators. The novel TFPM generator investigated in this work due to its possibly more compact construction would allow a better utilization of the available nacelle space. The analytical model, including evaluation of the synchronous inductance, is developed and applied in parametric study of a 5 MW wind turbine generator. The influence of the design variables with respect to the analyzed characteristics is investigated. A number of machines that have approximately the same performances are found. These machines are compared and the optimal ranges for the main parameters are suggested. One possible design topology is presented in more details with dimensions and main characteristics. This generator is compared with radial-flux generators with surface-mounted and tangentially-polarized magnets. It is found that the analyzed TFPM generator would favor a smaller outer diameter, reduced total active weight, and reduced weight of the magnet material. The TFPM would however require a longer axial length. TFPM generators with a broader range of output power have also been investigated. Generators rated 3, 5, 7, 10, and 12 MW are analyzed and their characteristics with respect to the output power are compared. The novel transverse flux topology has been found to be promising for low-speed hightorque applications, such as direct-driven wind turbines in the multi-megawatt range.</p>