<p>Under ventilprov vid kärnkraftverket Oskarshamnsverket 3 har oscillationsfenomen detekterats vid vissa driftlägen, främst i samband med stängning av någon av högtrycksreglerventilerna som reglerar ångflödet ut från reaktortanken. Syftet med detta examensarbete är att förklara uppkomsten av dessa oscillationer. </p><p>För att kunna analysera problemet har en modell över reaktor och tryckregulator tagits fram. Detta har gjorts dels med hjälp av befintlig systemdokumentation och dels genom att skatta modeller av olika delar av systemet. Det har visat sig att det går att få fram en modell som skattar reaktortrycket ganska väl med ångflöde och neutronflöde som insignaler. En tidigare beskrivning av ångflöde för olika ventilöppningsgrader har visat sig vara felaktig och därför har en ny ångflödesfunktion tagits fram. Vid simuleringar med den modell som har byggts upp över tryckreglersystemet har oscillationsfenomenet kunnat påvisas. </p><p>Tryckregulatorn syftar till att hålla reaktortrycket konstant genom att variera ångflödet ut från reaktorn. Detta görs genom att variera ventilernas öppningsgrad. Förhållandet mellan öppningsgrad och ångflöde är dock inte linjärt. Meningen är att detta ska kompenseras i reglerservomotorn som ska reglera ventilerna så att ångflödet motsvarar det beordrade ångflödet från regulatorn. Denna linjärisering bygger dock på det felaktiga sambandet mellan ventilöppningsgrad och ångflöde. Vid stängning av en högtrycksreglerventil kommer signalen från tryckregulatorn att förstärkas jämfört med fallet med samtliga ventiler öppna, något som med stor sannolikhet leder till uppkomsten av självsvängningar. </p><p>I rapporten ges två förslag till lösningar på självsvängningsproblemet. Om man kan få fram en bra bild av det olinjära sambandet mellan regulatorns signal och ångflödet borde detta kunna kompenseras i regulatorn så att man åter får ett linjärt samband. Ett annat alternativ är att byta ut de kurvskivor som nu används för linjärisering i reglerservomotorerna så att man får ett linjärt samband mellan regulatorns beordrade ångflöde och det verkliga ångflödet.</p>

<p>In this final thesis a rough description of aluminium extrusion is made, the importance of temperature of both the raw material and the extruded profile for a good profile quality. The difficulty in controlling these temperatures are discussed and attempts to increase the control are described. The attempts are basically made by controlling the furnace that is heating the raw material. This is done in a manner that the raw material reaches its final temperature shortly before it is extruded. An IR-camera at the press can be used for profile temperature measurements. The profile temperature is in turn used to decide the raw material temperature. Finally some proposals are given that can lead to a more controlled temperature at raw material and profile.</p>

<p>Evaporation is a part of the chemical recovery department at wood pulping mills. The purpose of evaporation is to remove water from the black liquor, which makes the liquor combustible. The process is very energy demanding, and having a well-functioning model of the system is of greatest interest. The model can then be used to study energy consumption and to test different control strategies. </p><p>Two models have been developed during the master thesis. The main model is a complete model of the evaporation at Södra Cell Mönsterås and has been constructed using the simulation program Extend. The Extend model is a block based, static model, which describes energy and mass flows of liquor, steam and condensate. </p><p>The other model consists of a dynamic, parametric model created using the System Identification Toolbox in MATLAB. However, the dynamic model only considers some parts of the evaporation. </p><p>Finally, some suggestions of further development and usage of the models are given.</p>

<p>Examensarbetet behandlar en modellering av hyttgasnätet vid SSAB Oxelösund AB. Det objektorienterade modelleringsspråket Modelica används. Modellen valideras statiskt och dynamiskt för olika driftsfall med gott resultat. </p><p>Hyttgasen används delvis för generering av elektricitet i kraftverket. Simuleringar av modellen visar att hyttgasnätets konstruktion begränsar inflödet av hyttgas till kraftverket. Modellen används för att studera förändringar av hyttgasnätet som kan öka inflödet till kraftverket. I examensarbetet föreslås byte av de befintliga brännarna i kraftverket, införande av två extra brännare eller införande av en tryckstegringsfläkt. Samtliga förändringar möjliggör en ökad elproduktion i kraftverket, detta leder till ökad vinst för SSAB. </p><p>Olika driftsstörningar i hyttgasnätet simuleras för att ge förslag på åtgärder som kan minska störningen. Ett snabbstopp av kraftverket ger en tryckstegring i nätet. Störningen kan minskas genom att facklorna regleras av trycket i gasnätet, tryckregleringen kombineras med dagens reglering mot gasklockans nivå. När ett snabbstopp i blåsmaskinen studeras kan en modifiering av regulatorn till reglerspjället göras. Förändringen medför att gasklockans nivå stabiliseras. </p><p>För att minska förlusterna av gas bör facklornas reglering ändras. Facklornas reglering kan förbättras genom att fördelningen av den hyttgas som ska förbrännas i facklorna ändras. Om förbättringen införs i hyttgasnätet minskas förlusterna av hyttgas och elproduktionen i kraftverket kan ökas.</p>

<p>A current trend in the information society is that traditionally fixed computing resources are made available to mobile users. Most of the existing techniques for communication have been developed for stationary computing, and they must be adapted to the different connection properties of the mobile environment. One of the emerging mobile computing environments is the Universal Mobile Telecommunication System, UMTS. This system places demands on the quality of service that is provided to data flows, which requires resource management in the connection network. The most scarce resources in this system is the radio resources. The easiest way to conduct research in new and adapted techniques for communication is to perform simulations. Management of resources places restrictions on connections, and to get reliable results during simulations it must be included in the simulated environment. The thesis discusses and builds a basis for development of UMTS radio resource management in the network simulator ns-2. A limited version of UMTS radio resource management is added to ns-2 and evaluated.</p>

<p>The problem with motorized wheelchairs is that they are large, clumsy and difficult to control. This is especially true if the driver has severely reduced capabilities. What we want is a wheelchair that can take instructionsfrom the driver and then based on its understanding of the environment, construct a plan that will take the user to the intended destination. The user should be able to sit in a room, tell the wheelchair that he wants to be in another room and the wheelchair should take him there as quickly and smoothly as possible. </p><p>The planner presented in this thesis uses a randomized bi-directional tree search. It builds two trees, one from the start state and one from the goal state by randomly sampling the control space of the robot. Each node is a state and each edge is a control input to the robot.</p><p>In order to decrease the execution time and improve path quality, the planner uses several heuristics to guide the planner. The heuristics are based on Rapidly-exploring Random Trees, Probabilistic Road-maps and the gradient method. </p><p>For a normal household situation, this planner can construct a decent plan in mere seconds on relatively slow hardware. Most times it finishes in a fraction of a second. </p><p>This means that the planner has the ability to run in real-time. As a consequence, the planner can handle a dynamic environment, inaccurate sensor readings and an inaccurate physical robot model.</p>

<p>The engine of JAS 39 Gripen, RM12, has recently been equipped with a new flameholder and a new engine inlet. This change has caused an increased noise level from the engine when the afterburner is in use. The noise level reaches its peak when the afterburner is partially used. The problem is thought to be unstable combustion in the regions around the flameholder. A solution to the problem has been proposed by Volvo Aero. The idea is to modify the software in the engine control unit (FADEC) that changes the airflows in the engine. This master thesis implements the proposed changes and analyzes the effects of this implementation. The analysis is done by simulations of a model of the engine that Volvo Aero has created and implemented in MatrixX/SystemBuild. Simulations showed that it is possible to achieve the desired result by the software changes. Further the simulations showed some problems with stability for the engine when controlled by the modified control unit. This was solved by implementing a filter in the FADEC software.</p>

<p>Conventional airborne laser scanner systems output the three-dimensional coordinates of the surface location hit by the laser pulse. Data storage capacity and processing speeds available today has made it possible to digitally sample and store the entire reflected waveform, instead of only extracting the coordinates. Research has shown that return waveforms can give even more detailed insights into the vertical structure of surface objects, surface slope, roughness and reflectivity than the conventional systems. One of the most important advantages with registering the waveforms is that it gives the user the possibility to himself define the way range is calculated in post-processing. </p><p>In this thesis different techniques have been tested to visualize a waveform data set in order to get a better understanding of the waveforms and how they can be used to improve methods for classification of ground objects.</p><p>A pulse detection algorithm, using the EM algorithm, has been implemented and tested. The algorithm output position and width of the echo pulses. One of the results of this thesis is that echo pulses reflected by vegetation tend to be wider than those reflected by for example a road. Another result is that up till five echo pulses can be detected compared to two echo pulses that the conventional system detects.</p>

The main part of this thesis focuses on optimal experiment design for system identification within the prediction error framework. A rather flexible framework for translating optimal experiment design into tractable convex programs is presented. The design variables are the spectral properties of the external excitations. The framework allows for any linear and finite-dimensional parametrization of the design spectrum or a partial expansion thereof. This includes both continuous and discrete spectra. Constraints on these spectra can be included in the design formulation, either in terms of power bounds or as frequency wise constraints. As quality constraints, general linear functions of the asymptotic covariance matrix of the estimated parameters can be included. Here, different types of frequency-by-frequency constraints on the frequency function estimate are expected to be an important contribution to the area of identification and control. For a certain class of linearly parameterized frequency functions it is possible to derive variance expressions that are exact for finite sample sizes. Based on these variance expressions it is shown that the optimization over the square of the Discrete Fourier Transform (DFT) coefficients of the input leads to convex optimization problems. The optimal input design are compared to the use of standard identification input signals for two benchmark problems. The results show significant benefits of appropriate input designs. Knowledge of the location of non-minimum phase zeros is very useful when designing controllers. Both analytical and numerical results on input design for accurate identification of non-minimum phase zeros are presented. A method is presented for the computation of an upper bound on the maximum over the frequencies of a worst case quality measure, e.g. the worst case performance achieved by a controller in an ellipsoidal uncertainty region. This problem has until now been solved by using a frequency gridding and, here, this is avoided by using the Kalman-Yakubovich-Popov-lemma. The last chapter studies experiment design from the perspective of controller tuning based on experimental data. Iterative Feedback Tuning (IFT) is an algorithm that utilizes sensitivity information from closed-loop experiments for controller tuning. This method is experimentally costly when multivariable systems are considered. Several methods are proposed to reduce the experimental time by approximating the gradient of the cost function. One of these methods uses the same technique of shifting the order of operators as is used in IFT for scalar systems. This method is further analyzed and sufficient conditions for local convergence are derived.

TCP (Transmission Control Protocol) is a transport protocol designed for the wired Internet. In wireless networks packet losses occur more frequently due to the unreliability of the physical link. The main problem is that TCP treats all losses as congestion, which leads to a lower throughput. Ad hoc networks are multihop wireless networks of mobile nodes, where each node can allow other packets to pass through it. Topology changes often occur and may lead to packet losses and delays, which TCP misinterprets as congestion. We want to modify TCP to recognize the differences between link failure and congestion to improve the capacity. In our model we have built a connection in an ad hoc network where packet losses and partitions can be made. Simulation experiments show that we didn't get the problems we expected. This can be explained by low delays and because we buffered the packets during link failure. A simple modification of TCP was made and simulated, and showed that an improvement of performance is possible. More research should be done to make a modification of TCP that would further affect the throughput.