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Optimization and robustness of structural product familiesÖman, Michael January 2009 (has links)
<p>This thesis concerns structural optimization of product families and robustness. The overall objective is to find a method for performing structural optimization of product families subjected to multiple crash load cases and to ensure a robust behavior.</p><p>A product family is a family of products where every product variant, or family member, shares at least one component with at least one other product in the family. Structural optimization of such a family is complex and for expensive function evaluations, e.g. crash simulations, the computing time to solve the problem with traditional methods gets unrealistically long. Therefore, a new optimization algorithm for product families is presented, called the critical constraint method (CCM), that reduces the number of required evaluations by only considering the active constraints in the optimal solution.</p><p>Traditionally optimized structures have a tendency of being sensitive to small variations in the design or loading conditions. As these kind of variations are inevitable, it is important to account for this sensitivity in the design process to ensure the robustness of the optimized design.</p><p>The thesis is divided in two parts. The first part serves as a theoretical background to the second part, the two appended articles. This first part includes introductions to the concepts of product families, optimization, meta modeling and robust design.</p><p>The first appended paper presents a new optimization algorithm for product families subjected to multiple crash loads. The method is compared to traditional methods and tested on two smaller product family examples.</p><p>The second paper is an application of an existing sensitivity analysis method on a large industrial application example. A sensitivity analysis is performed on a Scania truck cab subjected to an impact load in order to identify the most influencing variables on the crash responses.</p>
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Fuel Optimal Powertrain Control for Heavy Trucks Utilizing Look AheadIvarsson, Maria January 2009 (has links)
<p>The road topography in highways affects the powertrain control of a heavy truck substantially since the engine power is low in relation to the vehicle weight. In large road gradients constant speed is not possible to keep, which would have been beneficial otherwise, and in some uphills shifting gears becomes inevitable. If information about the road ahead, i.e. look ahead information, is available, then the powertrain can be controlled in a more fuel efficient way. Trial runs are performed, where the velocity trajectory that minimizes energy consumption, is calculated and communicated in real time as set points to the conventional cruise control. This look ahead control gives significant fuel consumption reductions compared to a standard cruise control, while keeping to the same mean speed. The results are the inspiration to further studies in how powertrain control can benefit from look ahead information. An engine with a non-linear fuel map is studied to understand its impact on fuel optimal speed. It is shown that for a significant fuel map non-linearity, quantified by a threshold value, constant speed in small road gradients is no longer optimal. Further, an automated manual transmission (AMT) optimal gear control is studied. It is shown that the reduced propulsion of a typical AMT gear-shifting process must be considered when choosing when to shift gears. Thus, additional reductions of fuel consumption are obtained with a look ahead control based on knowledge of engine and transmission characteristics.</p>
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Styrsystem : För en forskningsutrustningKarlsson, Oskar January 2009 (has links)
<p>The division of Engineering Materials at Linköping University, department of Management and Engineering, conducted a research project concerning Fatigue life of thermal barrier coatings during 2009. During this project equipment to provoke these fatigue failure by rapidly heating and cooling test subjects in cycles, was ordered.</p><p>Design and manufacturing of the equipment was handled internally at LIU.</p><p>The equipment was built using a furnace that is lowered and raised over the table where the test subject is placed. To keep the temperature of the furnace a lid slides in place to close the downward facing opening of the furnace when it is in the raised position. On this door there is nozzle that is used to cooling of the test subject by air.</p><p>To make sure that the equipment can work independently you need an automation controller that can evaluate if movement can occur without danger of collisions. The control system also needs to monitor that all elements are performed according to plan.</p><p>This degree project is based on a modular system from OPTO 22 and includes the configuration of a PLC that will be supplied with logic and a user interface.</p><p>The degree project resulted in a graphic interface in which a user can set desired values for different parameters and get information about current values for them. Using the interface the user could also start and stop the running of cycles. An analog interface consisting of a start and stop button is also handled in the project.</p><p>Logic has been created and tested using simulations of incoming signals. During these tests it managed to transform the equipment from standby to starting position for running cycles, running cycles that can be adapted by the user and to put the equipment in standby position when the user want to power down the system. Apart from this there is also routines to monitor that movements is actually done according to plan and communicates with external systems capable of sending signals. A routine that both transform digital alarms and translate numerical values representing different choices to text messages in the graphic interface has been created.</p>
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Askdeponi i bergrum : Metoder för slurrytillverkning / Deposit of Ashes in Rock Shelters : Methods for Slurry ProductionJohansson, David January 2009 (has links)
<p>This thesis work has been carried out at the consultant company Pöyry Sweden AB in Norrköping, whom performs the task for E.ON heating Sweden AB, Händelöverket in Norrköping. The report shows methods to manufacture slurry consisting of fly ash and water. The slurry shall be pumped into several former oil storage rock shelters that E.ON has put into operation for the specific purpose. The ash mixture also develops hydrogen gas in contact with water.The work has aimed to produce different suggestions of methods and equipment that can be used for the objective. Mixing method and security issues were in centre while working with the suggestions. Parts which only indirectly are involved in the slurry manufacturing have been left out.Information has first and foremost been obtained from the Internet and company websites, but also later on through contact with salesmen and persons with knowledge in ash handling. Several references have been investigated. A close visual inspective and thought-provoking educational visit was also conducted.The results of the work are three well-tried main suggestions and one suggestion where a totally different mixing technique is used. Comparable industrial mixing activities are discussed in the beginning of the result chapter, along with some theory in three different mixing technologies. Examples of pumping equipment have also been put together.In the future a lot of work remains. An evaluation of this thesis report should be conducted before the choice of mixing method and equipment is done. Also coordination concerning all sorts of practical and technical details regarding construction work, purchasing and so on, belongs to the work that lies ahead.</p>
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Occupational Fraud : Auditors’ Perceptions of Red Flags and Internal ControlFagerberg, Jesper January 2008 (has links)
<p>The overall purpose of this thesis is to increase the understanding of auditors’perceptions of occupational fraud. The focus is limited to red flags andinternal control, i.e. to the indications or symptoms of occupational fraud andthe internal control systems which are implemented in order to detect andprevent such actions from being carried out.</p><p>The thesis is based on 33 interviews with auditors and experts. In order toincrease confidence, triangulation was applied which implied both aqualitative as well as a quantitative methodological approach. The collecteddata was in turn analysed through two models of analysis – an adjustedversion of the so called fraud triangle and the so called COSO-model. Theanalysis was carried out on the group of auditors as a whole (including subgroupsof auditors) as well as compared to a group of experts on fraud andoccupational fraud.</p><p>The results from the study indicate several aspects of interest regardingauditors’ perceptions of occupational fraud. First, the results indicate a tendencyamong auditors to emphasise “harder” aspects stronger than “softer”aspects. Seen from the fraud triangle, this was manifested by an emphasis onopportunity; when concerning internal control of control activities in theCOSO model, this was emphasised relatively stronger. Second, the resultsindicate a rather strong heterogeneity among auditors in their perceptions ofoccupational fraud. Third, all subparts of the applied models were seldomcovered on an individual basis. Fourth, the interconnection between harderand softer sides, both concerning red flags and internal control, were not verystrongly emphasised. The results were given additional strength from thecomparison with the group of experts.</p><p>The study also included a comparison among different subgroups of auditors.The subgroups were constructed based on accumulated working experience aswell as whether the respondents primarily audit larger or smaller companies.The results that were based on years of experience indicate a tendency amongolder auditors with more accumulated working experience to emphasise softeraspects relatively stronger, than auditors with less working experience. Thistendency was present for red flags as well as for internal control. More experienced auditors also demonstrated a tendency to emphasise a relativelylarger part of the two applied models of analysis. The division based on sizeof audited companies indicated similar tendencies as were found for bothmore and less experienced auditors. Hence, auditors who mainly audit largercompanies showed a tendency to emphasise softer aspects relatively strongercompared to auditors who mainly audit smaller companies.</p>
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Meeting increased logistical demands : Developing as a small- and medium-sized system supplierCarlsson, Inga-Lill January 2009 (has links)
<p>Many subcontractors choose to implement a strategy of “system supply” in order to meetincreasing global competition. They are then confronted with increased demands to take agreater overall responsibility in this role. It is important to investigate the implications of theseresponsibilities before investing in developing the organization, especially for a small- ormedium-sized subcontractor with limited resources. The customer’s view of different demandsdoes not necessarily correspond to how the supplier sees and chooses to interpret and meetthose demands. A supplier with several customers has to create reasonably uniform routines tomeet different demands, in order to cut costs. The customers chosen to serve as well asattitudes and priorities may influence the way different customer demands are met. Thepurpose of this study is to describe what the widened role of system supply might mean to asmall- or medium-sized subcontractor in terms of demands, capabilities and resources.</p><p>After going through previous theory about different supplier roles and their characteristics asmall exploratory survey comparing demands between a component supplier and a systemsupplier was carried out. “System supplier” is, in this thesis, defined as a supplier with anoverall responsibility for the functionality of a product or a system of assembled components,produced in several process steps, and the resulting liability for purchase of material andservices. The focus is on small- or medium-sized suppliers that provide production services andare developing towards system supplying capabilities. The survey, based on existing customeragreements and demands on a relatively small supplier that is developing towards a systemsupplying role, gives insight to how customers and suppliers look at these demands. The resultsclearly point out some improvement areas. These are divided into a few “system demands”(such as systematic purchase and logistics work, product development and projectmanagement, and increased responsibilities) and more “generic demands” (for example qualityand delivery-precision).</p><p>A small- or medium-sized subcontractor must acquire some logistics capabilities in order tocope with the system supplying role. In a multiple case study, a comparison of three companiesof different sizes with varying degrees of system supplying services is presented. With theresource-based view as a linchpin the interviews point out the importance of the management’sstrategic alignment to supply chain management and logistics, with special focus on centralsourcing and sourcing from low-cost regions. Other capabilities such as IT and communicationsystems, cost reduction capability, volume flexibility and breadth of product lines are alsoidentified. The interviews also served the purpose of identifying important resources groupedinto three different categories: organizational, competence-base, and tools. The differencesbetween the companies and in what way these different resources influence the formation ofdifferent logistics capabilities to support system supply are discussed.</p><p>The conclusions drawn from comparing the three companies point out five system capabilities.One is the importance of a clear and distinct organization where the management understandsits role and responsibilities, managing its part of a larger system and its inherent processes.Supply chain management is another important system capability, where logistics skills andenhanced understanding and use of IT and other tools are identified as areas to improve for thesmaller companies. The importance of managing internal and external relations with extrafocus on customer relations is stressed. This also generally requires more overall managementof communications, making the best possible use of existing information and communicationstechnology. Finally, a basic and order-qualifying capability of managing the “genericdemands” is emphasized.</p>
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Power Amplifier Circuits in CMOS TechnologiesFritzin, Jonas January 2009 (has links)
<p>The wireless market has experienced a remarkable development and growth since the introduction of the first mobile phone systems, with a steady increase in the number of subscribers, new application areas, and higher data rates. As mobile phones and wireless connectivity have become consumer mass markets, a prime goal of the IC manufacturers is to provide low-cost solutions.</p><p>The power amplifier (PA) is a key building block in all RF transmitters. To lower the costs and allow full integration of a complete radio System-on-Chip (SoC), it is desirable to integrate the entire transceiver and the PA in a single CMOS chip. While digital circuits benefit from the technology scaling, it is becoming significantly harder to meet the stringent requirements on linearity, output power, and power efficiency of PAs at lower supply voltages. This has recently triggered extensive studies to investigate the impact of different circuit techniques, design methodologies, and design trade-offs on functionality of PAs in nanometer CMOS technologies.</p><p>This thesis addresses the potential of integrating linear and highly efficient PAs and PA architectures in nanometer CMOS technologies at GHz frequencies. In total four PAs have been designed, two linear PAs and two switched PAs. Two PAs have been designed in a 65nm CMOS technology, targeting the 802.11n WLAN standard operating in the 2.4-2.5GHz frequency band with stringent requirements on linearity. The first linear PA is a two-stage amplifier with LC-based input and interstage matching networks, and the second linear PA is a two-stage PA with transformer-based input and interstage matching networks. Both designs were evaluated for a 72.2Mbit/s, 64-QAM 802.11n OFDM signal with a PAPR of 9.1dB. Both PAs fulfilled the toughest EVM requirement of the standard at average output power levels of 9.4dBm and 11.6dBm, respectively. Matching techniques in both PAs are discussed as well.</p><p>Two Class-E PAs have been designed in 130nm CMOS and operated at low ‘digital’ supply voltages. The first PA is intended for DECT, while the second is intended for Bluetooth. At 1.5V supply voltage and 1.85GHz, the DECT PA delivered +26.4dBm of output power with a drain efficiency (DE) and poweradded efficiency (PAE) of 41% and 30%, respectively. The Bluetooth PA had an output power of +22.7dBm at 1.0V with a DE and PAE of 48% and 36%, respectively, at 2.45GHz. The Class-E amplifier stage is also suitable for employment in different linearization techniques like Polar Modulation and Outphasing, where a highly efficient Class-E PA is crucial for a successful implementation.</p>
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Planning Methods for Aerial Exploration and Ground Target TrackingSkoglar, Per January 2009 (has links)
<p>This thesis considers unmanned airborne surveillance systems equipped with electroopticalvision sensors. The aim is to increase the level of autonomy and improve thesystem performance by the use of planning methods for aerial exploration and targettracking. The general problem is very complex due to the “curse-of-dimensionality” andsuboptimal approaches are necessary in order to handle advanced surveillance missions.A general planning framework is proposed and the planner contains a high-level schedulerand a number of planning modes. Each mode consists of planning modules thatsolve smaller sub-tasks and in this thesis a number of these modules are developed. Inparticular, two major approaches are treated; information based planning, and Bayesiantarget search. In addition, the on-road target tracking problem is treated in detail and analgorithm based on the Particle filter is presented.</p><p>In information based planning, different information measures are used to solve theoptimal trajectory planning problem for bearings-only estimation. Thus, the problem ishow to maneuver an unmanned aerial vehicle (UAV) to achieve the best possible estimateof a target location while observing it with a vision sensor. Approaches based on the Informationfilter and the differential entropy are proposed. The Information filter approachis also used to develop an exploration framework where the UAV flight trajectory and thesensor pointing direction are considered concurrently.</p><p>In Bayesian target search, the aim is to find a target as quickly as possible givensome prior knowledge of where it might be. Methods based on both gradient search andcombinatorial optimization routines are proposed for the search problem where a UAV isequipped with a controllable vision sensor with limited field-of-view.</p>
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Computerized maintenance management systemRuud, Niklas January 2009 (has links)
<p>In this thesis have an implementation of a maintenance program called Computerized Maintenance Management System that has been developed together with the personal from SKF. The work has been conducted for 10 weeks at Sapa Thermal Heat Transfer (Shanghai) Ltd on the maintenance department. Sapa manufacture, sell and deliver to the automobile market. The goal has been to understand and learn how to use the new computer system CMMS. It shall help Sapa to save on doing unnecessary maintenance and make it easier to order spare part, scheduled maintenance and to see the problems and the solution the problems in the CMMS database. My report is limited to parts of the CMMS. The edge guides critical points that are the position transducer and the vertical roller bearing. I describe the failures that can occur and recommend some solutions to the problems. With the creation of different concepts, explanations are given to guide you to the right solution. I give a short introduction to the current maintenance in Sapa and how to update the database through the creating of a user manual directed to Sapa. Interviews have been conducted at Sapa maintenance department with SKF and API Pro personal. The biggest helping tool has been from the CMMS there I have been able to read about current problems with the edge guide. Fact has also been taken from the Internet and material provided by Sapa The report shows a few recommendations and helping tools for how to continue the update in the CMMS for the new hot mill. Optimize the maintenance to the smallest component with the goal of saving money and production time. The reason is that CMMS shall contribute to manage the maintenance so much that the machine should have availability above 90 percent.</p>
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Design of High‐Speed, Low‐Power, Nyquist Analog‐to‐Digital ConvertersSundström, Timmy January 2009 (has links)
<p>The scaling of CMOS technologies has increased the performance of general purposeprocessors and DSPs while analog circuits designed in the same process have not been ableto utilize the process scaling to the same extent, suffering from reduced voltage headroom and reduced analog gain. In order to design efficient analog‐to‐digital converters in nanoscale CMOS there is a need to both understand the physical limitations as well as to develop new architectures and circuits that take full advantage of what the process has tooffer.</p><p>This thesis explores the power dissipation of Nyquist rate analog‐to‐digital converters andtheir lower bounds, set by both the thermal noise limit and the minimum device and feature sizes offered by the process. The use of digital error correction, which allows for lowaccuracy analog components leads to a power dissipation reduction. Developing the bounds for power dissipation based on this concept, it is seen that the power of low‐to‐medium resolution converters is reduced when going to more modern CMOS processes, something which is supported by published results.</p><p>The design of comparators is studied in detail and a new topology is proposed which reduces the kickback by 6x compared to conventional topologies. This comparator is used in two flash ADCs, the first employing redundancy in the comparator array, allowing for the use of small sized, low‐power, low‐accuracy comparators to achieve an overall low‐power solution. The flash ADC achieves 4 effective bits at 2.5 GS/s while dissipating 30 mW of power.</p><p>The concept of low‐accuracy components is taken to its edge in the second ADC which oes not include a reference network, instead relying on the process variations to generate the reference levels based on the mismatch induced comparator offsets. The reference‐free ADC achieves a resolution of 3.69 bits at 1.5 GS/s while dissipation 23 mW showing that process variations not necessarily must be seen as detrimental to circuit performance but rather can be seen as a source of diversity.</p>
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