abstract: Needle steering is an extension of manually inserted needles that allows for maneuverability within the body in order to avoid anatomical obstacles and correct for undesired placement errors. Research into needle steering predominantly exploits interaction forces between a beveled tip and the medium, controlling the direction of forces by applying rotations at the base of the needle shaft in order to steer. These systems are either manually or robotically advanced, but have not achieved clinical relevance due to a multitude of limitations including compression effects in the shaft that cause undesired tissue slicing, torsional friction forces and deflection at tissue boundaries that create control difficulties, and a physical design that inherently restricts the workspace. While most improvements into these systems attempt to innovate the needle design or create tissue models to better understand interaction forces, this paper discusses a promising alternative: magnetic needle steering. Chapter 2 discusses an electromagnetic needle steering system that overcomes all aforementioned issues with traditional steering. The electromagnetic system advances the needle entirely magnetically so it does not encounter any compression or torsion effects, it can steer across tissue-interfaces at various angles of attack (90, 45, 22.5°) with root-mean-square error (RMSE) of 1.2 mm, achieve various radii of curvature as low as 10.2 mm with RMSE of 1.4 mm, and steer along complex 3D paths with RMSE as low as 0.4 mm. Although these results do effectively prove the viability of magnetic steering, the electromagnetic system is limited by a weak magnetic field and small 33mm cubic workspace. In order to overcome these limitations, the use of permanent magnets, which can achieve magnetic forces an order of magnitude larger than similarly sized electromagnetics, is investigated. The needle will be steered toward a permanent magnet configuration that is controlled by a 6 degree-of-freedom robotic manipulator. Three magnet configurations were investigated, two novel ideas that attempt to create local maximum points that stabilize the needle relative to the configuration, and one that pulls the needle toward a single magnet. Ultimately, the last design was found to be most viable to demonstrate the effectiveness of magnetic needle steering. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2020

The Master´s thesis deals with the design of device for vehicle steering stiffness measurement. In the first part were shown the most famous design solution of steering systems and basic parameters of steering geometry. The next part of the thesis is about design of the device which is using power screw. The final part of the thesis is dedicated to analysis of the most important errors which may arise during the measurement.

In an effort to reduce physical testing during the development process of a new vehicle, the automotive industries develop methods that can facilitate the recreation of the physical testing scenarios in virtual environments using simulation software. This thesis aims to develop a method which would help evaluate the vehicle’s dynamic properties without it being subjected to physical testing. The goal is to develop a tool that can be used in an early development phase by the industry and that would allow for modifications and calibration to take place. A vehicle model as well as an electronic stability control implementation is built, and the model’s performance to an ISO3888 part-2 double lane change test is evaluated. Since the handling potentials of the vehicle are rated by its entry speed in that test, the model was subjected to an optimization process where its steering action was controlled in order to achieve the highest possible entry speed to the test in an effort to isolate the vehicle’s dynamic potential from the influence of a human driver when conducting this test. The vehicle modelling procedure is done in steps, from a simple implementation of a linear bicycle model to a more complex implementation of a four-wheel vehicle including roll, tire relaxation and suspension compliance properties as well as a simplified ESC implementation. The results of the steering input optimization process were physically tested on a test track, where the correspondence of the model to the real vehicle was evaluated. By further promoting the vehicle dynamics modelling, this tool can facilitate study more testing scenarios and options and it can serve as a step toward the reduction of the physical testing when the vehicle’s dynamic and handling performance need to be studied and evaluated. / Under utvecklingsprocessen av nya fordon sker en strävan mot att reducera fysiska tester, bilindustrier utvecklar därför metoder för att återskapa fysiska testscenarier i virtuella miljöer med hjälp av simuleringsmjukvara. Denna studie har som målsättning att utveckla en metod, med vilken fordonets dynamiska egenskaper kan utvärderas utan att utföra fysiska tester. Målet är att utveckla ett simuleringsverktyg som, i en tidig utvecklingsfas, kan användas av fordonsindustrin och som skulle införa både modifikations- och kalibreringsmöjligheter i detta skede. Såväl en fordonsmodell som ett anti-sladd system är konstruerat och modellens prestanda i ett dubbelt filbyte, specificerat i ISO3888 del 2, är utvärderad. Då bilens dynamiska prestanda klassificeras utifrån ingångshastigheten i detta test utfördes en optimeringsprocess där hjulens styrvinklar reglerades för att uppnå högsta möjliga hastighet vid testets startposition, detta för att separera fordonets dynamiska klassificering från mänsklig inverkan. Processen att konstruera fordonsmodellen utfördes med succesivt ökande antal av fordonsegenskaper, från en enkel implementering av en linjär cykel-modell till en tvåspårs-modell med krängning, transienta däckegenskaper, hjulupphängningsegenskaper samt ett anti-sladd system. Resultatet av den optimerade styrregleringen testades i motsvarande fordon på en testbana varefter modellen kunde utvärderas med det verkliga testet som referens. Genom en utökad möjlighet till simulering kan detta verktyg ge möjligheten att studera fler scenarier såväl som alternativa modelleringskonfigurationer; det kan reducera fysiska tester då fordons dynamiska prestanda ska klassificeras, studeras samt utvärderas.

In high frequency, high-performance wireless communications, direct line of sight antennas are common. The issue with the line of sight antennas is the need to redirect the physical antenna to achieve the best possible reception. Classical redirections are done by mechanical movements: hand tuning and motors. Our multi-functional re-configurable antenna (MRA) concept allows for electrical and non-mechanical antenna reorientation. This work investigates two important concepts in the development and enhancement of future MRA devices: special, non-interfering, control signal circuitry and nano-sized switching devices that are controlled by the special circuitry. The investigation was conducted with the use of commercially available antenna modeling software: ANSYS High Frequency System Solver.

This study focuses on four English teachers’ perception of the concept of culture linked to teaching language. Semi-structured interviews were carried out in order to investigate how they perceive culture in relation to both their personal views and the steering documents for the educational system. To gain a more in–depth understanding of their perception we asked them about their own perception of their teaching methods and how they in turn perceive the students’ development with regards to intercultural understanding. We applied Eva Gagnestam’s four descriptions of culture to be able to explore the different ways in which the teachers worked with the concept of culture in the English classroom.

no / Reconfigurable beam steering using circular disc microstrip patch antenna with a ring slotis proposed. The overall dimension of the antenna is 5.4×5.4 mm2 printed on a 0.504 mm thick, Rogers RT5870 substrate with relative permittivity 2.3 and loss tangent 0.0012. The designed antenna operates at the expected 5G frequency band 60 GHz with a central coaxial probe feed. TwoNMOS switches are configured to generate three different beam patterns. Activating each switch individually results in a near 70 degree shift in the main beam direction, whereas the frequency characteristics are unchanged. The power gains are between 3.9 dB and 4.8dB for the three states of switches configurations. Simulated results in terms of return loss, peak gains and radiation pattern are presented and show a reasonable agreement at the expected 60 GHz bandfor 5G applications. / The published journal webpage is no longer available.

No / A new approach in achieving beam steering in array antenna is introduced using the genetic algorithm optimization. The binary switching technique uses simple binary ON/OFF diodes placed in the feeding network of the array element to achieve beam steering. Constantly feeding the driven element and continuous binary variation of the ON/OFF state of each parasitic array elements which determines its conducting ability defines a beam steering angle. Each beam steered angle is distinguished by series of binary combination determined by the genetic algorithm. A uniform circular array antenna consisting of 13 elements is used to implement this technique. The simulation and result analysis of the binary switched array is presented with several beam steering angles scanned.

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There has been great interest in antenna array processing (diversity, beamforming, null steering, and spatial multiplexing) to enhance the received signal quality and the capacity of wireless communications systems. However, in order to properly exploit the characteristics of different array processing techniques, understanding trade-offs among different techniques and parametric investigation, which offers an insight as to what parameters determine system performance under different situations is necessary. In this study, we present analytical framework which can facilitate the performance analysis of systems with antenna array. Five original contributions to the performance analysis of antenna array processing are presented in this study. First, we present theoretical outage probability of a system equipped with an array which suppresses a few dominant interering signals in TDMA cellular networks when the fading statistics of interfering signals are independent but non-identically distributed. Most of the related previous works assumed either independent and identically distributed fading statistics among cochannel interferences (CCI) or Rayleigh fading when CCI signals are subject to i.n.d. fading statistics. Secondly, the performance of multi-branch predetection equal gain combiner for different modulation techniques in equally correlated Nakagami-m fading is presented through analytical analysis. Specifically, the characteristic function (CHF) and the moment generating function (MGF) of EGC output with correlated inputs are derived and used to evaluate the average symbol error probability (ASEP) and the outage probability performance, respectively. Thirdly, we derived analytical expression which can be used to analyze the performance of different types of diversity techniques in equally correlated Nakagami-m or Rice fading channels. Fourthly, asymptotic analysis on different types of diversity combiners in generalized fading channels is presented in a unifying way. Finally, we investigate and present the impact of transmit diversity at handsets on the reverse link DS/CDMA systems in terms of capacity and coverage over generalized fading channels through analytical approaches. Then, we validate the analytical results with simulation results and investigate practical issues which are hard to capture through analytical analysis using system level simulator we developed. Although we have mainly focused on applying the analytical framework we have derived in this work to the performance analysis of physical layer algorithms such as spatial diversity and adaptive null steering, the framework can be extended to assist the analysis and design of wireless communication systems such as, to name a few, distributed multiple input multiple output (MIMO) system in cooperative wireless networks, multipath routing protocol analysis in wireless fading channels, and antenna selection problems in MIMO system. / Ph. D.