A monolithically integrated broadly tunable MQW laser that utilizes a combined impurity-free vacancy disordering (IFVD) of quantum wells and optical beam steering techniques is proposed and investigated experimentally. The device consists of a beam-steering section and an optical amplifier section fabricated on a GaAs/AlGaAs quantum well (QW) p-i-n heterostructure. The beam steering section forms a reconfigurable optical waveguide that can be moved laterally by applying separately controlled electrical currents to two parallel contact stripes. The active core of the gain section is divided in into selectively intermixed regions. The selective intermixing of the QW in the gain section results in neighboring regions with different optical bandgaps. The wavelength tuning is accomplished by steering the amplified optical beam through the selected region where it experiences a peak in the gain spectrum determined by the degree of intermixing of the QW. The laser wavelength tunes to the peak in the gain spectrum of that region. The IFVD technique relies on a silica (SiO2) capped rapid thermal annealing and it has been found that the degree of intermixing of the QW with the barrier material is dependent on the thickness of the SiO2 film. The QW sample is first encapsulated with a 400nm thick SiO2 film grown by plasma enhanced chemical vapor deposition (PECVD). In the gain section, the SiO2 film is selectively etched using multiple photolithographic and reactive ion etching steps whereas the SiO2 film is left intact in all the remaining areas including the beam-steering section. The selective area quantum well intermixing is then induced by a single rapid thermal annealing step at 975°C for a 20s duration to realize a structure with quantum well that has different bandgaps in the key regions. Optical characterizations of the intermixed regions have shown a blue shift of peak of the electroluminescence emission of 5nm, 16nm and 33nm for the uncapped, 100nm and 200nm iv respectively when compared to the as grown sample. The integrated laser exhibited a wavelength tuning range of 17nm (799nm to 816nm). Based on the same principle of QW selective intermixing, we have also designed and fabricated a monolithically integrated multi-wavelength light emitting diode (LED). The LED emits multiple wavelength optical beams from one compact easy to fabricate QW structure. Each wavelength has an independent optical power control, allowing the LED to emit one or more wavelengths at once. The material for the LED is the same AlGaAs/GaAs QW p-i-n heterostructure described above. The device is divided into selectively intermixed regions on a single QW structure using IFVD technique to create localized intermixed regions. Two different designs have been implemented to realize either an LED with multiple output beams of different wavelengths or an LED with a single output beam that has dual wavelength operation capabilities. Experimental results of the multiple output beams LED have demonstrated electrically controlled optical emission of 800nm, 789nm and 772nm. The single output LED has experimentally been shown to produce wavelength emission of 800nm and/or 772nm depending on electrical activation of the two aligned intermixed regions.

No / A vehicle that deviates laterally from its intended path of travel when the brakes are applied is considered to demonstrate ‘instability’ in the form of an unexpected and undesirable response to the driver input. Even where the magnitude of lateral displacement of the vehicle is small (i.e. ‘drift’ rather than ‘pull’) such a condition would be considered unacceptable by manufacturers and customers. Steering ‘drift’ during braking can be caused by several factors, some of which relate to vehicle design and others to external influences such as road conditions. The study presented here examines the causes and effects of steering drift during straight-line braking. A comparative analysis is made between two types of vehicle model: one built with rigid suspension components and the other with flexible components. In both the cases, the vehicle behaviour is simulated during braking in a straight line, and responses including lateral acceleration, yaw rate, and lateral displacement of the vehicle are predicted and analysed under fixed steering control. Suspension/steering geometry characteristics, namely toe steer and caster angle, have been studied to understand how the effect of variations in these parameters differs in models with rigid or flexible components drift during straight-line braking. Results from both vehicle models show that differences between rigid and flexible components can affect the predicted steering drift propensity. The differences between the two models have emphasized the importance of using flexible (compliant) components in vehicle handling simulations to achieve better correlation between prediction and experiment.

The development of phased array antenna systems requires considerable resources and time. Due to this constraint, the Naval Air Command (NAVAIR) needs a phased array that can be physically reconfigured to meet the demands of multiple missions without added development time or cost. This work develops and demonstrates a solution to this problem by implementing an adaptive calibration approach to the development of electronically steerable antennas (ESAs). In contrast to previous analog adaptive beamformer systems, this system allows for an arbitrary antenna configuration with a variable number of antenna elements and locations. A simulation model of arbitrary phased array configurations was developed to test the beamformer calibration algorithm and was used to show practical tile locations. To demonstrate this approach, four 4x4 ULA phased array antenna tiles were built and tested together in various configurations to show the viability of developing a physically reconfigurable phased array system.

Automated vehicles (AVs) have been developing at a rapid pace over the past few years. However, many difficulties still remain for achieving full Level-5 AVs. This signifies that AVs still require human operators to intervene or assist, such as taking over control of AVs or selecting their routes. Therefore, teleoperation can be seen as a subsystem of AVs that can remotely control and supervise a vehicle when needed. However, teleoperated driving conditions are largely different from real-life driving, so remote drivers may experience different driving feedback. In such a situation, therefore, the driving behaviour and performance of remote drivers can also be impacted. The following three studies were conducted to investigate these points. First, a seamless comparative study was carried out between teleoperated and real-life driving. Driving behaviour and performance were compared in two scenarios: slalom and lane following. Significant differences in driving behaviour and performance between them were found in the study. The lane following deviation during teleoperated driving is much greater than that of real-life driving. In addition, remote drivers are more likely to drive slower and make more steering corrections in lane following manoeuvres. Second, three types of steering force feedback (SFF) modes were compared separately in both teleoperated and real-life driving to investigate the effect of SFF on driving experience. The three SFF modes consist of Physical model-based steering force Feedback (PsF), Modular model-based steering force Feedback (MsF), and No steering force Feedback (NsF). The difference between PsF and MsF is that the main forces come from different sources, namely the estimated tyre force and steering motor current, respectively. As expected, the experimental results indicate that NsF would significantly reduce the driving experience in both driving conditions. In addition, remote drivers were found to require reduced steering feedback force and returnability. Finally, the influence of motion-cueing, sound, and vibration feedback on driving behaviour and experience was studied in a virtual teleoperation platform based on the IPG CarMaker environment. The prototype of a teleoperated driving station (TDS) with motion-cueing, sound, and vibration feedback was first developed to study human factors in teleoperated driving. Then, the low-speed disturbance scenario and high-speed dynamic scenario were used separately to investigate how these factors affect driving. Experimental results indicate that sound and vibration feedback can be an important factor in speed control by providing remote drivers a sense of speed. In the low-speed disturbance scenario, motion-cueing feedback can help with road surface perception and improve the driving experience. However, it did not significantly improve driving performance in the high-speed dynamic scenario. The research conducted reveals how driving behaviour may change in teleoperated driving and how different driving feedback influences it. These results could provide guidance for improving teleoperated driving in future research and serve as a guide for policymaking related to teleoperation. / Självkörande fordon (AV) har utvecklats i snabb takt de senaste åren. Men det finns fortfarande många utmaningar innan man når  helt självkörande fordon. Följaktligen krävs fortfarande säkerhetsförare när AV-enheter är i drift och i framtida drift kan AV-enheter stöta på oväntade problem som en människa behöver lösa. Fjärrövervakning kan därför ses som ett  backupsystem, som kan fjärrstyra och övervaka fordonet när det inte fungerar. Men situationen  vid fjärrstyrning är helt annorlunda än för körning i verkligheten, där fjärroperatörer kan uppleva olik återkoppling  och känslor jämfört med körning i verkligheten. Därför kan även fjärroperatörernas körbeteende och prestanda ändras i denna situation. För att undersöka detta utfördes följande tre studier. För det första genomfördes en sömlös jämförelsestudie mellan fjärrstyrning och verklig körning. Körbeteende och prestanda jämfördes i två scenarier, nämligen slalom och linjeföljning. Signifikanta skillnader i körbeteende och prestanda hittades mellan fjärrstyrning och körning i verkligheten. Avvikelse från linjeföljning vid fjärrstyrning är betydligt större än för körning i verkligheten. Dessutom är det mer sannolikt att fjärroperatörer kör i lägre hastigheter och gör fler styrkorrigeringar vid fjärrstyrning.  För det andra jämfördes tre typer av styrkraftsåterkopplingsmodeller (SFF) separat i både fjärrstyrning och verklig körning för att undersöka SFF:s inverkan på körupplevelsen. De tre SFF-modellerna inkluderar en  modell för fysisk återkoppling (PsF), modell för modulär återkoppling (MsF) och ingen återkoppling (NsF). Skillnaden mellan PsF och MsF är att huvudkrafterna härrör från olika källor, nämligen respektive från den matematiskt uppskattade däckkraften och från styrmotorströmmen. Som förväntat tyder resultaten av experimentet på att NsF avsevärt skulle minska körupplevelsen vid både fjärrstyrning och körning i verkligheten. Vid fjärrstyrning upptäcktes också  att operatörer kräver minskad styråterkopplingskraft och returförmåga.  Slutligen studerades påverkan av rörelsestyrning, ljud och vibrationsfeedback på körbeteende och upplevelse. Prototypen av fjärrkontrolltorn  med rörelsestyrning, ljud och vibrationsfeedback utvecklades först för att studera mänskliga faktorer vid fjärrstyrning. Sedan användes ett låghastighetsscenario med störningar och det dynamiska höghastighetsscenariot separat för att undersöka hur dessa faktorer påverkar körning vid fjärrstyrning. Resultaten av experimentet indikerar att ljud- och vibrationsåterkoppling kan vara till stor hjälp för att reglera  hastigheten genom att ge operatörerna medvetenhet om hastighet. I låghastighetsscenariot kan återkoppling  från rörelsestyrning underlätta uppfattningen av vägytan och förbättra körupplevelsen. Den ökade dock inte nämnvärt dynamisk körprestanda  i hög hastighet.  Denna forskning undersöker hur körbeteendet kan förändras vid fjärrstyrning och hur olika återkopplingar till operatör påverka körning på distans. Dessa resultat kan  ge vägledning om hur man kan förbättra fjärrstyrning i framtida forskning och fungera som en referens för skapande av regler kopplat till fjärrövervakning och fjärrstyrning. / <p>QC 230504</p>

In this thesis, a Model Predictive Control (MPC) based re-planning and control system is proposed. The MPC re-planner will generate a collision-free path for the controlled vehicle when obstacles are detected, and the controller will make the vehicle move along the reference or re-planned path by adjusting its velocity and steering angle. The MPC re-planner and controller are built based on different vehicle dynamic models, i.e., the bicycle model and point-mass model, respectively. Simulation results show that the trajectory tracking performance when the velocity and steering are controlled simultaneously are better than using steering MPC alone. Then the effects on computational time of two critical parameters, prediction horizon and control horizon, are studied to find reasonable horizons that can enable real-time control. The robustness of the obstacle avoidance function is tested using obstacles with increasing sizes and the results show that the controlled vehicle is able to avoid a 6 m obstacle so that it can overtake other car-like vehicles in the driving process. Finally, a closed-loop one-lane road with some moving vehicles is built as a test scenario for the MPC-based re-planning and control system. According to the results, the controlled vehicle can successfully follow the centerline of the road and overtake other vehicles. / I detta examensarbete föreslås ett fordonsreglersystem baserat på modellprediktiv reglering (MPC) med en omplaneringsfunktion. Det MPC-baserade omplaneringssystemet ska hitta en kollisionsfri väg åt det reglerade fordonet när hinder upptäcks på vägen och hastighet samt styrvinkel anpassas med hjälp av reglersystemet så att fordonet kan köra längs referensvägen eller den nya vägen efter omplaneringen. Det MPC-baserade fordonsregler- och omplaneringssystemet är uppbyggt baserat på olika fordonsdynamiska modeller, cykelmodellen och en punktmassemodell. Simuleringsresultaten visar att prestandan för trajektorieföljningen är avsevärt bättre i fallet då både fordonshastighet och styrvinkel regleras jämfört med att enbart reglera styrvinkeln. Därefter studerades vilken inverkan två kritiska parametrar, förutsägelsehorisont och reglerhorisont, har på simuleringstiden för att hitta rimliga horisonter som kan möjliggöra realtidsreglering. Omplaneringsfunktionens robusthet utvärderades med hjälp av olika hinder med ökande storlekar. Resultaten visar att det reglerade fordonet har förmåga att undvika hinder upp till sex meters storlek, vilket betyder att fordonet kan passera andra billiknande fordon under körning. Slutligen, för att utvärdera det MPC-baserade regler- och omplaneringssystemet skapas ett testscenario där fordonet kör på en enfilig väg och där det finns andra fordon i rörelse samtidigt. Enligt simuleringsresultaten så kan det reglerade fordonet följa vägens mittlinje samt köra om de andra fordonen som färdas på samma väg.

No description available.

No description available.

No description available.

A problem solving environment (PSE) is a computational system that provides a complete and convenient set of high level tools for solving problems from a specific domain. This thesis takes an in-depth look at the experiment management aspect of PSEs, which can be divided into three levels: 1) data management, 2) change management, and 3) execution management. At the data management level, anything related to an experiment (computer simulation) should be stored and documented. A database management system can be used to store the simulation runs for a PSE. Then various high level interfaces can be provided to allow users to save, retrieve, search, and compare these simulation runs. At the change management level, a scientist should only focus on how to solve a problem in the experiment domain. Aside from running experiments, a scientist may only consider how to define a new model, how to modify an existing model, and how to interpret an experiment result. By using XML to describe a simulation model and unify various implementation layers, changing an existing model in a PSE can be intuitive and fast. At the execution management level, how an experiment is executed is the main concern. By providing a computational steering capability, a scientist can pause, examine, and compare the intermediate results from a simulation. Contrasted with the traditional way of running a lengthy simulation to see the result at the end, computational steering can leverage the user's expert knowledge on the fly (during the simulation run) and provide new insights and new product design opportunities. This thesis illustrates these concepts and implementation by using WBCSim as an example. WBCSim is a PSE that increases the productivity of wood scientists conducting research on wood-based composite materials and manufacturing processes. It integrates Fortran 90 simulation codes with a Web based graphical front end, an optimization tool, and various visualization tools. The WBCSim project was begun in 1997 with support from United States Department of Agriculture, Department of Energy, and Virginia Tech. It has since been used by students in several wood science classes, by graduate students and faculty, and by researchers at several forest products companies. WBCSim also serves as a test bed for the design, construction, and evaluation of useful, production quality PSEs. / Ph. D.

The thesis has been done in collaboration with Kalmar Solutions AB and is a conceptual study that aims to design a hydraulic steering arrangement for the reachstacker DRG 450 where each wheel is steered independently of each other. This is done in order to reduce tire wear by achieving an Ackermann steering geometry; lesser tire wear reduces costs for customers. When steered independently of each other the same steering arrangement could be used on multiple different wheelbases while still achieving an Ackermann steering geometry. During the thesis, calculations for required steering angles and their required piston strokes has been done by creating a geometrical model of the steering arrangement. CAD-modeling and kinematic simulations of concepts has been conducted with CATIA R2024x where the concepts movement when turning could be simulated. Three main concepts of the steering arrangement were studied and developed during the thesis. Kinematic simulations concluded that by changing to two independent cylinders, along the same axis, and redesigning the steering knuckles could allow for the same steering arrangement to achieve an Ackermann steering geometry for multiple different wheelbases. This reduces tire wear and turning radius when compared to the current steering axle. Having the cylinders along the same axis proved to be best because less redesigns were needed and mainly no major redimensioning of the steering arrangement or chassis were needed.