Floating offshore wind turbines show great potential within the energy industry, especially for deeper waters where traditional fixed-bottom turbines cannot be used. Offshore locations also offer stronger and more stable winds compared to onshore locations. The study explores the impact of the secondary machine efficiency on the electricity production in a Counter Rotating Axis Floating Tilting (CRAFT) wind turbine. The counter-rotating design holds promise for achieving high overall system efficiency.  MATLAB simulations show that it is possible to maintain a lower secondary machine efficiency without compromising stability. Reviewing two control systems confirms that using a robust control algorithm with optimized TSR ensures system stability in both high and low winds. A decrease in secondary electric machine efficiency from 97% to 93% resulted in a 0.03% reduction in annually generated electricity, whereas a similar decrease in primary electric generator efficiency led to a 1% reduction instead. Decreasing the secondary machine efficiency further to 83% resulted in a 0.1% reduction in annual generated electricity. Thus, the secondary machine's efficiency is shown to be less critical for the electricity production than the primary generator’s efficiency.  Choosing an asynchronous over a synchronous option as the secondary machine is economically advantageous since its lower efficiency of 83% instead of 97% does not significantly affect the electricity production. Moreover, the lower magnet cost for the asynchronous machines positively impacts economic metrics like LCoE, NPVI and payback period, making the asynchronous generator a more favourable economic choice. Further research areas to obtain higher accuracy include integrating differences in maintenance costs and conducting a more in-depth assessment of the investment costs associated with the two types of generators. Additionally, considering airflow losses around turbine blades and airflow interaction amongst the turbines could further enhance the model accuracy.

This thesis studies wave energy converters developed at Uppsala University. The wave energy converters are of point absorbing type with direct driven linear generators. The aim has been to study generator design with closed stator slots as well as offshore experimental studies. By closing the stator slots, the harmonic content in the magnetic flux density is reduced and as a result the cogging forces in the generator are reduced as well. By reducing these forces, the noise and vibrations from the generator can be lowered. The studies have shown a significant reduction in the cogging forces in the generator. Moreover, by closing the slots, the magnetic flux finds a short-cut through the closed slots and will lower the magnetic flux linking the windings. The experimental studies have focused on the motion of the translator. The weight of the translator has a significant impact on the power absorption, especially in the downward motion. Two different experiments have been studied with two different translator weights. The results show that with a higher translator weight the power absorption is more evenly produced between the upward and downward motion as was expected from the simulation models. Furthermore, studies on the influence of the changing active area have been conducted which show some benefits with a changing active area during the downward motion. The experimental results also indicate snatch-loads for the wave energy converter with a lower translator weight. Within this thesis results from a comparative study between two WECs with almost identical properties have been presented. The generators electrical properties and the buoy volumes are the same, but with different buoy heights and diameters. Moreover, experimental studies including the conversion from AC to DC have been achieved. The work in this thesis is part of a larger wave power project at Uppsala University. The project studies the whole process from the energy absorption from the waves to the connection to the electrical grid. The project has a test-site at the west coast of Sweden near the town of Lysekil, where wave energy systems have been studied since 2004.

International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California / This paper presents a new approach for the effective generation of translator scripts that can be used to automate the translation of data display configurations from one vendor format to another. Our approach uses the IDEF5 ontology description method to capture the ontology of each vendor format and provides simple rules for performing mappings. In addition, the method includes the specification of mappings between a language-specific ontology and its corresponding syntax specification, that is, either an eXtensible Markup Language (XML) Schema or Document Type Description (DTD). Finally, we provide an algorithm for automatically generating eXtensible Stylesheet Language Transformation (XSLT) scripts that transform XML documents from one language to another. The method is implemented in a graphical tool called the Data Display Translator Generator (DDTG) that supports both inter-language (ontology-to-ontology) and intra-language (syntax-to-ontology) mappings and generates the XSLT scripts. The tool renders the XML Schema or DTD as trees, provides intuitive, user-friendly interfaces for performing the mappings, and provides a report of completed mappings. It also generates data type conversion code when both the source and target syntaxes are XML Schema-based. Our approach has the advantage of performing language mappings at an abstract, ontology level, and facilitates the mapping of tool ontologies to a common domain ontology (in our case, Data Display Markup Language or DDML), thereby eliminating the O(n^2) mapping problem that involves a number of data formats in the same domain.

In this thesis we model two very different movement-related neuronal circuits, both of which produce oscillatory patterns of activity. In one case we study oscillatory activity in the basal ganglia under both normal and Parkinsonian conditions. First, we used a detailed Hodgkin-Huxley type spiking model to investigate the activity patterns that arise when oscillatory cortical input is transmitted to the globus pallidus via the subthalamic nucleus. Our model reproduced a result from rodent studies which shows that two anti-phase oscillatory groups of pallidal neurons appear under Parkinsonian conditions. Secondly, we used a population model of the basal ganglia to study whether oscillations could be locally generated. The basal ganglia are thought to be organised into multiple parallel channels. In our model, isolated channels could not generate oscillations, but if the lateral inhibition between channels is sufficiently strong then the network can act as a rhythm-generating ``pacemaker'' circuit. This was particularly true when we used a set of connection strength parameters that represent the basal ganglia under Parkinsonian conditions. Since many things are not known about the anatomy and electrophysiology of the basal ganglia, we also studied oscillatory activity in another, much simpler, movement-related neuronal system: the spinal cord of the Xenopus tadpole. We built a computational model of the spinal cord containing approximately 1,500 biologically realistic Hodgkin-Huxley neurons, with synaptic connectivity derived from a computational model of axon growth. The model produced physiological swimming behaviour and was used to investigate which aspects of axon growth and neuron dynamics are behaviourally important. We found that the oscillatory attractor associated with swimming was remarkably stable, which suggests that, surprisingly, many features of axonal growth and synapse formation are not necessary for swimming to emerge. We also studied how the same spinal cord network can generate a different oscillatory pattern in which neurons on both sides of the body fire synchronously. Our results here suggest that under normal conditions the synchronous state is unstable or weakly stable, but that even small increases in spike transmission delays act to stabilise it. Finally, we found that although the basal ganglia and the tadpole spinal cord are very different systems, the underlying mechanism by which they can produce oscillations may be remarkably similar. Insights from the tadpole model allow us to predict how the basal ganglia model may be capable of producing multiple patterns of oscillatory activity.

International Telemetering Conference Proceedings / October 26-29, 1987 / Town and Country Hotel, San Diego, California / In an Independent Research and Development (IR&D) effort, the Telemetry Systems Operation (TSO) of Computer Sciences Corporation (CSC) sought to determine the feasibility of using Artificial Intelligence (AI) techniques in a real-time processing environment. Specifically, the use of an expert system to assist in telemetry data acquisition processing was studied. A prototype expert system was implemented with the purpose of monitoring F15 Vertical Short Take Off and Landing (VSTOL) aircraft engine tests in order to predict engine stalls. This prototype expert system was implemented on a Symbolics 3670 symbolic processor using Inference Corporation's Artificial Reasoning Tool (ART) expert system compiler/generator. The Symbolics computer was connected to a Gould/SEL 32/6750 real-time processor using a Flavors, Inc. Bus Link for real-time data transfer.

For this project the main goal was to design, simulate, build and test a DC motor driver. To accomplish this four specific parts had to be design. First a DCDC converter that converts the input signal from an external power supply in a controllable DC output. The second part was a DCDC converter that converts the DC input in a voltage useful for the function generator, the third part is the function generator that provides a signal to the H-Bridge, and the final part is the H-Bridge itself. The goal is to compare the measurement with the simulations to the expectations. What we are interested in is the influence of EMF when the RPM of the motor is zero or close to zero.

International Telemetering Conference Proceedings / October 27-30, 1997 / Riviera Hotel and Convention Center, Las Vegas, Nevada / To support the processing of International Space Station (ISS) Payloads, the Kennedy Space Center (KSC) had the need to develop specialized test and validation equipment to quickly identify interface problems between the payload or experiment under test and the communication and telemetry downlink systems. To meet this need, the Payload Data Analyzer (PDA) System was developed by the Data Systems Technology Division (DSTD) of NASA’s Goddard Space Flight Center (GSFC) to provide a suite of troubleshooting tools and data snapshot features allowing for diagnosis and validation of payload interfaces. The PDA System, in conjunction with the Payload Data Generator (PDG) System, allow for a full set of programmable payload validation tools which can quickly be deployed to solve crucial interface problems. This paper describes the architecture and tools built in the PDA which help facilitate Space Station Payload Processing.

ITC/USA 2005 Conference Proceedings / The Forty-First Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2005 / Riviera Hotel & Convention Center, Las Vegas, Nevada / The GPS receiver based on software radio technology is a kind of general purpose GPS signal processing platform which makes use of advanced design ideas and advanced design tools nowadays. We used FPGA device and lots of necessary peripherals such as DSP and PCI controller in our design to promote flexibility and practicability effectively. Various fast acquisition means and accurate tracking algorithms could be realized, improved and validated on this platform, besides basic GPS receiver function.

Large Eddy Simulation (LES) is carried out using the Rolls-Royce Hydra CFD code in order to investigate and give further insight into highly turbulent, unsteady flow structures for automotive applications. LES resolves time dependent eddies that are modelled in the steady-state by Reynolds-Averaged Navier-Stokes (RANS) turbulence models. A standard Smagorinsky subgrid scale model is used to model the energy transfer between large and subgrid scales. Since Hydra is an unstructured algorithm, a variety of unstructured hexahedral, tetrahedral and hybrid grids are used for the different cases investigated. Due to the computational requirements of LES, the cases in this study replicate and analyse generic flow problems through simplified geometry, rather than modelling accurate race car geometry which would lead to infeasible calculations. The first case investigates the flow around a diffuser-equipped bluff body at an experimental Reynolds number of 1.01 times 10 to the power 6 based on model height and inlet velocity. LES is carried out on unstructured hexahedral grids of 10 million and 20 million nodes, with the latter showing improved surface pressure when compared to the experiments. Comparisons of velocity and vorticity between the LES and experiments at the diffuser exit plane show a good level of agreement. Flow visualisation of the vortices in the diffuser region and behind the model from the mean and instantaneous flow attempts to explain the relation or otherwise between the two. The main weakness of the simulation was the late laminar to turbulent transition in the underbody region. The size of the domain and high experimental Reynolds number make this case very challenging. After the challenges faced by the diffuser-equipped bluff body, the underbody region is isolated so that increased grid refinement can be achieved in this region and the calculation is run at a Reynolds number of 220, 000, reducing the computational requirement from the previous case. A vortex generator mounted onto a flat underbody at an onset angle to the flow is modelled to generate vortices that extend along the length of the underbody and its interaction with the ground is analysed. Since the vortex generator resembles a slender wing with an incidence to the flow, a delta wing study is presented as a preliminary step since literature on automotive vortex generators in ground effect is scarce. Results from the delta wing study which is run at an experimental Reynolds number of 1.56 times 10 to the power 6 are in very good agreement with previous experiments and Detached Eddy Simulation (DES) studies, giving improved detail and understanding. Axial velocity and vorticity contours at several chordwise stations show that the leading edge vortices are predicted very well by a 20 million node tetrahedral grid. Sub-structures that originate from the leading edge of the wing and form around the core of the leading edge vortex are also captured. Large Eddy Simulation for the flow around an underbody vortex generator over a smooth ground and a rough ground is presented. A hexahedral grid of 40 million nodes is used for the smooth ground case, whilst a 48 million node hybrid grid was generated for the rough ground case so that the detailed geometry near the ground could be captured by tetrahedral cells. The geometry for the rough surface is modelled by scanning a tarmac surface to capture the cavities and protrusions in the ground. This is the first time that a rough surface representing a tarmac road has been computed in a CFD simulation, so that its effect on vortex decay can be studied. Flow visualisation of the instantaneous flow has shown strong interaction with the ground and the results from this study have given an initial understanding in this area.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: This thesis is a description of how the first magnetically geared axial flux permanent magnet generator (MGAFG) is designed, constructed and experimentally evaluated. Magnetic gears (MGs) allow for contact-less power transfer and lubricant free operation, which may solve the reliability concerns with current mechanically geared wind energy converters. However, the complex structure of MGs may present serious challenges to its design. Thus, special care should be given to the mechanical layout and the electromagnetic influence of every component. The MGAFG can be configured to be magnetically coupled or decoupled. In the coupled configuration the permanent magnets (PMs) of the MG contribute to the total flux linkage in the PM generator (PMG). The coupled configuration is therefore more efficient. The processing time required to optimise the decoupled configuration is however much faster, since the MG and the PMG can be optimised separately. The optimised results show that a torque density in excess of 100kNm/m3 could be achieved, which is significantly higher than any of known electrical machines. However, owing to excessive losses in the mechanical support structures, the prototype exhibited lower torque density and poor efficiency. The design related aspects and issues are analysed and discussed in detail in an attempt to outline problem areas in the design process. Relevant recommendations are also given for future design improvements. The costs of magnetic material accounts for over fifty percent of the total cost of the prototype. Therefore to make the manufacturing of the MGAFG more economically viable magnetic material should be minimised in the design process. / AFRIKAANSE OPSOMMING: In hierdie tesis word die eerste magnetiese geratte aksiale vloed permanente magneet generator (MGAVG) ontwerp, vervaardig en eksperimenteel geëvalueer. In magnetiese ratte (MR) is daar geen kontak tussen werkende dele nie, daarom word geen smeermiddels benodig nie. Dit dra by tot die betroubaarheid van die ratkaste in wind energie generators en kan onderhoud grotendeels uitskakel. Die komplekse struktuur van magnetiese ratte kan egter die betroubaarheid van die ontwerp juis verswak. Daarom moet die meganiese uitleg noukeurig beplan word sodat dit nie die elektromagnetiese werking ondermyn nie. Die magnetiese rat (MR) en die permanente magneet generator (PMG) van die masjien kan magneties of sonder magnetiese koppeling verbind word. In die gekoppelde konfigurasie dra all die permanente magnete van die MR gesamentlik by tot die totale vloed-koppeling in die PMG. Wat die magnetiese gekoppelde konfigurasie meer doeltrefend maak. Minder tyd word benodig om die nie magnetiese gekoppelde konfigurasie te optimaliseer omdat die MR en die PMG apart geoptimaliseer kan word. Die optimale resultate toon dat ’n wringkrag van meer as 100kNm/3 bereik kan word, wat aansienlik beter is as die van bekende elektriese masjiene. Maar as gevolg van oormatige verliese in die meganiese strukture, toon die prototipe lae wringkrag digtheid en swak doeltreffendheid. Die ontwerp probleme word ontleed en bespreek in ’n poging om probleem areas in die ontwerp te identifiseer. Relevante aanbevelings word gegee vir toekomstige ontwerp verbeterings. Die koste van die magnetiese material verteenwoordig meer as vyftig persent van die vervaardigings koste van die prototipe. Koste kan bespaar word op die vervaardiging van die MGAVG deur die hoeveelheid magnete wat gebruik word te beperk.