Comparative Analys is of Direct Torque Control in Three Phase and Five Phase Induction Motor Drives

The Direct Torque Control(DTC)is a type of vector control technique which is used to regulate the torque and hence speed of an induction motor drive.This method is very efficient,cheap and is very easy to execute.The absence of mechanical speed estimators along with the ease of processing and computations make it the most preferred option among all vector control techniques.In this method, only the voltage and current are sensed and they are used to estimate the torque,flux and the angle between the rotor and stator flux.Depending on the torque and flux errors,a suitable voltage vector is selected to keep the errors within the desired tolerance region.At present times,three phase induction motors have become the backbone of industries.Lifts,agricultural pumps,conveyor belts,lathes, cranes,drilling machine,etc.are some of the prominent areas where induction motors have been very effective. These motors can be controlled using the scalar V/F control techniques.However,for applications requiring quick response vector control techniques like DTC are preferred. But the problem lies in the presence of torque ripples in case of DTC of three phase induction motor drive.Recently it has been seen that multiphase induction machines have the inherent feature of low torque pulsations.Hence they have replaced their three phase counterparts in areas like ship propulsions and aerospace industries where higher accuracy is required.This feature along with many other advantages of multiphase induction machines make them a strong competitor to their three phase counterparts in the field of industrial drives.This project aims to study and simulate the conventional DTC technique in a five phase induction machine with the help of MATLAB & Simulink and compare the results with its three phase counterpart to verify the effectiveness of the multiphase machine

Preferential Composition during Nucleation and Growth in Multi-Principal Elements Alloys

The crystallization of complex, concentrated alloys can result in atomic-level short-range order, composition gradients, and phase separation. These features govern the properties of the resulting alloy. While nucleation and growth in single-element metals are well understood, several open questions remain regarding the crystallization of multi-principal component alloys. We use MD to model the crystallization of a five-element, equiatomic alloy modeled after CoCrCuFeNi upon cooling from the melt. Stochastic, homogeneous nucleation results in nuclei with a biased composition distribution, rich in Fe and Co. This deviation from the random sampling of the overall composition is driven by the internal energy and affects nuclei of a wide range of sizes, from tens of atoms all the way to super-critical sizes. This results in short range order and compositional gradients at nanometer scales

Mjerenje udarnog presjeka za zajedničku tvorbu Higgsovog bozona i elektroslabog bozona u konačnim stanjima s dva b kvarka i dva leptona u proton proton sudarima na Velikom hadronskom sudarivaču

This thesis summarizes the analysis in which we measure the cross-section for the production of the standard model Higss boson of 125 GeV in association with an electroweak boson (W or Z). The analysis is performed in the final state where the Higgs boson decays into a pair of b quarks and the electroweak boson decays leptonically resulting in three channels based on the number of charged leptons in the final state (0, 1 or 2 leptons). The analysis uses data recorded by the CMS experiment from proton-proton collisions at √s= 13 TeV in the LHC during the full Run 2 data taking period (2016-2018). The recorded data corresponds to an integrated luminosity of 138 fb−1. The analysis searches for 2 b-jets produced from b-quarks originating from the Higgs boson along with lepton candidates decaying from the vector boson. The mass of the Higgs boson is reconstructed from the four momenta of the b-jets which are identified using b-tagging algorithms. To account for events with a Lorentz boosted Higgs boson, a single large cone jet is reconstructed which consists of the two b-jets merged together due to the boost. Taking this into account, separate analysis called the boosted analysis is performed along with the nominal resolved analysis to improve sensitivity in high pT phase space. Both resolved and boosted analysis are combined together in the final fit to enhance precision of the measurement. To reduce the dependency on theoretical uncertainties this measurement is performed in the simplified template cross-section (STXS) scheme. This also allows for straightforward comparison of theoretical models using such measurements. Under this scheme, the cross section measurement is done in regions delineated by type of vector boson (W or Z), vector boson transverse momentum (pT ), and the presence of additional jets.Budući da se udarni presjeci mjere u shemi STXS, konačni skup događaja u kanalu i u svakoj regiji (signal ili kontrola) dalje se dijele prema shemi predloška STXS. Prilagodba maksimalne vjerodostojnosti izvodi se istovremeno u signalnim i kontrolnim područjima za svako STXS područje kako bi se dobio modifikator jačine signala (μ) koji označava omjer promatranog broja VHbb događaja u odnosu na onaj koji se očekuje u SM-u. μ=1 predstavlja udarni presjek u skladu s SM-om

Lower Body Exoskeleton Powered by Epidermal Electronics Systems

The purpose of our design revolves around the concept of enhancing the human body through the use of a lower body exoskeleton. The most applicable demographics for our design consists of paraplegics and non-paraplegics. The various uses we hope to include would allow the user to: walk again, lift heavier loads with the ability to move forward, back and be seated. Although lower body exoskeletons already exist on the market, they still have shortcomings that prevent widespread use among the general public. Our hope is to improve upon the design of existing exoskeletons with the integration of epidermal electronic systems (EES) with a hydraulic systems; allowing more functionality with less human metabolic consumption. We want the system to do most of the work for the user; to further our vision of minimalistic effort. The system will function by utilizing skin surface electromyogram signals (EMG); sent by muscles in the forearms. The signals will be picked up by the epidermal attachments transmitting them wirelessly to a microcontroller, activating the exoskeleton motion. A rigid, yet flexible frame will support the hydraulic systems and electronic components. One to two hydraulic pumps will be needed for three cylinders. One hydraulic cylinder, per leg, will be attached from the hamstring to the calf muscle. The third will be located at the hip, lifting the leg close to a ninety degree angle. The process for completing the lower body exoskeleton is split into three components: the hydraulic system, the electronic components, and the EES “tattoo.” The first step involves creating a CAD design of the frame and hydraulics. Francis Azari will be welding together the frame and attaching the cylinders to these frame at a machine shop with the assistance of Forrest Baber and Karan Patel. Saswat Mishra and Juan Soto will work together to program the Arduino Microcontroller and wire it to calibrate the hydraulic cylinders. Lastly, the EES “tattoo” will be fabricated by Saswat and Karan, using UV-Lithography in the VCU clean room. Our method of achieving our goal consists of splitting up into smaller groups; allowing us to complete work more efficiently. In order to allow ample time to complete the frame of the exoskeleton, the mechanical and electrical work has been split into the fall and spring semesters, respectively. By late December, we want the frame and hydraulic system to be completed so that we may begin coding and fabricating the EES in January. If all minimum goals can be completed early, we hope to include more features that will enhance the functionality of the suit.https://scholarscompass.vcu.edu/capstone/1054/thumbnail.jp

Mass uptake during oxidation of metallic alloys: literature data collection, analysis, and FAIR sharing

The area-normalized change of mass ($\Delta$m/A) with time during the oxidation of metallic alloys is commonly used to assess oxidation resistance. Analyses of such data can also aid in evaluating underlying oxidation mechanisms. We performed an exhaustive literature search and digitized normalized mass change vs. time data for 407 alloys. To maximize the impact of these and future mass uptake data, we developed and published an open, online, computational workflow that fits the data to various models of oxidation kinetics, uses Bayesian statistics for model selection, and makes the raw data and model parameters available via a queryable database. The tool, Refractory Oxidation Database (https://nanohub.org/tools/refoxdb/), uses nanoHUB's Sim2Ls to make the workflow and data (including metadata) findable, accessible, interoperable, and reusable (FAIR). We find that the models selected by the original authors do not match the most likely one according to the Bayesian information criterion (BIC) in 71% of the cases. Further, in 56% of the cases, the published model was not even in the top 3 models according to the BIC. These numbers were obtained assuming an experimental noise of 2.5% of the mass gain range, a smaller noise leads to more discrepancies. The RefOxDB tool is open access and researchers can add their own raw data (those to be included in future publications, as well as negative results) for analysis and to share their work with the community. Such consistent and systematic analysis of open, community generated data can significantly accelerate the development of machine-learning models for oxidation behavior and assist in the understanding and improvement of oxidation resistance

Fully portable and wireless universal brain-machine interfaces enabled by flexible scalp electronics and deep-learning algorithm

Variation in human brains creates difficulty in implementing electroencephalography (EEG) into universal brain-machine interfaces (BMI). Conventional EEG systems typically suffer from motion artifacts, extensive preparation time, and bulky equipment, while existing EEG classification methods require training on a per-subject or per-session basis. Here, we introduce a fully portable, wireless, flexible scalp electronic system, incorporating a set of dry electrodes and flexible membrane circuit. Time domain analysis using convolutional neural networks allows for an accurate, real-time classification of steady-state visually evoked potentials on the occipital lobe. Simultaneous comparison of EEG signals with two commercial systems captures the improved performance of the flexible electronics with significant reduction of noise and electromagnetic interference. The two-channel scalp electronic system achieves a high information transfer rate (122.1 ± 3.53 bits per minute) with six human subjects, allowing for a wireless, real-time, universal EEG classification for an electronic wheelchair, motorized vehicle, and keyboard-less presentation

Soft, wireless periocular wearable electronics for real-time detection of eye vergence in a virtual reality toward mobile eye therapies

Ocular disorders are currently affecting the developed world, causing loss of productivity in adults and children. While the cause of such disorders is not clear, neurological issues are often considered as the biggest possibility. Treatment of strabismus and vergence requires an invasive surgery or clinic-based vision therapy that has been used for decades due to the lack of alternatives such as portable therapeutic tools. Recent advancement in electronic packaging and image processing techniques have opened the possibility for optics-based portable eye tracking approaches, but several technical and safety hurdles limit the implementation of the technology in wearable applications. Here, we introduce a fully wearable, wireless soft electronic system that offers a portable, highly sensitive tracking of eye movements (vergence) via the combination of skin-conformal sensors and a virtual reality system. Advancement of material processing and printing technologies based on aerosol jet printing enables reliable manufacturing of skin-like sensors, while a flexible electronic circuit is prepared by the integration of chip components onto a soft elastomeric membrane. Analytical and computational study of a data classification algorithm provides a highly accurate tool for real-time detection and classification of ocular motions. In vivo demonstration with 14 human subjects captures the potential of the wearable electronics as a portable therapy system, which can be easily synchronized with a virtual reality headset

Soft material-enabled flexible electronics for disease diagnostics, therapeutics, and healthcare

The United States healthcare costs are approaching half a trillion dollars annually while mortality rates continue to rise from neurodegenerative and systemic diseases. Preemptive and therapeutics care is an alternative to expensive surgeries in order to reduce costs. Popularity with wearable devices enables in vivo biosensing platforms, but the existing devices are heavy, rigid, and bulky which inherently disrupts high-quality data recording and causes discomfort. This thesis optimizes the mechanics and materials for a soft material platform integrated with open-mesh, serpentine structures for extreme flexibility and stretchability. Mechanical integration of these sensors and devices is enabled by printing techniques using photolithography and aerosol jet printing. Ultimately these sensors need to be comfortable for long term wear but it also needs to be thin for Virtual Reality applications involving ocular therapy. My therapeutic platform aims to improve quality of eye vergence movements with practice in a virtual reality display. The wearable “skin-like” electrodes enhance the recording and classification of ocular signals to control a wheelchair for Parkinson disease patients. Additionally, a similar platform enables us to record contrasting eye vergence motions with a virtual reality headset for home-based visual therapy due the sensor’s small form factor. In this thesis, a set of materials, mechanics, and system integration methods is presented and discussed to unite preemptive and therapeutic care for comfortable recordings using electrooculograms and wearable devices.Ph.D