Miracle-dz/UniFAR-FTUs huggingface dataset:
Design and Experimental Study of a GaN-based Three-Port Multilevel Inverter

A three-port multilevel inverter with two DC ports and an AC port using Flying Capacitor Multilevel (FCML) design based on Gallium Nitride (GaN) switches is proposed in this paper. Recently, FCML inverter has shown a superior ability for power conversion with high power density, improved Total Harmonic Distortion (THD), and efficiency. The presented three-port multilevel inverter fits various applications such as battery and photovoltaic (PV) grid integration and standalone AC load. The proposed inverter is experimentally verified by building a 3-kW prototype using GaN switches which include two 4-level FCML converter paths, each share the same bus capacitor (Cbus), which links them together. One FCML path is 1 kW that incorporates an unfolder for the DC-to-AC conversion and has achieved a peak efficiency of 98.2% with AC voltage and current THDs of 1.26% and 1.23%, respectively. While the second FCML converter path is 2 kW used for the DC-to-DC conversion and has achieved a 99.43% peak efficiency.
A Novel Method for Calculating the Three-phase Unbalanced Shunt Compensation Current in the Low Voltage Distribution Network

In order to compensate unbalanced and non-linear loads of the low-voltage distribution network into the symmetric and pure resistive loads, a novel method is proposed, where the compensation current calculation is performed based on the instantaneous voltage space vector orientation. The proposed method is capable of making the waveform and phase of the compensated current consistent with those of the grid voltage, so as to achieve the minimum instantaneous reactive power consumption under the asymmetric and distorted background of the grid. It is found that this method has considerable advantages, including the low computational expense, adaptive phase sequence and the automatic frequency following, over the conventional methods. The accuracy and effectiveness of the proposed method are verified through simulation and experiments. It is concluded that the proposed method is an accurate and effective method for shunt comprehensive compensation in the low voltage distribution network.
Intermodulation suppression in slow shear TeO2 Bragg cells using a phased array transducer

A technique for the measurement of acousto-optic intermodulation products and the the improved dynamic range performance of a Gaussian weighted phased array slow shear Te02 50 MHz bandwidth Bragg cell are reported. The intermodulation products caused by the nonlinear acousto-optic interaction dominated over those caused by the elastic nonlinearity for most of the 50 μs cell length except near the end. This represents an improvement over the conventional transducer design where the nonlinear elastically generated intermodulation products dominate and limit the device dynamic range. The interferometric measurement system had over 50 dB of dynamic range and could easily display all of the two tone intermodulafion products with a standard RF spectrum analyzer.
Development of Wood-Based Composites Material for 3D Printing Process

This paper presents the development of wood-based composites material for 3D Printing process. The aim is to characterize the waste material from wood powder (WD) as an alternative material and low cost production for rapid prototyping product. The powder blends containing wood powder (90-120µm) with commercial ZP102 material from Z Corporation was used as the composite material. The materials were mechanically blended to produce composition of WD/ZP102(vol.%) 25:70, 50:50 and 75:25 respectively. The material was successfully processed on 3D printers machine, to produce three-dimensional components and followed by post-treatment with ZMax solution to enhance the mechanical properties. The mechanical properties, dimensional accuracy and surface quality of the components were evaluated and the results were compared with the standard ZP102 material. The result shows that the mechanical properties improved with the increased of wood powder content up to 50 (vol.%). However, dimensional accuracy and surface quality were decreased as the wood content increased. Further work on powder preparation is continued for surface quality improvement.
A Study on Small Signal Stability of the Large-Scale Wind Farm with DFIGs

The high penetration of doubly-fed induction generators (DFIGs) entails a change in dynamics and operational characteristics of the power system, thus this paper investigates the small signal stability of the large-scale wind farm with DFIGs. The GE 1.5MW DFIG is modeled in power system analysis software package (PSASP), and a large-scale wind farm with DFIGs is established. Then, the two-area test system with four generators is applied to assess the effect of the large wind farm on power system inter-area oscillatory mode in which the penetration and the installation site of the wind farm are considered. Finally, the simulation results indicate that abundant penetration of DFIG-based wind power will improve the inter-area oscillatory, and the integration of wind farms with DFIGs in the receiving area makes the inter-area mode highly damped.
Exploratory Analysis of Spatial Hierarchical Clustering in Los Angeles County, California: Relationship of Opportunity-Based Accessibility, Reported Land Values, and Resident Characteristics

The phenomenon of agglomeration has long been recognized as an important component in businesses and their location decisions. A similar phenomenon may also exist in resident location of the population in an urban area. This concept may also emerge from residential segregation and ethnic enclaves. Residential segregation may be influenced by location characteristics, social composition, and accessibility. This paper uses spatial clustering indicators that comprise resident population and its characteristics, infrastructure provision, activity opportunities by opportunity type, housing supply, and synoptic measures of travel. Time of day is introduced as a fundamental unit in classifying the spatial units. Classification of spatial units is accomplished first with a cluster technique that accounts for spatial dependence in opportunity-based accessibility indicators for different variables considered individually. Normalized scores for each variable and all spatial units are then used to derive a second set of clusters using multiple variables to build a group of clusters of spatial units. The characteristics of the residents in each spatial unit are examined for the Los Angeles County region of California with a sample of approximately 6,000 geolocated households with corresponding data on their residences along with detailed location characteristics. Residents of these clusters share similarity in their characteristics, and this analysis provides an example not only of a new way to use spatial clustering to understand location choices of households but also a way to alleviate the problem of dimensionality in choice set identification.
Integrated asynchronous high-voltage DC-DC buck converter for energy harvesting applications

Reported is a high-voltage DC–DC buck converter to interface energy harvesters in ultra-low-power wireless sensing applications. A measured efficiency between 61 and 91% has been obtained for input power between 10 and 1000 µW and for a large input voltage range between 5 and 60 V. To minimise the power consumption of the control circuits, an asynchronous implementation was used with a zero static power high-voltage level shifter and a widely applicable ultra-low-power n-switch control circuit architecture.
Development of SiC heterojunction power devices

Silicon carbide (SiC), with its wide bandgap, high thermal conductivity and natural oxide is a substrate that has given rise to a new generation of power devices than can operate at high temperature, high power and high frequency, though the material is not without its problems. SiC "heterojunction devices" are layers of germanium (Ge) or silicon (Si) that are deposited via molecular beam epitaxy (MBE) or wafer bonded onto the SiC surface. These narrow bandgap thin films can provide a high mobility channel region overcoming SiC's crippling channel mobility, which is most often made worse by a high density of interface states. Concentrating predominantly on Ge/SiC heterojunctions, this thesis characterises the physical and electrical nature of these structures, investigating the rectifying properties of the heterojunction interface and the ability of these layers to support a depletion region. A physical analysis of the layers revealed that the Ge formed in an unexpectedly uniform fashion, given the large lattice mismatch involved. At a deposition temperature of 500oC the Ge initially clumped into wide, shallow islands before merging, forming at best a 300 nm polycrystalline layer with a surface roughness of only 6 nm. This was in contrast to MBE deposited Si/SiC layers that formed tall islands that at 1 μm thick, still had not merged. After being formed into Ge/SiC heterojunction diodes they were electrically characterised. The layers displayed near ideal (η = 1:05) turn-on characteristics, low turn-on voltage (approximately 0.3 V less than Ni/SiC SBDs), reasonable on-resistance (12 m­Ωcm2) and minimal leakage current. The devices were shown to suffer severe Fermi level pinning that defined the way the materials' bands aligned. This occurred as a result of an inhomogeneous interface that also caused fluctuations in the size of the Schottky barrier height across the interface. New characterisation techniques relating to these phenomena were applied to a heterojunction for the first time. MBE formed Ge/SiC layers and wafer bonded Si/SiC layers were formed into MOS capacitors through the deposition of the high-K dielectric hafnium oxide (HfO2). The increased conduction band offset between oxide and narrow bandgap semiconductor suppressed leakage problems often seen in HfO2/SiC structures. Capacitance-voltage results showed that they could both support a depletion region, though the best results came from the MBE Ge/SiC diodes. Current-voltage results showed that the more uniform Si/SiC devices could block 3.5 MV/cm.
A Comparative Study of Energy Storage Systems based on Modular Multilevel Converters

With the rapid increase of renewable sources connected to the grid, a viable solution to ensure its stability is by deploying distributed Energy Storage Systems (ESS) along the grid. ESS should be capable of managing high-power ratings in short periods of time, thus supercapacitors (SCs) are attractive candidates to fulfill this requirement. ESS topologies based on the Modular Multilevel Converters (MMC) are both expandable and scalable in a manner that avoids the complexity of current systems. In this paper, we present a comparative study of multiple ESS through numerical simulations together with an application optimization for different scenarios.
Analyses and Design of a High Power Bidirectional 48V-12V DCDC Converter System for Electric Vehicle Application

This paper proposes the theoretical analyses, design method, design process and design results of a high power bidirectional 48V-12V DCDC converter system in electric vehicle (EV) application. The design is divided into 3 levels that are topology level, control method level, and block level based on IC with 3 steps respectively. In topology level, full-bridge CLLC is chosen for its high efficiency and good stability. 8 stages are designed for full-bridge CLLC in one switching period. Topology design mainly focuses on determining resonant components by inherent frequency and quality factor. In control method level, FPD (Frequency, Phase shift, and Duty) influence the performance of the whole system in their own way and FPD control method is chosen for this system. In block level, a main control loop that consists of 3 interlaced loops is illustrated by functional blocks and achieved actually by IC design. The whole design is verified by analog IC simulation whose results confirm the basic function and expected performance of the system. The output voltage accuracy enters 0.1% range and efficiency is up to 99.15% in buck mode with full load. The performances of the converter system in other conditions are also competitive.
E-Teaching High Accuracy Motion Control Techniques in Covid–19 time

High accuracy motion control is a subtle subject, and many critical aspects are related to the non-idealities of both the actuators and the mechanical device to be moved. Based on the multi-year experience gained in a hands-on laboratory, involving tens of Mechatronics’ master students at the University of Padova, it has been possible to set up (in a Matlab/Simulink environment) a realistic simulator of a servo positioner, accounting for most of the characteristics of an actual system. The typical laboratory experience starts with the identification of the relevant physical parameters of the system to be controlled (each student receives a different encrypted model of the system to be controlled), followed by the design of controllers and disturbance observers in a deterministic setting. Then, a stochastic approach is applied, with the design and experimental tuning of a Kalman filter. To improve the tracking and disturbance rejection of the controlled system, it is also studied the application of advanced techniques like Repetitive Control, Zero-Phase Tracking Error Control, Iterative Learning Control. As a result, it has been possible to get the full involvement of each student even in Covid-19 time, with results that closely matched those obtained in the previous hands-on experience.
Asynchronous Hybrid Deep Learning (AHDL): A Deep Learning Based Resource Mapping in DVFS Enabled Mobile MPSoCs

Mapping resources to tasks accurately in order to gain performance, energy efficiency, reduction in peak temperature, etc. on an embedded/Edge device is a big challenge. Machine learning has proven to be effective in learning heuristics based resource mapping approaches, but its success is bound by the quality of feature extraction. Additionally, feature extraction in such approaches not just requires expert domain knowledge and human effort, but at the same time requires the application (tasks) to be profiled for such processes. Therefore, the efficacy of such resource mapping methodologies depends on expertise, skills, profiling time and architecture of the system. In this paper, we propose a novel methodology, Asynchronous Hybrid Deep Learning (AHDL), which sets a new paradigm of using Deep Learning approaches to map resources to application (tasks). In our approach, we leverage task profiling methodologies to achieve accurate mapping in order to achieve greater reward from the system, but at the same time is able to allocate resources to unprofiled application (tasks) at the same time without the need of manual feature extraction by domain experts. Our proposed methodology is able to achieve competitive results in comparison with the state-of- the-art without the usual associated challenges such as manual feature extraction.
Co-Simulation of Two-Wheel Differential Spherical Robot Based on ADAMS and MATLAB

This paper proposes a novel approach for two-wheel differential spherical robot (TWDSR) design to monitor the power cable tunnel environment. A co-simulation of dynamic modeling and controller design is conducted based on ADAMS (Automatic Dynamic Analysis of Mechanical System) and MATLAB platforms, respectively. The combined simulation takes the advantages of dynamic modeling for complicated mechanical structure of ADAMS and various controller designs of MATLAB. We established the virtual prototype model of TWDSR composed of spherical shell, cart and driving wheels in ADAMS. The rectilinear motion and steering motion are modeled by loading different inputs on the driving wheel. Based on results of the model, we analyzed the basic open-loop motion control characteristics of TWDSR. Subsequently, the ADAMS virtual prototype model is imported into MATLAB to design the velocity controller by Simulink module. The co-simulation results demonstrate that the designed mechanism of TWDSR is suitable for power cable tunnel monitoring. The motion control simulation determines the parameter values of PI controller and evaluates the system motion performance. The co-simulation of TWDSR provides detailed references for the development and implementation of the physical prototype in the future.
Design of fault-tolerant cruise control in a hierarchical framework for connected automated vehicles

This paper presents a design method for the cruise control of connected automated vehicles. The proposed control system contains layers with different functionalities, which are interconnected in a hierarchical structure. The reason for using layers is to separate the functionalities which require different computation efforts. The layer on the high level computes a reference speed signal for the vehicle, which considers the economy and time performance requirements. It requires the solution of a complex optimization problem, which is performed in a cloud with low frequency. There are two further layers on the level of the vehicle, such as the signal analysis and the local control layers. The purpose of the signal analysis layer is to examine the feasibility of the reference speed regarding vehicle safety performances. This layer is designed to require low computation effort and on-board sensor measurements, thus analysis can be performed with high frequency. The proposed hierarchical cruise control is able to handle the priorities between the various performance requirements, thus safe motion of the vehicle is guaranteed under every circumstances.
Wind Energy Conversion System using a Squirrel Cage Induction Generator Coupled to the Network with a Predictive DPC

This paper presents the modeling of a Wind Energy Conversion System (WECS) using a self-excited induction generator (SEIG) coupled to the grid with a predictive Direct Power Controller (DPC), applying an optimal space vector selection technique. The self-excitation of the induction generator is obtained with a Direct Torque Controller (DTC) which allows controlling the machine's space vector flux and electric torque. On the other hand, the power system coupling is with a Direct Power Controller (DPC), that selects the voltage space vectors required to minimize the active and reactive power errors to the reference. The advantage of the optimum DPC scheme proposed in this work is the fast adjustment of the active and reactive powers to the references, compared with speed obtained using the inverter's PLL synchronization method.
Novel Isolated Multiple-Input Buck-Boost DC-DC Converter for Renewable Energy Sources

An isolated multiple input dc-dc converter (MIC) with unidirectional buck-boost characteristics and simultaneous power transfer is proposed for multi-sources in renewable energy systems in this paper. When compared to existing isolated MICs, the proposed MIC significantly reduces the component count and control complexity since it requires a fixed coupled inductor with only one primary and secondary winding each for any number of inputs and does not require any phase-shifted pulse-width modulation. The operation of the proposed converter for simultaneous power transfer from multiple sources with varying voltages is numerically verified in simulation and validated on OPAL-RT’s OP5700 hardware-in-the-loop (HIL) validation platform.
Design and Experimental Assessment of a 60 kW All-Si Three-Phase Six-Leg T-Type Rectifier for Electric Vehicle Ultra-Fast Charging

This paper presents a complete design methodology for a 60 kW AC/DC active rectifier stage of a modular electric vehicle ultra-fast battery charger. Due to the well known performance of three-level unidirectional rectifiers, a T-type converter topology is selected. Moreover, in view of the high target nominal power of the converter, a six-leg approach is adopted, thus halving the current rating of each bridge-leg and allowing for the adoption of conventional discrete semiconductor devices (i.e., Si MOSFETs and Si diodes). Therefore, a step-by-step design procedure is proposed, based on the selection, sizing and/or optimization of all main converter active and passive components, including the semiconductor devices, the DC-side capacitors, the AC-side inductors and the loss dissipation system (i.e., heatsink and fans). Finally, a 60 kW converter prototype is realized and its performance is experimentally assessed.
Octree-based Virtual Dental Training System with a Haptic Device

AbstractThe virtual dental training system using a haptic device is becoming a very important training tool for dental education. We propose a new approach that utilizes the so-called EP (Edge Proportion) value, local material stiffness and implicit function to develop a novel dental training system which has useful characteristics such as efficient collision detection, stable haptic interaction and accurate sculpting simulation. In the efficient collision detection approach, the oriented bounding box tree and EP value can be quickly updated for collision detection. The EP value is very important in our approach, because it can also be used to compute haptic force and update the tooth model. In the stable haptic interaction approach, we use the spring-damper force model and a simple force filter to obtain stable force feedback. Finally, in the precision sculpting simulation, an implicit function is employed to exactly represent various kinds of dental tools so that accurate calculation of cutter- surface .
Speed Limits for Single-Beam Laser Marking

Laser Marking is a very common part of many manufacturing processes usually performed at the last stages of production lines after the packaging of goods. The speed of production lines are key determinants of the output capacity of many industries, but their scalability could be hindered by some fundamental limits of current laser marking technologies. In this paper, we review related technologies, their limiting factors, and analyze how future systems could overcome them.
Torsional Electromagnetic Vibrational Energy Harvester Based on Stacked Flexible Coils

In this work, we report on an electromagnetic vibrational energy harvester (EVEH), based on the torsional movement of a permanent magnet over a stack of flexible planar coils. The disc magnet is glued to a silicon plate suspended by straight torsional springs. With a size of 1 cm×1 cm×1.08 cm, the proposed EVEH is capable of generating an open-circuit peak-to-peak voltage of 138.9 mV and a power of 4.6 μW, under a sinusoidal excitation of ±0.5g and frequency of 104 Hz. At elevated acceleration levels, the maximum peak-to-peak output voltage is 185.2 mV under the acceleration of 7g (±3.5g).
Servo Actuators with Induction Motor using Predictive Current Control with Duty Cycle Optimization

This paper proposes a controlling method for servo actuators of a three-phase induction motor (IM), using the finite control-set model predictive current control (FCS-MPCC). The IM is modelled using the indirect field-oriented control technique (IFOC), having the rotor flux as a reference for vector orientation. The control of the rotor shaft position from the IM, as well as the speed and magnetizing current controllers are performed using proportional-integral (PI) controllers. In addition, enhancement of control techniques using M2PCC and M³PCC are designed in order to minimize high ripples in the control variables, which means a reduction of the harmonics in at output of the converter. Simulation results are shown presenting high dynamic performance.