In the multi-load wireless power transfer (WPT) system, the output power and transfer efficiency will drop significantly with the change of distance between transmitter and receiver. Power distribution among multiple loads is also a major challenge. In order to solve these problems, a novel multi-load WPT system based on parity−time symmetry (PT-WPT) is proposed in this paper. Firstly, the multi-load PT-WPT system is modeled based on the circuit model. Then, the transmission characteristics of the multi-load PT-WPT system are analyzed. It is found that constant output power with constant transfer efficiency can be maintained against the variation of coupling coefficient, and the power distribution relationship among loads is only related to the coupling coefficient. Further, power distribution under different coupling situations is analyzed in detail to meet different power demands. Finally, taking a dual-load PT-WPT system as an example, the system parameters are designed and the circ... [more]

This paper presents the electromagnetic and thermal characteristics of a permanent magnet synchronous motor (PMSM) in a joint actuator which is used for articulated robot application. In an attempt to design a compact PMSM for the articulated robot, robot link should be taken into consideration during the motor design process as it can reduce the temperature distribution on motor, thus reducing the volume of the motor. A lumped-parameter thermal model of PMSM with and without a link is proposed considering the core loss, copper loss, and mechanical loss as heat sources. The electromagnetic and thermal analysis results are well confirmed by the experiment in a 400 W 20-pole/24-slot PMSM. The experiment results show that the robot link helps to reduce the motor end-winding temperature by about 40%, and this leads to an increase in power density of the motor.

Due to environmental issues and depletion of resources, global attentiveness in electric vehicles (EVs) is growing. In particular, research on high specification motors for driving large EVs has attracted a lot of attention. In this study, an analysis and design process for a motor that can be universally applied in heavy vehicles to reduce environmental pollution was introduced. Motors for driving heavy vehicles require high specifications. Thus, an interior permanent magnet synchronous motor (IPMSM) with a delta-shaped magnet array was used to improve the torque and power characteristics. A step skew rotor structure was also used to dampen vibration and noise by minimizing the high-order harmonics in the cogging torque. The proposed analysis and design approach also reduces the total harmonic distortion (THD) of the back electromotive force (EMF). The effectiveness of the proposed analysis and design process and the usefulness of the resulting high-performance traction motor for heav... [more]

In the last decade, the interest for higher reliability in several industrial applications has boosted the research activities in multiphase permanent magnet synchronous motors realized by multiple three-phase winding sets. In this study, a mathematical model of an asymmetric surface-mounted six-phase permanent magnet synchronous motor under high resistance connections was developed. By exploiting the intrinsic properties of multiphase machines in terms of degrees of freedom, an improved field-oriented control scheme is presented that allows online fault detection and a quite undisturbed operating condition of the machine under high resistance connections. More specifically, the proposed strategies for online fault-detection and fault-tolerance are based on the use of multi-reference frame current regulators. The feasibility of the proposed approach was theoretically analyzed, then confirmed by numerical simulations. In order to validate experimentally the proposed strategies, the enti... [more]

This paper proposes an energy shaping controller of a DC/DC converter for automatic guided vehicles (AGVs) wireless power transfer (WPT). A transformer is inserted after the LCC topology to improve the transfer power, and the DC/DC boost converter is added before this topology to obtain desired systematic power dynamically. The system power transfer model is derived based on the idea of voltage transformation and the desired power can be implemented indirectly through regulating desired output voltage of DC/DC converter. With the proposed controller, this WPT system will have a much better dynamic performance and the effective working time can be increased significantly. Furthermore, this paper proposes dynamical regulation strategy for output power to get real time target power according to the charging curve of the battery. Simulation and experimental results verified the control performance of the proposed control scheme. A WPT prototype with power up to 1.65 kW was built, and 92.12... [more]

This paper proposes a three-phase metaheuristic-based approach for induction machine bearing failure detection and diagnosis. It consists of extracting and processing different failure types features to set up a knowledge base, which contains different failure types. The first phase consists in pre-processing the measured signals by aggregating them and preparing the data in exploitable formats for the clustering. The second phase ensures the induction machine operating mode diagnosis. A measured signals clustering is performed to build classes where each one represents a health state. A variable neighborhood search (VNS) metaheuristic is designed for data clustering. Moreover, VNS is hybridized with a classical mechanics-inspired optimization (CMO) metaheuristic to balance global exploration and local exploitation during the evolutionary process. The third phase consists of two-step failure detection, setting up a knowledge base containing different failure types, and defining a repre... [more]

This study presents, experimentally, similarity and Froude number similitude (FNS) in the dimensionless features of two solitary waves propagating over a horizontal bed, using two wave gauges and a high-speed particle image velocimetry (HSPIV). The two waves have distinct wave heights H0 (2.9 and 5.8 cm) and still water depths h0 (8.0 and 16.0 cm) but identical H0/h0 (0.363). Together with the geometric features of free surface elevation and wavelength, the kinematic characteristics of horizontal and vertical velocities, as well as wave celerity, are elucidated. Illustration of the hydrodynamic features of local and convective accelerations are also made in this study. Both similarity and FNS hold true for the dimensionless free surface elevation (FSE), wavelength and celerity, horizontal and vertical velocities, and local and convective accelerations in the horizontal and vertical directions. The similarities and FNSs indicate that gravity dominates and governs the wave kinematics and... [more]

With ever-increasing concerns on health and environmental safety, there is a fast-growing interest in new technologies for medical devices and applications. Particularly, wireless power transfer (WPT) technology provides reliable and convenient power charging for implant medical devices without additional surgery. For those WPT medical systems, the width of the human body restricts the charging distance, while the specific absorption rate (SAR) standard limits the intensity of the electromagnetic field. In order to develop a high-efficient charging strategy for medical implants, the key factors of transmission distance, coil structure, resonant frequency, etc. are paid special attention. In this paper, a comprehensive overview of near-field WPT technologies in medical devices is presented and discussed. Also, future development is discussed for the prediction of different devices when embedded in various locations of the human body. Moreover, the key issues including power transfer eff... [more]

Sensorless control of electrical drives is still a difficult task, especially in the lower speed region. Moreover, when the machine has a low saliency such as in the case of Surface Mounted Permanent Magnet Synchronous Motor (SMPMSM), high frequency injection techniques are even more challenging. In this paper, an enhanced demodulation algorithm for the sensorless control of a SMPMSM is proposed. The new scheme uses the high frequency injection in the Synchronous Reference Frame (SRF) and employs also the negative sequence content of the measured current for improved accuracy. This allows an improved performance with a lower amplitude of the injected signal, thus reducing the noise and additional losses in the motor. It is found that, by using both components with the algorithm developed the estimation ripple can be greatly reduced and the system can operate properly with a voltage injection of only 2.17% of the rated motor voltage, which is lower than most found in the literature, spe... [more]

A position observer and a predictive controller for sensorless synchronous-reluctance-motor (SynRM) drive systems are investigated in this paper. The rotor position observer, based on motor parameters, and stator currents and voltages, was designed and implemented to compute the rotor position. A pole-assignment technique was used to provide similar converging rates of the position observer, even when operated at different speeds. Furthermore, a predictive controller was designed to enhance performance. A digital-signal processor (DSP), TMS-320F-28335, was used as a computation tool. Several simulated results are provided and compared with the measured results. The measured results showed that the implemented predictive controller sensorless SynRM drive system could be adjusted from 30 to 1800 rpm with satisfactory performance, including quicker and better tracking responses, and a lower speed drop than that of a proportional-integral (PI) controller.

Multiphase drives are entering the spotlight of the research community for transportation applications with their high power density and the possibility of high fault tolerance. The multi three-phase drive is one of the main types of multiphase drives that allows for the direct adoption of commercial three-phase converters and high control flexibility. The elimination of high-frequency current harmonics will reduce the flux linkage harmonics, torque ripple, vibration and noise in machine drives. Therefore, this work introduces a new method to the modelling of equivalent phase current in multi three-phase drives with the double integral Fourier analysis method. A new carrier-based pulse-width modulation (CPWM) method is introduced to reduce the equivalent phase current harmonics by applying proper carrier phase angle to each subsystem in the multi three-phase drives. The proposed angles of carrier signals are analyzed for quadruple three-phase drives, and the corresponding experimental... [more]

Due to the massive congestion in ground transportation in Beijing, underground rail transit has gradually become the main mode of travel for residents of large urban areas. Because the average daily traffic of the Beijing subway is over 12 million passengers, ensuring the safety of underground rail transit is particularly important. Big data shows that more than 4000 passengers participate in Long-term Stay in the Subway every day. However, the behaviors of these passengers have not been characterized. This paper proposes a method for identifying the Long-term Staying in Subway System (LSSS) in the subway based on the shortest path and analyze its travel mode. In combination with the past research of scholars, we try to quantify the suspected behavior with a database of assumed suspected behavior records. Finally, we extract the spatial-temporal travel characteristics of passengers and we propose a SAE-DNN algorithm to identify suspected anomalies; the accuracy of the training set can... [more]

Recently, the construction of external ventilated walls has become popular for public and office buildings. These blocks are used without internal rendering because of their good interior surface, stable dimensions and various filling of masonry joints, which provide an attractive architectural appearance. However, problems with the airtightness of such walls often occur. Currently, there are no standard methods to predict the airtightness of such wall. In practice, samples of particular walls are produced, and their air permeability is measured at laboratories. For the broader use of the results of laboratory air permeability measurements, a methodology has been developed to predict the air permeability of block masonry walls using experimentally determined air flow resistances of the individual layers. The masonry from various blocks were used for the research; mineral wool boards of various air permeability were used for thermal insulation and the wind protection layer. After measur... [more]

This work applies the Second-Order Adjoint Sensitivity Analysis Methodology (2nd-ASAM) to compute the mixed 2nd-order sensitivities of a polyethylene-reflected plutonium (PERP) benchmark’s leakage response with respect to the benchmark’s imprecisely known isotopic number densities and the other benchmark imprecisely known parameters, including: (i) the 6 × 180 mixed 2nd-order sensitivities involving the total microscopic cross sections; (ii) the 6 × 21,600 mixed 2nd-order sensitivities involving the scattering microscopic cross sections; (iii) the 6 × 60 mixed 2nd-order sensitivities involving the fission microscopic cross sections; and (iv) the 6 × 60 mixed 2nd-order sensitivities involving the average number of neutrons produced per fission. It is shown that many of these mixed 2nd-order sensitivities involving the isotopic number densities have very large values. Most of the large sensitivities involve the isotopic number density of 239Pu, and the microscopic total, scattering or fi... [more]

Thermodynamics is a discipline, with unambiguous concepts, words, laws and usefulness. Today it is in danger of becoming a Tower of Babel. Its key words are being pasted brazenly on new concepts, to promote them with no respect for their proper meaning. In this brief Perspective, I outline a few steps to correct our difficult situation.

Conductive particles are one of the most important defects which can greatly degrade the performance of gas-insulated metal-enclosed switchgear (GIS). Many efforts have been made to clarify the influence on the withstand voltage, understand the flashover mechanism, and build a comprehensive model to describe the particle-initiated flashover. In this study, a partial discharge (PD) signal detected through a photomultiplier (PMT) and recorded by a high-speed data acquisition (DAQ) system was used to analyze the discharge development of a conductive particle-contaminated GIS insulator under constant high AC voltage. An additional PMT was used as a reference to eliminate the dark count of the PMT and the data collection method of a DAQ system was optimized to capture the pulse waveform of each PD to obtain detailed physical information. Spectra of the PD pulse amplitude over pulse width, PD counts within various amplitude ranges over time and phase resolved partial discharge (PRPD) pattern... [more]

Recently, as OLED displays are widely used in smartphones, their power management has become an important issue. Since OLED display devices show a large difference in power consumption depending on the colors used, proper color selection is important to reduce power consumption, but this may affect quality-of-experience (QoE) perceived by users. To address this tradeoff, this paper proposes a new power management scheme for graphical-user-interface (GUI) applications in OLED-based mobile devices. First, we examine the relationship between power consumption and color usage based on actual measurements and derive a model to express color preferences. Next, we present a dynamic programming algorithm that adaptively changes the color of the GUI objects in the applications to limit the total power consumption while effectively reflecting the color preferences of the user. The proposed scheme was implemented on a commercial smartphone, and real power measurements were conducted to examine wh... [more]

In this article, a Quasi Z-source inverter (QZSI)-based unified power quality conditioner (UPQC) backed by the solar photovoltaic (SPV) is presented in order to enhance power quality. The UPQC consists of converters connected in parallel and series. The active power filters (APFs) connected in parallel and series is one of the versatile custom power circuitries to reduce current and voltage instabilities. The main functions of QZSI can increase the variable direct current (DC) voltage to any given alternating current (AC) output voltage, reduce the necessary elements, and alleviate harmonic content. The UPQC’s compensation function primarily relies on the control system used for the generation of reference current and voltage. The enhanced second order generalized integrator (ESOGI) is used in this proposed system to extract the reference current of QZSI-UPQC. The proposed UPQC uses the SPV system, which has an energy storage unit to offset long-term current and voltage disruptions and... [more]

This article presents a method for analysis of the low-power periodic Wireless Power Transfer (WPT) system, using field and circuit models. A three-dimensional numerical model of multi-segment charging system, with periodic boundary conditions and current sheet approximation was solved by using the finite element method (FEM) and discussed. An equivalent circuit model of periodic WPT system was proposed, and required lumped parameters were obtained, utilizing analytical formulae. Mathematical formulations were complemented by analysis of some geometrical variants, where transmitting and receiving coils with different sizes and numbers of turns were considered. The results indicated that the proposed circuit model was able to achieve similar accuracy as the numerical model. However, the complexity of model and analysis were significantly reduced.

Wireless inductive-coupled power transfer and opportunity battery charging are very appealing techniques in drone applications. Weight and size are very critical constraints in drones, so the battery and the on-board electronics must be as light and small as possible. The on-board components involved in the resonant inductive-coupled wireless power transfer usually consist of the secondary coil, the compensation capacitor, the bridge rectifier, the LC-filter and the battery. This paper suggests a sizing of the LC-filter capacitor that improves the charging power of the battery. In addition, further on-board space and size is saved by using the stray inductance of the battery as filtering inductor. LTSpice simulations and experimental tests carried out on the prototype of a wireless power transfer circuit shows the dependency of the power delivered to the battery on the filter capacitor size. Finally, it is found that the power transfer to the battery is maximized by choosing the capaci... [more]

An active coil system is proposed to shield the magnetic field produced by a dynamic wireless power transfer (WPT) system used to power electric vehicles (EVs) in motion. The considered dynamic WPT is based on an electrified road with many short-track pads. A sophisticated mathematical procedure is developed to optimize the design of the active coils configuration and their excitation. By the proposed approach, the resulting magnetic field is compliant with the reference levels (RLs) of the ICNIRP (International Commission on Non-Ionizing Radiation Protection) 2010 Guidelines inside the cabin of EVs and on the side of the electrified road.

A high-performance 20 kW, 20 Nm, 8000 rpm, spoke-type interior permanent magnet motor to be integrated into a FormulaStudent electric car’s powertrain has been designed to meet demanding performance requirements for its driving cycle. This paper describes key steps in the design optimization, analysis, fabrication, and testing of this machine. Design optimization used the non-dominated sorting genetic algorithm II (NSGA-II) coupled with a hybrid analytical/finite element model to reduce the computational time, achieving a torque and efficiency of 20 Nm and 98.6%, respectively. A prototype has been constructed. The final motor design has been tested, where experimental nominal torque and efficiency have reached 18.2 Nm and 90%, respectively. Design challenges regarding the manufacturing are presented, justified, and discussed in detail. Test results were conducted to evaluate reliability and motor temperatures with and without water refrigeration at nominal current. Despite those adjust... [more]

Exploration of chemical space around hit, experimental, and known active compounds is an important step in the early stages of drug discovery. In academia, where access to chemical synthesis efforts is restricted in comparison to the pharma-industry, hits from primary screens are typically followed up through purchase and testing of similar compounds, before further funding is sought to begin medicinal chemistry efforts. Rapid exploration of druglike similars and structure−activity relationship profiles can be achieved through our new webservice SimilarityLab. In addition to searching for commercially available molecules similar to a query compound, SimilarityLab also enables the search of compounds with recorded activities, generating consensus counts of activities, which enables target and off-target prediction. In contrast to other online offerings utilizing the USRCAT similarity measure, SimilarityLab’s set of commercially available small molecules is consistently updated, currentl... [more]

A voltage stability index is proposed using a new single-port equivalent depending on component peculiarity representation and sensitivity persistence to locate and determine long-term voltage instability in transmission and distribution power networks. The suggested single-port equivalent effectively represents the equivalence of various component types and assures the consistency of sensitivity information before and after the equivalence which is compulsory for the equivalent accuracy in estimating the voltage stability analysis. The stability index is derived from the new single-port equivalent to determine the system voltage instability. The proposed stability index is compared with indices based on virtual impedance and Thevenin impedance models. This new stability index shows more accuracy and effectiveness as compared to the indices based on virtual and Thevenin equivalent models. The index also determines the weak buses, where an improvement or functional measure can be used t... [more]

The process of upsetting, with rotating dies, is used to reduce the force required to deform the workpiece and to receive more homogeneous deformation compared to the same process without the rotational motion of the dies. The upper bound method is an efficient tool for a quick estimate of process parameters. The accuracy of upper bound solutions depends on the chosen class of kinematically admissible velocity fields. The present paper provides an efficient method for choosing kinematically admissible velocity fields that satisfy some stress boundary conditions if the associated flow rule is considered. The method applies to the upsetting of cylinders. It is expected that it leads to accurate solutions if friction is high enough. Besides, the kinematically admissible velocity field accounts for a rigid region near the axis of symmetry. Such a region inevitably occurs in exact solutions because the friction stress must vanish at the axis of symmetry. The final expression for the upper b... [more]