In this paper, different designs and controls of several wireless power transfer (WPT) topologies are comprehensively studied for battery charging. Most WPT topologies exhibit inherent constant voltage (CV) or constant current (CC) output characteristics. The paper systematically studies numerous WPT topologies to find these natural CC or CV characteristics. The battery requires combined CC and CV charging, which requires additional control, such as primary, secondary, and dual-side control. Different closed-loop control schemes are meticulously studied, reporting their merits and demerits, further delving into several works that attempted to combine two different WPT topologies using a switchable network to achieve a natural CC/CV charging without additional closed-loop control. This work also focuses on different WPT topologies exhibiting two or more resonant frequencies that achieve the CC and CV charging profile at two distinct frequencies. In addition, the growing popularity of the CP charging profile, which is known for its faster charging capability and compact thermal design, is explored. A sensitivity analysis compares the performances and robustness of the natural CC or CV characteristics of the different topologies when the WPT coil and compensation circuit parameters have a ±10% tolerance.

This paper describes a three-dimensional structure for an adjustable field magnetization permanent magnet (PM) motor. It also presents a high-power-density rotor structure with an asymmetric permanent magnet arrangement for achieving both high torque and high efficiency in the high-speed, low-torque range. 3D-FEA demonstrated that adjustable field magnetization operation is possible without sacrificing high torque density. Furthermore, load testing confirmed that high efficiency characteristics can be realized during high-speed operation.

This paper introduces the bidirectional functionality of a flyback converter achieved using a soft-switching technique. The proposed method can harness electrical energy more efficiently than conventional circuits, which are restricted to unidirectional power supplies. We focused on the flyback converter circuit, which uniquely integrates soft-switching and bidirectional operation, thus facilitating superior power conversion. Specifically, we assessed the power conversion efficiency of the assembled circuit during the boost and buck operations at a switching frequency of 1MHz. The empirical results demonstrated that the power conversion efficiency was 83.2% in boost operation and 81.9% in buck operation. Furthermore, we successfully implemented bidirectional operation by simply adjusting the duty cycle and phase of the switching devices.

We explored the efficacy of a myoelectric-driven rehabilitation robot in enhancing upper limb motor function among patients with post-stroke hemiplegia, focusing on the potential of targeted muscle activity during reaching. Four individuals with chronic stroke underwent a training regimen involving reaching movements in eight directions, utilizing a robot that activates specific muscle activity patterns pertinent to the reaching direction. The training spanned 1-2 months, comprising 8 sessions, with each session consisting of 3 sets of 10 reaching motions in each direction. The training effectiveness was evaluated using four indices: normalized integrated electromyogram (IEMG), number of velocity peaks, movement time, and the Fugl-Meyer Assessment (FMA). Three of four participants demonstrated significant improvements in muscle activity patterns and kinematic parameters, suggesting a potential enhancement in upper limb motor function. In particular, the training showcased promising outcomes for patients with moderate-to-severe chronic stroke hemiplegia both by activating necessary muscles and limiting compensatory movements. However, the effectiveness was not universally applicable, since one participant evidenced no appreciable improvements. This preliminary study highlights the potential of myoelectric-driven robots in rehabilitation. It sets the stage for future research to validate and further optimize this methodology for patients with stroke and motor function impairment.

This study focuses on the voltage-integral trajectory of a low-switching-frequency motor drive and proposes a method for optimizing switching patterns. The voltage-integral trajectory is computed to minimize the inverter switching frequency. The optimal solution is uniquely determined by all-switching-patterns search. The optimized trajectory has significant performance advantages under steady-state conditions. Additionally, by integrating it into direct torque control as an application of closed-loop control, high-speed response and superior steady-state characteristics can be achieved. To highlight the effectiveness of the proposed strategy, the performance is evaluated experimentally using a system consisting of an induction machine and a two-level three-phase inverter.

This paper presents a rotor winding configuration aimed at filtering space harmonics in the rotating magnetic field (RMF), resulting from stator fractional-slot concentrated winding (FSCW) configurations in 12-slot 10-pole induction motors. The design comprises multiphase full-pitch wave windings. The stator FSCW configurations generate a specific harmonic that produces the drive-torque and several other harmonics as the dominant components in the stator RMF. Conventional squirrel-cage winding rotors generate torques derived from all the dominant stator RMF harmonics. This inhibits the production of adequate drive-torque and line-start capability. The proposed wave-winding rotor traps the driving RMF harmonic and completely eliminates the effects of the other dominant RMF harmonics. This filtering effect on the stator RMF harmonics leads to the production of an adequate drive-torque and line-start capability. The efficacy of the proposed rotor winding configuration is determined by theoretically estimating the filtering effect on the stator RMF harmonics, numerically predicting the motor performance through a finite element method analysis, and demonstrating the actual motor performance of a prototype. This research provides insights into the design of IMs with stator FSCW configurations, particularly regarding rotor winding configurations, which has received insufficient attention in previous studies.

In the last decade, the trend in major position-sensorless research on permanent magnet synchronous motor drives has been to improve the performance of sensorless control. In a previous study, we proposed a position estimation method available for the full-speed range with a single Extended-Electromotive Force (EEMF) observer, simplifying the implementation of position-sensorless control. Unfortunately, a certain amount of time must be ensured for polarity determination and initial position estimation with EEMF, which affects the performance of the velocity control at start-up from the standstill state. To improve the EEMF sensorless control performance for the full-speed range, a new position-sensorless start-up method is proposed, to reduce the start-up time. The configuration of the EEMF position-sensorless control system is presented, and the principle of the proposed position-sensorless start-up method is described. The experimental results validate that the proposed method is more effective than the conventional method.

This study improves the previously proposed two-phase pulse width modulation (PWM) scheme with 2-degrees-of-freedom (2-DoF) variable switching pause periods for equalizing device loss in an unbalanced three-phase inverter. This PWM scheme is extended to incorporate 5-degrees-of-freedom (5-DoF) variable switching pause periods, enabling individual loss adjustments for each device. Theoretical and numerical results demonstrate that the proposed 5-DoF PWM scheme effectively equalizes losses for each device in an unbalanced three-phase inverter.

Wide-band-gap switching power devices, such as SiC MOSFETs, are preferred for high-voltage power converters due to their low switching losses compared to Si-based devices. However, their operation with high di/dt and dv/dt during switching exacerbate the issue of electromagnetic interference (EMI), particularly in the high-frequency region. To predict conducted EMI emissions, frequency-domain behavioral models are used. However, they require time-domain measurements on experimental prototypes. In this paper, we present a non-linear model for predicting high-frequency differential-mode conducted emissions (DM-CE) on the input side of a single-phase inverter. The modeling of DM-CE depends on circuit switching transients and the parasitics of the noise propagation path. An empirical non-linear model for SiC MOSFET parasitic capacitance and transfer characteristics is presented. The switching transients of a single-phase inverter were simulated using the proposed SiC MOSFET model and circuit wiring parasitics. DM-CE is calculated from the circuit simulations and compared with experimental observations.

This study developed and tested an inexpensive and accurate system for automating sprint time measurement using a low-cost single-board computer equipped with a microphone and a phototube sensor. The system comprises a program written in Python running on a Raspberry Pi computer. A microphone detects the starter pistol firing and a phototube sensor (Rasp-Pi system) measures the times across the finish line. The Rasp-Pi system's potential error was determined against a commercial unit and the program was corrected. It was then used to measure the 50m running times of 20 subjects. These results showed that the average difference (n =20) between the commercial and Rasp-Pi systems was less than 1/100th of a second. In validation, Pearson's product-moment correlation coefficient and the intraclass correlation coefficient (ICC(2,1)) were both > 0.999, which is exceptionally high. Finally, a Bland-Altman plot confirmed a high degree of agreement between the two systems, thereby validating the Rasp-Pi system's efficacy.

The short cruising distance per charge is a major technical challenge associated with electric vehicles (EVs), compared to hybrid and conventional vehicles with internal combustion engines. Dynamic wireless power transfer (DWPT) is a feasible solution to increase the cruising distance of EVs equipped with small capacity batteries. DWPT eliminates the need to use a large capacity batteries in an EV. This makes EVs lighter and thus reduces the energy required for cruising. Notably, the manufacture of large capacity batteries cause large quantity of greenhouse gas (GHG) emissions. Therefore, DWPT can contribute to reducing GHG emissions. This study estimates the GHG emissions of passenger electric vehicles with the DWPT system, including transmitter coils and inverters, and compares their emissions with those of passenger EV equipped with large capacity batteries. The number of DWPT transmitter coils was estimated by simulation using actual driving data on local roads and expressway gradient data. The comparison results show that DWPT system can reduce 28.9% of GHG emission compared to EV with large capacity batteries.

Wireless power transfer, a technology for transmitting electric power to various devices without physical connection, has been widely. Although the magnetic field resonance method of wireless power transfer exhibits high efficiency, the leakage magnetic field due to the current flowing in the coil poses an issue. To date, leakage magnetic field strength has been obtained via electromagnetic field analysis. However, electromagnetic field analysis requires a long time and a large memory capacity. In this study, a method to obtain the leakage magnetic field strength with high accuracy solely via numerical calculations is derived. The accuracy of the calculation near the coil were decreased via the conventional calculation methods. At a distance of 1m from the coil, the proposed method improved from 8.56% to 2.12% in the x-direction and from 11.25% to 1.41% in the y-direction. The validity of each magnetic field strength calculation method was confirmed via experiments. Given that only the input voltage to the transfer coil and the design value of the coil are used in the calculation of the magnetic field strength, this method can be useful in the design of wireless power transfer systems.

This letter proposes an induction heating system for plate heating applications using an auxiliary work coil with double-D shape (DD coil). In this system, the DD coil is arranged at the center of a circular work coil to facilitate the heating of the center area. This arrangement ensures magnetic decoupling of the two work coils. Hence, each converter of the work coils can operate independently. Additionally, this letter proposes an approach to control the eddy current interference in a workpiece by controlling the phase relationship of the coil currents. The analysis results show that the proposed system offers each work coil greater independence of heating while reducing uneven heating of the workpiece.

This letter evaluates common-mode (CM) noise in two parallel-connected buck converters with phase shift control. These converters were synchronized based on real-time information from the Global Navigation Satellite System (GNSS). Utilizing real-time information from GNSS enables independent control of the two converters while ensuring high synchronization precision. The experimental results show that GNSS-based synchronization of each converter helps achieve the conventional phase shift control and shifts the first CM noise peak to a higher frequency.

This paper proposes a novel permanent-magnet synchronous motor (PMSM) mathematical model based on the premise that only armature reaction flux causes iron loss. It insists that the total loss in the case of zero torque is minimized by only zero stator current, which is consistent with experiences of engineers. The model consists of three basic equations that are self-consistent with others, and consequently have no mathematical contradiction. In addition to the model, this paper proposes a PMSM vector simulator based on the model. Moreover, the vector simulator is validated by numerical experiments.

We developed a torque stabilization method for the regenerative operation of speed sensorless vector controlled induction motor (IM) drives. Speed sensorless vector control suffers from a torque reduction phenomenon in regenerative operation. Therefore, we analyzed the cause and developed two stabilization methods: one to stabilize the decrease in IM flux and the other to adjust the velocity command in the low-speed range. Time domain simulations and experiments demonstrate the effectiveness of the proposed method.

Permanent magnet synchronous motors (PMSMs) generate torque ripple through the pulse width modulation (PWM) method of voltage source inverters. In this report, we propose a method to reduce torque ripple during overmodulation in asynchronous PWM. In asynchronous PWM, when the number of pulses decreases during high-speed rotation, three-phase voltage imbalance occurs and torque ripple occurs. By controlling the PWM pulse edge using trapezoidal wave modulation, seamless control from asynchronous PWM down to a single pulse can be achieved. The effectiveness of the proposed method was confirmed by its simulation and experimental results.