This paper proposes a novel current control system for a PMSM that can stably operate even in the overmodulation range of an inverter. Because an inverter generates harmonic components in this range, an instability problem in the conventional current control system usually occurs. For solving this instability problem, the idea of harmonic current compensation scheme has already been proposed. However, the effectiveness of this method depends directly on the harmonic current estimation accuracy.
There are two new topics in harmonic component estimation that we use in our proposed current control system as follows: (1) the harmonic voltage estimation method that is based on the conventional sinusoidal PWM modulation technique, and (2) the harmonic current estimation method that estimates correctly both in the steady state and transient condition. The effectiveness of the proposed methods is confirmed by computer simulation and experimental results.

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In recent years, induction-heating (IH) cookers that can be used to heat nonmagnetic metals such as aluminum have been produced. Occasionally, a light pan moves on a glass plate due to buoyancy when heated by an IH cooker. In some IH cookers, an aluminum plate is mounted between the glass plate and the coil in order to reduce the buoyancy effect. The objective of this research is to evaluate the buoyancy-reduction effect and the heating effect of buoyancy-reduction plates. Eddy current analysis is carried out by 3D finite element method, and the electromagnetic force and the heat distribution on the heating plate are calculated. After this calculation is performed, the temperature distribution of the heating plate is calculated by heat transfer analysis. It is found that the shape, area, and the position of the buoyancy reduction plate strongly affect the buoyancy and the heat distribution. The impact of the shape, area, and position of the buoyancy reduction plate was quantified. The phenomena in the heating were elucidated qualitatively.

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The decline in the quality of patient's safety control is a problem, because the number of caretakers is reduced by the acceleration of demographic aging in an elder care facility. Especially, the detection of getting up from the bed is very important for preventing patients from falling and wandering unbreakable. In our previous study, we have developed the getting up detection device with an ultrasonic radar, which is safe, cheap, and break-proof. However, if there are many patients in a ward, it is difficult to use some ultrasonic radars. The reason is that if some ultrasonic radars, which have the same frequency, are used in same ward, the ultrasonic signals are coherent with each other. To solve this problem, we propose a novel incoherent method. This method is achieved by improving the software in the device at a low cost.

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This paper presents a novel Zero Current Switching (ZCS)-PWM controlled half-bridge DC-DC converter with High-Frequency (HF)-link. The newly-proposed soft switching DC-DC converter consists of a multi-resonant half-bridge HF-isolated inverter controlled by an asymmetrical PWM scheme and a center-tapped diode rectifier with a choke input filter. In order to attain the wide range of soft-commutation under the condition of constant switching frequency, the single Active Edge-Resonant Cell (AERC) that is composed of a lossless inductor and a switched resonant capacitor is originally employed for the half-bridge inverter arm, providing and assisting ZCS operations in the switching power devices. The ZCS-PWMDC-DC converter treated here is evaluated in experiments using the 800 W-55 kHz prototype. The practical effectiveness of the proposed soft switching DC-DC converter is actually demonstrated and discussed with the experimental results under open loop and closed loop configurations. Finally, the feasibility of the DC-DC converter topology is discussed from the view points of the high efficiency and high power density.

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We propose a new beatless control mechanism for permanent-magnet synchronous motor (PMSM) drives. In drive systems, the three-phase voltage source induces a ripple component whose frequency is six times that of the voltage source frequency in the DC voltage. Therefore, if the motor frequency becomes six times the voltage frequency, a beat phenomenon, which causes an increase in the motor current ripple is observed. We analyze the beat phenomenon which causes current ripples and propose a method based on periodic disturbance current regulation, i.e., beatless control. We carry out time-domain simulation and various experiments and demonstrate the effectiveness of the proposed controller.

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Global efforts toward energy conservation, increasing data centers, and the increasing use of IT equipments are leading to a demand in reduced power consumption of equipments, and power efficiency improvement of power supply units is becoming a necessity. MOSFETs are widely used for their low ON-resistances. Power efficiency is designed using time-domain circuit simulators, except for transformer copper-loss, which has frequency dependency which is calculated separately using methods based on skin and proximity effects. As semiconductor technology reduces the ON-resistance of MOSFETs, frequency dependency due to the skin effect or proximity effect is anticipated.
In this study, ON-resistance of MOSFETs are measured and frequency dependency is confirmed. Power loss against rectangular current pulse is calculated. The calculation method for transformer copper-loss is expanded to MOSFETs. A frequency function for the resistance model is newly developed and parametric calculation is enabled. Acceleration of calculation is enabled by eliminating summation terms. Using this method, it is shown that the frequency dependent component of the measured MOSFETs increases the dissipation from 11% to 32% at a switching frequency of 100kHz.
From above, this paper points out the importance of the frequency dependency of MOSFETs' ON-resistance, provides means of calculating its pulse losses, and improves loss calculation accuracy of SMPSs.

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Amorphous alloy exhibits high permeability and extremely low iron loss compared to magnetic steel sheet. Therefore, it is expected to contribute to the efficiency improvement of electromagnetic application products such as motors, generators, and transformers.
In this paper, we examined an axial-type motor that uses the rolled amorphous core as a stator core for the purpose of applying amorphous alloy to a motor for air-conditioning equipments. We propose the motor structure to use amorphous alloy as a rolled core without complicated processing, and the evaluation results of the trial motor clarified that this structure is able to meet the target motor efficiency of 85% under the conditions that the size of the motor is below φ100mm × 60mm and that ferrite magnets are used.

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This paper presents an analysis of the steady and transient characteristics of capacitor-input-type diode rectifier circuits connected to a delta-star transformer in a three-phase rectangular-waveform distribution system. Equations are derived for the input current, output voltage, and total input power factor of the rectifier circuits. The total input power factor can be improved from 0.91 to 0.98 by using the delta-star transformer. Further, design methods are developed for both the input reactor and output capacitor of the rectifier circuits. A small input reactor is desirable for obtaining a large total input power factor and a constant output voltage. The output capacitor can be designed to obtain the required output voltage variation in steady and transient states. The effectiveness of the proposed analysis is experimentally verified by using a 2.4kW prototype.

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This research focuses on the development scheme of a power converter in a gas engine cogeneration system using a power hardware-in-the-loop simulation. A matrix converter is adopted to substitute a conventional ac/dc/ac converter and transfers three phase electricity to single phase electricity directly. To inevstigate the interaction between gas engine-generator unit and the proposed matrix converter, a power hardware-in-the-loop simulation is carried out, in which a piece of real matrix converter is installed in the simulation loop and interfaces with the numerical model of gas engine-generator unit. Numerical models of gas engine and generator are presented and verified by experiment. The configuration of the power hardware-in-the-loop simulation is described and results are also presented, through which the practical application of matrix converter is well demonstrated.

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In this paper, a novel integrated stability program (ISP) based on robust rolling stability control (RSC) for in-wheel electric vehicle (EV) is proposed. Since EVs are driven by electric motors, they have the following four remarkable advantages: (1) motor torque generation is quick and accurate, (2) motor torque can be estimated precisely, (3) a motor can be attached to each wheel, and (4) a motor can output negative torque as a brake actuator. These advantages enable a high-performance three-dimensional vehicle motion control with a distributed in-wheel-motor system. Rolling stability is important for all classes of light-vehicles, especially, for EVs that have narrow tread and high center of gravity. In this study, RSC is designed using two-degree-of-freedom control (2-DOF), which achieves tracking capability to reference value and disturbance suppression. However, as the drivability of the vehicle will be changed significantly if only RSC is applied, vehicle rolling motion should be controlled depending on the rolling state. Therefore, variable weight-ISP and variable reference-ISP are proposed using rolling state information. For detecting rolling state, rollover index (RI) is introduced. The validity of the proposed methods is shown by the simulation and the experimental results.

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During the voltage saturation of a PWM inverter driving a motor, the torque control characteristics of the motor deteriorate because the controller can control only the phase of the output voltage. The cross-coupling current control scheme is a control scheme for motors, and it can be used to shift from the variable voltage mode to the voltage saturation mode seamlessly, and vice versa. This paper shows numerical simulation results and the torque response when the control scheme is used during voltage saturation.

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The peculiar structure of a hybrid stepping motor enables us to change its tooth arrangement without having to change its phase or number of rotor teeth. Each arrangement has its own flux distribution and iron loss. In this paper, two types of 3-phase stepping motors with different tooth arrangements are reported. A comparison between the estimated and measured iron losses in the two motors is drawn. The reason for the difference between the estimated and measured values is explained on the basis of the FEM results obtained.

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This paper proposes a new dc-voltage-balancing circuit for a five-level diode-clamped inverter intended for a medium-voltage motor drive. This circuit consists of two unidirectional choppers and a single coupled inductor with two galvanically-isolated windings. The dc magnetic fluxes in the magnetic core, which are generated by the two windings, cancel out each other. Therefore, the inductor does not generate any dc-magnetic flux in the magnetic core. This makes the inductor compact by a factor of six compared to previously used balancing circuits containing two non-coupled inductors. Experimental results obtained from a 200-V 5.5-kW downscaled model verify that the dc mean voltages of the four split dc capacitors are balanced well under all operating conditions.

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In this paper, a method for walking stabilization control using a virtual plane method for up-down motion of biped robots is proposed. In the case of the up-down motion in whitch the height of the center of gravity (COG) is not constant, the Zero-Moment Point (ZMP) equation that shows the relation between the ZMP and the COG becomes linear time-variant. Using the proposed method, the ZMP equation is transformed into linear time-invariant. Therefore, the frequency analysis and parameter design of the walking stabilization control can be implemented easily even in the up-down motion. The validity of the proposed method was confirmed by some simulations and experiments.

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Magnetic gears have some advantages such as low mechanical loss and maintenance-free operation that are not observed in conventional mechanical gears, and various kinds of magnetic gears have been proposed; however, they also have demerits: low torque and a complex structure involving multipole magnets. We have previously proposed a hybrid-type magnetic gear with a simple structure that can generate large torques; however, it was found that the high-speed rotor in the gear developed a large cogging torque, causing vibrations and generating noise. In this paper, a method for reducing the cogging torque is presented, and it is verified by a 3D FEM and carrying out measurements on a prototype.

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Recently, induction motors (IMs) and permanent-magnet synchronous motors (PMSMs) have been used in various industrial drive systems. The features of the hardware device used for controlling the adjustable-speed drive in these motors are almost identical. Despite this, different techniques are generally used for parameter measurement and speed-sensorless control of these motors. If the same technique can be used for parameter measurement and sensorless control, a highly versatile adjustable-speed-drive system can be realized. In this paper, the authors describe a new universal sensorless control technique for both IMs and PMSMs (including salient pole and nonsalient pole machines). A mathematical model applicable for IMs and PMSMs is discussed. Using this model, the authors derive the proposed universal sensorless vector control algorithm on the basis of estimation of the stator flux linkage vector. All the electrical motor parameters are determined by a unified test procedure. The proposed method is implemented on three test machines. The actual driving test results demonstrate the validity of the proposed method.

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In this paper, the effect of the plasma washing on the characteristics of unused three phase induction motor is clarified. We make plasma washing on the rotor and compare the characteristics of the motor after the washing with before the washing.

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An improvement of frequency characteristic of self-sensing active magnetic bearings (AMBs) with zero-bias current control is proposed. In the self-sensing AMBs non-liner magnetic characteristic of electromagnet degrades the frequency characteristic of the position sensing. Furthermore noise is observed due to alternations of electromagnet's excitation. This also degrades the frequency characteristic. In this paper, current-interference compensation and linearizing current disturbance are utilized. The method achieves improvement of the frequency characteristic of the position sensing.

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The regenerative energy from the motor drive systems used in the injection molding is consumed by resistors connected to the DC bus of the inverters. Recently the recovery systems of the regenerative energy with a bi-directional DC-DC converter and capacitors have been developed. In this paper a new control strategy of the EDLC based energy recovery system is proposed. The basic principle of the proposed control strategy and the power losses consumed in the energy recovery system are discussed in detail. The validity and practicability are confirmed by digital computer simulation.

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