Vector control is used to drive a DC brushless motor and generally needs current information. DC bus current detection is often adopted as a low cost method for reconstructing three-phase currents. PWM modifying techniques increase the DC pulse duration, thereby enabling easy detection of the DC bus current. However, these techniques have two problems: reducing a noise frequency and making the reconstructed current waveforms distorted by current ripple. In the techniques, modification signals are added to the three-phase voltage commands; the sum of the signals over a single cycle is zero.
The authors examined several PWM modifying techniques from the points of view of noise and current distortion performance. One of the techniques had a good noise performance, and the frequency component of the noise was the same as the carrier frequency (f_c). However, the reconstructed current waveforms were distorted. The total harmonic distortion (THD) varied from 1.7% to 4.1%. Another technique had a very poor noise performance, and the frequency component on the noise was one-fourth of f_c. The authors developed a new PWM modifying method called “Half Pulse Shift”, which achieves the optimum noise and current distortion performance. The frequency component of the new method was two-thirds of f_c, and the current waveforms were not distorted; the THD in the simulations and experiments was 0.5%-1.4% and 3.4%-3.6%, respectively.

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A new wind turbine generating system that employs a current-source thyristor inverter is proposed, and the steady-state and dynamic performances for a practical system are discussed. The proposed system is essentially based on the shaft generator system that is widely used in large ships, and it has many features such as high reliability and generation of output power of high quality. It is shown that electric power with constant frequency and voltage with low distortion can be obtained by using this novel system despite the changes in the velocity of natural wind. A dynamic model of the system is also developed, and a good agreement between simulated and experimental performances is obtained, thereby confirming the validity of the model.

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This paper presents a method for remaining life assessment of oil-immersed transformers using analyzable structured neural networks. Remaining life assessment of oil-immersed transformer is very important. Furfural method is conventionally used for such an assessment. In the furfural method, the average degree of polymerization is determined by considering the nonlinear correlation between the furfural and average degree of polymerization. The remaining life is estimated by considering the average degree of polymerization. However, a range of estimates of the remaining life is obtained when the furfural method is used, making accurate estimation difficult. The proposed method can be used to estimate the remaining life of an oil-immersed transformer accurately; this method involves analyzable structured neural networks and ensemble method. In the proposed method, not only furfural but also oil temperature, operational status, cooling type, etc., are considered. Since various factors are considered as input variables and a nonlinear model, i.e., artificial neural networks are used, accurate estimation of the remaining life has been realized. The effectiveness of the proposed method is shown by numerical simulation using actual measured data.

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Adaptive infinite impulse response (IIR), or recursive, filters are less attractive mainly because of the stability and the difficulties associated with their adaptive algorithms. Therefore, in this paper the adaptive IIR lattice filters are studied in order to devise algorithms that preserve the stability of the corresponding direct-form schemes. We analyze the local properties of stationary points, a transformation achieving this goal is suggested, which gives algorithms that can be efficiently implemented. Application to the Steiglitz-McBride (SM) and Simple Hyperstable Adaptive Recursive Filter (SHARF) algorithms is presented. Also a modified version of Simultaneous Perturbation Stochastic Approximation (SPSA) is presented in order to get the coefficients in a lattice form more efficiently and with a lower computational cost and complexity. The results are compared with previous lattice versions of these algorithms. These previous lattice versions may fail to preserve the stability of stationary points.

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In this paper, skid prevention control based on torque reduction is proposed for EVs driven by an IPMSM. The traction characteristics of the electric vehicle are improved by using a modified current controller to rapidly reduce the torque of the driving motor. In order to compensate for back-EMF, a disturbance observer is introduced. In addition, we propose skid prevention for an IPMSM by torque reduction using both the dq-axes currents. Further, we verify the effect of each control method by conducting experiments in which the electric vehicle is driven on a slippery road.

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Currently, the development of leading-edge technology for recording and loading human motion on the basis of haptic information is required in the field of manufacturing and human support. Human movement is an assembly of motion components. Since human movements should be supported by a robot in real time, it is necessary to integrate the morion components, which were saved earlier. Once such motion integration is realized, future technology for use in daily human life is developed.
This paper proposes the integrated reproduction of the decomposed components of human motion by using a motion copying system. This system is the key technology for the realization of the acquisition, saving and reproduction of the real-world haptic information. By the proposed method, it is possible not only to achieve expert skill acquisition, skill transfer to robots, and power assist for each motion component but also to open up new areas of applications.

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Bearing failure is well-known as a common problem in industries. Therefore, timely diagnosis and prognosis (DAP) of bearing fault is very crucial in order to prevent sudden damages. This paper proposes the practical method of bearing fault DAP using acoustic emission (AE) technique assisted with artificial neural network (ANN). The bearings failure data is measured based on the AE in terms of decibel (dB) and Distress levels, which are used as input for ANN of a bearing fault DAP. For this purpose, an experimental rig is setup to collect data from target bearing by using Machine Health Checker (MHC) Memo assisted with MHC Analysis software. In this work, Elman network with training algorithm, Levenberg-Marquardt Back- propagation is used for ANN DAP. The obtained results indicates that the proposed methods are suitable to inform the remaining useful life time of a faulty bearing.

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In recent years, consumer induction-heating (IH) cooking appliances have grown increasingly popular because of their easy cleaning, high efficiency, safety, and controllability. IH food cooking system for consumer home use are indispensable to heat various metallic pans, such as aluminum, copper, stainless steel, and iron cast for further diffusing. Furthermore, these appliances have to satisfy the utility AC grid harmonics regulations of IEC61000-3-2. To meet these requirements, this paper proposes a two-stage soft-switching high-frequency inverter with simple PFC function that is suitable for consumer IH cooking appliances. The proposed system comprises a soft-switching chopper based boost PFC converter with passive snubber and phase-shifted PWM controlled ZVZCS high-frequency inverter. In order to satisfy the utility AC grid current harmonic regulations, a simple PFC control technique with discontinuous current mode is introduced. This technique as well as the fundamental operating performances of the proposed IH system is tested. The effectiveness of proposed IH system is substantially proved from a practical point of view on the basis of the experimental results.

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In order to evaluate train timetables from passengers' points of view, it is indispensable to estimate the disutilities of passengers. This can be done by estimating the movements of passengers and trains accurately. In particular, when there are many passengers, an interaction between the passengers and trains must be considered. To this end, we have developed a microsimulation system to simulate both train operation and passengers' train choice behavior. The system can simulate train choice behaviors of more than one million passengers as well as their positions in trains. It is possible to estimate the delays caused by congestion in trains as well. The system is based on models of different attitudes of the passengers with respect to the train choice behavior, with includes the choice of the earliest train, transfer avoidance, and congestion avoidance; a passengers' train choice behavior reflects his/her preferences. We applied this system to an actual railway line in a metropolitan area and evaluated two train schedules by calculating the generalized cost that reflects each passenger's disutility in his/her experience. Through the numerical experiments, we have confirmed that the proposed method is very useful for evaluating timetables from passengers' points of view.

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This paper proposes a control method based on modal transformation for biped robots to climb unknown steps. This method is able to control the foot position of the biped robot and the ground reaction force acting in vertical direction when the biped robot climbs unknown steps in a double-support phase. The effectiveness of the proposed method is confirmed by simulation and experimental results.

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Motion recognition based on sensory information is important for providing assistance to human using robots. Several studies have been carried out on motion recognition based on image information. However, in the motion of humans contact with an object can not be evaluated precisely by image-based recognition. This is because the considering force information is very important for describing contact motion. In this paper, a modal-power-based haptic motion recognition is proposed; modal power is considered to reveal information on both position and force. Modal power is considered to be one of the defining features of human motion. A motion recognition algorithm based on linear discriminant analysis is proposed to distinguish between similar motions. Haptic information is extracted using a bilateral master-slave system. Then, the observed motion is decomposed in terms of primitive functions in a modal space. The experimental results show the effectiveness of the proposed method.

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A bilateral controller is used to transmit and share haptic information between a master system and a slave system. In a transmission system, the bilateral controller encounters problems in the event of data packet loss and/or disconnections. In this study, a master/slave simulator and environmental data memory are used to solve the problems. In the case of normal operation, the environmental data memory stores force data in a remote side. The control system is operated by the environmental data memory and master/slave simulator when the communication lines are disconnected.

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The evaluation of torque characteristics in a saturated magnetic field for permanent-magnet (PM) synchronous motors is presented. The torque saturation characteristics of non-salient and salient pole machines are investigated by finite element analysis and measurement. Thus, it is found that the torque saturation originates in the magnetic saturation in both the stator teeth, which are located on the leading position toward the direct axis, and in the stator back yoke, which is located on the lagging position toward the direct axis. This mechanism can also explain the reason for the significant torque saturation in the salient-pole machine; the higher inductance of the quadrature axis of the salient-pole machine causes a significant magnetic saturation in the stator back yoke. Therefore, less saliency or a wider back yoke can improve the torque saturation.

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With the development of information and communication technology, personal verification becomes more and more important. In the future ubiquitous society, the development of terminals handling personal information requires the personal verification technology. The signature is one of the personal verification methods; however, the number of characters is limited in the case of the signature and therefore false signature is used easily. Thus, personal identification is difficult from handwriting.
This paper proposes a “haptic pen” that extracts the writing pressure, and shows a character recognition method by time-frequency analyses. Although the figures of characters written by different amanuenses are similar, the differences appear in the time-frequency domain. As a result, it is possible to use the proposed character recognition for personal identification more exactly. The experimental results showed the viability of the proposed method.

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Electric double layer capacitors (EDLC) having very large capacitance have attracted attention as energy storage devices. The voltage rating of an EDLC is in the low range of approximately 2.3 to 3.0V. Hence, the use of EDLCs in power electronics requires many EDLC cells to be connected in series. Then an electronic circuit known as a parallel monitor is connected in parallel with each EDLC cell in order to avoid the overcharging which breaks it down. In this paper, we propose a new parallel monitor circuit, which consists of one MOSFET and two resistors. This parallel monitor circuit is not only simple but can be electrically separated from the EDLC cell during relaxation charging by connecting another simple electronic circuit. Therefore, the energy loss of this parallel monitor circuit is decreased. To confirm the advantages of this proposed parallel monitor circuit, a charging circuit, which comprises the proposed parallel monitors and the separation circuit described above, was fabricated for five serially connected EDLCs and experimentally examined. As a result, it was clarified that the charging efficiency of the proposed monitor with its separation circuit was 25% greater than that of the conventional one.

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In slip ratio control systems, it is necessary to detect the vehicle velocity in order to obtain the slip ratio. However, it is very difficult to measure this velocity directly. We have proposed slip ratio estimation and control methods that do not require the vehicle velocity with acceleration. In this paper, the slip ratio estimation and control methods are proposed without detecting the vehicle velocity and acceleration when it is decelerating. We carried out simulations and experiments by using an electric vehicle to verify the effectiveness of the proposed method.

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This paper proposes a novel control method for multi power supplies interface system using an indirect matrix converter. This system is constructed based on an indirect matrix converter, which does not have a large energy buffer such as an electrolytic capacitor. A snubber circuit of the indirect matrix converter is used to interface with a DC power supply. In addition, the proposed control method is based on an indirect control method with a space vector modulation. Therefore the proposed method can be easily used to achieve zero current switching in the rectifier stage.
This paper describes the multi power supplies interface system using an indirect matrix converter and its control method. Moreover, in this paper, the control range of the output voltage is analyzed. The validity of the proposed system is confirmed by the experimental results.

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This paper proposes a novel single-phase to three-phase power converter that can reduce the capacitance value of the smoothing capacitor in the DC link part. In the case of the single-phase converter, a large smoothing capacitor is required to absorb a power ripple with a frequency twice that of the power supply. The proposed method involves the use of an indirect matrix converter with an active snubber to absorb the power ripple. Therefore, the proposed system does not require a reactor and large energy buffer, such as a smoothing capacitor. Moreover, a diode bridge can be used on the rectifier stage in the proposed circuit. In this paper, the basic operation and validity of the proposed method are confirmed by simulation and experiment result. Thus, it is confirmed that good waveforms for input and output currents can be obtained by the proposed method.

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The recent introduction of very fast and frequent train services at Tokaido-Shinkansen makes it difficult to stabilize the feeding voltage only by compensating reactive power. Therefore, active power compensation has been introduced for further stabilization of the voltage, and a converter control strategy called “fixed power factor method” was applied in the commercial operation that started in February 2009. The feeding voltage stabilizing control by active power compensation is substantially more complicated than the conventional reactive power compensation. This paper describes a novel stability judging method for Shinkansen feeding system with multiple power converters; this method can be used to determine appropriate active/reactive compensation strategies that can be used by the operator of the new Shinkansen power supply system.

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This paper presents a medium-voltage motor drive with a three-phase modular multilevel PWM inverter and focuses on its control method and operating performance. This motor drive is particularly suitable for fans, blowers, pumps, and compressors, in which the load torque is proportional to the square of the rotating speed. Particular attention is paid to the dc-capacitor voltage fluctuation of each chopper-cell because it may affect the voltage rating of the power switching devices used. This paper describes the theoretical equations related to the amount of the voltage fluctuation. A downscaled model rated at 400V and 15kW is designed and built to confirm the validity and effectiveness of the nine-level (17-level in line-to-line) PWM inverter that is intended for use in medium-voltage motor drives to achieve energy savings.

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This paper presents a medium-voltage motor drive with a modular multilevel PWM inverter, and focuses on a startup method and its performance. It is formed by six modular arms, each of which consists of a cascaded stack of multiple bidirectional chopper-cells. The frequency of the dominant ac-voltage fluctuation is equal to the motor (inverter) frequency. These fluctuations occur in the dc capacitor of each chopper-cell, and the magnitude of the fluctuation is inversely proportional to the motor frequency. Because of the increased voltage fluctuation in low-frequency regions, the so-called “volt-per-hertz control” cannot be applied in motor starting. The startup method proposed in this paper is suitable for a motor drive with the modular multilevel PWM inverter. It enables the motor to produce a startup torque loaded on the motor at an initial amplitude and a fixed frequency of the inverter while taking into account constraints on the motor current and the ac-voltage fluctuation. The validity of the startup method as well as the startup performance is confirmed by experiment and simulation.

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This paper presents a novel control methodology for robust high-precision positioning systems. This methodology is based strain feedback using a piezoelectric element. The mechanical vibration modes at around the control bandwidth cause the deterioration of system stability. This prevents the positioning performance from being robust, particularly against variations in the vibration frequency. In this research, therefore, a robust positioning system was designed by applying an additional compensation loop by strain feedback; here, a piezoelectric element that acts as a strain sensor detects the vibration signal. This makes the performance of the system robust. The proposed compensation approach has been verified by numerical analyses and by experiments using a positioning device for industrial galvano scanners.

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Recently, linear oscillatory actuators have been used in a wide range of applications because of their advantages, such as high efficiency, simple structure, and easy control. Small linear oscillatory actuators are expected to be used in haptic devices and the vibration system of mobile phones.
In this paper, we propose a new structure of a small linear oscillatory actuator. The static and dynamic characteristics of the actuator are calculated by the 3-D finite element method. The effectiveness of this method is shown by the comparison of the calculated results with the experimental results.

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This paper proposes a new method of starting the hybrid power filter for wind power generation systems with soft starter. In the proposed method, an active filter of the hybrid power filter behaves a resistor for the source current under the starting condition. Thus the inrush phenomena of the passive filter are perfectly suppressed. The basic principle of the proposed starting method is discussed, and then confirmed by digital computer simulation using PSCAD/EMTDC. Simulation results demonstrate that the proposed starting method can overcome the inrush currents for the passive filter, building up the dc voltage of the active filter.

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This paper proposes a new method for position estimation of salient-pole permanent-magnet synchronous motor using the second high-frequency current correlated signal in new coordinates in addition to the conventional high-frequency current correlated signal. In the proposed method, even when a spatially-rotating ellipse-shape high-frequency voltage is injected, the relation between the position error and the estimated position shows a linear correlation in the region of ±π/2.

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