This study investigates the influence of the equivalent mass fluctuation on the control performance of a workspace-based motion control system with a workspace observer. It is theoretically demonstrated that the equivalent mass fluctuation affects the control gain, the cut-off frequency of the workspace observer, and so on. In addition, the effectiveness of the workspace motion controller based on the estimated equivalent mass with the workspace observer is discussed. In order to verify the workspace-based control method with the estimated equivalent mass, some simulation and experimental results obtained with the workspace position control of a two-degrees-of-freedom planar manipulator are presented.

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This study compares the characteristics of a PWM voltage source inverter (VSI) and PWM current source inverter (CSI) for an IPMSM drive system with concentrated winding. Past analysis showed that the PWM CSI had inferior operating characteristics compared with the PWM VSI. Thus, high-performance PM motor drive systems have been using a VSI for small-capacity applications. There has been almost no research addressing improvements in CSI motor drive systems. In this study, experiments were performed to compare the three-phase current and torque characteristics generated by VSIs and CSIs.

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This paper proposes a new concept for a contactless power supply system (CPS) in a mechanical multi-level parking tower for plug-in hybrid vehicles (PHVs) and electric vehicles (EVs). In recent years, PHVs and EVs have been commercialized as low environmental impact vehicles, and the demand for such vehicles is spreading rapidly. To cater to this increasing demand of PHVs and EVs, battery charging systems in the parking tower are necessary. Most multi-level parking towers have movable parking pallets that are electrically isolated from the building side. Because of the poor positional accuracy of the movable pallets, a contactless power transmission system between the utility grid in the building and the movable pallet is necessary. As for the CPS in the parking tower, a power conversion stage from commercial AC to high-frequency AC is necessary for size reduction. In general, such a power conversion system consists of power factor correction (PFC) converters and high-frequency inverters. Therefore, two or more conversion stages are necessary, which increases the power losses and cost. In this paper, a simple circuit configuration of a high-frequency link AC-AC converter for a CPS in a parking tower is proposed. The proposed high-frequency link AC-AC converter can directly convert commercial AC to high-frequency AC (HFAC) and HFAC to commercial AC again. Experiments are performed to demonstrate the validity of the proposed CPS. The proposed CPS is found to have a coupling coefficient of 0.75 for a contact-less transformer with a 10mm gap, and an efficiency of 86% can be achieved.

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Electric railway vehicles require high electric power when powering and return high electric when regenerating. Therefore, the fall in vehicle performance due to a voltage drop and the restriction on regenerative power due to a load shortage become problems in a DC-electrified railway. Therefore, energy storage devices (ESDs) are mounted on vehicles to assist the power of powering and to absorb the power of regeneration. In recent years, various hybrid vehicles have been studied because the performance of ESDs has become good enough for them to be mounted on vehicles. Generally, the design of the controller is a complicated problem because the vehicle operates under various running conditions. In this paper, a simple controller for ESDs is designed in the frequency domain. This controller aims at smoothing the input power and at managing the ESD energy. The proposed controller is examined under various running conditions with numerical simulations.

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Recently, the large-scale wind turbine market has expanded from onshore to offshore. Under the circumstances, to respond to requirements related to downsizing and weight reduction for the on-board generator, a permanent magnet type synchronous generator has been used. Because the offshore wind turbine drive train is difficult to maintain and so reliability is critical, a direct drive generator as well as a medium-speed generator with a low ratio gear are proposed for the drive train. With such a generator design, consequently, we have to investigate the number of poles and the winding method required to respond to the drive train type. In this study, we design a permanent-magnet type-synchronous generator for the medium-speed-type drive train, where we decide to employ the fractional slot winding method for high efficiency and low total harmonic distortion performance. We conclude that the optimum number of slots per pole per phase q is in the range 1 < q < 3/2. This is confirmed by experiments using a 2.2MW, 18min^-1 test machine.

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It is essential that photovoltaic (PV) systems detect islanding quickly to ensure electrical safety. We have proposed and developed a new active islanding prevention method that detects harmonic impedance. To verify the effectiveness of the proposed method, we conducted performance evaluation tests in the case of a mixed connection in PV inverters through different active islanding detection methods.

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Series connections of energy-storage modules such as electric double-layer capacitors (EDLCs) or lithium-ion batteries result in a voltage imbalance because of the nonuniform properties of the individual modules. Although various types of cell voltage equalizers have been proposed, the required numbers of transformer windings or magnetic components in conventional equalizers proportionally increase with the number of series connections of the cells. Therefore, conventional equalizers tend to be expensive and bulky and to have less extendability to increase the number of series-connected cells. This paper describes a novel cell voltage equalization circuit using an LC series circuit. The proposed circuit reduces the number of magnetic components, which gives cost and size advantages. The fundamental operating principles and detailed design procedures of the key components are presented. Experimental cell voltage equalization tests using the proposed equalization circuit were performed using eight series-connected EDLC and lithium-ion-battery modules whose initial voltages were intentionally imbalanced. The experimental results demonstrated that the proposed circuit was able to equalize the voltage of each cell connected in series. In addition, the standard deviation of each cell voltage was reduced to a sufficiently low value below 10mV after a finite time.

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This paper proposes a torque ripple suppression method for dealing with the system identification model error through learning and correction. A torque ripple generated by a motor or any other source causes many problems such as noise and vibration. We proposed the periodic disturbance observer to suppress a torque ripple. This method is a relatively simple control scheme built by using a system identification model. It has a high suppression effect regardless of the order of the target frequency. However, the model error leads to an increase in the convergence time to suppression and unstable control. Therefore, there is a need to improve the robustness against modeling errors.
The proposed method corrects for the existing system model through dynamic system identification using a torque ripple component detection value and estimate value. By adding the error correction function to the periodic disturbance observer, the problem caused by the model error is solved and the robustness is improved. This paper explains the proposed method and demonstrates the effectiveness of the proposed method through simulation and experimental results.

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This paper discusses a combination of input and output controls for a matrix converter with a generator and a motor. When an input stability control and an output current control are applied independently, the operation of the matrix converter becomes unstable because the controllers interfere with each other. As a solution to this problem, this paper proposes an output current control that includes a damping factor for input filter oscillation. In this paper, the stability of the proposed control is discussed using root locus analysis on a single phase equivalent circuit of the matrix converter. In addition, this study confirms the validity of the proposed control for a matrix converter with a generator and a motor through simulation and experimental results.

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Recently, many energy-saving household appliances such as air conditioners, refrigerators, and LED bulbs are being used in residences. Most household appliances use diode rectifiers equipped with smoothing dc capacitors, which output a large amount of harmonic current into utility lines. This harmonic current may cause electrical equipment to malfunction or fail. This paper discusses the harmonic compensation characteristics and power rating of a single-phase active filter, and proposes the use of control methods for reducing the power rating of the active filter. Furthermore, three single-phase active filters in conjunction with the proposed control method are used in an experiment on a three-phase system. The experimental results confirm that the frequency limitation method is suitable for a single-phase active filter.

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The present paper discusses the optimized design method for the efficiency and power density of a multilevel converter based on the implementation of system integration of power electronics. The performance of a five-level ANPC inverter is compared with that of a conventional two-level inverter, a three-level DC inverter, and a three-level T-type NPC inverter. For a switching frequency range of 1kHz to 500kHz, the comparison results indicate that the five-level ANPC inverter achieves both the highest efficiency and the highest power density.

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This paper presents a novel simultaneous optimization between feedforward (FF) and feedback (FB) compensators in a 2-degree-of-freedom (2-DOF) position control system. The authors have already proposed a simultaneous optimization scheme for the 2-DOF control system whose positioning performance is robust against resonance frequency fluctuations in the plant system. However, the conventional approach requires a higher-order FB compensator for each stroke condition, which increases the controller implementation cost. An efficient simultaneous design approach, therefore, is required from the standpoint of industrial applications. In this study, the conventional simultaneous design scheme is applied to multi-stroke conditions to reduce the number of FB compensators. In addition, the optimized FB compensators are approximated as low-order compensators to reduce the implementation cost. The effectiveness of the proposed approach has been verified through numerical simulations and experiments using a laboratory prototype of a galvano scanner.

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This paper describes a boost driver containing a charge-pump (CP) circuit and a method for its voltage regulation. The proposed driver can boost its DC link voltage by the voltage level of a capacitor in the CP circuit. An advantage of this driver is that it can charge the capacitor during power drive, enabling the driver to work continuously with sufficient boost performance. Moreover, the driver can reduce the harmonics in the output voltage. The numerical analysis and experimental examinations assess these features. Furthermore, the experiments investigate whether the driver not only performs as well as the conventional boost driver but also has a higher efficiency than it.

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The motion of ferrite particles was used to treat the excess activated sludge produced in waste water treatment plants. The motion of ferrite particles was controlled by two electromagnets (EMs). We have proposed a magnetic circuit with two metal plates between the EMs, so that the magnetic flux of the magnets can be obtained for a larger area. Thus, a larger container with activated sludge can be treated and by applying an AC voltage to it, can be sterilized and its quantity can be reduced. Our experiments show the prospects of using magneto-ferrite treatment in the return line of activated sludge in a sewerage plant.

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Our researches focus on motion control and robotic systems. Our laboratory not only makes a study on leading-edge research but also develops teaching materials for the motion control.

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