This thesis describes various examples of transformer voltages (induced voltage) associated with direct current motors and generators. The quantitative and useful index of CR filter design for the countermeasure for transformer (induced) voltage was be determined based on several actual measurements and analysis's of transformer (induced) voltages. In the other papers, the theory of transformer (induced) voltage had been explained, however there was no actual measurement related to the commutation. This paper describes the relationship between the transformer (induced) voltage and flashover.

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Giant Magnetostrictive Materials (GMM) came to attract attention because of great magnetostriction under moderate prestress condition, strong force, high response and so on. Recently, the design process of devices using this kind of smart material relies on computational tools increasingly. High accuracy analysis aids us in optimizing the performance of devices in the design stage. Then various kinds of analysis methods have been studied, however, it seems that any effective analysis method has not developed yet. One of the crucial reasons is that the nonlinearity of GMM is not considered in conventional method. In this paper, the magneto-mechanical coupled analysis method for GMM actuator is proposed using 3D-FEM under various prestress conditions, in which the nonlinearity of GMM characteristics are considered. Moreover, the validity of the proposed analysis method is verified through the comparison with the experiment of a prototype.

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During the turn-on period of IGBTs under inductive load switching, a collector voltage waveform characterized by medium-voltage hump followed by a long tail is usually observed. Further, this waveform indicates a large turn-on dissipation and is significant in the case of trench-gate FS-IGBTs designed on the basis of the wide-cell-pitch concept with floating p-base. In order to understand the lossy waveform, the transient behavior of the floating p-base in the wide-cell-pitch trench gate FS-IGBT is analyzed quantitatively. The transient behavior corresponding to the long tail has been interpreted well on the basis of the unintentional operations of a parasitic p-channel MOSFET and/or pnp transistor.

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This paper describes the comparison of the characteristics of double- and single-sided windings of contactless power transfer systems used in electric vehicles. The self-inductance changes with the electric current when the gap length is fixed in single-sided windings. The issue is resolved by maintaining the secondary voltage constant. In the case of double-sided windings, the transformer can be miniaturized in comparison with the single-sided winding transformer. However, the coupling factor is small, and appropriate countermeasures must be adopted to reduce the back leakage flux. The leakage flux is reduced by placing an aluminum board behind the transformer. Thus, the coupling factor increases.

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In this paper, a robust control of two-wheeled mobile manipulator with underactuated joint is considered. Two-wheeled mobile manipulators are dynamically balanced two-wheeled driven systems that do not have any caster or extra wheels to stabilize their body. Two-wheeled mobile manipulators mainly have an important feature that makes them more flexible and agile than the statically stable mobile manipulators. However, two-wheeled mobile manipulator is an underactuated system due to its two-wheeled structure. Therefore, it is required to stabilize the underactuated passive body and, at the same time, control the position of the center of gravity (CoG) of the manipulator in this system. To realize this, nonlinear backstepping based control method with virtual double inverted pendulum model is proposed in this paper. Backstepping is used with sliding mode to increase the robustness of the system against modeling errors and other perturbations. Then robust acceleration control is also achieved by utilizing disturbance observer. Performance of the proposed method is evaluated by several experiments.

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This paper proposes a novel DC-DC converter for a hybrid power supply using both a fuel cell and battery. The output voltage is controlled by a series converter that regulates only the differential voltage between the fuel cell and the output. Although the output power changes, the variation in the fuel cell current is suppressed by using a battery for the operation of the parallel converter. The control strategy and circuit design adopted to achieve high efficiency are described in this paper. The experimental results confirm that the proposed circuit achieves a maximum efficiency of 98.8% for a small differential voltage. In addition, the power loss is analyzed to prove the validity of the proposed circuit.

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This paper presents the modeling and controller design of a ropeless elevator model that employs a pair of linear synchronous motors (LSMs) with Halbach array magnets as the field. Analytical formulations are given to a conceptual design model. We apply a sliding mode control to design the motion control with three degrees of freedom. The control inputs are the thrust and normal forces of the two LSMs. We show that a decentralized control structure gives a better performance than a centralized control structure and that feedforward control is required in order to compensate for the gravitational force. The simulation results show that the elevator behavior is well controlled in spite of mutual interactions among the control variables.

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This paper describes a novel drive control scheme of electric power assisted wheelchairs based on neural network learning of human wheelchair operation characteristics. “Electric power assisted wheelchair” which enhances the drive force of the operator by employing electric motors is expected to be widely used as a mobility support system for elderly and disabled people. However, some handicapped people with paralysis of the muscles of one side of the body cannot maneuver the wheelchair as desired because of the difference in the right and left input force. Therefore, this study proposes a neural network learning system of such human wheelchair operation characteristics and a drive control scheme with variable distribution and assistance ratios. Some driving experiments will be performed to confirm the effectiveness of the proposed control system.

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This paper discusses a permanent magnet synchronous motor (PMSM) drive system based on direct torque control. First, in this paper we propose a novel torque-limiting and flux-weakening method. Torque limiting method capable of current limiting is based on the power equation instead of the motor model in the rotating d-q frame, which is synchronized to the rotor magnet. In this torque limiting method, the motor parameters need not be determined and this simplifies the limitation calculation. The proposed method incorporates a flux-weakening control that does not require motor parameters other than the armature resistance. These proposed schemes are implemented in a calculator for calculating the reference torque and reference flux. Second, we also propose an anti-windup scheme for torque control based on proportional and integral control. Generally, the controller winds up when the terminal output voltage of the inverter is saturated. The wind-up degrades the torque limiting and torque control performance. In the proposed anti-windup scheme, the gain of the integral element is varied on the basis of the degree of voltage saturation, which is detected by using the estimated flux-linkage. In this paper, the direct-torque-control-based drive system combined with a speed controller is presented, and the proposed system achieves stable operation. The proposed system is validated through experiments.

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This paper presents a novel design approach for feedforward compensation by employing specified step settling to provide fast and precise positioning control of mechatronic systems. In the conventional approach, the saturation of control input essentially deteriorates the control performance in terms of response time and residual vibration suppression. However, in the proposed method of feedforward compensation, command shaping is performed within the deadbeat control framework, wherein a constraint on the control input can be imposed by using the LMI technique to ensure the desired control performance. Therefore, by using the proposed approach, a 2-degrees-of-freedom positioning controller can achieve the required settling performance without causing residual vibration under the constraint. The effectiveness of the proposed approach has been verified by carrying out numerical simulations and experiments on a prototype.

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In this paper, we study a control method based on the virtual indirect circuit method for a single phase to three phase matrix converter (MC). The MC has a capacitor at the input side to compensate for the single phase input power fluctuation. We propose a method to determine the amplitude of the compensation capacitor voltage on the basis of the load power. The method is validated using a 1350W class single phase to three phase matrix converter system. In addition, restrictions on the modulation ratio of the input current and the compensation capacitor current are revealed, showing the limit of the output voltage according to the load power.

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Magnetic gears have some benefits such as low noise, low vibration, and they are maintenance free as opposed to mechanical gears. In the view of these advantages, some high-performance magnetic gears have been proposed; however, these gears have a complex structure because they require several magnets. In this paper, we propose a new magnetic gear with a high reduction ratio comprising only two magnets. From the result of 3D-FE analysis, it was found that our model generated large transmitted torque and less cogging torque despite its thin compact size. This result shows the possibility of the application of the proposed gear in various industries.

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This paper proposes a generalized circuit configuration of a new multilevel current-source inverter (CSI). In this new topology, a three-level CSI of which all the power switches are connected at an identical potential level line works as a main inverter circuit, and inductor cells are connected in parallel with the main inverter as auxiliary circuits. The inductor cells are composed by full-bridge power converters with inductors across the bridges. The inductor cells work to generate intermediate level currents of the output to obtain a multilevel current waveform without any additional external DC power sources. Five-level and nine-level PWM inverter configurations, including their chopper circuits as DC current-power sources, are verified through computer simulations. Furthermore, an experimental prototype of a five-level CSI is setup and is tested. The results show that the circuit works properly to generate the five-level output current waveform, which proves feasibility of the proposed strategy.

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Versatility and adherence to safety norms that are required of manipulators used in a human environment can be achieved by using tendon mechanisms that employ nonlinear springs. The nonlinear spring used in this paper is stiffness adjustable tendon (SAT), which has advantages such as it is light weight, low cost, and has a simple structure. However, precise tension control of SAT cannot be achieved by conventional methods based on a spring characteristic equation because of the SAT's hysteresis characteristics. Therefore, we propose a tension control method for nonlinear springs whose precise equation is difficult to obtain, such as SAT; this method is realized by using a disturbance observer and a reaction force observer. Experimental results validate the proposed method.

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Single-phase and three-phase voltage source converters with variable voltage and constant frequency ac-ac conversion are presented. These converters are a single bridge circuit of two legs for single-phase conversion and of three legs for three-phase, respectively. Both the power source and the load are connected to bridge legs. The normal PWM methods with the sinusoidal modulating and the triangular carrier waves are used for the converters. The experimental results confirm that the PWM converters can generate the sinusoidal input/output currents.

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This paper describes a sensorless control method of axial active magnetic bearings (AMBs). At high frequencies, inductance of the axial electromagnets is hardly dependent on the airgap because of the eddy current effects of the non-laminated core. Therefore the carrier frequency should be 3 kHz below to improve the sensitivity to the airgap. In the experiment, Sensorless controll of the axial AMBs have been achieved.

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The novel trans-linked single phase interleaved PFC converter suitable for the plug-in hybrid electric vehicle is proposed in this paper. The proposed trans-linked PFC converter can achieve the miniaturized performance for its scale and weight. As compared with the conventional single phase PFC converter, the core size and the value of the smoothing capacitor in the proposed trans-linked PFC converter is less than 1/2 that in the conventional one. Though the miniaturized performance, the proposed trans-linked PFC converter can be operated under the control system of the conventional interleaved single phase PFC converter. The operation characteristics and performances of the proposed trans-linked PFC converter is evaluated and discussed with experimental results.

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