This paper presents the position sensorless control of a switched reluctance motor (SRM). Position estimation accuracy is dependent on the measurement accuracy of the differential current, which is typically measured by dividing the difference between two sampled currents by the sampling period. The division error increases at a high carrier frequency because the sampling period is short. In this study, an analog circuit of a type-1 control system was utilized to reduce the error. The type-1 control system is a stable feedback loop with a first-order integrator element. When the current is input to the analog circuit, the output signal of the integrator converges to the current and the input signal of the integrator is measured as a differential current. Therefore, the differential current is directly measured without the division. The experimental results confirm the effectiveness of the proposed method.

We propose a variable flux reluctance motor with a single set of coils. This motor can control the torque-speed characteristics by increasing or decreasing the DC voltage, which is superimposed on the AC voltage. In this paper, we compare the performance of the proposed motor with that of an interior permanent magnet motor, switched reluctance motor, and induction motor. Finally, the high-performance mechanism of the proposed motor is investigated.

This paper presents a stabilization method using a passivity-based criterion for a residential dc system. In a dc system, we assume a dc distribution board that can be attached and detached to the dc output equipment flexibly. In previous researches, stable criteria based on the impedance ratio conditions were proposed. These criteria can treat one-way power transfer from a power source to a load. However, if a system has equipment that can change the power flow direction such as secondary batteries, it is difficult to apply the impedance-based conditions. We studied a stabilization method using a passivity-based stability criterion in a residential dc system. Positive Feed-Forward (PFF) control was adopted to satisfy the passivity-based stability criterion. Experimental results show that the input bus voltage of a buck converter was stable when it satisfied the passivity condition.

Power electronics devices can cause serious electromagnetic interference (EMI) because of their high-speed switching. Such switching disturbances then propagate along power cables, which can act as antennas to radiate noise. Typically, a passive filter composed of inductors and capacitors is used to reduce EMI. However, when a power cable is connected to the passive filter, the cable acts as a distributed constant line that worsens the attenuation characteristic of the passive filter at the anti-resonant frequencies of the cable. This study proposes a solution to this problem in the form of an active common-mode filter that uses a high-speed amplifier. Experimental results show that the proposed filter improves the attenuation characteristics of the passive filter and reduces radiated noise from the cable over a wide range of frequencies from 10MHz to 100MHz.

The magneto rheological elastomer (MRE) is composed of silicone elastomers and ferromagnetic powders that are responsible for its ferromagnetic and viscoelastic properties. The shape and the stiffness of the MRE change depending on the magnetic field. Therefore, it is expected to be used for artificial muscle or damping material. We developed a coupled analysis method by combining the moving particle semi-implicit/simulation (MPS) method with the finite element method (FEM) for the design of the MRE actuator. However, this method does not take into account a rigid body. Therefore, when analyzing the coil embedded in the MRE, it was difficult to calculate parameters such as the coil rotation and position. Therefore, this paper presents a numerical method for MRE actuator analysis by coupling MPS method with FEM to arrive at a calculation method for a rigid body. The numerical algorithm is described, and the calculated results are shown.

This paper proposes a novel V/f control method for interior permanent magnet synchronous motors (IPMSMs) in order to achieve maximum torque per ampere (MTPA) control without motor parameters such as d-q axis inductance and flux linkage of a permanent magnet. V/f control does not require either information of rotor position or the motor parameters in order to construct the control system. However, the conventional MTPA control method requires the motor parameters because the control determines the compensation voltage depending on reactive power. On the other hand, in the proposed MTPA control method, a hill-climbing method is utilized. The proposed MTPA control method calculates the compensation voltage depending on the output current in order to track the MTPA operation point without the motor parameters. The validity of the proposed method is confirmed by the experimental results using a 3.7-kW IPMSM. The experimental results indicate that the magnitude of the phase current decreased by 61% at the rated speed. Furthermore, the proposed MTPA control method is effective regardless of the magnitude of the load torque.

In this paper, an analytical method using the impedance for calculating rotor eddy-current losses caused by inverter carrier harmonics in a permanent magnet motor is investigated. With respect to different types of motors, the accuracy of the proposed method is compared with direct calculation by finite element analysis (FEA) using pulse width modulation (PWM) voltage waveforms. First, the two-phase and three-phase current circuits are investigated for calculation of the impedance. Next, impedance and eddy-current losses of six types of motor are calculated in order to investigate the influences of the motor structure and stator magnetomotive force (MMF) on the rotor eddy-current losses. Because the magnetic saturation of the motor core decreases the accuracy of the calculation, an estimation method is proposed that takes the magnetic saturation into account in order to improve the accuracy. The validity of the proposed method is verified by a comparison with the results of direct calculation by FEA using PWM voltage waveforms. Moreover, the effect of the calculation time reduction obtained by the proposed method is also compared with the case where it is calculated directly by FEA.

This paper proposes a bi-directional isolated DC/DC converter for the battery charger and discharger of Electric Vehicle to reduce the power loss under light load condition. The proposed DC/DC converter consists of two full-bridge inverters, an isolated transformer, and a boost reactor, and provides bi-directional transmission, buck-boost conversion, zero - voltage - switching and reactive power suppression. Two power semiconductors of the inverter in the rectification side are turned off to block a reverse current, which increases the power loss under light load condition. The amount of phase shift in the two full bridge inverters are controlled continuously and simultaneously seamless power transmission. The 400V-3.5kW experimental system exhibits stable bi-directional buck-boost conversion and seamless transition between the charging and discharging modes, while suppressing the reactive power. Moreover, the proposed DC/DC converter reduces power loss by 67.5W under light load (240W) condition, compared with the conventional control.

We have designed and developed a tri-stable rotary solenoid actuator, which has a simple structure and simple operation. The plunger has two stabilities at the extreme positions along an angular stroke and the third stability at the center of it. The third has been successively achieved by using the electromagnetic restoring torque, which is designed to be larger than the inertia torque. The dynamic characteristics were determined by utilizing an optimal design program that is specially constructed based on the response surface method in order to design the coil winding and the power supply for the coil excitation. A prototype solenoid was constructed and used to verify the tri-stable motions and accuracy of the previously constructed design program.

Our research focuses on smart grid, robust control, motor control, motion control and networked system control