This paper presents novel criteria for the reluctance torque utility of permanent magnet (PM) motors. The criteria can be quantified by the PM flux linkage Ψ_p of stator phase windings, and current I, as well as the direct- and quadrature-axis inductance L_d and L_q, respectively. Through both theoretical formulae and experiments, it is proved that a motor with large Ψ_p can utilize little reluctance torque even if the salient-pole ratio L_q/L_d is over 2.0. In such a case, the large salient-pole ratio only leads to an increase in iron loss, and hence a decrease in motor efficiency. The proposed criteria help one to understand the properties inherent in each motor, and also indicate that, in the above case, selecting the rotor geometry with less saliency can improve the efficiency. Results are given for two kinds of PM motors; one is a 4-pole Nd-Fe-B magnet motor with P_N = 0.6kW, n_N =3600min^-1, Y-connection; the other is a 6-pole ferrite-magnet motor with P_N = 0.2kW, n_N =1080min^-1, Y-connection.

In dense traffic railway networks, trains may often slow down or stop between stations owing to previous train delays. If preceding train trajectory can be predicted, energy-efficient driving can be achieved by suppressing unnecessary speed changes. In this paper, we propose an algorithm to find energy-efficient driving considering fixed-block signalling (FBS) system by using dynamic programming (DP). DP is suitable for use because it can optimize the control inputs with discrete and state constraints. In this paper, we discuss energy-efficient driving by considering a FBS system using some case studies of simulation. In the simulation, we examine a technique to drive an express train in an energy-efficient way when the preceding local train is running toward the station with passing loops. The results show that the proposed method can derive complex speed profiles for energy-efficient driving and the train can be operated with a maximum reduced energy consumption of 8.3%.

We developed a high speed induction motor, which has a high intensity rotor with a solid core and copper conductor. This paper describes the electrical characteristics of the high speed induction motor by comparing the experimental and analysis results. Then, we classify the losses into no-load iron loss and stray load loss. Based on the results, we reveal that the iron loss accounts for 74% of the total loss, the inverter harmonics have a small effect on the iron loss, and the harmonic factor of alternating current losses in the primary winding have an influence on the performance of the high speed motor.

Actuators that have characteristics such as light weight, high thrust to weight ratio, and force controllability are desirable for applications such as finger robots and power assist suits. Recently, an indirect force control method using an ultrasonic motor (USM) and a spring has been attracting considerable attention because this method has the potential to satisfy all of the desirable characteristics, namely light weight, high thrust to weight ratio, and force controllability. The USM controls the length of the spring, and the tensional force of the spring is indirectly controlled by the length. As the resonance frequencies of indirect force control systems are low due to the springs, it is difficult to select a high feedback gain. This research therefore proposes a novel resonance ratio controller for indirect force control systems. The validity of the controller is verified by simulation and experiment. The overshoot ratio of the conventional controller is more than 10%, while that of the proposed controller is around 1%, when the rise time is 0.30 s.

At present, it has become necessary to reduce the size of electron beam irradiation devices, which are utilized in many industries. This paper investigates a high step-up isolated DC-DC converter. This converter has the 5-stage Cockcroft-Walton circuit with an inductor in the secondary side. The inductor prevents a drastic changes in the transformer current and produces peak value of the output voltage with the LC resonance of the secondary side. In this paper, resonance point tracking control is proposed for the converter. The proposed control utilizes the LC resonance characteristics of the converter. The LC resonance in the secondary side is tracked by the proposed control regardless of load change. Therefore, the distortion of the transformer current is suppressed and the peak value of the output voltage is maintained by the resonance point tracking control. In addition, the validity of the proposed control is experimentally verified by demonstrating its transient behavior under load fluctuation.

In recent years, to increase transportation capacity, new intelligent signaling systems such as moving block have been proposed and put in operation. In addition, research and development on prediction control are now ongoing to decrease the propagation of train delay. Hence, it is important to estimate the effects of new signaling systems because replacement of current signal system may incur high costs. In this study, we developed new functions on a train operation and passenger flow simulator to analyze the activity of trains under moving block and prediction control, taking into account the drivers' operational requirements. We applied the simulation system to an actual commuter line, aiming to evaluate the quantification of effects of moving block and prediction control.

This paper proposes a control method that compensates for a system with time delay by predicting the future states of the plant. The proposed method contains a state predictor that predicts the future values of a system. Furthermore, the proposed method also considers the uncertainty of the model in terms of the modeling error, which might cause the predicted value to degrade the performance of the system or even destabilize it in the worst case. The disturbance in the remote plant is explicitly considered and is compensated for by locating a feedback controller in the remote side. This paper described the proposed control method based on model-based predictive control that considers modeling error. The stability of the proposed system is analyzed, and performance of the method is evaluated in comparison with conventional methods using numerical simulation results.

Wireless power transfer (WPT) via magnetic resonance coupling has been gathering attention because of its capability for highly efficient mid-range transmission and robustness to misalignment between the transmitter and receiver. Although the transmitting efficiency and charging power are determined by the coil parameters and load condition, their characteristics can be expressed based on the voltage ratio between the transmitter and receiver sides. In this paper, WPT systems are classified into four categories based on the design possibility and controllability of the system voltages on the transmitter and receiver sides. The design strategies of the system voltages are proposed, to give the priority operations for efficient power transmission and a stable power supply, considering power requirements and efficiency limitations. The experiments demonstrated the feasibility of the proposed method.

Commercial operation of type Kiha-E200 hybrid train started from 2007 in Koumi-line. Series HB-E300 has been operated as ‘Resort Shirakami’ rapid service in Ouu-line and Gono-line. Because of charge and discharge in the rapid service, HB-E300 expected to have shorter life time of storage batteries than Kiha-E200 according to result of its investigation after five years from the operation start. To check degradation of the batteries and develop optimal charge and discharge control, data collection in commercial operation was carried out and good performance of the control was confirmed.

The EPS algorithm consists of torque assist control and compensation control for vibration suppression. It is considered that there is a limit to the improvement in the response of steering angle control necessary for automatic drive. Therefore, this paper proposes the new compensation control based on one-input two-outputs sliding mode control.

This paper proposes a new power decoupling method for a high-frequency cycloconverter which converts the single-phase line-frequency ac input to the high-frequency ac output directly. The cycloconverter consists of two half-bridge inverters, two input filter capacitors, and a series-resonant circuit. The proposed power decoupling method stores the input power ripple at double the line frequency in the filter capacitors. Therefore, the proposed method achieves a unity power factor in ac input and a constant current amplitude in the high-frequency output without any additional switching device or energy storage element. This paper theoretically discusses the principle and operating performance of the proposed power decoupling method, and the viability is confirmed by using an experimental isolated ac-to-dc converter based on the high-frequency cycloconverter. As a result, the proposed power decoupling method effectively improved the displacement power factor in the line current to more than 0.99 and reduced the output voltage ripple to 4% without any electrolytic capacitor.

In recent years, the use of induction-heating systems has increased and wireless power transmission (WPT) systems have been discussed. These applications are installed close to a human body. Therefore, it is important to discuss the effects of alternating magnetic fields and to evaluate electromagnetic interference. This paper discusses the design procedure of a magnetic field generator to evaluate the electromagnetic interference at 85kHz which is being studied in WPT systems for EV and HEV. The magnetic field generator presented in this paper consists of a single-phase inverter circuit that uses SiC-MOSFETs and an air-core inductor that is used as the coil for generating a magnetic field. In particular, this paper shows that the coil used for generating magnetic field needs to reduce the winding voltage to generate higher magnetic flux. In addition, this paper presents the design procedure of the proposed coil structure which can satisfy some limited conditions. The experimental results of the proposed system rated at 82kHz and 100A are presented.

This paper describes the electrical characteristics of a new brushless doubly-fed AC Machine (DFM) system that is referred to as the rotary converter generation system (RCGS). The RCGS consists of two generators (main generator and sub generator) and a power conditioning system located in the rotor of the main generator. We show three energy flow characteristics of the RCGS. First, total output power is the sum of the output powers of the main generator and sub generator. Second, the operating range of the RCGS is the same as that of the DFM. Finally, the ratio of the output powers of the main generator and sub generator is determined by the ratio of their pole numbers. Additionally, we calculate the losses of the RCGS. The efficiency of the RCGS is almost as high as that of the DFM. We create a prototype of a 4kW RCGS and measure electrical characteristics. The flows of the prototype are the same as theoretical energy flows.

This paper discusses a power decoupling method using fly-back converter with discontinuous current mode (DCM) for PV micro-inverters. The proposed converter consists of a fly-back converter, voltage source inverter (VSI), and small capacitor. The proposed method does not require any additional component or complicated control for power decoupling. From the experimental result, the second-order harmonics of the PV input current is reduced by 97%, in comparison with that in the current continuous mode (CCM).

Haga laboratory focuses on power electronics, energy storage applications, and motor drive systems. Haga laboratory challenges creation of new technologies focusing on the circuit topology of power electronics. The effectiveness of the proposed method created by this laboratory is clarified by experiment. Haga laboratory also educates students who are technically, physically and mentally strong.