In this paper, a motion recognition method that uses haptic information of a human hand is proposed. The haptic information is measured by a master/slave robot hand. This robot has five degrees of freedom, and a bilateral control of the robot is implemented. An operator wears on the master robot hand and operates an object through the slave robot hand. A motion database is prepared to contain haptic information as reference vectors concerning eight kinds of human motion. Then, the motion database utilizes cosine similarity to distinguish the human motion from haptic information acquired by the master robot. Furthermore, the expansion and contraction of time axes are corrected by dynamic programming matching, and combination motion is consequently recognized. The validity of the proposed method is experimentally confirmed.

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The recent years have seen an increasing trend in the cumulative installed capacity of distributed generation. As a result, voltage management may become difficult in existing power distribution systems in the future. STATCOM (STAtic synchronous COMpensator) is a promising option for solving this problem because it can control reactive power rapidly and continuously. For a distribution system, STATCOM needs to be pole-mounted to realize its low cost. However, a transformer for STATCOM is large and heavy, and hence, it is difficult to install a STATCOM on a distribution pole. We adopt a transformerless STATCOM to reduce STATCOM size and apply SiC devices that show a low-loss performance to obtain a more compact and efficient STATCOM. There are a large number of circuits available for STATCOM and there has been considerable research on the performance comparison among these circuits. However, these comparisons were drawn under different conditions of switching frequency and level number of circuit. In addition, these comparisons do not encompass the application of SiC devices. We made an equitable comparison for a 100kVA pole-mounted STATCOM using SiC devices. We discuss the performance and characteristics of each circuit in terms of efficiency and volume.

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A practical-scale hybrid wind turbine generating system is developed for generating a constant output power even when the wind velocity fluctuates. The system consists of a wind turbine synchronous generator, a rectifier, a current-source thyristor inverter, a synchronous generator driven by a prime mover, and a duplex reactor. A high-quality output voltage waveform is always obtained from the system, which has a very simple configuration. Experimental results show the feasibility of the system. A model of the system is also developed to predict the dynamic performance when the system conditions such as the wind velocity and load are changed, and good agreement between simulated and experimental performances is observed, confirming the validity of the dynamic model.

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The trend in drives for dump trucks used in the mining industry is shifting from mechanical drives toward electric drives because of the increasing efficiency of mining operations. Therefore, we developed an AC drive system for 190-ton-payload mining dump trucks. A hill start is one of the important abilities required of mining dump trucks. During a hill start, it is necessary for the trucks to output large torque in a low-speed range. However, vector control was shown to have trouble outputting large torque in this range. Therefore, we developed a method for controlling large torque in the low-speed range of induction motors to improve vector control. We evaluated the efficiency of our method by performing simulations and experiments.

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This paper presents a real-time electro-thermal simulation system as a novel method of estimating the junction temperature of power semiconductors in real time. The proposed system consists of a real-time computer, a host computer, and an actual motor drive system consisting of a permanent magnet synchronous motor, a three-phase IGBT inverter, a controller, and an FPGA board.
The authors use an FPGA board with a clock of 50 MHz to measure the output voltage of the inverter, because the sampling rate of the real-time computer (18 kHz) is not fast enough to accurately measure the output voltage of the inverter. The measured output voltage is used to reconstruct the PWM signal in the FPGA board which is then transferred to a real-time computer. The instantaneous power losses and the junction temperatures of the power semiconductors are calculated in the real-time computer in which the thermal circuit network is implemented by using the load current and the reconstructed PWM signal. The simulation results were in very good agreement with the experimental results. Junction temperatures of power semiconductors can be estimated under actual operating conditions using the proposed real-time electro-thermal simulation system.

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In the laminated core of transformers, motors, etc., each electrical steel sheet is usually insulated in order to reduce the eddy current loss. It has been reported that the insulation is not necessary in such a laminated core in some conditions. However, few studies have been performed in quantitative and systematic examination of the relationship between the insulation and eddy current. In this study, the eddy current losses of a core made of SPCC (colded rolled steel sheets) of different widths with and without insulation under various conditions are analyzed by using the finite element method (FEM) and considering the contact resistance. The equivalent circuit of a laminated core without insulation is presented, that can be used for determining the necessity of insulation. It is shown that the increase in the eddy current is affected by the ratio of the resistance of steel to the contact resistance. An experimental investigation is also carried out.

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This paper proposes a method of accurately estimating the state of charge (SOC) of rechargeable batteries in high fuel efficiency vehicles, such as hybrid electric vehicles (HEVs) and electric vehicles (EVs). Despite the importance of accurately estimating the SOC of batteries to achieve maximum efficiency and safety, no method thus far has been able to do so. This paper focuses on the simplification of a battery model, estimation of time-varying battery parameters, and estimation of SOC under measurement noises. To address these three issues, a model-based approach that uses a cascaded combination of two Kalman filters, “Series Kalman Filters, ” is proposed and implemented. This approach is verified by performing a series of simulations under an HEV operating environment. The ultimate goal is to design a state estimator capable of accurately estimating the state of any kinds of batteries under every possible user condition.

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Short-circuit faults in windings due to the deterioration of insulation is one of the most common faults in motor drive systems. An easy and effective fault diagnosis method is urgently required to ensure a highly reliable operation. This paper proposes a novel method for the diagnosis of short-circuit faults in stator winding inside a low-voltage induction motor without removing the rotor, by performing an impulse voltage test. As the rotor does not need to be removed from the motor in the novel diagnosis method, the method can be applied for practical use. In this study, first, several impulse voltage tests are carried out on the stator windings of motors. Second, the values of two features that represent the characteristics corresponding to the condition of the motor are calculated, and it is found that the shape of the feature distribution does not depend on the rotor position but on the condition of the winding. Third, the distance between the feature distribution for the healthy motor and features obtained from a target motor is calculated. On the basis of this distance, the quality of stator winding inside the induction motor is determined. The effectiveness of the proposed diagnosis method is verified by performing experiments that involve several motors with healthy and faulty windings.

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The flux-modulating synchronous machine (FMSM) is a new type of multipole SM with nonoverlapping concentrated armature and field windings on the stator. This paper compares output characteristics of two FMSMs through finite-element analysis (FEA) and experiments. In both the FMSMs, attachment positions of the armature and field windings are swapped. To determine the reason for discrepancies in their output characteristics, unsaturated inductances were calculated using a d-q equivalent circuit. In addition, the calculated results of the inductances were confirmed by visualization of leakage fluxes using the FEA. The results of the study show that the synchronous inductance can be reduced by attaching the armature winding to the air-gap side of the stator teeth and that its reduction leads to an increase in output power.

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In this study, we investigate the method of accurate characteristics calculation for salient-pole synchronous machines assisted by permanent magnets. First, the operating principle of the machines is investigated by using both finite element analysis and a simple magnetic circuit. Then, the theoretical expression of the assist effect of the permanent magnets is derived from the magnetic circuit. Finally, the measured and calculated results are compared in order to confirm the validity of the proposed calculation method. It is clarified that the load characteristics of the proposed machine can be accurately estimated from the no-load and short-circuit characteristics of the conventional machine without permanent magnets, and the size and magnetization of the inserted permanent magnets.

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This paper presents a high-performance V/f control of an induction motor for precise speed operation, which is based on the vector control theory. A linear model is derived for analyzing the system stability, and the effect of a low-pass filter is discussed. The effectiveness of the proposed system and validity of the analysis have been demonstrated by simulations and experiments.

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A three-phase voltage-fed converter operated by a two-phase PWM scheme offers relatively high ac voltage, low switching times, and low switching losses in comparison to that operated by a three-phase PWM scheme. However, the harmonics involved in the ac-side voltages and currents produced in the two-phase PWM scheme are distributed over a wide frequency range, which can be a significant drawback depending on its applications. To overcome this problem, the authors propose a novel two-phase PWM scheme in which the harmonics appear in a frequency range as narrow as that in a conventional three-phase PWM scheme.

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