This paper proposes a torque control method for interior permanent magnet synchronous motors (IPMSMs). The proposed method uses state feedback control based on a new n-t coordinate system and controls the voltage amplitude and phase based on the coordinate system. The t-axis is a tangent line of the constant voltage ellipse, and the n-axis is a normal line of the ellipse. The n-axis current is utilized to place the poles of the transfer function at the desired position and reduce the mutual coupling between the voltage amplitude controller and phase controller. The proposed method realizes a high torque response even under parameter variation for the linear range and over-modulation range of the inverter, including a six-step mode. The effectiveness of the proposed method was verified by simulation and experimental results.

Recently, a bilateral teleoperation system using an electric helicopter as a slave robot has been researched. Although conventional methods utilize a static controller, a non-negligible position/force tracking error is induced by the grand effect. A propeller's angular velocity - thrust force characteristics change depending on the distance between the helicopter and grand due to the grand effect. Therefore, this paper proposes a gain scheduling controller that changes the controller gain depending on the distance between the helicopter and grand. The validity of the proposed controller is verified by experiments.

This paper reports on the experimental validation characteristics of a salient pole synchronous motor with the starting field circuit in contact. The starting characteristics were experimentally evaluated at voltages of 100%, 75%, and 50% using a 1.5kVA salient pole synchronous motor. The signal for pulling into step was applied to the field circuit by using the control module, for all test conditions. The results confirmed the proper pulling into step at 100% of voltage, and the results of the tests at 50% and 75% of voltage revealed that the pulling into step under these conditions becomes stable at the suitable slip condition.

In this study, we consider the demagnetization of magnets due to reverse magnetic field current, in order to find out the cause of local demagnetization of concentrated winding IPMSMs operating in high-temperature environments. It is clarified that the demagnetization part acting on the magnet greatly differs depending on the energized phase. We propose a method for demagnetization evaluation based on 2-phase and 3-phase energization using a test rotor with only two adjacent poles of a multipolar rotor.

This paper proposes an improvement to Taguchi's T-method. In product development, it is difficult to gather sufficient samples at the beginning of the development process. Taguchi's T-method was proposed as a method for constructing an estimation model in such a situation. However, if an outlier exists in the training data, Taguchi's T-method cannot obtain a correct estimation model. This is because Taguchi's T-method uses the least squares. Therefore, in this paper, we propose an improved version of Taguchi's T-method that does not degrade the accuracy of estimation by using a median-median line even for small training samples with outliers. The Effectiveness of the proposed method is confirmed through experiments. We confirmed that the accuracy of the proposed method is superior to that of similar methods.

Nowadays, many passengers rely on transfer guidance systems and their demands for punctuality of trains have become very high. In order to satisfy passengers' requirements for punctuality, it is necessary to establish an approach that can help deternining where delays occur and the type of delay reduction measures to be taken to reduce delays most efficiently. We have established functions to acquire and record the departure and arrival times of all trains in seconds at all stations. Based on these data, we introduce two indices that will be useful in deternining the places where delay reduction measures should be taken and the most effective delay reduction measures. We have applied this approach to the Hanzomon line, which is one of the most congested lines and small delays occur frequently. The results indicate that the proposed approach considerably reduced delays.

In this paper, we demonstrate the experimental evaluation of system feasibility of a wireless sensor network system powered by a hybrid energy harvester inside a reusable vehicle test (RVT). The hybrid energy harvester consists of a solar cell and a microwave rectifier as a passive and an active powering method, respectively. Basic characteristic measurement of the hybrid energy harvester under line-of-sight conditions and multi-sensor operation under non-line-of-sight conditions were carried out using the real RVT which is covered by an aeroshell.

Short-circuit faults in windings are among the most common faults in motor drive systems and occur when the insulation deteriorates. An easy and effective method for diagnosing such types of faults is urgently required to ensure a highly reliable motor drive system. In particular, a method to identify short-circuit faults can be very useful. There are two techniques used to construct motor windings: concentrated and distributed winding. This paper proposes a method for identifying the fault point at which the short-circuit fault is located in the concentrated winding of a motor. This method involves the measuring of the change in the magnetic field generated by a winding. The difference in the magnetic field before and after the occurrence of a short-circuit fault was theoretically predicted. Further, a numerical analysis was conducted to confirm the predicted change in the magnetic field. In addition, a small magnetic field sensor was developed to measure the magnetic flux density emanating from a winding. Finally, the effectiveness of the proposed method was experimentally verified using the magnetic field sensor.

This paper proposes a new current control method for permanent-magnet synchronous motors with double independent three-phase windings (DIW-PMSMs). It is well known that stable and fast current control of DIW-PMSMs is very difficult because of the inevitable magnetic coupling between two windings. Many methods suffer from slow and/or low performance when trying to achieve stable control. The proposed method takes a new approach that first extracts two fast and two slow mode-currents in the dq synchronous reference frame, and then controls four mode-currents independently and stably. The method succeeds in stable and fast current control of the motors. It can be applied even in cases where 1) independent windings have small leakage coefficients (i.e., large coupling coefficients), and 2) motor parameters and current commands associated with each winding are widely different. The effectiveness and usefulness of the proposed method are verified though simulations under harsh conditions.

A conventional medium-voltage large-capacity bidirectional chopper used in a battery energy storage system for dc electric railways is equipped with a heavy and bulky inductor for current smoothing. This paper presents the experimental verification of a bidirectional chopper with an auxiliary converter for the purpose of reducing the size and weight of an inductor. The auxiliary converter is formed by the cascade connection of multiple single-phase full-bridge converter cells. Applying the so-called “phase-shifted PWM” to each of the cells can reduce the voltage step across an inductor and increase the ripple frequency, resulting in a significant reduction in size and weight of the inductor. This paper discusses the operating principles and control method of the bidirectional chopper, followed by experiments using a 150-V, 2-kW down-scaled model.

Efficient planning of long-distance rail services requires appropriate forecasting of passengers' demand fluctuation based on historical ridership records. However, this forecast is difficult, because the records consist of a mixture of passengers' demand variations. An effective approach for achieving an appropriate forecast is to decompose it into several independent demand variation components and forecast each of them. This study applies the independent component analysis to decompose the fluctuations into several additive variation components. Then, a forecasting method for passengers' demand fluctuation is developed using the calendar structure and event venue capacity.

The configuration of a self-excitation circuit for a wind power generator using an alternator is presented. The proposed circuit applies a three-phase double voltage rectifier circuit with a triple voltage function. As a result, it is possible to establish a voltage at a lower rotation speed than in the conventional self-excitation method. The validity of the proposed circuit is demonstrated using experiments.