Serious defects in metal piping systems used in factories, power stations, and similar facilities can cause serious accidents. Regular inspections for metal pipework are therefore important. However, all conventional non-destructive inspection (NDI) methods are often time-consuming and inconvenient. To address this issue, we propose a simpler and more innovative inspection technique based on electromagnetic waves.

In this study, we introduce a new, highly sensitive NDI method for metallic pipework using the `polarization' properties of electromagnetic waves. This method utilizes the ability of a metal tube to act as a circular waveguide, radiating electromagnetic waves along its length. A key feature of this approach is that the transfer function changes significantly when the polarization direction of the electromagnetic waves at the transmitting and receiving ends is changed. This measurement method enables the detection of disturbances in the electromagnetic polarization caused by reduced wall in metal pipe with high sensitivity. Consequently, it facilitates ground-breaking inspections that quickly and easily detect the presence of defects, such as reduced wall, across the entire metal pipe being measured.

Motion control of automatic train operations requires accuracy in stopping position and flexibility to environmental changes when applied to conventional railway lines wherein adhesion characteristics may exhibit considerable variation because of disturbances such as rain, snow, and fallen leaves. This study focuses on iterative learning-based control for train motion to achieve precise stopping performance, whereby the motion controller updates the reference control trajectory in every train run on the basis of the results of the previous train runs. The proposed train motion controller iteratively learns the feasible maximum deceleration without excessive wheel slip from the running results and actively adjusts the speed profile for the next train run for compliance with the deceleration limits in accordance with the varying adhesion characteristics. Numerical simulations indicate sufficient stop position accuracy during repeated train runs under varying adhesion characteristics and a capability to return to more efficient speed profiles with higher deceleration and shorter running time as adhesion characteristics recover. The proposed method thus facilitates the automatic train operation while enabling flexibility of control under varying environments.

Railway vehicles have been recently employing lithium-ion battery systems aiming at further energy saving, battery-powered running and continuous operations during blackout. Regarding the calendar aging of the lithium-ion battery, the Weibull law-based long-term estimation method has been studied, which deals with only a constant temperature condition. In contrast, we developed a capacity fade estimation method based on the extended Weibull law, which allows conditions such as temperature and state of charge (SOC) to be varied. This method is useful for practical and accurate estimation. We performed accelerated aging tests using test cells of the onboard traction batteries. The test results demonstrated good agreement between the estimated and measured values of battery capacity, thus showing the effectiveness of the developed estimation method.

A train control system detects train positions using a ground devise. Railway companies maintain and renovate the system. On the other hand, if the ground devise fails, then the workers of railway companies will be dispatched to the site to perform maintenance. Hence, it is necessary to secure a certain number of workers. Given that the declining birthrate and aging population pose challenges in securing sufficient workers, it will be necessary to secure labor with respect to ground devices. In this study, we propose a new position detection method that performs position detection on-board to save labor with respect to ground devises. Specifically, first, location information, such as latitude, longitude, and kilometer, is linked to the layout of objects on the track. Second, the method detects objects using a LiDAR sensor installed on-board and then recognizes the layout of the objects. Third, position information is retrieved by matching the recognized layout with the database on-board. Finally, a train position is detected using the position information and relative position between the train and objects. The results of tests using the vehicle indicate the feasibility of the method in recognizing the layout and detecting the train position.

This paper presents design studies on a stator for a high-speed homopolar type permanent magnet motor that can be applied to a super charger for automobiles, and cordless stick vacuum cleaners, among others. The stator of the motor comprises electromagnetic steel cores, permanent magnets and concentrated windings. The rotor is composed of only electromagnetic steel cores without any retaining ring on the surface, thereby offering high mechanical strength suitable for high-speed applications with no increase in manufacturing cost and eddy current loss. However, the homopolar type permanent magnet motor treated in this study tends to have low torque density due to its three-dimensional magnetic circuit inherent to this type of motor. To improve the torque density, the designs of sintered Nd-Fe-B and bonded Nd-Fe-B permanent magnets were investigated from the viewpoints of reduced eddy current loss, higher maximum torque, and less cost. Finally, experimental studies on a prototype of the designed motor showed that the test results are in good agreement with corresponding analytical results. Therefore, the design approach adopted in this study is useful for examining the torque density improvement of the homopolar type permanent magnet motor.

This letter proposes a space vector modulation (SVM) method that reduces computational cost by minimizing vector searches for multiphase inverters in induction motor transmission system (IMTS) drives. This method decomposes the space vectors of the inverter into six fundamental space vectors and calculates their duty ratios, thereby eliminating the need for exhaustive combination searches. Experimental results confirm that the proposed SVM enables effective modulation even during pole-changing operation.

In this study, sliding experiments were conducted using a graphite brush and a copper slip ring. Four sliding speed conditions were tested, and the wear of the positive and negative brushes was measured. The results showed that the wear of the positive and negative brushes exhibited opposite trends with increasing sliding speed.