Electronics and Communications in Japan最新文献

This paper proposes an analytical calculation method of frequency characteristics of DC input impedances of an IPM motor drive system for design and stability analysis by the impedance method. The proposed method is based on an averaged frequency model linearized at an operating point. The developed small-signal model considers control principles and mechanical perturbations. It is an analog and digital mixed model which is controlled by a digital signal processor system. Analysis examples of frequency characteristics for the impedance method by the proposed method are investigated and validated analytically and experimentally.

In this study, iron oxide thin films are prepared under various heat treatment conditions, and their crystal structures and moisture-sensitive characteristics were evaluated to clarify the usefulness of iron oxide thin films as humidity-sensitive materials for humidity sensors. In addition, the possibility of a humidity sensor with a wide dynamic range was investigated by evaluating the relationship between the film thickness of the iron oxide thin film, the electrode width of the device, and the humidity-sensitive characteristics. As a result, it was found that the crystal structure of α-Fe2O3 exhibits relatively good humidity sensitivity compared to other crystal structures, and that the sensitivity to humidity can be adjusted by appropriately selecting the electrode width and film thickness of the device. Therefore, the α-Fe2O3 thin film may be useful as a moisture-sensitive material for wide dynamic range humidity sensors by appropriately adjusting the film thickness and electrode width.

This study aimed to develop teaching materials for circuit design and fabrication for elementary school students, and conduct workshops oriented to engineering. First, the content of the circuit design workshop was discussed and it was determined that a connection-focused design would be appropriate. Second, we examined the issue of existing teaching materials. Many of the existing kit materials were not suitable for learning circuit design as it was already completed. In addition, many of them required soldering work, which was too difficult for elementary school students. Hands-on materials that allow students to construct circuits through trial and error were suitable for learning circuit design. Therefore, we developed design and fabrication support materials using a 3D printer and conductive tape. Next, we provided workshop opportunities using developed material, with the theme of “making light-up cards,” wherein elementary school students worked on designing the layout of the components and fabrication. Consequently, students’ conceptual understanding of the connection was improved. All students were able to complete the circuit, with high self-evaluations of satisfaction and understanding suggesting that the activity was engineering-oriented.

In recent years, with the development of IoT, research and development of wireless sensor networks for monitoring has been advanced to monitor the condition of various devices in railway vehicles and notify train crews. In the operation of railway vehicles, the composition may be changed at stations by coupling and decoupling, and it is necessary to set up inter-vehicle wireless network considering them. Therefore, to transmit sensor data in railway vehicles, we propose an autonomous configuration establishment method of wireless network for railway vehicles considering coupling and decoupling.

Femtosecond double optical pulse experiments with nanosecond time delay were conducted in air. Terahertz pulses were generated from laser plasmas produced by the irradiation with the main pulses on shockwave excited by the pre-pulse illumination. Intensity of the terahertz pulses depends on the time difference Δt and relative position Δy between the pre- and main pulses. We found a characteristic dependence of the intensity of the terahertz pulses on Δy at a longer time delay, Δt = 14.7 ns, which has two maxima while only one maximum was observed when delay times were at and shorter than 9.7 ns. The results are discussed taking into account air density distribution of the shockwave. The terahertz emission spectroscopy shown here can be a useful technique for investigating density structure and its time variation of shockwave with high temporal resolution.

In the fields of medical and sports science, it is required to evaluate muscle activity qualitatively and quantitatively. Currently, mechanomyogram (MMG) that can reflect the mechanical activity of muscle fibers is attracting attention. The purpose of this study is to develop a sensor that can measure MMG during exercise. In this study, a small and flexible MMG sensor using P(VDF/TrFE), which is a piezoelectric polymer material, spun into nanofibers by the electrospinning method has been fabricated and evaluated. By the fabricated electrospinning equipment and the obtained fabrication conditions of the nanofibers MMG sensor has been fabricated by using piezoelectric polymer fibers. By using nanofiber nonwoven fabric for the sensor element, the flexible sensor has been realized. In a sound wave reception experiment assuming MMG measurement, the P(VDF/TrFE) nonwoven fabric element showed that the element detected the sound pressure. Additionally, MMG during isometric contraction and pedaling motion has been measured using the fabricated sensor. The results show that the proposed sensor is effective for measuring MMG during exercise.

We propose a modeling framework for automating batch processes operation. Batch processes are often controlled by PID controllers, where engineers manually regulate their parameters and temporal patterns of reference signals. Therefore, it takes a long time for optimizing these parameters and temporal patterns. A possible solution for this is to apply so-called Model Predictive Control (MPC) technology to the tuning. Here, batch process dynamics depend on the types of products and of equipment, thereby forcing engineers to construct and maintain multiple models that correspond to the number of combinations of product types and equipment types. Thus, batch process modeling is a time-consuming and complicated task. To solve this problem, we propose a modeling framework; about a modeling target, the part applying commonly and parameters can be decided in advance are constructed by mathematical models, and the part that required experimentation for designing or tuning are constructed by machine learning models. We expect this framework can improve estimation accuracy and suppressing the number of model construction by separating model construction and combining the mathematical and machine learning models. In our simulation, we confirmed that our proposed model can suppress prediction error (RMSE) of reactor temperature under 1 K. Furthermore, an optimization algorithm with our model can find a temporal pattern of a reference signal so as to reduce control error of reactor temperature under 1.99 K.

To properly maintain and manage track surfaces, the amount of collapsed settlement of a ballast bed must be determined. However, high maintenance costs make it difficult for railway operators to fully maintain and manage track surfaces. Therefore, we propose a method of estimating the shape of the ballast bed using Dense Inverse Search (DIS) optical flow in images captured using a camcorder, which is inexpensive. This paper describes the outline of the method, an evaluation of its accuracy through simulation and model experiments, and the results of applying the method to actual images captured.

Respiratory rate (RR) is known to be a more accurate predictor of clinical deterioration than other vital signs. However, there were few respiration measurement devices certified as medical devices that could be used in daily clinical settings. Therefore, using a bult-in microcontroller (72×57×12 mm) instead of a personal computer, we developed a portable stand-alone respiration measurement device with minimum workload in computing that can be used for non-contact measurement in 30 s using a Doppler radar. In this study, the problems of respiration measurement using a Doppler radar, such as miscounting of respiratory peaks were clarified, and proposed device with respiratory peaks miscount prevention algorithm achieved high accuracy RR measurement. Clinical testing was conducted on pediatric outpatients of Children's Medical Center, Showa University Koto Toyosu Hospital. The measurement accuracy of the system was confirmed to be comparable to the respiration measurement accuracy of stationary certified medical devices used in hospital, such as capnometers and the chest wall impedance method used in bedside monitors.

The purpose of this study is to realize a grasp force measurement of forceps for robotic surgery systems. Generally, surgical robot forceps is actuated by traction wire, and we have suggested a newly force sensing system by measuring the wire expansion utilizing micro displacement sensors. For measuring the elongation of the wire, the white-light interference principle has been utilized on sensor system, and the sensor consists of a tip-tilted optical fiber, a Fizeau interferometer and a sensor holder. In this report, displacement sensor has been successfully fabricated and mounted onto the wire to measure the elongation of the wire under tension and discussed the experimental results.