Electronics and Communications in Japan最新文献

In agricultural field, compact sensors that can measure both water content and electric conductivity are needed. Focusing on the fact that water content and conductivity depend on soil impedance, our group has been developing a new compact and noise-resistant driving circuit that measured soil impedance by detecting transient characteristics of the voltage obtained by injecting current through the soil and converting it to frequency information. In order to realize agricultural field measurements with sensors using this new driving circuit, it had been necessary to miniaturize the part that detected the output from the driving circuit, but it hadn't been achieved in our previous work. In this research, a microcomputer-based frequency counter was developed to downsize the system for on-site measurement. In general, there are two methods of frequency measurement: direct counting and reciprocal. The direct-counting method is suited for high-frequency measurements, while the reciprocal method is suited for low-frequency measurements. The developed frequency counter could measure with an error of 0.005% over the assumed frequency range by switching between those two measurement methods according to the measured frequency. Using this driving circuit and frequency counter, we measured the model soil and succeeded in capturing changes in water content as changes in impedance.

We have developed tactile sensor systems for next-generation robots. To install a large number of tactile sensors, we have proposed micro electro mechanical systems-large-scale integration (MEMS-LSI) integrated tactile sensors. The integrated device has the following features: capacitive type three-axis force sensing, embedded diode-based temperature sensing, signal processing for sensing data digitalization, and event-driven response for efficient serial bus communication. This paper demonstrates a sensor array system as up-to 40 integrated tactile sensors which are connected on one bus line. After acquiring the sensing data from the sensor array system, we applied a machine learning technique for target object judgment. The objective of the judgment is to classify the targets into normal object and abnormal object. With the sensor array system, data preprocessing and tuned Recurrent Neural network (RNN)/Long Short-Term Memory (LSTM) neural network models, we achieved high-accuracy, high-precision, and high-recall scores for the experiment of the judgment.

This paper addresses a pressure sensor for body pressure measurement. Many pressure sensors have been developed for disease treatment in the medical field. However, these sensors require inserting electronic components and other sensor elements via surgical operations, so the measurement physically burdens patients. Hence, we proposed a needle-type pressure sensor using MEMS (Micro Electro Mechanical Systems) cantilever. The sensor has a needle part with a thin membrane on the tip and is filled with incompressible fluid inside. The fractional resistance of the built-in piezoresistive cantilever varies according to the pressure change applied to the needle tip. We can measure body fluid pressure with minimal surgery by inserting a simple needle into the target organ. Because the fabricated sensor responded to pseudo-body pressure changes, it was suggested that the fabricated needle-type pressure sensor could detect pressure inside the body.

This paper presents a capacitor-voltage-balancing control scheme for an isolated medium-voltage AC-DC converter using level-shifted pulse width modulation (PWM) control of a modular matrix converter (MMxC). The proposed isolated AC-DC converter is composed of the primary MMxC with level-shifted PWMcontrol, high-frequency transformer, and secondary H-bridge circuits. The high-frequency transformer of the proposed circuit can be downsized because the level-shifted PWM control scheme makes the rated frequency of the high-frequency transformer equal to the switching-frequency. The proposed capacitor-voltage-balancing control can compensate for the capacitor voltage imbalance of the MMxC using the positive-sequence and negative-sequence circulating-currents with a power supply frequency and high-frequency voltage. In the proposed control system, the three feedback control systems with DC control variables can be developed to compensate for the capacitor voltage imbalance. The effectiveness of the proposed capacitor-voltage-balancing control scheme and the control systems is verified by experiments using a 200 V, 5-kW laboratory prototype.

In this paper, we propose data-driven control for the case of that the structure of the ideal controller is unknown. In this case, it is natural to implement FIR typed controller. Here, we utilize FRIT for the case of FIR typed inverse controller. In general, FIR might have unnecessarily large number of its taps. To prevent it, we also utilize LASSO regression so as to realize FIR typed inverse controller in as less numbers of the tap as possible. Moreover, we also utilize data-driven prediction to determine hyper parameters required in LASSO regression. The validity of our proposed method is verified by using experiments.

In this paper, input-oriented virtual internal model tuning (VIMT) is expanded to non-minimum phase systems. Proposed method can tune the feedback controller and the desired transfer function. Compared to Fictitious Reference Iterative Tuning (FRIT), the proposed method can realize good controllers even when the time constant of the desired transfer function is small. The validity of the proposed method is verified via numerical simulation.

In this study, in an electret capacitor sensor (ECS), which is an electromechanical exchange device consisting of an electret sandwiched between two electrodes, ridges as spacers and grooves as gaps were formed in the PTFE (polytetrafluoroethylene) layer of the insulating electrode by laser ablation. The ECSs were then fabricated using PTFE electrets, and the charge retention and airborne ultrasonic wave transmitting and receiving characteristics were investigated. The charge retention characteristics of the ECS with laser-patterned insulating electrodes were slightly lower than those of the silica-aggregate electret. As the thickness of the insulating layer increased or the groove width decreased, the transmitting and receiving sensitivity increased significantly and then peaked and degraded at the measurements of transmitting and receiving. The ECS with the highest peak sensitivity obtained by laser patterning had a bandwidth comparable to that of the conventional ECS with silica aggregate electret, but the peak sensitivity was improved by up to 8 dB. Therefore, laser patterning could contribute to the improvement of ECS performance.

A wrist-watch type biosensing system for real-time sweat lactic acid (LA) monitoring was fabricated and tested. The system consists of a microfluidic LA biosensor, a carrier-flow supplying device, and a sampling device for transporting whole secretions at the skin surface to the biosensor by continuous flow of phosphate-buffered saline (PBS). The perfusion test of PBS onto the skin surface by using the sampling device resulted in less than 1% leakage frequency at the collection site. The carrier-flow supplying device was able to feed PBS regardless of the body angle. When the subject wearing the device performed resistance training (lateral raise, 20 repetitions, 12.5 kg dumbbells), the LA secretion increased from 2 µg/cm²/min to 16 µg/cm²/min in response to the exercise, and then recovered to the baseline. The setup time for the measurement was less than 60 s. This indicates that the wrist-watch device can readily measure LA dynamics on the skin surface under conditions of the subject.

This study aimed to test the efficacy of a mint-flavored mouthwash when it is used at bedtime for subsequent sleep in a field study setting, using a wristwatch-type heart rate (HR) monitoring devise. Using a within-subject experimental design, twenty healthy adults used three types of mouthwash having a different intensity of mint sensation (or water as a control) per one experiment night just before going to bed at their home environment, in a counterbalanced order. As for results, irrespective of the intensity of mint-flavored mouthwashes, the subjective score for “fatigue” and “refreshing” before sleep was decreased and increased, respectively. In addition, although a significant inhibition of HR decline in the sleep initiation period (0–30 min after bedtime) was observed with the use of mint-flavored mouthwashes compared with the control, the trend reversed subsequently as HR trended lower than for the control during 2–6 h after the bedtime. These findings suggest that the using mint-flavored mouthwashes at bedtime induces a positive mood before sleep and may improve physiological sleep. Moreover, this study illustrated the possible application and significant advantage of the use of wristwatch-type HR monitoring devise in a context of field study.

In this study, we developed a capacitive seating analysis sensor using a conductive textile for evaluating a Seating Motion. Physical burden on caregivers is a common problem at nursing care sites. Developing long-term caregiving skills can help reduce the physical burden on amateur caregivers. Several quantitative evaluation studies have focused on the skills of caregivers. However, such evaluation is highly expensive and require huge area because it involves the use of motion capture systems with several 3D cameras for dynamic motion analysis. In our previous study, we developed a conductive textile sensor for measuring the seating position of a care recipient in a wheelchair. The sensor could measure either seating body pressure or distance between the buttocks and the seat. The system can measure the care recipient's motion without requiring any motion capture system. We recommend using the sensor to evaluate the skills of caregivers; the sensor output can be used to determine the seating speed of the care recipient on the chair. Herein, we report the validity of the measurement system comprising a conductive textile–based capacitive seating analysis sensor for evaluating seating in nursing care.