Satoshi Sano

A compact and high optical transmission SAW touch screen with ZnO thin-film piezoelectric transducers

A compact and high optical transmission touch screen has been developed using surface acoustic waves (SAWs) oscillated by ZnO thin-film piezoelectric transducers. It has a 98% optical transparency and a narrow frame of 1.4 mm. Therefore, it is ideally suitable for mobile devices, such as PDAs or cellular phones. Utilizing a single-phase transducer (SPT) constructed with a ZnO piezoelectric thin film sandwiched between a lower planar electrode and a comb-type electrode enabled us to reduce the ZnO film thickness to 1/20. The peculiarity of the ZnO transducer is using the local maximum of the electromechanical coupling factor with the SPT structure. It has been found that the hillocks on the lower electrode extremely affects the insertion loss and their suppression can improve the ZnO transducer quality. It is very helpful to introduce our own index, the area ratio of hillocks, to determine whether an aluminum alloy is suitable for the ZnO thin-film transducer or not. This paper describes the ZnO thin film we developed for the new SAW touch screen.

Reduction of baseline fluctuation in Electrocardiogram measurement for a car driver

Baseline fluctuation in Electrocardiogram (ECG) measurement system for car drivers is analyzed. The goal of this research is to develop a system that detects changes in R-R interval fluctuation, which is related to drowsiness and stress of the driver, and alert the driver to prevent drowsy driving. This system measures ECG with a contact electrode on the steering wheel and a capacitively coupled electrode on the drivers seat. This configuration allows ECG measurement while the driver is holding the steering wheel with one hand. The major source of baseline fluctuation is the static electricity generated by body motion, especially the pedaling motions that involve contact and removal of foot on the pedal. Baseline fluctuation can be as large as hundred times of the R-wave amplitude. Analysis of equivalent circuit model and experiments have shown that the baseline fluctuation can be reduced to 0.05 V by introducing an additional electrode on the drivers floor and connect it to the electrode in the steering wheel.

Assessment and prediction of older drivers' driving performance

Traffic accidents involving older drivers have been increasing all over the world. In order to assess elder driving performance and predict the risk of traffic accidents, we analyzed data from specific license renewal tests that are obligatory for Japanese drivers aged 70 years old or older, which includes a driving simulator test and an on-road test. As a result of the analysis, we found that aging affects several test results, such as the percentage of correct answers and the reaction times in multiple judgment tasks tests. In order to be able to classify a driver as a high accident risk, we performed an outlier analysis using a one-class SVM to investigate performance characteristics, and also performed a logistics regression analysis. Using parameters strongly related to cognitive decline, we found a viable way to classify impaired drivers. Driving is a complex task requiring integration of cognition, judgment, and operation skills. Deterioration of these skills is likely to increase the risk of traffic accidents. Although our final objective was to support elderly drivers suffering such deterioration, we initially studied a measurement method to detect the area and extent of deterioration effectively.

Measurement of a Car Driver’s Pulse Interval while Driving with One Hand

R-R interval measurement system for car drivers that allows measurement while the driver is driving with one hand has been developed. This system is intended for analysis of R-R interval fluctuation which is related to drowsiness and stress. R-R interval is the interval between R-waves in electrocardiogram (ECG). Our goal is to detect changes in R-R interval fluctuation and alert the driver to prevent drowsy driving. ECG was measured with a contact electrode on the steering wheel and a capacitive coupling electrode on the driver’s seat. ECG measurement with capacitive coupling is very sensitive to body motion. Baseline fluctuation can be as large as hundred times of the R-wave. In order to utilize differential amplification to reduce the fluctuation, an additional seat electrode was placed on top of the seat electrode with a paper insulator in between the two electrodes. The outputs of the upper seat electrode and the steering wheel electrode showed similar baseline fluctuation with respect to the lower seat electrode, while R-waves appeared only in the signal from the steering wheel electrode. Baseline fluctuation was reduced by taking the difference between the two signals. The proposed measurement method was evaluated in a real car. The system was capable of measuring R-waves of a passenger who held an electrode in the hand to simulate one hand driving while driving on a highway.

Development of adaptive noise reduction technology for in-vehicle heartbeat sensor

We proposed a noise reduction method for in-vehicle heartbeat sensor systems. The system measures the drivers heartbeat using a steering wheel electrode and a seat electrode that has dual construction. This configuration allows measurement while driving with one hand and provides two signals for noise cancellation. However, the amplitude ratio of the common mode noise varies when driving at high speeds. We multiplied a coefficient that was derived from the Root Mean Square (RMS) ratio between the two signals. This method enabled us to obtain 80% or more of the heartbeat signal while driving at high speed with one hand.