2012 年 50 巻 6 号 p. 564-570
In this study, we developed a point-contact force sensor, and this sensor was used to develop a measurement system that was shaped in the form of a feeding bottle. Unlike in a cantilever force sensor, in the proposed force sensor, the point of force measurement does not move. Thus, the force sensor can measure a force at a specified point. The force sensor consists of a pressure transducer and a steel ball with a diameter of 3 mm. Any force applied to the artificial nipple is transmitted to the pressure transducer, which is in point contact with the steel ball. The force sensor is linear up to a load of 3.92 N, has a hysteresis of 1%, and has a response time of 4 ms. The force is measured at distances of 8 mm (channel 1) and 14 mm (channel 2) from the tip of the nipple. In the measurement system, the sensor signals are converted (A/D) at a sampling rate of 100 Hz and a quantization resolution of 10 bits. After the A/D conversion, the force signals are transferred to a data indicator and a data logger for real-time display on an LCD and for storage ona micro SD card, respectively. Using this system, we performed measurements on four infants. A signal peak was observed from channel 2 and then from channel 1. This result could be attributable to the peristaltic movements of the infant's tongue. The same result was observed for all subjects. These results indicate that the proposed system can be used to measure any force that is applied to an artificial nipple. Moreover, the mother of a subject also performed measurements using the system. This confirmed that the system was easy to operate and that measurements could be performed in a normal feeding posture.