Human Sensing for Sleep Monitoring Using Film-Load Sensors

Abstract

This paper presents a novel bed-leaving sensor that is possible to be installed to various beds. Being made of piezoelectric films, this small and thin sensor requires no power supply for operation. Since the sensors are installed on a bed frame, they are invisible and thus is helpful for privacy protection. Moreover, we have developed a sensing system for monitoring and recognition of behavior patterns. Linear characteristics between loads and output were obtained from a load test for evaluation of the output characteristics of the sensors. Output values vary according to the input speed patterns in the case of the equivalent load. As a directional dependency, the maximum difference of the output voltage is three times. We have conducted an evaluation experiment for ten subjects using our original machine-learning based method. The experimental results on cross validation reveal that the mean recognition accuracy was 92.1% for four behavior patterns, which comprise longitudinal sitting, lateral sitting, terminal sitting, and leaving from the bed. The recognition accuracy of the leaving from the bed is merely 78.3%, although the accuracies of lateral sitting, terminal sitting, and longitudinal sitting were 100%, 98.3%, and 91.7%, respectively. For analysis using the confusion matrix, false recognition is distributed to the lateral sitting and terminal sitting.