Noninvasive Bed Sensing of Human Biosignals Via Piezoceramic Devices Sandwiched Between the Floor and Bed

Abstract

This paper describes a novel bed sensing method for noninvasive, constraint-free, subliminal detection of biosignals. The sensor system detects the heartbeat, respiration, body movement, position change, and scratching motion of a person lying or sleeping on the bed. These biosignals provide not only basic medical information but also sophisticated details about sleep conditions. Thus, the bed sensing method can be used to monitor the health condition of people sleeping at home, as well as that of patients in the hospital. Furthermore, the bed sensor system can detect emerging changes in the physical condition of a person, whether at home or in the hospital. The basic device used for sensing is piezoceramic bonded to stainless steel plate sandwiched between the floor and the four corners of the bed. Thus, no special bed is required. The device, which detects the biosignals generated as mechanical vibrations, has a wide dynamic range and high signal-to-noise (SN) ratio enabling the detection of microvibrations from the heartbeat by the change in acting force, without saturation from body movements. It accurately detects the person's heartbeat and respiration as well as body movement and even the number of scratching motions. The device is suitable for various health monitoring applications including sleep and medical monitoring for circulatory system disorders, as well as diseases characterized by itching.

A Petri net model of an integrated system for the Health Care At Home management

“…A bed sensor [9], [12], [13] is in the bedroom, giving the cardiac pulse and respiration rhythm of the patient and a bathtub sensor [8], [12] is in the bathroom, giving the cardiac pulse of the patient.…”

“…Some contributions investigate about new sensors to be installed in smart homes for monitoring the wellness and the health of the inhabitants [8], [9], [12], [13] or for the suitable use and analysis of the sensor outputs [15]. Other studies consider the problem of the online location tracking based on a state estimator [5], [6].…”

Sleep Quality Monitoring with the Smart Bed

“…The material is usually a thin and flexible film [23,25,31,37] which is placed under the bed mattress, a piezoelectric film sensor under the mattress topper [33], or a solid piezoceramic sensor [32,41] placed under the bedposts.…”

“…In [32] and [41] ceramic sensors were placed under the bed posts and were used to measure heartbeat, respiration, turning movements and scratching. They showed a good signal to noise ratio for the heartbeat (40 dB) and respiration (14 dB), but no clinical evaluation was done yet.…”

Multi-channel optical sensor-array for measuring ballistocardiograms and respiratory activity in bed

“…Accordingly, various types of sensors have been integrated into objects such as beds [1]- [9], (wheel-) chairs [10], [11], or weighing scales [12]. For the application in beds, a multitude of different sensors have been applied such as electromechanical film (EMFi) and polyvinylidene fluoride (PVDF) foils placed on top or beneath the mattress [1], [2], pneumatic mattresses [3], [4], hydraulic under-pillow sensors [5], infra-red sensor integrated into spring-coil mattresses [6], strain gauges under bed posts [7] or on the bed frame [8], as well as ultrasound sensors placed in a cavity beneath the mattress [9]. Most of these bed-based systems provide a single BCG signal which correlates with the integral of the forces acting on the entire mattress surface, or a large portion of it.…”