基于振动加速度的无束缚心冲击检测与心率提取方法研究

Unconstrained detection of ballistocardiogram and heart rate based on vibration acceleration

针对睡眠过程中无束缚监测心动信息的需求和现有检测方法在精度和方便性方面存在的缺点,本研究设计制作了一套利用加速度传感器无束缚检测心冲击的系统,开发了相应算法。心冲击信号具有方向性,沿脊柱方向强度最大,受呼吸运动影响最小。本研究采用固定于床体的3轴加速度传感器检测心冲击激发的床体振动,从中分离提取脊柱方向信号,以实现睡眠过程中的无束缚心冲击检测。信号预处理中,首先利用频率特征分析找出心冲击信号的频率范围,然后在此范围内对原始信号进行分段滤波并将结果与理论波形比较,以确定信号的通频阈值,从而获得准确的心冲击波形。本研究基于能量波形进行J波检测,并提出了一种幅值与周期相结合的自适应阈值算法,以准确提取心率。通过与心电图的对比实验,验证了噪声背景下提取心冲击信号的准确性和鲁棒性。对30名受试者进行的实验结果显示,所开发的系统检测心率的准确度高达99.21%,验证了利用加速度传感器无束缚检测心冲击的可行性。

The requirement for unconstrained monitoring of heartbeat during sleep is increasing,but the current detection devices can not meet the requirements of convenience and accuracy.This study designed an unconstrained ballistocardiogram(BCG)detection system using acceleration sensor and developed a heart rate extraction algorithm.BCG is a directional signal which is stronger and less affected by respiratory movements along spine direction than in other directions.In order to measure the BCG signal along spine direction during sleep,a 3-axis acceleration sensor was fixed on the bed to collect the vibration signals caused by heartbeat.An approximate frequency range was firstly assumed by frequency analysis to the BCG signals and segmental filtering was conducted to the original vibration signals within the frequency range.Secondly,to identify the true BCG waveform,the accurate frequency band was obtained by comparison with the theoretical waveform.The J waves were detected by BCG energy waveform and an adaptive threshold method was proposed to extract heart rates by using the information of both amplitude and period.The accuracy and robustness of the BCG detection system proposed and the algorithm developed in this study were confirmed by comparison with electrocardiogram(ECG).The test results of 30 subjects showed a high average accuracy of 99.21%to demonstrate the feasibility of the unconstrained BCG detection method based on vibration acceleration.