Research On Non-contact Human Pbysiological Signal Detection System Based On PVDF Piezoelectric Film

With the rising in the proportion of sub-health populations in recent years,it is imminent to prevent sub-health early.As the most basic physiological parameters of human body,heart rate and respiratory rate reflect the daily health changes.Therefore,chronically and effectively detecting heart and respiratory rates are the first link for sub-health prevention.As a result of which,a non-contact system to detect human physiological signals is designed and developed in this paper.The main work is as follows:Firstly,a ballistocardiogram(BCG)signal acquisition system based on PVDF piezoelectric film is designed.The detection of BCG signal is realized by ordinary mattress which is internally embedded S-shaped piezoelectric film.TLC2254 chip which has four operational amplifiers is used to magnify and modulate piezoelectric signal,and STM32F4 built-in 12-bit ADC is applied to achieve signal conversion.Besides,we realize wireless interaction and storage of physiological signal parameters via Bluetooth module and WIFI module.Secondly,research on processing and analyzing BCG signal is carried out.The collected raw BCG signal is denoised by using FIR digital filters,and the heart rate is extracted by utilizing the differential threshold algorithm.After discussing the influence of different wavelet functions and decomposition scales on the signal reconstruction effect,the appropriate sym8 wavelet function algorithm is selected.Then,the effectiveness of the algorithm through is validated by processing and analyzing different human BCG signals.In addition,we design amplitude detection algorithm for effective identification aiming at the body movement and bed leaving events at night.Thirdly,the non-contact human physiological signal detection system’s practical test is completed.The heart rate of twelve testers for 15 minutes continuously is tested by using this system,and the pulse rate is collected at the same time.Compared with that of the medical equipment,the error of heart rate detection is within ±3 beats/min,which shows that the monitoring system has good reliability.What is more,we validate the consistency of the breath detection through comparing the extracted respiratory signal with the synchronously collected nasal thermal signal.Meanwhile,the good versatility of breath detection is proved by effectively capture respiratory waveforms which are different in frequency.Finally,magnetically induced sleep system is designed.For the negative impact of insomnia on sub-health rehabilitation,the magnetic induction module which is composed of magnetic coil and drive circuit is designed.And,we initially verify the function of outputting magnetic field adaptively by simulating the body moving process during sleep.In a word,in this paper,the non-contact human body physiological signal detection system based on PVDF piezoelectric film developed can realize the accurate detection of heart rate,respiratory rate and other physiological parameters,as well as the regulation of magnetic induction module,after experiments and tests.This system basically achieved the expected function.The study of this paper coincides with the current requirements of the public for medical testing methods,and it has positive significance in the prevention and regulation of sub-health.