便携式人体生物电传感器的研究与设计

发布时间：2018-04-26 11:02

本文选题：有源电极 + 生物电　；参考：《南方医科大学》2012年硕士论文

【摘要】：人体的生物电信号(Bio-potential)与人体的许多功能密切相关,广泛应用于临床诊断、监护以及疾病预防等方面。但是由于人体生物电的幅值十分微弱,同时存在的各种干扰信号幅值往往很大,因此要准确的获得生物电信号必须通过专门的生物电传感器。生物电传感器一般是通过两个步骤将人体生物电信号转变为电路中电信号的：首先电极收集淹没于各种噪声与干扰中的人体表面的微弱电势变化,然后将检测到的电势变化传输到放大电路,经过放大器电路滤除各种噪声和干扰并且放大我们需要的微弱人体生物电信号,从而得到可供肉眼观察的电势变化波形。目前生物电在便携式设备与脑-机接口(Brain Computer Interface, BCI)领域的研究与应用在国内外掀起了一阵研究热潮。但是由于传统的人体生物电传感设备体积较大并且需要较为苛刻的使用环境,不能满足这些场合的应用。为了尽可能的减少环境限制,扩大人体生物电信号的使用范围,设计一种体积小、功耗低、放大倍数高的新型生物电传感放大设备显得十分必要。其中新型电极和新型的前置运放的设计又是其中研究的重点。传统的湿电极在使用时需要去除皮肤角质层并且添加额外的导电膏和固定胶带才能得到较好的信号,这样既不方便也不令人舒适从而限制了生物电的应用范围。对于新型电极的研究主要是为了克服传统湿电极的不足,即固定方便并且无需额外的预处理。其典型的代表有源电极(Active Electrodes)和干电极(DryElectrode)。国外如Biosemi公司、Nuroscan等公司都有自己专利的电极以及配套系统,而国内尚无较好的产品。传统的前置放大电路一般是针对临床条件下或者使用者静止的情况下设计的。而生物电的新型应用往往是处在人体运动状态下或者恶劣的电磁环境下,因此,新型放大电路应该具备抗干扰、噪声低、功耗低、电源稳等特点。针对这些要求,新型前置放大电路的研究主要寻求三方面的突破：其一,进一步提电路的抗干扰能力；其二,寻求一种可靠的低功耗的电池供电方案；其三,能够方便地与新型电极以及后续数字电路相结合。本文的主要工作是设计了一种新型的生物电传感采集显示方案,包括电极、前置放大电路以及后续数字采集显示系统的设计。对于电极的设计,针对实际情况与成本控制,本文选择了较易实现的有源电极方案,整个电极选用直径为1mm的纯银线与低成本的集成运放TLC272制作。对于前置放大电路的设计,本文选用仪表放大器AD623与TLC1078/1079两种低功耗芯片以保证整个电路的低功耗水平；采用Spinelli等人提出的AC耦合方法,使得作为第一级放大的仪表放大器AD623能够放大1000倍从而降低了整个系统的噪声水平；利用右腿驱动电路(Driven Right Leg circuit, DRL)(?)将人体电势驱动到供电电压的一半以满足单电源供电的需要。整个生物电传感装置较好地解决了电极阻抗不匹配产生的分压效应问题,充分抑制并减小了共模电压。整个模拟电路部分的设计采用仿真分析辅助实际电路实践验证的方法,即先在计算机中应用Pspice软件模拟分析,然后再实际搭建电路验证软件模拟结果,取得了较好的效果。Pspice仿真实验表明：该方案比其他几种类型的放大方案具有更宽的频带和更高放大增益,其50Hz共模抑制比可达到120dB以上,能够将μV级的信号放大至10000倍(受电源电压限制)。在实际电路的心电信号采集的测试中(放大1000倍),能够在没有任何皮肤处理的情况下,通过普通示波器观察到清晰明显的标准Ⅰ导联下的心电波形。对于脑电信号采集测试中(放大10000倍),采用DG1011型函数信号发生器内建的心电信号经阻性电路的衰减得到的信号进行模拟,也在示波器中得到了明显的信号,这表明该方案能够较好的抑制各种干扰噪声,能够在较恶劣的电磁环境中测量到人体微弱生物电信号。数字电路及显示部分选用芯片STM32作为下位机,主要用于AD转换以及与计算机的数字通讯,上位机程序选用LabVIEW软件编写,主要实现显示功能。
[Abstract]:Human bioelectrical signal (Bio-potential) is closely related to many functions of the human body. It is widely used in clinical diagnosis, monitoring and disease prevention. However, because the amplitude of human bioelectricity is very weak, the amplitude of various interference signals is often very large. Bioelectrical sensors. Bioelectrical sensors generally convert the human bioelectrical signals into electrical signals in the circuit through two steps: first, the electrode collects the weak potential changes of the human body surface submerged in various noises and interference, and then transfers the detected potential changes to the amplifier circuit and filters out various kinds of electric circuits through the amplifier circuit. Noise and interference, and magnify the weak human bioelectrical signals we need, so that we can get the potential change waveforms for the naked eye.
At present, the research and application of bioelectricity in the field of portable equipment and Brain Computer Interface (BCI) has set off a surge of research at home and abroad. However, because of the large size of the traditional human bioelectrical sensing equipment and the need for a more harsh environment, it can not meet the application of these applications. It is necessary to design a new type of biological electrical sensing magnifying equipment with small size, low power consumption and high magnification. The design of new electrode and new preamplifier is the focus of the research.
The traditional wet electrode needs to remove the skin cuticle and add extra conductive paste and adhesive tape to get better signal. It is neither convenient nor comfortable to limit the application range of bioelectricity. The research of new electrode is mainly to take the deficiency of traditional wet electrode, that is, it is convenient and convenient to fix. There is no need for extra pretreatment. It typically represents the active electrode (Active Electrodes) and dry electrode (DryElectrode). Foreign companies such as Biosemi, Nuroscan and other companies have their own patent electrodes and supporting systems, but there are no better products at home.
The traditional preamplifier circuit is usually designed under the condition of clinical or user static. The new application of bioelectricity is often under the condition of human motion or in the harsh electromagnetic environment. Therefore, the new type of amplifier should have the characteristics of anti-interference, low noise, low power consumption and stable power. The research of the new preamplifier mainly seeks three breakthroughs: one is to further improve the anti-interference ability of the circuit; secondly, to seek a reliable and low power battery power supply scheme; thirdly, it can be easily combined with new electrodes and subsequent digital circuits.
The main work of this paper is to design a new type of bioelectrical sensing collection and display scheme, including the design of electrode, preamplifier circuit and subsequent digital acquisition and display system. For the design of the electrode, in view of the actual situation and cost control, this paper selects the active electrode scheme which is easier to realize. The diameter of the whole electrode is 1mm. The pure silver line and low cost integrated operational amplifier TLC272 are made. For the design of the preamplifier circuit, the instrument amplifier AD623 and TLC1078/1079 two low power chips are selected to ensure the low power consumption level of the whole circuit. The AC coupling method proposed by Spinelli et al. Makes the AD623 of the instrument amplifier as the first stage magnification can be magnified The noise level of the whole system is reduced by 1000 times, and the right leg drive circuit (Driven Right Leg circuit, DRL) is used to drive the potential of the human body to half of the power supply to meet the needs of the single power supply. The whole bioelectrical sensing device solves the problem of the partial pressure effect caused by the mismatch of the electrode resistance, and fully restrains it. The common mode voltage is reduced. The design of the whole analog circuit uses the method of simulation analysis to assist the practice verification of the actual circuit, that is to use the simulation analysis of Pspice software in the computer first, and then build the circuit to verify the results of the software simulation, and obtain good results.Pspice simulation experiments show that the scheme is more than the other types. The amplification scheme has a wider frequency band and higher amplification gain, and its 50Hz common mode suppression ratio can reach more than 120dB and can magnify the signal of the V level to 10000 times (subject to the power supply voltage limit). In the test of the ECG signal acquisition in the actual circuit (magnified 1000 times), it can pass the ordinary oscilloscope without any skin treatment. The ECG waveform under the clear and obvious standard I lead is observed. For the EEG signal acquisition test (10000 times magnified), the signal obtained by the attenuation of the impedance circuit built by the DG1011 type function signal generator is simulated, and the obvious signal is obtained in the oscilloscope, which shows that the scheme can be better suppressed. Various interference noises can be used to measure the weak bioelectrical signal of human body in a bad electromagnetic environment. The digital circuit and display part are used as a lower computer, which is mainly used in AD conversion and digital communication with the computer. The host computer program is written by LabVIEW software, which mainly realizes the display function.

【学位授予单位】：南方医科大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：R318.6

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