【作者】 张颜颜；

【导师】 刘伯强；

【作者基本信息】 山东大学 ， 生物医学工程， 2008， 硕士

【摘要】 21世纪是世界科学界公认的生物科学、脑科学的时代。科技的进步使人类对外在世界的认知已经相当深刻,但人类对自身大脑的认知却十分肤浅。在全球性的研究计划的推动下,有关人脑认知过程的研究已成为当代科学发展的主流方向之一。认知功能是人体大脑高级机能的重要功能之一,是非常复杂的脑活动过程。目前脑电信号分析在认知科学的研究中起着不可或缺的重要作用,但用于脑认知研究的脑电分析系统十分昂贵,难以推广使用。因此,采用嵌入式结构方式,研究一种新型高性能低价格的脑电记录分析系统十分必要。本文完成了基于μC/os-Ⅱ的嵌入式脑电分析系统的设计。系统整体分为上位PC机和脑电信号采集仪器两部分。上位PC机和脑电信号采集仪器之间采用USB方式进行通信。嵌入式脑电采集仪器的设计是本文工作的重点,主要介绍了嵌入式脑电采集仪器的软硬件分析设计与实现,并采用实验室自主开发的上位机脑电采集分析软件实现了数据的采集分析。本文主要完成了以下工作:1)设计了高性能的脑电预处理电路。完成了放大、滤波、A/D转换等电路的设计。脑电预处理电路的性能主要取决于前置放大器,在本设计中选择了高精密度的仪表差分运算放大器AD620来构建放大器电路。2)完成了嵌入式子系统的硬件设计。采用强大的ARM微处理器S3C44BOX作为嵌入式系统的核心,完成了电源、JTAG接口、复位、晶振、存储器以及USB接口电路的设计,并完成了S3C44BOX启动程序的设计,3)在S3C44BOX微处理器上成功移植了实时嵌入式操作系统μC/os-Ⅱ。操作系统的引入是本系统软件设计的基础,使我们对软件各部分功能的管理更加方便,也使程序结构更加清晰、易读。更重要的是可以方便的进行系统升级和增加其他功能,有利于进一步开发。在成功移植了实时嵌入式操作系统μC/os-Ⅱ后,我们用S3C44BOX微处理器开发了基于μC/os-Ⅱ的USB驱动程序,完成了通讯软件的设计,并将应用软件所需要完成的功能划分为信号采集、数据预处理、参数设置、数据传输等几个部分,实现了模块化管理。4)采用实验室自主研究的脑电采集软件SDUND。完成了简单的诱发脑电信号采集实验。本系统设计的一个特点是为诱发脑电信号的提取提供了便利机制。系统由硬件接口来处理事件的起始同步问题。针对脑认知研究要处理不同事件下的诱发相关电位的特点,采用8通道0V/5V高低电平信号区分8类不同的刺激事件。在采集脑电信号的同时获取不同事件的起始同步信号,并将其与脑电信号封装在一起。这样,上位PC机在读取了数据后能够从一连串的数据中寻找到被刺激信号描记的脑电信号部分,对其进行叠加平均,提取出有效信息。基于μC/os-Ⅱ的嵌入式脑电分析系统能正确检测脑电信号的变化情况,实现了诱发脑电信号与刺激信号的同步描记,为诱发脑电信号的离线分析提供了事件标志,为脑认知的研究提供了实验工具,也可为脑-机接口的研究提供可靠的实验工具和分析平台。更多还原

【Abstract】 The 21st century is recognized by the world scientific community as the age of biological science and brain science.Advances in technology,humanity has a deep knowledge of the external world,but human awareness of its own brain is very superficial.In the promotion of global research projects,the research of human brain cognitive progress has become one of the mainstreams of contemporary scientific research.The brain cognitive function is a very complicated brain function process.EEG analyzing plays a very important part in the current research of the cognitive function.At present,the analyzing system used for brain cognitive research is too expensive to popularize. Therefore,a new high-performance and low-cost EEG analyzing system based on embedded system is very necessary.An EEG analyzing system based on Advanced RISC Machines(ARM)andμC/os-Ⅱreal time operating system is discussed in this paper.This system consists of two parts:EEG measurement and PC(personal computer).EEG measurement is connected with the PC by USB interface.The design of EEG measurement is the focus of this paper.The design of hardware and software of EEG measurement are completed.The data acquisition experiment is done using the EEG acquisition and analysis software SDUND which is developed by the laboratory independently.The experiment shows that the capabilities of this equipment are satisfied.The following works are completed in this paper.1)The design of high-performance EEG pretreatment circuit including amplification,filtering and A/D converter are described.The performance of EEG pretreatment circuit depends on preamplifier primarily.In this paper the high-precision instrumentation difference Operational Amplifier AD620 is selected to build amplifier circuit. 2)The hardware design of embedded subsystem is completed.An ARM microprocessor S3C44BOX is used as the core of the embedded system.The design of power supply,JTAG interface,reset,crystal,the memory and USB interface circuit are discussed.The BootLoader program of S3C44BOX is also discussed.3)TheμC/os-Ⅱreal-time embedded system is transplanted in S3C44BOX successfully.In this paper software design is based onⅡC/os-Ⅱ.Introduction of an operation system can manage programs more easily and make the structure of software clear.More importantly,its software can upgrade conveniently for further development.The design of communication software is completed.The driver of USB is developed in the base ofμC/os-Ⅱ.The system function is divided into five modules,signal acquisition,data preprocessing,parameter setting,order implementing,ordinary transmission and synchronous data transmission.4)A simple experiment of evoked EEG acquisition is done using the EEG acquisition and analysis software SDUND.This system uses hardware interfaces to deal with the synchronization of events.It uses 8 channels signal 0V/5V to distinguish eight different stimulations because brain cognitive research has to deal with ERP under different stimulations.Synchronization signals of different stimulations are acquired while recording EEG signals,then these signals are processed together.The system can accurately measure the EEG signals and synchronize the ERP signals and the stimulating signals.Therefore,this system can provide us with the event flag in the offline analysis of ERP.So it is a considerably useful experimental tool in brain cognitive research.It also supports us with a reliable experimental tool and analyzing platform for the Brain-Computer Inteface.更多还原