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II
Research on Mental Workload Classification Algorithm
Based on ECG Co-dimension Features
Abstract
Nowadays, the working scenes of human-computer interaction are more and
more abundant. Identifying the workload level of the operator's brain and giving
timely warning can effectively reduce the incidence of accidents, ensure life safety
and improve work efficiency to a certain extent. Electrocardiogram (ECG) can not be
artificially controlled and forged, and the acquisition of ECG is safe, cheap,
noninvasive, easy to use, and will not affect the daily operation of personnel engaged
in dangerous types of work. The technology of automatic ECG signal analysis is
currently an important topic in the classification of mental workload. However, due to
individual ECG signal differences and noise impact, it is still faced with many
difficulties to identify it accurately and efficiently. Based on this, the main research
and analysis work of this thesis are as follows: First, with regard to ECG signal
preprocessing, aiming at the sudden abnormalities in ECG signal, this paper proposes
a frequency correlation method according to the similar frequency domain
composition of each heartbeat of ECG signal. This method accurately and
automatically eliminates the interference signal segments without manual intervention
by setting the threshold value, which lays the foundation for subsequent feature
extraction and mental workload classification, It also provides a new idea for other
similar ECG signal processing. Wavelet transform soft threshold denoising is applied
to ensure the overall quality of ECG signal. Combined with notch filter and
differential threshold method, accurate R-wave position is obtained, which lays a
foundation for subsequent feature extraction. Secondly, in terms of ECG feature
extraction, this paper extracts the features of ECG signals under low, medium and
high mental workload levels, and extracts 14 features in total. It includes the more
mature time domain, frequency domain and nonlinear features of Heart Rate
Variability (HRV) in the field of mental workload research, as well as the innovative
frequency domain feature TP wave power, QRS complex power and nonlinear feature
III
sample entropy of ECG waveform extracted from the research of cardiac pathology
and EEG. In view of the different feature extraction cycles of HRV features and ECG
waveform features, A co-dimension ECG feature extraction method of sliding window
and resampling is proposed, which maximizes the use of the features in mental
workload classification. Finally, this paper establishes the three classification mental
workload model of ECG co-dimension features based on the random forest algorithm
by comparing the classification accuracy and test time of the classification model of
k-Nearest Neighbor, Support Vector Machines(SVM), Decision Tree, Random Forest
and AdaBoost algorithm, as well as the classification accuracy obtained by combining
the 14 dimensional ECG features into 8 different inputs according to the types, The
average classification accuracy is 96.406%.
Key words: Mental Workload,ECG,Co-dimension Features,Random Forest
目 录
摘 要 ................................................... I
ABSTRACT ................................................II
第一章 绪论 ............................................. 1
1.1
研究的背景与意义
............................................................................................. 1
1.2
国内外研究现状
................................................................................................. 2
1.2.1
心电信号预处理的研究现状
...................................................................... 2
1.2.2
心电特征提取与分析的研究现状
.............................................................. 3
1.2.3
脑力负荷分类的研究现状
.......................................................................... 5
1.3
本文的研究思路
................................................................................................. 6
1.4
本文研究内容和结构
......................................................................................... 7
第二章 脑力负荷实验设计及心电信号的获取 ................. 9
2.1
脑力负荷实验整体设计和信号采集
................................................................. 9
2.2 MATB
任务和主观量表数据的获取
................................................................10
2.3
本章小结
........................................................................................................... 13
第三章 心电信号的预处理 ................................. 14
3.1
心电信号的去噪
............................................................................................... 14
3.1.1
突发噪声剔除方法
.................................................................................... 15
3.1.2
心电信号整体去噪
.................................................................................... 21
3.2
心电
R
波位置获取方法
...................................................................................22
3.3
本章小结
........................................................................................................... 24
第四章 心电信号的多维度特征提取和联合方法 .............. 25
4.1
心电信号波形的特征提取与分析
................................................................... 26
4.1.1
波形频域特征提取与分析
........................................................................ 26
4.1.2
波形非线性特征提取与分析
.................................................................... 27
4.2
心电
HRV
特征提取与分析
............................................................................. 27
4.2.1 HRV
及其时频域特征提取
........................................................................ 27
4.2.2
庞加莱图非线性分析和特征提取
............................................................ 29
4.3
心电波形特征和
HRV
特征联合方法
............................................................. 30
4.4
本章小结
........................................................................................................... 32
第五章 心电联合特征的脑力负荷分类 ...................... 33
5.1
心电特征应用于脑力负荷分类的分析
........................................................... 33
5.1.1
不同脑力负荷水平下心电特征的显著性分析
........................................ 37
5.1.2
心电联合特征的可视化
............................................................................ 37
5.2
脑力负荷分类模型的建立和算法原理
........................................................... 33
5.2.1 k
近邻
.......................................................................................................... 37
5.2.2 SVM.............................................................................................................38
5.2.3
决策树
........................................................................................................ 39
5.2.4
随机森林
.................................................................................................... 39
5.2.5 Adaboost...................................................................................................... 40
5.3
脑力负荷分类模型结果的对比和分析
........................................................... 41
5.3.1
不同算法的脑力负荷分类效果分析
........................................................ 41
5.3.2
分类模型输入特征的不同组合
................................................................ 42
5.3.3
不同特征作为模型输入的结果分析
........................................................ 44
5.4
本章小结
........................................................................................................... 46
第六章 结论与展望 ...................................... 47
6.1
主要结论
........................................................................................................... 47
6.2
研究展望
........................................................................................................... 48
参考文献 ................................................ 49
在学期间的研究成果 ...................................... 55
致 谢 .................................................. 56
第一章 绪论
1
第一章 绪论
1.1
研究的背景与意义
近年来,由于工业信息化的蓬勃发展,各种作业任务的智能化和信息化程度
也日益提高,作业人员所承担的脑力负担也日益增大。研究表明,
60%
至
90%
的
驾驶事故是在高脑力负荷的状态下发生的。在当前的人机交互设计中,脑力负荷
是一个非常重要的问题,有关的信息探测技术已成为人们普遍关心的问题。如何
有效评估人类的脑力负荷已成为各类工效学专家们所面临的一个重要课题。大脑
负荷在本质上是中枢诱导的,随着人体各器官在不同负荷状态下的应激反应,心
血管神经系统和体液也会随之调整
[1-4]
。
脑力负荷被称为实现任务目标所需的认知资源水平。它受到任务难度、过去
经验和外部支持的影响。适当的脑力负荷可以帮助驾驶员安全有效地执行任务
(或附加任务)。研究表明,较低的脑力负荷会导致操作员延长决策时间,对其
他操作员的行为反应较慢,或做出错误的驾驶行为,而更高水平的脑力负荷可能
会导致错误的决策甚至事故。目前,通过分析操作者生理特征的变化,如脑电信
号、心电信号、反应能力、眼部眨眼和眼睑闭合度等
[5-10]
,监测危险工种的脑力
负荷水平是一个重要的手段。
心电信号不能被人为控制和伪造。而且采集心电信号是一种实用的方法,因
为它安全、廉价、无创,而且易于使用,并且不会影响从事危险工种人员的日常
操作。许多研究表明心电信号与脑力负荷有关
[11-13]
,特别是在安全关键动态系统
如运输系统的驾驶领域
[14-17]
。心电信号被认为受到交感神经系统和自主神经系统
副交感神经的影响,它可以帮助定义脑力工作负荷指数。在脑力负荷作用下,机
体各脏器的应激响应,使心血管神经和体液发生相应的调整。因此,心电信号是
识别脑力负荷水平的重要工具,它可以用于开发个性化的驾驶警告系统和车辆中
的智能车内人机交互,从而获得更可靠的措施助于提高车辆的安全性能。
在生物医学和计算机科学中,心电信号的自动分析是目前国内外研究的热点。
因此,重要的是要找到有效可靠的方法来测量脑力负荷,并分析其机制,以促进
最佳的人因绩效和最大限度地减少人为错误。当任务难度增加时,人类可能不得
不做出更大的努力来保持安全、稳定和质量合格的工作性能。因此,重要的是要
知道,当人们试图保持稳定的表现水平时,某些措施是否能有效地提供对高脑力
负荷条件的灵敏检测。
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