【肌电信号】基于GUI MUAP波形【Matlab 736期】

2023-10-17 21:29:40

一、简介

EMG 信号是很容易采集的，但是要想理解和解释所采集到的EMG信号是非常困难的。对EMG信号进行分析可以让我们具备理解肌肉中力的产生机制以及肌肉如何产生运动的能力。但如何提取这些信息取决于适当的信号获取办法。
1 EMG信号提取过程
信号采集，信号调节和信号处理。流程图如下所示
【肌电信号】基于GUI MUAP波形【Matlab 736期】
2 信号采集
肌肉收缩可以引起皮肤表面电流发生变化，此电流的大小可以通过放置在皮肤表面的电极来测量得到。电极与皮肤接触的区域被称为测量表面(detection surface)。利用表面电极测量得到的生理学数据被称为表面肌电流(sEMG)。sEMG是电极测量的来自于所有活跃运动单元的MUAPTs的总和。
【肌电信号】基于GUI MUAP波形【Matlab 736期】
随着肌肉输出力的增加，活跃运动单元的数量也随着增加。由于肌肉收缩时许多运动单元都是活跃的，因此，电极测量到的信号来自于许多不同的运动单元。MUAP的形状和幅值取决于肌纤维和电极的相对方向(和其他因素相比)。在一个MUAPT中，如果电极和肌纤维的相对位置保持不变，电极的属性保持不变以及肌肉组织的生物化学属性没有改变，则MUAP的的波形保持不变。
有作者在144篇文章里发现了352种采集表面肌电流信号时电极安放位置的描述。其中大部分的方法都是通用的，并且提到肌腹(肌肉中部较厚的区域)，Motor point(轴突和肌纤维接触的地方)，或者肌肉中点。

影响EMG稳定性的因素包括：

  1. 运动单元/肌腱
  2. 附近其他活跃肌肉
  3. 活跃肌肉纤维和测量点的距离
  4. 电极的滤波特性
  5. 神经区域(innervation zone)和电极的位置之间的关系

通常，双极点电极相对于肌纤维平行放置，并且两电极中心距离在20 mm以上的时候可以取得较好的结果。这种距离足够小可以避免信号的串扰，并且足够大选择众多的运动单元。

参考电极应该放置在中性组织上(i.e. 骨头突出的部分)，以便于给电极放大器提供一个公用的参考。

3 信号调节
电极-放大器用来减小电极-皮肤的阻抗。
信号调节用来进一步改善EMG信号的质量。
信号调节的方法包括：

滤波以减小运动伪迹
电极运动伪迹可能来自于表面电极区域下的皮肤变形，或者电极电荷层的扰动。运动伪迹的功率密度小于20 Hz。因此，高通滤波器可用于改善信号的质量。这种滤波器的转折频率应该在10 Hz和20 Hz之间，但是不能大于20 Hz，否则会导致EMG信号能量的丢失。
用于运动伪逆的滤波技术包括：

  1. 8th order Chebychev high pass filters
  2. adaptive filtering based on orthogonal Meyer wavelets
    EMG信号放大

要特别注意工频噪声的干扰。
power line interference

4 信号处理
EMG 信号用作控制信号：

  • 多功能假肢
  • 轮椅
  • 抓握控制
  • 虚拟键盘
  • 基于姿势的控制接口

5 数据分割
EMG信号有两种状态：

  • 瞬态： 肌肉从静止到自主收缩
  • 稳态： 肌肉产生常力收缩
    瞬态EMG信号比稳态EMG信号处理起来要更困难一些。

6 特征提取
时域特征
EMG幅值和活跃运动单元的数量以及他们的活跃水平有关系。
形成EMG幅值的方法有：

  • 模拟修正和平滑(低通)
  • 平均绝对值(MAV)处理
  • 均方根(RMS)处理

对于高层次的收缩，可以采用高斯模型对EMG信号进行拟合；对较弱的肌肉收缩和处于肌肉疲劳状态的收缩可以采用LaPlacian进行拟合。
其他EMG时域特征包括：平均绝对值（MAVs）斜率，zero crossing,斜率符号改变和波形长度。

7 频域特征
时域-频域特征
专业用语
surface EMG( sEMG): 表面肌电信号
MU (motor unit): 运动单元
MUAPTs (motor unit action potential trains): 动作电位序列
motion artifact: 运动伪迹

二、部分源代码

function varargout = MUAPgui(varargin)
% MUAPGUI M-file for MUAPgui.fig
%      MUAPGUI, by itself, creates a new MUAPGUI or raises the existing
%      singleton*.
%
%      H = MUAPGUI returns the handle to a new MUAPGUI or the handle to
%      the existing singleton*.
%
%      MUAPGUI('CALLBACK',hObject,eventData,handles,...) calls the local
%      function named CALLBACK in MUAPGUI.M with the given input arguments.
%
%      MUAPGUI('Property','Value',...) creates a new MUAPGUI or raises the
%      existing singleton*.  Starting from the left, property value pairs are
%      applied to the GUI before MUAPgui_OpeningFunction gets called.  An
%      unrecognized property name or invalid value makes property application
%      stop.  All inputs are passed to MUAPgui_OpeningFcn via varargin.
%
%      *See GUI Options on GUIDE's Tools menu.  Choose "GUI allows only one
%      instance to run (singleton)".
%
% See also: GUIDE, GUIDATA, GUIHANDLES

% Copyright 2002-2003 The MathWorks, Inc.

% Edit the above text to modify the response to help MUAPgui

% Last Modified by GUIDE v2.5 27-Dec-2006 12:09:22

% Begin initialization code - DO NOT EDIT
gui_Singleton = 1;
gui_State = struct('gui_Name',       mfilename, ...
                   'gui_Singleton',  gui_Singleton, ...
                   'gui_OpeningFcn', @MUAPgui_OpeningFcn, ...
                   'gui_OutputFcn',  @MUAPgui_OutputFcn, ...
                   'gui_LayoutFcn',  [] , ...
                   'gui_Callback',   []);
if nargin && ischar(varargin{1})
    gui_State.gui_Callback = str2func(varargin{1});
end

if nargout
    [varargout{1:nargout}] = gui_mainfcn(gui_State, varargin{:});
else
    gui_mainfcn(gui_State, varargin{:});
end
% End initialization code - DO NOT EDIT


    % --- Executes just before MUAPgui is made visible.
function MUAPgui_OpeningFcn(hObject, eventdata, handles, varargin)
% This function has no output args, see OutputFcn.
% hObject    handle to figure
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
% varargin   command line arguments to MUAPgui (see VARARGIN)

% Choose default command line output for MUAPgui
handles.output = hObject;

% Update handles structure
guidata(hObject, handles);
clear all;
% UIWAIT makes MUAPgui wait for user response (see UIRESUME)
% uiwait(handles.figure1);


% --- Outputs from this function are returned to the command line.
function varargout = MUAPgui_OutputFcn(hObject, eventdata, handles) 
% varargout  cell array for returning output args (see VARARGOUT);
% hObject    handle to figure
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Get default command line output from handles structure
varargout{1} = handles.output;


% --- Executes on button press in Laplace.
function Laplace_Callback(hObject, eventdata, handles)
% hObject    handle to Laplace (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

global muap;
lapmuap=4*muap(2,:)-muap(1,:)-muap(3,:)-muap(4,:)-muap(5,:);
axes(handles.axes1);
HH=plot(lapmuap);
set(HH,'LineWidth',2);
clear HH;

% --- Executes on button press in Bipolar.
function Bipolar_Callback(hObject, eventdata, handles)
% hObject    handle to Bipolar (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
global muap;

biomuap=muap(1,:)-muap(2,:);
axes(handles.axes2);
HH=plot(biomuap);
set(HH,'LineWidth',2);
clear HH;

% --- Executes on button press in Monopolar.
function Monopolar_Callback(hObject, eventdata, handles)
% hObject    handle to Monopolar (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

global muap;

axes(handles.axes3);
HH=plot(muap(2,:));
set(HH,'LineWidth',2);
clear HH;

function nf_Callback(hObject, eventdata, handles)
% hObject    handle to nf (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Hints: get(hObject,'String') returns contents of nf as text
%        str2double(get(hObject,'String')) returns contents of nf as a double


% --- Executes during object creation, after setting all properties.
function nf_CreateFcn(hObject, eventdata, handles)
% hObject    handle to nf (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    empty - handles not created until after all CreateFcns called

% Hint: edit controls usually have a white background on Windows.
%       See ISPC and COMPUTER.
if ispc
    set(hObject,'BackgroundColor','white');
else
    set(hObject,'BackgroundColor',get(0,'defaultUicontrolBackgroundColor'));
end



function skinfat_Callback(hObject, eventdata, handles)
% hObject    handle to skinfat (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Hints: get(hObject,'String') returns contents of skinfat as text
%        str2double(get(hObject,'String')) returns contents of skinfat as a double


% --- Executes during object creation, after setting all properties.
function skinfat_CreateFcn(hObject, eventdata, handles)
% hObject    handle to skinfat (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    empty - handles not created until after all CreateFcns called

% Hint: edit controls usually have a white background on Windows.
%       See ISPC and COMPUTER.
if ispc
    set(hObject,'BackgroundColor','white');
else
    set(hObject,'BackgroundColor',get(0,'defaultUicontrolBackgroundColor'));
end



function x_Callback(hObject, eventdata, handles)
% hObject    handle to x (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Hints: get(hObject,'String') returns contents of x as text
%        str2double(get(hObject,'String')) returns contents of x as a double


% --- Executes during object creation, after setting all properties.
function x_CreateFcn(hObject, eventdata, handles)
% hObject    handle to x (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    empty - handles not created until after all CreateFcns called

% Hint: edit controls usually ave a white background on Windows.
%       See ISPC and COMPUTER.
if ispc
    set(hObject,'BackgroundColor','white');
else
    set(hObject,'BackgroundColor',get(0,'defaultUicontrolBackgroundColor'));
end

三、运行结果

【肌电信号】基于GUI MUAP波形【Matlab 736期】
【肌电信号】基于GUI MUAP波形【Matlab 736期】

四、matlab版本及参考文献

1 matlab版本
2014a

2 参考文献
[1] 沈再阳.精通MATLAB信号处理[M].清华大学出版社，2015.
[2]高宝建,彭进业,王琳,潘建寿.信号与系统——使用MATLAB分析与实现[M].清华大学出版社，2020.
[3]王文光,魏少明,任欣.信号处理与系统分析的MATLAB实现[M].电子工业出版社，2018.
[4]徐洁.基于小波分析的脉搏波信号处理[J].电子设计工程. 2013,21(11)

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