Mechanical Engineering

# how to draw a 3D-HHT using MATLAB,here is a good example for us.

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clc
clear
close all
fs = 1024;
n = 1024;
t = 0:1/fs:(n-1)/fs;
y = sin(2*pi*50*t) + 0.4*cos(2*pi*150*t);
figure,plot(y)
set(gca,'xlim',[0,1024])
imf = emd(y);
plot_hht_3d(imf,1024,1024,[-60,50])

imf：emd分解后的结果
numfreq：划分的频率个数
fs：采样频率
ANGLE：视图角度

function plot_hht_3d(imf,numfreq,fs,ANGLE)
if nargin<3
fs=1;
ANGLE=[-37.5,30];
end
if nargin<4
if size(fs,2)>1
ANGLE=fs;
fs=1;
else
ANGLE=[-37.5,30];
end
end
N=size(imf,2);
[A,f,tt]=hhspectrum(imf);
[m,n]=size(f);
MaxFreq=max(max(f));
MaxFreq=ceil(MaxFreq/0.5)*0.5;
if nargin<2
numfreq=512;
end
df=linspace(0,MaxFreq,numfreq);
Spectrum=zeros(numfreq,n);
Temp=f;
Temp=min(round((Temp/MaxFreq)*numfreq)+1,numfreq);
for k=1:m
for u=1:n
Spectrum(Temp(k,u),u)=Spectrum(Temp(k,u),u)+A(k,u);
end
end
df=df*fs;
figure
clf
mesh(tt,df,Spectrum);
set(gca,'XLim',[0,N]);
xlabel('采样点数/n');
if fs==1
ylabel('归一化频率');
else
ylabel('频率/Hz');
end
zlabel('幅值');
title('三维联合时频图');
colormap jet;
view(ANGLE(1),ANGLE(2));
set(gca,'YLim',[0,fs/2]);
end

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This has limited value to those who do not read Oriental characters.

What is HHT?

DrD

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sorry, i will revise it if you need.

HHT is means Hilbert-Huang Transform, which was proposed by Huang in 1998, NASA, US.

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Dear Ching,

I have no need for this personally, but if it is worth posting, it must be worth posting where a reader can understand it. In this case, since this is an English language site, that means putting it all in English.

What is the value of the Hilbert-Huang transform? What sort of problems and solution processes call for it? There is a lot more you could say that would make your note more interesting and of greater value.

DrD

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