butterworth.m

截止频率在0.3Hz的巴特沃斯低通滤波器

clear all;
clc;
format long;
% a=load('E:\实验室工作\硕士论文\me\振动处理\me处理\低通滤波\39230000.dat');
a=load('E:\实验室工作\硕士论文\me\振动处理\me处理\低通滤波\01-27-1.dat');
b=a(12000:24000,10);
N=length(b);

for i=1:N
    x(i)=gain*b(i);
    for j=1:4
        k = 3*j-2;
        delay(k) = x(i)+delay(1+k)*den1(j)-delay(2+k)*den2(j);
        x(i) = delay(k)+delay(1+k)*num1(j)+delay(2+k)*num2(j);
        delay(2+k) = delay(1+k);
        delay(1+k) = delay(k);
    end
end
subplot(3,3,4);
plot(b);
subplot(3,3,5);
plot(x);
c(:,1)=b;
c(:,2)=x;
subplot(3,3,6);
% save c.dat c -ascii
plot(c);
%%%%%%%%%%%%%%%%滤波后谱分析%%%%%%%%%%%%%%%%%%%%%
w1=hanning(nfft);
w2=hamming(nfft);
w3=blackman(nfft);
[pxx1,f1]=psd(b,512,fs,w1,nfft/2);
[pxx2,f2]=psd(b,512,fs,w1,nfft/2);
[pxx3,f3]=psd(b,512,fs,w1,nfft/2);
subplot(3,3,7);
plot(f1(2:256),pxx1(3:257));
title('hanning');
subplot(3,3,8);
plot(f2(2:256),pxx2(3:257));
title('hamming');
subplot(3,3,9);
plot(f3(2:256),pxx3(3:257));
title('blackman');