Filter löschen
Filter löschen

Filtering high frequencies from response signal

17 Ansichten (letzte 30 Tage)
Joe Bennet
Joe Bennet am 20 Jan. 2021
Kommentiert: Star Strider am 21 Jan. 2021
I have a data set comprising a number of strain measurements obtained from a strain gauge and would like to filter out the ultra high frequncy noise present inbetween the seperate measurements. See code attached below :)
clc, clear, close all;
t= g{:,1};
sm= g{:,3};
sm= rmmissing(sm);
t = arrayfun(@(i) mean(t(i:i+n-1)),1:n:length(t)-n+1)';
sm= arrayfun(@(i) mean(sm(i:i+n-1)),1:n:length(sm)-n+1)';
xlabel('Time Elapsed (s)')
title('Strain Signal')
fs= 6.2e-4;

Akzeptierte Antwort

Star Strider
Star Strider am 20 Jan. 2021
Try this:
D1 = load('7004x4.mat');
T1 = D1.g;
Q1 = T1(1:5,:);
t = T1{:,1};
sm = T1{:,3};
t = rmmissing(t);
sm = rmmissing(sm);
% Signal Vector
L = size(sm,1); % Data Length
Fs = 1/mean(diff(t)); % Sampling Frequency
Ts = 1/Fs; % Sampling Interval
Fn = Fs/2; % Nyquist Frequency
smc = sm - mean(sm); % Subtract Mean (Makes Other Peaks More Prominent)
FTsm = fft(smc)/L; % Normalised Fourier Transform
Fv = linspace(0, 1, fix(L/2)+1)*Fn; % Frequency Vector
Iv = 1:numel(Fv); % Index Vector (One-Sided Fourier Transform)
plot(Fv, abs(FTsm(Iv))*2)
xlim([0 50])
title('Fourier Transform')
xlabel('Frequency (Hz)')
Wp = [30]/Fn; % Passband Frequency (Normalised)
Ws = [1.01].*Wp; % Stopband Frequency (Normalised)
Rp = 1; % Passband Ripple
Rs = 60; % Passband Ripple (Attenuation)
[n,Wp] = ellipord(Wp,Ws,Rp,Rs); % Elliptic Order Calculation
[z,p,k] = ellip(n,Rp,Rs,Wp); % Elliptic Filter Design: Zero-Pole-Gain
[sos,g] = zp2sos(z,p,k); % Second-Order Section For Stability
freqz(sos, 2^20, Fs) % Filter Bode Plot
set(subplot(2,1,1), 'XLim',Wp*Fn.*[0.8 1.2]) % Optional
set(subplot(2,1,2), 'XLim',Wp*Fn.*[0.8 1.2]) % Optional
sm_filtered = filtfilt(sos, g, sm); % Filter With IIR Filter
plot(t, sm)
hold on
plot(t, sm_filtered)
hold off
xlabel('Time (Units Estimated)')
ylabel('AMplitude (Units Not Specified)')
legend('Original Signal', 'Lowpass-Filtered Signal', 'Location','SE')
Adjust the value of ‘Wp’ (Passband Frequency) of the filter to get the result you want. The Fourier transform plot can help with that decision.
  5 Kommentare
Joe Bennet
Joe Bennet am 21 Jan. 2021
Thank you so much!
Star Strider
Star Strider am 21 Jan. 2021
My pleasure!
If my Answer helped you solve your problem, please Accept it!

Melden Sie sich an, um zu kommentieren.

Weitere Antworten (1)

Mathieu NOE
Mathieu NOE am 20 Jan. 2021
try also sgolayfilt
function y=sgolayfilt(x,order,framelen,weights,dim)
%SGOLAYFILT Savitzky-Golay Filtering.
% SGOLAYFILT(X,ORDER,FRAMELEN) smooths the signal X using a
% Savitzky-Golay (polynomial) smoothing filter. The polynomial order,
% ORDER, must be less than the frame length, FRAMELEN, and FRAMELEN must
% be odd. The length of the input X must be >= FRAMELEN. If X is a
% matrix, the filtering is done on the columns of X.



Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by