Butterworth filter how it works

Question

tupac1971ful 2016-5-21

0
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https://ww2.mathworks.cn/matlabcentral/answers/285224-butterworth-filter-how-it-works

回答： Star Strider 2016-5-21

So I wanted to remove the noise of my acceleration data signal so I could integrate to get velocity and integrate again to get displacement. I found about "filtering" on mathworks and I got the code to design but I cannot understand how it works, can someone help tellimg me what each step means and how can I modify it,if needed at all? Here's the code :

_%% Design High Pass Filter

fs = 8000; % Sampling Rate

fc = 0.1/30; % Cut off Frequency

order = 6; % 6th Order Filter

%% Filter Acceleration Signals

[b1 a1] = butter(order,fc,'high');

accf=filtfilt(b1,a1,acc); %acc : my acceleration data

I used hold on to plot both my acceleration with and without the filter to compare the results. The acceleration data had included the g acceleration and the filter removed it solely. finally something that I want to add is that I read someqhere about a function "detrend" clearing the signal. What's the difference between those two?