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Further filtering of accelerometer data

PIYUSH MOHANTY さんによって質問されました 2019 年 10 月 6 日
最新アクティビティ Nikhil Sonavane さんによって コメントされました 2019 年 10 月 11 日
Hi Star Strider, I find your answers regarding the filters to be quite insightful.
I have a similar problem. I have used the Butterworth filter of 5th order and used 0.7Hz and 50 Hz as cutoff frq for passband filter. I am quite sure the frequncy beyond this frequncy region is not of point of interest. My sampling frequncy : 200Hz.
Still I can see there is noise as it can be seen in the attched figure.
Can you please help me to further denoise the data/filter data? I have attached the .fig file aswell for your reference.
Thanks in advance.acc8 filtered.jpg

  2 件のコメント

Nikhil Sonavane 2019 年 10 月 9 日
It would be great if you can share me your data and filter parameters.
PIYUSH MOHANTY 2019 年 10 月 9 日
Hi Nikhil,
Please find my data as attached.
Here is my filter parameters:
d=dlmread('acc8.txt');
t=dlmread('Time.txt'); %File having sampling time instances
order = 5;
fcutlow = 0.3;
fcuthigh = 50;
fs=200;
[b,a]=butter(order,[fcutlow fcuthigh]/(fs/2),'bandpass');
X_filt=filtfilt(b,a,d);
figure()
plot(t,d);
hold on
plot(t,X_filt);%2
hold off

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1 件の回答

回答者: Nikhil Sonavane 2019 年 10 月 9 日

After looking at the Fourier Transform (figure attached) of your input data it can be concluded that it majorly comprises of frequencies from 0Hz to 50Hz. If you use a bandpass filter with cut off frequencies of 0.3Hz and 50Hz, you are allowing most of the frequencies through the filter and hence you are not able to remove the noise. Try changing the cut off frequencies to eliminate the spikes in your output data. fft.jpg

  5 件のコメント

PIYUSH MOHANTY 2019 年 10 月 10 日
Hi Nikhil,
Can you please let me know if my point of interest (from the perspective of analysis) frequency range is 1-10 Hz, is it ok if I put the cutoff 0.3Hz -20 Hz. Does it any way affect my data in 1-10Hz range?
Thanks in advance.
piyush
PIYUSH MOHANTY 2019 年 10 月 11 日
Further, reducing the frequncy cutoff points is not helping much. What else kind of noise can be there in the signal?
Nikhil Sonavane 2019 年 10 月 11 日
Consider reducing the frequency range of the filter to less than 10Hz. Also try using a higher order filter to get a sharp transition.

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