You are attempting to measure the oscillatory motion of a squirrel scratching it
ID: 3815641 • Letter: Y
Question
You are attempting to measure the oscillatory motion of a squirrel scratching it's ear with a leg-mounted accelerometer. In order to get the current position of the leg you will have to integrate twice. To help overcome the issues created when integrating you decide to implement a digital filter before integrating (filtering the acceleration data). After looking at YouTube you estimate the frequency of scratching to be around 5 Hz for a typical squirrel. Knowing the accelerometer will have quite a bit of noise, you decide to sample at 100 Hz. Given the scenario described, identify an appropriate digital filter type (low pass, band pass, etc.), filter name (elliptic, butter worth, etc.), cutoff frequency or frequencies, and filter order. Make sure to explain where your choices came from!
Explanation / Answer
Given the scenario, the following choices would be helpful.
1. Filter Type: Lowpass filter
Since we are interested in the frequency ranges around 5 Hz, Lowpass filter would be good.
Through this we can filter out the frequencies around 5Hz.
2. Filter Name: Butterworth Filter
Butterworth filter is designed to have as flat a frequency response as possible.
Since the problem talks about the noise, having a filter with maximally flat
magnitude would be good.
3. Cutoff frequencies:
This can be around 8Hz.
4. Filter Order:
Higher order filter, for example n = 6
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