Sense

This is a small application that was designed to graph sensor data and see the effect of some common filters on this data.

The following filters are used for the accelerometer:

Weighted Smoothing:

This is a common low-pass filter which involves weighting every new collected value against the old mean using a weighting value or smoothing parameter, set at 0.1 for the purposes of this application.

𝑤𝑠𝑚 = 𝑤𝑠𝑚𝑝𝑟𝑒𝑣 ∗ (1 − 𝑎) + (𝑥𝑖 ∗ 𝑎)

Simple Moving Average (SMA):

This low-pass filter calculates the arithmetic mean of the previous k values - the averaging window. K is set at 5 for the purposes of this application.

Simple Moving Median (SMM)

This low-pass filter calculates the median of the previous k values. Where k is even the 2 medians will be averaged. K is set at 5 for the purposes of this application.

Gyroscope:

Inversion of the above low-pass filters is applied to the gyroscope resulting in high-pass filters as gyroscopes are more susceptible to long-term drift.

The following filters are used on both accelerometer and gyroscope:

Complementary Filter (comp):

More on this filter can be found here: http://d1.amobbs.com/bbs_upload782111/files_44/ourdev_665531S2JZG6.pdf

𝑎𝑛𝑔𝑙𝑒 = 𝑎 ∗ (𝑎𝑛𝑔𝑙𝑒 + 𝑔𝑦𝑟𝑜 ∗ 𝑑𝑡) + (1 − 𝑎) ∗ 𝑎𝑐𝑐

b is set at 0.98, dt is set a 0.01.

Enhanced Complementary Filter (comp2):

This filter injects the current weighted smoothing value from the accelerometer and the inverse weighted smoothing value of the gyroscope into the balance filter.

Magnetometer values are not filtered.

Thank you for downloading and enjoy.