Hellow,
I did sit to stand test with single IMU on the pelvis.
I have a acceleration data from IMU, and the units are m/s^2. The sample rate was 100Hz.
I did filter (butterwarth 4th order)
fc=3;
[b,a] = butter(4,fc/(100));
filtAcc = filter(b,a,y_acceleration);
and than numerical integration by cumtrapz function and remove the drift by detrend function twice: first time to get the velocity (units are [m/s] ?) and second time to get the displacement (units are [m] ?).
vertical_velocity=cumtrapz(filtAcc);
vertical_velocity_detrend=detrend(vertical_velocity);
vertical_displacement=cumtrapz(vertical_velocity_detrend);
vertical_displacement_detrend=detrend(vertical_displacement);
In the reality the displacement of the pelvis is 0.5 [m] or 50 [cm] why I got the displacement are in range -2000 to 2000 [m]?
Thank,
