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Tracking 3d gait from accelerometer data

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Giovanni Mastromatteo
Giovanni Mastromatteo on 16 Nov 2016
Commented: Sharah on 16 Nov 2016
Hi, I'm testing a LPMS b2-bluetooth-imu board and I get from the device the accelerometer, gyro, magnetometer, Euler angles and Quaternions data.
The idea is to realize something similar to this (
Now, after two integrations of the linear acceleration data for three directions, I have found the resultant displacement.
How could I rebuild the step gait combining the result for each axis?
Thanking you in advance for your help in this matter.


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Answers (1)

Sharah on 16 Nov 2016
What do you mean by "rebuild the step gait combining the result for each axis"?
Usually you would do double integration on all 3 axis x y z. You shouldn't combined them all together if you want the real movement in all 3 direction. On the other hand, if you only require resultant displacement, then you'll combined the data from all theree axis as in:
xyz = sqrt(x^2 + y^2 + z^2)
And if you want a graphical representation of the gait, you will plot the data from all three axis.
Human Robotics Group
Imperial College London


Giovanni Mastromatteo
Giovanni Mastromatteo on 16 Nov 2016
Sorry, I didn't explain well. What i would to track is the gait from the obtained values of displacement in the three axes. I've integrated the arrays of linear acceleration in 3-axis, in the sintax shown below:
vX=cumtrapz(Time, aX);
sX=cumtrapz(Time, vX);
vY=cumtrapz(Time, aY);
sY=cumtrapz(Time, vY);
vZ=cumtrapz(Time, aZ);
sZ=cumtrapz(Time, vZ);
Plotting the resulting arrays for the displacement I obtain these graphs
I wish to track the gait as this example
Thanks for your help
Sharah on 16 Nov 2016
1) Your integration value especially from Z direction looks like there's drift, you might want to remove that
2) the picture you're showing looks like the force measure by a force plate during walking, so not sure what you're trying to see here.
3) If you think about a movement, there will always be a 3D representation of a movement. if you are interested in only the vertical (up and down the movement), just take the value from only that axis (either only x, y or z) depending on your measurement.

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