How to integrate a list of 3-axis Accelerometer data to velocity and location in python?

Question

I get a list of acceleration and gyroscope data from the myo armband. The acceleration data is given like [[-0.11474609375, -0.13037109375, 0.9873046875], [-0.111328125, -0.12890625, 0.9892578125], [-0.11376953125, -0.12255859375, 0.98828125]...] where the values represent each the x,y and z axis values. I know to get the velocity, you have to integrate it once and for the location you have to double integrate it.

The problems I encounter are:

• In some questions/articles/answers it's stated you need the initial velocity to correctly calculate it. But how do i get it from the accelerometer (and/or gyroscope) data?
• For the quad function from scipy a function is required to integrate the data. How do i find out which function is correct? Can i just take f(x) where x is the current value and iterate over all values?
• The same question is for dblquad, just that it takes multiple values.

The time period for those collected data is relatively short (around 5-7 seconds), so i don't think that the error drift will sum up much in this time.

Background: Those data is needed as an feature for ML algos with detecting handwritten letters. So velocity might vary due to the point since each person writes with a different tempo, but an average tempo could be used.

Some question already asked like this refer to real positioning, which isn't my goal. Also would this be enough aka just summing up without using the integration at all?

Answer 1

Hello Luka answering to your question the answer is: yes it is posible if you add a gyro into to mix to estimate the position hence the velocity but it is hard and not too reliable (depnding on the accuracy and precision of your sensors).

What you are proposing is an inertial navigation system, which works on the principle of detecting the subtle changes in acceleration with respect to a given inertial-frame, in this case the planet Earth which rotates at a constant speed. For more in depth info I found this article hope this helps!

Answer 2

They are correct you cannot determine the velocity from just the acceleration. Remember that accelaration is the rate at which the velocity changes... so for instance if you had an object who went from 0 m/s to 10 m/s in 1s its acceleration would be calculated by applying the following formula a =(vf-vi)/t which would result in (10-0)/1 =10 m/s^2 and if on the ohter hand you got an object who went form 100m/s to 110 m/s you would still get the same acceleration.

To know the velocity you would neet to know the position of the object, remember that velocity is the rate at which an object changes position from a certain reference-fram, dji's drones fro example use GPS coordinates to estimate its velocity relative to ground.