Polynom of phi -> derivate to [mm/rad] and [mm/rad^2]

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Christian
Christian on 18 Jan 2017
Edited: Christian on 19 Jan 2017
Hello everybody, I need your help!
I have a huge dataset for an ellipse.
Column 1 = degree from 0° -> 360°
Column 2 = radius (I define it as distance from the center) -> s [mm]
In the end I would like to plot the angular velocity [mm/rad] and the angular acceleration [mm/rad^2]. Therefor I used polyfit to get a function for the radius in dependency of degree -> s(°) with the unit [mm]
Now I would like to diff this function to get the angular velocity [mm/rad] and the angular acceleration [mm/rad^2].
The math looks like this:
s_dot = ds/dt = ds/dphi * dphi/dt = ds/dphi * omega
I have already tried it in several ways, but I’m not able to succeed.
Many thanks in advance!
Cheers
Christian
  5 Comments
Christian
Christian on 19 Jan 2017
Yes, you might be right! 'radial velocity' is what I mean. My ellipse is on a shaft which rotates. So the change of the radius causes a radial velocity for all points on the brink of the ellipse.
You could compare this problem to a camshaft where the velocity of the points on the brink of a cam looks like this:
Christian
Christian on 19 Jan 2017
Edited: Christian on 19 Jan 2017
I solved it!
s_strich=gradient(s, Shaft_deg).*(180/pi)
I used the diff function all the time, but the gradient function is what I was looking for. Simple as that :)

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