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I want to find the instantaneous center of rotation of a differential drive robot. Assuming I know that the robot will travel with a particular linear and angular velocity (v,w) I can use the equations (given here http://rossum.sourceforge.net/papers/CalculationsForRobotics/CirclePath.htm ).

which come out to be

x_c = x_0 - abs(v/w) sin(\theta_0) y_c = y_0 - abs(v/w) cos(\theta_0)

I'm using the webots simulator and I dumped gps points for the robot moving in a circle (constant v,w (1,1)) and instead of a single x_c and y_c I get a center point for every point. if I plot it out in matlab it does not look nice.

Here's an image ...

the red points in the image are the perceived centers

https://docs.google.com/file/d/0BzLnU1-OKHh7dmxvbGU1bDFKcFU/edit?usp=sharing

they just seem to trace the curve itself.

is there some detail I am missing ? I'm really really confused as to whats happening.

help please

I'm trying to figure out the center so I can check whether an obstacle is on this circle or not and whether collision will occur.

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# Instantaneous Center of Rotation for a Differential Drive Robot

Can you offer guidance or do you also need help?

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