Hi, 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.