How can I make an EV3 vehicle follow an elliptic equation? Has anyone succeeded in having the EV3 driving base moving following an ellipse? I would like the kids to think about how would we program a satellite orbiting around earth. 

They would input the equation for the ellipse and then they will have the robot driving around it. Any thoughts?
I think it would be more realistic to have the robot drive in a straight line but have a linkage to the foci of the ellipse that "pulls" the robot towards the center of the ellipse just as orbiting objects are pulled toward Earth by gravity.

For example, you could use two nails in a board as the foci. Tie a string in a loop to use as the linkage. Place the string loop around the nails and attach to the side of the robot. Drive the robot forwards (no steering). It will travel in an ellipse. You could even attach a pen to the robot to draw the ellipse.