Pop up robot.
I plan on having some sort of actuator, near each ‘pole’ of the robot, then having cheap IRs or 2 ultrasonics pop out every so often. OR, I could make some sort of linkage to the ball that lets it spin, as well as not tangling wires around an axis screw. Then, I permanently aim them forward, and send it on its way.
Assuming that your IR
Assuming that your IR emitter/detector pair will be in the same relative postiion in the ball at all times - i.e. the same height off the ground, and pointing in the same direction - then the optics shouldn’t change from time to time. So can you not simply either calculate, estimate, or empirically measure some kind of fudge factor to scale up the distance you measure from the IR sensors?
Possibly
This project is parked until I get my Mr. General Competition robot done, and my Xmos started. But that’s an excellent Idea, I think I’ll use it.