Re: Simple Question: Rotations
It depends on what kind of turn you are making. For example, are you turning the left and right wheels with equal power but in opposite direction (turn in place)? Or are you turning with one wheel stopped and other wheel forward (swing turn)? This affects the pivot point. Assuming you are turning the wheels in opposite directions (turn in place), your pivot point will be the centroid between the four wheels (or however many wheels). Then you can use the following. It will give you a good initial value but you may still need to fine tune it for compensating inaccurate measurement and real world factors.
Basically, if you turn in place, you are drawing a circle on the ground with the center of the circle being the centroid of the wheel base with the diameter approximately equal to the distance between diagonal wheels. Therefore, you first translate the number of encoder ticks to the distance travelled on one of the wheels. Then assume the wheel is travelling along the circumference of the circle, you can calculate the relationship between the distance travelled and the degrees turned.