I was wondering how do memory seats keep track of their position. Since this kind of equipment existed in 1990's cars, it must be simple yet ingenious. I have been thinking about this for quite a time now and cannot figure out how it works (without tearing apart a donor car).
So as to keep it simple, let's only consider the forward / backward position of the seat. Usually, we have buttons for 3 memories.
Seats could be using a default position as a reference paired with a duration of movement of the electric motors, but they would need to go back to this position when you press a button to recall a memorized position before moving to the right position. Since they go straight to the right position, I guess it's not how it works.