Actually there are a couple of things we can do to prevent the backlash problem: (1) Use a worm gear motor with self locking feature, (2) Use control tricks such as PID (digital) or trapezoidal travel pattern: (a) start accelerate moving fast to max speed, (b) then move at max speed to almost reach position/degree, say 160 degrees, then (c) deccelerate to zero while moving the last 20 degrees, so reaching the last degree/cm at almost zero speed, thus prevent overshooting.
