ironbot:
PeterH,There's nothing stopping you from putting a feedback loop on your motor control
Well, unfortunately what is stopping me is lack of skills in control theory: I've not done the homework, not finished a single control theory book (but have chosen what to read, it has matlab simulations to pass to hopefully couple theoretical understanding with some intuition). I'd give a try to the PID lib you kindly suggested but hardly imagine that in this concept any good result comes without sound theoretical background and gained intuition in putting them to work.
You may be surprised how easy it is once you have got your head around the basic concept. Instead of giving a movement command and assuming that the actuator ends up in the correct position, you find the current position and compare it to the desired position and tell it to move in the right direction. This is basically all you are trying to achieve. The PID algorithm is a feedback algorithm that works very well in a wide variety of situations which is why it is so popular. As well as dealing with the position, it also deals with the speed and acceleration which I suspect will be important to you when you're trying to move and position elements with a lot of inertia.