In my recent search for some "simple, cheap and cheerfull" methods of servo motor torque control of a Flight Simulator Jack, I discovered this most useful site that might be helpful to some builders who are agonising over some practical and theoretical FS building matters!

http://www.educypedia.be/electronics/motorservo.htm

The site is well worth fully exploring as it is an extraordinary mine of very usefull information on many useful subjects.

Bill.