I'm looking for a simple principal to build an 'automatic hammock rocker'. I would imagine this is a classic control system problem.
The system should be able to pull the hammock to one side, up to a certain force, then release the force and start pulling at the opposite side. By using forces (and not distance or speed) it should be possible to start from a non-moving situation and then generate very tiny movements, which gradually get larger, until a certain maximum swing-radius, were the force needed for additional swing equals the maximum force delivered by the control system.
This system would require some form of 'force-measuring' device. This could be done by using springs. The only design I could come up with is a system of 2 electromotors continously running in opposite directions, and a cogwheel, that 'feeds' of motor1 (forward), motor2 (backward) or none at all (neutral). This 'gear selection' could be done by a set of springs, that measure which force is needed. The cogwheel could pull the hammock ropes
(Motor1) O s (spring) s (cogwheel) o--------* (pivot) s (Motor2) O s (spring)
Any thoughts ?