I need to assemble a small (about 8cm x 5cm x 5cm maximum), actuator with as much torque as I can get at that size. It will be driving a small reel and pulley (reel is ~1.25cm^3, 5mm center diameter), and needs to respond to load (eg. stop if the load increases beyond a certain threshold). Power to the actuator will be provided via a common bus line, so the space limit isn't further limited by the size of the battery.
My thought is to use a worm drive for this (for torque) and watch for change in current/voltage (for load), but I'm not sure if that is mechanically sound. It seems like the mechanical advantage provided by the worm would make it hard to detect a change in load.
I could add another sensor that would gauge the force being exerted. I'd prefer to avoid adding too many points of failure to the system, but if I did what sort of sensor would I use?
How should I approach this?