power chucks, bar feeders etc

I'm just wondering if anyone knows much about the operation of the
typical power chuck?

I'm mentally designing a small swiss-style lathe and I can't work out
how to automate the rear chuck, it needs to be able to grip and
release bar stock at will even at low speeds (i.e. no centrifugal chuck).

I've seen wedge based chucks mentioned but you only seem to get to see
the outside of commerical ones.

My only real idea has been a spring loaded collet chuck with springs
to keep the chuck closed on the bar stock and an external pneumatic
mechanism to release it when required.

Only minimal accuracy is required in terms of centering so I feel
there must be some neat and dirty solutions out there somewhere.

Graham