Piezo mechanical actuators of various sorts are available
commercially.

Philips make piezo building block materials meant for this sort of
purpose.
They have a leaflet (book maybe) covering potential and real
applications.
AFAIR one application is pneumatic valves where the piezo crystal is
the sole source of mechanical actuation.

All that said, piezo is probably best suited for small movements.
Real world servo applications may be rather too gross motion
demanding to be an optimum application.

Then again - I have read that that "people" are attempting to develop
a piezo actuated helicopter rotor (full size) - piezo controlled
flexing replaces the 2000 odd components in a normal cyclic head.
Multiple piezos are distributed along the rotor blade. That sounds
like a very real-world servo application :-).



    Russell McMahon.




From: Mel Evans <MEvans1027@AOL.COM>
Subject: Solid-state servo


>    I need your help in developing a new device -- a piezoelectric
servo.
>Remember the crystal (or ceramic) phono cartridge, where, if
something (like a
>phono record) wiggled the needle, you got a voltage on the output
terminals?
>Shouldn't it also work backwards?  That is, if I put a voltage on
the
>terminals, shouldn't it wiggle the needle?

>Do any of you old-timers know how they really work?  Or know any
>retired Astatic engineers who might like some consulting work?
>-- Mel Evans    mevans1027@aol.com      727-595-7685      fax:
727-595-7680
>