magnetic spindle bearings

Has anyone looked at magnetic spindle bearings?
IBAG ( http://www.ibag.ch/e/index.shtml makes these things, they claim
stiffness similar to ball bearings, 200,000 rpm, up to 125 HP (maybe not all
at the same time).
Evidently there is servo action to adjust the magnetic field and keep the
spindle centered. One could imagine capacitive sensors, servo circuitry,
and coils to push the spindle back to center made as part of the motor.
Capacitive sensors have been made good to nm, and 200,000 rpm is only 3000
Hz, not a very high speed for analog circuitry.

These are used for high speed machining of hard materials to get smooth
surfaces, and are evidently a step up from hydrostatic bearings.
The bearings are ranked as follows:
ball bearings-> limited stiffness at high speed, moderate accuracy
hydrostatic (liquid) bearings-> good stiffness and accuracy, large drag at
high speed
air bearing-> high accuracy & speed, limited stiffness
magnetic-> high accuracy, speed, and stiffness. Cost is way up there!

Since this is a servo used in machining operations, is it a suitable topic
for CCED?

A similar technology could be (is) used for linear motors and ways, which
would be way cool to bring to the home shop.

By using a high speed spindle the frequency is raised to a point where
electromagnetic drives are efficient. For example, think of a loudspeaker.
Your woofer is 20X larger than the tweeter, yet they produce roughly the
same output power. The main difference the frequency and electromechanical
coupling efficiency at high frequency.

It might be fun to make a simple one just to play with, even if it didn't
get all those big numbers.
The expertise of this group has brought the cost of CNC down considerably in
the last few years, perhaps it can do the same for high speed spindles.

Elliot B.