Fuzzy logic is used for more than mechanical control. See, for instance:
-Will
if you want an accelerometer that'll operate a high frequencies use a voice-coil and integrate the output.
Bye. Jasen
Some folks have tried this; there was even an article in a recent AudioXpress about using a dual-coil subwoofer off the shelf with one coil as a feedback winding.
The problem with this is that it's hard to avoid coupling between the two coils.
--scott
-- "C\'est un Nagra. C\'est suisse, et tres, tres precis."
That's how the old Philips did it, 2 coils on the former, larger one to drive, small one for the FB signal.
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There was an article in the magazine "Power Conversion and Intelligent Motion" some years back where they made a sub woofer with a servo motor driving the cone. You may want to see if you can find the article.
The highest frequency at which the servo should have its gain cross over point is going to be lower than where the coil input to feedback signal gets to be 180 degrees. The "D" part of the PID controller will give you about 45 degrees of phase lead at the cross over.
There could be a problem if the signal frequency is a subharmonic of the gain cross over frequency. Distortion products can be increased at the gain crossover. If you imagine that the distortion is a signal added at some point within the loop, I think you will see why this is true.
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