Herbert Graf wrote:
> > Servos in HDD are also "brushless", position quite precisely under PID.
>
> Very true, but I wouldn't consider them "motors" per se, which is what
> the thread was about.

Yes, you may call them servo drive, that's very close in meaning  to
motor, at least for my level of English.


> A brushless motor isn't very good for positioning since it doesn't have
> a great deal of "holding power" at stall.

It depends on efficiency of close loop. (Encoders provide positioning
information back)


> I'm sure you could devise some PID system to
> turn a brushless motor into a pseudo servo,

Google says that brushless motors are often called servo motors. I
think, you meant that steppers are usually better for positioning than
brushless (servo) motors.


> but frankly a stepper is just so much easier I don't really see the point.

I'm sure (but I can't prove it) that the very brushless (servo) motors
are used in CDs and DVDs to precisely position head, not steppers, for
example.


Best regards,
MS.


PS
Herb, I remember I was somewhat wrong to you a couple of years ago, my
apologies.
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