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From: a0014246@unicorn.it.wsu.edu (mark fuller)
Subject: Re: microstepping (?)
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Date: Sat, 21 Jan 1995 05:21:36 GMT
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Steve Gillen (steve@phy-server) wrote:
: Bernhard Greissing (berni@nugat) wrote:

: : Hi there!

: : There's a method for controling stepper-motors called 'microstepping'.
: : Is there anybody who can tell me how this works and 
: : about the benefits of this method.

: Yes... Microstepping does involve varying the current in two adjacent 
<deleted>
:   My only worry about using a stepper motor (and maybe even syncros)
: at low speed or stopped is the shape of the poles on the windings and
: armature.  I suspect (ok... Guess) that the angular position is not linear
: with the ratio of the currents in the windings.  In other words, two sine
: waves 90 degrees out of phase may NOT give a linear angular (oxmoron or 
: what?) motion.  It probably depends on the specific motor as to the exact
: waveform if you want precise positioning.
:   People are welcome to add/correct me.  I belong to the postulators 
: anonymous :)
:   Hope this helps.
:                            Stephen Gillen
:                            Queen's University Physics
:                            Kingston, ON, Canada

: Note: !!!  I speak for mysELF.   My employers speak for themsELVES.
:            And most ELVES don't speak to either of us.
: A
:            anything I say.
What you can do, if the manufacturer doesn't have the specs for the stepper
is to measure the change of angle or possibly the ripple in rpm(for higher
rotational rates) and use this data to apply a correction factor to your 
sine tables.  You might have to have a variable correction factor dependant\
upon rpm as the ripple effect may change for different rates.  Another
 possibility is to use feedback from a resolver to provide correction for
rpm ripple.

Mark Fuller
TANSTAAFL
