Re: [ATM] Voice coil actuators was: DC Motor for grinding machine question

["Don Clement" <don_clement@charter.net>]

 The "small" S-Series of Unholtz-Dickie electrodynamic shaker systems  have
up to 8.5K lbsf see: http://www.udco.com/sseries.htm

"Electrodynamic" is another term for voice coil actuator. The new U-D shaker
amplifiers are 90% efficient air-cooled class D switchers. Did someone say
PWM?





Don Clement

Running Springs, California



>
> I am not sure about "voice" coil actuators specifically, but have
> seen very powerful selenoids, etc using same basic physics. I am
> very confident such devices could be used.
>
> Dominic
>
> On Mon, 20 Nov 2006, GARY FUCHS wrote:
>
> > Don,
> >
> > That was probably a basic explanation, but still mostly over my head.
> >
> > It looks like voice coil actuators move linearly. If that's true, won't
you need to convert that to rotary motion? If so, how?
> >
> > And if it's going to be driven by an audio amplifier, won't the
amplifier need to be pretty powerful if the voice coil actuator is going to
be pushing a polishing tool around?
> >
> > What am I missing?
> >
> > Gary
> >
> >
> > >
> > >Gary,
> > >
> > >
> > >
> > >Voice coil actuators are neither complicated nor expensive. A good
> > >explanation can be found here:
> > >http://www.consult-g2.com/course/chapter11/chapter.html
> > >
> > >Voice coil actuators are commonly found in just about everywhere in the
form
> > >of the loudspeaker. Voice coil actuators are simple enough to be built
by
> > >the ATMer. I plan to use voice coil actuators because of the simplicity
of
> > >driving them using off-the-self audio amplifier and off-the-self D/A
cards
> > >with a PC. The pseudo random driving signals are easily generated in
> > >software in the PC. I am using my favorite all-graphical software NI
LabView
> > >to do this.
> > >
> > >
> > >
> > >Don Clement
> > >
> > >Running Springs, California
> > >
> > >
> > >
> > >> Thanks Don,
> > >>
> > >> I looked up voice coil actuators - very interesting - though I didn't
> > >understand much. The ones I saw looked like they weren't for continuous
> > >motion. Is that true of all, or am I just not making sense of it? If
so, how
> > >would you use them for the machine?
> > >>
> > >> They also look expensive...
> > >>
> > >> With their rapid acceleration/braking/reversing and ability to move
in
> > >very small increments would these be better than other motors for scope
> > >drives?
> > >>
> > >> Thanks,
> > >>
> > >> Gary Fuchs
> > >>
> > >>
> > >>
> > >> >
> > >> >Gary,
> > >> >
> > >> >
> > >> >
> > >> >Periodic error by definition would produce a regular pattern.
Machines
> > >that
> > >> >use the same drive for spindle rotation and also drive the tool will
have
> > >> >some synchronization and produce periodic component. That's why my
> > >machine
> > >> >will use two independently driven voice coil actuators to drive the
tool.
> > >We
> > >> >could test that theory by using the Lyot phase-contrast method and
look
> > >for
> > >> >any effects of periodic error on the machine polished surface.
> > >> >
> > >> >
> > >> >
> > >> >Don Clement
> > >> >
> > >> >Running Springs, California
> > >> >
> > >> >
> > >> >
> > >> >> (First, thanks for the VFD info. That's on my Christmas list.)
> > >> >>
> > >> >> Don, Mike, et al?,
> > >> >>
> > >> >> I'm probably in over my head here, but why wouldn't the periodic
error
> > >I
> > >> >think you're talking about actually be beneficial, making the
machine's
> > >> >action just slightly irregular and more human-like? Don't typical
> > >machines
> > >> >have at least two places where periodic error would occur, but not
at the
> > >> >same time?
> > >> >>
> > >> >> Gary Fuchs
> > >> >>
> > >> >>
> > >> >> >
> > >> >> > Mike,
> > >> >> >
> > >> >> >
> > >> >> >
> > >> >> >We could test that theory.  Perhaps using technique mentioned by
> > >Texereau
> > >> >in
> > >> >> >"How to make a Telescope", the Lyot phase-contrast method. One
could
> > >do a
> > >> >> >spatial spectrum analysis on the machine polished surface using
the
> > >Lyot
> > >> >> >phase-contrast method to detect any periodic contribution due to
the
> > >> >regular
> > >> >> >arraignment of balls in a ball bearing race. Since spindle rpm is
> > >known
> > >> >and
> > >> >> >the ball bearing race configuration is known, one would know what
> > >spatial
> > >> >> >frequencies to surface roughness to look for.
> > >> >> >
> > >> >> >
> > >> >> >
> > >> >> >
> > >> >> >
> > >> >> >Don Clement
> > >> >> >
> > >> >> >Running Springs, California
> > >> >> >
> > >> >> >
> > >> >> >> Don,
> > >> >> >>
> > >> >> >> Don Clement wrote:
> > >> >> >> > There is no contradiction.
> > >> >> >>
> > >> >> >> Yes, there was.  In one message you said there was no effect,
then
> > >in
> > >> >> >> your next message you said there was.  Maybe it was a typo.  I
was
> > >> >> >> just trying to follow your reasoning.
> > >> >> >>
> > >> >> >> > Using a FFT Dynamic Signal Analyzer
> > >> >> >> > (such as the Agilent 35670A) and the proper sensors one can
see
> > >the
> > >> >> >> > effects of rotating equipment using ball bearing races. In
fact,
> > >> >> >> > one can determine detailed information on the ball bearing
race
> > >> >> >> > parameters (such as number of balls, etc) by examining the
> > >spectrum
> > >> >> >> > of rotating machinery. There is no doubt that regular spaced
balls
> > >> >> >> > in ball bearing races add some periodic component to a
rotating
> > >> >> >> > spindle of a polishing machine.
> > >> >> >>
> > >> >> >> I have no doubt you are correct in that statement - my day job
is
> > >> >> >> signal processing and I play with FFTs all day.  I also have no
> > >doubt
> > >> >> >> that the vibrations affect the quality of finish in metal
working,
> > >and
> > >> >> >> I found your post about 3-phase motors and speed controllers
very
> > >> >> >> interesting and useful.
> > >> >> >>
> > >> >> >> However, I debate your assertion that the miniscule vibrations
will
> > >> >> >> cause measurable effects on the surface of a mirror being
polished
> > >on
> > >> >> >> a machine.  I certainly haven't detected any on my DC
motor/variac
> > >> >> >> setup, or on a machine that uses a PWM controller.
> > >> >> >>
> > >> >> >> I guess you'll end up with a grinding machine that can double
as a
> > >> >> >> decent turntable for playing vinyl, should your Marantz
experience
> > >> >> >> problems.  :)
> > >> >> >>
> > >> >> >> (Yes, I know vinyl often sounds better.)
> > >> >> >>
> > >> >> >> Mike Lockwood
> > list http://www.atmlist.net/
> > _______________________________________________
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> >
>
>

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