On Mon, 2008-03-10 at 12:55 -0400, Gene Heskett wrote: > On Monday 10 March 2008, Kirk Wallace wrote: ...snip > No, it can serve to absorb it, quite well from my experiences so far. Common > sense says the weight of the damper will lower that frequency somewhat also. ... snip
Yes, I agree. I must have gotten up on the dumb side of the bed today. > >I also noticed > >from other threads, that the voltage the stepper is driven with can > >change the resonance frequency. > > Yes, the higher the voltage, within limits the stiffer it will be in that rpm > range where the inductance of the motor is costing it torque. Below that > range it should be a wash cuz the driver is chopper regulating the current > and therefore the strength of the magnetic spring action. > > >I think the ideal would be to move the > >resonance above the maximum operating speed, so you never see it in > >normal operation. I should have said, move the resonance down. (or convert to heat or something else as you mention above.) > That would take a new concept in current profile control, and even then may > not work well as the spikes of high current that would imply might be high > enough to demagnetize the rotor, and effectively reduce its power forever. > > >Isn't micro stepping the most effective tool against > >resonance? > > Yes, the finer the better although going beyond 8 steps does seem to be an > area of diminishing returns. > > >Or maybe an RC filter on the driver outputs to help shape the > >voltage. > > Absolutely not. The inrush currents in any capacitance would quickly > overheat > and destroy the H bridge components in the output stage, and any resistance > there is pure power loss. We are cautioned to not even hook a scope probe to > a motor lead because of its added capacitance. Ops, another mistake. What I was trying to say is, there might be widely different ways to change the output signal shape. > >Of course EMC is flexible enough to be able to set up some sort > >of feedback to mechanically or electrically change the stepping > >characteristics. > > There are others here who can describe the sharpness of the stones in that > path far better than I. I'll only say its a rocky road. :) > > >Brushless DC motors are just low pole count steppers aren't they? I > >wonder if a stepper driver could be used to drive a BLDC? Though I > >suppose a BLDC driver might be better. > > And that is another area I'll invite others to comment on. > > -- > Cheers, Gene Thanks. I knew there was a reason I keep yuz guys around. -- Kirk Wallace (California, USA http://www.wallacecompany.com/machine_shop/ Hardinge HNC lathe, Bridgeport mill conversion, doing XY now, Zubal lathe conversion pending) ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
