Kirk Wallace wrote: > > I think you stated the crux of the problem with "there is no way to > avoid a condition where a stepper motor is operating at a step rate > where resonance is present." > > The mechanical damping can move where resonance happens. I also noticed > from other threads, that the voltage the stepper is driven with can > change the resonance frequency. I think the ideal would be to move the > resonance above the maximum operating speed, so you never see it in > normal operation. Isn't micro stepping the most effective tool against > resonance? Or maybe an RC filter on the driver outputs to help shape the > voltage. Yes, this has actually been done in the distant past. The problem is that mid-band resonance ocurrs at rather low speeds and therefore frequencies. This necessitates really big capacitors in an RC series circuit parallel to the phase coils. An active method works much better. Of course EMC is flexible enough to be able to set up some sort > of feedback to mechanically or electrically change the stepping > characteristics. > Yes, but then you'd get into all sorts of tuning issues, so you'd need encoders to see what is happening. Soon, it starts to look like a servo. > 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.
Yes, a software-driven stepper drive is pretty close to what you'd need, but almost all BLDC motors are 3-phase. You also need inputs to read the encoder or Hall sensors. I've been working with BLDC motors here and have made a simple BLDC motor drive. It is only slightly more complicated than my DC Brush drives - mostly adding a 3rd half-bridge stage to the full-bridge driver section. Jon ------------------------------------------------------------------------- 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 [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
