Re: Dead zone in stepper power curve

Ted,

Step motors exhibt 2 distinct resonance phenomena; low speed
resonance and midband resonance.

Low speed resonance occurs below 1 rev per second and is
characterized by 2 or sometimes 3 harmonically related resonant
speeds. A typical example would be resonance at 20, 40 and 80 full-
steps per second. Microstepping is the only completely effective
cure, though friction (1st order damping) helps somewhat.

Mid-band resonance is a broader band-width resonance that typically
spans the 5 to 15 revolution per second range. Rate-damping (2nd
order damping) is required to tame this behavior.

It's not your code, it's the motor.

Mariss

--- In CAD_CAM_EDM_DRO@y..., "tedinoue" <etinoue@c...> wrote:
> I was wondering if anybody had encountered this problem. I'm
> developing my own stepper controller system and experience the
> following...
>
> when I run a smooth speed ramp, there are certain speeds at which
> the motor doesn't like to run. Not fast speeds, but slow ones. I'm
> running assembly on a microcontroller, and the pulses are very
> accurately timed.
>
> Depending on how I set the winding power (it's a chopper drive), I
> can tune out these dead spots. Usually by decreasing the power.
>
> Do you think this is a resonnance problem? Or is it more likely to
> be a problem with my code?
>
> I've scoped the waveforms and they are uniform and glitch free
> through the problem speed zone.
>
> Any thoughts?
>
> Thanks,
> Ted