Re: stepper motor speed ramp

"david austin" <[EMAIL PROTECTED]> wrote in message news:<[EMAIL PROTECTED]>...
> The method can cope with Bill Sloman's objection by building a
> piecewise-linear acceleration profile.
> My experience is that this is not necessary
> Dave Austin

I hope your lucky break continues. A lot depends on how dissipative
your load is. Several of the steppers I've played with had a fairly
high-Q first resonances, and the starting sequence that worked
involved enegergising the coils for several cycles of the resonant
period, until the rotor had settled down aligned with the magnetic
field, then making the first step period one quarter of the inverse of
the resonant frequency.

Do it wrong, and the rotor doesn't rotate, it just sits there buzzing
at the stepping frequency, which isn't helpful.

--------
Bill Sloman, Nijmegen

 
> "Bill Sloman" <[EMAIL PROTECTED]> wrote in message
> news:[EMAIL PROTECTED]
> > "david austin" <[EMAIL PROTECTED]> wrote in message
>  news:<[EMAIL PROTECTED]>...
> > > This site has a pdf with a neat method to generate timings for a linear
> > > ramp.
> > > It is quick enough to do in real time in a timer-comparator ISR on a
>  PIC.
> > >
> > > http://mysite.freeserve.com/stepper
> >
> > A linear ramp isn't all that helpful in accelerating a stepper motor.
> >
> > If your maximim stepping rate is higher than the first resonance
> > frequency of the stepper motor you are using, you do have to chose
> > your acceleration sequence with the resonant frequency in mind, and an
> > arbitrary linear ramp probably won't serve. Read Douglas W. Jones on
> > the subject.
> >
> > http://www.cs.uiowa.edu/~jones/step/physics.html
> >
> > -------
> > Bill Sloman, Nijmegen