stepper motor speed ramp

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
Dave Austin
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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
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On Thu, 20 Nov 2003 06:01:30 -0800, Bill Sloman wrote:

A linear (or S curve or low jerk etc etc) ramp is just fine for a stepper as long as you use microstepping so that you do not exite the resonance. Any kludge that limits your flexibility in choosing acceleration or velocity would be extremely painful to deal with in a multi axis system...
Peter Wallace
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Here's a nice kludge on a 343-axis stepper farm.
http://taomc.com/stepperarray/stepperarray.htm
It sure was fun fun fun!!!
MAN, 100 Amps at 4.25 Volts takes BIG wire.
--
- Alan Kilian <alank(at)timelogic.com>
Director of Bioinformatics, TimeLogic Corporation 763-449-7622
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On Tue, 25 Nov 2003 02:37:42 GMT, snipped-for-privacy@raceme.UUCP (Alan Kilian) wrote:

Dang, I love it! Neat hack.
--
Rich Webb Norfolk, VA

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Agreed. Microstepping almost always allows you to operate at stepping frequencies well above the motor resonances, and if by chance you do happen to hit a resonance anyway, the amplitude of the oscillation is almost certanly going to be too low to drive the system out of its piece-wise linear range.
I was in involved in a cheapish stepper-motor controller development back in 1992, where we used a bottom-of-the-line Transputer chip to get the processing band-width to calculate micro-step up-dates in real time in a single processor.
Regular microcontroller chips of that period couldn't hack it. I would have preferred to use a decent-sized programmable logic device, but the software guys found the Transputer to be much more congenial programming environment.
Knowing the resonant frequencies of your motor-load combination can let you use cheaper,dumber controllers, but it takes work, and you have to be reasonably confident that these resonance freqencies aren't going to change when the buyers find a cheaper stepper motor ....
-------- Bill Sloman, Nijmegen
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