stepper motor speed ramp

[david austin]

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

 

[Bill Sloman]

"david austin" <dave@slotech.fsnet.co.uk> wrote in message news:<bphlkj$bgc$1@news7.svr.pol.co.uk>...

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

 

[david austin]

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

"Bill Sloman" <bill.sloman@ieee.org> wrote in message
news:7c584d27.0311200601.47c0a230@posting.google.com...

"david austin" <dave@slotech.fsnet.co.uk> wrote in message
news:<bphlkj$bgc$1@news7.svr.pol.co.uk>...
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

 

[Trevor Barton]

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

"david austin" <dave@slotech.fsnet.co.uk> wrote in message news:<bphlkj$bgc$1@news7.svr.pol.co.uk>...
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

Well that's all very well, but I've never heard of a stepper motor
driver that does anything other than linear or s-curve accelerations,
but then I guess I've only seen about half a dozen

--
Trevor Barton
Isotek Electronics Ltd, 9 Clayton Wood Bank, Leeds, LS16 6QZ, UK.
Tel: +44 (113) 275 1339, Fax +44 (113) 224 9827
Remove X from tmb@Xisotek.co.uk before replying.
Views expressed are my own and not necessarily those of Isotek Electronics Ltd.

 

[Bill Sloman]

"david austin" <dave@slotech.fsnet.co.uk> wrote in message news:<bpijm0$epg$1@newsg2.svr.pol.co.uk>...

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" <bill.sloman@ieee.org> wrote in message
news:7c584d27.0311200601.47c0a230@posting.google.com...
"david austin" <dave@slotech.fsnet.co.uk> wrote in message
news:<bphlkj$bgc$1@news7.svr.pol.co.uk>...
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

 

[Stephen Pelc]

On Thu, 20 Nov 2003 16:14:08 GMT, Trevor Barton <tmb@Xisotek.co.uk>
wrote:

Well that's all very well, but I've never heard of a stepper motor
driver that does anything other than linear or s-curve accelerations,
but then I guess I've only seen about half a dozen

A long, long time ago I did the software for a six axis machine
that cut patterns on glasses and decanters. The first time we
tried an S-curve, we hit the low-frequency resonance problem
and the motors stalled. Both resonant regions are important.

Stephen
--
Stephen Pelc, stephenXXX@INVALID.mpeltd.demon.co.uk
MicroProcessor Engineering Ltd - More Real, Less Time
133 Hill Lane, Southampton SO15 5AF, England
tel: +44 (0)23 8063 1441, fax: +44 (0)23 8033 9691
web: http://www.mpeltd.demon.co.uk - free VFX Forth downloads