Well, it is hard to say, I think there is a limit to the base period (at
least I saw that in my machines) and it is about 10000 to 15000 ns. If I
decrease it, everything froze. Said that, an approximated formula that gives
you an idea of the needed base period is:
BASE_PERIOD = 1 / ( INPUT_SCALE * MAX_VELOCITY * 2 ) * 10^9
The value of INPUT_SCALE * MAX_VELOCITY is the max number of step per
second you will need, you double this value to be sure you will be able to
obtain the step per second you need. The inverse is the time in second
between a step and the successive at the max speed doubled. You multiply for
10^9 to obtain ns.
With your data, you should be ok with a Base-Period of 12500, and that
should be ok for your machine.
Dont' forget to update the STEPGEN_MAXVEL value accordingly to the MAX_VEL
value. It should be a little more than the MAX_VEL. Also remember that in
the formula above, you should put the STEPGEN_MAXVEL value and not the
MAX_VEL...
I hope this helps.
Regards,
Manfredi
My websites: www.m24-pro.com
www.emc2cnc.altervista.org
>From: Cecil Thomas <[EMAIL PROTECTED]>
>Reply-To: "Enhanced Machine Controller (EMC)"
><emc-users@lists.sourceforge.net>
>To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net>
>Subject: [Emc-users] Max speed too fast
>Date: Thu, 23 Aug 2007 01:11:15 -0500
>
>I am using EMC2 and a gecko servo drive to drive a servo I have
>mounted on my Millrite.
>When I set the max speed to 1.0 (I think that is 1 ips or 60 ipm) I
>get an error saying that the velocity is too high.
>I the motor/encoder/gecko drive require 2000 steps per rev and the
>lead screw is 5 tpi and I have a 4 to one timing belt pulley
>reduction between the motor and the axis so the input scale is 2000 x
>4 x 5 or 40,000 steps per inch.
>This requires 40,000 steps per second for 1 inch per second.
>
>I am using a 2 GHZ machine and I think I can get a higher step per
>second output by changing the base period and the associated periods
>but I am a little fuzzy on the relationship. I saw this explained
>here sometime in the last few months but I can't find it in my
>inbox. How do I relate max steps per second to base period? What
>is the minimum base period for a given cpu clock speed?
>
>Can someone refresh me on maximum speeds and minimum base periods etc. ?
>
>BTW I really don't need 60 ipm but it looked like a good max speed
>and the servo will do it with a squarewave generator input to the
>gecko drive. I could live with half that or so as the max traverse speed.
>
>Thanks,
>Cecil
>
>
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