On Sun, 8 Sep 2019, Gene Heskett wrote:
Date: Sun, 8 Sep 2019 11:44:23 -0400
From: Gene Heskett <[email protected]>
Reply-To: "Enhanced Machine Controller (EMC)"
<[email protected]>
To: [email protected]
Subject: Re: [Emc-users] Step timing and max velocity
On Sunday 08 September 2019 06:55:58 Peter C. Wallace wrote:
On Sun, 8 Sep 2019, andy pugh wrote:
> Date: Sun, 8 Sep 2019 10:50:54 +0100
> From: andy pugh <[email protected]>
> Reply-To: "Enhanced Machine Controller (EMC)"
> <[email protected]>
> To: "Enhanced Machine Controller (EMC)"
> <[email protected]> Subject: Re: [Emc-users] Step
> timing and max velocity
>
> On Sun, 8 Sep 2019 at 04:41, andrew beck <[email protected]>
> wrote:
>
>I can move the table at max speed but the Stepgen PID errors out.
>
>
>Can you elaborate on this?
>PID has no error messages, as far as I know. So what is the actual
> error?
>
>What is PID.n.maxerror set to?
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
I almost guarantee this is the issue, Some earlier versions of pncconf
set this to .0005 as a way to make the stepgen more robust with regard
to host servo thread jitter but the number only makes sense in inches
so fails on metric machines. This should be set so say .0127 on metric
machines (or just 0) to disable the correction limit completely.
Other values:
FF1 = 1.0
P= 1/servo period (so normally 1000)
and if you are very fussy:
FF2 = seconds from position read to velocity write
about 0.0001 on Ethernet cards
And that is the first time I've seen a spec for FF2 that makes any sense,
thank you Peter. What would be roughly correct for a 5i25-7i76 combo?
Probably around 20 - 50 usec so .00002 to .00005
But it will not make a noticeble difference unless you need pulse fidelity in
the <100 uinch range at 1G acceleration hence the "if you are very fussy"
disclaimer
>Is your FF1 correct? In a cruise, using
>halscope, you should see the
>velocity command and the actual velocity pretty much equal.
>
>--
>atp
>"A motorcycle is a bicycle with a pandemonium attachment and is
> designed for the especial use of mechanical geniuses, daredevils and
> lunatics." ???? George Fitch, Atlanta Constitution Newspaper, 1916
>
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Peter Wallace
Mesa Electronics
Cheers, Gene Heskett
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Mesa Electronics
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