On Thu, 15 Jul 2010, Chris Radek wrote:
> Date: Thu, 15 Jul 2010 11:06:27 -0500
> From: Chris Radek <ch...@timeguy.com>
> Reply-To: "Enhanced Machine Controller (EMC)"
> <emc-users@lists.sourceforge.net>
> To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net>
> Subject: Re: [Emc-users] Spindle at speed & Coordinated Motion problems?
>
> On Thu, Jul 15, 2010 at 08:42:34AM -0700, Peter C. Wallace wrote:
>
>>
>> Not quite, I was suggesting tossing bad data so even if the velocity is
>> filtered the bad data does not contribute to the average
>
> pid can now be hooked to an index-enable signal so it knows when
> there's a (possibility of a) position jump that needs to be handled in
> a special way.
Perhaps even better (at least for HostMot2 and maybe the software
encoder) would be a velocity input port on the PID component, since the
velocity output of the encoder component has no jumps at index.
I am assuming here that the position jump should be have no direct
effect (P term) since the commanded position and feedback position should
"jump" at the same time, and the only effect of the position jump is to mess
up the DDT velocity calculations for the D term. I guess the FF1 and FF2
calculations still need to skip DDT calculation for a cycle at index...
>
> ddt could also have this capability but it's only useful if ddt is
> used specifically for this one task.
>
> It is better to tell ddt when its input is bad, instead of making it
> guess, so if we must add this I'd prefer it be done that way.
>
> But really I think the special handling of an encoder event belongs in
> the encoder driver, not ddt.
Sure, but until there's someone to do the driver work this may be a
work-around.
>
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Peter Wallace
Mesa Electronics
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