On Thu, 22 Jun 2017, andy pugh wrote:
Date: Thu, 22 Jun 2017 00:06:42 +0100
From: andy pugh <bodge...@gmail.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] following error only while homing
On 21 June 2017 at 19:36, Peter C. Wallace <p...@mesanet.com> wrote:
The stepgen is not computing following error it just cant be driven by a
position command with a stepwise discontinuity and move instantaneously to
the new position.
I think it might be more interesting than that. Stepgen commanded position
and encoder position track each other very well, and the f-error is small
throughout.
https://docs.google.com/spreadsheets/d/1qRVyQWFl4BIsSNKwy9IYsXrmZLTK8vgVVNX4tAuUmJM/edit?usp=sharing
--
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
Only because the step was small (because it was probably not the first time
homed)
Take a look at axis.0.motor-pos-fb and axis.0.motor-pos-cmd in Sebastians test
on a servo system:
http://highlab.com/~seb/linuxcnc/homing-x-first-time.png
Notice the (probably multi-inch) jump to 0 when index is detected
A velocity mode servo system can cope with this because the PIDs command and
feedback step at the ~same time (and there are some patches to fix derivative
related problems in the PID comp when index is detected)
Peter Wallace
Mesa Electronics
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