On Fri, 1 Mar 2013, Todd Zuercher wrote:
> Date: Fri, 1 Mar 2013 07:52:22 -0500 (EST)
> From: Todd Zuercher <zuerc...@embarqmail.com>
> Reply-To: "Enhanced Machine Controller (EMC)"
> <emc-users@lists.sourceforge.net>
> To: Klemen Dovrtel <klemen_dovr...@yahoo.com>,
> "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net>
> Subject: Re: [Emc-users] bldc/axis homing
>
> I may be having a similar problem. I am using home to index on a ordinary
> rotary servo machine and the first time I try to home after starting
> Linuxcnc, one axis always seems to set a following a error, If I try to home
> it a second time it will home fine? I am not using bldc, so it might be
> possible that your following error on homing problem could be completely
> unrelated to bldc using index to initialize. What is more odd is that I
> only seem to have a problem with one axis (out of 4) doing it. I think Andy
> might be on the right track with thinking it may have something to do with
> the counts resetting to zero when the index is tripped for the first time.
> But the question still remains, what to do about it?
If you have reasonably late LinuxCNC version, the PID component has an input
for index-enable which works arond the thump on index problem, heres the
manual page info about this pin:
pid.N.index-enable bit in
On the falling edge of index-enable, pid does not update the
internal command derivative estimate. On systems which use the
encoder index pulse, this pin should be connected to the index-
enable signal. When this is not done, and FF1 is nonzero, a
step change in the input command causes a single-cycle spike in
the PID output. On systems which use exactly one of the -deriv
inputs, this affects the D term as well.
Todd Zuercher
mailto:zuerc...@embarqmail.com
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Mesa Electronics
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