> Date: Mon, 27 May 2013 11:17:24 -0500
> From: el...@pico-systems.com
> To: emc-developers@lists.sourceforge.net
> Subject: Re: [Emc-developers] axis.N.home-state
>
> John Thornton wrote:
> > One more rambling thought could you move both motors together through
> > the whole search, back off, slow seek move and record the offset counts
> > between the two and at the end of the homing move square the gantry by
> > moving each motor 1/2 the distance toward the other and zero the
> > encoders at that point then move to home position?
> >
> if you home to index on both encoders, then the encoder counter hardware
> is zeroed when the index pulse occurs. That makes it hard to maintain
> sync between the encoders, as the current implementation of the drivers
> (software, Pico System and I believe Mesa, too) destroy the information
> of how much the count changed by when the zeroing happened.
> I think it may be pretty simple if you home to the switches only.
>
> Jon
>
But the offset would be shown from the difference between the encoder counts.
-started homing with both joints
-when one joint hits switch and index, it zeros the count, but keeps moving
both joints
-when the next joint hits zero and index, stop both joints
-now the the difference between the encoder counts can be evaluated and adjusted
as per a setting in the INI file
eg if one encoder is 0 and the other is 100 after homing but the INI file says
it should be
55 move till it's 55
if we add this offset as a HAL pin you can observe it and also cause an Estop
if it becomes
too great.
As far as I can see, you can't make any corrections until both the homing marks
are found,
without making assumptions.
Chris M
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