Arnold,
I have not solved it but I think I know the direction to go. After digging
though the mailing list archive I found one thread that addressed homing of a
dual servo gantry. It looks like it will take some work in HAL - I have
included an excerpt of the thread below that sums it up fairly well. Other
than this, the info I have found has been for steppers or solutions that
handled gantry squaring outside of EMC2 by mechanical means or though the servo
drives themselves. I would be surpised if someone has not figured this out
given the number of large format machines running EMC2. I am 6 to 9 months
away from having a gantry to test with but I would be happy to work with you on
this if someone doesn't chime in with a solution. This is something that
should become a native element of homing in EMC2 as it is fundamental to the
operation of a dual drive gantry.
Jeff
Re: [Emc-users] syncing two motors to one axis
From: Jon Elson <el...@pi...> - 2009-04-01 17:28
Len Shelton wrote:
> So let's say you have two drives, two motors, and two home switches on the
> same axis (gantry type machine). The problem with this arrangement is
> synchronization. The control needs to be aware of the two motors and needs
> to home both at the same time. While homing, we need to bring both motors
> towards the home switches together then independently home each motor when
> it reaches the home switch.
>
> How can this be done in EMC2?
>
We've gone over this a dozen times, at least. It would take about 10-15
lines of HAL and several HAL components to perform the logic.
Basically, you make the two motors run at the same rate. As each motor
hits the home switch, it stops. When both have touched home, they move
together again to complete the precision home sequence to the encoder
index pulse. EMC2 already has features in HAL to handle tandem axes
like this, once homing is done. You feed the lettered axis (as in "X")
position to two numbered "joints" as in zero and one. So, the only
detail up in the air is how to do the homing.
Jon
> Message: 9
> Date: Sun, 10 Jan 2010 11:32:40 +0100
> From: Arnoldritercnc <arnoldriter...@gmail.com>
> Subject: Re: [Emc-users] Homing dual drive gantry
> To: "Enhanced Machine Controller (EMC)"
> <emc-users@lists.sourceforge.net>
> Message-ID: <4b49acc8.7050...@gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> I have the same problem. Jeff, have you solved it?
> Any help will be very appreciated
>
> Thanks
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