Experimental Physics and
Industrial Control System

Tim Mooney <[email protected]> · Mon, 27 May 2013 22:46:57 -0500 (CDT)

Hi Emma,

I agree.  The original purpose of RDBD was specifically about retries,
and not also about whether or not to make an initial move.  I would
like to explore the consequences of going back to that purpose.

Tim

----- Original Message -----
> From: "Emma Shepherd" <[email protected]>
> To: [email protected]
> Sent: Monday, May 27, 2013 5:57:25 PM
> Subject: Motor record .RDBD field
> 
> Hi all,
> 
> I've stumbled into this issue a couple of times now so I thought it
> was worth a message to tech-talk.
> 
> The .RDBD field of the motor record limits the smallest allowed move
> - quite often we want to set this very low so that we can do small
> step moves.  However, in a few cases we also want to use the motor
> record's retry mechanism by setting .UEIP to 'Yes' and feeding the
> encoder into .REP (I'm using the tpmac driver which allows you to do
> this when the encoder is on a different channel).  Because .RDBD is
> now used as the retry deadband, we need to make it larger since it
> is not capable of attaining such an accurate position.
> 
> It would be better if we could somehow decouple the use of .RDBD in
> the retry sense from the smallest allowed move.  Have other people
> run into this and found a solution?  In the meantime I need to keep
> switching between modes (toggling .UEIP and changing .RDBD
> appropriately) to allow me to do scans in very small steps followed
> by a wind-back which uses retries to ensure I'm not losing steps.
>  It's a bit messy and not ideal.
> 
> Of course if we had perfect mechanics we wouldn't need to be doing
> retries at all, but c'est la vie!
> 
> Thanks,
> Emma
> 
> P.S. I hope I haven't missed a thread on this already, the APS
> website seems to be down at the moment so I can't check
> 
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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System