Re: pmacAsynCoord in-position vs .MOVN

["Knap, Giles \(DLSLtd,RAL,LSCI\) via Tech-talk" <tech-talk at aps.anl.gov>]

Hi Dean, Lewis,

First re EPICS support modules. https://github.com/dls-controls/pmac is the one that DLS currently supports and includes all the functionality from tpmac, plus supports the power pmac and trajectory scanning, among other things.

Regarding your MOVN issue:

The driver looks at a few axis flags to determine if it reports the axis is moving:

• In Position Bit == 1 (bit 1 of status word 2) OR
• Motor On Bit == 0 (bit 23 of status word 2) OR
• Amplifier Enabled == 0  (bit 19 of status word 1) 

You can see the value of these status bits directly with the terminal command (for axis 1)

 #1?

The LSB of the number printed is In Position Bit, if this is set to 0 when you see your issue then its due to the configuration of that axis.

The pmac sets in position for an axis under the following circumstances

1. The motor must be in closed-loop control;

2. The desired velocity must be zero;

3. The magnitude of the following error must be less than In-position deadband Ixx28;

4. The move timer must not be active;

5. The above four conditions must all be true for (Ixx88+1) consecutive scans.

I have seen a situation where the tuning of the motor is such that it may stop outside of the in-position deadband so this would be something to look for.

I hope this helps,

giles.

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From: Tech-talk <tech-talk-bounces at aps.anl.gov> on behalf of J. Lewis Muir via Tech-talk <tech-talk at aps.anl.gov>
Sent: 16 February 2021 21:10
To: Hidas, Dean <dhidas at bnl.gov>
Cc: tech-talk at aps.anl.gov <tech-talk at aps.anl.gov>
Subject: Re: pmacAsynCoord in-position vs .MOVN

 

On 02/16, Hidas, Dean via Tech-talk wrote:
> I'm using pmacAsynCoord with a pmac turbo2 brick controller.  What I notice is that occasionally the pmac reports that a move is finished, that the coordinate system is not motion, but the .MOVN field of the motor record stays high despite reaching the desired position and not actually being in motion.  At this point the pmac reports in position, but the motor record does not seem to have any additional control effect (nor should it I believe), ie the .MOVN field stays high but there is no further motion.  Are there any motor record fields or other parameters you might advise having a look at that could have an effect on this?

Hi, Dean!

Haven't seen that before.  I initially thought it might be an issue I
reported a while ago

  https://github.com/epics-modules/tpmac/pull/4

but after reading your description of the problem more carefully, I
don't think it's the same thing.

Where did you get pmacAsynCoord?  There seems to be at least three PMAC
drivers floating around that I know of:

1. https://www.gmca.aps.anl.gov/TPMAC2/
2. https://github.com/epics-modules/tpmac
3. https://github.com/dls-controls/pmac

#1 is the original, #2 seems to be a friendly fork of #1, and #3 is a
driver for which I don't know its lineage.

Also, what version of the driver are you using?

Regards,

Lewis

 

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