Re: How to use the RVEL field of the motor record

[Torsten Bögershausen via Tech-talk <tech-talk at aps.anl.gov>]

Hej again,

to my understanding we use pC_->motorVelocity_
as the setpoint, how fast should the motor move.
Derived from VELO, JVEL and others, using MRES.
The actual measured velocity from the motor is not handled
at all, to my understanding, reading the code.
We could add another asyn paramater to let the driver
(Yes, drivers based on asynMotor are model 3) report that value.
Mark, Kevin, what do you think ?
/Torsten



On 2026-02-12 08:16, Mathis, Stefan via Tech-talk wrote:
> Dear Mark,
>
> That is exactly what I did -> setDoubleParam(pC_->motorVelocity_, 
> actualVelocity);
> However, this doesn't do anything. Torsten Bögershausen from the ESS 
> mentioned in another channel to me that this feature doesn't work for 
> "model 3 drivers" (I have no idea, what a "model 3" driver is, I guess 
> one based on asynMotor?). So this seems buggy.
> Since apparently there aren't any drivers in the wild using this 
> feature, I guess this bug is maybe undetected until now? If you want to 
> check it, you could just add  setDoubleParam(pC_->motorVelocity_, 42.0); 
> to any asynMotor driver and see if the field gets actually populated.
> For reference: We're using asynMotor R7-2-1 at SINQ (PSI).
>
> Best regards
> Stefan
>
> __________________________________________
> Paul Scherrer Institut
> Dr. Stefan Mathis
> WHGA/022
> Forschungsstrasse 111
> 5232 Villigen PSI
> Schweiz
>
> Telefon: +41563102926
> E-Mail: stefan.mathis at psi.ch
>
> ------------------------------------------------------------------------
> *From:* Mark Rivers <rivers at cars.uchicago.edu>
> *Sent:* Wednesday, February 11, 2026 9:18 PM
> *To:* tech-talk at aps.anl.gov <tech-talk at aps.anl.gov>; Mathis, Stefan 
> <stefan.mathis at psi.ch>
> *Subject:* Re: How to use the RVEL field of the motor record
> Hi Mathis,
>
> I have not found any drivers that set the actual velocity.  However, I 
> believe the infrastructure to do so is implemented in 
> asynMotorController.  In you axis poll() method you just need to add 
> this line:
> setDoubleParam(pC_->motorVelocity_, actualVelocity);
>
> Please let me know if there are problems with this.
>
> Mark
>
> ------------------------------------------------------------------------
> *From:* Tech-talk <tech-talk-bounces at aps.anl.gov> on behalf of Mathis, 
> Stefan via Tech-talk <tech-talk at aps.anl.gov>
> *Sent:* Wednesday, February 11, 2026 1:27 AM
> *To:* tech-talk at aps.anl.gov <tech-talk at aps.anl.gov>
> *Subject:* How to use the RVEL field of the motor record
> Dear all,
>
> I have a asynMotor-based driver (controller inherits from 
> asynMotorController and axis inherits from asynMotorAxis). I would like 
> to populate the RVEL field with the actual velocity read from the 
> hardware, but can't get it to work.
>  From looking through the source code of the motor record, it seems that 
> the param-lib entry with the index motorVelocity_  is involved into 
> populating RVEL. However, just writing to this param-lib entry and then 
> running callParamCallbacks() does not seem to be sufficient. Are there 
> any other param-lib entries which influence this?
> Is there any asynMotor-based example where the RVEL field is actually used?
>
> Thank you very much
> Stefan
>
> __________________________________________
> Paul Scherrer Institut
> Dr. Stefan Mathis
> WHGA/022
> Forschungsstrasse 111
> 5232 Villigen PSI
> Schweiz
>
> Telefon: +41563102926
> E-Mail: stefan.mathis at psi.ch