Experimental Physics and
Industrial Control System

"Gregory, Ray via Tech-talk" <tech-talk at aps.anl.gov> · Thu, 9 Jun 2022 17:24:33 +0000

Thank you, Kevin! That works fantastically well.

Ray

Ray Gregory
Oak Ridge National Laboratory

-----Original Message-----
From: Kevin Peterson <kmpeters at anl.gov> 
Sent: Thursday, June 09, 2022 11:31 AM
To: Gregory, Ray <gregoryrd at ornl.gov>; tech-talk at aps.anl.gov
Subject: [EXTERNAL] Re: RBV value for Soft Channel motor not always being set properly on IOC startup

Ray,

You can work around the initialization problem by adding a calcout 
record to mirror the underlying motor's RBV:

record(calcout,"$(VM):rbvCalc")
{
     field(DESC,"Mirror RBV")
     field(CALC,"A")
     field(INPA,"$(M1).RBV CP MS")
}

And then using the calcout in the virtual motor's RDBL field:

   field(RDBL, "$(VM):rbvCalc")

Kevin

On 6/9/22 09:13, Gregory, Ray via Tech-talk wrote:
> Hi,
> 
> I am developing a Soft Channel motor to be a virtual motor that controls 
> two other motors. The virtual motor is essentially a copy of one of the 
> underlying motors and applies ‘adjustment’ moves to the other motor it 
> controls in accordance with a pre-specified alignment profile (using a 
> simple linear equation determined by calibration).
> 
> Most of this is working well. However, when the IOC starts, the virtual 
> motor often fails to retrieve its RBV value from the underling motor. 
> I’ve included the soft channel motor record below.
> 
> How do I fix this?
> 
> I am using EPICS base version 3.14.12.6. I am currently developing on my 
> VM with Simulated motors. I’m not sure what differences to expect when I 
> deploy this to an actual instrument.
> 
> So far I haven’t found a simple solution.
> 
> However, I have created horribly complicated solution that seems to 
> work: I created another do-nothing Soft Channel motor and make it part 
> of the virtual motor system, so now the overall virtual motor controls 3 
> motors, one of them being the do-nothing motor. Then, if the RBV value 
> was not set properly at launch time, I move this do-nothing motor. This 
> has the effect of sometimes properly setting the RBV of the main virtual 
> motor. If that doesn’t work, I try it again, and again, up to some 
> maximum number. I call this process ‘kicking’ the RBV.
> 
> It's a kludgy and nasty solution. I would very much appreciate knowing 
> how to fix this in some simple way.
> 
> Thank you,
> 
> Ray Gregory
> 
> Oak Ridge National Laboratory
> 

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System