Experimental Physics and
Industrial Control System

Pete,

Which version of the motor record is being used?  I've seen unexpected
motion problems with ancient versions of the motor record, but they
involved stopping a motor while it was in SET mode, not restoring
autosaved positions.

A new motor-record field, RSTM, is available in the master branch of the
motor module, which gives users more control over how autosaved
positions are restored:

   https://github.com/epics-modules/motor/pull/160

Kevin

On 1/6/22 15:13, Siddons, David via Tech-talk wrote:
> I would like to suggest an addition to the motor record logic (or
> save-restore, not sure which). I have been bitten several times by
> having a set of motors under save-restore and having a restart provoke a
> runaway. The sequence goes like this:
>
> motor system running fine, save-restore operating.
> IOC is stopped.
> Motors are powered down.
> motors powered up, causing their internal position registers to be set
> to zero.
> IOC re-started, save restore writes previous positions into motor
> driver, causing them to move to that position, and havoc!
>
> My proposed change would cause someone (motor, save-restore) to notice
> that the hardware and software disagree, and ask the User how they want
> to resolve this dilemma. Those of you old enough to remember Spec know
> that this is exactly how Spec behaved on startup. If the User decides
> that the software is right, then the new positions should be entered in
> the SET=1 mode. If she decides that the hardware is right, then that
> value should be entered in the same way. It isn't enough to just take
> the hardware value as right, since it is quite liable to be wrong, as
> described above, although that would prevent runaways.
>
> In my case, the problem was compounded by the fact that the STOP command
> did not work! But that is the subject of another discussion.
>
> Pete.