Experimental Physics and
Industrial Control System

"Steven M. Hartman" <[email protected]> · Tue, 23 Mar 2010 09:30:26 -0400

Korhonen Timo wrote:
The calculations are put into a layer of EPICS records that uses the
hardware layer records as inputs and outputs.

Basically we work(ed) together with the physicists and translate(d) some
of the most used applications into epics

templates; those have then bunches of calcout records for the formulas
and other stuff to distribute/concentrate the values

as needed. One can achieve quite neat results with epics records....

Once this is done, the physics parameters are available for all
applications. For changing the parameters you then need

just a simple screen - medm panel for instance.

Of course, all this can also be done using a server. I think however
that the implementation in the records has paid off.

That is similar to the approach I took. PVs for beam energy (MeV),
quad focusing strength (m^-2), betatron tune shift, orbit
correction (mrad), undulator K/gamma, etc. are the PVs which are
available at the operator interface layer (e.g. medm). The logic
for translating this to engineering units (e.g. power supply Amps)
is all contained in the EPICS database layer. In most cases, it is
not a one-to-one mapping. For instance, the betatron tune shift
knob drives 9 families of quadrupoles involving 16 (if I recall
correctly) power supplies. The wiggler knob drives even more power
supplies with built in feed-forward compensation for orbit shifts
and tune shifts. And the beam energy knob touches nearly every
magnet power supply (with the quadrupoles, for instance,
maintaining the same effective focusing strength for the different
energy beam).
Within the EPICS database, it is basically an ao record for a
high-level parameter, a bunch of calc, calcout and fanout records,
breakpoint records (for non-linear mapping), and then to ao
records to drive the hardware, with event records used for
synchronization.

--
Steven Hartman
[email protected] || 865-466-6473

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System