Re: Insertion Devices Control and EPICS

[Dirk Zimoch <dirk.zimoch@psi.ch>]

At SLS, the difference between upstream and downstream encoders (we call 
it "taper") is monitored by a PLC. The PLC shuts down the motors when 
the taper becomes larger than 50um. This happens much too often.

Recently, we wanted to raise the speed of out servomotor comtrolled gaps 
to 1mm/sec. The delay of the 2nd motor became quite noticable. I tried 
to compensate for that with slightly different acceleration times, so 
that the 2nd motor could catch up. Unfortunatly, the delay is not 
completely reproducable. I will try to change PRIO. Maybe that helps.

During the move, the taper stays within a few um, but at the beginning 
and the end of the move, it is much higher (15 um) and sometimes too high.

I'm desperately waiting for an OMS driver that can handle synchonous 
moves. I see one problem if encoder readback is provided to the motor 
record by another EPICS record: two readbacks for one motor record. But 
if readback goes to the OMS via hardware (as it is here) it should be 
possible.

Dirk

--
Dr. Dirk Zimoch
Swiss Light Source
Paul Scherrer Institut
Computing and Controls
phone +41 56 310 5182
fax   +41 56 310 4413