ECR for modification of SUS BS RCG model to allow damping of bounce and roll modes

Document #:

LIGO-E1400078-v2

Document type:

E - Engineering documents

Abstract:

The 17Hz bounce and 25Hz roll modes of the BS suspension cannot be damped using to top stage alone. This is due to the limited actuation coupling from the top stage to the wires between the middle stage and optic. We propose to use the middle stage actuation to damp these modes, which was shown to benefit the stability of the MICH feedback loop (link to elog: https://alog.ligo-la.caltech.edu/aLOG/index.php?callRep=11076 ). This state should only be necessary during locking and can be disabled in science mode.

The change required would be to wire a connection in the front end simulink model from the top stage osems to the middle stage coil actuators.

Files in Document:

• E1400078-v2.pdf (101.9 kB)

Other Files:

• E1400078-v2.docx (18.7 kB)

Topics:

• Suspensions

Authors:

• Nicolas Smith
• Jeffrey Kissel

Keywords:

SUS RCH ECR

Notes and Changes:

approved by Dennis Coyne
see integration issue #723:
https://services.ligo-wa.caltech.edu/integrationissues/show_bug.cgi?id=723

Referenced by:

• LIGO-E1300803: Changes Resulting from the L1 DRMI Testing