daniel.sigg@LIGO.ORG - posted 12:41, Tuesday 15 October 2024 - last comment - 08:42, Wednesday 16 October 2024(80685)
Strain gauge servo
(Dave, Vicky, Daniel)
The necessary filter modules for the ZM2/4/5 strain gauge servos were booted into the h1tcscs model, and the medm updated. We added some channels to the copy guardian, since the strain gauge channels are acquired in the TwinCAT system. The new filter modules were loaded with a -1/f filter and then engaged with a gain of 1. The output limiter were set to 50V.
We played around with the new servos by stepping the target strain gauge settings. The response time seems to be about 7-8 sec. All working fine.
So when running the PSAMS servo, to change PSAMS ROC, set H1:AWC-ZM{2,4,5}_M2_STRAIN_VOLTAGE_TARGET instead of adjusting the applied voltage offset slider H1:AWC-ZM{2,4,5}_M2_SAMS_OFFSET.
Attaching some trends of the PSAMS servo working overnight -
Screenshot 1 - For ZM4, servo filter bank settings and ndscope trends of a step in the servo setpoint. The PSAMS servo output adjusts the applied voltage (see PZT DC voltage readback, eg H1:AWC-ZM4_PSAMS_VOLTAGE_DC) to bring the strain gauge voltage readback (H1:AWC-ZM4_PSAMS_STRAIN_VOLTAGE) to the target setpoint voltage (H1:AWC-ZM4_M2_STRAIN_VOLTAGE_TARGET).
Screenshot 2 - ZM2,4,5 PSAMS strain gauge voltage trends before/after servo. Before PSAMS servo (last few days) - the applied PSAMS PZT voltage is static, and the PSAMS strain gauge voltage readbacks drifts (small amount). After turning on PSAMS servos, the applied PSAMS PZT voltages are servo'd to stabilize the strain gauge readbacks to the "TARGET" values.
Screenshot 3 - ZM5 suspension MEDM screen, showing where the PSAMS servo filter bank and target setpoints are. This ZM5 suspension medm screen is in $(userapps)/sus/common/medm/hxds/SUS_CUST_HPDS_OVERVIEW.adl (Sheila helped us svn-commit this screen from LLO, then Daniel pulled it for use at LHO).
Daniel updated the PSAMS servo parts in the AWC block of h1tcscs.mdl, found in userapps/trunk/tcs/h1/models. The SDF's appeared in the h1tcscs table (in the "OAF" box on the sdf screen). Daniel has sdf-monitored the PSAMS filter banks, and left the ZM PSAMS PZT offsets sdf-monitored. Note these pzt offset values are basically meaningless when the servo is running. The ZM2/4/5 offsets are now all SDF'd around 100V, so they would come back to ~nominal values after any resets.
This follows up on Adam's llo73464 "Adding SAMS servo to HPDS common part" (from LLO: WP 11839, IIET ticket 32287, and ECR E2400361) to pull the psams servo for LHO.