Virgo Logbook

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AdV-SAT (Suspension control upgrade)

ruggi - 11:06 Saturday 19 April 2025 (66595)

WE ACCH1 re-calibrated

Yesterday an attempt to close the inertial damping of WE suspension failed, due to a slow oscillation. It was the typical behaviour occurring when the accelerometers are not well calibrated. I made the noise injection and I found ACCH1 calibration changed by more than a factor of 2. This morning the compensation filter has been updated and the loop has been closed successfully. The reason why this change happened is not clear and it would be worth to investigate on it: it is not the first time that something like that happens during hardware interventions, but I'm not aware of any clear explanation. Anyway the performance of the control should be back to normal after the re-calibration.

Comments to this report:

pinto, ruggi - 12:55 Wednesday 14 May 2025 (66770)

Today we investigated the issue experienced yesterday with the ID of the WE.

We performed a measument in order to recompute the calibration for the accelerometeres. We found out that ACC_H1 was the one miscalibrated, but the correct compensator was the one used before the last update. One possibility is that the accelerometer switches between two states. The reason of this behaviour is not clear. Some investigation is needed.

In the meantime, we reloaded the older compensation filter, and we modified the DSP card adding one switch for the two compensators in order to have the possibility to move between one 'state' and the other.