Abstract:

I tested the modal damping of GAS filters on SR3.
The modal damping seems to work wel but yet to be implemented into the guardian.

Detail:

Currently, GAS control of Type-B suspension has a large gain peaking, which is shaking the suspension around several Hz (klog36609).
It might disturb to lock the DRMI stably, I tested the modal damping control of GAS filters by using SR3.

First, I diagonalized the sensor by measuring the response of each LVDT to each resonance.
The data are stored at  /users/VISsvn/TypeB/SR3/Spectrum/2026/0416/.
Procedure is basically same as written in JGW-P1809347-v9 (DC response of actuator is measured by just pushing 5000 cnts from each modal actuator to save the time while it was measured with several tens of mHz transfer function in te document).

Figure 1 and 2 show the decoupled sensor and actuator matrices.
Figure 3 -5 show the suspension plant with modal actuators and sensors, which seems well decoupled.

Then, I designed the control filter and implemented it at FM1 of each modal filter bank.
Figure 6-8 show the measured OLTFs of each modal damping control.

Figure 9 shows the spectrum of IMV OSEM signals with current LOCK_ACQUISITIN state (blue), current OBSERVATION state (pink), and modal damping (brown).
The modal damping has a low noise at high frequency while maintaining the low frequency damping performance.
This control should be implemented into the guardian so that these controls are on at LOCK_ACQUISITION state.