Komori, Tanaka, Dan, Sugioka

We performed the actuator balancing ITMX and ETMY.

We manually adjusted the balance because the script seemed to be malfunctioning and outputting irrational values. The manual process we used was basically the same as the script’s logic.

We send excitation signal of 12Hz to each coil and estimated coil imbalance. Figure1 shows the spectrum of oplev signal with excitation. Then, TM_COILOUTF gains are set to compensate the imbalance. For example, when we balance the Pitch mode(H1 and H2) based on H1, TM_COILOUTF gain for H2 should be set $\frac{P_1}{P_2}g_{2old}$. Here we suppose original TM_COILOUTF gain for H1, H2 are 1, $g2oldg_{2old}$, and $P_1$, $P_2$ are the peak value of oplev_P with H1, H2 excitation. Figure2 shows the new TM_COILOUTF gains.
After adjusting the balance, I re-measured the spectrum while exciting each coil again and confirmed that the peak values were equal, indicating the balance was acquired.
To be safe, I did a final vibration test in the L-direction. Since there was no response in Pitch or Yaw, I’ve confirmed that the L-direction actuator is well-isolated from those rotational modes.

Each TM_COILOUTF gains changed as below.

ITMX
H1: 0.844 → 0.789
H2: 1 → 1
H3: 0.962→ 0.935
H4: 1 → 1

ETMY
H1: 1 → 1
H2: 0.859 → 0.890
H3: 1 → 1
H4: 0.912 → 0.951