[Nakano, Nishimoto, Okutomi, Yamada]

Summary:

• MN photosensors of all cryopayloads were somehow decoupled.
• MN_PS_DAMP of L, T, P and Y were all closed in ETMX and ETMY. Gains are also adjusted.

It was known that photosensors have strong and terrible coupling with each DoF, however, we have succeeded to decoupled them and it helps PRFPMI progress.

What we did:

[Decoupling]

• Excited 6 DoFs with band-limited white noise
• Calculate transfer functions and extract values at each DoFs' resonant frequencies.(Choosing resonant frequency is very important.)
• Make matrix and calculate inverse of it. This is decoupling matrix.
• In ETMX, ITMX and ITMY, vertical resonance cannot be seen so we didn't decouple vertical DoF, although we could see V in EMTY and decoupled it.
• In ETMY, IM PSs were also decoupled however only P seems to be succeeded.
• Decoupling was mostly done in PSDECOUPLING MATRIX, however, only ETMY MN stage was done by SENSING MATRIX.
• DECOUPLING MATRIX looks like Scandinavian flag. (see fig.1 to 4).
• Comparison before/after decoupling can be seen in fig.5 to 7.

 [Damping filter]

• MN_PS_DAMP of L, T, P and Y were all closed in ETMX and ETMY.
• Gains are also adjusted. see fig.8 to 11
• In ITMY, we confirmed Yaw loop can be closed. But others not.
• In ITMX, due to some reasons we didn't confirmed yet.

Next step:

• Implement PS damping in L, T, P and Y DoFs