[Nakano, Yamada, Okutomi]
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We found the ETMY TM pitch spectrum has two peaks around 7.5 Hz
- Their mode frequencies are 7.5 Hz and 7.62 Hz, respectively.
- 7.5 Hz: 2nd pitch mode of the TM chain - well known
- 7.62 Hz: Unknown
- This peak split got significant when we close the TMP damping loop.
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So I tried to damp the second peak with the band-pass filter strategy.
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Through some excitation experiments, it seemed that the peak is involved with one of roll-DoF modes.
- The model actually predicted that there is a mechancial resonance having a mode frequency of 6.05 Hz, slightly close to 7.62 Hz.
- However, its mode shape looks displacing mainly the RM-chain that made us wonder.
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But the following schemes were not successful.
- TMP -> MNR
- TMP -> IMR
- TMP -> IMP
- MNP -> MNR
- MNP -> MNR+MNP (with comprehensive band-pass filter for both 7.5 Hz and 7.62 Hz peaks)
- MNP -> MNT
- MNP -> IMR
- MNP -> IML
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Through some excitation experiments, it seemed that the peak is involved with one of roll-DoF modes.
- It seems better to identify the mode shape more precisely and decide which DoF of the actuators is used to damp the mode.