K.Tanaka, C.Hirose

This report is a continuation of klog#20592

We made filters for feedback control returned to IMMT1 and IMMT2 by POP forward QPDs. Degree of freedom are {IMMT1, IMMT2}_{PIT,YAW}. These filters consist mainly of a first-order low-pass filter, an ellip filter (or notch filter) that suppresses the resonance frequencies of the IMMT1 and IMMT2 suspensions (around 2Hz and 7Hz), and a gain. These are assumed to be around UGF0.1Hz, at which time the phase margin is 70 to 80 deg. (ASC-DOF_PIT_YAW.png)

DOF{3,4}_{PIT,YAW}.png --> These images show the PLANT measurement results(klog#20592) on the right and the open-loop transfer function expected when a filter is added to PLANT on the left.

Of these, IMMT1_PIT and IMMT2_YAW succeeded in closing the feedback control loop. Their open-loop transfer functions are shown below. At this time, we turned off ADS of IMMT2 and PR2.(OLT_IMMT1PIT_IMMT2YAW.png) The remaining degrees of freedom could not be measured due to alignment.