Izumi, Arai,

We modified the TM-IM Servo filters of BS oplev Pitch and Yaw.

In the BS oplev angular control, we send the oplev signal's feedback to TM for high frequency and IM for low frequency. Before now, we used the inverse filters that cancel the mechanical  peak characteristics. So, we modified the filters that can take advantage of them.

We measured the Transfer Functions of BS TMY/TMY, TMP/TMP, TMY/IMY, TMP/IMP, and then we made TM+IM filters that  send feedback signal to IM for low freq and TM to high freq.Crossover frequency is about 0.9Hz for Pitch and 0.2Hz for Yaw.(see the figures below)

The filters we modified are TM_DAMP,  IM_OLDAMP, TM_OPLEV_SERVO (Pitch, Yaw respectively) .the details are below.

figure explanation (from left  1,2, ...)

1, 2)Open loop gain and Transfer function*filter (1:Pitch, 2:Yaw)

The left is Open loop gain(Magnitude and phase) and the right is Transfer function*filter. Transfer functions*filter are measured Transfer function * fliter(TM: TM_DAMP, IM: IM_OLDAMP filter) and the red is the TM+IM. The left Open loop gain is TM+IM filter(the right red one) * TM_OPLEV_SERVO filter. The green line is gain of the old filter, just reference. UGF is set at 3Hz.

3, 4, 5, 6)The filters we modified

3: IM_OLDAMP_P,  4:TM_OPLEV_SERVO_P,  5:IM_OLDAMP_Y,  6:TM_OPLEV_SERVO_Y.  (there is no TM_DAMP_P(Y) filter, returning the same signal)

7, 8)Screenshots of medm(7:Pitch, 8:Yaw)

These are screenshots of filter in medm. Top is VIS_CUST_TYPEB_TM_DAMP, meduim is VIS_CUST_TYPEB_IM_OLDAMP, and bottom is VIS_CUST_TYPEB_IM_TM_SERVO. The name of filters we modified are 'AraServo'.