J. Kissel, K. Izumi

Kiwamu and I sat down again this morning to review the suspected sign error in the L3 / TST / ESD path in the calibrated output (see LHO aLOG 29860). He's convinced me -- just like what had happened in July (LHO aLOG 28396) -- after the most recent flip of the ETMY L3 ESD bias sign (LHO aLOG 29397), although I had accounted for all of the digital changes in the L3 path, I did not change the replica of the actual to reflect the real actuation strength sign flip. 

Several decisions have been made so as to prevent this problem in the future:
(1) We've decided against changing anything in the CAL-CS front-end calibration for future ESD bias sign flips.
In the real ETMY L3 path, when the ESD bias sign is flipped, it changes the sign of the real-world ESD actuation. As such we compensate that change by changing the sign of the gain in the L3_DRIVEALIGN_L filter bank. In doing so, that means there's no change in the overall LSC super-actuator transfer function. Because there is no change in the overall transfer function, we therefore do not need to change the replica of the path in CAL-CS.

In the past, we've changed the CAL-CS replica to save our sanity aesthetically -- such that, for example, we can look at the DRIVEALIGN matrix gain in both the actual ETMY SUS and in CAL-CS and they match. But if one does so, one MUST change the sign of the real ESD (H1:CAL-CS_DARM_ANALOG_ETMY_L3_GAIN). This is what was not done in July, nor was it done in late August, because there's no digital equivalent in the control system to remind me. 

In light of us (well, me) failing to keep this replica path correct, forgetting to code up a setting change here or there every time, we find the cons of keeping things aesthetically the same out-weighing the pros. 

We will no longer touch the CAL-CS calibration settings when we flip the bias sign in the future.

(2) We've removed all CAL-CS changes from the ISC_LOCK guardian.
While assessment and control system compensation for the bias flip still live in the ISC_LOCK and SUS_PI guardians, we've removed all modification to CAL-CS settings from the ISC_LOCK guardian. We've remove execution of these steps by commenting out the relevant lines in the ISC_LOCK guardian:

        # Check for BIAS flip on ETMY
        # Note that SUS_PI guardian also is affected by ETMX Bias Flipping. 
        #            There are checks and appropriate actions in there too. -Kissel, Hardwick 08/31/2016
        if ezca['SUS-ETMY_L3_LOCK_INBIAS'] < 0:
        #    ezca['SUS-ETMY_L3_ESDOUTF_UL_GAIN'] = +1   # Commented out after finding that compensating for the 
        #    ezca['SUS-ETMY_L3_ESDOUTF_LL_GAIN'] = +1   # Bias flip down stream of the linearization just does
        #    ezca['SUS-ETMY_L3_ESDOUTF_UR_GAIN'] = +1   # not work.
        #    ezca['SUS-ETMY_L3_ESDOUTF_LR_GAIN'] = +1
            ezca['SUS-ETMY_L3_DRIVEALIGN_L2L_GAIN'] = -30.0
            ezca['SUS-ETMY_L3_ESDOUTF_LIN_FORCE_COEFF'] = -124518.4
        #    ezca['CAL-CS_DARM_FE_ETMY_L3_DRIVEALIGN_L2L_GAIN'] = -30.0          # Commented out after second occurrence
        #    ezca['CAL-CS_DARM_FE_ETMY_L3_ESDOUTF_UL_GAIN'] = +1                 # of overall sign error in L3 path of 
        #    ezca['CAL-CS_DARM_FE_ETMY_L3_ESDOUTF_LIN_FORCE_COEFF'] = -124518.4  # CAL-CS. LHO aLOG 29868.
        #    ezca['CAL-CS_DARM_ANALOG_ETMY_L3_GAIN']= -1
        else: # flip everything.
        #    ezca['SUS-ETMY_L3_ESDOUTF_UL_GAIN'] = +1   # Commented out after finding that compensating for the 
        #    ezca['SUS-ETMY_L3_ESDOUTF_LL_GAIN'] = +1   # Bias flip down stream of the linearization just does
        #    ezca['SUS-ETMY_L3_ESDOUTF_UR_GAIN'] = +1   # not work. LHO aLOG 29397.
        #    ezca['SUS-ETMY_L3_ESDOUTF_LR_GAIN'] = +1
            ezca['SUS-ETMY_L3_DRIVEALIGN_L2L_GAIN'] = +30.0
            ezca['SUS-ETMY_L3_ESDOUTF_LIN_FORCE_COEFF'] = +124518.4   
        #    ezca['CAL-CS_DARM_FE_ETMY_L3_DRIVEALIGN_L2L_GAIN'] = +30.0          # Commented out after second occurrence
        #    ezca['CAL-CS_DARM_FE_ETMY_L3_ESDOUTF_UL_GAIN'] = +1                 # of overall sign error in L3 path of 
        #    ezca['CAL-CS_DARM_FE_ETMY_L3_ESDOUTF_LIN_FORCE_COEFF'] = +124518.4  # CAL-CS. LHO aLOG 29868.
        #    ezca['CAL-CS_DARM_ANALOG_ETMY_L3_GAIN']= +1
        ezca['SUS-ETMY_L3_LOCK_BIAS_GAIN'] = 1


Attached is a screen shot of the relevant MEDM screens to aide discussion.