JeffK, SheilaD, HugoP
We currently have 2 sets of optimized BSC-ISI blend filters that we are trying to choose from: TCrappy and TBetter.
We produced the plots for these filters as installed on ETMX* in order to asses their strengths and weaknesses. Plots are attached:
TBetter filters feature more inertial sensor signal in the blend, at low frequency, on the rotational degrees of freedom.
TBetter blends allows getting more performance ~0.5Hz, and the trade off is more low frequency motion amplification (see upcoming plots from Sheila).
*: TBetter was loaded into TCrappy, and it was unclear which filters loaded in TBetter due to file shadowing in the folder tree. This was fixed on ETMX, and we now load the TBetter blend filters from the common part of the SEI svn:
/ligo/svncommon/SeiSVN/seismic/BSC-ISI/Common/Complementary_Filters_BSC_ISI/aLIGO/some_modified_bend_crappy_filters_040914.mat
Here are spectra of the OpLevs for ETMX. For all of these plots there is no sensor correction.
THe first plot is saved as sheila.dwyer/ALS/HIFOX/ISIs/ETMX_APril16.xml, this template also has the data for ISI and ground sensors. The references (dashed lines) are with Tcrappy on, the solid lines are Tbetter. As expected, Tbetter is better for pitch at half a Hz, but adds large yaw at low frequencies.
Next I tried Tbetter for every DOF excpet moved Rz to Tcrappy on both stage 1 +2. This gets us the benfit in ptich, without the low frequency yaw penalty. In the second plot the dashed lines are Tcrappy again, the solid lines are Tbetter on all DOFs expcept for RZ. This first plot is saved as sheila.dwyer/ALS/HIFOX/ISIs/ETMX_APril16_TcrappyRZ.xml
