Koji pointed out that I was being silly, and rather than actually misaligning the optics (by, say, changing their IFO Align sliders) I was changing the location of the actuation node by changing the coil output gains. Now I see nice signals at the I_OUT of each of the demodulators (so far I've only looked at the YARM).
I've measured and inverted the matrix by taking the nominal values of the demodulator outputs when the optics are all by-hand optimally aligned, then one-by-one misaligning an optic's angle (pitch or yaw), and looking at the demod outputs that result. Repeat with each misalignment DoF for each of the 4 rows of the matrix. Then I set the pit/yaw coupling elements of the matrix to zero. Then invert the matrix, put it in, and see what happens. So far, the yaw DoFs converged to zero, but the pitch ones didn't. I'll play with it more and think some more tomorrow. |