On Tuesday, I added some spare vertical L4Cs under HAM3 to try doing the 3dl4c feedforward that we've used on HAM1. While the earthquake was ringing down this morning, I tried turning on some feed forward filters I came up with using Gabriele's interactivefitting python tool (SEI log). The feedforward to HEPI works, doesn't seem to affect the HEPI to ISI feedforward. There is some gain peaking at 1-3hz, so I will take a look at touching up the filter in that band, then try again.

First attached image are some trends for the test. Top two traces are the Z L4C and position loop output during the test. The third trace is the gain for the feedforward path, it's on when the gain is -1, off when the gain is 0. Bottom trace are the 1-3hz and 3-10hz log blrms for the ISI Z Gs13s. The HEPI L4Cs and ISI GS13s both see reduced motion when the feedforward is turned on, but the is some increased 1-3hz motion on the ISI.

Second image are some performance measurements, top plot are asds during the on (live traces) and off (refs) measurements. This was done while the 6.5 eq in Canada was still ringing down so the low frequency part of the asds are kind of confusing, but there is clear improvement in both the HEPI BLND L4C and ISI GS13s above 3 hz. Bottom plot are transfer functions from the 3DL4C to HEPI L4C and ISI GS13, these do a better job accounting for the ground motion from the earthquake. Red (3dl4c to HEPI l4c tf) and blue (3dl4c to ISI GS13 tf) are 3dl4c feedforward on, green (3dl4c to HEPI l4c tf) and brown (3dl4c to ISI GS13 tf) are 3dl4c feedforward off. Sensor correction was off at this time, but HEPI to ISI feedforward was on. It seems like the 3dl4c feedforward makes the HEPI and ISI motion worse by a factor of 3 or 4  at 1 to 2hz, but reduces the HEPI motion by factors of 5-10x from 4 to 50hz.  The ISI motion isn't improved as much, maybe because the feedforward to HEPI is affecting the HEPI to ISI feedforward. I might try this on HAM4 or HAM5 next.