I have implemented new DHARD P and Y high power controllers. The DHARD Y controller is also designed to have lower noise than the previous lownoise controller. Both of these controllers have more low frequency suppression and are designed using a 300 kW radiation pressure suspension plant. I have attached the modeled open loop gain and close loop suppression for each loop.
These controllers will be turned on in lownoise ASC after the RPC turns off. The DHARD Y gain will be lowered to -25, and then the controller engaged. The DHARD P gain will stay the same. Both new controller filters are located in FM5. They will be turned on in addition to the filters already engaged for the loops.
I have also increased the DSOFT P gain in lownoise ASC to give more stability at 0.5 Hz when we go to higher power.
Everything has been guardianized.
Evan and I made some measurements of both DHARD loops. DHARD P looks fine, but DHARD Y could use an additional boost around 0.5 Hz. Evan made some edits to FM5 to give us back some phase and added a resG filter in FM3. We are also back to operating DHARD Y with a gain of -40. This should maintain the new lower noise level at 20 Hz.