Nulling interferometry and adaptive optics control system optimization

We present a study of the LBT nulling interferometer (LBTI) performance considered from the control systems point of view. Focusing first on the fast path length corrector controller within the LBTI, we show that a simple modification of the controller algorithm reduces the modal tracking error by 50% or more depending on the system dynamics. WE show that this translates into a null depth improvement by a factor larger than 5. Next, we consider coupling the LBTI real-time controller to that of the AO to take advantage of the high order information that is available on the LBTI phase sensor and we show that here again, the global performance can be improved, albeit more modestly by 20%-30%.