Robust feedforward control of uncertain systems using dynamic IQCs

We consider the problems of robust H
_infin
and H
₂
disturbance feedforward control for uncertain systems described in the standard LFT form. We use integral quadratic constraints (IQCs) for describing the uncertainty blocks in the system. Due to technical reasons related to the feedforward problem, throughout the paper, we work with the duals of the constraints involved in robustness analysis using IQCs. Our main results stem from a state-space characterization of nominal stability. For the robust H
_infin
problem, we use the L
₂
-gain interpretation and use another signal-based generalization of the H
₂
-norm for LTI systems. We obtain convex solutions to both problems using the stability characterization mentioned above. A numerical example highlights the use both of feedforward control and dynamic IQCs.