Robust synthesis of feedforward compensators

The design of a feedforward compensator for robust ℋ_∞ or ℋ₂ performance under structured uncertainty is considered. For linear time-invariant uncertainty, a convex method based on linear matrix inequalities (LMIs) across the frequency variable is given. For nonlinear or time-varying perturbations and ℋ_∞ performance, the design problem is reduced exactly to a state-space LMI, and extensions to ℋ₂ performance are discussed. An example illustrates the application of these techniques to two-degree-of-freedom control design