ℋ∞ control of nonlinear systems via output feedback: controller parameterization

The standard state space solutions to the ℋ_∞ control problem for linear time-invariant systems are generalized to nonlinear time-invariant systems. A class of local nonlinear (output feedback) ℋ_∞-controllers are parameterized as nonlinear fractional transformations on contractive, stable nonlinear parameters. As in the linear case, the ℋ_∞ control problem is solved by its reduction to state feedback and output estimation problems, together with a separation argument. Sufficient conditions for ℋ_∞-control problem to be locally solved are also derived with this machinery