Getting Robustness Against Unstructured Uncertainty: A Tube-Based MPC Approach

This note extends tube-based model predictive control to the control of nonlinear systems with unmodeled dynamics. The problem of obtaining robustness against unstructured uncertainty is converted into the easier problem of achieving robustness against an additional bounded disturbance while satisfying an additional output constraint. The output constraint depends on the maximum l
_∞
gain of the unstructured dynamics.