Design of Robust Input-Constrained Feedback Controllers for Nonlinear Systems

This work contributes to the optimal design of closed-loop nonlinear systems with input saturation in the presence of unknown uncertainty. Stability conditions based on contractive constraints were developed for a general class of nonlinear systems under some Lipschitz assumptions. Closed-loop robust stability and robustly optimal performance can be guaranteed in the presence of input bounds, if the solution of the design problem, formulated as a nonlinear semi-infinite program (SIP) with differential equation constraints, can be guaranteed to be feasible. In this work, the SIP is solved by means of a local reduction approach, which requires a local representation of the so-called lower level problems associated with the SIP.