Robust nonlinear control of uncertain systems with state and control constraints

Uncertain plants constitute an important class of dynamical systems that have a wide domain of applicability. The research studied in this paper treats an innovative robust design procedure for achieving the desired performance and robustness of linear continuous-time systems in the presence of constraints and uncertainties. This paper describes a new robust control methodology and presents manageable results obtained using the Hamilton-Jacobi-Bellman theory. A new performance index is used and the nonquadratic integrand functions are applied. An advantage of this performance measure is that the constraints are introduced in the design process. The robust bounded controller accomplishes asymptotic stability and provides good dynamic performance even when the parameters of the system are variable. The nonlinear control strategy accommodates the available control efforts. The Hamilton-Jacobi-Bellman theory plays a central role throughout. The purpose of this paper is to continue the development of the dynamic programming method for a class of uncertain systems with constraints. The robust control algorithm is implemented and verified for an uncertain model of the aircraft with bounded controls and the constrained state. The longitudinal flight dynamics of the F-18 fighter is considered. Analytical and modeling results demonstrate that the resulting closed-loop system is robustly stable and the fighter achieves the desired performance despite the constraints and uncertainties.