SMDO-Based NGPC Control for Uncertain Nonlinear Systems

As the velocity of near-space vehicle (NSV) is hypersonic, the system should be influenced by strong disturbance and uncertainty. It is difficult to design the flight control system. Nonlinear Generalized Predictive Control (NGPC) method is investigated based on the mechanism model. However, the control performance of NGPC method based on nominal model will be degraded for uncertain systems. Therefore, concerning about a class of uncertain nonlinear systems, the ideal NGPC law based on uncertain model is raised first in this paper. Then a sliding mode disturbance observer (SMDO) is designed to estimate the compound disturbance which includes internal uncertainty, modeling error, and external disturbance. On the other hand, the outputs of SMDO are integrated with nominal NGPC law to eliminate the hybrid disturbance. Furthermore, the stability of the close-loop system is analyzed using the Lyapunov method. Finally, the developed control strategy is used in a hypersonic NSV attitude control system, and simulation results show good robustness and disturbance attenuation ability of this strategy.