Composite Nonlinear Control for Near Space Vehicles with Input Saturation Based on Disturbance Observer

A new control scheme is proposed to achieve satisfactory tracking control performance for the Near Space Vehicle (NSV) subject to input saturation and unknown external disturbances. The basic idea is to incorporate disturbance observer method and composite nonlinear feedback (CNF) control technique to eliminate the integrated effect of input saturation and disturbances and to track the desired trajectory of NSV in the presence of input saturation and unknown disturbances. Based on the output of the designed disturbance observer, a CNF controller is designed to track the desired signals. The stability of the closed-loop system under the developed controller is rigorously proved. Simulation results show that the developed control scheme can achieve satisfactory tracking control performance for the NSV with input saturation and unknown disturbances.