Robust tracking control of near space vehicles with input and output saturation

A robust adaptive tracking control scheme is proposed for the attitude model of the near space vehicles (NSVs) with input saturation, output constraint, unknown external disturbances and modeling uncertainties. Firstly, a second-order sliding model disturbance observer is adopted to estimate the compound disturbance including system uncertainties and external disturbances. Then, the constraints of the output are equivalent to that of the tracking errors which are transformed into unconstrained signals by selecting an appropriate transforming function. Moreover,an auxiliary system is designed to solve the input saturation problem, and the robust adaptive controller is developed for the transformed system by using the backstepping technology. Meanwhile, the boundness of the tracking errors and closed-loop system’s internal signals is rigorously proved. Finally, the developed controller is applied to the attitude control of a NSV, and the simulation results are presented to validate the effectiveness of the proposed robust adaptive control scheme.