Adaptive dynamic surface control of NSVs with input saturation using a disturbance observer

An adaptive dynamic surface control (DSC) scheme is proposed for the multi-input and multi-output (MIMO) attitude motion of near-space vehicles (NSVs) in the presence of external disturbance, system uncertainty and input saturation. The external disturbance and the system uncertainty are efficiently tackled using a Nussbaum disturbance observer (NDO), and the adaptive controller is constructed by combining the dynamic surface control technique to handle the problem of “explosion of complexity” inherent in the conventional backstepping method. For handling the input saturation, an auxiliary system is designed with the same order as that of the studied MIMO attitude system. Using the error between the saturation input and the desired control input as the input of the designed auxiliary system, a series of signals are generated to compensate for the effect of the saturation in the dynamic surface control design. It is proved that the developed control scheme can guarantee that all signals of the closed-loop control system are semi-globally uniformly bounded. Finally, simulation results illustrate that the proposed control scheme can achieve satisfactory tracking performance under the composite effects of the input saturation and the external disturbance.