Nussbaum-type function–based attitude control of spacecraft with actuator saturation

This paper investigates the attitude stabilization problem of spacecraft subject to external disturbances and actuator saturation. A novel attitude control scheme is technically proposed by incorporating the Nussbaum gain technique into backstepping design. The key idea behind this is to introduce a special Nussbaum-type function in order to compensate for the time-varying nonlinear terms arising from input saturation. By exploiting the dynamic surface control technique, the problem of “explosion of terms” inherent in traditional backstepping designs is effectively eliminated and the computational burden is significantly reduced. Additionally, based on the selected Nussbaum-type function, a constructive analysis methodology is presented, which plays an important role in analyzing the stability properties of the closed-loop system. It is then proved that the proposed control scheme can guarantee the boundedness of all closed-loop signals. Furthermore, the unwinding phenomenon is given a simple and effective remedy by resorting to suitable choices of the attitude error variable and the virtual control law. Finally, simulation experiments are carried out to assess the effectiveness and demonstrate the advantages of the proposed control scheme.