Composite adaptive backstepping controller for variable speed rotating scan optical spacecraft

In this article, a rotating speed varying scanning strategy for multibody rotating scan optical spacecraft connected with active magnetic bearing (AMB) is introduced. This strategy can increase the imaging efficiency of the high-resolution observation mission by speeding up the rotation in the nonimaging phase. Then, to address the lack of time delay margin problem brought by variable rotational speed, a composite adaptive backstepping controller (CABC) which composed of two controllers is derived via the Lyapunov theory to guarantee the stability of the closed-loop system. In the system, two control methods switch for different phases. When the optical payload is working, the rotational speed of optical payload is decreased to achieve the high pointing precision. The high precision adaptive backstepping controller (HPABC) is used in this phase. When the optical payload stops working, the rotational speed is high and the high rotating speed adaptive backstepping controller (HRSABC) is designed to guarantee the stability of the system. Then, to give the time delay margin of two controllers and prove that the time delay margin of HRSABC is higher than the HPABC, the reference value, which represents the system stabilization and time delay margin and angular velocity margin, is derived using the discretization and linearization method. Finally, a series of numerical simulations have been performed and the simulation results indicated the new control method can effectively address the control problem brought by rotating speed varying.