Performance comparison of adaptive and ESO-based backstepping controllers for disturbance rejection in spacecraft

This paper compares spacecraft attitude control in the presence of disturbance torque using an adaptive backstepping controller and an extended state observer-based backstepping controller. Firstly, the adaptive backstepping controller is designed, in which the unknown parameters in a specific disturbance model are estimated using an adaptive law so that the closed-loop system is stable. Afterward, the backstepping control based on the extended state observer is designed. In this approach, the standard backstepping controller is initially designed, and then disturbances with a completely unknown model are estimated by the extended state observer, and the disturbance is rejected by applying the feed-forward law. The simulation results for two different disturbance models show that the backstepping controller based on the extended state observer demonstrates very good results compared to the adaptive backstepping controller when no disturbance information is available. This is for the reason that the extended state observer estimates the uncertainties more accurately.