Two-Step Input Excitation Disturbance Estimation-Based Self-Adjustment Control for Spacecrafts With Multiplicative Uncertainties

Multiplicative uncertainties, including inertia variation and actuator effectiveness loss, degrade the attitude control performances of spacecrafts significantly, which poses high requirements for the accurate identification of uncertainties. In this article, a two-step input excitation disturbance estimation-based self-adjustment attitude control method is proposed for spacecrafts, where the whole process is divided into a two-step input excitation phase and an attitude control phase. In the first step of input excitation phase, an input excitation sliding mode disturbance observer is designed to identify the actuator effectiveness, where the influence of inertia variation can be eliminated by the designed input excitation signal. In the second step of input excitation phase, by using the identified actuator effectiveness, an input excitation refined disturbance observer is designed to obtain the values of inertia variation. Next, in the attitude control phase, by incorporating the identification results, a self-adjustment attitude control law is designed to achieve the attitude tracking, where a modified attitude dynamic model is established and thereby the model uncertainties can be reduced significantly. Finally, numerical simulation and experiment verification are carried out to show the effectiveness of the proposed method.