Composite disturbance attenuation based saturated control for maintenance of low Earth orbit (LEO) formations

Maintenance of high performance formation control is important for low Earth orbit (LEO) formation missions of small spacecraft. In this paper, a model of nonlinear relative motion dynamics is built, and then nonlinear and important perturbations affecting the formation configuration, such as J ₂ and atmospheric drag, are analyzed as disturbances. Global navigation satellite system based relative positioning with nonlinear filtering is adopted to provide state information associated with the perturbations. By combining disturbance observer based control with H∞ state feedback, a composite disturbance attenuation controller is proposed for maintenance of continuous and accurate formation. With consideration of precise control relying on micro thrusters, a composite disturbance attenuation based saturated controller is designed and its stability is proved. Finally, through numerical simulations, we demonstrate that control accuracy is improved after effectively avoiding perturbations and that stabilization can be satisfied using this method.