Dynamics and Control of Flexible Satellite using Reaction Sphere Actuators

This paper presents a disturbance observer-based linear quadratic Gaussian (LQG) control strategy to stabilize the flexible spacecraft considering the vibration suppression of flexible appendages using an orthogonal cluster of magnetically suspended reaction sphere actuators. The nonlinear dynamic equation of a flexible satellite is given and then linearized using the Jacobian method to get a linear state-space model. The dynamic equation of the reaction sphere actuators is derived by considering 2 virtual gimbals. A new steering law is designed to produce the tilt angle commands of orthogonal reaction sphere actuators. The proposed disturbance observer-based LQG considers process disturbances and measurement noises, and performs a trade-off search between control efforts and regulation performance. Numerical simulations are performed to evaluate the proposed strategies for an attitude stabilization scenario, and the results illustrate that the disturbances are effectively mitigated.