Control of elastic spacecraft by nonlinear inversion and singular perturbation

This paper treats the question of large angle rotational manoeuvre and stabilization of an elastic spacecraft (spacecraft-beam-tip body configuration). Based on nonlinear inversion, a control law is derived to decouple the attitude angle and the dominant flexible modes from the remaining elastic modes. The inverse control law decomposes the spacecraft dynamics into a slow and a fast subsystem. The decoupled attitude angle and the dominant elastic modes are the components of the slow state vector and the remaining elastic modes are included in the fast state vector. Based on singular perturbation theory, controllers are designed for each lower-order subsystem. Then a composite state feedback control is obtained by combining the slow and the fast control laws. Simulation results are presented to show that the composite control system accomplishes large rotational manoeuvre and vibration suppression in the closed-loop system