ACTIVE VIBRATION SUPPRESSION AND MANEUVER CONTROL OF AN ORBITING SMART FLEXIBLE SATELLITE

In this paper, vibration suppression and control of a smart flexible satellite maneuvering in a circular orbit are studied. The satellite is considered as a rigid hub and two flexible appendages with PZT (lead zirconate titanate) layers attached on them as sensors and actuators. Flexible satellite governing equations of motion are obtained using Lagrange-Rayleigh-Ritz technique and assumed mode method; these dynamic equations of motion of the flexible satellite are nonlinear and coupled. A thorough look at the resulting equations reveals that the flexible satellite dynamics that include the appendage vibrations and its rigid maneuver occur in two different time scales. Therefore, the dynamics of the flexible satellite can be divided into two fast and slow subsystems using the singular perturbation theory. The slow and fast subsystems are associated with rigid maneuver and appendages vibrations, respectively. A hybrid controller is proposed which consists of an adaptive inverse dynamics for slow subsystem maneuvering control, and a Lyapunov based controller for vibration suppression of the fast subsystem. Use of adaptive controller allows us to cope with parameters uncertainty for the rigid motion of the system. Using the Lyapunov approach the stability of these hybrid controllers is studied. Finally, the whole system is simulated and the simulation results show the effective performance of the proposed hybrid controller.