AAS 99-117

Multiple-Mode Input Shaping for the Attitude Control of a Flexible Spacecraft

A. Tewari, A. Sanyal

Indian Institute of Technology, Kanpur, India


While the previous input shaping techniques for the control of flexible spacecraft have used only one or two flexible modes, the present paper studies pre-shaped input sequences with many flexible modes. The relevance of high-frequency modes in input shaping, and robustness of the command profile with respect to neglected flexible modes are examined. While only a few modes are adequate for controlling a simple system without resonant modes exemplified here by a train of spring connected masses, the same cannot be said of a flexible structure with several resonant modes, such as a rotating spacecraft. For the spacecraft with a rotating hub and flexible appendages, a hub fixed coordinate system is used, permitting large angle hub rotations with a linear model. Simulation results show that for a maneuver involving larger slew angles, it is necessary to include an increasing number of flexible modes in input shaping. The simulated transverse vibration of the appendages is seen to be within acceptable limits, justifying the linear model.