Extra-insensitive input shapers for controlling flexible spacecraft

A procedure for designing command profiles for flexible spacecraft is presented. The command profiles are required to move a spacecraft from rest to rest or to accelerate a spacecraft to a constant velocity with very little residual vibration. To model the case where the spacecraft is equipped with on-off reaction jets, the command signals are restricted to positive or negative constant-amplitude pulses. The technique results in command profiles that are significantly more robust to modeling errors than profiles developed with similar procedures that have been previously reported. Commands are generated that are much more fuel efficient than profiles obtained with related methods. A technique for eliminating multiple modes of vibration is presented. The control technique is evaluated with both hardware experiments and a highly realistic computer simulation that is used to plan Space Shuttle flights.