  The Zero Propellant Maneuver (ZPM) maneuvers the space station by large
angle, utilizing the Control Momentum Gyroscopes (CMGs) only. A robust tracking
guidance strategy is proposed to enhance its performance. It is distinguished
from the traditional trajectory tracking guidance in that the reference
trajectory is adjusted on-line, under the inspiration of eliminating the
discrepancy on the total angular momentum of the space station system. The
Lyapunov controller is developed to adjust the attitude trajectory and further
redesigned for a better performance based on an interesting physical
phenomenon, which is taken advantage of by coupling the components of state
vector. The adjusted trajectory is then tracked to reach the target states of
maneuver. Simulations results show that the disturbance effects arising from
initial state errors, parameter uncertainty and modeling errors are attenuated
or even eliminated, which verifies the robustness of the guidance strategy.
