SPACE STATION ATTITUDE-CONTROL AND MOMENTUM MANAGEMENT - A NONLINEAR LOOK

Nonlinear design procedures are presented for obtaining attitude and angular momentum control laws for the Space Station. These are based on Lyapunov's second method for stability analysis. In the absence of disturbances, there exist four stable equilibrium points. Only one of these is desired and its stability boundary is estimated from the gravitational dynamic potential. Simulation results are presented for the current Space Station configuration for large initial deviations from the local-vertical-local-horizontal frame. The control laws obtained under the zero disturbance assumption are tested in the presence of constant disturbance torques. It is shown that the Space Station can be stabilized about a torque-equilibrium attitude and the momentum of the control moment gyroscopes is bounded, provided the disturbance is smaller than the maximum gravity gradient torque that can be produced by the Space Station.