ATTITUDE-CONTROL AND MOMENTUM MANAGEMENT OF THE SPACE STATION

A design procedure based on Liapunov's second method for stability analysis is presented for obtaining attitude and angular momentum control laws for a nonlinear model of the space station. Continuous dumping of the Control Moment Gyros (CMG) momentum is achieved by extracting work from the gravity gradient torque. Mathematically, this is accomplished by providing momentum feedback in the control law. The design procedure can be applied to both stable and unstable station configurations. Zero CMG momentum in the presence of constant aerodynamic disturbance is achieved by providing feedback of the integral of the momentum. Periodic aerodynamic disturbance about the pitch axis is rejected using disturbance rejection filters for each discrete disturbance frequency. It is shown that due to the limits on the maximum gravity gradient torque that can be produced, the closed loop system is locally stable at the desired equilibrium point. Simulations are presented for the current MB6 space station configuration which is inherently unstable. It is observed that the nonlinear design procedure produces excellent results and the selection of the control gains is quite straight forward.

ATTITUDE-CONTROL AND MOMENTUM MANAGEMENT OF THE SPACE STATION Academic Article