PRECISION AUTONOMOUS SATELLITE ATTITUDE-CONTROL USING MOMENTUM-TRANSFER AND MAGNETIC TORQUING
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An attitude control system utilizing as control elements three orthogonal reaction wheels and three orthogonal on/off electromagnets is studied for an earth-looking satellite in polar orbit. The nonlinear feedback law for attitude control cancels out all gyroscopic coupling effects and also allows independent restoring and damping control torques about each axis. Momentum dumping is accomplished by bang-bang switching of the three magnets. Simulation results indicate that this system provides excellent attitude stability and momentum control in the presence of typical disturbance torques. A comparison of the proposed attitude and momentum control laws with other closed-loop laws is also included.