Pointing stability improvement of astronomy satellites by integration of actuators

As pointing requirements of astronomy satellites become more demanding, a c onventional momentum-exchange scheme for attitude-pointing control is somet imes not enough to satisfy stringent stability requirements. This paper pre sents a new attitude control system for improving the attitude-pointing sta bility of astronomy satellites/and earth-observation satellites. In our pro posed control system, an actuator system is composed of wheel-rotor drive m otors and magnetic torquers driven by a newly devised "cooperative drive la w." The pointing stability is improved by torque control of the actuator sy stem so that the total torque acting on the satellite body is minimized wit h the use of disturbance observers and in a way that shortcomings of the ac tuators are compensated for by each other. In the torque control, attitude control and momentum management are both treated consistently. In this pape r, the mathematical formulation of our proposed scheme is presented and the results of numerical simulations are also presented to demonstrate the sta bility improvement.