Douglas J. Bender - Redondo Beach CA James D. Brehove - Corona CA
Hughes Aircraft Company - Los Angeles CA
Method and apparatus for controlling the two-axis rate and position as well as the linear elevation of a momentum wheel platform supported by three jackscrews driven by stepper motors. By tilting the momentum wheel, a control torque is produced in the plane orthogonal to the nominal wheel spin axis. When all three actuators are operational, the control transformations are made unique by constraining the sum of the actuator extensions to be zero. When one actuator has failed, the above constraint is eliminated and the failed actuator is constrained to its measured value. Momentum wheel platform rotational rate commands generated by the roll/yaw control system are first integrated to give desired gimbal angles, and then transformed into jackscrew extensions. Jackscrew step commands are computed as the difference between these desired extensions and the current positions of the jackscrews. The position of each jackscrew is maintained by accumulating the step commands.