ROLL YAW CONTROL OF A FLEXIBLE SPACECRAFT USING SKEWED BIAS MOMENTUM WHEELS

Roll/yaw attitude control of a bias momentum stabilized flexible spacecraft is presented. The roll/yaw normal controller with a nonminimum phase control logic is shown to be very insensitive to the structural mode uncertainty. However, if this controller is switched on at the termination of a thruster-controlled stationkeeping maneuver, it cannot provide sufficient nutation damping by itself to guarantee that the initial transients will remain within specifications. Consequently, a roll/yaw transition controller has been designed to meet the pointing requirements during the transtion from the stationkeeping model to the normal mode. The new transition controller design requires consideration of the solar array flexibility because a control logic, designed to stabilize the nutation mode neglecting the solar array flexibility, could destabilize the solar array flexible mode.