Spacecraft adaptive attitude control using variable inertia wheels

Variable inertia wheel (VIW) is a new atttiude control actuator for a spacecraft. VIW can provide attitude control torque not only by adjusting the spin rate, but also by changing the inertia of the wheel. This paper investigates the adaptive attitude tracking control of a spacecraft using VIWs. The rotational equation of motion of a spacecraft with VIWs as actuators is established, and a globally asymptotic stable control law for adaptive attitude tracking is designed. The control law can track given attitude trajectory with unknown spacecraft inertia, and estimate the moment of inertia of the system simultaneously. The VIW spin rate is employed as a weight to distribute the control torque between the two torque modes of a VIW, and such distribution scheme enlarges the output torque of inertia mode, as well as reduce the VIW spin rate. The numerical simulation results demonstrate the validity of the system.