Attitude Stabilization Using Two Parallel Single-Gimbal Control Moment Gyroscopes

Abstract

This paper investigates the underactuated attitude stabilization problem using two parallel single-gimbal control moment gyroscopes (SGCMGs). Different from most existing underactuated control techniques requiring the zero total angular momentum assumption, only the controllability of the whole control moment gyroscope (CMG)–spacecraft system, which means the total angular momentum of the spacecraft with CMG array within the momentum envelope of the CMG array, is required in this paper. To achieve the underactuated attitude stabilization, a new controller consisting of two parts, that is, a higher level sliding mode control part to stabilize the angular velocity about the underactuated axis in finite time and a tracking control part to track desired angular velocities that are used to stabilize the remaining states, is developed. This proposed novel control logic achieves attitude stabilization when the initial total angular momentum of the CMG-spacecraft is not zero. Simulations show that the attitude of a microsatellite can be stabilized precisely within acceptable time using the proposed control law and steering law when the controllability constraint is satisfied. When the initial total momentum of the spacecraft base and the CMG array exceeds the momentum envelope of the CMG array, simulation results demonstrate that the attitude is controlled to be a periodic oscillation in the vicinity of the equilibrium, at the same angular momentum level determined by the initial condition.