Underactuated Steering Control Law for Spacecraft Attitude Maneuver using Two Skewed Control Moment Gyroscopes under Path Constraint

Several methods have been proposed for three-axis attitude control using two control moment gyroscopes (CMGs) under the condition that the total angular momentum of the system is zero. Star sensors that recognize small stars are commonly used to precisely determine spacecraft attitudes. Because star sensors are highly sensitive, their boresight must not align with the Sun. However, previously reported underactuated steering laws are feedforward type controllers and cannot satisfy the attitude-path constraint for star sensors in real time. This paper proposes a novel underactuated steering algorithm for two skewed single-gimbal CMGs (SGCMGs) that addresses the limitations of previous steering laws by incorporating a barrier function to prevent the star sensor’s boresight from entering prohibited directions. The innovation of the proposed steering algorithm is that it can stabilize not only the spacecraft attitude towards the target attitude but also prevent the star sensor boresight from entering the prohibited area during maneuvers using only two skewed SGCMGs. The validity of the proposed algorithm is demonstrated through numerical simulations.