Nonlinear Attitude Tracking Control of a Spacecraft with Thrusters Based on Error Quaternions

The multi-axis-coupling attitude control of a spacecraft with thrusters for attitude tracking is investigated. The attitude kinematics and dynamics are both described by error quaternions. The four error quaternion dynamic equations are then transformed into four perturbed double integrators via linear transformations. An on-off controller is designed based on the perturbed double integrators. The controller is determined by parabolic switching functions of the scalar error quaternion and the transformed vector error quaternions and their rates. The shortest possible acquiring path, external disturbance rejection, parameter uncertainty compensation are also taken into account. A non-diagonal jet-torque matrix is allowed, which makes the fixing of thrusters more flexible. The controller including no target acceleration feedback is also suitable for acquisition and tracking of maneuvering targets. Stability of the closed-loop system is analyzed by means of phase plane methods. Simulation examples are included to illustrate the effectiveness of the control scheme.