Sun-Pointing Attitude Control Scheme for Magnetic-based Satellite

For some low-orbit satellites, SADA (solar array drive assembly) is not necessary but steady sun-pointing is required. Magnetic-based attitude control schemes are adopted by more and more low-cost low-orbit satellites and magnetic-based sunpointing attitude control schemes have been proposed for various satellites. For magnetic Attitude Determination and Control System (ADCS), magnetometer and magnetic torquer are the core ADCS components while sun sensor and gyro, which would be employed to determine or estimate sun vector, are important ones. Due to the underactuated characteristics, magnetic attitude control torque could not stabilize the full attitude but the two components of the attitude, simultaneously, which means that magnetic attitude control effort could orientate the solar panels to the Sun. A Lyapunov function, combining the rotational energy and sun angle, is formulated and a PD-type sun-pointing attitude control scheme is proposed to meet the requirements corresponding to sun-pointing task. Further, the effectiveness of the PD-type sun angle-based magnetic attitude control scheme, composed of proportional term, damping term and spinning term, has been verified by use of Lyapunov direct method. Simulations show that, the proposed PD-type attitude control scheme is a suitable sun-pointing scheme for magnetic satellites.

Rotation of TNS Series Spacecraft along the Velocity Vector under the Rotor Control and Magnetic Attitude Control System

A satellite that rotates around the axis of symmetry is considered. A rotor is installed to compensate the angular momentum of the rotating body. Magnetic attitude control system is utilized to provide the stabilization of the rotation axis along the velocity vector on the circular orbit. Control algorithms are proposed that ensure the equilibrium position for the required attitude and its asymptotic stability in the semi-fixed reference frame. Control implementation issues are discussed, including the inherent problems of the magnetic control and the transition to the satellite-fixed reference frame. Numerical simulation is performed for the TNS satellite, which is very far from axisymmetrical. Fast rotation of the satellite around the velocity vector is proved to be achievable with the magnetic control despite the different disturbance sources.