Satellite Magnetic Attitude Control in Sun-Safe Mode Using Control Lyapunov Function

The sun-safe mode is employed to restore the satellite to normal operating conditions in the event of a serious attitude control malfunction. In this article, a fully magnetic attitude controller based on control Lyapunov function (CLF) is proposed. This approach allows the satellite to maintain sun-pointing on the target axis while slowly rotating around this axis, thereby ensuring the satellite's stability and providing a reliable energy supply. First, an affine nonlinear system is constructed based on sun vector dynamics and attitude dynamics, and an appropriate magnetic control law is developed using a CLF to solve the stability problem of this system. Then, the magnetic control law is proven to achieve asymptotic stability without restrictive assumptions on the satellite inertia matrix. Compared with state-of-the-art magnetic control methods for sun-safe mode, the proposed method has a wider application scope and better control performance, as demonstrated by the simulation results. Finally, hardware-in-the-loop experimental results substantiate that the proposed method is both applicable and effective.