Appointed time control for flexible satellite with active vibration suppression

This work addresses the problem of achieving precise appointed time attitude control and rapid active vibration suppression in flexible satellites. Firstly, an appointed time piecewise sliding mode controller is developed to ensure the convergence of attitude error to the vicinity of the origin at the appointed time. The convergence time can be predetermined using a parameter. Secondly, a modal observer is introduced to estimate the vibrations in the flexible elastic modal, and a predefined-time active vibration suppression controller is designed to mitigate the elastic vibrations in flexible solar panels. The stability of both controllers is proven using the Lyapunov theory. Finally, simulations are conducted to validate the proposed control strategy. Through comparison with two predefined time controllers, it is evident that the proposed controller achieves more precise convergence time, smoother attitude variations, and minimal magnitude of control inputs.