Robust Online Perturbation Estimation using Second- order Sliding Mode Theory for an Earth-Orbiting Spacecraft

Several methods for perturbation estimation can be found in the literatures. The dynamic Inversion technique is a well-known technique to estimate perturbation in the noisy environment. The main idea in the dynamic inversion techniques is replacing the measurement output by state variables in the dynamic equation. The problem with implementing the dynamic inversion method is that it might be difficult to construct the derivative output from noisy measurement. In this paper, a second order sliding mode differentiator and super twisting algorithm is applied for obtaining the derivative of noisy measurement signal. For this purpose, after the measurement noise has been approaches to sliding surface, the measurement output has been decoupled from noisy environment and it is possible to extract derivatives of measurement signal in a noise-free environment. The proposed method is evaluated to estimate the space perturbation in the presence of measurement noise. The advantages of the proposed method in comparison with other methods are illustrated through simulations.