State estimation and non vanishing unmatched disturbance reconstruction using modified super twisting algorithm

The super-twisting second-order sliding-mode algorithm is modified for a class of nonlinear systems with non vanishing unmatched disturbance. The proposed method is based on the modified super-twisting algorithm where the states can be estimated exactly in the presence of non vanishing unmatched disturbance. The value of the equivalent output injection is used to reconstruct disturbance directly. The effectiveness of the modified algorithm is shown by simulation.