Mismatched disturbance estimation and compensation for seeker system using higher order sliding mode control

This paper develops a higher order sliding mode control approach for system with non vanishing mismatched uncertainties through a nonlinear disturbance observer. A novel, stable sliding surface is designed by augmenting the state vector with the estimated disturbance as an extra state. The super twisting algorithm is applied to obtain a continuous, robust control for this extended state system. Convergence of the states ensures convergence of the mismatched disturbance via higher order sliding mode technique. Efficacy of the scheme is proved by MATLAB simulation on seeker system of a missile. This estimation compensation approach is tried for various kinds of mismatched disturbances.