Self-regulation controller design based on disturbance estimation for reusable launch vehicle

A new robust controller scheme integrating sliding mode control and nonlinear dynamic inversion technique for reusable launch vehicle re-entry attitude control is proposed. Sliding mode item was introduced in the nonlinear dynamic inversion controller to enhance its robustness and designed for high performance of the nominal system. For choosing an appropriate magnitude of the sliding mode item, which will ensure the robustness and avoid unnecessary large chattering, a nonlinear estimator, based on nonlinear extended state observer, was built to estimate the disturbance between the nominal system and nonlinear plant. Then the estimation of the disturbance was used to regulate the magnitude of the sliding mode item online. Stability of the whole system is analyzed. Feasibility and validity of the new controller is demonstrated with RLV simulation examples.