Adaptive disturbance-based high-order sliding-mode control for hypersonic-entry vehicles

In this paper, an adaptive, disturbance-based sliding-mode controller for hypersonic-entry vehicles is proposed. The scheme is based on high-order sliding-mode theory, and is coupled to an extended sliding-mode observer, able to reconstruct online the disturbances. The result is a numerically stable control scheme, able to adapt online to reduce the error in the presence of multiple uncertainties. The transformation of a high-order sliding-mode technique into an adaptive law by using the extended sliding-mode observer is, together with the multi-input/multi-output formulation for hypersonic-entry vehicles, the main contribution of this paper. The robustness is verified with respect to perturbations in terms of initial conditions, atmospheric density variations, as well as mass and aerodynamic uncertainties. Results show that the approach is valid, leading to an accurate disturbance reconstruction, to a better transient, and to good tracking performance, improved of about 50% in terms of altitude and range errors with respect to the corresponding standard sliding-mode-control approach.