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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 presence of multiple uncertainties. The transformation of a highorder 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 veried 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 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.

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This paper describes a novel general on-board guidance strategy which can be applied to both the aerodynamically-controlled descent and the powered landing phase of reusable rockets. The proposed guidance method is based on sequential convex optimization applied to a Cartesian representation of the equations of motion. The contributions are an exploitation of convex and non-convex contributions, which are processed separately to maximize the computational efficiency of the approach, the inclusion of highly nonlinear terms represented by aerodynamic accelerations, a complete reformulation of the problem based on the use of Euler angle rates as control means, an improved transcription based on the use of a generalized hp pseudospectral method, and a dedicated formulation of the aerodynamic guidance problem for reusable rockets. The problem is solved for a 40 kN-class reusable rocket. Results show that the proposed technique is a very effective methodology able to satisfy all the constraints acting on the system, and can be potentially employed online to solve the entire descent phase of reusable rockets in real-time.