Nonlinear robust control for reusable launch vehicles in reentry phase based on time-varying high order sliding mode

This paper describes the design of nonlinear robust controller for reusable launch vehicles which is nonlinear, multivariable, strong coupling, and includes uncertain parameters. Firstly, the feasible guidance strategy is proposed to obtain the desired guidance commands. Then, the time-varying sliding mode manifold is designed through calculating a series of algebraic equations with fixed final states to make the system trajectories start on the manifold at the initial time. The global robustness is ensured via designing high order sliding mode attitude controller which forces the system trajectory to stay on the sliding mode manifold despite the model parameter uncertainties and external disturbances. Furthermore, in order to reduce control saltation, the virtual control is introduced into the control strategy. Finally, the six degree of freedom flight simulation results are provided to demonstrate the effectiveness of the integrated guidance and control strategy in tracking the guidance commands as well as achieving safe and stable reentry flight.