Quasi-continuous high-order sliding mode controller design for reusable launch vehicles in reentry phase

A nonlinear robust control strategy is developed for Six-Degree-of-Freedom (6DOF) Reusable Launch Vehicles (RLV) which is nonlinear, multivariable, strong coupling, and includes uncertain parameters and external disturbances. Firstly, a reentry guidance law is designed to generate feasible guidance commands which are then tracked by second-order sliding mode attitude controller designed based on quasi-continuous high-order sliding mode theory. Furthermore, in order to reduce control chattering, the virtual control is introduced into the design of third-order sliding mode attitude controller which achieves higher tracking accuracy and less control chattering. Finally, 6DOF integrated guidance and control simulation results for X-33 vehicle are presented to demonstrate the effectiveness of the proposed control strategy in tracking the guidance commands as well as achieving safe and stable reentry flight.