Asymmetric Barrier Lyapunov Function based Practical Fixed-time Control of Vertical Take-off/ Vertical Landing Reusable Launch Vehicles with Partial State Constraints

In order to stabilize the vertical take-off/ vertical landing reusable launch vehicles in aerodynamic guidance phase against complex disturbances and partial state constraints, an asymmetric logarithm-type barrier function and asymmetric double-exponential-type barrier function are proposed, where the latter is smooth with respect to system states and has a higher application value compared with the logarithm-type one. Based on the barrier functions and practical fixed-time control theory, two practical fixed-time control laws are derived to drive the attitude tracking errors to a small neighborhood of the origin within a fixed time and ensure the attitude constraints unviolated. Simulation results demonstrate the efficiency of the controllers.