Semi-globally smooth control for VTVL reusable launch vehicle under actuator faults and attitude constraints

Abstract

The present paper deals with the control problem of vertical takeoff vertical landing (VTVL) reusable launch vehicle (RLV) under actuator faults and multi-type attitude constraints (unilateral constraints, symmetric/asymmetric bilateral constraints, or without constraints). A semi-globally smooth control system is proposed based on a novel barrier function (BF) to realize the finite-time convergence of attitude tracking errors into a small neighborhood of the origin. Moreover, the attitude constraints unviolated under multiple disturbances are guaranteed. To further enhance the disturbance rejection ability, a BF-based adaptive disturbance observer (DO) is derived and incorporated into the control system, which is responsible for reconstructing the disturbance in finite time. The proposed control systems are characterized by the following four points. One is to ensure the finite-time convergence of attitude tracking errors and guarantee the non-violation of constraints without requiring any prior information regarding the Lipschitz constant and upper bound of the disturbance. The second is to provide a unified instrument for control problems with the aforementioned multi-type state constraints. The third is the smoothness property contributing to the chattering-free convergence of attitude tracking errors. The high performance and robustness concerning non-Lipschitz disturbance (such as the sudden actuator faults) are the fourth. Ultimately, the effectiveness of the proposed control systems was demonstrated by the numerical simulation results.