Adaptive fault-tolerant control for a VTVL reusable launch vehicle

This paper mainly focuses on the attitude tracking controller design for a vertical take-off and vertical landing (VTVL) reusable launch vehicle in regardless of uncertain parameters, un-modeled dynamics, external disturbances and actuator faults. Starting from the kinematics and dynamics model of the VTVL, the attitude tracking error model subject to grid fin faults is built. A novel fixed-time extended state observer (FxTESO) is presented to estimate the derivative of the attitude tracking error and the lumped disturbances including grid fin faults and other uncertainties. Subsequently, a novel nonsingular fast terminal sliding mode surface (NFTSMS) is designed using the FxTESO, which has faster convergence performances than the traditional sliding mode surface. Finally, an adaptive fault-tolerant control scheme is proposed by utilizing the FxTESO, the proposed NFTSMS and the nonsingular fast terminal sliding mode control with an adaptive gain. The proposed controller achieves faster convergence speed and shorter reaching time. Both adaptive fault-tolerant controller and NFTSMS are proved by Lyapunov theory. The performances of the proposed control scheme are demonstrated by numerical simulations.