Quaternion observer-based sliding mode attitude fault-tolerant control for the Reusable Launch Vehicle during reentry stage

In this paper, the attitude fault tolerant control (FTC) problem for the reusable launch vehicle (RLV) during the reentry stage is addressed, and a novel quaternion observer-based sliding mode attitude FTC scheme is proposed to accommodate the undesirable actuator faults and maintain a good attitude tracking performance. First, the attitude dynamics and kinematics are presented, and control-oriented attitude systems with actuator malfunctions are established based on the unit quaternion, which would avoid the singularity caused by the attitude maneuvering within a wide range in reetry phase. Then, a quaternion observer is proposed to estimate the compound disturbances, including uncertainties and malfunctions information. The norm character of the unit quaternion is retained in the developed observer and the convergence of estimation errors is proved by the coordinate transformation. Employed the estimations, a multivariable integral terminal sliding mode FTC scheme is proposed to guarantee the closed-loop system stability and high-precise attitude tracking even existing aerodynamics uncertainties and actuator faults. Finally, the simulations are developed to validate the effectiveness of the proposed approach.