Robust attitude control for hypersonic reentry vehicle via composite fixed-time stable control method

A novel adaptive nonsingular fixed-time converged terminal sliding mode control method is proposed for a standard nonlinear system suffering from uncertainties and disturbance. The obtained results are applied to attitude maneuver controller design for hypersonic reentry vehicles (HRV). First, an adaptive disturbance observer with fixed-time stability is introduced to cope with the total disturbance consisting of uncertainties and disturbance. Considering the singularity issue inherent in classical fixed-time converged terminal sliding mode, an improved nonsingular fixed-time terminal sliding mode(NFxTSM) is designed by implementing the switching function, ensuring faster convergence and singularity-free. The adaptive technique is also incorporated with the controller design to enhance the robustness of the NFxTSM. Then, considering the inherent time-scale separation feature, the composite attitude maneuver controller is further designed for HRV based on the backstepping technique. The outer loop generates the desired angle rate command, and the inner loop is designed to track the outer loop command. Finally, the numerical simulations are established to verify the effectiveness of the proposed controller.