Fixed-time adaptive smooth control with relaxed performance constraints for a canard rotor/wing UAV subject to aerodynamic interferences and actuator faults

This paper proposes a fixed-time adaptive smooth control strategy with relaxed performance constraints for a canard rotor/wing unmanned aerial vehicle (UAV) to accommodate aerodynamic interferences and actuator faults. Firstly, a dynamic model of the studied canard rotor/wing UAV is established, and a relaxed prescribed performance function is proposed to restrict the tracking errors within a specific range. Secondly, a newly-designed reaching law is used to construct a robust feedback controller, which consists of a pseudo-sliding variable and effectively suppresses undesirable control chattering. Then, a new fixed-time terminal sliding surface with relaxed performance constraints is proposed and incorporated with the robust feedback control term to guarantee fixed-time convergence of tracking errors while ensuring desired tracking performance. To further address the critical challenges caused by aerodynamic interferences and actuator faults during transition mode, an adaptive smooth control strategy is developed, which can adaptively adjust its parameters without requiring explicit knowledge of faults and uncertainties. Finally, a Lyapunov function is designed to prove the stability of the proposed control strategy theoretically. Comparative simulation results validate the superior performance of the proposed method.