Anti-saturation adaptive fault-tolerant control with fixed-time prescribed performance for UAV under AOA asymmetric constraint

Abstract

This paper presents an anti-saturation adaptive fault-tolerant control scheme with fixed-time prescribed performance for the longitudinal model of fixed wing UAV under actuator faults, control input saturation, angle of attack (AOA) asymmetric constraint and uncertainties. First, by introducing equivalent error transformation technique, the error transformed models of the altitude and airspeed tracking subsystems are strictly constructed. Second, asymmetric saturation function, auxiliary system and barrier Lyapunov function (BLF) are incorporated to guarantee AOA maintain in the asymmetric constraint. Then, neural network approximation structures are combined with adaptive robust terms to handle the lumped disturbances. Furthermore, Nussbaum-type gain technique is adopted to deal with the unknown time-varying parameter arising from input saturation and actuator faults. According to the stability analysis, the altitude and airspeed tracking errors evolve strictly inside the fixed-time performance envelops, while the AOA remains in asymmetric constraint and all signals in closed-loop system are uniformly ultimately bounded. Finally, numerical simulation is presented to verify the effectiveness and superiority of proposed control scheme.