Application of improved appointed time control in helicopter mode of a tilt-rotor eVTOL aircraft

In this paper, an appointed time sliding mode control scheme is proposed for trajectory tracking control of a tilt-rotor electric vertical takeoff and landing (eVTOL) aircraft. First, the error dynamic model of helicopter mode of the tilt-rotor eVTOL aircraft is presented. Second, an appointed time prescribed performance function (ATPPF) is designed as the expected value of the error, which guides the error to converge to zero at the appointed time. Then, a predefined time controller ensures that the actual error tracks the expected error before the settling time set by the ATPPF. By setting the time parameters of the ATPPF and the predefined time controller to the same value, the actual error will converge to zero vicinity at the appointed time. Finally, the predefined time convergence of the closed-loop system is proved via Lyapunov analysis. The effectiveness of the appointed time control strategy is demonstrated in the simulation results in the presence of external disturbances, dynamic uncertainties and control input constraints.