Adaptive fuzzy time-varying sliding mode control for quadrotor UAV attitude system with prescribed performance

This paper presents an adaptive fuzzy time-varying sliding mode control scheme for quadrotor unmanned aerial vehicle (UAV) attitude system with prescribed performance. A performance function is used and an error transformation is provided to transform the original constrained nonlinear system into an equivalent unconstrained one. Fuzzy systems are used to approximate unknown nonlinear functions of the attitude system. To eliminate the reaching phase which can make the control is robust with respect to external disturbances and parameter uncertainties from the very beginning, a time-varying fast terminal sliding mode surface is designed by the transformed error and a tracking differentiator. Then by using the sliding mode surface, the controller is developed. The proposed scheme guarantees that all the signals in the resulting closed-loop system are bounded and that the tracking errors converge to a small residual set with the prescribed performance bounds in finite time. Simulation results are used to demonstrate the effectiveness of the proposed scheme.