Disturbance observer-based nonsingular fixed-time sliding mode tracking control for a quadcopter

This paper proposes a fixed-time method for the tracking control of a quadcopter subject to external disturbances. Compared with finite-time tracking control, the proposed control strategy ensures that the upper bound of the convergence time is independent of the initial state of the system. To determine the external disturbances, we have designed a fixed-time disturbance observer (FTDO). This allows the external disturbances to be compensated precisely, as a result of which the robustness of the control algorithm is enhanced, and the chattering problem is alleviated. We also propose a novel nonsingular fixed-time sliding mode control (FTSMC) technique to provide fixed-time position and attitude tracking control for the quadcopter, which enables a more accurate determination of the convergence time. We validated the fixed-time convergence of the proposed quadcopter tracking control method using Lyapunov stability theory. Finally, we verified the theoretical results not only by simulations but also by experiments.