Design of Terminal Sliding Mode Controller for Quadrotor UAV Based on Inner-Outer Loop

This paper investigates the trajectory tracking control problem of quadrotor UAVs subject to model parameter uncertainties and external disturbances. First, based on the time-scale separation principle, the quadrotor UAV control system is decomposed into a slow-varying position subsystem and a fast-varying attitude subsystem. To ensure rapid convergence of system tracking errors, a fast nonsingular sliding mode reaching law is proposed. By integrating terminal sliding mode control theory and adaptive techniques, an adaptive sliding mode robust controller for the outer-loop position system and a terminal sliding mode controller for the inner-loop attitude system are respectively designed. The stability of the proposed control strategy for quadrotor UAVs is proved via Lyapunov function, and the effectiveness of the control scheme is validated through numerical simulations.