Attitude Control of a Quadcopter UAV Using Sliding Mode Control with an Improved Extended State Observer

Quadrotor UAVs require robust control methods to handle complex dynamics, model uncertainties, and external disturbances during trajectory tracking. This paper presents a trajectory tracking control method combining Sliding Mode Control with an Improved Extended State Observer (SMC-IESO). The control system uses a hierarchical structure with position and attitude control loops, employing a third-order Extended State Observer to estimate disturbances in real-time. The improved sliding mode control law incorporates observation error compensation to reduce the required sliding mode gain. Lyapunov stability analysis proves the asymptotic convergence of tracking errors. Simulation results demonstrate that SMC-IESO achieves better tracking accuracy and disturbance rejection than conventional sliding mode control, while significantly reducing control signal chattering, making it more suitable for practical quadrotor applications.