Wind Disturbance Rejection of a Foldable Quadrotor Using Nonlinear PID-based Sliding Mode Control

The present paper presents the design of a foldable quadrotor that can adapt its morphology in the presence of sudden external disturbances such as wind. It focuses on solving the problem of tracking a specific trajectory of the foldable quadrotor in the presence of external disturbances. Therefore, robust controllers were designed to ensure better tracking under sudden turbulence, such as wind, considering the inertia change due to the rotating arms. An architectural console for foldable quadrotors was introduced under a gust of conservative winds. A dual loop control strategy was used in which the movements in the X and Y axes were managed by a nonlinear PID controller in the outer loop. In addition, a sliding mode controller was added to the inner loop to regulate the attitude and height in the Z direction, where the mechanical model of the aircraft was combined with the conservative wind gust model. When a conservative wind gust hit the foldable quadrotor for a certain period, a slight deviation from the proposed path at the beginning and end of the disturbance existed with an overshoot (7.468×10^(-3)) for the x-axis and (8.069×10^(-2)) for the z-axis at the beginning of the disturbance, while at the end of disturbance on the z-axis appears undershoot in its value (6.725×10^(-2)). Therefore, the quadrotor maintained its stability with an accuracy of 98%.