Collaborative Control for Aerial Transportation of Cargo With Dual Quadrotors

With excellent maneuver performance and flexibility, quadrotor unmanned aerial vehicles (UAVs) are widely used in aerial transportation. However, the aerial transportation system with dual quadrotors exhibits high degrees of freedom, strong nonlinearities, and complex state couplings, which makes it more difficult to realize simultaneous quadrotor positioning and cargo swing suppression. Compared with the traditional description of cargo swing dynamics with four angles in the previous work, the spatial swing angle is introduced in a more intuitive way to reflect the swing dynamics of the cargo. On this basis, the dynamic model of the system is established according to Lagrange's equations. Then, a nonlinear adaptive controller is proposed, in which a dynamic compensation term is introduced to compensate for the lateral forces along the cables, and a spatial swing angle-related term is designed to enhance cargo swing damping. Meanwhile, considering the influence of unknown air resistance on quadrotors and cargo during transportation, an adaptive term is applied. Subsequently, Lyapunov techniques and LaSalle's invariance principle are used to prove the stability of the closed-loop system. Finally, based on the self-built general experimental platform, both indoor and outdoor experiments have been carried out to validate the practicability and effectiveness of the proposed method.