Online trajectory planning for quadrotor UAV with slung load based on differential flatness

Purpose The traditional quadrotor UAV hanging model is used for positioning and anti-swing control, which is a more complex model and does not facilitate the design of subsequent control methods. An online trajectory planning method based on differential flatness is proposed in this paper. Design/methodology/approach Aiming at the characteristics of this system such as underdrive and strong coupling, a quadrotor UAV hanging model of double points link by sling is established by using Lagrangian equation, which greatly decouples and simplifies the model. The differential flatness theory is used to prove that the system is a differential flatness system with load position as the flat output, and then the load trajectory is planned to obtain the open-loop control law. To accomplish the task of anti-swing, the anti-swing trajectory is added, and the stability of the system is verified by using the LaSalle’s invariance principle and Barbalat Lemma. Findings This paper uses the differential flatness of the system to integrate the control laws and to design the online trajectory planning method. Originality/value The proposed method in this paper can quickly suppress the swing angle vibration and realize the accurate positioning of the system, and the online trajectory planning based on differential flatness has excellent stability.