Modeling and Control for UAV with Off-center Slung Load

TL;DR

This paper develops a new modeling and control approach for UAVs with off-center slung loads, addressing the nonlinear coupling caused by suspension point offset, and validates it through simulations and experiments.

Contribution

It introduces a novel model based on the suspension point rather than the UAV's CoM and designs a cascade control strategy to handle the nonlinear dynamics.

Findings

The control system achieves stable swing regulation and attitude tracking.

Simulation and experimental results validate the effectiveness of the proposed approach.

Abstract

Unmanned aerial vehicle (UAV) with slung load system is a classic air transportation system. In practical applications, the suspension point of the slung load does not always align with the center of mass (CoM) of the UAV due to mission requirements or mechanical interference. This offset creates coupling in the system's nonlinear dynamics which leads to a complicated motion control problem. In existing research, modeling of the system are performed about the UAV's CoM. In this work we use the point of suspension instead. Based on the new model, a cascade control strategy is developed. In the middle-loop controller, the acceleration of the suspension point is used to regulate the swing angle of the slung load without the need for considering the coupling between the slung load and the UAV. An inner-loop controller is designed to track the UAV's attitude without the need of simplification on the coupling effects. We prove local exponential stability of the closed-loop using Lyapunov approach. Finally, simulations and experiments are conducted to validate the proposed control system.