Control and real-time experiments for a multi-agent aerial transportation system

This work presents a multi-agent aerial transportation system (MAATS) with various aerial robots carrying a cable suspended load. First, the dynamical model of the coupled system is described using the Newton-Euler formalism, considering a mass connected to the aerial drones by rigid cables. The objective is to control the load's position to perform trajectory tracking using n drones. Hence, a hierarchical controller is designed using Lyapunov-like energy functions, where the resultant desired cable tension is employed as a virtual control input for the load control which in turn is distributed among the agents to obtain a suitable desired pose of each agent that ensures the trajectory tracking of the load. Then, position and attitude control of each drone is carried out using the desired pose. The stability analysis of the closed-loop system is provided, demonstrating the stability of the coupled system. Finally, the performance of the MAATS control strategy is verified in software-in-the-loop simulations, as well as in real-time experiments, considering 2 and 3 drones, and showing good behavior in spite of significant external perturbations acting on the cables, the load or the agents.