Cooperative Transportation of a Cable-Suspended Load by Multiple Quadrotors

This paper presents the problem of cooperative transportation of cable-suspended load by four quadrotors, considering lifting and carrying it to the desired pose. Quadrotors and the load in the system, are modeled using Newton-Euler approach. The load is modeled assuming it as a point load, which means that the cable goes from the quadrotors CoM (Center of Mass) to the load CoM. There is switching in dynamics when load exerts a force in the drones in comparison when quadrotors are moving free. Under these considerations, the system can be modeled using a hybrid systems approach, bearing in mind that the system is switching the dynamics when quadrotors start to lift the load. Quadrotors make use of geometric control to track the desired trajectory, which is created by implementing way-points in an optimization process. In this sense, a position-based passivity formation control is implemented in order to create a formation capable of reducing efforts. Reducing the effort made by quadrotors when carrying a common load, is also achieved by adding a new term in the control law in charge of keeping drones in a desired formation even when their position is perturbed by the load. Finally, improvements in trajectory tracking and the reduction of position errors are shown through simulation. Copyright (C) 2019. The Authors. Published by Elsevier Ltd. All rights reserved.