This paper proposes a centralized control framework for cooperative aerial transportation using multiple Unmanned Aerial Vehicles (UAVs) connected via suspended cables, where the overall UAVs–payload system is treated as a unified dynamic entity. The objective is to transport a rigid object along a predefined trajectory while ensuring stable and coordinated motion. The payload is connected to the UAVs through elastic cables, which introduce coupling effects between the vehicles and the transported object. Due to the highly coupled and uncertain dynamics of the UAVs–payload system and the absence of onboard sensors on the payload, an explicit dynamic model is difficult to obtain and the payload state cannot be directly measured. To address these limitations, a Centralized Model-Free Control (CMFC) strategy is adopted, allowing control to be achieved without relying on an accurate model of the system nor on onboard sensing of the payload. Instead, the payload position and orientation are estimated from the measurements provided by the cooperating UAVs. The MFC-based approach is combined with a force allocation scheme to distribute the global control effort among the UAVs in a coordinated manner, enabling cooperative transportation despite modeling uncertainties and limited payload measurements. In addition, force-based allocation metrics are investigated as analytical indicators for comparing cooperative transport configurations with different numbers of UAVs and attachment geometries. Rather than seeking an optimal configuration, this analysis provides insight into the relative efficiency of each setup and supports the selection of suitable attachment layouts or the estimation of the number of UAVs required for a given task. The proposed control architecture is evaluated through numerical simulations, showing accurate trajectory tracking, robustness to disturbances and consistent cooperative behavior of the UAV team. These results highlight the effectiveness of the MFC-based centralized strategy and its relevance for cooperative aerial transportation applications.
Ayoub et al. (Tue,) studied this question.