We present a novel approach to cooperative aerial transportation through a team of drones, using optimal control theory and a hierarchical control strategy. We assume the drones are connected to the payload through rigid attachments, essentially transforming the whole system into a larger flying object with "thrust modules" at the attachment locations of the drones. We investigate the optimal arrangement of the thrust modules around the payload, so that the resulting system is robust to disturbances. We choose the $\mathcal{H}_2$ norm as a measure of robustness, and propose an iterative optimization routine to compute the optimal layout of the vehicles around the object. We experimentally validate our approach using four drones and comparing the disturbance rejection performances achieved by two different layouts (the optimal one and a sub-optimal one), and observe that the results match our predictions.

翻译：我们提出了一种通过无人机团队实现协作空中运输的新方法，该方法基于最优控制理论与分层控制策略。假设无人机通过刚性连接件与负载相连，从而实质上将整个系统转化为一个更大的飞行物体，并在无人机连接位置处设有“推力模块”。我们研究了推力模块围绕负载的最优布局，使所得系统对扰动具有鲁棒性。以$\mathcal{H}_2$范数作为鲁棒性度量指标，提出一种迭代优化算法来计算无人机围绕物体的最优布局。通过四架无人机实验验证了该方法，比较了两种不同布局（最优布局与次优布局）的抗扰动性能，观察到的实验结果与理论预测吻合。