  Cooperative transportation by multi-aerial robots has the potential to
support various payloads and improve failsafe against dropping. Furthermore,
changing the attachment positions of robots according payload characteristics
increases the stability of transportation. However, there are almost no
transportation systems capable of scaling to the payload weight and size and
changing the optimal attachment positions. To address this issue, we propose a
cooperative transportation system comprising autonomously executable software
and suitable hardware, covering the entire process, from pre-takeoff setting to
controlled flight. The proposed system decides the formation of the attachment
positions by prioritizing controllability based on the center of gravity
obtained from Bayesian estimations with robot pairs. We investigated the
cooperative transportation of an unknown payload larger than that of whole
carrier robots through numerical simulations. Furthermore, we performed
cooperative transportation of an unknown payload (with a weight of about 3.2 kg
and maximum length of 1.76 m) using eight robots. The proposed system was found
to be versatile with regard to handling unknown payloads with different shapes
and center-of-gravity positions.
