  In this paper, first the full dynamics of aerial transportation of a rigid
body with arbitrary number of quadrotors is derived. Then a control strategy is
proposed to convey the nonuniform rigid body appropriately to the desired
trajectory. In the dynamical model of this transportation system, not only the
load is considered as a nonuniform and non-homogeneous rigid body but also
mass, flexibility, and tension of the cables are considered. Each cable is
modeled as successive masses, springs, and dampers where each mass, spring, and
damper has 4 degrees of freedom (DOF). The Euler-Lagrange equations are used to
derive the motion equation. The control strategy includes three loops of
attitude control, formation control, and navigation control. The sliding mode
control is designed based on multi-agent systems for the formation control
where the controller is proven to be asymptotically stable. The navigation
control loop, based on the load states, guarantees that the load reaches the
desired location. Finally, numerical examples and simulations are presented to
verify the appropriate operation of the proposed system for transporting both
homogeneous and non-homogeneous bodies by spreading quadrotors according to
mass distribution of the body.
