  This paper proposes a decentralized passive impedance control scheme for
collaborative grasping using under-actuated aerial manipulators (AMs). The AM
system is formulated, using a proper coordinate transformation, as an
inertially decoupled dynamics with which a passivity-based control design is
conducted. Since the interaction for grasping can be interpreted as a feedback
interconnection of passive systems, an arbitrary number of AMs can be modularly
combined, leading to a decentralized control scheme. Another interesting
consequence of the passivity property is that the AMs automatically converge to
a certain configuration to accomplish the grasping. Collaborative grasping
using 10 AMs is presented in simulation.
