  This paper addresses the problem of cooperative object transportation for
multiple Underwater Vehicle Manipulator Systems (UVMSs) in a constrained
workspace involving static obstacles. We propose a Nonlinear Model Predictive
Control (NMPC) approach for a team of UVMSs in order to transport an object
while avoiding significant constraints and limitations such as: kinematic and
representation singularities, obstacles within the workspace, joint limits and
control input saturations. More precisely, by exploiting the coupled dynamics
between the robots and the object, and using certain load sharing coefficients,
we design a distributed NMPC for each UVMS in order to cooperatively transport
the object within the workspace's feasible region. Moreover, the control scheme
adopts load sharing among the UVMSs according to their specific payload
capabilities. Additionally, the feedback relies on each UVMS's locally
measurements and no explicit data is exchanged online among the robots, thus
reducing the required communication bandwidth. Finally, real-time simulation
results conducted in UwSim dynamic simulator running in ROS environment verify
the efficiency of the theoretical finding.
