  This paper investigates a fully distributed cooperation scheme for networked
mobile manipulators. To achieve cooperative task allocation in a distributed
way, an adaptation-based estimation law is established for each robotic agent
to estimate the desired local trajectory. In addition, wrench synthesis is
analyzed in detail to lay a solid foundation for tight cooperation tasks.
Together with the estimated task, a set of distributed adaptive controllers is
proposed to achieve motion synchronization of the mobile manipulator ensemble
over a directed graph with a spanning tree irrespective of the kinematic and
dynamic uncertainties in both the mobile manipulators and the tightly grasped
object. The controlled synchronization alleviates the performance degradation
caused by the estimation/tracking discrepancy during the transient phase. The
proposed scheme requires no persistent excitation condition and avoids the use
of noisy Cartesian-space velocities. Furthermore, it is independent from the
object's center of mass by employing formation-based task allocation and a
task-oriented strategy. These attractive attributes facilitate the practical
application of the scheme. It is theoretically proven that convergence of the
cooperative task tracking error is guaranteed. Simulation results validate the
efficacy and demonstrate the expected performance of the proposed scheme.
