  This paper proposes a task-space control protocol for the collaborative
manipulation of a single object by N robotic agents. The proposed methodology
is decentralized in the sense that each agent utilizes information associated
with its own and the object's dynamic/kinematic parameters and no on-line
communication takes place. Moreover, no feedback of the contact forces/torques
is required, therefore employment of corresponding sensors is avoided. An
adaptive version of the control scheme is also introduced, where the agents'
and object's dynamic parameters are considered unknown. We also use unit
quaternions to represent the object's orientation. In addition, load sharing
coefficients between the agents are employed and internal force regulation is
guaranteed. Finally, experimental studies with two robotic arms verify the
validity and effectiveness of the proposed control protocol.
