A two stage approach for distributed cooperative manipulation of an unknown object without explicit communication and unknown number of robots

This paper proposes a distributed algorithm for cooperatively manipulating an object rigidly grasped by a team of mobile manipulators. In order to increase the flexibility of the multi-robot cell and differently from other approaches, it is assumed that the object is completely unknown and there is not information exchange between robots. The devised strategy includes two stages: at the first stage, each robot estimates the object kinematic and dynamic parameters by applying specific contact wrenches, while, in the second stage, the estimated parameters are exploited within a distributed cooperative control framework that can be adopted, for instance, to control the interaction wrench exerted by the environment on the object or to implement a zero-force control algorithm. In addition to the total absence of communication and differently from existing solutions, the proposed technique assumes that each robot has not knowledge of the number of cooperative agents in the team and, remarkably, it is devised in the 3-dimensional space with the aim of handling both the position and the orientation of the object. Finally, the feasibility of the approach is proven via numerical simulations.