Decentralized object transportation by two nonholonomic mobile robots exploiting only implicit communication

This paper addresses the problem of cooperative object transportation by two nonholonomic wheeled robots, with the coordination relying exclusively on implicit communication. We implement a leader-follower scheme, considering compliant contact between the object and the follower. Only the leader has knowledge of the object´s goal configuration. The follower employs force/torque measurements to keep the contact stable and align itself with the object. The control scheme of the follower is based on the prescribed performance methodology guaranteeing thus the satisfaction of certain predefined force/torque constraints. In this way, the overall system acts as a perturbed version of the nominal car-like model. As a result, the leader implements a discontinuous control scheme, that drives robustly the system arbitrarily close to the goal configuration. No explicit data is exchanged among the robots, thus reducing bandwidth and increasing robustness and stealthiness. Finally, the proposed method is experimentally validated using two Pioneer mobile robots interconnected with a rod.