Decentralized cooperative manipulation and consensus through object sensing

Abstract

With the decrease in sensor and actuator costs decentralized control strategies have become increasingly attractive, aiming to use multiple simpler robots for achieving a global objective. The problem of reaching the global objective generally results in a consensus problem requiring communication amongst the agents. The cooperative manipulation problem, where a payload is manipulated using multiple robots, poses an attractive alternative: By using the payload's motion as the means of communication, the agents can reach consensus without using explicit communication. The advantage being that no additional bandwidth is required as the number of participating agents increases and all to all communication is effectively achieved.

Whereas previous works considered only the translation dynamics this thesis work considers the use of the full rigid body motion as a means of communication, such that the agents reach consensus on the desired wrench and the payload is stabilized at any desired configuration. As a possible application the towing of a payload by multiple UAV via cables is considered. This brings the additional challenge of underactuation from the perspective of each agent, since only forces can be used to control the full payload's motion.

The result is a decentralized nonlinear control law for the forces applied to a payload such that consensus is reached amongst the agents, the leader's control action is amplified and the payload is stabilized at any desired configuration. Proofs are constructed via Lyapunov arguments and the applicability of the control design to the aerial towing problem is validated in simulation.