Cooperative Swinging of Complex Pendulum-Like Objects: Experimental Evaluation

Cooperative dynamic object manipulation increases the manipulation repertoire of multiagent teams. As a first step toward cooperative dynamic object manipulation, we present an energy-based controller for cooperative swinging of two-agent pendulum-like objects. Projection of the complex underactuated mechanism onto an abstract cart-pendulum allows us to separate desired and undesired oscillations. The desired oscillation is excited up to a desired energy level, while an undesired oscillation can be actively damped. Communication between the agents is restricted to force feedback. The controller can render leader and follower agents. The follower actively assists the swinging task by imitating the leader's energy flow. Real-world experiments with a robot and a human swinging complex pendulum-like objects are presented. The experimental results indicate that no simultaneous damping of the undesired oscillation is needed, also because it disturbs the human partner. A successful contribution of the robotic follower to the swing-up effort in interaction with a human leader supports the proposed control approach.