Low-Impedance Physical Human-Robot Interaction Using an Active–Passive Dynamics Decoupling

When a robot manipulator is designed to interact with a human being, performance is often compromised due to safety constraints. The interaction becomes thus less responsive and less intuitive, making the use of such robots difficult to implement in an industrial context. This letter revisits the concept of macro-mini manipulator to improve the interaction bandwidth, by introducing a novel low impedance mini mechanism specifically designed for physical human-robot cooperation. This mini structure, consisting of passive joints, combined with a macro robot is experimentally compared with a nonredundant fully actuated manipulator. The experiments demonstrate that the resulting effective impedance is greatly reduced with the addition of the passive mechanism. Therefore, such an architecture has the potential to provide passive contacts and safer interactions while providing large payload capability, extensive range of motion, and end-effector agility and responsiveness.