Object dynamics virtualization by robotic assistance for cooperative object handling with human

This paper proposes an object dynamics virtualization that enables a human operator to handle the object easy for a given task by changing dynamics of the object by a robot assistance. The proposed method uses a force sensor fixed between an end effector of the manipulator and an object to measure force/torque applied by the manipulator to the object. Then, force/torque applied by an operator are estimated by using a disturbance observer, which subtracts the sensing force/torque from those calculated based on the object acceleration. Using the force sensor makes implementation easier by isolating the object dynamics from those of the manipulator. By using a virtual internal model driven by the estimated force/torque, a task-oriented mechanical impedance is given to the object that is in reality heavy and unbalanced as if it were lighter and well-balanced. Experiments to virtualize dynamics of a rod with a weight at one end, i.e., an example of an unbalanced object, to be a uniform disc by a SCARA manipulator with three degrees-of-freedom were conducted, and the results showed the validity of the proposed method.