We study a robotic assistance system for handling of a long object that is difficult to support with one point. The robot grasps one end of the object and helps the human operator at the other end to carry it. Such a cooperative handling in a vertical plane is considered here. Human cooperative behavior is experimentally measured and analyzed to find the control strategy. To simplify the system, only kinesthetic information such as force, position and velocity is used. The control law in the horizontal direction can be modeled as impedance control, and that in the vertical direction is to maintain the posture of the object horizontally. In this method, the robot supports half of the gravitational load irrespective of the mass and length of the object. These control laws are implemented to a robot arm. The experimental results show that the robot and human can carry a long object cooperatively.
