Nonlinear impedance control to maintain robot position within specified ranges

This paper proposes a nonlinear impedance control approach to keeping the position and orientation of a robot within a specified region even if excessive force and moment are applied to the robot. Specifically, this paper addresses how to design desired nonlinear impedance characteristics so that the robot position and orientation do not exceed the limits of the specified region. First, general conditions for designing the nonlinear impedance characteristics are derived. Second, the stability of the nonlinear impedance characteristics is analyzed. Then, the proposed design method is applied to an example. Finally, the effectiveness of the method is verified by experiments with a real robot.