Simple tension distribution converting workspace commands for 2-joint arm with 3 pairs of 6 tendons

Safety and general versatility are necessary for robots to perform various tasks in human living area. There are tendon based manipulators with nonlinear springs as a manipulator for the requirement. In this paper, we propose simple tension distribution method utilizing an advantage of biological extremity structure for tendon mechanisms to overcome weaknesses of a conventional method using pseudo inverse matrix. The human body structure and a polar coordinate definition for workspace contribute to the simple calculation. The proposed method takes account not only of weaknesses of the conventional method such as tension limit problem, but also of workspace command priority. The capability to directly consider workspace command priority makes the proposed method more useful. Because in many cases where robots perform tasks, workspace commands will be given, not joint torque or stiffness. Effectiveness of the proposed method is confirmed by a numerical calculation.