Development of a cybernetic shoulder-a 3-DOF mechanism that imitates biological shoulder motion

In this paper, we develop a 3-degree of freedom (DOF) mechanism for humanoid robots, which we call the cybernetic shoulder. This mechanism imitates the motion of the human shoulder and does not have a fixed center of rotation, which enables unique human-like motion in contrast to the conventional design of anthropomorphic 7-DOF manipulators that have base three joint axes intersecting at a fixed point. Taking advantage of the cybernetic shoulder's closed kinematic chain, we can easily introduce the passive compliance adopting the elastic members. This is important for the integrated safety of humanoid robots that are inherently required to physically interact with the human.