This paper presents a shoulder joint for a human-like robotic arm. This joint mechanism is composed of two ball joints laying back to back and the range of motion is larger than that of a usual ball joint. Since the joint is driven by the mutually inter-connected air cylinders, the control signal can be operated equally with a normal ball joint shoulder. The prototype of the joint with 6 air cylinders and its kinematic model were developed to confirm its range of motion. We also achieved an overhand throwing motion with a robotic arm using the proposed shoulder mechanism thanks to the large moving range.
2016 The Robotics Society of Japan