Inverse Kinematics of a Parallel Mechanism with an Offset Structural Design for Prosthetic Wrist Motions

Recent developments in upper limb wrist prosthetics allow for amputees to closely mimic the motions of a healthy human wrist. Although many active wrist prosthetics can flex and extend, relatively little work is done with their ability to pronate and supinate without the use of additional motors between the region where the forearm meets the hand. This paper reports a 3SPS-S-3RRR mechanism that provides quasi-spherical motions, mimicking a wrist's ability to flex and extend. It is also designed to offer rotational motion with offset Kresling arms to achieve motions conforming with pronation and supination. The paper explores the kinematics of the mechanism and introduces the use of motion capture acquisition in further studies.