Design of a Self-Aligning Four-Finger Exoskeleton for Finger Abduction/Adduction and Flexion/Extension Motion.

For wearable four-finger exoskeletons, it is still a challenge to design the metacarpophalangeal (MCP)joint abduction/adduction (a/a) kinematic chain and achieve axes self-aligning. This paper proposes a novel exoskeleton for four fingers that features a high degree of dexterity enabling MCP joint flexion/extension (f/e) and a/a motion. Other features of the exoskeleton include a self-aligning mechanism that absorbs misalignment between the exoskeleton and human joints, the ability to accommodate fingers of different sizes, and a compact design that allows simultaneous a/a motion without interference. This paper presents the exoskeleton's kinematic model, optimizes the range of motion (ROM), and length of the exoskeleton linkage using the Genetic Algorithm. We compare the four-finger MCP joint's ROM and fingertip workspace with and without the exoskeleton. Our experiments show that the proposed exoskeleton has no significant impact on the natural ROM of the four-finger MCP joint, enables the fingers to cover an average of 82.96% of the original workspace, and can reach a significant portion of the fingertip workspace.