KULEX-Wrist: Design and Analysis of Linkage-Driven Exoskeleton for Wrist Assistance

This paper presents a wrist exoskeleton called the KULEX (KIST Upper-Limb EXoskeleton)-wrist for activities of daily living assistance of the elderly and the disabled. A novel linkage-based structure of the rotational mechanism with three degrees of freedom is proposed. The proposed wrist mechanism is composed of two PUS (Prismatic-Universal-Spherical) serial chains and one RRR (Revolute-Revolute-Revolute) spherical chain. Besides, a combination of a planar slider-crank and spherical four-bar linkages was employed as a driving mechanism for power transmission. Kinematic analysis was conducted to understand its working principle. Then, the dimensions of all the linkages were synthesized to meet the structural design suitable for the wearable exoskeleton and the transmission quality. In addition, motion twists and wrenches were geometrically derived. Finally, a prototype of the KULEX-wrist was designed, and then its performance of mechanical stiffness, motion capability, and power assistance was verified.