Design and Preliminary Testing of WELiBot: A Wearable End-Effector Type Upper Limb Assistive Robot

A full-scale prototype of a 3-DOF 4R-5R parallel mechanism for a wearable end-effector type upper limb assistive robot called "WELiBot" is fabricated. Owing to its kinematic structure, it can assist the user's upper limb in motions where the generation of vertical force and constrain along/on certain geometries are required. EMG measurements were collected from a healthy person as a preliminary evaluation prior to clinical trials with hemiplegic patients. Muscle activities of the person's upper limb were measured for the cases with and without assistance, and the results were compared. The results show that when the robot-assisted the arm-raising motion, activity in specific muscles of the upper arm and forearm decreased significantly. This confirmed the effectiveness of the motion assistance by the robot. On the other hand, no decrease in activity was observed in the shoulder muscles.