Design and analysis of WELiBot for assisting upper limb motion

Upper limb motor dysfunction significantly impacts daily activities and quality of life for individuals with stroke. Existing assistive robots often struggle to balance portability, ease of use, and motion assistance. This research presents WELiBot, a novel wearable end-effector-type upper limb assistive robot, designed with a 4R-5R parallel mechanism and an arc-shaped guide rail to provide controlled assistance in lifting, reaching, and circumferential motions. The study introduces the conception of the robot design, focusing on its functional requirements and mechanical structure. The kinematic and static characteristics of WELiBot were analyzed to evaluate its feasibility and effectiveness. Based on this design, a prototype with a 1/4 arc-shaped guide rail was fabricated to test motion feasibility and assistance effects. To assess its performance, electromyography experiments were conducted with four healthy participants. The results showed a significant reduction in biceps brachii muscle activity, confirming the robot's ability to reduce user effort. Future work will focus on attaching the guide rail to the body for improved usability and refining the control strategy to enhance motion assistance and adaptability in daily life support applications.