A Semi-Active Occupational Shoulder Exoskeleton for Overhead Work with Free Mode and Personalized Assistive Torque
Jin Tian, Baichun Wei, Chifu Yang, Haijiao Wang, Feng Jiang, Hong Huang, Xiang Li, Haiqi Zhu, Chunzhi Yi
AI summary
Problem
Existing shoulder exoskeletons rely on fixed assistive torque profiles that fail to adapt to different users and tasks, and they often store elastic energy at low angles, which interferes with natural daily movements.
Approach
The authors designed a motorized torque generator that electrically adjusts both the peak assistive torque angle and magnitude, paired with a hybrid control strategy that switches between a zero-resistance free mode and personalized assistive modes based on user height and weight.
Key results
- Motorized generator enables electrical tuning of peak assistive torque angle and magnitude
- Hybrid control strategy successfully implements non-interfering free mode and three personalized assistive levels
- Reduces shoulder muscle activation by up to 55.03% during overhead tasks
- Demonstrates significantly lower backdrivability resistance and better torque tracking than fixed-assistance exoskeletons
Why it matters
Provides a highly adaptable, user-specific solution to prevent work-related shoulder injuries for industrial workers performing overhead tasks.
Abstract
Current passive or semi-active shoulder exoskeletons for overhead work provide fixed assistive torque for all partici- pants and tasks, which lacks adaptability. In addition, due to the need to store energy at low elevation angles, they may increase physical demand on the user when assistance is not required. This study presents a novel semi-active shoulder exoskeleton that can provide the free mode (i.e., no assistance) and personalized assistive torque to assist overhead work. The exoskeleton includes the motorized torque generator and hybrid control strategy. The motorized torque generator equipped with servo motor and en- coder is characterized by its ability to electrically adjust the peak assistive torque angle and peak torque. In addition, we propose a hybrid control strategy with free and assistive modes. The free mode allows the exoskeleton to not interfere with movements that do not require assistance. The assistive mode provides personalized torque with three levels based on the height and weight of the user. Experimental results validated the exoskeleton’s mechanical per- formance (e.g., high backdrivability) and its assistive effectiveness. The results showed that the exoskeleton could reduce shoulder muscle activation by up to 55.03% and demonstrated a significant difference compared to fixed assistance.