Development and testing of a wearable passive lower-limb support exoskeleton to support industrial workers

Abstract A custom-designed, wearable, lightweight, and passive exoskeleton was proposed to provide gravity support for industrial workers to reduce prevalence of musculoskeletal disorders, joint injures, and arthritis caused by repeatedly or persistently squatting task. The designed exoskeleton can act as a wearable chair to allow workers to squat for an extended period when performing prolonged tasks. The exoskeleton employs torsion springs to store energy harvested from the squatting motion, and the stored energy is released to help the workers stand up. Dimensions optimization designs based on the finite element analysis program were implemented for a lightweight of the device. Besides, the exoskeleton effectiveness was investigated by performing an ergonomic assessment on muscular activity, plantar pressure, endurance time, and comfort. The plantar pressure and electromyography of rectus femoris, biceps femoris, vastus medialis, and vastus laterals were measured in a simulated assembly task with the knee bend for three different angles (60°, 90°, 120°) under two conditions of with and without the exoskeleton. The endurance time was recorded in three different static squatting tasks. The comfort with the exoskeleton was recorded. Under the condition of wearing the exoskeleton, the average reduction of muscle activity was 44.8–71.5%, and the plantar pressure was 58.5–64.2%. The exoskeleton contributed to an increase in endurance time from 2.76 to 13.58 min. Moreover, 70% of the subjects exhibited a comprehensive exoskeleton comfort score of higher than 70. The experimental results demonstrated that this exoskeleton has good potential to reduce physical workload and increase endurance time during industrial assembly tasks.