Design and Evaluation of Load Distributing Upper-Limb Exoskeleton Using Wired Clutch Mechanism

Abstract

Musculoskeletal disorders are caused by repetitive tasks of a specific body part, uncomfortable working posture, strong labor intensity, excessive force, and lack of rest, resulting in minor damage to muscles, blood vessels, and nerves. The statistics of work-related musculoskeletal disorders for 12 years between 2006 and 2017 in Korea show that the number of people with musculoskeletal disorders between 5,000 and 7,000 per year is steady. In the United States, the number of people with musculoskeletal disorders in 2016 is about 280,000. In Europe, in 2012, 47% of EURO27 country workers have back pain, and 45% of them have upper-extremity musculoskeletal disorders. Workers are easily exposed to musculoskeletal disorders and measures are needed to prevent them. In this study, the author proposed the development of a passive upper limb exoskeleton robot for the prevention of upper-limb related musculoskeletal disorders of workers handling heavy load manually. In general, exoskeleton robots include actuators such as motors, pneumatic and hydraulic actuators, control boards for controlling actuators, and sensors for detecting wearer's intentions. However, passive exoskeleton robots are designed to exclude these electronic devices and mechanically operate by a mechanism to increase muscle strength or reduce muscle fatigue. Therefore, it is light and compact in comparison with the active type, and there is no time limitation due to the battery, which is advantageous to be introduced in the industrial field. To this end, the author proposes a mechanism that uses a wire to distribute the load applied to the arm to the torso through the wire when the object is lifted. In order to evaluate the efficiency of the proposed exoskeleton robot, experiments were carried out to evaluate the subject 's subjective evaluation through the difference of muscle fatigue, posture holding time, and borg RPE scale according to the with or without of exoskeleton. The comparative analysis showed that the muscle fatigue decreased, and the posture maintenance time was increased and the Borg scale for the arm part was reduced.