Development of a Soft Semi-Active Suit Using Electro-Static Clutches for Assisting Static Holding Tasks

Assistive suits are used in industries to prevent MSDs (musculoskeletal disorders) and improve work efficiency and productivity that can be affected by excessive manual labor. Recently, soft assistive suits have been developed, distinguished by their comfortable fit, easy wearability, and compact design. In this study, we propose a soft semi-active suit based on an ES clutch (electrostatic clutch) to assist in the isometric contraction of arm muscles during a holding task. The assistive suit, weighing only 742 g, comprises multi-layer ES clutches for providing support force, cables for force transmission, and soft strain sensors for measuring the elbow joint angle. The ES clutch provides an effective support force (240 N) with a light weight (50 g), a thin thickness (4 mm) and a fast response time (39 ms). The integrated soft component system designed for mobile applications is capable of operating for a duration of 11 hours. A trigger mechanism has been implemented to activate the actuator at specific angles in the elbows. The supporting performance of the proposed system was verified by surface electromyography (sEMG) experiments during a holding task. The sEMG activity of the brachioradialis, the brach biceps, and the anterior deltoid, the major muscles of the forearm, decreased by approximately 55.2%, 54.8% and 63.4%, respectively, during the holding task.