Rigid, Soft, Passive, and Active: A Hybrid Occupational Exoskeleton for Bimanual Multijoint Assistance

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Physically demanding work is still common in western countries, with large proportions of the workforce that are exposed for more than a quarter of their working time to tiring postures or repetitive tasks: the shoulder is one of the main body areas susceptible to work-related musculo-skeletal disorders. Recent advancements in assistive technology have provided new instruments to promote safety and reduce workload. Colloquially referred to as occupational exoskeletons (OEs), these wearable devices are usually spring-loaded, and provide gravity support for overhead tasks. OEs for upper limbs are usually single-joint exoskeletons and assist shoulder flexion/extension; they do not provide support to distal joints such as the elbow. In the present work, starting from a commercially available exoskeleton, we propose an innovative concept of hybrid upper-limb OEs. We combined a spring-loaded shoulder exoskeleton with an active elbow exosuit to extend the capability of the OEs to provide gravitational support to both shoulder and elbow flexion-extension in strenuous manual tasks. The proposed device can reduce up to 32% of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">biceps</i> activity during the elbow flexion and up to 31% of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">deltoids</i> activity during the shoulder abduction. In-lab experimentation showed the potentials of such a hybrid approach in reducing the strain of the upper-limb muscles.