Novel Mechanism of Upper Limb Exoskeleton for Weight Support

Industrial workers suffer from musculoskeletal disorders. Especially, the shoulder disorder affects many working movements. To reduce it, various assistive devices have been developed. However, because of the complex shoulder, there are several issues to apply the devices to the actual workspace, such as bulky size or heavyweight. In this paper, a novel mechanism consisting of three sub-mechanisms is suggested. It is focused on the weight support as the main function. This target-oriented approach can reduce the complexity of the mechanism and can lead to a light and compact structure. The mechanism is designed to compensate three main issues between the exoskeleton and shoulder joint: various arm raising direction at the initial posture, protraction/retraction, and scapulohumeral rhythm. The design parameters were optimized by using the center of the rotation of the shoulder, and the whole structure was designed with a trajectory error of 5 mm or less.