Department of Mechanical, Aerospace, and Biomedical Engineering, University of Tennessee, 1512 Middle Drive, Knoxville 37996, TN.
Department of Rehabilitation Services, Brain and Spine Institute, University of Tennessee Medical Center, 1924 Alcoa Highway, Knoxville, TN 37920.
J Biomech Eng. 2022 Nov 1;144(11). doi: 10.1115/1.4054639.
Mechanically passive exoskeletons may be a practical and affordable solution to meet a growing clinical need for continuous, home-based movement assistance. We designed, fabricated, and preliminarily evaluated the performance of a wearable, passive, cam-driven shoulder exoskeleton (WPCSE) prototype. The novel feature of the WPCSE is a modular spring-cam-wheel module, which generates an assistive force that can be customized to compensate for any proportion of the shoulder elevation moment due to gravity. We performed a benchtop experiment to validate the mechanical output of the WPCSE against our theoretical model. We also conducted a pilot biomechanics study (eight able-bodied subjects) to quantify the effect of a WPCSE prototype on muscle activity and shoulder kinematics during three shoulder movements. The shoulder elevation moment produced by the spring-cam-wheel module alone closely matched the desired theoretical moment. However, when measured from the full WPCSE prototype, the moment was lower (up to 30%) during positive shoulder elevation and higher (up to 120%) during negative shoulder elevation compared to the theoretical moment, due primarily to friction. Even so, a WPCSE prototype, compensating for about 25% of the shoulder elevation moment due to gravity, showed a trend of reducing root-mean-square electromyogram magnitudes of several muscles crossing the shoulder during shoulder elevation and horizontal adduction/abduction movements. Our results also showed that the WPCSE did not constrain or impede shoulder movements during the tested movements. The results provide proof-of-concept evidence that our WPCSE can potentially assist shoulder movements against gravity.
机械被动式外骨骼可能是满足不断增长的居家连续移动辅助临床需求的实用且负担得起的解决方案。我们设计、制造并初步评估了一种可穿戴、无源、凸轮驱动的肩部外骨骼（WPCSE）原型的性能。WPCSE 的新颖之处在于采用了模块化的弹簧凸轮轮模块，该模块可产生辅助力，可根据重力引起的肩部提升力矩的任何比例进行定制补偿。我们进行了一项台式实验，以根据我们的理论模型验证 WPCSE 的机械输出。我们还进行了一项初步的生物力学研究（八位健康受试者），以量化 WPCSE 原型对三种肩部运动中肌肉活动和肩部运动学的影响。弹簧凸轮轮模块产生的肩部提升力矩与所需的理论力矩非常吻合。然而，当从完整的 WPCSE 原型进行测量时，与理论力矩相比，在正向肩部提升时的力矩较低（低至 30%），在负向肩部提升时的力矩较高（高达 120%），这主要是由于摩擦力造成的。即便如此，补偿重力引起的肩部提升力矩约 25%的 WPCSE 原型显示出在肩部提升和水平内收/外展运动中，跨越肩部的几大肌肉的均方根肌电图幅度有降低的趋势。我们的研究结果还表明，在测试的运动中，WPCSE 不会限制或阻碍肩部运动。这些结果提供了概念验证证据，表明我们的 WPCSE 有可能协助肩部对抗重力运动。
