Heo Ung, Feng Jirou, Kim Sangjoon J, Kim Jung
IEEE Trans Neural Syst Rehabil Eng. 2022;30:2175-2185. doi: 10.1109/TNSRE.2022.3196361. Epub 2022 Aug 11.
To prevent lower back pain (LBP) in the industrial workplace, various powered back support exoskeletons (BSEs) have been developed. However, conventional kinematics-triggered assistance (KA) strategies induce latency, degrading assistance efficiency. Therefore, we proposed and experimentally evaluated a surface electromyography (sEMG)-triggered assistance (EA) strategy. Nine healthy subjects participated in the lifting experiments: 1) external loads test, 2) extra latency test, and 3) repetitive lifting test. In the external loads test, subject performed lifting with four different external loads (0 kg, 7.5 kg, 15 kg, and 22.5 kg). The assistance was triggered earlier by EA compared to KA from 114 ms to 202 ms, 163 ms to 269 ms for squat and stoop lifting respectively, as external loads increased from 0 kg to 22.5 kg. In the extra latency test, the effects of extra latency (manual switch, 0 ms, 100 ms and 200 ms) in EA on muscle activities were investigated. Muscle activities were minimized in the fast assistance (0 ms and 100 ms) condition and increased with extra latency. In the repetitive lifting test, the EA strategy significantly reduced L1 muscle fatigue by 70.4% in stoop lifting, compared to KA strategy. Based on the experimental results, we concluded that fast assistance triggered by sEMG improved assistance efficiency in BSE and was particularly beneficial in heavy external loads situations. The proposed assistive strategy can be used to prevent LBP by reducing back muscle fatigue and is easily applicable to various industrial exoskeleton applications.
为预防工业工作场所的下背痛（LBP），已研发出多种动力背部支撑外骨骼（BSE）。然而，传统的运动学触发辅助（KA）策略会产生延迟，降低辅助效率。因此，我们提出并通过实验评估了一种表面肌电图（sEMG）触发辅助（EA）策略。九名健康受试者参与了举重实验：1）外部负荷测试，2）额外延迟测试，3）重复举重测试。在外部负荷测试中，受试者使用四种不同的外部负荷（0千克、7.5千克、15千克和22.5千克）进行举重。随着外部负荷从0千克增加到22.5千克，与KA相比，EA触发辅助的时间更早，深蹲和弯腰举重分别提前114毫秒至202毫秒、163毫秒至269毫秒。在额外延迟测试中，研究了EA中额外延迟（手动切换，0毫秒、100毫秒和200毫秒）对肌肉活动的影响。在快速辅助（0毫秒和100毫秒）条件下，肌肉活动最小化，并随着额外延迟而增加。在重复举重测试中，与KA策略相比，EA策略在弯腰举重时显著降低了L1肌肉疲劳70.4%。基于实验结果，我们得出结论，sEMG触发的快速辅助提高了BSE的辅助效率，在重外部负荷情况下尤其有益。所提出的辅助策略可通过减少背部肌肉疲劳来预防LBP，并且易于应用于各种工业外骨骼应用。
