Design and Experimental Evaluation of a Semi-Passive Upper-Limb Exoskeleton for Workers With Motorized Tuning of Assistance

Soft pneumatic elbow exoskeleton reduces the muscle activity, metabolic cost and fatigue during holding and carrying of loads

“…While the assistance with two arms at 1.22 bar produces 7.2 Nm of torque and 100% support for a 2.2 kg load, 3.65 bar produces 22 Nm of torque and 100% support for a 6.6 kg load. With increasing assistance torque, we expect increased benefits for the user as was found for a semi-passive shoulder exoskeleton 38 . At a pressure of 3 bar, an elbow assistance torque of 27.6 Nm was achieved with a comparable pneumatic design 52 .…”

“…However, slightly larger benefits are expected for use cases where a tethered system could be used (i.e., fixed workplace), as used in our experiments. If a system mass of 3 kg for an autonomous Carry can be achieved, this will be close to passive contenders such as PAEXO (1.8 kg 33 ), and this would be in the range or slightly below other promising designs, such as the motor-powered exosuits (4 kg for two elbows 43 ) or semi-passive systems (5 kg H-Pulse 38 ). Use cycles of greater than 73 seem reasonable for mobile applications, and this could be doubled with a 0.4 kg increase in either the battery or tank weight.…”

“…A semi-passive shoulder exoskeleton (12 kg) was also included, which uses a motor to change the assistance force of two springs 37 . Recently, another semi-passive concept demonstrated reductions in user’s shoulder muscle activity and heart rate during overhead work (H-PULSE, 5 kg 38 ).…”

A physiological and biomechanical investigation of three passive upper-extremity exoskeletons during simulated overhead work

“…To date, a multitude of studies have noted positive biomechanical and physiological results for this class of exoskeleton. These results include reductions in muscle activity during static and dynamic movements (Rashedi et al 2014, Kim, Nussbaum, Mokhlespour Esfahani, Alemi, Alabdulkarim, andRashedi 2018;Theurel et al 2018;Alabdulkarim and Nussbaum 2019;Gillette and Stephenson 2019;Schmalz et al 2019;Grazi et al 2020;Iranzo et al 2020;Yin et al 2020), decreases in the sum of joint torque in the upper arm (Sylla et al 2014), decreases in the effective load on the shoulder joint (Naito et al 2007), and decreases in heart rate (Schmalz et al 2019;Grazi et al 2020). That being said, physiological measures related to oxygen utilisation in the surrounding musculature can provide a complementary picture of how upper-extremity exoskeletons alter the capacity for muscles to do work and the subsequent likelihood of muscle fatigue.…”

Methodologies for evaluating exoskeletons with industrial applications

“…Some authors also try to investigate statistical dependencies between evaluation criteria like muscular activity in supported body regions, error proneness, and working speed [Alabdulkarim and Nussbaum 2019a], reductions in physical demand, discomfort, usability, and intention-to-use [Hensel and Keil 2019], reductions in muscular activity or reduced muscle fatigue and usage decision or system acceptance [Gillette and Stephenson 2019]. Other authors multidimensionally use or interpret the results of electromyography for, e.g., calculating supporting moments [Koopman et al 2020a], metabolic costs [Grazi et al 2020], mean user's power frequency [Rashedi et al 2014], or the system's efficiency [Yong et al 2019] as well as detecting changes in working speed [Baltrusch et al 2018] or in motions [Madinei et al 2020a]. The analysis of more muscle groups than only the directly supported ones can help to detect a physical burden as well as to derive further comfort and usability issues [Maurice et al 2020, van Engelhoven et al 2019, Weston et al 2018].…”