Effects of a lower-body exoskeleton device on metabolic cost and gait biomechanics during load carriage

Gregorczyk, Karen N.; Hasselquist, Leif; Schiffman, Jeffrey M.; Bensel, Carolyn K.; Obusek, John P.; Gutekunst, David J.

doi:10.1080/00140139.2010.512982

Cited by 116 publications

(62 citation statements)

References 39 publications

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“…Some full-body exoskeletons have resulted in large metabolic penalties (e.g. [7]) while lightweight ankle-foot exoskeletons have resulted in penalties of less than 3% for active autonomous 1 exoskeletons [4] and even close to zero for passive autonomous1 exoskeletons [5]. Reducing the penalty of wearing an exoskeleton in zero-work mode is mainly a design challenge, while increasing the difference between the zero-work condition and powered exoskeleton conditions is mainly a biomechanics challenge.…”

Section: Introductionmentioning

confidence: 99%

Reducing the metabolic cost of walking with an ankle exoskeleton: interaction between actuation timing and power

Galle

Malcolm

Collins

et al. 2017

J NeuroEngineering Rehabil

173

162

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BackgroundPowered ankle-foot exoskeletons can reduce the metabolic cost of human walking to below normal levels, but optimal assistance properties remain unclear. The purpose of this study was to test the effects of different assistance timing and power characteristics in an experiment with a tethered ankle-foot exoskeleton.MethodsTen healthy female subjects walked on a treadmill with bilateral ankle-foot exoskeletons in 10 different assistance conditions. Artificial pneumatic muscles assisted plantarflexion during ankle push-off using one of four actuation onset timings (36, 42, 48 and 54% of the stride) and three power levels (average positive exoskeleton power over a stride, summed for both legs, of 0.2, 0.4 and 0.5 W∙kg−1). We compared metabolic rate, kinematics and electromyography (EMG) between conditions.ResultsOptimal assistance was achieved with an onset of 42% stride and average power of 0.4 W∙kg−1, leading to 21% reduction in metabolic cost compared to walking with the exoskeleton deactivated and 12% reduction compared to normal walking without the exoskeleton. With suboptimal timing or power, the exoskeleton still reduced metabolic cost, but substantially less so. The relationship between timing, power and metabolic rate was well-characterized by a two-dimensional quadratic function. The assistive mechanisms leading to these improvements included reducing muscular activity in the ankle plantarflexors and assisting leg swing initiation.ConclusionsThese results emphasize the importance of optimizing exoskeleton actuation properties when assisting or augmenting human locomotion. Our optimal assistance onset timing and average power levels could be used for other exoskeletons to improve assistance and resulting benefits.Electronic supplementary materialThe online version of this article (doi:10.1186/s12984-017-0235-0) contains supplementary material, which is available to authorized users.

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Section: Introductionmentioning

confidence: 99%

Reducing the metabolic cost of walking with an ankle exoskeleton: interaction between actuation timing and power

Galle

Malcolm

Collins

et al. 2017

J NeuroEngineering Rehabil

173

162

View full text Add to dashboard Cite

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“…A number of research and industry groups are developing powered lower limb exoskeletons to help people in industry (Hodson, 2014; Lamothe, 2014), military (Zoss et al, 2006; Gregorczyk et al, 2010; Raytheon XOS 2 Exoskeleton, Second-Generation Robotics Suit: Army-Technology, 2010; France’s Slender Hercule Exoskeleton Is No Lightweight, 2012; Asbeck et al, 2015), and healthcare settings (Gancet et al, 2012; Zeilig et al, 2012; Kolakowsky-Hayner et al, 2013; Sczesny-Kaiser et al, 2013; Farris et al, 2014). Progress in hardware development has been rapid and widespread (Huo et al, 2014), but control over these advanced devices still needs significant improvement for exoskeletons to be adopted widely in everyday use (Yan et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Influence of Power Delivery Timing on the Energetics and Biomechanics of Humans Wearing a Hip Exoskeleton

Young

Foss

Gannon

et al. 2017

Front. Bioeng. Biotechnol.

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A broad goal in the field of powered lower limb exoskeletons is to reduce the metabolic cost of walking. Ankle exoskeletons have successfully achieved this goal by correctly timing a plantarflexor torque during late stance phase. Hip exoskeletons have the potential to assist with both flexion and extension during walking gait, but the optimal timing for maximally reducing metabolic cost is unknown. The focus of our study was to determine the best assistance timing for applying hip assistance through a pneumatic exoskeleton on human subjects. Ten non-impaired subjects walked with a powered hip exoskeleton, and both hip flexion and extension assistance were separately provided at different actuation timings using a simple burst controller. The largest average across-subject reduction in metabolic cost for hip extension was at 90% of the gait cycle (just prior to heel contact) and for hip flexion was at 50% of the gait cycle; this resulted in an 8.4 and 6.1% metabolic reduction, respectively, compared to walking with the unpowered exoskeleton. However, the ideal timing for both flexion and extension assistance varied across subjects. When selecting the assistance timing that maximally reduced metabolic cost for each subject, average metabolic cost for hip extension was 10.3% lower and hip flexion was 9.7% lower than the unpowered condition. When taking into account user preference, we found that subject preference did not correlate with metabolic cost. This indicated that user feedback was a poor method of determining the most metabolically efficient assistance power timing. The findings of this study are relevant to developers of exoskeletons that have a powered hip component to assist during human walking gait.

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“…The MIT quasi-passive exoskeleton found an increase metabolism of 32% during assisted walking as compared to control [24]. In [25], a 60% increase of energy consumption was found when a prototype exoskeleton (EXO) was worn as compared with the control condition. However, it is premature to conclude that the walking with LEAD using the proposed method is beneficial over free walking.…”

Section: Resultsmentioning

confidence: 91%

Functional task based assistance during walking for a Lower Extremity Assistive Device

Shen

Chew

2014

2014 IEEE International Conference on Robotics and Automation (ICRA)

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In this paper, we propose a functional task based assistance controller to aid user in the walking task with our Lower Extremity Assistive Device (LEAD). Firstly, a gait period detector, which utilizes a Gaussian Mixture Model (GMM), is developed to estimate the user's current gait period among the six major periods. Then, an impedance based controller is used to apply assistive torques to the hip and knee joints of the user based on the functional task intended at the current gait period. To validate the above control scheme, preliminary experiments have been performed with one healthy subject walking on a treadmill. The results show that the gait period detector can effectively detect each gait period for the whole cycle. Based on measurements of the heart rate, the proposed assistance method has shown that it can effectively assist a human user in walking at speed of 1 km/h.

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Effects of a lower-body exoskeleton device on metabolic cost and gait biomechanics during load carriage

Cited by 116 publications

References 39 publications

Reducing the metabolic cost of walking with an ankle exoskeleton: interaction between actuation timing and power

Reducing the metabolic cost of walking with an ankle exoskeleton: interaction between actuation timing and power

Influence of Power Delivery Timing on the Energetics and Biomechanics of Humans Wearing a Hip Exoskeleton

Functional task based assistance during walking for a Lower Extremity Assistive Device

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