Biological Joint Loading and Exoskeleton Design

Medrano, Roberto Leo; Rouse, Elliott J.; Thomas, Gray C.

doi:10.1109/tmrb.2021.3098920

Cited by 8 publications

(5 citation statements)

References 31 publications

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“…However, our results demonstrate that the current reductions in metabolic rate are not yet broadly perceptible in the short term. The difficulty of perceiving changes to metabolic rate motivates the consideration of alternative metrics which may be more clearly perceivable by users, including reduction of muscle fatigue [ 70 – 72 ], peak joint forces in arthritic joints [ 71 , 73 , 74 ], and user preference [ 31 , 75 – 77 ]. The development of perceivable and meaningful metrics to quantify success in future exoskeletons is an important challenge for the field.…”

Section: Discussionmentioning

confidence: 99%

Can humans perceive the metabolic benefit provided by augmentative exoskeletons?

Medrano

Thomas

Rouse

2022

J NeuroEngineering Rehabil

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Background The purpose of augmentative exoskeletons is to help people exceed the limitations of their human bodies, but this cannot be realized unless people choose to use these exciting technologies. Although human walking efficiency has been highly optimized over generations, exoskeletons have been able to consistently improve this efficiency by 10–15%. However, despite these measurable improvements, exoskeletons today remain confined to the laboratory. To achieve widespread adoption, exoskeletons must not only exceed the efficiency of human walking, but also provide a perceivable benefit to their wearers. Methods In this study, we quantify the perceptual threshold of the metabolic efficiency benefit provided during exoskeleton-assisted locomotion. Ten participants wore bilateral ankle exoskeletons during continuous walking. The assistance provided by the exoskeletons was varied in 2 min intervals while participants provided feedback on their metabolic rate. These data were aggregated and used to estimate the perceptual threshold. Results Participants were able to detect a change in their metabolic rate of 22.7% (SD: 17.0%) with 75% accuracy. This indicates that in the short term and on average, wearers cannot yet reliably perceive the metabolic benefits of today’s augmentative exoskeletons. Conclusions If wearers cannot perceive the benefits provided by these technologies, it will negatively affect their impact, including long-term adoption and product viability. Future exoskeleton researchers and designers can use these methods and results to inform the development of exoskeletons that reach their potential.

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Section: Discussionmentioning

confidence: 99%

Can humans perceive the metabolic benefit provided by augmentative exoskeletons?

Medrano

Thomas

Rouse

2022

J NeuroEngineering Rehabil

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“…In the weight-bearing event, when the GRF of the subject with exoskeleton is equal to that without exoskeleton, the net load benefit (NLB) percentage of assisting efficiency of exoskeleton in weight bearing task is proposed as (7), which is based on (6).…”

Section: ) Data Processingmentioning

confidence: 99%

“…The fitting line of the GRF with exoskeleton are lower than those without exoskeleton. According to (7) and (8), plot the relationship between net load benefit (NLB) percentage and net force benefit (NFB) percentage and load levels, as shown in Figs. 9(b) and 9(C).…”

Section: A) Grfsmentioning

confidence: 99%

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Magnetorheological Damper With Variable Displacement Permanent Magnet for Assisting the Transfer of Load in Lower Limb Exoskeleton

Song,

Zhu,

et al. 2024

IEEE Trans. Neural Syst. Rehabil. Eng.

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Magnetorheological (MR) fluid exhibits the ability to modulate its shear state through variations in magnetic field intensity, and is widely used for applications requiring damping. Traditional MR dampers use the current in the coil to adjust the magnetic field strength, but the accumulated heat can cause the magnetic field strength to decay if it works for a long time. In order to deal with this shortcoming, a novel MR damper is proposed in this paper, which is based on a variable displacement permanent magnet to adjust the output resistance torque and applied to an exoskeleton joint for human load transfer assistance. A finite element model is used to determine the size parameters of the magnet and separator, so that the maximum output torque is optimal and the torque is uniformly distributed with the magnet displacement. The MR damper was characterized and calibrated on the experimental bench to make it controllable. The novel design enables the torque mass density of the MR damper to reach 8.83Nmm/g, the torque volume density to reach 48.7N/mm 2 , and has stability for long-term operation. Based on the torque control method proposed, a preliminary human experiment is conducted. The ground reaction force (GRF) data of the subjects is analyzed here, which represents the effect of load transfer to the exoskeleton. Compared with no exoskeleton, the GRF with exoskeleton is significantly reduced: the peak GRF in early stance phase is reduced by 24.14%, and in late stance phase is reduced by

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“…Consequently, exoskeletons may have beneficial implications for recreational users and workers in factory, military, or supply chain environments. In addition, exoskeletons can reduce muscle activation, and thus may reduce joint loading (10)(11)(12)(13), potentially extending the physical capabilities of aging individuals. Rehabilitation-focused exoskeletons may also restore the mobility of people with neuromotor deficits who face weakness and impairments in balance, coordination, and joint mechanics following upper motor neuron disease (e.g.…”

Section: Introductionmentioning

confidence: 99%

The Economic Value of Augmentative Exoskeletons and their Assistance

Medrano¹,

Thomas²,

Margolin³

et al. 2023

Preprint

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<p>Understanding the success of augmentative exoskeletons is critical to their impact on society. Many exoskeletons are developed to address impairments stemming from neuromotor pathology, which provides guidance for understanding their abilities; however, for augmentative exoskeletons that assist able-bodied users, a clear metric of success remains an open question. In this study, we leverage an approach from economics--the Vickrey second-price auction--to quantify the economic value added by lower-limb exoskeletons during uphill walking. In our protocol, participants describe the monetary compensation needed to continue walking uphill for consecutive bouts of two minutes. To incentivize truthful descriptions of participant's “price to walk,” their compensation amounts were provided as bids in Vickrey auctions before each bout. We compared these data across different conditions to determine the marginal value of the exoskeleton weight, assistance, and weight + assistance. Our approach found that the total value of the exoskeleton and its assistance was modest ($3.40/hr, SD: $3.35/hr); while most participants found the assistance itself valuable ($19.76/hr, SD: $19.43/hr), this value was nearly offset by the cost of wearing the exoskeleton weight (-$18.59/hr, SD: $18.28/hr). Our approach and results demonstrate that economic value can be a powerful tool to develop exoskeletons that maximize user benefit. </p>

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Biological Joint Loading and Exoskeleton Design

Cited by 8 publications

References 31 publications

Can humans perceive the metabolic benefit provided by augmentative exoskeletons?

Can humans perceive the metabolic benefit provided by augmentative exoskeletons?

Magnetorheological Damper With Variable Displacement Permanent Magnet for Assisting the Transfer of Load in Lower Limb Exoskeleton

The Economic Value of Augmentative Exoskeletons and their Assistance

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