Delayed Output Feedback Control for Gait Assistance With a Robotic Hip Exoskeleton

Lim, Byeonghwa; Lee, Jusuk; Jang, Junwon; Kim, Kyungrock; Park, Young Jin; Seo, Keehong; Shim, Youngbo

doi:10.1109/tro.2019.2913318

Cited by 74 publications

(49 citation statements)

References 23 publications

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“…With capable devices, optimization, and training, exoskeletons can provide very large improvements in locomotor performance. Whole-leg assistance reduced the metabolic cost of walking by 50% relative to walking with no torque, a substantial improvement over the state-of-the-art (17% -24%) (12,14,17)) . This corresponded to a 37% reduction relative to walking with no exoskeleton, nearly double the justnoticeable difference in metabolic cost (20%) (20), indicating that participants could feel the reduction in effort compared to walking normally.…”

Section: Discussionmentioning

confidence: 89%

“…Exoskeletons have improved walking by reducing metabolic cost, but larger improvements may be necessary for widespread adoption of exoskeleton products. Reductions in metabolic cost have been demonstrated from assisting one or two joints (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19), with the largest metabolic cost reduction being around 18% relative to walking in no exoskeleton (14,17) and 24% relative to walking in an exoskeleton with no torques applied (12). Despite demonstrated improvements, exoskeletons are in a nascent stage of commercial development, and widespread adoption has not yet occurred (6).…”

Section: Introductionmentioning

confidence: 99%

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Comparing optimized exoskeleton assistance of the hip, knee, and ankle in single and multi-joint configurations

Franks

Bryan

Martin

et al. 2021

Preprint

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Exoskeletons that assist the hip, knee, and ankle joints have begun to improve human mobility, particularly by reducing the metabolic cost of walking. However, direct comparisons of optimal assistance of these joints, or their combinations, have not yet been possible. Assisting multiple joints may be more beneficial than the sum of individual effects, because muscles often span multiple joints, or less effective, because single-joint assistance can indirectly aid other joints. In this study, we used a hip-knee-ankle exoskeleton emulator paired with human-in-the-loop optimization to find single-joint, two-joint, and whole-leg assistance that maximally reduced the metabolic cost of walking for three participants. Hip-only and ankle-only assistance reduced the metabolic cost of walking by 26% and 30% relative to walking in the device unassisted, confirming that both joints are good targets for assistance. Knee-only assistance reduced the metabolic cost of walking by 13%, demonstrating that effective knee assistance is possible. Two-joint assistance reduced the metabolic cost of walking by between 34% and 42%, with the largest improvements coming from hip-ankle assistance. Assisting all three joints reduced the metabolic cost of walking by 50%, showing that at least half of the metabolic energy expended during walking can be saved through exoskeleton assistance. Changes in kinematics and muscle activity indicate that single-joint assistance indirectly assisted muscles at other joints, such that the improvement from whole-leg assistance was smaller than the sum of its single-joint parts. Exoskeletons can assist the entire limb for maximum effect, but a single well-chosen joint can be more efficient when considering additional factors such as weight and cost.

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Section: Discussionmentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Comparing optimized exoskeleton assistance of the hip, knee, and ankle in single and multi-joint configurations

Franks

Bryan

Martin

et al. 2021

Preprint

View full text Add to dashboard Cite

show abstract

“…Seventeen publications presented improved human walking and/or running economy using an exoskeleton versus without using a device during preferred levelground conditions: twelve exoskeletons improved walking economy [11][12][13][25][26][27][28][29][30][31][32][33], four improved running economy [14,15,17,18], and one improved both walking and running economy [16] versus using no device ( Fig. 2).…”

Section: Exoskeleton User Performance: Insights and Trendsmentioning

confidence: 99%

The exoskeleton expansion: improving walking and running economy

Sawicki

Beck

Kang

et al. 2020

J NeuroEngineering Rehabil

278

192

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Since the early 2000s, researchers have been trying to develop lower-limb exoskeletons that augment human mobility by reducing the metabolic cost of walking and running versus without a device. In 2013, researchers finally broke this 'metabolic cost barrier'. We analyzed the literature through December 2019, and identified 23 studies that demonstrate exoskeleton designs that improved human walking and running economy beyond capable without a device. Here, we reviewed these studies and highlighted key innovations and techniques that enabled these devices to surpass the metabolic cost barrier and steadily improve user walking and running economy from 2013 to nearly 2020. These studies include, physiologically-informed targeting of lower-limb joints; use of off-board actuators to rapidly prototype exoskeleton controllers; mechatronic designs of both active and passive systems; and a renewed focus on human-exoskeleton interface design. Lastly, we highlight emerging trends that we anticipate will further augment wearable-device performance and pose the next grand challenges facing exoskeleton technology for augmenting human mobility.

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“…These experiments suggest that savings of > = 30% for bilateral ankle assistance with optimized torque profiles may be possible for a portable system if the cost of carrying the device and its actuators can be minimized. These ankle-based and powered lower-limb exoskeleton systems targeting other joints [8,9] accomplish the goal of reducing metabolic cost by transferring net mechanical energy to the user. Alternatively, our research has shown that it is possible to use an unpowered, passive-elastic ankle exoskeleton to reduce the metabolic cost of walking by 7.2% while delivering no net mechanical work [10].…”

Section: Introductionmentioning

confidence: 99%

Impact of elastic ankle exoskeleton stiffness on neuromechanics and energetics of human walking across multiple speeds

Nuckols

Sawicki

2020

J NeuroEngineering Rehabil

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Background: Elastic ankle exoskeletons with intermediate stiffness springs in parallel with the human plantarflexors can reduce the metabolic cost of walking by~7% at 1.25 m s − 1. In a move toward 'real-world' application, we examined whether the unpowered approach has metabolic benefit across a range of walking speeds, and if so, whether the optimal exoskeleton stiffness was speed dependent. We hypothesized that, for any walking speed, there would be an optimal ankle exoskeleton stiffness-not too compliant and not too stiff-that minimizes the user's metabolic cost. In addition, we expected the optimal stiffness to increase with walking speed. Methods: Eleven participants walked on a level treadmill at 1.25, 1.50, and 1.75 m s − 1 while we used a state-of-theart exoskeleton emulator to apply bilateral ankle exoskeleton assistance at five controlled rotational stiffnesses (k exo = 0, 50, 100, 150, 250 Nm rad − 1). We measured metabolic cost, lower-limb joint mechanics, and EMG of muscles crossing the ankle, knee, and hip. Results: Metabolic cost was significantly reduced at the lowest exoskeleton stiffness (50 Nm rad − 1) for assisted walking at both 1.25 (4.2%; p = 0.0162) and 1.75 m s − 1 (4.7%; p = 0.0045). At these speeds, the metabolically optimal exoskeleton stiffness provided peak assistive torques of~0.20 Nm kg − 1 that resulted in reduced biological ankle moment of~12% and reduced soleus muscle activity of~10%. We found no stiffness that could reduce the metabolic cost of walking at 1.5 m s − 1. Across all speeds, the non-weighted sum of soleus and tibialis anterior activation rate explained the change in metabolic rate due to exoskeleton assistance (p < 0.05; R 2 > 0.56). Conclusions: Elastic ankle exoskeletons with low rotational stiffness reduce users' metabolic cost of walking at slow and fast but not intermediate walking speed. The relationship between the non-weighted sum of soleus and tibialis activation rate and metabolic cost (R 2 > 0.56) indicates that muscle activation may drive metabolic demand. Future work using simulations and ultrasound imaging will get 'under the skin' and examine the interaction between exoskeleton stiffness and plantarflexor muscle dynamics to better inform stiffness selection in human-machine systems.

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Delayed Output Feedback Control for Gait Assistance With a Robotic Hip Exoskeleton

Cited by 74 publications

References 23 publications

Comparing optimized exoskeleton assistance of the hip, knee, and ankle in single and multi-joint configurations

Comparing optimized exoskeleton assistance of the hip, knee, and ankle in single and multi-joint configurations

The exoskeleton expansion: improving walking and running economy

Impact of elastic ankle exoskeleton stiffness on neuromechanics and energetics of human walking across multiple speeds

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