Exoskeleton plantarflexion assistance for elderly

Galle, Samuel; Derave, Wim; Bossuyt, Fransiska M; Calders, Patrick; Malcolm, Philippe; Clercq, Dirk De

doi:10.1016/j.gaitpost.2016.11.040

Cited by 57 publications

(62 citation statements)

References 27 publications

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“…There is mounting evidence that wearable assistive devices that generate power, such as exosuits and exoskeletons, can benefit users during walking, [5, 6, 22], hopping [23–25], load carriage [4, 15] and other locomotor tasks, and that these benefits can be realized for individuals across a range of ages [26] and physical abilities [1–3]. But these benefits are only realized when augmentation power is timed and scaled (in magnitude) appropriately; and this augmentation power is heavily dependent on how power is transmitted from a device to the body via physical interfaces.…”

Section: Discussionmentioning

confidence: 99%

Physical interface dynamics alter how robotic exosuits augment human movement: implications for optimizing wearable assistive devices

Yandell

Quinlivan

Popov

et al. 2017

J NeuroEngineering Rehabil

113

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BackgroundWearable assistive devices have demonstrated the potential to improve mobility outcomes for individuals with disabilities, and to augment healthy human performance; however, these benefits depend on how effectively power is transmitted from the device to the human user. Quantifying and understanding this power transmission is challenging due to complex human-device interface dynamics that occur as biological tissues and physical interface materials deform and displace under load, absorbing and returning power.MethodsHere we introduce a new methodology for quickly estimating interface power dynamics during movement tasks using common motion capture and force measurements, and then apply this method to quantify how a soft robotic ankle exosuit interacts with and transfers power to the human body during walking. We partition exosuit end-effector power (i.e., power output from the device) into power that augments ankle plantarflexion (termed augmentation power) vs. power that goes into deformation and motion of interface materials and underlying soft tissues (termed interface power).ResultsWe provide empirical evidence of how human-exosuit interfaces absorb and return energy, reshaping exosuit-to-human power flow and resulting in three key consequences: (i) During exosuit loading (as applied forces increased), about 55% of exosuit end-effector power was absorbed into the interfaces. (ii) However, during subsequent exosuit unloading (as applied forces decreased) most of the absorbed interface power was returned viscoelastically. Consequently, the majority (about 75%) of exosuit end-effector work over each stride contributed to augmenting ankle plantarflexion. (iii) Ankle augmentation power (and work) was delayed relative to exosuit end-effector power, due to these interface energy absorption and return dynamics.ConclusionsOur findings elucidate the complexities of human-exosuit interface dynamics during transmission of power from assistive devices to the human body, and provide insight into improving the design and control of wearable robots. We conclude that in order to optimize the performance of wearable assistive devices it is important, throughout design and evaluation phases, to account for human-device interface dynamics that affect power transmission and thus human augmentation benefits.Electronic supplementary materialThe online version of this article (doi:10.1186/s12984-017-0247-9) contains supplementary material, which is available to authorized users.

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Section: Discussionmentioning

confidence: 99%

Physical interface dynamics alter how robotic exosuits augment human movement: implications for optimizing wearable assistive devices

Yandell

Quinlivan

Popov

et al. 2017

J NeuroEngineering Rehabil

113

View full text Add to dashboard Cite

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“…Load cells (100 Hz; 210 Series, Richmond Industries Ltd., Reading, United Kingdom) were connected between the orthoses and the pneumatic muscles to measure the force of the pneumatic muscles. Linear displacement sensors (100 Hz; SLS130, Penny&Giles, Christchurch, United Kingdom) were connected between the foot and shank sections of the exoskeletons to measure ankle joint angles [20]. The total weight of one tethered exoskeleton including all sensors was 0.890 kg (0.680 kg for the orthosis, 0.030 kg for the displacement sensor, 0.110 kg for the pneumatic muscle and 0.070 kg for the load cell).…”

Section: Methodsmentioning

confidence: 99%

“…1). Based on a prior calibration with motion capture, ankle joint angle and moment arm of the pneumatic muscles were estimated based on linear displacement [20]. A moving average of positive exoskeleton power with a window of 10 strides was then used as the input for the iterative learning algorithm.…”

Section: Methodsmentioning

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

177

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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“…Another important field of application relates to the augmentation of human capabilities. Herein, exoskeletons are commonly used to reduce the stress and metabolic cost during physically demanding tasks (Zoss et al, 2006;Bosch et al, 2016;Galle et al, 2017;Huysamen et al, 2018) or to prevent falls in the elderly (Giovacchini et al, 2015;Verrusio et al, 2017). Furthermore, as physical and functional losses increase with the aging of the population (e.g., sensory loss, slower reaction time, decreased limb muscle force and power, reduced oxygen consumption), just recently Grimmer et al (2019) emphasized the potential of LLExos to compensate for such losses.…”

Section: Introductionmentioning

confidence: 99%

Does a Passive Unilateral Lower Limb Exoskeleton Affect Human Static and Dynamic Balance Control?

Ringhof

Patzer

Beil

et al. 2019

Front. Sports Act. Living

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Exoskeletons are wearable devices closely coupled to the human, which can interact with the musculoskeletal system, e. g., to augment physical and functional capabilities. A main prerequisite for the development and application of exoskeletons is to investigate the human-exoskeleton interaction, particularly in terms of potential inferences with human motor control. Therefore, the purpose of the present study was to investigate whether a passive unilateral lower limb exoskeleton has an impact on static and dynamic reactive balance control. Eleven healthy subjects (22.9 ± 2.5 years, five females) volunteered for this study and performed three different balance tasks: bipedal standing, single-leg standing, and platform perturbations in single-leg standing. All the balance tasks were conducted with and without a passive unilateral lower limb exoskeleton, while force plates and a motion capture system were used to capture the center of pressure mean sway velocity and the time to stabilization, respectively. Dependent t-tests were separately run for both static balance tests, and a repeated-measure analysis of variance with factors exoskeleton and direction of perturbation was calculated for the dynamic reactive balance task. The exoskeleton did not significantly influence postural sway in bipedal stance. However, in single-leg stance, the mediolateral mean sway velocity of the center of pressure was significantly shorter for the exoskeleton condition. For the dynamic reactive balance task, the participants tended to regain stability less quickly with the exoskeleton, as indicated by a large effect size and longer time to stabilization for all directions of perturbation. In summary, the study showed that the exoskeleton provided some assistive support under static conditions, which however may disappear when sufficient stability is available (bipedal stance). Besides, the exoskeleton tended to impair dynamic reactive balance, potentially by impeding adequate compensatory adjustments. These are important findings with strong implications for the future design and application of exoskeletons, emphasizing the significance of taking into account the mechanisms of human motor control.

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Exoskeleton plantarflexion assistance for elderly

Cited by 57 publications

References 27 publications

Physical interface dynamics alter how robotic exosuits augment human movement: implications for optimizing wearable assistive devices

Physical interface dynamics alter how robotic exosuits augment human movement: implications for optimizing wearable assistive devices

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

Does a Passive Unilateral Lower Limb Exoskeleton Affect Human Static and Dynamic Balance Control?

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