Analysis of a Periodic Force Applied to the Trunk to Assist Walking Gait

Bhat, Sandesh; Cherangara, Susheelkumar; Olson, Jason; Redkar, Sangram; Sugar, Thomas G.

doi:10.1109/wearracon.2019.8719396

Cited by 3 publications

(9 citation statements)

References 13 publications

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“…The load cell was mounted at the attachment point with the participant to avoid underestimating or overestimating the applied forces due to oscillating mass from the tether components (elastic element or mechanical fuse). Certain cable robot studies use a similar configuration [21], [23], [39], and others appear to position load cells away from the participant [24], [25], [28] or estimate the forces based on the elongation of a spring [22]. The control station consists of an input-output interface (HuMoTech) and a real-time computer (SpeedGoat, Liebefeld, Switzerland) that runs a controller in Simulink (MathWorks, Data 1).…”

Section: B Sensing and Controlsmentioning

confidence: 99%

“…Simple models [13] and experiments with exoskeletons [7], [8], [30]- [32] show that actuation parameters such as the timing of force profiles can affect the impact of wearable robots. Differences in reductions in metabolic cost between studies with tethers that apply constant forces [20], [21] and tethers that apply cyclic forces once per step [28] or once per stride [29] confirm that assistance timing might also be important when using linear forces at the COM. Although passive systems have the benefit of being convenient to use (not requiring electromechanical hardware), a limitation of the existing studies with passive systems designed to produce cyclic forces is that they could not rigorously control the timing or other actuation parameters.…”

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confidence: 97%

“…For more information, see https://creativecommons.org/licenses/by/4.0/ cost [27], which could be useful for exercise therapy. Bhat et al [28] conducted experiments with relatively short and stiff tethers attached to a fixed anchor to elicit cyclic force profiles within every step as a result of small forward and backward movements on the treadmill. They found smaller reductions in metabolic cost compared to studies that use longer and less stiff tethers that were designed to maintain forces at a constant level [20], [21].…”

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confidence: 99%

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A System for Simple Robotic Walking Assistance With Linear Impulses at the Center of Mass

Gonabadi

Antonellis

Malcolm

2020

IEEE Trans. Neural Syst. Rehabil. Eng.

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Walking can be simplified as an inverted pendulum motion where both legs generate linear impulses to redirect the center of mass (COM) into every step. In this work, we describe a system to assist walking in a simpler way than exoskeletons by providing linear impulses directly at the COM instead of providing torques at the joints. We developed a novel waist end-effector and highlevel controller for an existing cable-robot. The controller allows for the application of cyclic horizontal force profiles with desired magnitudes, timings, and durations based on detection of the step timing. By selecting a lightweight rubber series elastic element with optimal stiffness and carefully tuning the gains of the closed-loop proportionalintegral-derivative (PID) controller in a number of singlesubject experiments, we were able to reduce the within-step root mean square error between desired and actual forces up to 1.21% of body weight. This level of error is similar or lower compared to the performance of other robotic tethers designed to provide variable or constant forces at the COM. The system can produce force profiles with peaks of up to 15 ± 2% of body weight within a root mean square error (RMSE) of 2.5% body weight. This system could be used to assist patient populations that require levels of assistance that are greater than current exoskeletons and in a way that does not make the user rely on vertical support. Index Terms-Aiding force, cable robotics, center of mass (COM), rehabilitation, walking. I. INTRODUCTION T HE field of wearable robots for assisting walking has witnessed an evolution from advanced, sophisticated devices that assist multiple joints [1]-[3] towards a greater focus on single-joint exoskeletons [4]-[9] and elegant, simple Manuscript

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Section: B Sensing and Controlsmentioning

confidence: 99%

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confidence: 97%

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confidence: 99%

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A System for Simple Robotic Walking Assistance With Linear Impulses at the Center of Mass

Gonabadi

Antonellis

Malcolm

2020

IEEE Trans. Neural Syst. Rehabil. Eng.

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Section: Introductionmentioning

confidence: 99%

“…There is increasing interest in devices that can apply such nonconstant force profiles during specific phases of the gait cycle ( 5 , 6 ). Bhat et al ( 5 ) used stiff tethers to elicit cyclic force profiles from the back-and-forth movements on a treadmill. They found smaller metabolic rate reductions than those for constant forces ( 4 , 7 ), which suggests that their force profiles a suboptimal.…”

Section: Introductionmentioning

confidence: 99%

Metabolically efficient walking assistance using optimized timed forces at the waist

et al. 2022

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The metabolic rate of walking can be reduced by applying a constant forward force at the center of mass. It has been shown that the metabolically optimal constant force magnitude minimizes propulsion ground reaction force at the expense of increased braking. This led to the hypothesis that selectively assisting propulsion could lead to greater benefits. We used a robotic waist tether to evaluate the effects of forward forces with different timings and magnitudes. Here, we show that it is possible to reduce the metabolic rate of healthy participants by 48% with a greater efficiency ratio of metabolic cost reduction per unit of net aiding work compared with other assistive robots. This result was obtained using a sinusoidal force profile with peak timing during the middle of the double support. The same timing could also reduce the metabolic rate in patients with peripheral artery disease. A model explains that the optimal force profile accelerates the center of mass into the inverted pendulum movement during single support. Contrary to the hypothesis, the optimal force timing did not entirely coincide with propulsion. Within the field of wearable robotics, there is a trend to use devices to mimic biological torque or force profiles. Such bioinspired actuation can have relevant benefits; however, our results demonstrate that this is not necessarily optimal for reducing metabolic rate.

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Neuromechanical adjustments when walking with an aiding or hindering horizontal force

et al. 2019

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Analysis of a Periodic Force Applied to the Trunk to Assist Walking Gait

Cited by 3 publications

References 13 publications

A System for Simple Robotic Walking Assistance With Linear Impulses at the Center of Mass

A System for Simple Robotic Walking Assistance With Linear Impulses at the Center of Mass

Metabolically efficient walking assistance using optimized timed forces at the waist

Neuromechanical adjustments when walking with an aiding or hindering horizontal force

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