Task-dependent modulation of multi-dimensional human ankle stiffness

2020 ◽  
pp. 41-56
Author(s):  
Hyunglae Lee
Keyword(s):  
Ankle Stiffness ◽  
Human Ankle

Design, Development, and Control of a Fabric-Based Soft Ankle Module to Mimic Human Ankle Stiffness

2019 ◽  
Author(s):  
Sunny Amatya ◽  
Amir Salimi Lafmejani ◽  
Souvik Poddar ◽  
Saivimal Sridar ◽  
Thomas Sugar ◽  
...  
Keyword(s):  
Design Development ◽  
Ankle Stiffness ◽  
Human Ankle ◽  
And Control

Support vector machine identification of a parallel cascade model of human ankle stiffness

2016 ◽  
Vol 10 ◽  
pp. 1359-1371
Author(s):  
Mujahed Aldhaifallah ◽  
David T. Westwick ◽  
K. S. Nisar
Keyword(s):  
Support Vector Machine ◽  
Cascade Model ◽  
Support Vector ◽  
Ankle Stiffness ◽  
Human Ankle

scholarly journals Estimation of the Two Degrees-of-Freedom Time-Varying Impedance of the Human Ankle

2018 ◽  
Vol 12 (1) ◽  
Author(s):  
Evandro Ficanha ◽  
Guilherme Ribeiro ◽  
Lauren Knop ◽  
Mo Rastgaar
Keyword(s):  
Degrees Of Freedom ◽  
Mechanical Impedance ◽  
Heel Strike ◽  
Time Varying ◽  
Two Degrees Of Freedom ◽  
Impedance Modulation ◽  
Ankle Stiffness ◽  
Human Ankle ◽  
Stiffness And Damping ◽  
And Inversion

An understanding of the time-varying mechanical impedance of the ankle during walking is fundamental in the design of active ankle-foot prostheses and lower extremity rehabilitation devices. This paper describes the estimation of the time-varying mechanical impedance of the human ankle in both dorsiflexion–plantarflexion (DP) and inversion–eversion (IE) during walking in a straight line. The impedance was estimated using a two degrees-of-freedom (DOF) vibrating platform and instrumented walkway. The perturbations were applied at eight different axes of rotation combining different amounts of DP and IE rotations of four male subjects. The observed stiffness and damping were low at heel strike, increased during the mid-stance, and decreases at push-off. At heel strike, it was observed that both the damping and stiffness were larger in IE than in DP. The maximum average ankle stiffness was 5.43 N·m/rad/kg at 31% of the stance length (SL) when combining plantarflexion and inversion and the minimum average was 1.14 N·m/rad/kg at 7% of the SL when combining dorsiflexion and eversion. The maximum average ankle damping was 0.080 Nms/rad/kg at 38% of the SL when combining plantarflexion and inversion, and the minimum average was 0.016 Nms/rad/kg at 7% of the SL when combining plantarflexion and eversion. From 23% to 93% of the SL, the largest ankle stiffness and damping occurred during the combination of plantarflexion and inversion or dorsiflexion and eversion. These rotations are the resulting motion of the ankle's subtalar joint, suggesting that the role of this joint and the muscles involved in the ankle rotation are significant in the impedance modulation in both DP and IE during gait.

scholarly journals Development of a Mechatronic Platform and Validation of Methods for Estimating Ankle Stiffness During the Stance Phase of Walking

2013 ◽  
Vol 135 (8) ◽  
Author(s):  
Elliott J. Rouse ◽  
Levi J. Hargrove ◽  
Eric J. Perreault ◽  
Michael A. Peshkin ◽  
Todd A. Kuiken
Keyword(s):  
Mechanical Properties ◽  
Stance Phase ◽  
Testing Machine ◽  
Human Interaction ◽  
Joint Torque ◽  
Average Error ◽  
Prosthetic Foot ◽  
Ankle Impedance ◽  
Ankle Stiffness ◽  
Human Ankle

The mechanical properties of human joints (i.e., impedance) are constantly modulated to precisely govern human interaction with the environment. The estimation of these properties requires the displacement of the joint from its intended motion and a subsequent analysis to determine the relationship between the imposed perturbation and the resultant joint torque. There has been much investigation into the estimation of upper-extremity joint impedance during dynamic activities, yet the estimation of ankle impedance during walking has remained a challenge. This estimation is important for understanding how the mechanical properties of the human ankle are modulated during locomotion, and how those properties can be replicated in artificial prostheses designed to restore natural movement control. Here, we introduce a mechatronic platform designed to address the challenge of estimating the stiffness component of ankle impedance during walking, where stiffness denotes the static component of impedance. The system consists of a single degree of freedom mechatronic platform that is capable of perturbing the ankle during the stance phase of walking and measuring the response torque. Additionally, we estimate the platform's intrinsic inertial impedance using parallel linear filters and present a set of methods for estimating the impedance of the ankle from walking data. The methods were validated by comparing the experimentally determined estimates for the stiffness of a prosthetic foot to those measured from an independent testing machine. The parallel filters accurately estimated the mechatronic platform's inertial impedance, accounting for 96% of the variance, when averaged across channels and trials. Furthermore, our measurement system was found to yield reliable estimates of stiffness, which had an average error of only 5.4% (standard deviation: 0.7%) when measured at three time points within the stance phase of locomotion, and compared to the independently determined stiffness values of the prosthetic foot. The mechatronic system and methods proposed in this study are capable of accurately estimating ankle stiffness during the foot-flat region of stance phase. Future work will focus on the implementation of this validated system in estimating human ankle impedance during the stance phase of walking.

scholarly journals The effects of ankle stiffness on mechanics and energetics of walking with added loads: a prosthetic emulator study

2019 ◽  
Vol 16 (1) ◽  
Author(s):  
Erica A. Hedrick ◽  
Philippe Malcolm ◽  
Jason M. Wilken ◽  
Kota Z. Takahashi
Keyword(s):  
Energy Cost ◽  
Load Condition ◽  
Metabolic Cost ◽  
Load Carriage ◽  
Metabolic Energy ◽  
Additional Load ◽  
Ankle Stiffness ◽  
Human Ankle ◽  
Positive Work ◽  
Load Conditions

Abstract Background The human ankle joint has an influential role in the regulation of the mechanics and energetics of gait. The human ankle can modulate its joint ‘quasi-stiffness’ (ratio of plantarflexion moment to dorsiflexion displacement) in response to various locomotor tasks (e.g., load carriage). However, the direct effect of ankle stiffness on metabolic energy cost during various tasks is not fully understood. The purpose of this study was to determine how net metabolic energy cost was affected by ankle stiffness while walking under different force demands (i.e., with and without additional load). Methods Individuals simulated an amputation by using an immobilizer boot with a robotic ankle-foot prosthesis emulator. The prosthetic emulator was controlled to follow five ankle stiffness conditions, based on literature values of human ankle quasi-stiffness. Individuals walked with these five ankle stiffness settings, with and without carrying additional load of approximately 30% of body mass (i.e., ten total trials). Results Within the range of stiffness we tested, the highest stiffness minimized metabolic cost for both load conditions, including a ~ 3% decrease in metabolic cost for an increase in stiffness of about 0.0480 Nm/deg/kg during normal (no load) walking. Furthermore, the highest stiffness produced the least amount of prosthetic ankle-foot positive work, with a difference of ~ 0.04 J/kg from the highest to lowest stiffness condition. Ipsilateral hip positive work did not significantly change across the no load condition but was minimized at the highest stiffness for the additional load conditions. For the additional load conditions, the hip work followed a similar trend as the metabolic cost, suggesting that reducing positive hip work can lower metabolic cost. Conclusion While ankle stiffness affected the metabolic cost for both load conditions, we found no significant interaction effect between stiffness and load. This may suggest that the importance of the human ankle’s ability to change stiffness during different load carrying tasks may not be driven to minimize metabolic cost. A prosthetic design that can modulate ankle stiffness when transitioning from one locomotor task to another could be valuable, but its importance likely involves factors beyond optimizing metabolic cost.

Identification of intrinsic and reflex contributions to human ankle stiffness dynamics

1997 ◽  
Vol 44 (6) ◽  
pp. 493-504 ◽  
Author(s):  
R.E. Kearney ◽  
R.B. Stein ◽  
L. Parameswaran
Keyword(s):  
Ankle Stiffness ◽  
Human Ankle

Determination of In Vivo Dynamic Human Ankle Stiffness Under External Foot Rotation

2012 ◽  
Author(s):  
Keith D. Button ◽  
Jerrod E. Braman ◽  
Feng Wei ◽  
Roger C. Haut
Keyword(s):  
Injury Risk ◽  
Sports Injuries ◽  
External Rotation ◽  
Surface Interactions ◽  
Ankle Sprains ◽  
Ankle Stiffness ◽  
Human Ankle ◽  
Using Data

Ankle sprains account for 10–15% of all sports injuries [1]. Understanding the conditions that contribute to sports-related ankle sprains can provide useful information to footwear designers to help prevent such injuries. Attempts have been made to create surrogate ankles that mimic ankle properties in order to simulate injury scenarios. In this laboratory, using data from cadaver experiments, Villwock et al. developed such an ankle to assess injury risk due to shoe-surface interface [2]. While this model provides data on shoe-surface interactions, it only takes into account ankle stiffness in rotation. Consequently, the model can only recreate internal-external rotation, not eversion-inversion or plantarflexion-dorsiflexion responses of the human ankle.

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