Experimental comparison of torque control methods on an ankle exoskeleton during human walking

Zhang, Juanjuan; Cheah, Chien Chern; Collins, Susan M.

doi:10.1109/icra.2015.7139980

Cited by 102 publications

(132 citation statements)

References 18 publications

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“…Rapidly decreasing torque during the plantarflexion phase of the BiOM ® T2 emulation proved challenging for this simple proportional control scheme, so desired ankle torque was adjusted with an iteratively learned torque ( τ a,lrn ) to compensate for steady-state errors (inspired by [13]).…”

Section: Methodsmentioning

confidence: 99%

Informing ankle-foot prosthesis prescription through haptic emulation of candidate devices

Caputo

Adamczyk

Collins

2015

2015 IEEE International Conference on Robotics and Automation (ICRA)

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Robotic prostheses can improve walking performance for amputees, but prescription of these devices has been hindered by their high cost and uncertainty about the degree to which individuals will benefit. The typical prescription process cannot well predict how an individual will respond to a device they have never used because it bases decisions on subjective assessment of an individual’s current activity level. We propose a new approach in which individuals ‘test drive’ candidate devices using a prosthesis emulator while their walking performance is quantitatively assessed and results are distilled to inform prescription. In this system, prosthesis behavior is controlled by software rather than mechanical implementation, so users can quickly experience a broad range of devices. To test the viability of the approach, we developed a prototype emulator and assessment protocol, leveraging hardware and methods we previously developed for basic science experiments. We demonstrated emulations across the spectrum of commercially available prostheses, including traditional (e.g. SACH), dynamic-elastic (e.g. FlexFoot), and powered robotic (e.g. BiOM® T2) prostheses. Emulations exhibited low error with respect to reference data and provided subjectively convincing representations of each device. We demonstrated an assessment protocol that differentiated device classes for each individual based on quantitative performance metrics, providing feedback that could be used to make objective, personalized device prescriptions.

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Section: Methodsmentioning

confidence: 99%

Informing ankle-foot prosthesis prescription through haptic emulation of candidate devices

Caputo

Adamczyk

Collins

2015

2015 IEEE International Conference on Robotics and Automation (ICRA)

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“…During walking trials, an additional time-based iterative learning term was added, which provided feed-forward compensation of torque errors that tended to occur at the same time each step. This method is described in detail in [24].…”

Section: B Controlmentioning

confidence: 99%

“…A tethered emulator approach [20][21][22][23] decouples the problems of discovering desirable prosthesis functionality from the challenges of developing fully autonomous systems. Powerful off-board motors and controllers are connected to lightweight instrumented end-effectors via flexible tethers, resulting in low worn mass and high-fidelity torque control [20,21,24]. Such systems can be used to haptically render virtual prostheses to human users, facilitating the discovery of novel device behaviors [25] that can then be embedded in separate autonomous designs.…”

Section: Introductionmentioning

confidence: 99%

An ankle-foot prosthesis emulator with control of plantarflexion and inversion-eversion torque

Collins

Kim

Chen

et al. 2015

2015 IEEE International Conference on Robotics and Automation (ICRA)

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Ankle inversion-eversion compliance is an important feature of conventional prosthetic feet, and control of inversion, or roll, in robotic prostheses could improve balance for people with amputation. We designed a tethered ankle-foot prosthesis with two independently-actuated toes that are coordinated to provide plantarflexion and inversion-eversion torques. This configuration allows a simple lightweight structure with a total mass of 0.72 kg. Strain gages on the toes measure torque with less than 2.7% RMS error, while compliance in the Bowden cable tether provides series elasticity. Benchtop tests demonstrated a 90% rise time of less than 33 ms and peak torques of 180 N·m in plantarflexion and ±30 N·m in inversion-eversion. The phase-limited closedloop torque bandwidth is 20 Hz with a 90 N·m amplitude chirp in plantarflexion, and 24 Hz with a 20 N·m amplitude chirp in inversion-eversion. The system has low sensitivity to toe position disturbances at frequencies of up to 18 Hz. Walking trials with five values of constant inversion-eversion torque demonstrated RMS torque tracking errors of less than 3.7% in plantarflexion and less than 5.9% in inversion-eversion. These properties make the platform suitable for haptic rendering of virtual devices in experiments with humans, which may reveal strategies for improving balance or allow controlled comparisons of conventional prosthesis features. A similar morphology may be effective for autonomous devices.

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“…A value of of 0.5 was found to provide a reasonable learning rate, for which the learned friction compensation profile was updated such that a new learned behavior was fully incorporated in approximately 10 seconds. Similar iterative learning methods have been successful in wearable robotics in the presence of cable frictional losses [15].…”

Section: Stance Phase Torquementioning

confidence: 99%

Development and Evaluation of a Powered Artificial Gastrocnemius for Transtibial Amputee Gait

Eilenberg

Kuan

Herr

2018

Journal of Robotics

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Existing robotic transtibial prostheses provide only ankle joint actuation and do not restore biarticular function of the gastrocnemius muscle. This paper presents the first powered biarticular transtibial prosthesis, which is a combination of a commercial powered ankle-foot prosthesis and a motorized robotic knee orthosis. The orthosis is controlled to emulate the human gastrocnemius based on neuromuscular models of matched nonamputees. Together with the ankle-foot prosthesis, the devices provide biarticular actuation. We evaluate differences between this biarticular condition and a monoarticular condition with the orthosis behaving as a free-joint. Six participants with transtibial amputation walk with the prosthesis on a treadmill while motion, force, and metabolic data are collected and analyzed for differences between conditions. The biarticular prosthesis reduces affectedside biological knee flexion moment impulse and hip positive work during late-stance knee flexion, compared to the monoarticular condition. The data do not support our hypothesis that metabolism decreases for all participants, but some participants demonstrate large metabolic reductions with the biarticular condition. These preliminary results suggest that a powered artificial gastrocnemius may be capable of providing large metabolic reductions compared to a monoarticular prosthesis, but further study is warranted to determine an appropriate controller for achieving more consistent metabolic benefits.

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Experimental comparison of torque control methods on an ankle exoskeleton during human walking

Cited by 102 publications

References 18 publications

Informing ankle-foot prosthesis prescription through haptic emulation of candidate devices

Informing ankle-foot prosthesis prescription through haptic emulation of candidate devices

An ankle-foot prosthesis emulator with control of plantarflexion and inversion-eversion torque

Development and Evaluation of a Powered Artificial Gastrocnemius for Transtibial Amputee Gait

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