A Variable Impedance Knee Mechanism for Controlled Stance Flexion During Pathological Gait

Bulea, Thomas C.; Kobetic, Rudi; To, Curtis S.; Audu, Musa L.; Schnellenberger, John R.; Triolo, Ronald J.

doi:10.1109/tmech.2011.2131148

Cited by 43 publications

(28 citation statements)

References 41 publications

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“…We have previously reported design and testing of a variable impedance knee mechanism (VIKM) capable of controlling knee motion [36-38]. The VIKM uses a passive, controllable damper to provide up to 64.5 Nm of torque to resist and control knee motion, with a response time of less than 35 ms.…”

Section: Methodsmentioning

confidence: 99%

“…The purpose of this investigation was to compare stiff legged FNS-driven gait with a new HNP capable of providing stance phase knee motion regulated by a variable impedance knee mechanism (VIKM-HNP) [36-38]. In this study we evaluated the hypothesis that by controlling stance phase knee motion, the VIKM-HNP system can provide a more natural gait compared to FNS systems which retain a stiff knee joint.…”

Section: Introductionmentioning

confidence: 99%

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Stance controlled knee flexion improves stimulation driven walking after spinal cord injury

Bulea

Kobetic

Audu

et al. 2013

Journal of NeuroEngineering and Rehabilitation

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BackgroundFunctional neuromuscular stimulation (FNS) restores walking function after paralysis from spinal cord injury via electrical activation of muscles in a coordinated fashion. Combining FNS with a controllable orthosis to create a hybrid neuroprosthesis (HNP) has the potential to extend walking distance and time by mechanically locking the knee joint during stance to allow knee extensor muscle to rest with stimulation turned off. Recent efforts have focused on creating advanced HNPs which couple joint motion (e.g., hip and knee or knee and ankle) to improve joint coordination during swing phase while maintaining a stiff-leg during stance phase.MethodsThe goal of this study was to investigate the effects of incorporating stance controlled knee flexion during loading response and pre-swing phases on restored gait. Knee control in the HNP was achieved by a specially designed variable impedance knee mechanism (VIKM). One subject with a T7 level spinal cord injury was enrolled and served as his own control in examining two techniques to restore level over-ground walking: FNS-only (which retained a stiff knee during stance) and VIKM-HNP (which allowed controlled knee motion during stance). The stimulation pattern driving the walking motion remained the same for both techniques; the only difference was that knee extensor stimulation was constant during stance with FNS-only and modulated together with the VIKM to control knee motion during stance with VIKM-HNP.ResultsStance phase knee angle was more natural during VIKM-HNP gait while knee hyperextension persisted during stiff-legged FNS-only walking. During loading response phase, vertical ground reaction force was less impulsive and instantaneous gait speed was increased with VIKM-HNP, suggesting that knee flexion assisted in weight transfer to the leading limb. Enhanced knee flexion during pre-swing phase also aided flexion during swing, especially when response to stimulation was compromised.ConclusionsThese results show the potential advantages of incorporating stance controlled knee flexion into a hybrid neuroprosthesis for walking. The addition of such control to FNS driven walking could also enable non-level walking tasks such as uneven terrain, slope navigation and stair descent where controlled knee flexion during weight bearing is critical.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Stance controlled knee flexion improves stimulation driven walking after spinal cord injury

Bulea

Kobetic

Audu

et al. 2013

Journal of NeuroEngineering and Rehabilitation

Self Cite

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“…3). The lower extremity brace was a modified reciprocating gait orthosis (RGO) with the hip reciprocator disengaged, knee drop locks replaced by the four-bar linkage and damper mounted across the knee (the VIKM [21]), and ankles locked in neutral position by ankle-foot orthosis (AFOs). A sensor set and associated electronics for powering the sensors and the VIKM dampers were mounted on the brace.…”

Section: Control System Validationmentioning

confidence: 99%

“…We have previously reported the design and testing of a variable impedance knee mechanism (VIKM) composed of a four bar linkage with a magnetorheological damper [21]. The VIKM provides up to 65 Nm of torque to resist knee motion, with passive resistance less than 4 Nm and a response time of 35 ms.…”

Section: Introductionmentioning

confidence: 99%

Finite State Control of a Variable Impedance Hybrid Neuroprosthesis for Locomotion After Paralysis

Bulea

Kobetic

Audu

et al. 2013

IEEE Trans. Neural Syst. Rehabil. Eng.

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We have previously reported on a novel variable impedance knee mechanism (VIKM). The VIKM was designed as a component of a hybrid neuroprosthesis to regulate knee flexion. The hybrid neuroprosthesis is a device that uses a controllable brace to support the body against collapse while stimulation provides power for movement. The hybrid neuroprosthesis requires a control system to coordinate the actions of the VIKM with the stimulation system; the development and evaluation of such a controller is presented. Brace mounted sensors and a baseline open loop stimulation pattern are utilized as control signals to activate the VIKM during stance phase while simultaneously modulating muscle stimulation in an on-off fashion. The objective is twofold: reduce the amount of stimulation necessary for walking while simultaneously restoring more biologically correct knee motion during stance using the VIKM. Custom designed hardware and software components were developed for controller implementation. The VIKM hybrid neuroprosthesis (VIKM-HNP) was evaluated during walking in one participant with thoracic level spinal cord injury. In comparison to walking with functional neuromuscular stimulation (FNS) alone, the VIKM-HNP restored near normal stance phase knee flexion during loading response and pre-swing phases while decreasing knee extensor stimulation by up to 40%.

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“…Indeed controlling the damping component has proven more beneficial for some applications, particularly in the fields of prosthetics [25], orthotics [26]- [28], and rehabilitation robotics [29] where energy efficiency is less of a consideration and safe human interaction is of prime concern. Damping is controlled by the inclusion of brakes and clutches and the development of such mechanisms is proving to be a fertile field of research [30]- [33].…”

Section: Introductionmentioning

confidence: 99%

Linear Multimodal Actuation Through Discrete Coupling

Leach

Günther

Maheshwari

et al. 2014

IEEE/ASME Trans. Mechatron.

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Due to technological limitations, robot actuators are often designed for specific tasks with narrow performance goals, whereas a wide range of behaviors is necessary for autonomous robots in uncertain complex environments. In an effort to increase the versatility of actuators, we introduce a new concept of multimodal actuation (MMA) that employs dynamic coupling in the form of clutches and brakes to change its mode of operation. The dynamic coupling allows motors and passive elements such as springs to be engaged and disengaged within a single actuator. We apply the concept to a linear series elastic actuator which uses friction brakes controlled online for the dynamic coupling. With this prototype, we are able to demonstrate several modes of operation including stiff position control, series elastic actuation as well as the possibility to store and release energy in a controlled manner for explosive tasks such as jumping. In this paper, we model the proposed concept of actuation and show a systematic performance analysis of the physical prototype that we developed in our laboratory.Index Terms-Brake and clutch, discrete couplings, serieselastic actuator (SEA).

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A Variable Impedance Knee Mechanism for Controlled Stance Flexion During Pathological Gait

Cited by 43 publications

References 41 publications

Stance controlled knee flexion improves stimulation driven walking after spinal cord injury

Stance controlled knee flexion improves stimulation driven walking after spinal cord injury

Finite State Control of a Variable Impedance Hybrid Neuroprosthesis for Locomotion After Paralysis

Linear Multimodal Actuation Through Discrete Coupling

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