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Technical Brief

Design and Preliminary Testing of a Pneumatic Muscle-Actuated Transfemoral Prosthesis

[+] Author and Article Information
Molei Wu, Tad Driver, Sai-Kit Wu

The Department of Mechanical Engineering,
The University of Alabama,
Tuscaloosa, AL 35487

Xiangrong Shen

The Department of Mechanical Engineering,
The University of Alabama,
Tuscaloosa, AL 35487
e-mail: xshen@eng.ua.edu

Manuscript received July 31, 2013; final manuscript received February 6, 2014; published online August 19, 2014. Assoc. Editor: Carl A. Nelson.

J. Med. Devices 8(4), 044502 (Aug 19, 2014) (7 pages) Paper No: MED-13-1184; doi: 10.1115/1.4026830 History: Received July 31, 2013; Revised February 06, 2014

Providing powered joint actuation is a major focus of research in the lower-limb prosthesis area. The capability of actively powering the joints enables the prosthesis to meet the energetic requirements of locomotion, and thus provide higher performance in restoring the lost lower-limb functions in comparison with traditional passive prostheses. In this paper, a powered transfemoral (above-knee) prosthesis is presented, in which the knee and ankle are powered with pneumatic muscle actuators. A new variable-radius pulley-based mechanism is utilized, which enables the free adjustment of actuation torque curve to better match the desired torque curve as dictated by the locomotive requirements. Additionally, a spring-return mechanism is also incorporated, which replaces the muscle actuator in the “weak” (less torque-demanding) direction with a set of mechanical springs. With this mechanism, both knee and ankle joints can be powered while maintaining a compact profile of the prosthesis. The design details are presented, and the prosthesis is able to provide sufficient torque for an 85 kg user in various locomotion modes. A prototype of the prosthesis has been fabricated and tested, with the preliminary results indicating that this prosthesis is able to provide a walking gait similar to that of a healthy person.

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References

Winter, D. A., 1991, The Biomechanics and Motor Control of Human Gait: Normal, Elderly and Pathological, 2nd ed., University of Waterloo Press, Waterloo, ON, Canada.
Riener, R., Rabuffetti, M., and Frigo, C., 2002, “Stair Ascent and Descent at Different Inclinations,” Gait Posture, 15, pp. 32–44. [CrossRef] [PubMed]
Waters, R., Perry, J., Antonelli, D., and Hislop, H., 1976, “Energy Cost of Walking Amputees: The Influence of Level of Amputation,” J. Bone Jt. Surg., 58A, pp. 42–46.
Flowers, W. C., and Mann, R. W., 1977, “An Electrohydraulic Knee-Torque Controller for a Prosthesis Simulator,” ASME J. Biomech. Eng., 99(1), pp. 3–8. [CrossRef]
Sup, F., Varol, H. A., Mitchell, J., Withrow, T. J., and Goldfarb, M., 2009, “Preliminary Evaluations of a Self-Contained Anthropomorphic Transfemoral Prosthesis,” IEEE/ASME Trans. Mechatron., 14(6), pp. 667–676. [CrossRef]
Martinez-Villalpando, E. C., and Herr, H., 2009, “Agonist-Antagonist Active Knee Prosthesis: A Preliminary Study in Level-Ground Walking,” J. Rehabil. Res. Dev., 46(3), pp. 361–374. [CrossRef] [PubMed]
Hoover, C. D., Fulk, G. D., and Fite, K. B., 2012, “The Design and Initial Experimental Validation of an Active Myoelectric Transfemoral Prosthesis,” ASME J. Med. Devices, 6(1), p. 011005. [CrossRef]
Sup, F., Bohara, A., and Goldfarb, M., 2008, “Design and Control of a Powered Transfemoral Prosthesis,” Int. J. Rob. Res., 27(2), pp. 263–273. [CrossRef] [PubMed]
Lambrecht, B. G. A., and Kazerooni, H., 2009, “Design of a Semi-Active Knee Prosthesis,” IEEE International Conference on Robotics and Automation (ICRA '09), Kobe, Japan, May 12–17, pp. 639–645. [CrossRef]
Shen, X., and Christ, D., 2011, “Design and Control of Chemo-Muscle: A Liquid-Propellant-Powered Muscle Actuation System,” ASME J. Dyn. Syst., Meas., Control, 133(2), p. 021006. [CrossRef]
Waycaster, G., Wu, S.-K., and Shen, X., 2011, “Design and Control of a Pneumatic Artificial Muscle Actuated Above-Knee Prosthesis,” ASME J. Med. Devices, 5(3), p. 031003. [CrossRef]
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Figures

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Fig. 1

The structure (a) and functioning mechanism (b) of the pneumatic muscle actuator

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Fig. 2

Body-weight-normalized joint torque trajectories for various locomotive modes: (a) knee torque trajectories and (b) ankle torque trajectories. The curves are plotted based on the level-walking data from Winter [1] and the stair ascent/descent data from Riener et al. [2].

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Fig. 3

Schematic of the knee actuation mechanism

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Fig. 4

Schematic of the ankle actuation mechanism. Note that the return spring is incorporated in the prosthetic joint.

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Fig. 5

3D model of the transfemoral prosthesis design

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Fig. 6

The linear spring-based return mechanism for the knee

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Fig. 7

The available torque capacity provided by the spring-return mechanism (solid line), in comparison with the torque requirement (dashed line) for the flexion of the knee

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Fig. 8

The available torque capacity provided by the spring-return mechanism (solid line), in comparison with the torque requirement (dashed line) for the dorsiflexion of the ankle

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Fig. 9

Definition of parameters for the superellipse (a) and the corresponding knee actuation mechanism (b)

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Fig. 10

The available torque capacity provided by the knee actuation mechanism (solid line), in comparison with the torque requirement (dashed line) for the extension of the knee

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Fig. 11

Definition of design parameters for the ankle actuation mechanism

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Fig. 12

The available torque capacity provided by the ankle actuation mechanism (solid line), in comparison with the torque requirement (dashed line) for the plantar-flexion of the ankle

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Fig. 13

Photos of the prosthesis prototype

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Fig. 14

A healthy subject fitted with the prosthesis through an able-body adaptor

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Fig. 15

Definition of the states and triggering conditions

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Fig. 16

Comparison of the trajectories of the biological joints versus the prosthetic joints

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