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Research Papers

Design and Evaluation of a Passive Ankle Prosthesis With Powered Push-Off

[+] Author and Article Information
Jacob J. Rice, Joseph M. Schimmels, Shuguang Huang

Department of Mechanical Engineering,
Marquette University,
Milwaukee, WI 53233

Manuscript received March 6, 2015; final manuscript received July 29, 2015; published online November 24, 2015. Assoc. Editor: Byung-Ju Yi.

J. Mechanisms Robotics 8(2), 021012 (Nov 24, 2015) (8 pages) Paper No: JMR-15-1052; doi: 10.1115/1.4031302 History: Received March 06, 2015; Revised July 29, 2015; Accepted August 08, 2015

Below-knee amputation is one of the most frequently performed types of amputation in the United States. This paper describes CamWalk, a novel passive ankle prosthesis that has mechanical behavior similar to that of a natural ankle. CamWalk generates rotational push-off to propel the walker forward using a compliant coupling between two degrees-of-freedom (DOFs) (deflection along the leg and rotation about the ankle). The design closely matches the ankle torque and ankle work characteristics of an average healthy ankle. Simulation results indicate that CamWalk generates 44.5% of the net rotational work performed by a natural healthy ankle when leg deflection is limited to 15 mm. Standard gait analysis of four amputees using CamWalk demonstrated that the device performance ranged from marginally dissipative to significantly active, generating 48.0% of the work performed by their natural ankle.

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Figures

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Fig. 1

Stance phase key positions

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Fig. 2

Natural gait profiles for a healthy natural ankle. Average subject mass: 56.7 kg.

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Fig. 3

Torque–angle curve for a healthy natural ankle. Average subject mass: 56.7 kg.

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Fig. 4

Torque–angle curve for a passive prosthetic ankle. Subject mass: 63.7 kg.

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Fig. 5

Novel 2DOF approach with compliant coupling. Ankle angle and leg deflection are zero at the no-load equilibrium configuration.

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Fig. 6

CamWalk at key stance positions. Springs with dashed lines indicate that they are not providing force. (1) Heel-strike, (2) foot-flat, (3a) heel-off, (3b) heel-off, (4a) toe-off, and (4b) toe-off.

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Fig. 7

CamWalk design parameters. Design parameters are specified in the no-load equilibrium configuration.

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Fig. 8

Compactness envelope for CamWalk

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Fig. 9

Average natural and simulated torque–angle curves

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Fig. 10

CamWalk prototype

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Fig. 11

Shock absorption spring, follower, and cam: (a) side view and (b) trimetric view

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Fig. 12

Cam follower and track

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Fig. 13

Torque–angle curves for the robot test and model simulation

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Fig. 14

Ankle torque–angle curves for CamWalk with early drop timing. Subject 2 mass: 73.5 kg.

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Fig. 15

Ankle torque–angle curves for CamWalk and the amputee's original prosthesis. Subject 4 mass: 88.0 kg.

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