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RESEARCH PAPERS

Design of a Novel Two Degree-of-Freedom Ankle-Foot Orthosis

[+] Author and Article Information
Abhishek Agrawal

Mechanical Engineering Department, University of Delaware, Newark, Delaware 19716agrawala@me.udel.edu

Vivek Sangwan

Mechanical Engineering Department, University of Delaware, Newark, Delaware 19716sangwan@udel.edu

Sai K. Banala

Mechanical Engineering Department, University of Delaware, Newark, Delaware 19716sai@udel.edu

Sunil K. Agrawal

Mechanical Engineering Department, University of Delaware, Newark, Delaware 19716agrawal@udel.edu

Stuart A. Binder-Macleod

Department of Physical Therapy, University of Delaware, Newark, Delaware 19716sbinder@udel.edu

J. Mech. Des 129(11), 1137-1143 (Dec 04, 2006) (7 pages) doi:10.1115/1.2771231 History: Received May 10, 2005; Revised December 04, 2006

An ankle-foot orthosis (AFO) is commonly used to help subjects with weakness of ankle dorsiflexor muscles due to peripheral or central nervous system disorders. Both these disorders are due to the weakness of the tibialis anterior muscle, which results in the lack of dorsiflexion assist moment. The deformity and muscle, weakness of one joint in the lower extremity influences the stability of the adjacent joints, thereby requiring compensatory adaptations. We present an innovative ankle-foot orthosis (AFO). The prototype AFO would introduce greater functionality over currently marketed devices by means of its pronation-supination degree of freedom in addition to flexion/extension. This orthosis can be used to measure joint forces and moments applied by the human at both joints. In the future, by incorporation of actuators in the device, it will be used as a training device to restore a normal walking pattern.

FIGURES IN THIS ARTICLE
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Copyright © 2007 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Orientations of D/P joint axis (Z1) and P/S joint axis (Z2) and their projection angles (7-8)

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Figure 2

Assembled AFO with the shank and the foot brace. It comprises the three links corresponding to the three segments of the human foot.

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Figure 3

A 3D AutoCAD drawing of the AFO fabricated at the University of Delaware. Blocks labeled A and B are used to orient the joint axes.

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Figure 4

Free body diagram of the human and machine parts of the ankle and the shank. Oval and bony bodies represent the human segments and the rectangular shaped bodies represent the machine segments. Forces and torques in circles are the sensor forces and torques.

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Figure 5

Orientations of the D/P and P/S frames. This picture is representative of only the orientations of the frame and not the locations. The frames are placed at the actual joint in the human foot.

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Figure 6

The D/P (θ1) and P/S (θ2) angle movements during the motion about the D/P joint. There is some movement about the P/S axis but is small as compared to the D/P movement.

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Figure 7

The forces and moments applied by the subject about the D/P joint during the motion about the D/P joint

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Figure 8

The forces and moments applied by the subject about the P/S joint during the motion about the D/P joint

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Figure 9

The D/P (θ1) and P/S (θ2) angle movements during the motion about the P/S joint. It is difficult for a subject to obtain a pure P/S rotation, but still we can see that the P/S motion here is much more pronounced and the D/P motion is much less as compared to the previous case.

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Figure 10

The forces and moments applied by the subject about the D/P joint during the motion about the P/S joint

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Figure 11

The forces and moments applied by the subject about the P/S joint during the motion about the P/S joint

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