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Research Papers

Gravity Balancing of a Human Leg Using an External Orthosis

[+] Author and Article Information
Abbas Fattah

Department of Mechanical Engineering, Isfahan University of Technology, Isfahan 841568111, Iranfattah@cc.iut.ac.ir

Khatereh Hajizadeh

Department of Mechanical Engineering, Isfahan University of Technology, Isfahan 841568111, Iran; Department of Mechanical Engineering, National University of Singapore, Singapore, 117576khatere.hajizade@gmail.com

Sunil K. Agrawal

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

J. Med. Devices 5(1), 011002 (Feb 03, 2011) (10 pages) doi:10.1115/1.4003329 History: Received August 28, 2009; Revised November 12, 2010; Published February 03, 2011; Online February 03, 2011

Gravity balancing is often used in industrial machines to decrease the required actuator efforts during motion. In this paper, we present a new design for gravity balancing of the human leg using an external orthosis. This external orthosis is connected to the human leg on the shank and its other end is fixed to a walking frame. The major issues addressed in this paper are as follows: (i) design for gravity balancing of the human leg and the orthosis, (ii) kinematic compatibility of the human leg and the external orthosis during walking, and (iii) comparison of the joint torque trajectories of the human leg with and without external orthosis. We illustrate feasible 2D and 3D designs of the external orthosis through computer simulations. Our results show that the 3D design has smaller inertia with respect to 2D design, which can be more helpful for typical stroke patients to walk in a balanced position.

Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Description of anatomical planes

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Figure 2

A schematic of a 4DOF human leg and external orthosis

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Figure 3

Geometric and inertia parameters of the human leg and external orthosis

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Figure 4

A schematic of human leg

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Figure 5

The three spring connections to the external orthosis

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Figure 6

Snapshots of animation of the human leg (right) and external orthosis (left)

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Figure 7

Feasible 2DOF: case (a): external orthosis with one spring

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Figure 8

Feasible 2DOF: case (b): external orthosis with two springs

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Figure 9

((a)–(c)) Joint torque trajectories at the hip τ2 and the knee τ3 for the design with one spring (2D case) at different walking speeds: (a) 0.92 m/s, (b) 0.451 m/s, and (c) 0.23 m/s

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Figure 10

Joint trajectories at the hip θ1,θ2 and the knee θ3 for the human leg (3D case) at walking speeds: 0.23 m/s

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Figure 11

((a) and (b)) Joint torque trajectories at a walking speed of 0.92 m/s for design with one and two springs: (a) hip joint τ2 and (b) knee joint τ3

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Figure 12

((a)–(c)) Joint torque trajectories at the hip (τ1 and τ2) and the knee τ3 for the design with three springs (3D case) at different walking speeds: (a) 0.92 m/s, (b) 0.451 m/s, and (c) 0.23 m/s

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Figure 13

Rotation matrix of frame {0} with respect to reference frame {F} about YF axis by angle of θ0

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Figure 14

Rotation matrix of frame {1} with respect to reference frame {0} about x0 axis by angle of θ1

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Figure 15

Rotation matrix of frame {2} with respect to reference frame {1} about z1 axis by angle of θ2

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Figure 16

Rotation matrix of frame {3} with respect to reference frame {1} about z1 axis by angle of θ3

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