Technical Brief

An Adjustable Single Degree-of-Freedom System to Guide Natural Walking Movement for Rehabilitation

[+] Author and Article Information
Brandon Y. Tsuge

Department of Mechanical and Aerospace Engineering,
University of California–Irvine,
Irvine, CA 92697
e-mail: btsuge@uci.edu

J. Michael McCarthy

Fellow ASME
Robotics and Automation Laboratory,
Department of Mechanical and Aerospace Engineering,
University of California–Irvine,
Irvine, CA 92697
e-mail: jmmccart@uci.edu

1Corresponding author.

Manuscript received September 4, 2015; final manuscript received March 9, 2016; published online August 5, 2016. Assoc. Editor: Rita M. Patterson.

J. Med. Devices 10(4), 044501 (Aug 05, 2016) (6 pages) Paper No: MED-15-1252; doi: 10.1115/1.4033329 History: Received September 04, 2015; Revised March 09, 2016

This paper presents a linkage system designed to guide a natural ankle trajectory with the corresponding foot orientation. A six-bar linkage was designed to coordinate the joint angles of an RR chain (R denotes a revolute or hinged joint) that models the leg to achieve the desired ankle trajectory. The design is shown to be adjustable to meet a range of trajectories obtained in an individual's normal gait. Control of the foot position is obtained using a cam-driven parallel chain that has the same input as the six-bar linkage. The design of the linkage was carried out using linkage synthesis theory and optimization methods. The result is a one degree-of-freedom system that guides a natural walking movement of the leg and foot. A solid model of the complete device is presented. The results of this research provide a procedure that focuses on the kinematics and mechanical design of a device named the UCI gait mechanism.

Copyright © 2016 by ASME
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Fig. 1

Motion caption setup with attached marker locations for walking on a treadmill

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Fig. 2

Ankle trajectories obtained from the Vincon MX motion capture system in the global frame

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Fig. 3

Ankle trajectories transformed to a coordinate system fixed at the user's hip joint

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Fig. 4

Stephenson III six-bar linkage with a single displacement

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Fig. 5

Ankle trajectory of a single gait cycle relative to the hip joint, set of 60 precision points derived from a B-spline for the optimization problem, and set of seven precision points derived from a B-spline for homotopy continuation. Precision points derived from B-spine fall within the original ankle trajectory.

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Fig. 6

Optimized walking linkage solution found with design refinement with the hip joint at the origin

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Fig. 7

The foot orientation is controlled by a cam-driven parallelogram linkage. The hip joint is at B, the knee joint is at F, and the ankle joint is at P.

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Fig. 8

Cam profile used to actuate the slider crank mechanism

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Fig. 9

Solid model of the assembly of the six-bar linkage that guides the ankle trajectory with the cam-driven parallelogram linkage that controls the foot orientation

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Fig. 10

An adjustment to joint A introduces a variation of the ankle trajectory between two extremes. (a) Six-bar linkage trajectory with the fixed pivot, A, set to Aupper. (b) Six-bar linkage trajectory with the fixed pivot, A, set to Alower.

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Fig. 11

Solid model of the UCI gait mechanism

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Fig. 12

A solid model of the six-bar linkage for the ankle trajectory obtained from homotopy directed optimization with design refinement

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Fig. 13

Solid model of the slider–crank mechanism that is actuated by a cam

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Fig. 14

Solid model of 12 poses of the walking linkage throughout the gait cycle

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Fig. 15

Solid model of the foot bracket with slotted holes for straps that will secure the user's foot in place




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