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Research Papers

Minimizing Human Tracking Error for Robotic Rehabilitation Device

[+] Author and Article Information
Andrew J. Homich

Department of Mechanical Engineering,
The Pennsylvania State University,
University Park, PA 16802
e-mail: ajh5267@psu.edu

Megan A. Doerzbacher

Department of Mechanical Engineering,
The Pennsylvania State University,
University Park, PA 16802
e-mail: mad5560@psu.edu

Eric L. Tschantz

Department of Mechanical Engineering,
The Pennsylvania State University,
University Park, PA 16802
e-mail: elt5104@psu.edu

Stephen J. Piazza

Department of Kinesiology,
The Pennsylvania State University,
University Park, PA 16802
e-mail: piazza@psu.edu

Everett C. Hills

Department of Physical Medicine
and Rehabilitation,
The Pennsylvania State University,
University Park, PA 16802
e-mail: ech14@psu.edu

Jason Z. Moore

Department of Mechanical Engineering,
The Pennsylvania State University,
University Park, PA 16802
e-mail: jzm14@psu.edu

Manuscript received October 21, 2014; final manuscript received March 20, 2015; published online August 6, 2015. Assoc. Editor: Carl Nelson.

J. Med. Devices 9(4), 041003 (Aug 06, 2015) (8 pages) Paper No: MED-14-1253; doi: 10.1115/1.4030275 History: Received October 21, 2014

This paper explores the design of a novel robotic device for gait training and rehabilitation, a method to estimate a human's orientation within the rehabilitation device, as well as an optimal state space controller to actuate the rehabilitation device. The robotic parallel bars (RPBs) were designed to address the shortcomings of currently available assistive devices. The RPB device moves in response to a human occupant to maintain a constant distance and orientation to the human. To minimize the error in tracking the human, a complementary filter was optimized to estimate the human's orientation within the device using a magnetometer and gyroscope. Experimental measurements of complementary filter performance on a test platform show that the filter estimates orientation with an average error of 0.62 deg over a range of angular velocities from 22.5 deg/s to 180 deg/s. The RPB device response was simulated, and an optimal state space controller was implemented using a linear quadratic regulator (LQR). The controller has an average position error of 14.1 cm and an average orientation error of 14.3 deg when tracking a human, while the simulation predicted an average error of 10.5 cm and 5.6 deg. The achieved level of accuracy in following a human user is sufficiently sensitive for the RPB device to conduct more advanced, realistic gait training and rehabilitation techniques for mobility impaired patients able to safely support their body weight with their legs and arms.

Copyright © 2015 by ASME
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References

Figures

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Fig. 2

Errors between human and device

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Fig. 3

Total position and orientation error between human and device

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Fig. 4

RPB device model for the (a) linear system and (b) rotational system

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Fig. 5

State space controller design

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Fig. 6

Simulated response to linear and angular step input

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Fig. 7

Complementary filter test setup

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Fig. 8

Typical complementary filter experimental results

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Fig. 9

Overhead camera view for controller performance experiments

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Fig. 10

Filter test for (a) full range of complementary filter gains and (b) subrange of complementary filter gains

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Fig. 11

Filter performance results over range of angular velocities

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Fig. 12

Device and simulated device response to linear input of human walking 1.07 m

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Fig. 13

Position error associated with linear input

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Fig. 14

Device and simulated device response to angular input of human spinning 360 deg

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Fig. 15

Average orientation error associated with angular input

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