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Journal of Robotics
Volume 2010, Article ID 465618, 8 pages
Research Article

Estimating Ground Inclination Using Strain Sensors with Fourier Series Representation

Intelligent System Laboratory, IDE Department, Halmstad University, Box 823, 301 18 Halmstad, Sweden

Received 1 November 2009; Accepted 25 January 2010

Academic Editor: Noriyasu Homma

Copyright © 2010 Wolfgang Svensson and Ulf Holmberg. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


An embedded measurement system for foot orthosis during gait is proposed. Strain gauge sensors were mounted on a foot orthosis to give information about strain in the sagittal plane. The ankle angle of the orthosis was fixed and strain characteristics were therefore changed when walking on slopes. With a Fourier series representation of the strain during a gait cycle, ground angle at different walking speeds and inclinations could be estimated with similar accuracy as previous studies using kinematically based estimators. Furthermore, if the angle of the mechanical foot ankle was changed, the sensing technique still could estimate ground angle without need for recalibration as opposed to kinematical sensors. This indicates that embedded strain sensors can be used for online control of future orthoses with inclination adaptation. Also, there would be no need to recalibrate the sensing system when changing shoes with different heel heights.