Photonic Sensors

, Volume 8, Issue 1, pp 1–6 | Cite as

Center of gravity estimation using a reaction board instrumented with fiber Bragg gratings

  • Rui Oliveira
  • Paulo Roriz
  • Manuel B. Marques
  • Orlando Frazão
Open Access


The purpose of the present work is to construct a reaction board based on fiber Bragg gratings (FBGs) that could be used for estimation of the 2D coordinates of the projection of center of gravity (CG) of an object. The apparatus is consisted of a rigid equilateral triangular board mounted on three supports at the vertices, two of which have cantilevers instrumented with FBGs. When an object of known weight is placed on the board, the bending strain of the cantilevers is measured by a proportional wavelength shift of the FBGs. Applying the equilibrium conditions of a rigid body and proper calibration procedures, the wavelength shift is used to estimate the vertical reaction forces and moments of force at the supports and the coordinates of the object’s CG projection on the board. This method can be used on a regular basis to estimate the CG of the human body or objects with complex geometry and density distribution. An example is provided for the estimation of the CG projection coordinates of two orthopaedic femur bone models, one intact, and the other with a hip stem implant encased. The clinical implications of changing the normal CG location by means of a prosthesis have been discussed.


Optical fiber sensors fiber Bragg gratings cantilever center of gravity hip prosthesis 


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Copyright information

© The Author(s) 2017

Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

Authors and Affiliations

  • Rui Oliveira
    • 1
  • Paulo Roriz
    • 1
    • 2
  • Manuel B. Marques
    • 1
    • 3
  • Orlando Frazão
    • 1
  1. 1.INESC TECPortoPortugal
  2. 2.CIDESD-ISMAI-Institute University of Maia (ISMAI)MaiaPortugal
  3. 3.Department of Physics and Astronomy, Faculty of SciencesUniversity of PortoPortoPortugal

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