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Virginia Tech

Estimating Joint Torques on a Biodex System 3 Dynamometer

Abstract

dc:description.abstract

The purpose of this investigation is to propose a method for determining resultant joint moments from a Biodex System 3 isokinetic dynamometer. Previous investigations using a dynamometers determined that measured moments from a dynamometer do not equate to the moment applied by the joint. Using Biodex System 3 dimensions and equipment, the proposed method corrects for gravity, acceleration and inertia moments, and relative angular movement between the dynamometer and the joint axis of rotation for the knee and ankle. The current method includes gravitations correction using a 3rd order polyfit method to a 4°/s passive trial, and inclusion of inertial moments from the dynamometer arm and limb segment. A method is also proposed to correct for gravitational moments, acceleration and inertia moments, and distal joint moments while testing the hip. Previously proposed methods are then compared to the proposed method in isometric and isokinetic exertions. The comparison to a known moment concluded that the results for the isometric exertion are accurate for the proposed method. If the torque measurements from the dynamometer are independent of the velocity, as reported by the manufacturer, the validation of the proposed method for isometric testing holds true for isokinetic as well. The results from isokinetic testing show reasonable results for determining the resultant joint moments. The proposed method can be simplified for clinical or experimental testing. If inertial and acceleration moments are not of concern, than using the propsed gravitational correction will account for the COM (Center of Mass). No additional measurements of the limb segement and dynamometer attachment are needed. The proposed method is recommended for Biodex System 3 isokinetic dynamometer correction in obtaining resultant joint moments at the knee, ankle, and hip.

Degree

thesis:*
Name thesis:degree_name
Master of Science
Level thesis:degree_level
masters
Discipline thesis:degree_discipline
Mechanical Engineering
Department dc:contributor.department
Mechanical Engineering
Grantor dc:publisher
Virginia Tech
Year dc:date.issued
2005

Author and committee

dc:creator, dc:contributor.*
Author dc:creator
  • Herrmann, Christine
Chair dc:contributor.committeechair
  • Madigan, Michael L.
Committee members dc:contributor.committeemember
  • Nussbaum, Maury A.
  • Granata, Kevin P.

Subjects

dc:subject × 3

Rights

dc:rights
Statement dc:rights
  • In Copyright

Identifiers

dc:identifier.*
Dc Identifier Other
etd-07052005-170008
OAI identifier oai:identifier
oai:vtechworks.lib.vt.edu:10919/43529

Chain of custody

source
Harvested from
Virginia Tech
Base URL
vtechworks.lib.vt.edu/oai/request
Last updated
2026-07-22
Source record
OAI-PMH GetRecord
citation

Herrmann, Christine. Estimating Joint Torques on a Biodex System 3 Dynamometer. masters thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/43529