Inverse dynamics of mechanical multibody systems: An improved algorithm that ensures consistency between kinematics and external forces

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

Inverse dynamics is a technique in which measured kinematics and, possibly, external forces are used to calculate net joint torques in a rigid body linked segment model. However, kinematics and forces are usually not consistent due to incorrect modelling assumptions and measurement errors. This is commonly resolved by introducing ‘residual forces and torques’ which compensate for this problem, but do not exist in reality. In this study a constrained optimization algorithm is proposed that finds the kinematics that are mechanically consistent with measured external forces and mimic the measured kinematics as closely as possible. The algorithm was tested on datasets containing planar kinematics and ground reaction forces obtained during human walking at three velocities (0.8 m/s, 1.25 and 1.8 m/s). Before optimization, the residual force and torque were calculated for a typical example. Both showed substantial values, indicating the necessity of developing a mechanically consistent algorithm. The proposed optimization algorithm converged to a solution in which the residual forces and torques were zero, without changing the ground reaction forces and with only minor changes to the measured kinematics. When using a rigid body approach, our algorithm ensures a consistent description of forces and kinematics, thereby improving the validity of calculated net joint torque and power values.

LanguageEnglish
Article number204575
Pages1-16
Number of pages16
JournalPLoS ONE
Volume13
Issue number9
DOIs
Publication statusPublished - 28 Sep 2018

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kinematics
Biomechanical Phenomena
Kinematics
Torque
torque
Joints
Constrained optimization
Measurement errors
Walking
walking

Cite this

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title = "Inverse dynamics of mechanical multibody systems: An improved algorithm that ensures consistency between kinematics and external forces",
abstract = "Inverse dynamics is a technique in which measured kinematics and, possibly, external forces are used to calculate net joint torques in a rigid body linked segment model. However, kinematics and forces are usually not consistent due to incorrect modelling assumptions and measurement errors. This is commonly resolved by introducing ‘residual forces and torques’ which compensate for this problem, but do not exist in reality. In this study a constrained optimization algorithm is proposed that finds the kinematics that are mechanically consistent with measured external forces and mimic the measured kinematics as closely as possible. The algorithm was tested on datasets containing planar kinematics and ground reaction forces obtained during human walking at three velocities (0.8 m/s, 1.25 and 1.8 m/s). Before optimization, the residual force and torque were calculated for a typical example. Both showed substantial values, indicating the necessity of developing a mechanically consistent algorithm. The proposed optimization algorithm converged to a solution in which the residual forces and torques were zero, without changing the ground reaction forces and with only minor changes to the measured kinematics. When using a rigid body approach, our algorithm ensures a consistent description of forces and kinematics, thereby improving the validity of calculated net joint torque and power values.",
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Inverse dynamics of mechanical multibody systems : An improved algorithm that ensures consistency between kinematics and external forces. / Faber, Herre; Van Soest, Arthur J.; Kistemaker, Dinant A.

In: PLoS ONE, Vol. 13, No. 9, 204575, 28.09.2018, p. 1-16.

Research output: Contribution to JournalArticleAcademicpeer-review

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