### Abstract

Postures are often described and modeled using angles between body segments rather than joint coordinates. Models can be used to predict these angles as a function of anthropometry and postural requirements. Postural representation, however, requires the joint coordinates. The use of conventional forward kinematics to derive joint coordinates from predicted angles may violate task constraints, such as the placement of a hand on a target or a foot on a pedal. Errors arise because the anthropometry or other motion characteristics of a subject, for which the prediction is to be made, may differ from the data from which the prediction model was derived. We describe how to rectify model-predicted postures to exactly satisfy such task constraints. We require that the model used for predicting the angles also produce estimates of the variation in these predictions. We show how to alter the initial angle predictions, with the amount of perturbation at each angle dependent on the accuracy of its estimation, so as to exactly satisfy the joint coordinate constraints. Finally, we show in an empirical example that this correction usually produces better overall predictions of posture than those obtained initially.

Original language | English |
---|---|

Pages (from-to) | 733-736 |

Number of pages | 4 |

Journal | Journal of Biomechanics |

Volume | 32 |

Issue number | 7 |

Early online date | 23 Jun 1999 |

DOIs | |

Publication status | Published - 1 Jul 1999 |

### Keywords

- Optimization
- Postural constraints
- Pseudoinverse

### ASJC Scopus subject areas

- Biophysics
- Orthopedics and Sports Medicine
- Biomedical Engineering
- Rehabilitation

### Cite this

*Journal of Biomechanics*,

*32*(7), 733-736. https://doi.org/10.1016/S0021-9290(99)00046-9

**Rectifying postures reconstructed from joint angles to meet constraints.** / Faraway, Julian J.; Zhang, Xudong; Chaffin, Don B.

Research output: Contribution to journal › Article

*Journal of Biomechanics*, vol. 32, no. 7, pp. 733-736. https://doi.org/10.1016/S0021-9290(99)00046-9

}

TY - JOUR

T1 - Rectifying postures reconstructed from joint angles to meet constraints

AU - Faraway, Julian J.

AU - Zhang, Xudong

AU - Chaffin, Don B.

PY - 1999/7/1

Y1 - 1999/7/1

N2 - Postures are often described and modeled using angles between body segments rather than joint coordinates. Models can be used to predict these angles as a function of anthropometry and postural requirements. Postural representation, however, requires the joint coordinates. The use of conventional forward kinematics to derive joint coordinates from predicted angles may violate task constraints, such as the placement of a hand on a target or a foot on a pedal. Errors arise because the anthropometry or other motion characteristics of a subject, for which the prediction is to be made, may differ from the data from which the prediction model was derived. We describe how to rectify model-predicted postures to exactly satisfy such task constraints. We require that the model used for predicting the angles also produce estimates of the variation in these predictions. We show how to alter the initial angle predictions, with the amount of perturbation at each angle dependent on the accuracy of its estimation, so as to exactly satisfy the joint coordinate constraints. Finally, we show in an empirical example that this correction usually produces better overall predictions of posture than those obtained initially.

AB - Postures are often described and modeled using angles between body segments rather than joint coordinates. Models can be used to predict these angles as a function of anthropometry and postural requirements. Postural representation, however, requires the joint coordinates. The use of conventional forward kinematics to derive joint coordinates from predicted angles may violate task constraints, such as the placement of a hand on a target or a foot on a pedal. Errors arise because the anthropometry or other motion characteristics of a subject, for which the prediction is to be made, may differ from the data from which the prediction model was derived. We describe how to rectify model-predicted postures to exactly satisfy such task constraints. We require that the model used for predicting the angles also produce estimates of the variation in these predictions. We show how to alter the initial angle predictions, with the amount of perturbation at each angle dependent on the accuracy of its estimation, so as to exactly satisfy the joint coordinate constraints. Finally, we show in an empirical example that this correction usually produces better overall predictions of posture than those obtained initially.

KW - Optimization

KW - Postural constraints

KW - Pseudoinverse

UR - http://www.scopus.com/inward/record.url?scp=0032997140&partnerID=8YFLogxK

U2 - 10.1016/S0021-9290(99)00046-9

DO - 10.1016/S0021-9290(99)00046-9

M3 - Article

VL - 32

SP - 733

EP - 736

JO - 5th World Congress of Biomechanics Munich, Germany, 29 July - 4 August 2006

JF - 5th World Congress of Biomechanics Munich, Germany, 29 July - 4 August 2006

SN - 0021-9290

IS - 7

ER -