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Exploring Optimal Objective Function Weightings to Predict Lifting Postures Under Unfatigued and Fatigued States
Justin B Davidson1, Joshua G A Cashaback2, Steven L Fischer1
1University of Waterloo, ON, Canada.
Human Factors
|June 2, 2022
Summary
Digital human models (DHMs) can predict lifting postures. Minimizing discomfort in objective functions accurately predicted postures, regardless of fatigue state, for better lifting posture prediction.
Area of Science:
- Ergonomics and Biomechanics
- Human-Computer Interaction
- Occupational Safety
Background:
- Predicting human postures is crucial for ergonomics and injury prevention.
- Fatigue significantly influences biomechanical responses and lifting postures.
- Digital Human Models (DHMs) offer a potential tool for simulating and predicting these postures.
Purpose of the Study:
- To investigate if optimal objective function weightings in a DHM change for predicting lifting postures under unfatigued and fatigued conditions.
- To assess the impact of fatigue on the accuracy of DHM-predicted lifting postures.
- To determine if modifying DHM objective function weightings can enhance posture prediction accuracy in different physiological states.
Main Methods:
- Utilized a multi-objective optimization-based DHM to predict origin and destination lifting postures for ten avatars.
- Employed response surface methodology to identify optimal objective function weightings by minimizing the root mean squared error between predicted and measured postures.
- Compared resultant weightings across different lifting postures and fatigue states.
Main Results:
- Objective function weightings for discomfort and joint torque were influenced by lifting posture and fatigue state.
- Weighting the discomfort objective function alone demonstrated good generalization across various postures and fatigue states.
- Sufficiently large post-hoc differences between fatigue states and lifting postures were not detected.
Conclusions:
- Minimizing the discomfort objective function provided optimal prediction of lifting postures, irrespective of the user's fatigue state.
- While discomfort minimization is effective for unfatigued states, further research is needed to refine DHM weightings for fatigued states.
- The study highlights the importance of considering physiological states in biomechanical modeling for accurate posture prediction.
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