| 1. |
- Brolin, Karin, 1974, et al.
(författare)
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Towards omni-directional active human body models
- 2016
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Ingår i: 6th International Symposium on Human Modeling and Simulation in Automotive Engineering, Heidelberg, GERMANY, October 20-21.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 2. |
- Brynskog, Erik, 1989, et al.
(författare)
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Population Variance in Pelvic Response to Lateral Impacts - A Global Sensitivity Analysis
- 2022
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Ingår i: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI. - 2235-3151. ; 2022-September, s. 173-196
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Konferensbidrag (refereegranskat)abstract
- Pelvic fracture remains the third most common moderate to severe injury in motor vehicle crashes, and the dominating lower extremity injury in lateral impacts. An essential tool for analysis of injury, and real-world occupant protection, are finite element human body models. However, today's state-of-the-art pelvis models do not adequately consider the variability in shape and size naturally occurring in human populations. In this study, we developed a new detailed pelvis finite element model, morphable to enable representation of the population shape variance. The model was validated using force-displacement data from post-mortem human subjects, in lateral loading of the denuded pelvis, followed by a global sensitivity analysis. The results suggests that in lateral impacts to the pelvis, pelvic shape contributes to the model response variance by the same magnitude as pelvic bone material stiffness, and that each of these contributions are approximately twice that of the cortical bone thickness. Hence, to model pelvic response for a general population accurately, future studies must consider both pelvic shape and the material properties in the analysis. Increased knowledge about population variability, and inclusion in safety evaluations, can result in more robust systems that reduce the risk of pelvic injuries in real-world accidents.
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| 3. |
- Brynskog, Erik, 1989, et al.
(författare)
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Predicting pelvis geometry using a morphometric model with overall anthropometric variables
- 2021
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Ingår i: Journal of Biomechanics. - : Elsevier BV. - 1873-2380 .- 0021-9290. ; 126
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Tidskriftsartikel (refereegranskat)abstract
- Pelvic fractures have been identified as the second most common AIS2+ injury in motor vehicle crashes, with the highest early mortality rate compared to other orthopaedic injuries. Further, the risk is associated with occupant sex, age, stature and body mass index (BMI). In this study, clinical pelvic CT scans from 132 adults (75 females, 57 males) were extracted from a patient database. The population shape variance in pelvis bone geometry was studied by Sparse Principal Component Analysis (SPCA) and a morphometric model was developed by multi- variate linear regression using overall anthropometric variables (sex, age, stature, BMI). In the analysis, SPCA identified 15 principal components (PCs) describing 83.6% of the shape variations. Eight of these were signifi- cantly captured (α < 0.05) by the morphometric model, which predicted 29% of the total variance in pelvis geometry. The overall anthropometric variables were significantly related to geometrical features primarily in the inferior-anterior regions while being unable to significantly capture local sacrum features, shape and position of ASIS and lateral tilt of the iliac wings. In conclusion, a new detailed morphometric model of the pelvis bone demonstrated that overall anthropometric variables account for only 29% of the variance in pelvis geometry. Furthermore, variations in the superior-anterior region of the pelvis, with which the lap belt is intended to interact, were not captured. Depending on the scenario, shape variations not captured by overall anthropometry could have important implications for injury prediction in traffic safety analysis.
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| 4. |
- Iraeus, Johan, 1973, et al.
(författare)
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A new open-source finite element lumbar spine model, its tuning and validation, and development of a tissue-based injury risk function for compression fractures
- 2023
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Ingår i: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI. - 2235-3151. ; , s. 1048-1072
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Konferensbidrag (refereegranskat)abstract
- Lumbar spine fractures have been identified as a problem in motor vehicle crashes, and it is expected that this problem might increase with the introduction of reclined postures in autonomous vehicles. Human body models provide a means to address this issue and develop countermeasures. In this study a new open-source finite element lumbar spine model and an associated tissue-based injury risk function were developed and validated. The injury risk function was based on trabecular bone compressive strain in the superior-inferior direction. The kinematic and kinetic validation showed that the model compared reasonably to experimental data, with axial compression and flexion predictions being closest to experimental results. The new risk function was found to have a good quality index. Even though the model evaluations indicated that the fracture risk was somewhat overpredicted, it was judged that the current model, together with the associated injury risk function, can be used to estimate the risk for compressive fractures in the lumbar spine, with the knowledge that these estimates are most likely somewhat conservative.
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| 5. |
- Larsson, Emma, 1991, et al.
(författare)
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Active Human Body Model Predictions Compared to Volunteer Response in Experiments with Braking, Lane Change, and Combined Manoeuvres
- 2019
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Ingår i: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI. - 2235-3151. ; :S1-9, s. 349-369
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Konferensbidrag (refereegranskat)abstract
- Active human body models are an important tool to study occupant interaction with safety systems in evasive manoeuvres such as braking and/or steering. In this study a finite element human body model with and without closed-loop active muscle control in the neck and lower trunk was compared to volunteer occupants in six different load cases with lane change, braking, and combined manoeuvres using standard and prepretensioned seat belts. Seven different muscle controllers, using two different muscle activation strategies based either on head and torso displacements or muscle length, and one with the controller turned off have been compared to volunteer kinematics. Cross-correlation analysis with CORA was used to evaluate the model biofidelity. The results show an improvement in CORA scores when using active muscles, compared to the model with muscle activity turned off, for one load case and similar CORA scores between the models for five load cases. CORA scores ranged from 0.78 to 0.88 for the active models and 0.70 to 0.82 from the model with muscles turned off. The active model gave a kinematic response with good biofidelity in lane change with braking, pure braking, and lane change with pre-pretensioned seat belt, but the biofidelity of the model was rated as fair in lane change with standard seat belt.
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| 6. |
- Larsson, Emma, 1991, et al.
(författare)
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Investigating sources for variability in volunteer kinematics in a braking maneuver, a sensitivity analysis with an active human body model
- 2023
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Ingår i: Frontiers in Bioengineering and Biotechnology. - 2296-4185. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Occupant kinematics during evasive maneuvers, such as crash avoidance braking or steering, varies within the population. Studies have tried to correlate the response to occupant characteristics such as sex, stature, age, and BMI, but these characteristics explain no or very little of the variation. Therefore, hypothesis have been made that the difference in occupant response stems from voluntary behavior. The aim of this study was to investigate the effect from other sources of variability: in neural delay, in passive stiffness of fat, muscle tissues and skin, in muscle size and in spinal alignment, as a first step towards explaining the variability seen among occupants in evasive maneuvers. A sensitivity analysis with simulations of the SAFER Human Body Model in braking was performed, and the displacements from the simulations were compared to those of volunteers. The results suggest that the head and torso kinematics were most sensitive to spinal alignment, followed by muscle size. For head and torso vertical displacements, the range in model kinematics was comparable to the range in volunteer kinematics. However, for forward displacements, the included parameters only explain some of the variability seen in the volunteer experiment. To conclude, the results indicate that the variation in volunteer vertical kinematics could be partly attributed to the variability in human characteristics analyzed in this study, while these cannot alone explain the variability in forward kinematics. The results can be used in future tuning of HBMs, and in future volunteer studies, when further investigating the potential causes of the large variability seen in occupant kinematics in evasive maneuvers.
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| 7. |
- Larsson, Emma, 1991, et al.
(författare)
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Passenger Kinematics Variance in Different Vehicle Manoeuvres - Biomechanical Response Corridors Based on Principal Component Analysis
- 2022
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Ingår i: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI. - 2235-3151. ; 2022-September, s. 793-843
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Konferensbidrag (refereegranskat)abstract
- This study explores the influence of occupant characteristics and belt type on occupant kinematics in evasive manoeuvres and provides models for construction of response corridors. Data originated from evasive manoeuvres with male and female volunteers. Principal component analysis and linear mixed models were used on selected data to create predictive models for kinematics and belt time histories, using belt configuration, sex, age, stature, and BMI as co-variates. Monte Carlo simulations of resulting models were used to generate upper and lower response corridor limits around the predicted responses. For translational and rotational displacements of the head and the torso, the first three principal components together captured 91%-99% of the variance in the responses. Belt configuration, sex, age, stature, BMI, and their interaction effects were found statistically significant (p < 0.05) in the linear mixed model analysis in lane changes, braking and U-turns at 40 km/h but not in U-turns at 30 km/h or when aware of turn. Response corridors for average sex, stature and BMI, were provided. In conclusion, the models and data provided can be used for validation of human body models with a range of anthropometries and in different manoeuvres and belt configurations potentially occurring in pre-crash manoeuvres.
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| 8. |
- Larsson, Emma, 1991, et al.
(författare)
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Predicting occupant head displacements in evasive maneuvers; tuning and comparison of a rotational based and a translational based neck muscle controller
- 2023
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Ingår i: Frontiers in Bioengineering and Biotechnology. - 2296-4185. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Objective : Real-life car crashes are often preceded by an evasive maneuver, which can alter the occupant posture and muscle state. To simulate the occupant response in such maneuvers, human body models (HBMs) with active muscles have been developed. The aim of this study was to implement an omni-directional rotational head-neck muscle controller in the SAFER HBM and compare the bio-fidelity of the HBM with a rotational controller to the HBM with a translational controller, in simulations of evasive maneuvers. Methods : The rotational controller was developed using an axis-angle representation of head rotations, with x, y, and z components in the axis. Muscle load sharing was based on rotational direction in the simulation and muscle activity recorded in three volunteer experiments in these directions. The gains of the rotational and translational controller were tuned to minimize differences between translational and rotational head displacements of the HBM and volunteers in braking and lane change maneuvers using multi-objective optimizations. Bio-fidelity of the model with tuned controllers was evaluated objectively using CORrelation and Analysis (CORA). Results : The results indicated comparable performance for both controllers after tuning, with somewhat higher bio-fidelity for rotational kinematics with the translational controller. After tuning, good or excellent bio-fidelity was indicated for both controllers in the loading direction (forward in braking, and lateral in lane change), with CORA scores of 0.86−0.99 and 0.93−0.98 for the rotational and translational controllers, respectively. For rotational displacements, and translational displacements in the other directions, bio-fidelity ranged from poor to excellent, with slightly higher average CORA scores for the HBM with the translational controller in both braking and lane changing. Time-averaged muscle activity was within one standard deviation of time-averaged muscle activity from volunteers. Conclusion : Overall, the results show that when tuned, both the translational and rotational controllers can be used to predict the occupant response to an evasive maneuver, allowing for the inclusion of evasive maneuvers prior to a crash in evaluation of vehicle safety. The rotational controller shows potential in controlling omni-directional head displacements, but the translational controller outperformed the rotational controller. Thus, for now, the recommendation is to use the translational controller with tuned gains.
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| 9. |
- Larsson, Karl-Johan, 1985, et al.
(författare)
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A First Step Toward a Family of Morphed Human Body Models Enabling Prediction of Population Injury Outcomes
- 2024
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Ingår i: Journal of Biomechanical Engineering. - 0148-0731 .- 1528-8951. ; 146:3
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Tidskriftsartikel (refereegranskat)abstract
- The injury risk in a vehicle crash can depend on occupant specific factors. Virtual crash testing using finite element human body models (HBMs) to represent occupant variability can enable the development of vehicles with improved safety for all occupants. In this study, it was investigated how many HBMs of different sizes that are needed to represent a population crash outcome through a metamodel. Rib fracture risk was used as an example occupant injury outcome. Morphed HBMs representing variability in sex, height, and weight within defined population ranges were used to calculate population variability in rib fracture risk in a frontal and a side crash. Two regression methods, regularized linear regression with second-order terms and Gaussian process regression (GPR), were used to metamodel rib fracture risk due to occupant variability. By studying metamodel predictive performance as a function of training data, it was found that constructing GPR metamodels using 25 individuals of each sex appears sufficient to model the population rib fracture risk outcome in a general crash scenario. Further, by utilizing the known outcomes in the two crashes, an optimization method selected individuals representative for population outcomes across both crash scenarios. The optimization results showed that 5–7 individuals of each sex were sufficient to create predictive GPR metamodels. The optimization method can be extended for more crashes and vehicles, which can be used to identify a family of HBMs that are generally representative of population injury outcomes in future work.
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| 10. |
- Larsson, Karl-Johan, 1985, et al.
(författare)
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Evaluation of a diverse population of morphed human body models for prediction of vehicle occupant crash kinematics
- 2022
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Ingår i: Computer Methods in Biomechanics and Biomedical Engineering. - : Informa UK Limited. - 1476-8259 .- 1025-5842. ; 25:10, s. 1125 -1155
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Tidskriftsartikel (refereegranskat)abstract
- Morphing can be used to alter human body models (HBMs) to represent a diverse population of occupants in car crashes. The mid-sized male SAFER HBM v9 was parametrically morphed to match 22 Post Mortem Human Subjects, loaded in different configurations. Kinetics and kinematics were compared for the morphed and baseline HBMs. In frontal impacts, the morphed HBMs correlated closer with the kinematics of obese subjects, but lower to small females. In lateral impacts HBM responses were too stiff. This study outlines a necessary evaluation of all HBMs that should be morphed to represent the diverse population in vehicle safety evaluations.
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