| 1. |
- Leledakis, Alexandros, 1991, et al.
(författare)
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Influence of an Individualised Shoulder Belt Position for Diverse Occupant Anthropometries on Seatbelt Interaction in Frontal and Side Impacts
- 2023
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Ingår i: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI. - 2235-3151. ; , s. 639-664
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Konferensbidrag (refereegranskat)abstract
- This simulation study investigated the influence of individualised shoulder belt position on seatbelt interaction and occupant kinematics in two frontal and one far side impact, considering the variability of occupant anthropometry and sitting postures. Morphed Human Body Models, positioned as front passengers, were simulated in 132 setups. For every occupant, an individualised shoulder belt position configuration was created by changing the D-ring mounting location, aiming for a mid-shoulder belt fit. A “traditional belt” configuration was also tested, with the D-ring mounted on the B-pillar. The initial belt's placement over the occupant's shoulder was influential; however, it may not necessarily lead to an overall improved seatbelt interaction as a single parameter. Different occupants were associated with different seatbelt interaction challenges. Tall occupants with low Body Mass Index (BMI) were more likely to slide out of the shoulder belt, while short low-BMI occupants were more likely to submarine. The early torso to pelvis retention balance and the torso’s axial rotations were identified as the main mechanisms behind those observations. The study identified seatbelt interaction challenges for different occupant groups and could facilitate the analysis of additional changes in belt characteristics towards individualised occupant restraint systems.
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| 2. |
- Leledakis, Alexandros, 1991, et al.
(författare)
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The Influence of Occupant's Size, Shape and Seat Adjustment in Frontal and Side Impacts
- 2022
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Ingår i: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI. - 2235-3151. ; 2022-September, s. 549-584
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Konferensbidrag (refereegranskat)abstract
- The sensitivity of occupant kinematic and kinetic crash responses to anthropometric and seat adjustment variation was investigated by performing frontal- and side-impact simulations with a family of morphed Human Body Models (HBMs). The HBM family included variations of shape and size, accounting for stature, Body Mass Index (BMI) and sex. A global sensitivity analysis method was developed and applied. Increased BMI was associated with increased spinal and extremity loading in the HBM for all evaluated impacts. Increasing the stature resulted in a consistent increase in lower extremity loading. The fore-aft seat position influenced the head and torso speed relative to the vehicle interior. Furthermore, in high-severity frontal impacts, adjusting the seat position rearwards altered the load path, increasing the HBM pelvic and lumbar spine loading in favour of reducing the lower extremity forces, and vice versa when the seat was positioned forward. The results from this study highlight potential occupant protection challenges and trade-offs, and can be used to enhance protection, considering occupant anthropometric diversity and seat adjustment variation.
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| 3. |
- 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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| 4. |
- 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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| 5. |
- 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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| 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. |
- Leledakis, Alexandros, 1991, et al.
(författare)
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A method for predicting crash configurations using counterfactual simulations and real-world data
- 2021
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Ingår i: Accident Analysis and Prevention. - : Elsevier BV. - 0001-4575. ; 150
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Tidskriftsartikel (refereegranskat)abstract
- Traffic safety technologies revolve around two principle ideas; crash avoidance and injury mitigation for inevitable crashes. The development of relevant vehicle injury mitigating technologies should consider the interaction of those two technologies, ensuring that the inevitable crashes can be adequately managed by the occupant and vulnerable road user (VRU) protection systems. A step towards that is the accurate description of the expected crashes remaining when crash-avoiding technologies are available in vehicles. With the overall objective of facilitating the assessment of future traffic safety, this study develops a method for predicting crash configurations when introducing crash-avoiding countermeasures. The predicted crash configurations are one important factor for prioritizing the evaluation and development of future occupant and VRU protection systems. By using real-world traffic accident data to form the baseline and performing counterfactual model-in-the-loop (MIL) pre-crash simulations, the change in traffic situations (vehicle crashes) provided by vehicles with crash-avoiding technologies can be predicted. The method is built on a novel crash configuration definition, which supports further analysis of the in-crash phase. By clustering and grouping the remaining crashes, a limited number of crash configurations can be identified, still representing and covering the real-world variation. The developed method was applied using Swedish national- and in-depth accident data related to urban intersections and highway driving, and a conceptual Autonomous Emergency Braking system (AEB) computational model. Based on national crash data analysis, the conflict situations Same-Direction rear-end frontal (SD-ref) representing 53 % of highway vehicle-to-vehicle (v2v) crashes, and Straight Crossing Path (SCP) with 21 % of urban v2v intersection crashes were selected for this study. Pre-crash baselines, for SD-ref (n = 1010) and SCP (n = 4814), were prepared based on in-depth accident data and variations of these. Pre-crash simulations identified the crashes not avoided by the conceptual AEB, and the clustering of these revealed 5 and 52 representative crash configurations for the highway SD-ref and urban intersection SCP conflict situations, respectively, to be used in future crashworthiness studies. The results demonstrated a feasible way of identifying, in a predictive way, relevant crash configurations for in-crash testing of injury prevention capabilities.
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| 10. |
- Leledakis, Alexandros, 1991, et al.
(författare)
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The influence of car passengers’ sitting postures in intersection crashes
- 2021
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Ingår i: Accident Analysis and Prevention. - : Elsevier BV. - 0001-4575. ; 157
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Tidskriftsartikel (refereegranskat)abstract
- Car passengers are frequently sitting in non-nominal postures and are able to perform a wide range of activities since they are not limited by tasks related to vehicle control, contrary to drivers. The anticipated introduction of Autonomous Driven vehicles could allow “drivers” to adopt similar postures and being involved in the same activities as passengers, allowing them a similar set of non-nominal postures. Therefore, the need to investigate the effects of non-nominal occupant sitting postures during relevant car crash events is becoming increasingly important. This study aims to investigate the effect of different postures of passengers in the front seat of a car on kinematic and kinetic responses during intersection crashes. A Human Body Model (HBM) was positioned in a numerical model of the front passenger seat of a midsize Sports Utility Vehicle (SUV) in a total of 35 postures, including variations to the lower and upper extremities, torso, and head postures. Three crash configurations, representative of predicted urban intersection crashes, were assessed in a simulation study; two side impacts, a near-side and a far-side, respectively, and a frontal impact. The occupant kinematics and internal loads were analyzed, and any deviation between the nominal and altered posture responses were quantified using cross-correlation of signals to highlight the most notable variations. Posture changes to the lower extremities had the largest overall influence on the lower extremities, pelvis, and whole-body responses for all crash configurations. In the frontal impact, crossing the legs allowed for the highest pelvis excursions and rotations, which affected the whole-body response the most. In the two side-impacts, leaning the torso in the coronal plane affected the torso and head kinematics by changing the interaction with the vehicle's interior. Additionally, in far-side impacts supporting the upper extremity on the center console resulted in increased torso excursions. Moreover, the response of the upper extremities was consistently sensitive to posture variations of all body regions.
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