| 1. |
|
|
| 2. |
|
|
| 3. |
- Arikere, Adithya, 1987, et al.
(författare)
-
On the Potential of Accelerating an Electrified Lead Vehicle to Mitigate Rear-End Collisions
- 2015
-
Ingår i: Proceedings of the 3rd International Symposium on Future Active Safety Technology Towards zero traffic accidents, 2015. ; , s. 377-384
-
Konferensbidrag (refereegranskat)abstract
- This paper analyzes the potential safety benefit from autonomous acceleration of an electrified lead vehicle to mitigate or prevent being struck from behind. Safety benefit was estimated based on the expected reduction in relative velocity at impact in combination with injury risk curves. Potential issues and safety concerns with the operation and implementation of such a system in the real world are discussed from an engineering and human factors stand point. In particular, the effect of the pre-collision acceleration in reducing whiplash injury risk due to change in head posture and reduction of crash severity is also discussed. In general, this study found that autonomously accelerating an electrified lead vehicle can mitigate and prevent rear-end collisions and significantly increase the safety benefits from existing systems such as autonomous emergency braking.
|
|
| 4. |
- Brolin, Karin, 1974, et al.
(författare)
-
Finite Element Musculoskeletal Model with Feedback Control to Simulate Spinal Postural Responses
- 2014
-
Ingår i: 7th World Congress of Biomechanics. ; July 6-11, Boston, USA:18-14
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Today, most Finite Element (FE) Human Body Models (HBMs) are intended for crash simulations and not for pre-crash events, due to the lack of active muscles. To study combined pre- and in crash events, muscle activity is essential. Therefore, this work presents a method to implement postural muscle responses in an FE HBM.The Total HUman Model for Safety (THUMS®) AM50 version 3.0 (Toyota Central Labs Inc, Nagakute, Japan) was chosen and a model of active musculature was added (Östh et al. 2012). The trunk, neck, upper and lower extremities were represented by 394 Hill-type line elements. Muscle activation levels were generated by seven proportional, integrative, and derivative feedback controllers for the controlled angles of the spine and upper extremities, Figure 1. For each controller, the deviation from the initial angle was used to generate correcting moment requests to the flexors and extensor muscles in the respective body region. Neural delay was implemented by a time offset for the controlled angle. The request was scaled with the maximum strength of the muscles and then passed through a muscle activation dynamics model.The model response was compared to an experimental volunteer study that measured muscle activity, kinematics, and boundary conditions for drivers and passengers, riding on rural roads in a passenger car, subjected to autonomous and driver braking. The experimental braking pulse was applied to the model seated in an FE model of the front seat and restrained with seat belts. The results show that postural feedback control can be utilized to model driver and passenger responses to autonomous braking interventions in the sagittal plane. However, the model overestimated head rotation for driver braking events. Volunteer muscle activity occurred prior to deceleration onset, which cannot be captured by the feedback control model. Therefore, a hypothesized anticipatory postural response was implemented by modifying the reference value of the feedback controllers based on the volunteer data. The result was earlier onset of muscle activity and a kinematic response that was within one standard deviation of the corresponding test data from volunteers performing maximum braking.
|
|
| 5. |
- Brolin, Karin, 1974, et al.
(författare)
-
Towards omni-directional active human body models
- 2016
-
Ingår i: 6th International Symposium on Human Modeling and Simulation in Automotive Engineering, Heidelberg, GERMANY, October 20-21.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)
|
|
| 6. |
- Cutcliffe, Hattie, et al.
(författare)
-
Gender Differences in Occupant Posture and Muscle Activity with Motorized Seat Belts
- 2015
-
Ingår i: The 24th ESV Conference Proceedings.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this study was to assess gender differences in the posture and muscular activity of occupants in response to pretension from motorized seatbelts. Male and female vehicle occupants were tested in both front seat positions during normal driving and autonomous braking. This data is useful for the development of human body models (HBM), and increases the understanding of the effects of motorized belts.Kinematics and electromyography (EMG) were analyzed for 18 volunteers (9 male, 9 female) subjected to autonomous braking (11 m/s2 deceleration) during real driving on rural roads. Two restraint configurations were tested: a standard belt and a motorized belt, activated 240 ms before the initiation of braking. Statistical comparison of volunteers’ posture and normalized EMG amplitudes was performed to understand differences incurred by the motorized belts, as well as to compare response across gender and role (occupant position within the vehicle). Data was analyzed both prior to and at vehicle deceleration, which occurred 240 ms after motorized belt onset.Motorized belts significantly affected all postural metrics, and significantly elevated the activity of all muscles compared to typical riding. Though increases in muscle activity were small at deceleration onset compared with typical riding for male occupants and female passengers, female drivers demonstrated significantly larger increases in muscular activity: between 5 and 13% of the maximum voluntary contraction (MVC). At deceleration onset, standard belts showed little change in posture or muscle activation, with the median changes being well within the ranges exhibited during typical riding for all groups (i.e. not distinguishable from typical riding). Typical riding postures of males and females were similar, as were muscular activation levels—generally less than 5% of the MVC. However, drivers exhibited significantly higher muscular activity in the arm and shoulder muscles than passengers.Limitations include the repeated nature of the testing, as prior work has shown that habituation across trials alters occupant response compared to that of unaware occupants. However, randomization of the trial order helped mitigate potential habituation effects. Another limitation is the sample size of 18 volunteers.An important finding of this study is that the increase in occupant muscular activation seen with motorized belts was gender-specific: at deceleration, the change in activation of most muscles was significantly different across gender and belt type, with female drivers exhibiting larger increases in muscular activation than male drivers or passengers of either gender, particularly in the arm muscles. These activations appeared to be startle responses, and may have implications for interactions with the steering wheel and motion during a braking or crash event. This warrants further studies and stresses the importance of quantifying male and female subjects separately in future studies of pre-crash systems.
|
|
| 7. |
- Cutcliffe, Hattie, et al.
(författare)
-
Gender differences in Occupant Posture during Driving and Riding
- 2017
-
Ingår i: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI. - 2235-3151. ; Antwerp, 2017, September 13-15:IRC-17-12, s. 23-33
-
Konferensbidrag (refereegranskat)abstract
- The aim of this study was to compare postures of male and female vehicle occupants, tested in both front seat positions, during normal driving and deceleration onset. These data are useful for the development and initialisation of computational human body models. A secondary aim was to examine the effect of reversible, motorised seat belts in these events. Kinematics were analysed for volunteers driving on rural roads, prior to autonomous braking (11 m/s2 deceleration). Two restraint configurations were tested: a standard versus a motorized belt, activated 200 ms before braking initiation. Kinematic metric comparison via ANCOVA was performed to understand postural differences across gender, role (driver/passenger), and belt type (standard/motorised). Data was analysed prior to and at vehicle deceleration, termed typical riding and initial braking, respectively.While males and females displayed similar postures during typical riding, differences existed between driversand passengers, especially with respect to neck posture. Drivers displayed more protracted neck postures, withsignificantly smaller (by 22‐27 mm, depending on gender) head‐to‐sternum horizontal distances, than passengers.Motorised belts significantly changed posture during initial braking, notably of the chest (which was shiftedposteriorly by approximately 13 mm, depending on gender and role), while standard belts did not. Within a given belt type, occupants’ change in posture was similar across gender and role during initial braking.
|
|
| 8. |
|
|
| 9. |
- Olafsdottir, Jóna Marin, 1985, et al.
(författare)
-
Cervical Muscle Responses to Multi-Directional Perturbations
- 2014
-
Ingår i: 7th World Congress of Biomechanics.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Numerical human models are widely used in the design process and evaluation of passive and active vehicle safety systems in pre-crash and crash situations. Development and validation of human models that simulate neuromuscular control requires information on muscle activation patterns and contraction levels for different loading directions. Due to the lack of experimental data on cervical muscle recruitment strategies, the aim of this study was to provide activation patterns for superficial and deep cervical muscles during multidirectional perturbations.Eight volunteers received three perturbations (apeak=1.5g, ∆v=0.5m/s) in each of eight different directions while seated unrestrained on a sled-mounted car seat without a head restraint. Volunteers received no warning of perturbation onset. Electromyographic (EMG) activity was measured with wire electrodes inserted into the left sternocleidomastoid (SCM), trapezius (Trap), levator scapulae (LS), splenius capitis (SPL), semispinalis capitis (SCap), semispinalis cervicis (SCerv), and multifidus (Multi) muscles, and with surface electrodes over the sternohyoid (STH) muscle. All EMG signals were normalized with maximum voluntary isometric contraction activity.All median muscle activities were below 5%MVC before perturbation onset. During perturbation, most muscles showed distinctive activation patterns consistent with their anatomical location and function. Anterior muscles (SCM, STH) activated to counteract head extension and posterior muscles, except SPL, activated to counteract flexion (Figure). Although with different levels of contraction, SCap, SCerv, and Multi activated synergistically with the highest activity (89%, 50%, and 36%MVC respectively, 110ms after perturbation onset) during rearward and ipsilateral rearward oblique perturbations. Activation levels were generally five times lower in other directions. Despite its posterior location, SPL had activities between 19%MVC and 27%MVC during forward, forward oblique and lateral perturbations, but
|
|
| 10. |
- Olafsdottir, Jóna Marin, 1985, et al.
(författare)
-
Dynamic Spatial Tuning of Cervical Muscle Reflexes to Multidirectional Seated Perturbations
- 2015
-
Ingår i: Spine. - 0362-2436 .- 1528-1159. ; 40:4, s. E211-E219
-
Tidskriftsartikel (refereegranskat)abstract
- Study Design. Human volunteers were exposed experimentally to multidirectional seated perturbations.Objective. To determine the activation patterns, spatial distribution and preferred directions of reflexively activated cervical muscles for human model development and validation.Summary of Background Data. Models of the human head and neck are used to predict occupant kinematics and injuries in motor vehicle collisions. Because of a dearth of relevant experimental data, few models use activation schemes based on in vivo recordings of muscle activation and instead assume uniform activation levels for all muscles within presumed agonist or antagonist groups. Data recorded from individual cervical muscles are needed to validate or refute this assumption.Methods. Eight subjects (6 males, 2 females) were exposed to seated perturbations in 8 directions. Electromyography was measured with wire electrodes inserted into the sternocleidomastoid, trapezius, levator scapulae, splenius capitis, semispinalis capitis, semispinalis cervicis, and multifidus muscles. Surface electrodes were used to measure sternohyoid activity. Muscle activity evoked by the perturbations was normalized with recordings from maximum voluntary contractions.Results. The multidirectional perturbations produced activation patterns that varied with direction within and between muscles. Sternocleidomastoid and sternohyoid activated similarly in forward and forward oblique directions. The semispinalis capitis, semispinalis cervicis, and multifidus exhibited similar spatial patterns and preferred directions, but varied in activation levels. Levator scapulae and trapezius activity generally remained low, and splenius capitis activity varied widely between subjects.Conclusion. All muscles showed muscle- and direction-specific contraction levels. Models should implement muscle- and direction-specific activation schemes during simulations of the head and neck responses to omnidirectional horizontal perturbations where muscle forces influence kinematics, such as during emergency maneuvers and low-severity crashes.Level of Evidence: N/A
|
|
| 11. |
- Olafsdottir, Jóna Marin, 1985, et al.
(författare)
-
Energy Recuperation in Fully Electric Vehicles Subject to Stability and Drivability Requirements
- 2012
-
Ingår i: The 11th International Symposium on Advanced Vehicle Control.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents a combined control and estimation framework for energy recuperation in fully electric vehicles. We consider a fully electric powertrain, with a driven front axle operating on low friction road surfaces. Our objective is to find the blending of regenerative and friction braking that maximizes the amount of recovered energy (i.e., the regenerative braking), while (i) delivering the total braking force requested by the driver, (ii) preserving the yaw stability as well as driveability of the vehicle. The proposed framework, which consists of a predictive braking control algorithm and a vehicle state and parameters estimator, is appealing because it requires minimal re-design efforts in order to cope with different powertrain layouts (e.g., individual wheel motors) and/or control objective and design and physical constraints. We present simulation results, obtained in three sets of manoeuvres, showing promising results in terms of energy recuperation, vehicle stability and driveability.
|
|
| 12. |
- Olafsdottir, Jóna Marin, 1985, et al.
(författare)
-
Modelling reflex recruitment of neck muscles in a finite element human body model for simulating omnidirectional head kinematics
- 2019
-
Ingår i: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI. - 2235-3151. ; , s. 308-323
-
Konferensbidrag (refereegranskat)abstract
- Numerical human body models that can predict occupant head and neck responses are essential for the development and assessment of motor vehicle safety systems. Including the contribution of neck muscle responses is needed to improve model predictions, in particular during simulated pre-crash manoeuvers. While a general purpose model that can predict head-neck kinematics in various pre-crash conditions (e.g. emergency braking and steering) is needed most current models have been limited to predictions of longitudinal motion (e.g. during emergency braking). We developed a method for simulating muscle recruitment in a finite element human body model for omnidirectional head-neck kinematics predictions. A neural control scheme that uses kinematics and muscle length feedback to determine the activation level in individual muscle elements was implemented. The control scheme included a novel approach to determine load sharing between muscles based on experimental data from human subjects in dynamic conditions. Multidirectional 1 g loading conditions were simulated to assess the effect of muscle recruitment on head and neck kinematics in multiple directions and to evaluate the predicted spatial tuning of recruitment for selected muscles. Simulation results demonstrate that including both kinematics and muscle length feedback reduces head and internal neck motion induced from external 1 g loading.
|
|
| 13. |
- Olafsdottir, Jóna Marin, 1985
(författare)
-
Muscle Responses in Dynamic Events. Volunteer experiments and numerical modelling for the advancement of human body models for vehicle safety assessment.
- 2017
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Fatalities and injuries to car occupants in motor vehicle crashes continue to be aserious global socio-economic issue. Advanced safety systems that provide improvedoccupant protection and crash mitigation have the potential to reduce this burden.For the development and virtual assessment of these systems, numerical human bodymodels (HBMs) that predict occupant responses have been developed. Currently,there is a need for increasing the level of biofidelity in these models to facilitatesimulation of occupant responses influenced by muscle contraction, such as oftenexperienced during pre-crash vehicle manoeuvres.The aim of this thesis was to provide data and modelling approaches for theadvancement of HBMs capable of simulating occupant responses in a wide rangeof pre-crash scenarios. Volunteer experiments were conducted to study driver andpassenger responses during emergency braking with a standard seatbelt and with aseatbelt equipped with a reversible pre-tensioner. Muscle activity, kinematic, andboundary condition data were collected. The data showed that pre-tensioning theseatbelt prior to braking influenced the muscular and kinematic responses of occupants.Drivers modified their responses during voluntary braking, resulting indifferent kinematics than were observed during autonomous braking. Passenger anddriver responses also differed during autonomous braking. The findings demonstratethat HBMs need to account for the differences in postural responses between occupantroles as well as the adjustments made by drivers during voluntary braking. Thestudies provide detailed data sets that can be used for model tuning and validation.The modelling efforts of this work focused on simulation of head-neck responses.To facilitate the modelling of neck muscle recruitment, muscle activity data from volunteersexposed to multi-directional horizontal seated perturbations were analysed.The derived spatial tuning curves revealed muscle- and direction-specific recruitmentpatterns. The experimental tuning curves can be used as input to models or to verifyspatial tuning of muscle recruitment in HBMs.A method for simulating muscle recruitment of individual neck muscles was developed.The approach included a combination of head kinematics and muscle lengthfeedback to generate muscle specific activation levels. The experimental tuningcurves were used to define appropriate sets of muscle activation in response to headkinematics feedback. The predicted spatial tuning using the two feedback loops wasverified in multi-directional horizontal gravity simulations. The results showed thatmuscle activation generated by individual or combined feedback loops influenced thepredicted head and intervertebral kinematics. The developed method has the potentialto improve prediction of omnidirectional head and neck responses with HBMs.However, further work is needed to verify these findings.Overall, this research has increased knowledge about the muscle responses ofoccupants in dynamic events typical of pre-crash scenarios. The findings highlightimportant aspects that must be considered to enable active HBMs to capture a widerange of occupant responses. The data presented support the advancement of currentand future HBMs, which will contribute to the development of improved safetysystems that reduce the number of fatalities and injuries in motor vehicle crashes.
|
|
| 14. |
|
|
| 15. |
- Olafsdottir, Jóna Marin, 1985, et al.
(författare)
-
Passenger Kinematics and Muscle Responses in Autonomous Braking Events with Standard and Reversible Pre‐tensioned Restraints
- 2013
-
Ingår i: IRCOBI Conference 2013. - 2235-3151. ; :IRC-13-70, s. 602-617
-
Konferensbidrag (refereegranskat)abstract
- Biofidelic human body models (HBMs) with active muscles are valuable tools for assessing the safety potential of systems that are active immediately before and during a crash. For validation, experimental data including muscle activity are required. This paper provides a data set for front seat passengers in autonomous braking events comprising 20 volunteers (11 male and 9 female) in a passenger car. Volunteers were subjected to two different autonomous braking test cases of 1.1 g, wearing a standard belt and a reversible pre-tensioned belt activated 200 ms before deceleration onset. The following data were collected: muscle activity with electromyography, kinematics with video tracking, footwell force, belt force and belt pay-out. Head and T1 displacements were shorter with a pre-tensioned belt while head rotation was similar for both test cases. Kinematics did not display any significant gender differences. Average muscle activity with a pre-tensioned belt increased rapidly before onset of deceleration for females, but not for males. Muscle activity, predominantly in the cervical and lumbar extensors, increased soon after vehicle deceleration onset for all volunteers wearing the standard belt. All muscles were significantly more active during braking than normal driving. Data are presented in corridors for use when validating active HBMs.
|
|
| 16. |
- Olafsdottir, Jóna Marin, 1985, et al.
(författare)
-
Trunk muscle recruitment patterns in simulated precrash events
- 2018
-
Ingår i: Traffic Injury Prevention. - : Informa UK Limited. - 1538-957X .- 1538-9588. ; 19, s. S186-S188
-
Tidskriftsartikel (refereegranskat)abstract
- Objectives: To quantify trunk muscle activation levels during whole body accelerations that simulate precrash events in multiple directions and to identify recruitment patterns for the development of active human body models. Methods: Four subjects (1 female, 3 males) were accelerated at 0.55 g (net Δv = 4.0 m/s) in 8 directions while seated on a sled-mounted car seat to simulate a precrash pulse. Electromyographic (EMG) activity in 4 trunk muscles was measured using wire electrodes inserted into the left rectus abdominis, internal oblique, iliocostalis, and multifidus muscles at the L2–L3 level. Muscle activity evoked by the perturbations was normalized by each muscle's isometric maximum voluntary contraction (MVC) activity. Spatial tuning curves were plotted at 150, 300, and 600 ms after acceleration onset. Results: EMG activity remained below 40% MVC for the three time points for most directions. At the 150- and 300 ms time points, the highest EMG amplitudes were observed during perturbations to the left (–90°) and left rearward (–135°). EMG activity diminished by 600 ms for the anterior muscles, but not for the posterior muscles. Conclusions: These preliminary results suggest that trunk muscle activity may be directionally tuned at the acceleration level tested here. Although data from more subjects are needed, these preliminary data support the development of modeled trunk muscle recruitment strategies in active human body models that predict occupant responses in precrash scenarios.
|
|
| 17. |
- Olafsdottir, Jóna Marin, 1985
(författare)
-
Volunteer Muscle Activity in Dynamic Events. Input Data for Human Body Models.
- 2014
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Human body models (HBMs) are virtual human surrogates used to predict kinematic and injury responses during motor vehicle crashes. In recent years, active musculature has been incorporated into HBMs for enhanced biofidelity in simulated emergency scenarios, in particular low-severity crashes and pre-crash situations, where occupant responses are influenced by muscle tension. Development and validation of HBMs that simulate neuromuscular control requires information on muscle activation patterns and contraction levels for different loading levels and directions. This information can be acquired by measuring muscle activity in volunteers with electromyography in replicated pre-crash events. This thesis investigates occupant responses in various pre-crash type braking scenarios and multidirectional perturbations. Muscle activity was measured in volunteers in the following scenarios; maximum voluntary braking, autonomous braking with standard seatbelt, autonomous braking with reversible pre-tensioner activated 200 ms before braking, and seated perturbation in multiple directions without restraint. Muscle activity and forward displacement during autonomous braking was influenced by type of restraint system and role (passenger vs. driver). Pre-tensioning the seatbelt caused decreased forward displacement as well as increased startle like muscle activity in some volunteers. Active HBMs that model the startle reflex can elucidate its effect on injury risk in the crash phase. The difference in posture between drivers and passengers resulted in decreased upper extremity and increased lower back muscle activity for passengers and more forward displacement. Active HBMs validated against the data presented here can be used to further assess the difference between the two occupant roles and to aid the optimisation of safety systems for each group. The spatial tuning patterns generated from multidirectional perturbation showed variable activation amplitudes and preferred directions for the neck muscles. Implementing muscle and direction specific activation schemes in active HBMs might result in better prediction of the head and neck responses. The research outcomes provide data sets for active HBM validation in pre-crash braking events and the development and validation of omnidirectional models. Further studies that identify occupant muscle responses are needed. Measuring muscle activity during a pre-crash steering manoeuvre or during a realistic visual threat to identify the muscle responses following a startle reflex would support the advancement of future omnidirectional models and startle reflex control methods.
|
|
| 18. |
- Östh, Jonas, 1983, et al.
(författare)
-
Driver Kinematic and Muscle Responses in Braking Events with Standard and Reversible Pre-tensioned Restraints: Validation Data for Human Models
- 2013
-
Ingår i: Stapp car crash journal. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 1532-8546. ; 57, s. 1-41
-
Tidskriftsartikel (refereegranskat)abstract
- The objectives of this study are to generate validation data for human models intended for simulation of occupant kinematics in a pre-crash phase, and to evaluate the effect of an integrated safety system on driver kinematics and muscle responses. Eleven male and nine female volunteers, driving a passenger car on ordinary roads, performed maximum voluntary braking; they were also subjected to autonomous braking events with both standard and reversible pre-tensioned restraints. Kinematic data was acquired through film analysis, and surface electromyography (EMG) was recorded bilaterally for muscles in the neck, the upper extremities, and lumbar region. Maximum voluntary contractions (MVCs) were carried out in a driving posture for normalization of the EMG. Seat belt positions, interaction forces, and seat indentions were measured.During normal driving, all muscle activity was below 5% of MVC for females and 9% for males. The range of activity during steady state braking for males and females was 13–44% in the cervical and lumbar extensors, while antagonistic muscles showed a co-contraction of 2.3–19%. Seat belt pre-tension affects both the kinematic and muscle responses of drivers. In autonomous braking with standard restraints, muscle activation occurred in response to the inertial load. With pre-tensioned seat belts, EMG onset occurred earlier; between 71 ms and 176 ms after belt pre-tension. The EMG onset times decreased with repeated trials and were shorter for females than for males. With the results from this study, further improvement and validation of human models that incorporate active musculature will be made possible.
|
|
| 19. |
- Östh, Jonas, 1983, et al.
(författare)
-
Modeling Active Human Muscle Responses during Driver and Autonomous Avoidance Maneuvers
- 2014
-
Ingår i: 3rd International Workshop on Computational Engineering CE 2014.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Integration of pre-crash and in-crash safety systems has a potential to further reduce car occupant fatalities and to mitigate injuries. However, the introduction of integrated safety systems creates new requirements for Human Body Models (HBMs) as occupant kinematics must be predicted for a longer period of time, in order to evaluate the effect of systems activated before the crash phase. For this purpose, a method to model car occupant muscle responses in a finite element (FE) HBM have been developed, utilizing feedback control of Hill-type muscle elements. The model has been applied to study occupant kinematics under the influence of autonomous and driver braking deceleration. Ongoing work aims at extending the model to be able to also capture human responses to lateral and oblique pre-crash loading.
|
|
| 20. |
- Östh, Jonas, 1983, et al.
(författare)
-
Modelling of Car Occupant Muscle Responses in a Finite Element Human Body Model
- 2014
-
Ingår i: 11 World Congress and V European Conference on Computational Mechanics, July 20-25, 2014, Barcelona.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Over 30 000 fatalities related to the road transport system are reported in Europe annually. Of these fatalities, the largest share is car occupants, even though significant improvements in vehicle safety have been achieved by the implementation of in-crash restraints and pre-crash driver support systems. Integration of pre-crash and in-crash safety systems provides a potential for further reduction of car occupant fatalities. For virtual development of integrated systems, numerical occupant models are needed. At the present, finite element (FE) human body models (HBM) are commonly used for crash simulations, but not for pre-crash scenarios due to the lack of active muscles. This presentation addresses a method to include postural muscle responses in an FE HBM for simulation of integrated safety systems.
|
|
| 21. |
- Östh, Jonas, 1983, et al.
(författare)
-
Muscle Activation Strategies in Human Body Models for the Development of Integrated Safety
- 2015
-
Ingår i: The 24th ESV Conference Proceedings.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Human Body Models (HBMs) have been used in crash safety research for some time, and are now emerging as tools for the development of restraints systems. One important challenge in the development of advanced restraint systems is to integrate sensory information about the pre-crash phase (time to collision, impact speed and direction, occupant position) to alter restraint activation parameters. Restraint activation can begin even before the beginning of an impact, providing additional time to reposition or restrain the occupant. However, any such pre-crash intervention would invoke a muscle response that needs to be taken into account in HBMs used in simulation of integrated restraints. The objective of this paper is to provide an update on state-of-the-art modeling techniques for active musculature in HBMs. Examples of applications are presented, to illustrate future challenges in modeling of car occupants muscle responses to restraint activation.The most common approach for modeling active muscle force in HBMs is to use Hill-type models, in which the force produced is a function of muscle length, shortening velocity, and activation level. Active musculature was first implemented in cervical spine models. These models were applied to study occupant kinematic responses and injury outcome in rear-end, lateral, and frontal impacts; it was found that active musculature is essential for studying the response of the cervical spine. One approach utilized to represent muscle activity in HBMs is to use experimentally recorded muscle activities or activity levels acquired through inverse optimization in open-loop. More recently, in order to represent car occupant muscle responses in pre-crash situations, closed-loop control has been implemented for multibody and finite element HBMs, allowing the models to maintain their posture and simulate reflexive responses. Studies with these models showed that in addition to feedback control, anticipatory postural responses needs to be included to represent driver actions such as voluntary braking. Current HBMs have the capacity to model (utilizing closed-loop control) active muscle responses of car occupants in longitudinal pre-crash events. However, models have only been validated for limited sets of data since as high quality volunteer data, although it exists, is scarce. Omni-directional muscle responses have been implemented to some extent, but biofidelity of the simulated muscle activation schemes has not been assessed. Additional experimental volunteer muscle activity measurements (with normalized electromyogram recordings) in complex 3D-loading scenarios are needed for validation and to investigate how muscle recruitment depends on occupant awareness and varies between individuals. Further model development and validation of muscle activations schemes are necessary, for instance startle responses, and individual muscle control. This could improve assessment of restraint performance in complex accident scenarios, such as multiple impacts, far-side impacts and roll-over situations.
|
|
