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- Brolin, Karin, 1974, et al.
(författare)
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Evaluation at low g-level loading
- 2014
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Ingår i: 5th International Symposium on Human Modelling and Simulation in Automotive Engineering, Munich, Germany, October 16-17, 2014.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 2. |
- Brolin, Karin, 1974, et al.
(författare)
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Finite Element Musculoskeletal Model with Feedback Control to Simulate Spinal Postural Responses
- 2014
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Ingår i: 7th World Congress of Biomechanics. ; July 6-11, Boston, USA:18-14
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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.
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| 3. |
- Brolin, Karin, 1974, et al.
(författare)
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HUMAN BODY MODELING FOR APPLIED TRAFFIC SAFETY
- 2011
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Ingår i: SVENSKA MEKANIKDAGAR, 13-15 JUNI, 2011, Göteborg.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Traffic injuries are an important public health issue. To prevent, diagnose and treat injuriesit is vital to understand the mechanics of injuries. Here, mathematical models of the humanpresent a valuable complement to other models, such as animal models and crash dummies.Today, Human Body Models (HBM) are recognized as important tools within traffic safetyresearch. To successfully apply an HBM to improve and evaluate real life safety systems,it has to: (1) be numerically robust in a wide range of crash loading conditions, (2) becomputationally efficient to enable analyses with full car models, (3) represent the humanpopulation with respect to age, gender and anthropometry, (4) maintain its posture in agravitational field for pre-crash events, (5) predict the onset of tissue injury and organ failure,and (6) simulate muscle tension due to bracing and muscle reflexes. Therefore, work is ongoingto model the active muscle response and improve the injury predictability of currently availableFE HBM.The commercially available HBM Total HUman Model for Safety [1], called THUMS,was used with the explicit capabilities in the FE code LS-DYNA [2]. It is a model of a 50thpercentile adult male vehicle occupant and contains approximately 150,000 elements. To studythoracic injuries, the responses of the THUMS were compared to several cadaver experiments.Then, a sensitivity study was performed to evaluate the influence of belt interaction and tissueparameters on the predicted thoracic response. Lastly, several candidates to predict rib cagefractures were compared in loading conditions relevant to frontal car crashes.The central nervous system controls the muscle contraction and was modeled using feedbackproportional, integral, and derivative (PID) control. The reference signal is a joint angledefining a body position. The neural delays, due to the time needed for the nerve signalsto travel back and forth to the central nervous system, and muscle activation dynamics areincluded. Firstly, this was applied to evaluate the response of the elbow joint comparedto volunteer experiments [3], and secondly, to compare passenger kinematics in autonomousbraking events. It was seen that by changing the controller gains, the model can can capturedifferences in the muscle response when the human is relaxed compared to tensed, which isimportant to study the difference between occupants who are or who are not aware of anoncoming accident.
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| 4. |
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| 5. |
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| 6. |
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| 7. |
- Khodaei, Hamid, 1982, et al.
(författare)
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Simulation of active skeletal muscle tissue with a transversely isotropic viscohyperelastic continuum material model
- 2013
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Ingår i: Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine. - : SAGE Publications. - 0954-4119 .- 2041-3033. ; 227:5, s. 571-580
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Tidskriftsartikel (refereegranskat)abstract
- Human body models with biofidelic kinematics in vehicle pre-crash and crash simulations require a constitutive model of muscle tissue with both passive and active properties. Therefore, a transversely isotropic viscohyperelastic continuum material model with element-local fiber definition and activation capability is suggested for use with explicit finite element codes. Simulations of experiments with New Zealand rabbit's tibialis anterior muscle at three different strain rates were performed. Three different active force-length relations were used, where a robust performance of the material model was observed. The results were compared with the experimental data and the simulation results from a previous study, where the muscle tissue was modeled with a combination of discrete and continuum elements. The proposed material model compared favorably, and integrating the active properties of the muscle into a continuum material model opens for applications with complex muscle geometries.
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| 8. |
- Olafsdottir, Jóna Marin, 1985, et al.
(författare)
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Passenger Kinematics and Muscle Responses in Autonomous Braking Events with Standard and Reversible Pre‐tensioned Restraints
- 2013
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Ingår i: IRCOBI Conference 2013. - 2235-3151. ; :IRC-13-70, s. 602-617
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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.
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| 9. |
- Östh, Jonas, 1983, et al.
(författare)
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A Method to Model Anticipatory Postural Control in Driver Braking Events
- 2014
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Ingår i: Gait and Posture. - : Elsevier BV. - 0966-6362. ; 40:4, s. 664-669
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Tidskriftsartikel (refereegranskat)abstract
- Human Body Models (HBMs) for vehicle occupant simulations have recently been extended with active muscles and postural control strategies. Feedback control has been used to model occupant responses to autonomous braking interventions. However, driver postural responses during driver initiated braking differ greatly from autonomous braking. In the present study, an anticipatory postural response was hypothesized, modelled in a whole-body HBM with feedback controlled muscles, and validated using existing volunteer data. The anticipatory response was modelled as a time dependent change in the reference value for the feedback controllers, which generates correcting moments to counteract the braking deceleration. The results showed that, in 11 m/s2 driver braking simulations, including the anticipatory postural response reduced the peak forward displacement of the head by 100 mm, of the shoulder by 30 mm, while the peak head flexion rotation was reduced by 18°. The HBM kinematic response was within a one standard deviation corridor of corresponding test data from volunteers performing maximum braking. It was concluded that the hypothesized anticipatory responses can be modelled by changing the reference positions of the individual joint feedback controllers that regulate muscle activation levels. The addition of anticipatory postural control muscle activations appears to explain the difference in occupant kinematics between driver and autonomous braking. This method of modelling postural reactions can be applied to the simulation of other driver voluntary actions, such as emergency avoidance by steering.
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| 10. |
- Östh, Jonas, 1983, et al.
(författare)
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Active muscle response using feedback control of a finite element human arm model
- 2012
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Ingår i: Computer Methods in Biomechanics and Biomedical Engineering. - : Informa UK Limited. - 1476-8259 .- 1025-5842. ; 15:4, s. 347-361
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Tidskriftsartikel (refereegranskat)abstract
- Mathematical human body models (HBMs) are important research tools that are used to study the human response in car crash situations. Development of automotive safety systems requires the implementation of active muscle response in HBM, as novel safety systems also interact with vehicle occupants in the pre-crash phase. In this study, active muscle response was implemented using feedback control of a nonlinear muscle model in the right upper extremity of a finite element (FE) HBM. Hill-type line muscle elements were added, and the active and passive properties were assessed. Volunteer tests with low impact loading resulting in elbow flexion motions were performed. Simulations of posture maintenance in a gravity field and the volunteer tests were successfully conducted. It was concluded that feedback control of a nonlinear musculoskeletal model can be used to obtain posture maintenance and human-like reflexive responses in an FE HBM.
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