07 Fakultät Konstruktions-, Produktions- und Fahrzeugtechnik

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    On the validation of human body models with a driver-in-the-loop simulator
    (2018) Kempter, Fabian; Fehr, Jörg; Stutzig, Norman; Siebert, Tobias
    For the development of modern integrated safety systems, standard simulation models of anthropometric test devices, often called crash test dummies, are inappropriate for Pre-Crash investigations due to missing activation possibilities, tuned characteristics for one specific accident scenario and high passive stiffness properties. To validate safety concepts getting active prior to the crash new tools like suitable virtual models of human occupants are required. Human Body Models (HBM) provide a higher biofidelity and can be equipped with active muscle elements enabling different muscle activation strategies. To improve the muscle activation strategy and the stiffness properties of active HBMs, validation processes on the basis of low-acceleration experiments are inevitable. In contrast to Post Mortem Human Surrogates only low-severity tests can be performed with real human subjects. This paper presents the workflow of a validation process based on an academic scale Driver-in-the-Loop (DiL) simulator in combination with a synchronized measurement chain consisting of an Optitrack stereo vision and an electromyography detection system.
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    Dynamic human body models in vehicle safety : an overview
    (2023) Fahse, N.; Millard, M.; Kempter, F.; Maier, S.; Roller, M.; Fehr, J.
    Significant trends in the vehicle industry are autonomous driving, micromobility, electrification and the increased use of shared mobility solutions. These new vehicle automation and mobility classes lead to a larger number of occupant positions, interiors and load directions. As safety systems interact with and protect occupants, it is essential to place the human, with its variability and vulnerability, at the center of the design and operation of these systems. Digital human body models (HBMs) can help meet these requirements and are therefore increasingly being integrated into the development of new vehicle models. This contribution provides an overview of current HBMs and their applications in vehicle safety in different driving modes. The authors briefly introduce the underlying mathematical methods and present a selection of HBMs to the reader. An overview table with guideline values for simulation times, common applications and available variants of the models is provided. To provide insight into the broad application of HBMs, the authors present three case studies in the field of vehicle safety: (i) in-crash finite element simulations and injuries of riders on a motorcycle; (ii) scenario-based assessment of the active pre-crash behavior of occupants with the Madymo multibody HBM; (iii) prediction of human behavior in a take-over scenario using the EMMA model.
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    Implementation and validation of the extended Hill-type muscle model with robust routing capabilities in LS-DYNA for active human body models
    (2017) Kleinbach, Christian; Martynenko, Oleksandr; Promies, Janik; Häufle, Daniel F. B.; Fehr, Jörg; Schmitt, Syn
    In the state of the art finite element AHBMs for car crash analysis in the LS-DYNA software material named *MAT_MUSCLE (*MAT_156) is used for active muscles modeling. It has three elements in parallel configuration, which has several major drawbacks: restraint approximation of the physical reality, complicated parameterization and absence of the integrated activation dynamics. This study presents implementation of the extended four element Hill-type muscle model with serial damping and eccentric force-velocity relation including Ca2+ dependent activation dynamics and internal method for physiological muscle routing.
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    Role of rotated head postures on volunteer kinematics and muscle activity in braking scenarios performed on a driving simulator
    (2022) Kempter, Fabian; Lantella, Lorena; Stutzig, Norman; Fehr, Jörg; Siebert, Tobias
    Occupants exposed to low or moderate crash events can already suffer from whiplash-associated disorders leading to severe and long-lasting symptoms. However, the underlying injury mechanisms and the role of muscle activity are not fully clear. Potential increases in injury risk of non-nominal postures, i.e., rotated head, cannot be evaluated in detail due to the lack of experimental data. Examining changes in neck muscle activity to hold and stabilize the head in a rotated position during pre-crash scenarios might provide a deeper understanding of muscle reflex contributions and injury mechanisms. In this study, the influence of two different head postures (nominal vs. rotation of the head by about 63 ± 9° to the right) on neck muscle activity and head kinematics was investigated in simulated braking experiments inside a driving simulator. The braking scenario was implemented by visualization of the virtual scene using head-mounted displays and a combined translational-rotational platform motion. Kinematics of seventeen healthy subjects was tracked using 3D motion capturing. Surface electromyography were used to quantify muscle activity of left and right sternocleidomastoideus (SCM) and trapezius (TRP) muscles. The results show clear evidence that rotated head postures affect the static as well as the dynamic behavior of muscle activity during the virtual braking event. With head turned to the right, the contralateral left muscles yielded higher base activation and delayed muscle onset times. In contrast, right muscles had much lower activations and showed no relevant changes in muscle activation between nominal and rotated head position. The observed delayed muscle onset times and increased asymmetrical muscle activation patterns in the rotated head position are assumed to affect injury mechanisms. This could explain the prevalence of rotated head postures during a crash reported by patients suffering from WAD. The results can be used for validating the active behavior of human body models in braking simulations with nominal and rotated head postures, and to gain a deeper understanding of neck injury mechanisms.