Muscle Responses in Dynamic Events. Volunteer experiments and numerical modelling for the advancement of human body models for vehicle safety assessment

Sammanfattning: 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.