Volunteer Kinematics and Muscle Activity in Dynamic Events Representative of Pre-crash Scenarios, Evaluation Data for Human Body Models

Licentiate thesis, 2018

Advanced integrated safety technologies in modern cars such as collision avoidance intervention and pre-crash activated restraint systems involve comprehensive research on how vehicle occupants respond to these systems in pre-crash situations. Human Body Models (HBMs) are mathematical tools developed to predict human responses and injury outcomes in different pre-crash and in-crash situations. In recent years, introducing muscular activation strategies into the HBMs has enhanced the accuracy of model responses in these situations. The development and validation of biofidelic HBMs intended for studies of pre-crash situations require information on kinematics and muscle activation of vehicle occupants in similar circumstances. This information can be obtained through volunteer experiments representative of pre-crash loading situations. To provide validation data for HBMs, this thesis investigates volunteer responses in evasive manoeuvres potentially occurring prior to a crash.

Kinematics and muscle responses of front-seat male passengers travelling at 73 km/h together with vehicle dynamics and boundary conditions were measured in the following scenarios: autonomous lane change and autonomous lane change combined with braking, each with two belt configurations; standard and reversible pre-pretensioner belts. The surface electromyography method was used to measure muscle activity and the data was then normalised using maximum voluntary contraction (MVC) values. Transformation of coordinates corresponding to several film targets attached to the head and torso was used to calculate head centre of gravity (CoG) and upper torso kinematics in 3-D. All data were presented in corridors comprising mean ± one standard deviation. Muscle activity as well as head and torso motion were influenced by type of the manoeuvre and the belt configuration used. In addition to lateral motion observed in lane changes, forward displacement of the head and upper torso were also observed in lane changes with braking. Differences in activation time and amplitude between muscles in the right and left side of the body with respect to the vehicle’s lateral motion were noted. Compared to the standard belt, pre-tensioning the seat belt prior to the manoeuvres reduced lateral and forward displacement of head and upper torso. Seat belt pre-tensioning was also associated with earlier muscle activation onset and significantly lower activation amplitude for specific muscles.

The data provided in this thesis can be used for further enhancement and validation of HBMs capable of simulating muscles activity in simulation of pre-crash situations, involving both sagittal and lateral loading. In addition to the volunteer data being suitable for directly assessing the design of integrated safety systems, the HBMs validated against the volunteer data can facilitate the prediction of injury outcomes in crashes that may follow evasive manoeuvres. As such, the HBMs would be applicable in the optimisation of integrated safety technologies targeted at the reduction of injuries of vehicle occupants. Further studies identifying responses of other occupant categories based on seated position, gender, age, stature and BMI are needed for subject-specific optimisation of safety systems in modern cars. Furthermore, studies on volunteer responses in other types of omnidirectional loading scenarios as well as the effect of being unprepared compared to anticipatory or voluntary responses, can help understand human motor control strategies specific to pre-crash situations.