Active Muscle Responses in a Finite Element Human Body Model

Licentiate thesis, 2010

The development of automotive safety systems is moving towards an integration of systems that are active before and during an impact. Consequently, there is a need to make a combined analysis of both the pre-crash and the in-crash phases, which leads to new requirements for Human Body Models (HBMs) that today are used for crash simulations. In the pre-crash phase the extended duration makes the active muscle response a factor that must be taken into account in the HBM to correctly simulate the human kinematics. In this thesis, the active muscle response is modeled using a feedback control strategy with Hilltype line muscle elements implemented in a Finite Element (FE) HBM. A musculoskeletal modeling and feedback control method was developed and evaluated, with simulations of the human response to low level impact loading of the arm in flexion-extension motion. Then, the method was implemented to control trunk and neck musculature in an FE HBM, to simulate the occupant response to autonomous braking. Results show that the method is successful in capturing active human responses and that a variety of responses in volunteer tests can be captured by changing of control parameters. The proposed method, to model active muscle responses in an FE HBM using feedback control, makes it possible to conduct a pre-crash simulation in order to determine the initial conditions for an in-crash simulation with an FE HBM. It also has a large potential to extend the use of FE HBMs to the simulation of combined pre-crash and in-crash scenarios, crash scenarios of longer duration such as roll-over accidents and, eventually, multiple events.