Industrialisation of a Finite Element Active Human Body Model for Vehicle Crash Simulations
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Typ
Examensarbete för masterexamen
Master Thesis
Master Thesis
Program
Maskinteknik 300 hp (civilingenjör)
Publicerad
2015
Författare
Eliasson, Erik
Wass, Jacob
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
The Total HUman Model for Safety (THUMS), developed by Toyota, is a numerical finite element model of the human body to enable studies of vehicle accidents by computer aided simulations. Recently a new muscle package, referred to as the SAFER Active Human Body Model (AHBM) which provides the THUMS with active muscle response, was developed in a PhD project at Chalmers University of Technology. This enable studies of pre-crash events, such as emergency braking. The objective of this thesis is to industrialise the SAFER AHBM used by the automotive industry to make it a reliable tool in development. Industrialisation of the model, in this context, includes making the model easier to use, solving numerical instability issues when entering the crash phase, reducing computational time, and calibration and validation of the industry version of the SAFER AHBM. A method for positioning the SAFER AHBM was developed to aid the user when evaluating new driving scenarios. The positioning is conducted via a constraint based simulation where the model is placed in the desired position by prescribing nodal displacements. The model was also calibrated and validated with respect to experimental data from volunteers in a pre-crash scenario. Calibration was done using a radial basis function meta-model which was sampled by two Design of Experiment (DOE) iterations consisting of 48 and 24 simulations, respectively. The parameter test matrix was constructed using a space-filling design algorithm with the controller gains as parameters. The goal functions for the calibration and validation were head rotation, head vs. sternum relative X-displacement, belt force, steering wheel force and frequency content of all responses. Positioning of the model is done with high precision by prescribing displacements (rotations) for key nodes in the model, e.g. ankles, wrists, head, neck, spine and hips. After the simulation is completed the user has the possibility to extract element stresses which can be used as input to a new simulation starting from the positioned state. This enables both seat squashing and positioning to be done in one simulation. Calibration of the model resulted in seventeen new controller gains for the PID-control system which improved the model response compared to experimental data. The model response now is within one standard deviation for all the goal functions (except head rotation for which it over rotates slightly) and exhibits a stable response towards small perturbations. It was found that the muscle control system is very sensitive and easily experiences closed loop instability, especially for variations in the derivative gain. The model was also shown to complete a full pre-crash crash simulation without termination due to numerical instabilities.
Beskrivning
Ämne/nyckelord
Transport , Fastkroppsmekanik , Farkostteknik , Transport , Solid mechanics , Vehicle Engineering