Computer Simulation of Steer-Induced Rollover Events Via SIMON 2011-01-1122

This study examines through computer simulation the reconstruction of on-road vehicle rollover accidents induced by a driver steering maneuver. The three-dimensional vehicle dynamics software package SIMON is used to model a set of four test vehicles as six degree-of-freedom sprung masses with up to five degrees-of-freedom for each unsprung mass. The performance of the simulator's physics model, in the context of accident reconstruction, is evaluated through correlation with full-scale vehicle rollover tests. Of specific interest to this study was simulation of the trip phase of the vehicle's motion.

The correlation parameters include vehicle trajectory, speed, heading angle, yaw rate, roll angle, roll rate and lateral acceleration. SIMON's capacity to accurately model the physics of a test vehicle's suspension and tire kinetics in the pre-trip and trip phases of motion is evaluated by modeling a set of four instrumented full-scale tests of steering-induced rollovers.

This study demonstrated that, with appropriate tire-ground friction values, accurate modeling of vehicle dynamics parameters and rollover initiation can be achieved. Further, up until wheel liftoff, the simulation also produced close matching of the vehicle trajectory and orientation, and achieved good overall agreement with measured vehicle responses. The average increase in the default tire-ground friction values in SIMON to effect trip initiation in the simulations of the four rollover tests was 27% (14% - 35%). It was also noted in simulations of two of the tests that the phasing of steer input to vehicle response was shorter than that of the test vehicle. These observations suggest the need for additional empirical tire friction data and improved steering compliance data in the HVE vehicle database for rollover simulations, particularly in the case of light trucks, SUV's and minivans.