Influence of Driver Input on the Touchdown Conditions and Risk of Rollover in Case of Steering Induced Soil-Trip Rollover Crashes 2016-01-1514

Some rollover testing methodologies require specification of vehicle kinematic parameters including travel speed, vertical velocity, roll rate, and pitch angle, etc. at the initiation of vehicle to ground contact, which have been referred to as touchdown conditions. The complexity of the vehicle, as well as environmental and driving input characteristics make prediction of realistic touchdown conditions for rollover crashes, and moreover, identification of parameter sensitivities of these characteristics, is difficult and expensive without simulation tools. The goal of this study was to study the sensitivity of driver input on touchdown parameters and the risk of rollover in cases of steering-induced soil-tripped rollovers, which are the most prevalent type of rollover crashes. Knowing the range and variation of touchdown parameters and their sensitivities would help in picking realistic parameters for simulating controlled rollover tests. Additionally, understanding the sensitivity of the risk of rollover could potentially aid in developing countermeasures to prevent rollover. Monte Carlo simulations were performed using two multibody models (sedan and pickup) by varying the driving inputs (speed, steer angle, steer rate) for typical driving maneuvers. Linear regression models were used to study the sensitivity of driving input to touchdown parameters and logistic regression models were built to analyze the risk of rollover for given driver inputs. Analysis of Variance (ANOVA) from the linear regression models showed that the initial travel speed had the most prominent effect on the speed of the vehicle and the pitch angle and yaw rate were not sensitive to driver input. The risk of rollover was a nonlinear function of driving inputs and increased with the initial travel speed of the vehicle. For a given steer angle, higher steer rates further increased the risk of rollover. In a two steer maneuver (pattern A) increase in the first steer angle resulted in an increased risk of rollover.