Rollover Testing: Analysis of Steer Input Timing

Recent rollover resistance test results show discrepancies between vehicles steered with programmable steering machines and those steered by test drivers. This paper examines the differences in steering profiles and their effects on vehicle dynamics. For decades, test drivers have steered vehicles through rollover resistance test maneuvers. Human inputs, however, can cause variability from test to test. The National Highway Traffic Safety Administration (NHTSA) is currently performing rollover testing with steering machines in an effort to objectively rate the rollover resistance of passenger vehicles. The trapezoidal steer inputs are visibly different from human inputs and may be responsible for test differences. The roll rate feedback loop, which determines steer timing, may also affect vehicle response.