Modified Approach to Accurately Measure Height of Force (HOF)

Crash compatibility has attracted lot of attention in recent years due to the proliferation of light trucks in the United States, which are typically taller and heavier than passenger cars. The inherent issue is the safety of the occupants in the smaller vehicle when involved in a collision with the larger vehicle. Research is ongoing to address self protection and partner protection in both vehicles for various impact scenarios. Several numeric measures have been proposed to assess crash compatibility between two vehicles. One of the measures under investigation is the Average Height of Force (AHOF). This metric is a measure of the vertical centroid of forces exerted by the vehicle on a flat rigid barrier surface. Several studies in the past have concluded that there are large inherent errors in the AHOF measure. One of the main factors influencing the error in this measure is the size of the load cell on the barrier face.

In this study, the error bounds in AHOF as a function of barrier load cell size are computed using computer simulations. Three different vehicle types, compact car, SUV and a mini-van are used in this study. The load cell wall is raised above the ground in fixed increments creating different height overlaps with the frontal structure of a vehicle in order to estimate the AHOF error against the height of the barrier. A modified approach using multi-axis load cells is presented which can accurately measure the AHOF. This research will enable us to specify barrier designs that can accurately measure AHOF and use this metric to investigate the effects of height of force matching in the vehicle fleet.