The aim of this study is to determine if the degradation of one or more dampers
of a passenger car with ABS leads to a statistically significant reduction of
vehicle safety. Therefore, a compact and a mid-size car are tested on a flat
test track and on an uneven test track by straight braking maneuvers at
different levels of damper degradation. Both test tracks are scanned using a 3D
laser scanner. For every level of damper degradation (on each test track) a new
set of tires is used, a preconditioning routine is applied and 30 successful
measurements are conducted to allow using statistical methods to evaluate the
results.
The results show that any level of damper degradation with each type of car and
test track leads to a significant increase in braking distance and, therefore,
to a significant reduction of vehicle safety. The braking distance extension
varies heavily with the level of damper degradation and the road properties. The
observed extensions range from a little more than 2% to more than 30% of the
braking distance of the intact state. However, the vehicle’s behavior does not
deteriorate linearly as the oil volume goes down. The longest braking distance
(when one damper is degraded) can already be at higher oil volumes, as this
study suggests. As one possible cause, the reduced functionality of the ABS at
asymmetrical levels of degradation is examined.
This is the first study that applies statistical methods to straight braking
distance measurements investigating damper degradation and offers the comparison
of 11 different configurations with 30 measurements each. Additionally, the
quality of the results is improved by the analysis of the properties of the two
used test tracks and the transparent preconditioning routines.