Abstract
The changes in tire pressure will cause braking force to significantly vary due to the change in the tire-to-road contact during hard braking. The most important reason of this issue is the changes in road contact because of the changes in the vertical stiffness and slip stiffness of tire, as tire pressure varies. Therefore, in this study, it was aimed to investigate the effects of the tire pressure on anti-lock brake system (ABS) control performance through vertical and slip stiffness of tire. For this, first, the friction coefficient extended to tire pressure was integrated into the braking dynamics equations using the magic tire model. In this way, the effects of tire pressure were analytically revealed on braking performance. Then, taking into account the theoretical results, ABS braking tests were carried out with three different tire pressures: higher (38 psi) and lower (25 psi) tire pressure than the nominal (33 psi) tire pressure. In experimental studies, tests were carried out for braking initial speeds 30 and 60 km/h with the same tire pressures in µ-jump road conditions. In this way, the effects of the tire pressure were experimentally investigated on control performance of ABS under critical road conditions. At 33 psi tire pressure, the highest brake pressure was observed when switching to wet roads. At 25 psi tire pressure, the brake pressure did not build up in time. This showed that low tire pressure causes brake pressure to increase with a delay. On the slippery part, the lock-up limit is closer at 38 psi tire pressure. Therefore, it was seen that the decrease and increase in tire pressure have great effect on control performance of ABS under µ-jump road conditions.
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