Estimation of Steady State Rollover Threshold for High Capacity Transport Vehicles using RCV Calculation Method

Abstract

The rollover stability of high capacity transport (HCT) vehicles depends on multiple phenomena which result in lateral and vertical shift of the vehicle center of gravity and consequently in the load transfer from inner side tires to outer side tires. Vehicles' roll stability depends on the equilibrium between overturning and restoring moments. When overturning moments become governing, vehicle looses its stability and rolls over. Some of the design parameters which determine the roll stability are the height of center of gravity, track-width, suspension and tire compliance, axle and suspension roll stiffness, fifth-wheel compliance and frame exibility. United Nations Economic Commission for Europe (UNECE) Regulation 111 approves vehicles either by tilt table test or a calculation method, which is theoretical way to determine steady-state rollover threshold (SRT). Tilt table test is a good method but limited by the size of the test bed which makes it less preferable for long vehicle combinations with more than one articulation joints and the most preferable way to determine SRT is through a calculation method. However, calculation method involves number of non-validated parameters and simplified equations, which generally predicts higher SRT value than the actual. This overestimation can lead to rollover situation even within safe predicted zone. This study presents a plausible physical interpretation of UNECE111 calculation method to identify its assumptions and simplifications. An alternative Roll Compliant Vehicle (RCV) method is proposed, which includes a more sophisticated approach of compliances influence on roll stability and provides a direct comparison with UNECE111. The SRT value obtained from UNECE111 and RCV methods are then compared with tilt table tests for certain vehicle combinations to determine the degree of UNECE111's SRT overestimation within the study.