Influences of Controlling Tire Inflation Pressure on Handling Characteristics of Off-Road Vehicles

This paper investigates the effect of tire inflation pressure on the directional stability of All Wheel Drive (AWD) vehicles during high-speed off-road maneuvers over different soft terrains such as loam, sand and clay. For this purpose, a fourteen-degrees-of-freedom (14-DOF) full parametrized vehicle model is employed and numerically simulated in MATLAB/Simulink environment to represent the full vehicle body dynamics such as roll, yaw and pitch motions. In order to calculate tire forces and moments over deformable terrains, the AS²TM Soft Soil Tire Model was successfully integrated with the vehicle model which enabled the possibility of changing tire pressure and consequently investigate its effect on vehicle dynamics. Numerous simulations are carried out to examine vehicle handling in case of different tires inflation pressure during steady state turning maneuvers such as ramp steer input. Simulation results at both moderate and high-speed turning maneuvers showed that changing tire inflation pressure is significantly affecting vehicle handling characteristics such that it can be changed from understeer to oversteer behavior for excessively reduced tire inflation pressure.

The paper is also presenting a proposal for a Central Tire Inflation System (CTIS) which is verified using laboratory test-rig. The proposed CTIS is mainly intended to use a professional control system using Programmable Language Control (PLC). The control system is based on two analog pressure sensors which are used as feedback of the real tire inflation pressure. The driver can control tire pressure either manually by selecting the tire pressure value or automatically by specifying the soil type. The driver interface system is implemented using ten inches touch screen which is also used to show the tire pressure instantaneously. The proposed CTIS system is effective, reliable, inexpensive and request no modifications in vehicle axles.