TERRAMECHANICS IMPACT OF THE WHEEL NORMAL REACTION ON MOBILITY AND STEERABILITY MARGINS

The normal reaction force in the tire-soil patch is a continuously changing wheel parameter. When a vehicle moves over uneven ground, motion in the vehicle’s sprung and unsprung masses produce dynamic shifts in the magnitude of the load transmitted to the ground. With the damping force controlled for better ride quality, tight constraining of the sprung mass motion may lead to significant dynamic changes of the normal load. At excessive loads, the wheel can dig into the soil. Considerably reduced loads can negatively impact vehicle steerability and diminish traction performance. The purpose of this paper is to develop a method that allows for establishing boundaries of the dynamic normal reaction in the tire-soil patch on uneven terrain. The boundary constraints are considered for both maximum and minimum values to establish conditions for mobility and steerability. Using differential equations describing the motion two masses of a single-wheel module representing a vehicle corner, an inverse dynamics-based method is developed to recover a time history of the dynamic normal reaction of the wheel for assigned kinematics characteristics of the sprung mass and wheel longitudinal dynamics, and given stochastic characteristics of the terrain profile.

Citation: J. Paldan, V. Vantsevich, D. Gorsich, J. Goryca, A. Singh, L. Moradi, “Terramechanics Impact of the Wheel Normal Reaction on Mobility and Steerability Margins”, In Proceedings of the Ground Vehicle Systems Engineering and Technology Symposium (GVSETS), NDIA, Novi, MI, Aug. 10-12, 2021.