Nonlinear dynamics modeling and rollover control of an off-road vehicle with mechanical elastic wheel

Abstract

Nonlinear dynamics modeling and rollover stability control are the indispensable parts of automotive active safety research, especially for the military off-road vehicle with some special demands. The nonlinearity of the vehicle model refers to the nonlinear tire characteristics. By simplifying the structure of non-pneumatic mechanical elastic wheel (ME-Wheel),the change of half long grounding mark, lateral distribution stiffness along with vertical load is studied, and the corresponding fitting model is established. Then, a corrected tire brush model is constructed and a longitudinal and lateral force expression is set up. Finally, a nonlinear 8-DOF vehicle model for an off-road vehicle with ME-Wheel was built up and an active suspension control system based on rollover prediction and Fuzzy proportional-integral-derivative (PID) is designed for rollover prevention, which utilizes a predictive load transfer ratio (PLTR) as the rollover index and the Fuzzy PID controller activates only when the potential for rollover is significant as measured by the PLTR. The effectiveness of proposed tire model and vehicle model are verified by virtual simulations and experiments. Simulation results during single lane-change and fishhook maneuvers show that the PLTR index can provide a time-advanced measure of rollover propensity and Fuzzy PID anti-rollover control algorithm based on PLTR index has better stability of roll than load transfer ratio index.