A novel conservative dynamics envelope of vehicle lateral stability under different tire characteristics

Abstract

This paper proposes a dynamic stability envelope based on safety maneuver margin to estimate the lateral stability of nonlinear vehicle systems with different tire characteristics (i.e. understeering (UN) and oversteering (OV) vehicles). Firstly, this study employs phase portraits and handling diagrams to investigate the number of equilibrium points and the evolution trend of state variables under various manipulation conditions. Subsequently, the nonlinear bifurcation theory is applied to analyze the characteristics of the vehicle equilibrium, aiming to derive the safe maneuver margin of the vehicle and restrict the vehicle instability. Within this proposed margin, the stability of each point of the nonlinear system is analyzed using the local linearization method. Simultaneously, a more conservative estimate of the vehicle handling stability is further obtained by applying stability criteria, resulting in the dynamic stability envelope, which ensures vehicle stability. Finally, the reliability of the dynamic stability envelope results based on the safety maneuver margin is validated under sine-with-dwell conditions (SDC) and steady-state cornering driving scenarios (SSC). The simulation results indicate that maintaining an appropriate understeering range keeps the vehicle stable.