A study on model fidelity for model predictive control based obstacle avoidance in high speed autonomous ground vehicles
ABSTRACT This paper investigates the level of model fidelity needed in order for a model predictive control (MPC) based obstacle avoidance algorithm to be able to safely and quickly avoid obstacles even when the vehicle is close to its dynamic limits. The context of this work is large autonomous ground vehicles that manoeuvre at high speed within unknown, unstructured, flat environments and have significant vehicle dynamics related constraints. Five different representations of vehicle dynamics models are considered: four variations of the two degrees of freedom (DoF) representation as lower fidelity models and a fourteen DoF representation with combined slip Magic Formula tyre model as a higher fidelity model. It is concluded that the two DoF representation that accounts for tyre nonlinearities and longitudinal load transfer is necessary for the MPC based obstacle avoidance algorithm in order to operate the vehicle at its limits within an environment that includes large obstacles. For less challenging environments, however, the two DoF representation with linear tyre model and constant axle loads is sufficient.