Coordinated control of path tracking and energy optimization for in-wheel motor drive electric buses with velocity estimation

Abstract

Accurate velocity estimation plays a significant role in improving path tracking performance. Meanwhile, for in-wheel motor drive electric buses (IWMEBs), how to tradeoff the energy optimization and torque distribution in path tracking is also a challenging task. To address the above issues, a hierarchical control framework is proposed in this paper for IWMEBs based on nonlinear model predictive control (NMPC), under which a modular nonlinear observer is designed to achieve accurate velocity estimate. The framework can be divided into two layers. In the upper layer, a modular nonlinear observer is designed to estimate the longitudinal and lateral velocities, considering the dependence of path tracking control on vehicle states. By replacing the tire model with the estimated longitudinal and lateral forces, the errors caused by the inaccurate parameters and modeling can be reduced. In the lower layer, a coordinated control method is proposed to realize the accurate path tracking while minimizing the energy consumption based on NMPC. By integrating tracking error, energy consumption and dynamic demand of IWMEB into an objective function, the coordinated control of path tracking and energy optimization is accomplished. The comparison simulation is implemented via Trucksim-Simulink joint simulation, whose results demonstrate that the proposed hierarchical control framework is effective and its performance is satisfactory.