Cooperative optimization of speed planning and energy management for hybrid electric vehicles based on Nash equilibrium

Abstract

The longitudinal automatic driving of hybrid electric vehicles (HEVs) is a complex multi-objective problem, and the coupling relationship between speed planning and energy management is difficult to reveal using the commonly used hierarchical control algorithm. Thus, in this paper, a collaborative control strategy is proposed for cruise speed optimization and energy management of HEVs based on Nash equilibrium. The strategy in this paper can optimize the control of vehicle-level and hybrid-system-level at the same time. First, this paper builds the key component model of HEV under the Simulink environment, which lays the foundation for vehicle control. Then, a multi-objective problem-solving framework based on game theory is proposed aiming at the economy and safety of HEV cruising. Afterward, a weight factor adjustment method is proposed based on fuzzy logic to judge the brake/drive logic. Finally, the utility functions are used for coordinated control based on Nash equilibrium. The simulation results show that the control method proposed in this paper has improved in various aspects as compared with hierarchical model predictive control, including vehicle following, safety, and comfort. In addition, this strategy can significantly reduce energy consumption costs while meeting the cruise speed requirements of vehicles. In the whole driving cycle, the strategy proposed in this paper has a high termination of SOC and a fuel consumption reduction of 15.33%. It can better deal with the relationship between speed planning and torque distribution than the traditional hierarchical control method.