Hybrid Energy Management Strategy Based on Fuzzy Logic and Optimal Control for Tri-Actuated Powertrain System

In this paper, an efficient energy management strategy (EMS) of a specific multi-hybrid plug-in electric bus is designed and validated using high-fidelity TruckMaker software simulation. The studied bus is equipped with a tri-hybrid powertrain in which traction torque is produced by three distinct energy sources (internal combustion engine, hydraulic accumulator, and battery). To manage the complex operation of this hybrid powertrain smoothly and efficiently, an EMS composed of two control layers combining fuzzy logic and adaptive optimal control is proposed. The main purpose of this control strategy is the coordination of these multiple energy sources while minimizing the fuel consumption and ensuring smooth torque transitions between the motors. This last-mentioned benefit is quite important, since smooth torque transitions helps to reduce power loss in the hydraulic system and ensure reliability of the powertrain. In addition, the proposed strategy is designed so that it respects the intrinsic constraints of the powertrain components and to deal with the uncertainties on the driving conditions when controlling the hybrid powertrain system.