Multi-objective Optimization of Hybrid Electric Vehicle Equipped with Power-split Continuously Variable Transmission

This paper aims to find the efficient state of hybrid electric vehicle (HEV) by simultaneous optimization of the control strategy and the power train. The power transmission employed in this vehicle is a power-split continuously variable transmission (CVT) which uses several fixed ratio mechanisms. After describing this transmission, the rules of electric assist control strategy are introduced. A modification on this strategy is proposed to decrease the start/stop frequency of the engine and electric motor. Afterwards, an optimization on the HEV's power train size, power-split CVT and the control strategy is accomplished with the aim of minimizing the vehicle fuel consumption and emissions. The optimization results are some Pareto-optimal points which are tradeoff solutions between fuel consumption and emissions. Finally, in order to intuitively demonstrate the optimality of the optimization results, the Pareto points for the case of considering two objectives are shown.