Abstract: The temperature and efficiency of the three way catalytic converters of hybrid electric vehicle may be decreased and emission is deteriorated because of the engine’s frequent start/stop during mode switching process. In order to minimize the fuel consumption and emission from the outlet of catalytic converter of full hybrid electric vehicles in the NEDC cycle, based on Pontryagin minimum principle the cost function relating the battery’s state of charge and the temperature of three-way catalytic converter is established and solved to get the extreme value, then the global optimum real-time control strategy is obtained in order to minimize the fuel consumption and emission from the outlet of catalytic converter of full hybrid electric vehicles in the NEDC cycle. The control strategy during braking and stopping operations is simplified to analytically compare the effects of the control strategies with and without engine’s start-stop optimum on the fuel consumption and emission. Dynamic model of the vehicle is established on the platform of Matlab / Simulink to validate the optimum control strategy and to compare the optimum control strategy with Rules control strategy. The results show that the optimum control strategy can optimize the engine’s start-stop with the purpose of significantly speeding up the catalytic converter’s light-off. The vehicle’s fuel economy and emission from the outlet of three way catalyst are optimized from global perspective. Compared to the Rules control strategy, each index in Pareto solution set is improved effectively.

Key words: Engine start-stop, Full hybrid electric vehicle, Optimum control, Three way catalyst