A Predictive Supervisory Controller for an HEV Operating in a Zero Emission Zone

Low Emission Zones have been designated in the European Union where entry of vehicles causing high emission is regulated. However, existing energy management based control strategies for HEVs do not consider such constraints while computing the optimal torque split ratio (TSR). In this paper, a predictive energy management strategy for a route having a Zero Emission Zone (ZEZ)is proposed. Under this strategy, the required SOC at the entry point of ZEZ for the HEV to cross it in EV mode is estimated where emission is also reduced gradually to zero at its entry. To achieve this, a cost function is designed considering the equivalent fuel consumption rates for different torque speed combinations and the relative distance of the vehicle from the entry point of the ZEZ. This cost function is minimized under various constraints of parameters to satisfy the net tractive torque demand to finally yield the required TSR at each instant. Results obtained using a validated HEV model in simulation environment under drive cycles having a ZEZ demonstrate the effectiveness of the proposed strategy when evaluated under various performance parameters. The performance of HEV under different ambient temperatures has also been studied.