Torque control strategy incorporating charge torque and optimization for fuel consumption and emissions reduction in parallel hybrid electric vehicles

This paper proposes a torque control strategy to charge the battery of parallel hybrid electric vehicles (HEVs), in which the charge torque by an internal combustion engine (ICE) is newly introduced. In our previous paper, only regenerative braking was used to charge the battery. However, this is not sufficient for CO2 and NOx emissions reduction, and thus, a more effective energy management system (EMS) should be developed. To maintain the battery state of charge (SOC), a target SOC is also introduced in the charge torque. In addition, a CHARGE driving condition where the charge torque by the ICE is generated is newly proposed. By introducing the CHARGE driving, the ICE driving region on torque-engine speed plane was reduced. As a result, a greater reduction in CO2 and NOx emissions is expected. Based on the EMS proposed in our previous papers, an EMS incorporating the CHARGE driving is developed. Through typical driving cycles, the validity of the proposed EMS algorithm incorporating the CHARGE driving is examined.