Optimal control of aftertreatment electric heaters for mild hybrid vehicles during cold start

Hybrid electric on-road vehicles are gradually replacing their fossil fuel counterparts. Meanwhile, exhaust aftertreatment systems integrate new degrees of freedom, for example, heating capabilities. Therefore, this paper proposes an optimal control method to minimize the fuel consumption and the tailpipe emissions of a mild hybrid electric vehicle (mHEV) equipped with an electric aftertreatment system heater. The optimal control of the heating unit is formulated using the Pontryagin maximum principle, from which a sub-optimal bang-bang strategy can be derived. Results are presented in simulation for an mHEV with a selective catalytic reduction system equipped with an electric heating device.