Optimal control of hybrid electric vehicles with power split and torque split strategies: A comparative case study

In designing control strategies to optimize fuel consumption, driveability and other objectives for hybrid electric vehicles (HEVs), one can choose to use either power split or torque split as one of the control variables. While both approaches have been employed and documented, no systematic study has been reported that illuminates what implications this choice might have in terms of HEV performance, system robustness, and control strategy design and implementation complexity. This work aims to develop a case study that explores this degree of design freedom and to quantify any differences that this control design selection might impart on a given HEV architecture. Using a validated HEV model, we will derive optimal operating strategies using dynamic programming for two cases: one uses power split and other torque split. Performance metrics of fuel consumption as well as the computational complexity associated with the two different strategies will be assessed.