Abstract
Keywords:
HEV, Optimization, Control strategy, Single shaft parallel HEV, Double shaft parallel HEV
Abstract
Optimal control strategy is obtained for (1) single shaft parallel HEV and (2) double shaft parallel HEV. In order to find the optimal control strategy, optimization problems are defined, which find the optimal control variables to minimize the fuel consumption while satisfying the constraint equations. Scale factors in weighting the motor usage are selected as the control variables on how to distribute the demanded vehicle power into the electric motor and the internal combustion engine. Dynamic models of the HEV powertrain are represented with state space equations. The optimization problems are solved using the HEV performance simulator developed in MATLAB Simulink and the mathematical optimization algorithm, SQP which is based on FORTRAN for multi-variables design optimization. It is found that the optimal control strategy of the double shaft HEV provides better fuel economy than the single shaft HEV since the recuperation energy due to the regenerative braking can be increased by the engine off and clutch operation.