Gear shifting and engine on/off optimal control in hybrid electric vehicles using partial outer convexification

摘要

The hybrid electric powertrain provides various degrees of freedom to optimize fuel efficiency. Along with the optimal torque split between propulsion machines, the optimal gear choice and the decision to turn the engine on/off inherently influence efficiency as well. The latter aspect introduces additional control variables into an optimization problem which is then usually formulated as a mixed-integer optimal control problem. The computational complexity resulting from integer optimization makes the centralized optimization schemes intractable for real-time applications. In this article, we formulate and treat a distributed optimization problem in order to attain the optimal torque split along with the optimal gear choice and the decision for engine on/off. Therefore a partial outer convexification method is applied to reformulate a mixed integer energy management problem into a two-layer predictive control problem which is efficiently solved.