Energy management strategies for a parallel hybrid electric powertrain: Fuel economy optimisation with driveability requirements

More efficient deployment of natural resources and reduction of emissions into the atmosphere are two of the most pressing problems for modern society. Hybrid powertrains and continuously variable transmissions are two technical solutions that could overcome the new challenges. The additional complexity they introduce and the necessity to meet customer expectations in terms of performance and driveability call for more sophisticated control solutions to be adopted. This paper reviews the driveability issue to underline the constraints it imposes on possible control architectures. It then classifies the typical control approaches available. A rule based controller is developed for a parallel hybrid powertrain with an infinitely variable transmission. The control features that improve driveability are explained. The fuel economy performance is demonstrated in simulation and an improvement is achieved with respect to a baseline non-hybrid powertrain with the same transmission topology. A dynamic programming investigation is finally performed in order to investigate optimal control trajectories over legislative drive cycles and the results analysed as a contribution to the knowledge base for controller formulation