Comparative Study of Hybrid Powertrain Strategies

Hybrid electric vehicles have the potential to reduce air pollution and improve fuel economy without sacrificing the present conveniences of long range and available infrastructure that conventional vehicles offer. Hybrid vehicles are generally classified as series or parallel hybrids. A series hybrid vehicle is essentially an electric vehicle with an on-board source of power for charging the batteries. In a parallel hybrid vehicle, the engine and the electric motor can be used to drive the vehicle simultaneously. There are various possible configurations of parallel hybrid vehicles depending on the role of the electric motor/generator and the engine.

In this paper, a comparative study of the drivetrains of five different hybrid vehicles is presented. The underlying design architectures are examined, with analysis as to the tradeoffs and advantages represented in these architectures. Where appropriate, comparisons to five popular non-hybrid vehicles are made to give the reader a sense of perspective. The primary drivetrain components of engine, transmission, electric machine, inverter, and battery pack are evaluated and changes to the user interface paradigm are highlighted. Based on the comparative study, hybrid drivetrain technology strategies for future vehicles are proposed.