Motor Selection Criteria and Potentials of Electrified All Wheel Drive Concepts for Passenger Cars by Add-on Wheel Hub Motors on the Rear Axle

As the age of crude oil gradually finishes and political arrangements all over the world force a continuous reduction of global carbon dioxide (CO₂) emissions, energy efficiency and energy sustainability become worldwide a major challenge for automotive industry. The ambitious European goal of a fleet average emission for all new cars of 130 g/km CO₂ by 2012 afford an overall energy efficiency increase of the entire powertrain topologies. One way to come up to this challenge is surely the electrification of powertrain systems. Nowadays, hybrid electric vehicles (HEV) represent one of the most promising technologies that combine the advantages of high performance, high fuel efficiency and low emissions in combination with a long operating range. In literature exists lots of investigations concerning the requirements of different powertrain topologies along with the corresponding individual requirements of electric motor types. Nevertheless an ideal electric traction motor cannot be given. The current research topic concentrates on motor selection criteria and tries to represent the individual pros and cons of induction motors and synchronous machines with interior mounted magnets for their use within a parallel diesel hybrid powertrain topology. The electric motor types are used as wheel hub motors on the rear axle representing an electrical add-on all-wheel-drive concept for passenger cars. The comparison of the two motor types is given by design and operational characteristics. The article tries to give an overview on specific electric motor selection issues, additional functionalities, fuel consumption and energy saving potentials for the investigated electric motor types and powertrain topologies.