Correlating Dynamometer Testing to In-Use Fleet Results of Plug-In Hybrid Electric Vehicles

The Untied States Department of Energy is engaged in the research, development and deployment of PHEV technology through the “Advanced Vehicle Testing Activity.” In this program, data has been collected from a Prius PHEV converted by Hymotion^TM using industry standard dynamometer testing procedures and from in-use operation of fleets. Differences in fuel-only consumption rates observed in the on-road data compared to the dynamometer results were fairly dramatic. Correlations of the driving style and conditions of dynamometer testing and on-road conditions were made possible by comprehensive onroad loggers. A model was developed to infer driving intensity from the on-road dataset from data load measurement during dynamometer testing. The reasons for the shortfall are detailed in the paper. They range from driver aggressiveness, accessory loads, ambient temperature (weather), and the high sensitivity the control system exhibits with increased acceleration pedal demand and higher average cruising speeds.