Impact of Supervisory Control on Criteria Tailpipe Emissions for an Extended-Range Electric Vehicle 2012-01-1193

The Hybrid Electric Vehicle Team of Virginia Tech participated in the three-year EcoCAR Advanced Vehicle Technology Competition organized by Argonne National Laboratory, and sponsored by General Motors and the U.S. Department of Energy. The team established goals for the design of a plug-in, range-extended hybrid electric vehicle that meets or exceeds the competition requirements for EcoCAR. The challenge involved designing a crossover SUV powertrain to reduce fuel consumption, petroleum energy use, regulated tailpipe emissions, and well-to-wheel greenhouse gas emissions. To interface with and control the hybrid powertrain, the team added a Hybrid Vehicle Supervisory Controller, which enacts a torque split control strategy.

This paper builds on an earlier paper [1] that evaluated the petroleum energy use, criteria tailpipe emissions, and greenhouse gas emissions of the Virginia Tech EcoCAR vehicle and control strategy from the 2^nd year of the competition. The Year 2 control strategy was further refined to reduce tailpipe emissions and fuel consumption based on chassis dynamometer testing results gathered during Year 3 of the competition. Criteria tailpipe emissions, such as carbon monoxide, oxides of nitrogen, and hydrocarbons, were touched on briefly in the previous paper but not in depth. This paper presents the results from an empirical study of the impact of changes in the hybrid supervisory control strategy on emissions and energy consumption, and evaluates the success of the changes made to the control strategy based on test data taken in the third and final year of the EcoCAR competition. The improved control strategy enabled the vehicle to achieve a utility-factor-corrected fuel consumption of 82 mpgge on combined city and highway driving, as well as Tier 2 Bin 2 tailpipe emissions as defined by the Environmental Protection Agency (EPA), when driven on the EcoCAR drive cycle, an on-road approximation of 55% city and 45% highway driving.