Eco-Driving of Compression-Ignition Vehicles to Minimize Nitrogen Oxide Emissions

Emissions of nitrogen oxides from road vehicles pose a public health hazard because of their role in smog and acid rain formation. Although a great body of research exists on driving techniques to reduce vehicular fuel use and carbon dioxide emissions, solutions for other pollutants such as nitrogen oxides are not nearly as well studied. Unfortunately, nitrogen oxides do not necessarily trend with fuel consumption as carbon dioxide emissions do and the fuel-minimal solution may produce excess nitrogen oxides. This article addresses the emissions eco-driving problem for compression-ignition engines with EGR and SCR using an optimal control approach based on Pontryagin's minimum principle (PMP). In anticipation of eco-coaching applications, a simplified piecewise-affine model results in optimal acceleration as rational functions of speed. The effectiveness of this approach is compared to dynamic programming (DP) and heuristic rules from an available eco-driving mobile app. When applied to a real-world human driving dataset from an urban area, the proposed technique reduced modeled emissions of nitrogen oxides by 35%-36% while simultaneously reducing carbon dioxide emissions.