Intelligent cruise control with traffic preview introduces a potential to adjust the vehicle velocity and improve fuel consumption and emissions. This paper presents trade-offs observed during velocity trajectory optimizations when the objective function varies from fuel-based targets to emissions-based. The scenarios studied consider velocity optimization while following a hypothetical leader executing the federal test procedure (FTP) velocity profile with distance constraint, instead of the classical legislated velocity constraint, to enable the flexibility in optimizing the velocity trajectory. The vehicle model including longitudinal dynamics, fuel consumption and tailpipe NOx emissions is developed for a medium-duty truck with a diesel engine and verified over the FTP. Then, dynamic programming is applied on a reduced-order model to solve the constraint trajectory optimization problem and calculate an optimal vehicle velocity profile over the temperature stabilized phase (Bag 2) of the FTP. Results show 59% less tailpipe NOx emissions with an emission-optimized drive cycle but with 17% more fuel consumption compared to a non-optimized baseline. Whereas, a fuel-optimized cycle improves the fuel efficiency by 18% but with doubled tailpipe NOx emissions. Moreover, it is shown that for a diesel powertrain, including the aftertreatment system efficiency associated with the thermal dynamics is crucial to optimize the tailpipe NOx emissions and can not be ignored for problem simplification.
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Hardware-in-the-loop exploration of energy versus emissions trade-off in eco-following scenarios for connected automated vehicles
Studies on eco-driving have mostly taken an energy-centric view and considered driving performance, while less attention has been paid on emissions behavior. This work extends in an experimentally verified way our understanding of the trade-offs among fuel economy, driving aggressiveness, and, especially, emissions in connected automated diesel-powered vehicles. Experiments are performed with a 6.7-L Ford Powerstroke diesel engine, a urea-SCR based NOx aftertreatment system, and a full model for a Ford F250 medium-duty truck in the loop to provide realistic assessment of fuel consumption, tailpipe emissions, and driving style performances. An energy and emissions conscious speed planner is leveraged to follow the traffic. This planner offers flexibility in prioritizing energy or emissions while satisfying user-defined headway constraints, and thus allows exploration of different calibrations in a unified way. Results show how various calibrations of the flexible leader following policy yield 8%–14% decrease in total fuel consumption and 64%–70% decrease in tailpipe emissions compared with a strictly constrained following policy.
more » « less- NSF-PAR ID:
- 10368339
- Publisher / Repository:
- SAGE Publications
- Date Published:
- Journal Name:
- International Journal of Engine Research
- Volume:
- 24
- Issue:
- 4
- ISSN:
- 1468-0874
- Page Range / eLocation ID:
- p. 1643-1654
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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