Analysis of Drivability Influence on Tailpipe Emissions in Early Stages of a Vehicle Development Program by Means of Engine-in-the-Loop Test Benches 2020-01-0373

Due to increasing environmental awareness, standards for pollutant and CO₂ emissions are getting stricter in most markets around the world. In important markets such as Europe, also the emissions during real road driving, so called “Real Driving Emissions” (RDE), are now part of the type approval process for passenger cars. In addition to the proceeding hybridization and electrification of vehicles, the complexity and degrees of freedom of conventional powertrains with internal combustion engines (ICE) are also continuing to increase in order to comply with stricter exhaust emission standards. Besides the different requirements placed on vehicle emissions, the drivability capabilities of passenger vehicles desired by customers, are essentially important and vary between markets. As the interactions between different hardware and software parts of the powertrain strongly influence the drivability characteristics of a vehicle, a high degree of maturity of test vehicles is required to execute drivability calibration tasks with a reliable evidence. Hence, these calibration and evaluation tasks are generally conducted in late phases of the vehicle development process where the engines base calibration is already at an advanced level. Thereby, the assessment of the influences of drivability calibration on the vehicle’s tailpipe emissions is complex. Since any changes to the powertrain and exhaust gas aftertreatment systems, except calibration changes, are very expensive and time consuming in late vehicle development phases, drivability related emission analyses and enhancements are usually not carried out or considered separately.

Before this backdrop, this article introduces a method to determine and enhance the influence of drivability calibration demands on tailpipe emissions already during early vehicle development phases. The utilization of objectification of the vehicle’s drivability behavior enables frontloading of drivability calibration tasks into phases of investigations on engine test benches. Therefore in this work, a highly dynamic “Engine-in-the-Loop” (EiL) test bench, which is equipped with emission analyzers and operated as part of a virtual co-simulation scenario, is used to compare the individual tailpipe emissions of two regionally different drivability calibration data sets for the same powertrain/vehicle variant. With this technique, the customer and market-specific requirements for longitudinal drivability and their interdependencies on the vehicle’s tailpipe emissions can be considered in early vehicle development phases, in which pilot or final production equivalent vehicles are not yet available. Thus, the risk of expensive late changes during a vehicle development program can be significantly reduced, as base calibration tasks of the combustion engine can already be carried out against the background of the later desired drivability behavior.