How do you evaluate your Real Driving Emissions (RDE) data?

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Calibration engineers are concerned with many aspects of the vehicle: driveability, performance, efficiency, and exhaust gas emissions.  The availability of targeted software tools increases an engineer’s efficiency and ability to deliver a higher quality product on schedule by affording more time to analyze and develop solutions to problems.

I would like to share some background on the Real [World] Driving Emission (RDE) testing requirement and some ideas on using ETAS INCA calibration software tools.  INCA with two add-ons, INCA-RDE and INCA-FLOW can improve RDE testing as well as other vehicle level development and testing.

What is a Real Driving Emission Test?

In order to market a vehicle, automobile manufacturers must prove that their vehicle is in conformance with laws established to protect the environment and our health.  However, various organizations have reported data exceeding minimum air quality standards or differences in reported to measured exhaust gas emissions.  Already prior to 2011, the EU commission recognized differences between real world and laboratory testing thereby established a working group to develop a Real Driving Emissions test protocol.   Therefore, the Real Driving Emission (RDE) testing requirement was implemented by the European Union Commission as of September 2017.

Real Driving Emissions, essentially “brings the lab to the vehicle” by installing a “mini-laboratory” which is referred to as a Portable Emissions Measuring System or PEMS.  The PEMS is typically mounted on the rear exterior of a vehicle and measures exhaust gas emissions and other data (see Figure 1).  Real Driving Emissions or RDE is conducted on public roads under varying conditions such as route type (urban, rural, highway).   This differs from typical established laboratory test cycles where the vehicle emissions are measured in under controlled, repeatable conditions.  INCA RDE guides the driver to ensure that all the requirements are met, thus ensuring a valid test.INCAFLOW_RDE_Configuration

Figure 1.  INCA RDE and PEMS Configuration

Are Real Driving Emissions Tests relevant to the United States?

The United States Environmental Protection Agency (US EPA) or California Air Resources Board (CARB) do not require similar RDE testing as the European Union, however, there are some current regulations and dialogue that are related to RDE.  In-Use Testing Program for Heavy-Duty Diesel Engines and Vehicles has been required by the US EPA since 2005.  Notably, the responses by CARB to the European Parliament Committee of Inquiry indicates a continued direction toward Real Driving Emissions.   “We plan to make extensive use of PEMS and other tools that can be used to assess real-world emissions” [CARB].

Where does INCA / INCA-RDE provide a benefit?

INCA-RDE provides the driver real time feedback to ensure that the multiple RDE test requirements are met (Figure 2).  This is preferred over post processing and later determining that several tests are invalid.  Additionally, INCA-RDE with a PEMS is a benefit because adjustments for driveability can be evaluated for emission impacts (neutral or increase/decrease) in real-time, rather than repeating a traditional development loop of modifying a calibration for driveability and then later re-testing for the emission impact with a different vehicle on a chassis dyno.  The RDE trip encompasses city, suburban, and highway driving for a duration of 90-120 minutes and a distance of approximately twenty-nine miles.  INCA-RDE could also be used without a PEMS as a guide for mileage accumulation to ensure that a vehicle was driven over various routes (vehicle speed range), at a level of dynamic operation and for a given duration.


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Figure 2.  INCA-RDE Benefits and Display

Additional benefits are achieved by combining INCA-RDE with INCA-FLOW Drive Cycle.  A chassis-dyno cycle, standard test sequence (0-60mph Wide Open Throttle), road event (traffic circle), or customer satisfaction issue could be replicated.  In this case, I created a test using a drive route recorded near Berlin.  The drive cycle was provided in an Excel format.  Using INCA-FLOW, the Excel file is read as an input for the Drive Cycle.  When the INCA-FLOW test process runs, the target vehicle speed with an error-band is displayed.  The user-created INCA-FLOW variable, ‘ADAS_Vehicle_Speed’, is regulated by the INCA-FLOW Proportional-Integral Governor to follow the recorded vehicle speed.  For a manual transmission, the Drive-Cycle also prompts the driver for the transmission gear selection (Figure 3).  Adding additional data such as steering angle, brake pressure, lateral and longitudinal acceleration would improve replicating a driving maneuver with INCA-FLOW.


Figure 3.  INCA-FLOW replication a Drive-Cycle Emission Display

If you want to learn more, please see the INCA-RDE article in our 2017/2108 RealTimes Magazine.  For any feedback or questions, just comment below.  I look forward to hearing from you!