Technical Challenges with on Board Monitoring

The proposed Euro 7 regulation includes On Board Monitoring, or OBM, to continuously monitor vehicles for emission exceedances. OBM relies on feedback from existing or additional sensors to identify high emitting vehicles, which poses many challenges. Currently, sensors are not commercially available for all emissions constituents, and the accuracy of available sensors is not capable enough for in use compliance determination. On board emissions models do not offer enough fidelity to determine in use compliance and require new complex model innovation development which will be extremely complicated to implement on board the vehicle. The stack up of multi-component deterioration leading to an emissions exceedance is infeasible to detect using available sensors and models. An assessment of limitations and measurement accuracy for sensors or models including oxides of nitrogen (NOx) sensors under a variety of operating conditions, ammonia (NH₃) sensing, and particulate matter (PM) sensing is provided. This paper also reviews what is being promulgated elsewhere in regard to using on-board sensors or portable emissions measurement systems (PEMS) to directly measure pollutants such as the California Air Resources Board (CARB) “Real Emissions Assessment Logging (REAL) NOx Tracking” system and in-use on-road emissions testing requirements. Considering the aforementioned technical challenges with OBM, we will offer practical measures to identify significant excess emissions and detect tampering of the emission system. We will consider the use of already available designs including statistical analysis of diagnostic results and other solutions that can be implemented quickly. One such solution is closing the gap to existing US/CARB On Board Diagnostic (OBD) requirements. We will also discuss the challenges of defining standardized data parameters to support the proposed implementation timing.