<div>Exhaust emission standards for road vehicles require on-board diagnostics (OBD)
of all comprehensive powertrain components (CCMs) impacting pollutant emissions.
The legislation defines the generic malfunction criteria and pollutant threshold
limits to trigger the component functional degradation. The electric drivetrain
in xEV (more than one propulsion energy converter) applications substitutes or
supports the internal combustion engine (ICE) operation with electric machine
(EM) power. Malfunctions in the electric drivetrain will lead to an increase in
ICE power demand. Hence, the electric drive system is classified as a
comprehensive component in the OBD legislation. The regulation defines
monitoring of the EM performance. The malfunctions that could prevent the EM(s)
from properly operating emission control strategies, including any ICE control
activation or electric drivetrain performance degradation, should be monitored
by the OBD system. This work demonstrates an approach to systematically
transform generic OBD legislation requirements into granular component
malfunctions based on a simulation approach in the early development phase for
an electric drivetrain. In the first step, the generic legislation requirements
of properly functioning emission control strategies and performance degradation
are transformed into electric drivetrain system element functional attributes.
The malfunctions from different sources were collected as a potential
malfunctions list including malfunction characterization. The impact on electric
drivetrain system element functional attributes is determined for each of the
malfunctions based on their characterization. Then, the matching set of
malfunctions between the potential list and the OBD-derived system element
functional impacts resulted in an optimized malfunction list. These optimized
malfunctions are evaluated for their exhaust emission impact on a map-based
one-dimensional vehicle longitudinal simulation model. The faults are also
modeled to simulate their impact on ICE operation and their exhaust emissions
when driven in the Worldwide harmonized Light-duty vehicles Test Cycle (WLTC).
There are electric drivetrain faults that significantly increase the exhaust
emissions of carbon monoxide (CO), non-methane hydrocarbons (NMHC), and oxides
of nitrogen (NO<sub>x</sub>). Hence, it is important to note that even if the
ICE is faultless, increased pollutant emissions can occur due to electric
drivetrain malfunctions in an xEV vehicle.</div>
