Janghyeok Won

Energy assessment of electrified vehicles requires driving cycles that include altitude change, whereas certification cycles and most synthesis methods describe flat-road speed profiles only. This study synthesizes time–speed–altitude driving cycles from real-world data (145.7 h, 10,491 km). Road grade was obtained from a vehicle-mounted barometric sensor corrected for its speed-dependent pressure drop, and its low-frequency drift was replaced by a digital elevation model (DEM). A distance-based semi-Markov route model of road types (urban/rural, highway and mountain) was combined with a 1 s Markov chain of type-specific acceleration and grade transitions; sign symmetrization and a grade-trend state removed the net-ascent bias. For 4934 synthesized cycles, the route model reduced the root mean square error (RMSE) of the steep-grade share by speed bin from 9.2 to 2.5 percentage points, and sampling the next acceleration instead of the next speed reduced the deviation of the mean positive vehicle-specific power (VSP) from +27% to +3.4%. With terminal decelerations sampled from measured stop approaches, the recoverable energy exceeded that of real-world windows ending with the same kind of stop approach by 3.3% (distance-weighted), and neglecting grade underestimated it by 18%. In day-level bootstrap and leave-one-day-out cross-validation, the traction power and energy deviations stayed within the day-to-day variability. A flat output reproduced the mean positive VSP, positive specific energy, and energy consumption of zero-grade real-world driving within 3%. Finally, a representative cycle and speed-group × VSP-severity cycles were selected.

All vehicles available for sale undergo certification tests mandated by law, and their certified fuel efficiency from these tests is indicated and disclosed. However, to address discrepancies between the certified fuel efficiency and actual driving conditions, more sophisticated certified modes, post-certification systems, and real-world driving tests have been introduced to complement the fuel efficiency certification system. The incorporation of a real-world driving mode, similar to certification modes, in vehicle research and development is of paramount importance from a directional perspective. To achieve this, various methods of configuring real-world driving modes have been proposed and applied in research. However, the validation of the correlation between fuel efficiency in real-world driving modes and certified driving modes is relatively limited. This study aimed to construct real-road driving cycles that are similar to the federal test procedure (FTP-75) and highway fuel economy test (HWFET) certification modes to determine the differences between the driving characteristics of the certification modes and real-road driving. The present study employed the commonly used relative positive acceleration analysis method along with a segmented short-trip technique for analysis. Additionally, variables such as fuel consumption and driving time were utilized to diversify our analytical methods. Test Routes A and B were configured for comparison with the fuel efficiency certification mode. An analysis of the relative positive acceleration (RPA) in both the test routes and certification mode confirmed that Test Route B, reflecting the actual driving patterns, closely follows the RPA distribution of the certification mode. Additionally, the fuel consumption for each short trip on each route was graphically represented, addressing aspects where determining the driving characteristics based solely on the RPA, such as the road grade, was difficult.