Aspect of repeatability in Real Driving Emissions tests regarding to velocity profile

Abstract

Relatively large results discrepancies observed in vehicles emission tests became a reason for change of test procedure. The New European Driving Cycle (NEDC) test was replaced by more dynamic Worldwide Harmonized Light Vehicles Test Procedure (WLTP) on September 2017, however it occurred that emissions obtained in WLTP are still far from real ones. Due to that fact a new Real Driving Emissions (RDE) test was introduced in order to complement WLTP. RDE testing involves emissions measurement while vehicle being driven in real traffic conditions which is the biggest difference from previous tests conducted on chassis dynamometer. Because of that it is suspected that repeatability of RDE tests is significantly lower than in case of WLTP or even does not have to appear. Subject of authors investigation was evaluation of RDE tests repeatability. It included portable emission measuring system (PEMS) installation on vehicle and six test runs along test route designed in accordance with European Commission requirements. Results were then compared regarding to velocity profile of vehicle. Performed analysis involved statistical distribution of velocity profiles and their kurtosis and skewness comparison. It was found that tests repeatability occurs for some velocity ranges, however it is not satisfactory. Conclusions present the concept of further research on this problem.