Construction de cycles de conduite représentatifs pour la mesure des émissions de polluants des véhicules
The measurement of pollutant emissions from vehicles requires the defining of representative test conditions and driving cycles. This last one requires a knowledge of vehicle usage and of their operating conditions. For that, private vehicles are fitted with on- board data acquisition systems, and used normally by their owner. According to these principles, 80 European cars have been selected and monitored by 4 European laboratories. Globally, 10,000 trips and 90,000 km have been recorded. Driving conditions are analysed through the speed recorded on-board the vehicles, during elementary periods, or kinematic segments with homogeneous size. These ones are described by the crossed-distribution of the instant speeds and accelerations. Correspondence Analysis and Clustering allow the defining of a driving conditions typology in 12 classes. The same tools are used to characterise trips as regards the driving conditions encountered. According to these typologies, two sets of 3 and 8 driving cycles are built-up that represent urban, road and motorway trips. 30 gasoline and diesel vehicles, with and without catalysator are tested on a chassis dynamometer using these driving cycles. Emissions values (CO, HC, NOx and CO2 ) measured on the 3 main driving cycles underestimate the results obtained while using the 8 cycles. That highlights the necessity of a detailed description of the driving conditions, as non-average operating conditions can led to high overemissions. Link between thermal and kinematic conditions and the impact of cold start show the necessity to proof this point. Links between driving conditions and vehicles characteristics question the principle of the usage of a unique driving cycle for all the vehicles.