A Methodology of Real-World Fuel Consumption Estimation: Part 1. Drive Cycles 2018-01-0644
To assess the fuel consumption of vehicles, three sets of input data are required; drive cycles, vehicle parameters, and environmental conditions. As the first part of a series of studies on real-world fuel consumption, this study focuses on the drive cycles.
In principle, drive cycles should represent real-world usage. Some of them aim at a specific usage such as a city driving condition or an aggressive driving style. However, the definition of city or aggressive driving is very subjective and difficult to quantitatively correlate with the real-world usage.
This study proposes a methodology to quantify the speed and dynamics of drive cycles, or vehicle speed traces in general, against the real-world usage. After reviewing parameter sets found in other studies, relative cubic speed (RCS) and positive kinetic energy (PKE) are selected to represent the speed and dynamics through energy flow balance at the wheels. The authors suggest a normalised 2-dimensional coordinate space representing speed and dynamics of the drive cycles by statistical analysis of the parameters. The suggested space can be used for quantitative mapping of homologation drive cycles onto the given real-world usage data and identify which group of customers the homologation drive cycles represent. Another potential application of the methodology is to compare the multiple coordinate spaces generated from different data sets such as different vehicle segments.
To demonstrate the proposed methodology, the 2-dimensional space is generated from a collection of data logged from passenger cars. The parameters of the collection show lognormal - normal distribution and are correlated to each other. Some homologation drive cycles are mapped onto the space and are compared to the real-world data followed by a discussion of the metrics of individual drive cycles.