A new method for collecting vehicle behaviour in daily use for energy and environmental analysis

Abstract

Abstract

The power supply, fuel consumption, and noxious emissions of a vehicle depend on the use that is made of it. Usually [1] only the driving cycle is considered to be a sufficient way to gauge a vehicle's usage. It is not, however, enough. Experimental tests have proved that, while similar driving cycles entail similar power demand, fuel consumption and emissions differ. In addition, a driving cycle, usually a synthesis [1-7] of several cycles collected experimentally, represents neither a specific link of the road network nor a specific user. Vehicle use must, accordingly, be described by something more comprehensive than the driving cycle, and this might be called the ‘use cycle’, for which a definition needed to be found. For a definition of the use cycle, all possible factors influencing vehicle emissions had to be examined. It was thus necessary to develop a tool both for gathering data that might reveal a different use of the vehicle and for identifying factors that might have an influence on emissions. The easiest, cheapest, and most versatile way to collect real data on the use of a vehicle is to use the vehicle's own sensors connected to the on-board diagnostic (OBD-2) port. Readings from a GPS can provide some characteristics related to the vehicle's position. This paper describes the development of a tool for collecting real-time OBD and GPS information. The acquisition tool was validated by a number of tests on a dynamometer chassis and differences are never higher than 3 per cent (e.g. on speed max 2 km/h). The first result obtained on vehicle usage is that driver behaviour influences throttle position independently of the driving cycle. Even with similar driving cycles, the accelerator pedal position and its variations turned out to be heavily different, suggesting a new definition of driver behaviour linked to the way the driver uses the pedals. Such pedal movement does have an influence on the air-fuel ratio, which remains stable around the stoichiometric value with ‘calm’ use of the accelerator, while it changes continuously, never becoming stoichiometric, with ‘aggressive’ accelerator behaviour. The continuous use of the developed tool on large fleets of vehicles will allow progress along this path and help define use cycles that may then be used by car manufacturers to design vehicles more efficient in their different uses and by the authorities to force more stringent homologation rules.