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Generation of an Driving Cycle in General

Wissenschaftlicher Aufsatz 2013 3 Seiten

Ingenieurwissenschaften - Fahrzeugtechnik


Generation of an Driving Cycle in General

Gerald Bonengel

J-Sport Automotive GmbH Cologne / Germany

Abstract— The energy consumption of vehicles is heavily depending on the operating environment in which they are used. To be able to create a realistic comparability of different products, legislation defined general conditions for the determination of specific values, such as consumption or emission-restriction. Part of these terms is the conventional driving cycle, a time-speed-profil, which helps to compare every vehicles within comparable terms. The choosen driving cycle has a strong impact on the development of vehicles, as the manufacturer optimize their drive concept in the shown operating range. Therefor it is very crucial that the driving cycle complies with the future field of application of of the vehicle. Only by this the consumption and the emission during operation can be minimized.

I. Introduction

A driving cycle describes a fixed given speed-time-course, which reproduced with a vehicle on a chassis dynamometer test bench. The defined speed-time-course is intended to show for each of the specific region typical operating characteristics of a vehicle on public streets. These driving cycles will be used for the identification of the legally limited exhaust emissions, as well as the fuel consumption/energy consumption. The purpose of a driving cycle is the definition of a basis for comparableness of exhaust emissions and fuel consumption of different vehicles with reproducible test conditions. The most important driving cycles in the car industry are the new “European driving cycle” (NEFZ), the FTP 75 in the USA and the “10-15 Mode” in Japan. The European and Japans cycles are synthetically constructed whereas the North American FTP 75 is showing a real test drive.

Figure 1: Velocity plot of the NEFZ Abbildung in dieser Leseprobe nicht enthalten

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Figure 1 NEFZ = NEDC [ECE]

The cycle is frequently as not customer representative regarded, which is shown in not reachable norm-consumptions in practice for actual cars. [1] Furthermore the actual emission limitations can such as for example Euro 6 can only be met within the cycle. In particular accelerations of the cycle are underestimated. For instance the acceleration from 0 to 50 km/h in nearly 30 seconds is not practice-oriented. This becomes visible by reviewing the needed engine loads within the NEFZ. FIGURE 2 is showing for example the engine load of a Toyota Landcruiser. It is visible that maximal 45% of the engine load and 2.500min-1 are required.

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Figure 2 Loadpoints Toyota LandCruiser NEFZ

Overall this stimulates the wrong impulsions for the engine developments, many drives/engines are developed towards a good norm-consumption and exhaust-emissions within the driving cycle, in place of fulfilling customer needs. In the process of engine improvements and development of new drives the comparability is implicitly required. In the meantime various concepts for realistic driving cycles do exist. For instance the Common Artemis Driving Cycle (CADC) has been developed in the framework of a EU project. [2]

II. Materials and Methods

Generally driving cycles can be defined by two methods. Firstly via a real drive with collection of drive-condition-data, e.g. speed and time, which build the basis for a driving cycle. Or secondly the driving cycle can be defined by statistical data, e.g. generation of frequency distribution of driving speed and vehicle acceleration. As the second alternative represents the average operation of a vehicle better, it is chosen as the accretion.

To define a general driver profile, the drive-condition-data for generating the driving cycle of an statistical investigation will be taken. [3] Via extensive test drives, frequency distribution of engine rpm and engine torsional, as well as parameter such as drive duration, stop times, brake times, speeds, acceleration and drive distance are identified.

The description of the representative driving cycle is determined by the arithmetical average of the specific value. The arithmetical averages are not showing the time development, but can be used as comparable quantity, as they are representing the average of a measurement for the full drive duration. Drive data records with nearly identical or rather identical with small variations of the specific values (arithmetical averages) towards the collective are taken as representative.

Alternatively a driver profile can be put together by single elements of the collective, which are showing similarly small variations. This drive cycle considers therefor driving patterns, originated from data file of the collective. Moreover the position of the engine operating points of the driving cycle in comparison to the collective can be taken as an assessment basis.

Driving data records with bigger deviations to the collective cannot be taken as representative. If necessary these driving data records can be used for an extreme inappropriate or “worst case” cycle.



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Titel: Generation of an Driving Cycle in General