Abstract
Research and/or Engineering Questions/Objective:
A major challenge in the Euro 6 light duty and Euro VI heavy duty vehicle OBD requirements is the detection of partial DPF failures against the upcoming particulate OBD threshold limits. This paper summarizes information from a project funded by the European Commission, DG-Enterprise. Objective of this study was the assessment of the technical feasibility of the proposed particulate OBD thresholds and the evaluation of the soot sensors available in the market at mature development state.
Methodology:
A review of the European and Worldwide legislation and of the available monitoring hardware options has been made in order to identify the challenges imposed by the more stringent OBD requirements. For the evaluation of the different monitoring hardware a test procedure was developed which includes testing protocols and cycles, measurement equipment as well as handling of the soot sensors. A significant element of the test procedure is the methodology to artificially introduce failures to diesel particulate filters in order to simulate different levels of particulate emissions. The failure methodology is able to produce DPFs with specific filtration efficiency and consequently DPF out soot emission level and at the same time determine the correlation of the test cycle soot emissions with gravimetric PM emissions. Finally, in order to evaluate the sensor performance, a generic OBD algorithm was developed and calibrated for each of the evaluated sensors.
Results:
Sensors were tested on engine and chassis dynamometers. Information is given on the different principles of operation chosen by developers. The resulting OBD models simulated the behaviour of the sensors on a vehicle and provided a malfunction illumination decision using as input the sensor signals and information of the vehicle OBD data stream. The error of omission and error of commission were determined for each sensor, test engine and vehicle and used as sensor evaluation score. The results of the extensive multi laboratory, multi sensor study are presented and discussed.
Limitations of this study:
The main limitation of the study was the fact that all assessed monitoring technologies were at early stage of development lacking durability and/or suitable implementation algorithms.
What does the paper offer that is new in the field including in comparison to other work by the authors:
This paper presents an independent assessment of the monitoring technologies and the thresholds these technologies are expected to cope with. It is using an innovative approach that combines testing with dedicated OBD detection algorithms developed specifically for this project.
Conclusions:
Different sensors were evaluated in a relative and absolute ranking. Their ability to identify PM related failures at the OBD threshold limit levels set by the legislation or at less or more stringent levels was determined. From the evaluation of a sample of 5 sensors it was concluded that at the time of writing this text there were available sensors able to fulfil the EU OBD threshold limit requirements. Certain concerns on sensor durability are expected to be addressed at later sensor development stages. The latter may introduce the need of additional lead time for the sensor developers and vehicle OEMs.
KEYWORDS – On-Board Diagnostics, PM threshold, DPF, soot sensor