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Improvement in OBD Development Process for HEV's

Hybrid technology has the potential to enable dramatic reductions in greenhouse gases (GHG), such as the California goal of reducing GHG by 80 percent from 1990 levels by 2050. As a result it is expected that hybrid systems will occupy a growing proportion of the market. However, introducing a hybrid system in a vehicle may adversely affect the performance of the engine OBD system in monitoring malfunctions impacting pollutant emissions. For example, a hybrid system that reduces time of the engine in idle or deceleration overrun conditions could make a well-performing engine OBD system noncompliant, by reducing in-use frequency of some OBD monitors below acceptable levels. In this presentation, Ricardo will present a process for evaluating the impact that a hybrid system which has been optimised to minimise GHG emission over a specified drive-cycle will have on the effectiveness of engine OBD monitors. The process involves the use of a Vehicle Simulation Model (VSIM) to predict vehicle performance, fuel consumption and emissions over specified drivecycles. The process extracts OBD engine system monitor enable conditions from the Summary Table and verifies that each monitor meets or exceeds minimum IUMPR requirements. Global optimisation techniques including Dynamic Programming are used to perform off-line optimisation of a hybrid vehicle system traversing a specified drive cycle. The optimisation process generates torque split, mode and gear changes required to minimise GHG emissions. This optimal engine-transmission-machine on-time profile is automatically analysed to generate the impact on the engine OBD system.

Andrew David Noble, Ricardo Consulting Engineers, Ltd.
Minsuk Shin, Ricard Inc.

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