Robust injection rate estimation in common rail diesel injectors with nozzle wear

The combustion performance in common rail diesel injectors is significantly influenced by the injection rate. Aging effects such as coking or cavitation, which develop in the injector nozzles over the lifetime, deteriorate the injection behavior and result in increasing soot and nitrogen oxide (NOx) emissions. The objective of this study is to present a robust injection rate estimator considering wear and aging effects within the injector nozzle. The two-stage estimation process consists of a wear estimator to identify wear effects within the injector nozzle and a sliding mode observer to improve the estimation accuracy and to cope with uncertainties.