Development and validation of a virtual soot sensor: Part 2: Transient engine operation

Abstract

The reduction of the legislative emission limits has led to an increased complexity of the engine control unit (ECU) calibration. Integrating feedback of the Particulate Matter (PM) and NOx emissions into the engine management could make fulfilment of legislation easier and reduce the complexity of the necessary calibration process. Due to the fact that production type PM sensors for raw emission feedback will not be available, or will be exceedingly expensive in the near future, in part 1 of this work, a virtual soot sensor (VSS) has been developed. Along with the very good steady state behaviour, the VSS is able to predict PM emissions in transient engine operation with a sufficient precision. This has been approved with different changes in torque demand at constant engine speed. Though an overestimation of the soot occurs during the first cycles of the step in torque demand, the behaviour of the engine out soot was well captured and compared with measurements from a photo-acoustic soot sensor (PASS) and characteristic end values of the representative in-cylinder soot trace (measured by multi-colour pyrometry). The performance of the control structure with integrated VSS is demonstrated on the new European driving cycle and an Urban Dynamometer Driving Schedule. Furthermore, a change in set point value demonstrates the opportunity of changing the raw emission strategy on-line. These results offer the opportunity to expand this cylinder-pressure-based VSS approach to other pollutants (primarily NOx) as well.