| Summary: | With a strong legal basis and regulatory authority, cost-effective transient emission sensors that reflect real-driving emissions are key factors for accomplishing environmental requirements. It is difficult for the existing NO<sub>x</sub> emission monitoring techniques to achieve a balance between accuracy and timeliness. Fundamentally, in-cylinder combustion is the thermodynamic cause of NO<sub>x</sub> emissions and the main excitation source for engine vibration and noise emissions. A novel vibration-based virtual NO<sub>x</sub> sensor is developed based on these critical relationships for real-time NO<sub>x</sub> monitoring. First, the correlation between vibration and NO<sub>x</sub> emission was characterized in-depth. Then, a technique of constructing two-dimensional filters for vibration signals is proposed to extract combustion-related information. A principal component regression (PCR) model for NO<sub>x</sub> prediction was established based on the reconstructed in-cylinder pressure. Finally, the virtual NO<sub>x</sub> sensor is tested and validated on a single-cylinder diesel engine bench. The virtual NO<sub>x</sub> sensor is proven to meet the accuracy requirement of vehicle emission monitoring for both steady-state and transient conditions and has a better frequency response compared to the emission measurement system.
|
|---|