Multi-scale analysis for engine momentary crankshaft speed

Misfire detection or cylinder by cylinder variations feedback using momentary crankshaft speed is practical for certain engine conditions such as idle speed. It is still a difficult problem at high speed and transient condition. Aiming at that remaining challenge, this paper presents a new tool wavelet transform to process the momentary crankshaft speed. The multi-scale (or multiresolution) analysis of the speed signal at different engine operating condition is presented. The speed fluctuations between normal combustion and misfire are compared. The results indicate that wavelet transform is a suitable tool to process the speed signal and it paves a new way to achieve misfire detection at high or transient speed condition