第二代小波变换在汽油机爆震分析中的应用

为研究汽油机爆震的精确判定方法,研究了第二代小波变换在爆震分析中的应用.频率混淆是第一代离散小波变换的三大失真之一.分析了一种新型的第二代小波变换中的频率混淆问题,发现与第一代离散小波变换相比,这种新型的第二代小波变换在抑制频率混淆方面效果明显,而且运算时间明显减少.将这种新型的第二代小波变换应用于汽油发动机的爆震边缘检测,结果表明:该方法能够有效地提取缸压信号和更复杂的缸盖振动信号中的微弱爆震信息,运算速度更快,比第一代离散小波变换更适合于基于爆震的汽油机点火闭环控制.

Knock detection for gasoline engines based on the second generation wavelet transform

For precisely determining the detonation phenomenon of gasoline engines,the second generation wavelet transform was studied.Frequency aliasing is one of the three main distortions of the first generation discrete wavelet transform.A new type of the second generation wavelet transform was discussed to solve this problem.Compared with the first generation wavelet transform,the new type of the second generation wavelet transform is effective on suppressing frequency aliasing and saving computing time obviously.The new type of the second generation wavelet transform was then applied to the knock threshold detection of gasoline engine.The results show that the presented method can effectively extract the weak information of the knock from cylinder pressure signals and more complex signals of the cylinder head vibration.Compared with the first generation wavelet transform,the new type of the second generation wavelet transform is more suitable for the knock-based closed-loop ignition control for gasoline engines due to its faster computing speed.