基于振动的汽油机爆震始点识别与强度评价研究

Research on Gasoline Knock Onset Identification and Knock Intensity Evaluation Using Vibration Signal

研究了利用振动信号进行汽油机爆震检测和强度评价的方法。通过滤波对机体振动信号进行降噪处理,利用功率谱密度估计确定了爆震特征频率。将集总经验模态分解(ensemble empirical mode decomposition,EEMD)应用到机体振动信号处理中,结合连续小波变换(continues wavelet transform,CWT)对EEMD分解得到的各本征模态函数(intrinsic mode function,IMF)分量进行时频分析,确定包含爆震特征频率成分的IMF分量,研究了利用振动信号判别爆震始点的方法,并结合缸压信号对结果进行了验证。在确定了准确的爆震窗口后,提出了爆震强度评价参数K。试验用汽油机的计算结果表明:当K值超过20,可以判断有轻微爆震的发生;当K值超过80,则代表爆震强度较强,发生明显爆震。

The research was focused on the gasoline engine knock detection and intensity evaluation using vibration signal. A proper filter was designed to reduce the noise from engine vibration signal, the power density spectrum estimation was made to determine knock characteristic frequency. The ensemble empirical mode decomposition （EEMD） was used to decompose the de-noised signal, the time-frequency characteristics of the intrinsic mode functions （IMFs） were analyzed using continues wavelet transform （CWT） and then the IMF containing the characteristic frequency band was further determined. Moreover, a knock starting point identification method was proposed, based on the IMF decomposed from the filtered signal and its accuracy was verified using the cylinder pressure signal which has high signal-noise ratio. The knock window was then determined, from which a new knock intensity evaluation factor K was proposed. The calculation result shows that when K is over 20, the engine can be estimated to have light knock and when K reaches 80, severe knock will be encountered.