基于双谱的汽油机爆震特征提取与强度评价
Gasoline Knock Feature Extraction and Knock Intensity Evaluation Using Bispectrum

将双谱分析应用于爆震振动信号分析，提出了爆震特征频率提取和强度判定的方法。首先，用功率谱密度估计的方法分析发动机3个方向的振动信号，确定爆震特征频率范围；然后，利用双谱分析不同爆震强度下的振动信号并提取双谱主对角线切片，分析不同状况下的信号频率间的相位耦合关系，确定爆震特征频率；最后，提出了爆震强度评价参数。试验结果表明，相比功率谱密度估计，双谱峰值频率更能凸显爆震特征频率，爆震强度评价参数能有效判定爆震强度。
Knock feature extraction detection is the key of closed loop control of ignition in gasoline engine, and it is also the difficult point in knock measurement. In this paper, an investigation of knock detection in gasoline direct injection(GDI) engines using bispectrum slice based on the engine cylinder head vibration signals. Power spectrum density(PSD) estimation is used to determine the band range of the resonance frequency generated by knock component. The diagonal slice of bispectrum is computed to extract the non-linear feature deriving from the quadratic phase coupling, as well as the knock characteristic frequencies. This method is endowed with characteristics of suppressing Gaussian white noise, detecting the nonlinear coupling feature, and which is used to extract the knock threshold characteristic information. Derived from the above method, a novel knock intensity factor has been developed and the relevance of the proposed criterion for characterizing different levels of knock has been investigated.