Instantaneous rotational speed measurement of the engine is crucial in routine inspection and maintenance of an automobile engine. Since the contact measurement of rotational speed is not always available, the vibration measurement has been used for noncontact rotational speed estimation methods. Unfortunately, the accuracy of the noncontact estimation methods by analyzing engine vibration frequency is not satisfactory due to the influence of noise and the strong nonstationary characteristic of the vibration signal. To overcome these problems, based on the multiple matching synchrosqueezing transform (MSST) (MMSST, improved MSST with multiple squeeze operations), a novel noncontact method is proposed to accurately estimate the instantaneous rotational speed of automobile engine in this paper. Firstly, a MMSST is proposed to process the vibration signal to obtain a concentrated time-frequency (TF) representation. Secondly, the instantaneous frequency (IF) detection algorithm is employed to extract the fundamental frequency from the TF result. Finally, the rotational speed of the engine is calculated according to the relationship between the fundamental frequency and rotational speed. Results from numerical simulations and test on real engine have proven that the proposed method can obtain much higher frequency resolution and more precise IF estimation of the engine vibration signal and more accurate rotational speed estimation result compared with the MSST method. Furthermore, the proposed method is verified to have a stronger noise robustness and can provide satisfactory estimation results for engine vibration signal containing nonlinear frequency-modulated components.

中文翻译：

---

基于多重匹配同步压缩变换的瞬时发动机转速估计方法

发动机的瞬时转速测量对于汽车发动机的常规检查和维护至关重要。由于旋转速度的接触测量并非总是可用的，因此振动测量已用于非接触旋转速度估计方法。不幸的是，由于噪声的影响和振动信号的强烈的非平稳特性，通过分析发动机振动频率的非接触估计方法的准确性不能令人满意。为了克服这些问题，本文基于多重匹配同步压缩变换（MSST）（MMSST，经过多次挤压的改进型MSST），提出了一种新颖的非接触方法来准确估计汽车发动机的瞬时转速。首先，提出了一种MMSST来处理振动信号以获得集中的时频（TF）表示。其次，采用瞬时频率（IF）检测算法从TF结果中提取基本频率。最后，根据基本频率和转速之间的关系来计算发动机的转速。数值模拟和实际发动机测试的结果证明，与MSST方法相比，该方法可以获得更高的频率分辨率，更精确的发动机振动信号IF估计和更准确的转速估计结果。此外，