A Precise Time–Frequency Positioning Method for Assisting Piston Pump Fault Diagnosis

This article presents a precise time-frequency (TF) positioning method that assists in the fault diagnosis of each piston in piston pumps. First, in response to the short-time broadband characteristics of the piston pump vibration pulse signal, the local maximum transient extraction transform (LTET) is proposed to provide a TF representation (TFR) with more concentrated energy. Second, the parameter setting of LTET is discussed, and the improved LTET (ILTET) method is proposed to achieve the precise positioning of the 2-D group delay (GD) of piston pump vibration pulses. Finally, by combining ILTET with the TF envelope and TF mask method, a periodic pulse screening method based on ILTET (ILTET-PPS) for piston pumps is proposed, which can effectively screen the piston vibration pulse, filter out random pulses (RPs), and noise interference. Experimental validation using vibration data from six piston pump operating conditions demonstrates that the Rényi entropy value of the TFR obtained by ILTET is the smallest, and the nonzero values at the center frequency slice can accurately indicate the piston pulse components while disregarding noise components. In contrast, the TFR center frequency slices of the STET, TET, TMSST, and short-time Fourier transform (STFT) methods exhibit a significant amount of noise components. This proves that ILTET exhibits superior energy concentration and noise robustness compared to other methods. The PPS method can more accurately extract high-quality piston pulses based on the TFR provided by ILTET, while the TFR from other methods can lead to the extraction of noise components in the PPS process. This demonstrates the effectiveness and superiority of ILTET-PPS.