Condition Monitoring in Diesel Engines for Cold Test Applications. Part II: Comparison of Vibration Analysis Techniques.

This work compares the effectiveness of different vibration analysis techniques for fault detection in diesel engines during cold tests for quality control at the end of assembly line. The cold test imposes a pass/fail decision comparing vibration features with proper threshold values. In part I, the authors have described the capabilities of the cold test monitoring and presented a technique based on statistical analysis of the vibration signal in the time domain in order to obtain reliable threshold values. In this part, the effectiveness of some advanced techniques is compared and discussed. Some parameters extracted by processing the PSD (Power Spectral Density) are compared to features obtained from time-frequency analysis techniques (Short Time Fourier Transform and Wavelet Transform) and from image correlations of the symmetrised dot pattern of the vibration signal (SDP). Experiments on 29 engines were carried out and eight different kinds of faults were introduced one by one in engines in order to assess the effectiveness of these techniques.