For a pure sine wave, the crest factor will be , and for normally distributed random noise, the value will be approximately 3. Compared to peak and RMS values, the crest factor is usually used when measurements are conducted at different rotational speeds because it is independent of speed. Crest factors are also reliable only in the presence of significant impulsiveness [1]. Jiang et al. [65] employed the crest factor features and SVM to diagnose gear faults. It was found that the crest factor is the most sensitive feature for gear failure and by applying this feature, the achieved diagnostic accuracy is 93.33%. Shrivastava and Wadhwani [58] applied the crest factor values along with other time domain features for the fault detection and diagnosis of rotating electrical machines. They found that the crest factor feature is unable to classify between healthy bearing, bearing with defective ball, and bearing with defective outer race. Aiswarya et al. [66] used the crest factor feature along with other time domain features to diagnose faults in the turbo pump of a liquid rocket engine. Combined with the SVM method in the fault classification stage, the proposed method can diagnose the fault effectively with 100% accuracy.
More than 100 articles were discussed in this study, covering a topic associated with the vibration analysis in machine monitoring and diagnosis in terms of instruments used in the data acquisition stage, feature extraction methods, and fault recognition by AI techniques. Because there is a large amount of literature on this field, a review of all the literature is impossible, and some papers might be omitted. For the data acquisition process and to answer the RQ 1, most of the studies applied the simpler and cheaper alternative of the computer-based analyzer, and with the help of DSP and FPGA, this analyzer is nearly as good as the conventional analyzer. Accelerometer is still the best sensor option for vibration analysis, and this has been proved by most of the articles reviewed. However, due to the high cost of the piezoelectric accelerometer, researchers are continuously working towards the application of the MEMS accelerometer, which can provide the same or better performance. Velocity transducer is preferable to be applied in diagnosing low-speed machinery compared to accelerometers as the absolute accelerations measured are much smaller in value for similar vibration displacements. Noncontact sensors also have a huge potential in machine monitoring as mounting the sensor on the machine is not a concern anymore which in turn, produces a more accurate measurement. However, due to its costly application, it is not widely used. LDV with multichannel measurements is expected to be widely applied in the future, where the cost of implementing the LDV is reduced.
Electrical Measurements And Measuring Instruments Rajput Pdf 33
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