Instantaneous frequency estimation method based on Prewitt operator and t test

Abstract

The present invention discloses an instantaneous frequency estimation method based on the Prewitt operator and the t test. The method employs the short-time Fourier transform to convert original signals to a time-frequency spectrogram, employs the Prewitt detection algorithm to obtain multi-strip ridge bands, employs the t test to eliminate the abnormal value of each ridge band, employs overlapping to construct a compound ridge band having a complete and clear edge, employs the t test to eliminate the abnormal value of the compound ridge band, calculates the mean curve of the compound ridge band, perform smooth processing of the mean curve, calculate a confidence interval, above the 95% confidence level, of the smooth mean curve and map the smooth mean curve and the confidence interval thereof to a target ridge to obtain the reference line and a local search interval of the target ridge, and employs a non-delayed cost function to extract the target ridge. The instantaneous frequency estimation method based on the Prewitt operator and the t test is suitable for estimation of instantaneous frequency of multi-component frequency conversion signals so as to overcome defects in the instantaneous frequency estimation of mechanical vibration signals of a traditional method, improve the accuracy and the precision of the estimation result and facilitate engineering application.

Description

technical field [0001] The invention relates to the field of state monitoring and fault diagnosis of rotating machinery, in particular to an instantaneous frequency estimation method based on Prewitt operator and t test. Background technique [0002] Due to the complexity of the working environment, rotating machinery often works under variable speed conditions. Instantaneous frequency estimation is an important prerequisite for evaluating the operating state and fault diagnosis of rotating machinery. The most commonly used instantaneous frequency estimation method is the one-step cost function method. The one-step cost function method can search for ridge points in the local frequency range, but the center point of the local frequency range depends on the position of the previous ridge point, which leads to a delay in the one-step cost function. In addition, the width of the local frequency range is set arbitrarily according to experience, and the width at any moment is f...

AI Technical Summary

Problems solved by technology

The one-step cost function method can search for ridge points in the local frequency range, but the center point of the local frequency range depends on the position of the previous ridge point, which leads to a delay in the one-step cost function

In addition, the width of the local frequency range is set arbitrarily based on experience, and the width at any moment is fixed and cannot change with time, which leads to a lack of sufficient adaptability of the one-step cost function

The above defects lead to the low accuracy and precision of the one-step cost function method in estimating the instantaneous frequency

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