Research On Detection Of Eggshell Crack Based On Dynamic Signal Analysis

Cracked eggs are prone to spoilage caused by pathogenic microorganisms.Accurate detection and timely processing of cracked eggs are conducive to reducing economic losses and ensuring food quality and safety.At present,the research results of eggshell crack detection are abundant in our country,but there are still some problems compared with foreign detection devices,especially in the eggshell crack detection method based on the analysis of eggshell vibration signals.Aiming at the problems of the lack of research on the excitation response signal generation mechanism and the poor stability of response signals,dynamic response characteristics of eggshell were studied.In order to improve the recognition rate of cracked eggs,the relationships between the response signal and the device structure was analyzed.This can provide technical support for the development of eggshell crack detection equipment.The main research results are summarized as follows:1.Mechanics analysis and structural optimization of the excitation device.The mechanical model of the excitation device was established and the excitation process was analyzed.The results showed that the excitation pulse can be approximated by a half sine wave.The spectrum of excitation pulse was analyzed.The results showed that the sensitivity of response signals for eggshell crack information can be improved by reducing the pulse width and increasing the pulse peak.Structural parameters of the excitation rod were optimized on the basis of the spectrum analysis results.The mass of the optimized excitation rod was less than 5.6g,and the nylon was selected as the material of impact head.The effect of the optimized device was verified by an experiment.The results showed that,the difference in the excitation pulse of intact and cracked eggs was obvious.The consistency and stability of the excitation pulse of intact eggs produced by the optimized excitation stick were better,and correlation coefficients between the pulse of intact eggs and mathematical model were above 0.92.2.Finite element analysis of vibration response signals and selection of measuring points for sensors.The dynamic geometric model of eggs was established,and the propagation characteristics of vibration response signals of the eggshell were studied by the finite element simulation technique.The influence of the crack on the vibration characteristics of the eggshell was analyzed.The results showed that vibration waves of intact eggs were continuous,and the eggshell structure of cracked eggs was destroyed.When the vibration wave propagated to the crack,the vibration of eggshell changed as a result of scattering and reflection phenomena.Considering relationships between the location of the crack and the position of sensors,the coherence function analysis method was used to select measuring points of the sensor,which were the blunt end,sharp end and equator of eggs.3.Experimental study on eggshell crack detection based on dynamic response characteristics.According to the result of the optimized excitation device and the vibration measuring points of sensors,a set of experimental devices based on the dynamic response characteristic was designed for eggshell crack detection.Based on the time domain and frequency domain analysis of the vibration response signal,the characteristics of intact eggs and cracked eggs response signals were studied.The linear discriminant analysis(LDA)model was established by using six characteristic parameters as input variables.The highest identification rates of the training set and prediction set were 99.38% and 97.5%,respectively.The research of some problems about the detection method of eggshell crack based on dynamic response characteristics was carried out.The results showed that it was practicable and effective to improve the recognition rate of eggshell crack by optimizing the parameters of the excitation device,the detection conditions and the reasonable measuring points of the sensor.The research conclusions were favorable for the development of crack detection device for eggs and other species.