Research On On-line Detection System Of Eggshell Crack Based On Acoustic Technology

Eggs are an important component of Chinese diets,due to its rich nutritional value and easy to be absorbed by the human body.Absolutely China is a big producer of eggs with an annual output of eggs more than 30 million tons in the recent ten years.Nevertheless,eggs are inevitably be subjected to physical collision in the process of purchasing,loading,unloading and transportation,which cause structural damage to eggshells.If broken and cracked eggs are not detected in time,it will affect the sales of fresh eggs and the processing of egg products,resulting in economic losses and food safety risks.According to the analysis of the status quo of egg quality testing and eggshell crack nondestructive testing in China,the most urgent problem that domestic enterprises need to solve is the online detection of egg crack.Consequently,this paper uses acoustic technology to study the on-line detection system of eggshell crack.The main contents are as follows:1.In order to achieve the orderly knock of egg shell and signal acquisition,we design the eggs online percussion and signal acquisition unit,mainly including eggs transmission module,eggshell rap module,which can realize automatic transmission and automatic tapping eggs.Subsequently,the electrical control circuit of the system are built.Through mechanical and electrical coordination,eggs can be rolled forward and the self-adaptation of 16-way percussion station and transmission line speed can be met;2.The audio signal acquisition scheme is designed.The computer can complete the multi-channel synchronous acquisition of 8 microphones through 8 USB sound cards.Furthermore,the upper computer can open the sound card by reading the sound card number saved by the PLC register,and read the egg percussion sound signal collected by the corresponding microphones can realize the orderly collection of the knocking signal;3.In order to correct the machining error and obtain the knocking time sequence in the actual testing process,high-speed photography technology is used to collect the knocking process of eggs in operation,and the timing signal of the knocking device is corrected to analyze the collection law of audio signal and the movement law of the knocking stick in the continuous knocking process.Combined with the signal acquisition of the encoder,the precise pulse value of the equatorial position of the egg can be realized;4.According to the method of detecting eggshell crack by using correlation coefficient of multi-point knocking signal on eggshell surface,and the online detection and discrimination model of eggshell crack based on the correlation coefficient is established.The upper computer software is written based on Lab VIEW software,including the communication module between Lab VIEW and PLC,the acquisition module of eggshell knocking signal and the detection module of eggshell crack.The eggshell percussion signal can be displayed in real time on the PC interface,and the detection result can be directly displayed on the PC interface;5.The online detection system for eggshell cracks are tested.100 intact eggs and100 cracked eggs are real-time monitored at a detection speed of 3.5s/egg.The detection accuracy rates for intact eggs and intact duck eggs are 88% and 90%respectively,and for cracked eggs and cracked duck eggs were 96% and 98%respectively.