Automated Inspection System for On-line Detection ofCracked Eggs

摘要

Egg grading is determined by internal and external quality. As an assessment method of the egg quality, a candling method is commonly used to identify eggs with cracked shells and internal defects. But this method is time-consuming and laborious. In addition, practically, it is challenging to detect hairline and micro cracks. In this study, an on-line inspection system based on acoustic resonance frequency analysis was developed to detect hairline cracks on eggshells. A roller conveyor was used to transfer eggs along one lane to the impact position where each of eggs rotated by the roller was excited with an impact device on four different locations on the eggshell equator. The impact device consisted of a plastic hammer and a rotary solenoid. The acoustic response of the egg to the impact was measured with a small condenser microphone at the same position as the impact device was installed. Two acoustic parameters, correlation coefficient for normalized power spectra and standard deviation of peakresonant frequencies, were used to detect cracked eggs. Intact eggs showed relatively high coefficients of correlation for the four normalized power spectra and low standard deviations of the four peak resonant frequencies. On the other hand, cracked eggs showed acoustic characteristics opposite to those measured with the intact eggs. This method allowed a crack detection rate of 97.6%.