Fruit Internal Defect Detection Using Laser Vibrometry
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Solution Overview
Problem
Current methods for detecting internal defects in fruits are time-consuming, labor-intensive, and lack accuracy, making them unsuitable for high-throughput rapid detection, relying heavily on manual observation and simple vibration data analysis.
Innovation Solution
A non-destructive detection system utilizing a pulse type gas spray device and a laser Doppler vibrometer, combined with wavelet transformation to analyze vibration signals, extracts time-domain and frequency-domain characteristic parameters to establish a prediction model for identifying internal defects in fruits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual observation and knocking sound methods are used for internal quality inspection of fruits, then the detection process is simple to implement, but the detection accuracy is low and time-consuming
Solution Approach 1:
The patent replaces manual observation and knocking methods with a laser Doppler vibration detection system. The laser Doppler vibrometer non-contactly measures fruit vibration responses, and wavelet transformation algorithms automatically analyze the signals to detect internal defects, eliminating manual labor while improving both accuracy and throughput.
Solution Approach 2:
The patent transforms the detection approach by changing from simple time-domain vibration signals to time-frequency domain analysis using wavelet transformation. This parameter transformation enables extraction of characteristic features that accurately indicate internal defects, significantly improving detection precision.
2Measurement precision
If fast Fourier transform is used to convert vibration signals from time-domain to frequency-domain for analysis, then the method is simple and easy to implement, but the online detection accuracy of internal defects is insufficient
Solution Approach 1:
The patent segments the vibration signal analysis into multiple stages: first applying fast Fourier transform to convert to frequency domain, then using wavelet transformation to further decompose the signal into time-frequency components. This multi-stage segmentation allows extraction of more discriminative features for accurate defect detection.
Solution Approach 2:
The patent transitions from one-dimensional frequency-domain analysis (FFT) to two-dimensional time-frequency domain analysis (wavelet transformation). This dimensional expansion provides additional information about when specific frequency components occur, improving defect detection accuracy while managing computational complexity through efficient algorithms.
3Productivity
If conventional vibration data analysis methods are used, then the system structure is simple, but the detection throughput and speed are insufficient for high-throughput rapid detection
Solution Approach 1:
The patent implements continuous non-contact laser scanning as fruits move on the conveyor belt. The laser Doppler vibrometer continuously tracks vibration responses in real-time, enabling high-throughput detection without interrupting fruit flow, thereby maintaining both speed and accuracy.
Solution Approach 2:
The patent replaces contact-based vibration excitation and measurement with non-contact laser Doppler vibrometry. This eliminates mechanical wear and allows rapid sequential measurement of multiple fruits, significantly increasing detection throughput while maintaining measurement precision through optical sensing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system significantly improves detection accuracy and efficiency by performing time-domain and frequency-domain analysis, enabling rapid and precise identification of internal defects, such as hollow fruits, with the potential for application across various fruit types.
Implementation Method 1
laser Doppler vibrometer technology has the advantages of high sensitivity, fast dynamic response, and large measurement range
Implementation Method 2
a laser Doppler vibrometer is adopted to collect the vibration response signal of the sample
Implementation Method 3
The designed pulse type gas spray device is adopted to excite the sample
Data Source
AI summary
Disclosed are a nondestructive detection system and a method for an internal defect of a fruit. The system comprises an aluminum profile frame, a conveyor belt, a tray, a pulse type gas spray device, and a laser Doppler vibrometer; when a piece of fruit passes a detection station, the pulse type gas spray device excites the fruit to vibrate, and the laser Doppler vibrometer evaluates a vibration response signal of the fruit; a time-domain vibration characteristic parameter and a frequency-domain vibration characteristic parameter are acquired by means of a wavelet transform and a fast Fourier transform; and a prediction model for an internal defect of the fruit is established on the basis of the acquired time-domain and frequency-domain vibration characteristic parameters.