Non-Destrctive Quality Evaluation Of Watermelon Based On Its Acoustic Property

The method for non-destructive quality evaluation of watermelon based on its acoustic properties was studied, and the main research contents and results were as follows:1. A fruit quality inspecting system based on its acoustic properties was developed, which consisted of a acoustic wave generator, sensors, a set of signal processing circuit, a data acquisition board, a computer and data sampling & processing software. The acoustic waves were produced by striking on the surface of watermelon with a steel ball wrapped in rubber, sensed by 2 microphones: The electric signal was amplified and filtered by a processing circuit first, the pass band of which is 3-3000Hz, and sampled at a rate of 10kHz with a data acquisition board PCL-1800 (Advantech Co., Ltd.), then processed by the MATLAB programmers.2. A special clamp for measuring the acoustic wave transmitting velocity was developed, which consisted of 2 microphones at a distance of 6cm, isolation covers, flexible covers and a bracket.3. By use of MATLAB programmers and LMS algorithm, an adaptive filter was designed to filter noises from the signal sampled during tests, which greatly improved the accuracy of the test results.4. The effects of measuring position, striking position, interior defects and growth status of watermelon on the accuracy of model, which reflected the relationship between the sugar content of watermelon and its acoustic wave transmitting velocity, were approached by experiment. It was found that when'the measuring position is at the middle of watermelon, and the striking position is at the peduncle of watermelon, the correlation coefficient of the model was the highest. In addition, the correlation coefficient of model was not sensitive to the interior defects of watermelon, but it was highly correlated to the growth status of watermelon. To improve the accuracy of the model, the different model should be set up for the watermelons, whose pedicel was attached to the ground, and other watermelons..5. By means of testing results, the model, which reflected the relationship between the sugar content of watermelon and its acoustic wave transmitting velocity, was established. It was:V = -5.5175sc3. +133.15.;-1 064sc + 2833 A , and the correlation coefficient of the modelwas 0.81208,6. To nondestructively measure sugar content of watermelon and evaluating its maturity by testing the acoustic waves transmitting velocity was effective, and it was not sensitive to the size and weight of watermelon. These results laid a solid foundation for the development of nondestructive measuring equipment of sugar content and maturity of watermelon.