JPH02240561A - Device for judging existence of hollow in watermelon - Google Patents

Abstract

PURPOSE:To automatically decide whether a hollow exists in a watermelon or not by deriving an acoustic pressure level difference of a first resonance point and a second resonance point in a power spectrum of an impulse response waveform. CONSTITUTION:With respect to a vertical line of a watermelon 1 placed on an installing base 20, a shock is applied by a ball 2 of an impulse shock generating device 6 along on a straight line which passes through its center part and intersects in the straight direction. Subsequently, a response waveform of its impulse shock is detected by an acoustic sensor 7 sucked to the opposed reverse side of the rubber ball 2, amplified 8 and brought to A/D conversion 9 and data of a prescribed time portion is inputted to a RAM 12, and a power spectrum is derived by an FFT method by a CPU 11. Next, the CPU 14 reads the power spectrum data of the RAM 12 through an interface 15, derives an acoustic pressure level of a first and a second resonance points, and when the acoustic pressure level of a first resonance point is higher than the acoustic pressure level of a second resonance point, it is decided as a normal fluid and displayed 19, and on the contrary, when the acoustic pressure level of a first resonance point is lower, it is decided as a hollow fruit and displayed 19.

Description

DETAILED DESCRIPTION OF THE INVENTION +8>Field of Industrial Application The present invention relates to a watermelon cavity determination device that non-destructively determines the occurrence of cavities (nests) inside a watermelon.

(bl Conventional technology In general, regarding classification of fruits such as watermelon by size and weight, for example, Japanese Patent Laid-Open No. 57-19807
They are automatically sorted by the method shown in No. 9.

However, quality judgments such as fruit ripeness and the state of cavity (nest) formation are difficult to automate and are carried out exclusively by hand.

(C) Problems to be Solved by the Invention In such quality inspections based on human judgment, variations occur depending on the skill level and individual differences of the inspectors, as well as depending on the day and time of day, and the reliability is not sufficient. There wasn't. In addition, since work efficiency and judgment accuracy are contradictory, it is particularly effective for quality inspection of watermelons to eliminate the disadvantage of requiring a large number of inspectors to judge a large amount of fruit within a certain amount of time. As an example, Japanese Patent Application Laid-open No. 62-4466
No. 0 and Japanese Unexamined Patent Publication No. 58-750 disclose a method in which watermelon is subjected to vibrations or blows and its quality is determined based on the response. In particular, since the latter method evaluates quality by focusing on the power vector of the impulse response, it is expected that the reliability of the test results will be high. However, since this method uses multiple parameters individually, it requires complicated determination processing.

SUMMARY OF THE INVENTION An object of the present invention is to provide an apparatus that solves the above-mentioned conventional problems and, in particular, can automatically and easily determine the presence or absence of cavities in a watermelon.

(d) Means for Solving the Problems The device for determining the presence or absence of cavities in watermelon according to the present invention comprises: impulse impact generating means that applies an impulse impact of a constant intensity to the watermelon from the outside; an acoustic sensor that detects vibrations of the watermelon; A power spectrum analysis means that amplifies the detection signal of this acoustic sensor and obtains a power spectrum, and a sound pressure level of a first resonance point that occurs on the low frequency side on the power spectrum, and a sound pressure level that occurs on the high frequency side of the first resonance point. It is characterized by comprising a sound pressure level difference determining means for extracting the sound pressure level at the second resonance point and determining the presence or absence of a cavity based on the difference between the two sound pressure levels.

(e) Effect According to experiments conducted by the inventors, the difference in impulse response characteristics due to the presence or absence of a cavity in a watermelon is the difference between the sound pressure level at the first resonance point and the sound pressure level at the second resonance point in its power spectrum. It has become clear that this appears. In other words, if there is no cavity inside the watermelon, the sound pressure level at the first resonance point will be lower than the second resonance point.
The sound pressure level at the resonance point will be higher than the sound pressure level at the resonance point, but if there is a cavity, the level difference will be small (and depending on the degree of the cavity, the sound pressure level at the second resonance point will be higher than the sound pressure level at the first resonance point. It became clear that

This is because if there is a cavity inside the watermelon, the vibration system is separated in the cavity, so the sound pressure level at the first resonance point, which is the fundamental resonance frequency, decreases, and the sound pressure level at the first resonance point, which is the fundamental resonance frequency, decreases. This is thought to be because the sound pressure level at the resonance point becomes stronger.

In the apparatus for determining the presence or absence of cavities in a watermelon according to the present invention, the impulse impact generating means applies an impulse impact of a constant intensity to the watermelon from the outside. The acoustic sensor detects the impulse response waveform, and the power spectrum analysis means determines the power spectrum of the impulse response waveform. moreover,
The sound pressure level difference determination means extracts the sound pressure level of a first resonance point that occurs on the low frequency side on the power spectrum and the sound pressure level of a second resonance point that occurs on the high frequency side of the first resonance point, and The presence or absence of a cavity is determined based on the difference in level. Therefore, the sound pressure level difference determining means can determine the presence or absence of a cavity based on this level difference.

(f) Embodiment FIG. 1 is a block diagram of an apparatus for determining the presence or absence of cavities in watermelon, which is an embodiment of the present invention. In the figure, 6 is a device that applies an impulse impact of a constant intensity to the watermelon, and a rod 4 is attached to a hard rubber ball 2, and the rod 4 is attached to a support base 5 so as to be slidable in the horizontal direction. Further, a coil spring 3 is inserted between the support base 5 and the rubber bulb 2, and the rubber bulb 2 is configured to give an impulse impact to the belly of the watermelon l by the repulsive force of the coil spring 3. The watermelon 1 is placed on an installation stand 20 made of urethane foam or the like in order to avoid vibration noise from the stand and to prevent changes in vibration mode due to the watermelon's own weight. An impact is applied to the hard rubber ball 2 along a straight line that passes through the center of the watermelon 1 and intersects perpendicularly with the vertical axis (the straight line connecting the stem and navel). rubber ball 2
A suction cup-shaped acoustic sensor 7 is brought into close contact with the back side facing the. Therefore, this acoustic sensor 7 detects an impulse response waveform in response to the impulse impact given by the rubber ball 2. The amplifier circuit 8 amplifies the detection signal of the acoustic sensor 7, and the A-D converter 9 converts this into digital data. The CPU I inputs this data via the I10 port 10 and sequentially writes it into the RAM 12. R
After importing the data into the AM 12, the CPU II calculates the power spectrum of the content using the FFT method. Furthermore, R0M
13, the processing procedure of the CPU II described above is written in advance. The CPU 14 uses the R via the interface 15.
The power spectrum data obtained from AM12 is read, and the presence or absence of a cavity is determined based on the difference between the sound pressure level at the first resonance point and the sound pressure level at the second resonance point through a predetermined process described later.■10 baud) 1B Display is performed on the display 19 via the. The processing procedure of the CPtJ14 is written in advance in the ROM 16, and the RAM 17 is used as a working area.

FIG. 2 shows the structure of the acoustic sensor. The acoustic sensor consists of a suction cup part 7a that sticks to the belly part of the watermelon, and a piezoelectric element 7b embedded inside the suction cup part 7a. The suction cup part 7a is made of soft urethane rubber with a hardness of 35° and shaped into a spherical shell.
With this acoustic sensor attached to the watermelon, the piezoelectric element pick-amplifies vibrations directly through the urethane rubber. Therefore, there is no attenuation in the high frequency range compared to the case where vibration sound is collected through the air.

Examples of power spectra obtained from the detection signal of the acoustic sensor using the impulse impact generator and acoustic sensor described above are shown in FIGS. 4(A) and 4(B). In the example shown in FIG. 5A, the sound pressure level of the first resonance point occurring on the lowest frequency side is higher than the sound pressure level of the second resonance point C occurring on the higher frequency side than this first resonance point. A watermelon exhibiting an impulse impact response with such a power spectrum has no cavities. On the other hand, as shown in FIG. 3B, a watermelon exhibiting a response in which the sound pressure level at the first resonance point d is lower than the sound pressure level at the second resonance point e has a cavity inside.

The CPU 4 shown in FIG. 1 determines the above characteristics from the power spectrum of the impulse response waveform obtained in the RAM 12 to determine the presence or absence of a cavity.

The processing procedure is shown in FIG. First, power spectrum data is read, its envelope is determined, and the frequencies at which the maximum occurs are extracted in order from the low frequency side by determining the difference between the envelopes. Next, the sound pressure level of the maximum frequency existing within 100 to 150 Hz is determined as A. Furthermore, the maximum frequency at 150 to 200H2, that is, the second
Find the sound pressure level at the resonance point in B. After that, if the sound pressure level B at the second resonance point is lower than the sound pressure level A at the first resonance point, a correct result is displayed, and if the sound pressure level A at the first resonance point is lower than the sound pressure level B at the second resonance point, a correct result is displayed. If the hollow fruit is displayed.

In addition, in the example, the time when the sound pressure level of the first resonance point and the second resonance point are equal was set as the threshold value for determining the presence or absence of a cavity.
The sound pressure level difference serving as the threshold value can be determined as appropriate depending on the size and variety of the watermelon.

In addition, in the embodiment, the acoustic sensor is used in close contact with the watermelon, but other methods include, for example, making the pickup part into a pin shape and having the tip of the pin contact the watermelon, or making the tip of the bottle pierce. You can also do that.

(g) Effects of the Invention As described above, according to the present invention, the presence or absence of a cavity is determined by focusing on the sound pressure level difference between the first resonance point and the second resonance point in the power spectrum of the impulse response waveform. This eliminates the need for arithmetic processing using a large number of parameters, allowing determination to be made in a short time. Therefore, it is possible to perform a large number of determination tasks within a limited amount of time.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an apparatus for determining the presence or absence of cavities in watermelon, which is an embodiment of the present invention. FIG. 2 is a diagram showing the configuration of an acoustic sensor used in the device. FIG. 3 is a flowchart showing the processing procedure of the main parts of the device. FIGS. 4(A) and 4(B) are diagrams showing examples of power spectra obtained by the same apparatus. l-watermelon, 6-impulse impact generator, 7-acoustic sensor.

Claims (1)

[Claims] (1) Impulse impact generating means that applies an impulse impact of a constant intensity to the watermelon from the outside, an acoustic sensor that detects vibrations of the watermelon, and a power spectrum analysis that amplifies the detection signal of this acoustic sensor and calculates the power spectrum. extracting the sound pressure level of the first resonance point that occurs on the lower side of the power spectrum and the sound pressure level of the second resonance point that occurs on the higher side of the first resonance point, and extracting the difference between the two sound pressure levels. A device for determining the presence or absence of a cavity in a watermelon, comprising a sound pressure level difference determining means for determining the presence or absence of a cavity.