FR2635993A1 - Method and device for sorting employing the study of sounds, applied to the field of cultivating fish - Google Patents

Abstract

The invention relates to a method and device for sorting employing the study of sounds, applied to the field of cultivating fish. The shellfish are conveyed by means of a conveyor to a means capable of imparting a shock to them. They fall, for example, one by one onto an acoustically dead block consisting of a stainless steel plate attached to a concrete block. The sound emitted under the effect of the shock is collected, amplified, filtered, processed by an appropriate electronic circuit which, as a function of the result, controls a flap which directs the shellfish into one or other of the directions f1 and f2. The invention applies to sorting shellfish, in particular before packaging them.

Description

METHOD AND DEVICE FOR SORTING
IMPLEMENTING THE STUDY OF SOUNDS,
APPLIED TO AQUACULTURAL FIELD.

 The invention relates to a method and a sorting device implementing the study of sounds, applied to the domeine aquaccle.

 The sorting of shells consists in separating the good shells from the bad shells, and intervenes at the levels of the production, the harvest and especially the marketing.

 There is an empirical method commonly used, especially by the ostrellulturists, to eliminate oysters unsuitable for consumption, and which consists in manually striking an oyster considered good against a second oyster to be tested. An oyster that is bad (dead) is more or less open because the adductor muscle no longer compresses the ligament of the hinge which then spreads the valves. When an open oyster is struck, a stronger and more colored sound is obtained than that which, all things being equal, is given by a closed oyster.

 The importance of eliminating the oysters consumed by others from the point of packaging for marketing is understandable. However, it turns out that, in order to take account of the laws of the market, the conditioning of shellfish in general and oysters in particular is being done more and more by means of more and more efficient packaging lines. It is therefore less and less a question of treating menuellen: ent the qualitative sorting of the good and the oysters.

 A system for sorting objects comprising a percussion system and an electronic sound analysis device associated with an automatic object separation system is claimed in the French patent application 2,298,377 filed on January 27, 1975. The application to Aquaculture field is cited mrds is not the subject of any description sufficient means to implement to achieve the desired result.

 The present invention specifically aims to describe a sorting device capable of being integrated into a shellfish packaging line, including oysters. This device is based on numerous observations and measurements made by the Applicant that have highlighted a relationship between the quality of the shell and the frequent.ce of main resonance.

 The invention relates more specifically to a method of sorting shellfish using the study of sounds; characterized in that it consists in filtering the frequency spectrum of the sounds emitted by the shocked shell, by at least one band-pass filter, to integrate the energy over a given time and to compare the signal with a value threshold.

The invention will be better understood with the help of the explanations that follow and the attached figures among which:
- Figure 1 schematically illustrates a first embodiment of a sorting device according to the invention;
- Figure 2 - schematically illustrates a second embodiment of a device according to the invention;
- Figure 3 is a diagram illustrating an embodiment of a conveyor adapted to the variant of Figure 2;
FIG. 4 illustrates a variant of the electronic circuit for analyzing the sound;
FIGS. 5 and 6 are curves illustrating the method implemented by means of the device according to the invention;
FIG. 7 is another variant of the electronic circuit for analyzing the sound;
- Figures 8 and 9 are curves illustrating the method of implementation of the device according to the invention.

 For the sake of clarity, the same elements carry the same references in all the figures.

 The Applicant has carried out a certain number of analyzes of the sounds emitted by a shell, notably a closed oyster (live), and by the same open shell (dead), both being subjected, under certain conditions. , to an identical shock. He found that if the shock is caused on one of the valves, if the cavity is open, the sound escapes. This results in a main resonant frequency which is a function of the resonant volume dimensions and the aperture height. For a closed oyster, the vibration of the cavity is weaker because the two valves are held together, so that they do not vibrate relative to each other and the sound does not vibrate. hardly escapes.

The sorting method according to the invention is characterized in that it consists in studying the spectrum of the resonance frequencies of shells, in particular oysters, subjected one to one to shock. By way of example, for a closed oyster, the resulting sound consists of a multitude of frequencies of 1000
Hz at a few tens of KHz whose energy is damped after about 0.5 to 1 millisecond. For the open oyster, the same signal is obtained on which is superimposed at least one stronger frequency which is depreciated after about 4 to 6 milliseconds.

 In a first variant illustrated by means of FIG. 1, the oyster (1) is conveyed on a conveyor (2). When it reaches the end (A) of the conveyor (2), it tilts, falls and comes, following a path (151), to strike a soundproof block (150), an optical detector (7) is positioned on the trajectory ( 151) and a microphone (8) correctly placed to pick up the sound emitted during the collision of the eater (1) against the block (150).

 In this variant, the conveyor may have only one transfer band (2c) since the position of the oyster on the mat does not intervene. The essential thing is that the respective arrangement of the conveyor and the block (150) is such that the oyster necessarily comes to hit the block (150). The latter, according to a characteristic of the invention, must be insonore: the shock of the oyster must not cause vibration at its level. It can be a stainless steel plate behind which is glued a heavy material that absorbs sound, such as concrete for example.

 The optical detector (7) at the passage of an oyster (1) triggers the taking and the analysis of the sound. The output signal of the electronic circuit controls the flap (31) so that the oyster (1), which has just hit the block (150), is directed towards a path (fl) or (f2) depending on the signal sound analyzed.

The captured sound energy is amplified in an amplifier (10), filtered in a bandpass filter (11) before being rectified by a rectifier (12) to be integrated into an integrator (13). One of the outputs of the integrator (13) is connected to the input of a comparator (15) to be compared with a threshold value (s). A computer (20) receives and processes the information (signals a, b) provided respectively by the comparator (15), the optical cell (7), to control by a signal (d) an orientation system (30) consisting of a flap (31) leading rhiriant (1) which has just been shocked towards a path (fl) or (f2) as a function of the sound signal analyzed. A reset signal (z) completes the device.

 A second embodiment of a sorting device according to the invention is illustrated by means of FIG. 2. As in the previous case, the example chosen is the sorting of the oysters, but the process used is valid for all type of shells, only the values of the parameters change.

 An oyster (1) is placed on a flexible support (2) to avoid damping vibrations. An example of such a support is more particularly illustrated by means of FIG. 3. These are two strips (2a, 2b) separated from one another by a distance (d) chosen as a function of the size of the oyster (1) to allow passage to the organ responsible for causing a shock on IhLitre (1). The two strips (2a, 2b) are driven by any known means around the two drive guides (3, 4) of facor. to consist of a conveyor which serves as a flexible support (2), operating continuously and on which the oysters to be tested are positioned one by one manually or by an automatic system.

 The oyster (1) is positioned on the conveyor (2), concavity er.

base, so that it is in this position in front of a hammer (5) creed for example by an electromagnet, or a jack or any other equivalent means, itself actuated by a signal emitted by a detection cell (7) of arrival of Phttre (1) facing the matrix (5). The speed of movement of the latter is determined and kept constant. A microphone (8) picks up the sound emitted during the impact of the hammer (5) on the oyster (1). As in the previous variant, the sound energy captured is amplified in an amplifier (10), filtered in a bandpass filter (11) before being rectified by a rectifier (12) to be integrated into an integrator (13) One of the outputs of the integrator (13) is connected to the input of a comparator (15) to be compared with a threshold value (s). A computer (20) receives and processes the information (signals a, b) supplied respectively by the comparator (15), the optical cell (7), to control, from the signals (c, d), respectively the electromagnet ( 6) and an orientation system (30) consisting of a flap (31) leading the oyster (1) which has just been shocked to one way or the other depending on the sound signal analyzed. A reset signal (z) completes the device.

 In the two variants previously described, the bandpass filter (11) is a filter of 800 Hz at 2000 Hz and the integrator (13) integrates the energy over a time of 4 to 5 milliseconds. The stronger the signal, the more the oyster is open. Between a closed oyster and an open oyster, gold. gets level reports in the order of three to four.

 This solution has the advantage of being simple can be implemented for a large number of shellfish population, including dhctres. However, it may have disadvantages in certain cases, such as, for example, when the impact occurs on a part of the hull (1) covered with a small parasitic shell that breaks, or with an alga, or a stack of scales soaked with water, in short, a matter foreign to the oyster itself. This material indeed can absorb the shock and the sound obtained on an open oyster can descend to a level identical to that of a closed oyster. This disadvantage is overcome by repeating the measurement several times on the same oyster and averaging the measurement results: it is then this average that is compared to a determined threshold.

An alternative embodiment of the electronic circuit is illustrated by means of FIG. 4. This is characterized in this case by the implementation, at the output of the amplifier (10), of a plurality of N passband filters. (1a, 11b ... 11N) mounted in parallel. (N) is an integer of at least two. Each filter passes a fraction of the spectrum between 500 Hz and 2500
Hz, and this in a staggered manner. The output of each filter (11a) to (11N) is connected to a rectifier respectively referenced (12a) to (12N) followed by an integrator (13a) to (13N). The N voltage values (V) are thus obtained ( Va, Vb,
Vc, VN) corresponding to the N energies thus integrated. The calculator (200) determines if one of the energies is much higher than the sum of all the others, which indicates the presence of a main resonance of an open oyster. . Figures 5 and 6 show the curves of the voltage (V) as a function of frequency for a closed oyster (Figure 5) and for an open oyster (Figure 6) where there is a voltage (Vi) greater than one determined threshold, the oyster then is deemed open and therefore rejected.

 The advantage of this variant of the electronic circuit according to the invention with respect to the circuit shown in Figures 1 and 2 is that the force of the shock is no longer a determining factor.

FIG. 7, supplemented by FIGS. 8 and 9, illustrates another variant of an electronic circuit according to the invention. The amplifier (10) is connected to a bandpass filter (111) which is sufficiently wide to recover the resonance of the cavity, for example from 500 Hz to 2500 Hz. The output of the filter (111) is connected, via a rectifier (12), to an analog / digital converter (70) itself connected to a computer (300) which, according to the invention, raises the level of the signal (V) as a function of time (t), from its appearance during the shock to its disappearance, or after about 5 milliseconds. As shown by the two curves "V = shown in Figure 8 for a closed oyster and in Figure 9 for an open oyster, it is is an exponential function "V = V0.exponential (-t / t0>" where (VO) represents the amplitude at the beginning of the shock, (t) the time, (to) the time constant which is less than 0.5 ms for a closed oyster, and of the order of 3 ms for an open oyster From this series of numbers, the calculator (300) will determine the coefficient (to) which gives the closest exponential function. For this, we use the following formula:
to = (S3-S1S1 / N) / (S2-S1S7 / N)
N = number of measured values.

 53 = sum of 1 to N of (t12).

 S1 = sum of 1 to N of (ti).

 = = sum of 1 to N of (tiLogVi).

 S7 = sum of 1 to N of (LogVi).

 This (to) is compared to a threshold that allows you to sort the good oysters from the bad ones.

 The shellfish sorting device according to the invention finds its application in the aquaculture field, particularly in terms of shellfish packaging chains and more particularly oysters.

Claims (10)

 1. A method of sorting shellfish using the study of sounds; characterized in that it consists in filtering the frequency spectrum of the sounds emitted by the shocked shell, by at least one band-pass filter, to integrate the energy over a given time and to compare the signal with a threshold value .  2. A shell-sorting device employing the study of sounds according to claim 1; characterized in that it comprises a conveyor for conveying the shells to be tested, a means capable of creating a shock on each shell, a microphone intended to pick up the sound emitted during the shock of the oyster, and a detector intended to detect the passage shellfish being tested and to trigger an electronic circuit for analyzing the sound emitted during the impact.  3. Device according to claim 1, characterized in that the shock is created by the percussion of the seashell falling from the conveyor on a soundproof block.  4. Device according to claim 3, characterized in that this block is a stainless steel plate integral with a heavy material which absorbs sound such as concrete.  5. Device according to claim 2, characterized in that the conveyor is equipped with two strips (2a, 2b) separated from each other by a distance (d) allowing the passage of a hammer (5) intended to strike the shell, the operation of the hammer (5) being controlled by the detector (7).  6. Device according to one of claims 2 to 5, characterized in that the electronic analysis circuit is processed by a computer (20, 200, 300) which provides a signal actuating an orientation system (30) leading to oyster that has just been shocked to one (fl) or the other <f 2), depending on the sound signal analyzed.  7. Device according to one of claims 2 to 6, characterized in that the electronic circuit for analyzing the sound comprises an amplifier (10) of the sound emitted during the shock, a band-pass filter (11), a rectifier ( 12), an integrator (13), one of whose outputs is connected to a comparator (15).  8. Device according to one of claims 2 to 6, characterized in that the electronic analysis circuit comprises an amplifier (10) -relié to a plurality of N bandpass filters (1 la, lob ... lit) each filter being connected to a rectifier (12a ... 12N) followed by an integrator (13a ... 13N) providing N voltage values (Va, Vb ... VN), corresponding to N integrated energy.  9. Device according to one of claims 2 to 6, characterized in that the electronic analysis circuit comprises an amplifier (10) connected to a band-pass filter (111) connected, via a rectifier (12), to a analog / digital converter (70), itself connected to the computer (300).  10. Device according to claim 10, characterized in that the calculator (300) raises the signal level (V) as a function of time (t), of the form, V = VO.exponential (-t / tO), where VO represents the amplitude at the beginning of the shock, (t) the time, (to) the time constant intended to be compared with a threshold value.