NL1039247C2 - A method of separating scrap, and a device. - Google Patents

Description

100-580-45 A method of separating scrap, and a device

The present invention relates to a method of separating scrap comprising scrap items of a first type and of a second type, at least 5 one of said types of scrap comprising metal.

Such a method is known in the art. A scrap stream, e.g. electrical components being salvaged when stripping cars, is created by transporting scrap items on a conveyor belt. A camera is used to identify the type of scrap item on the conveyor belt using object 10 recognition and deflect a desired or undesirable scrap item of a first type so as to separate scrap items of the first type from the scrap items of the second type.

A disadvantage of the method is that it is rather expensive, requiring a camera, and powerful computer hardware to achieve a 15 commercially acceptable throughput is required as well.

The object of the present invention is to provide a relatively simple, more cost-effective method according to the preamble.

To this end, a method according to the preamble is characterized in that the method comprises the steps of 20 - projecting a beam of light from a light source onto a scrap item and moving said scrap item and the beam of light relative to each other so as to pass a spot of light over the surface of said scrap item, the beam of light having at the location of said spot of light a maximum dimension D in the direction of the relative movement of the beam of 25 light and the scrap item at the location of the spot of light on said scrap item of less than 5 mm; - performing a plurality of successive light intensity measurements of light reflected from the surface of said scrap item in time, the light being reflected from different locations of said 30 surface; - collecting data from said light intensity measurements, the collected data from at least two light intensity measurements of light reflected from a scrip item constituting a set of fingerprint data; - computing the type of scrap item based on said set of 35 fingerprint data; and - moving the scrap item to one of a first location and a location differing from said first location depending on the type of scrap as determined in the computing step.

1039247 2

Surprisingly it has been found that a set of fingerprint data representative of the surface characteristics of a scrap item can be sufficient to distinguish between two types of items without having to rely on an image or multitude of images. Light reflected from an item 5 can yield a fingerprint specific for that type of scrap item. Such a fingerprint can be considered a one-dimensional array, which is way simpler than the two-dimensional array obtained from a camera representing a picture of the scrap item, not in the least because a camera will in practice take many pictures of a single item, so the 10 state of the art method has to process many two-dimensional arrays, which are rather large. For an acceptable through-put, such camera's have to take pictures at a frequency well above what ordinary camera's do, and such special camera's are expensive. The present invention allows for the use of a simple sensor, such as a photocell. In general 15 and preferably, the beam of light and the scrap item will be moved relative to each other with a constant speed, as this will result in more accurate separations. However, it is not impossible to compensate for variations in said relative speed. In case of a scrap stream where the scrap items drop, the acceleration due to gravity can be 20 compensated for, but because the acceleration is otherwise constant, the fingerprints will reflect this and no compensation may be necessary in such a case. Moving a scrap item to a first location or other location can be done in any manner known in the art, e.g. with a robot arm, a piston pushing the item, etc. Typically, in the direction of the 25 relative movement of the spot of light over the scrap item the speed at which the spot moves over the surface of the scrap item is at least 1 m/s, preferably with a speed of at least 2 m/s. Computing will generally be performed using a computer, although in case of a neural network this is not strictly necessary. The plurality of light 30 intensity measurements will involve at least two measurements, but preferably more such as at least 10. In practice this number will be for example more than 50. While the locations from which light is reflected are different, they may overlap although that may not be particularly favourable. Preferably, in a set of fingerprint data there 35 will be data of non-overlapping areas.

According to a favourable embodiment, the first type of scrap items comprises scrap items from the group consisting of motors and transformers .

3

This is an important application of the present invention, and it has been found to work very well, despite scrap items being covered with some dust and/or rust as is the case in practice. Transformers are made up of plates, and motors have windings, both of which result in a 5 fingerprint markedly different from other types of scrap items such as lumps of steel and chunks of rock or stone that may be present.

According to a favourable embodiment, the beam of light has a maximum dimension D

in the direction of the relative movement of the beam of light and 10 the scrap item at the location of the spot of light on said scrap item of less than 3 mm, preferably less than 1 mm.

This allows for obtaining more information-rich fingerprints of each scrap item because smaller surface regularities/irregularities can be detected.

15 According to a favourable embodiment, the beam of light is a laser beam.

This allows for a narrow beam, increasing the amount of information of the signal reflected by the scrap item. Thus, a more reliable fingerprint can be obtained. Depending on the type of laser 20 used (e.g. a HeNe laser), it is quite simple to collimate and have a small spot size that hardly varies for different distances from the scrap item to the laser. In other words, the spot size will be adequate irrespective of the size of typical scrap items of a given type of scrap and there is no need for focusing depending on the size of the 25 scrap item.

According to a favourable embodiment, the angle between i) the beam of light and ii) the direction of the relative motion of the scrap item with respect to the beam of light, is fixed and at least 20°.

Phrased differently, the angle of the beam of light doesn't change 30 in time with respect to the vertical and to a horizontal plane. This avoids the use of fine-mechanical apparatus components such as rotary mirrors or prisms, wobbling mirrors etc., improving the reliability of the apparatus in an industrial environment. This embodiment is very easily achieved by moving scrap items of the scrap stream through the 35 beam of light, e.g. using a conveyor belt.

According to a favourable embodiment, the scrap items are supplied along a path and spaced apart and subsequently the spot of light is passed over said aligned scrap items.

4

The path will generally be straight, for example because the scrap items are transported on a conveyor belt at the center thereof. Thus a stream of scrap comprising the first and second types of scrap items can be sorted quickly and conveniently.

5 According to a favourable embodiment, for the light intensity measurements at least two different colours are sampled.

This provides additional information that can be used to distinguish type of scrap. Measuring different colours can be performed in many ways, e.g. using two different sensors, each sensitive at a 10 different wavelength or provided with band filters. It can, for example, also be accomplished using a single sensor and two different light sources. It is advantageous if the light sources work alternating, so as to avoid cross-talk.

According to a favourable embodiment, light intensity measurements 15 are performed for two different polarisations of light.

For optimum signals, the polarisations will be at right angles.

According to a favourable embodiment, the scrap items are on a support surface and the location where the beam of light hits the support surface if no scrap item is in the beam of light is outside the 20 field of view of a light sensor for performing light intensity measurements .

This results in a sharp drop in intensity measured by the light sensor, making it easy to determine the begin and the end of the path of the spot of light over the surface of the scrap item. This makes it 25 easy to establish the beginning and the end of the dataset to make up the fingerprint of said scrap item. Limiting the field of view may be done in any of a variety of ways, e.g. using a lens, or using an aperture opening (diaphragm).

Finally, the present invention relates to a device for separating 30 scrap items from scrap comprising scrap items of first type and of a second type, at least one of said types of scrap comprising metal, wherein the device comprises - a light source capable of emitting a beam of light; - means for moving the beam of light and a scrap item relative to 35 each other; - a sensor for performing light intensity measurements in time; - collecting means arranged in communication with the light intensity sensor and arranged for creating a set of fingerprint data 5 from at least two successive light intensity measurements obtained when the beam shines on an item of scrap; - computing means, arranged in communication with said collecting means, and arranged for computing the type of item from a set of 5 fingerprint data, related to a scrap item, obtained from the collecting means; and - an actuator means capable of causing the scrap item to move to one of a first and a second location, the second location differing from the first location, on the basis of the computed type of the scrap 10 item.

Such a device is suitable for use in the method according to the invention. The device will generally comprise an opaque housing to block at least 50% of ambient light. For the sake of brevity only so as to avoid repetition, the present invention also discloses the device 15 with any of the modifications described in the above method claims, in any combination thereof, by reference to the above text and in particular the device features thereof.

The present invention will now be illustrated with reference to the drawing where 20 Fig. 1 shows a schematic cross-sectional view of a device for separating scrap items; and

Fig. 2 shows a flow diagram of signal processing steps.

Fig. 1 shows a device 100 for separating scrap items 101. In the embodiment shown here, the device 100 comprises a conveyor belt 102 for 25 transporting scrap items 101. Over the conveyor belt 102 there is a housing 103 for excluding ambient light to a major extent, said housing 103 having an inlet opening 104 and an outlet opening 105. The housing 103 is provided with a first light source 111 with a first light detector 121. This allows for obtaining data from specular reflection 30 and scattering properties of the surface of the scrap items 101.

In accordance with a preferred embodiment, further data are obtained concerning the colour properties of the scrap items 101. To this end, the embodiment shown here comprises a second light source 112 and a third light source 113. A beam splitter cube 114 allows 35 superposition of the beams from said second light source 112 and third light source 113. A cylindrical lens 115 is provided to diverge the beam of light coming from said second light source 112 and third light source 113. To detect the light, there is a second light detector 122.

6

In the present embodiment the light sources are lasers. For separation of scrap items 101 containing copper, the second light source 112 and third light source 113 are for example blue and red. The light sources can work intermittently in an alternating way, so as to 5 avoid cross-talk. The use of filters is thus avoided. Instead of two light sources, one could use a single white light source and use two light detectors, one for each colour.

Scrap items 101 are transported by the conveyor belt 102 through the housing 103. The first light source 111 projects a spot of light 10 onto said scrap item 101 and light reflected by the scrap item 101 is detected by the first light detector 121. An electrical signal from the first light detector 121 is passed to a multiplexer 130 and from there to an analog-digital converter 131. Similarly, the signal from the second light detector 122 is passed to the multiplexer 130 and the 15 analog-digital converter 131.

The signal from the analog-digital converter 131, constituting a set of fingerprint data, is passed to a computer 132, where the signal is processed as detailed below, resulting in the determination of the scrap item type. This determination may be a positive one; i.e. the 20 scrap item belongs to a particular type. It may also be a negative one, that the scrap item does not belong to a known scrap item type. Irrespective of that, a decision can be made what to do with the scrap item. In the embodiment shown here, the computer 132 controls a motor 141 capable of rotating a deflector plate 142 at the end of the 25 conveyor belt 102, so as to perform the separation. With a known speed of the conveyor belt 102, the computer 132 will take the time it takes from passing through the housing 103 to the location of the deflector plate 142 into account, thus deflecting the appropriate scrap item 101.

Fig. 1 also shows the field of view of the second light detector 30 122. It should be noted that without a scrap item 101 being present, the beam from the second light source 112 hits the conveyor belt 102 outside the field of view of the second light detector 122. This results in an improvement of the signal quality, helping in detecting the presence of a scrap item.

35 Fig. 2 shows a flow diagram of a convenient way of processing data from a light detector, such as the first light detector 121, in a process wherein motors and transformers were separated from lumps of steel. Because of the presence of windings or plates, the surface 7 characteristics differ from those of lumps of steel. The size of these scrap items 101 was 2 to 15 cm and their height was in the range of 5 to 50 mm. As a result of the varying height, the spot size had a dimension parallel to the belt between 0.2 and 0.5 mm. The scrap items 5 101 were positioned in a longitudinal direction on the belt 102. The belt 102 moved with a speed of 3 m/s and the sampling frequency of the ADC convertor (14 bit) was 40 KHz.

The signal from the ADC converter is subjected by a program run on computer 132 to a step to remove an off-set, for example caused by 10 background light that may have entered the housing 103. This increases the contrast for the second step, where the presence of a scrap particle is detected because the signal level exceeds a threshold value. This defines a data window and data from this data window is in the form of an array of data (i.e. what in the present application is 15 indicated as the set of fingerprint data) that may be subjected to a step to remove spikes in the data of the data window. Spikes are for example caused by dust in the air. Spike removal is, for example, performed by taking 5 consecutive data values, determining whether any of the data value numbers 2 to 4 are above a threshold value compared 20 to data value numbers 1 and 5. If so, then the data value numbers 2 to 4 are replaced by the average values of data value numbers 1 and 5. If not, no values of data value numbers are changed and the data value numbers 2 to 6 are examined similar as just described for data value numbers 1 to 5, etc. This results in pre-processed signal SO. The 25 threshold to discern what is a spike and what is not a spike depends on the particular circumstances (scrap items to be separated) and can easily be determined, using the raw data stream from the ADC converter 131 and looking at outliers.

The pre-processed signal SO is subjected to a step wherein a 1 mm 30 moving average is determined. That is, all the data values obtained while a scrap item 101 moved over a distance of 1 mm on the belt 102 are averaged. This results in a signal SI. The difference between SO and SI represents high frequencies and is signal S2.

Signal SI is subjected to a step wherein a 4 mm moving average is 35 determined, resulting in signal S4, representative of low frequencies.

The difference between SI and S3 is representative of intermediate frequencies (signal S4).

The signals SO to S4 are used to calculate a simplified data set, 8 called extracted data. These extracted data are then fed into an Adaboost program. Adaptive boosting is a well-known technique for machine learning and classification. Reference: Adaptive Boosting (Adaboost), a machine learning algorithm formulated by Yoav Freund and 5 Robert Schapire. (A Decision-Theoretic Generalization of on-Line

Learning and an Application to Boosting (1995)). Several open source programs are available, see for example wikipedia (http://en.wikipedia.org/wiki/AdaBoost) .

For classification, the person skilled in the art may instead 10 employ any other of various techniques well disclosed in the art. For example: Principal Components Analysis (http://www.cs.otago.ac.nz/ cosc453/student_tutorials/principal_components.pdf) and linear discriminant analysis.

Training was done with 30-50 scrap items of each type.

15 To process colour-based information from the second light detector 122, this too was subjected to signal processing as disclosed above, but separating the data belonging to light from the second light source 112 and the third light source 113 first, based on the time when light was emitted. This results in two additional data arrays, allowing 20 further computational parameters to be calculated. For example, the difference in signal strength between the data of said colours can be used as a signal S5.

The method according to the present invention has been found to be more accurate (>80%) than a human sorter (50-60%), whose accuracy is 25 subject to concentration and motivation. The present method is also much faster. To achieve the above results, the features extracted from SO to S4 and fed to the Adaboost program were 1. mean[ abs(S2) ) / max(SI) 2. mean[ abs(S2) / SI ] 30 3. meant abs(S2) > 0.3*max(abs(S2)) ) where abs means the absolute value of and max means the maximum value of. The last feature (feature 3) is a logical operation. IF the absolute value of an S2 value in the data array for this scrap item is larger than 30% of the largest S2 value, THEN it is assigned a value of 35 1, ELSE it is assigned a value of 0. The average of all ones and zero's is determined to result in a single value for feature 3. Thus the original light signal measured from the scrap item 101 is reduced to three values, which are fed to the Adaboost program. It is believed 9 that a further improved sorting result can be obtained by reducing the sensitivity for a single maximum (max) value, e.g. by using the average of the 10% highest values. It should be noted that, the Adaboost program is trained using scrap items of the various types, the training 5 being done under particular circumstances (e.g. speed of the conveyor belt, sampling frequency etc.) a change in circumstances may need retraining to achieve the desired quality of separation.

With the method according to the.present invention, further optical properties may be exploited, in particular polarization. To 10 this end and by way of example, the second light source 112 and the third light source 113 may be linearly polarized lasers angled and operated such that the scrap item 101 is subjected alternately to H and V polarized light. This is e.g. useful for separating metals from dielectric materials such as stones. Alternatively, a non-polarized or 15 circularly polarized light source may be used, with two sensors each provided with a polarization filter to detect the desired H and V component.

The use of a V-shaped conveyor belt set-up facilitates orientation of scrap items for high through-put purposes.

1039247

Claims (10)

1. Werkwijze voor het scheiden van schroot welke stukken schroot (101) van een eerste type en van een tweede type omvat, waarbij ten minste 5 één van de genoemde schroottypes metaal omvat, met het kenmerk, dat de werkwijze de stappen omvat van - het projecteren van een lichtbundel van een lichtbron (111) op een stuk schroot (101) en het ten opzichte van elkaar bewegen van het genoemde stuk schroot (101) en de lichtbundel teneinde een lichtplek 10 over het oppervlak van het genoemde stuk schroot (101) te bewegen, waarbij de lichtbundel op de plaats van de genoemde lichtplek een maximale afmeting D bezit in de richting van de relatieve beweging van de lichtbundel en het genoemde stuk schroot (101) op de plaats van de lichtplek op het genoemde stuk schroot (101 van minder dan 5 mm; 15. het uitvoeren van een veelheid van achtereenvolgende lichtintensiteit-metingen van licht dat door het oppervlak van het genoemde stuk schroot (101) wordt weerkaatst in tijd, waarbij het licht door verschillende plaatsen van het genoemde oppervlak wordt weerkaatst; 20. het verzamelen van gegevens van de genoemde lichtintensiteit-metingen, waarbij de verzamelde gegevens van ten minste twee lichtintensiteit-metingen van door een stuk schroot (101) weerkaatst licht een set vingerafdruk-gegevens vormen; - het berekenen van het type van het stuk schroot (101) gebaseerd op de 25 genoemde set vingerafdruk-gegevens; en - het bewegen van het stuk schroot (101) naar één van een eerste plaats en een plaats die anders is dan de genoemde eerste plaats afhankelijk van het type schroot zoals bepaald in de bereken-stap. 30A scrap separation method comprising scraps (101) of a first type and a second type, wherein at least one of said scrap types comprises metal, characterized in that the method comprises the steps of - projecting a light beam from a light source (111) onto a scrap piece (101) and moving said scrap piece (101) and the light beam relative to each other to create a light spot 10 over the surface of said scrap piece (101) wherein the light beam at the location of said light spot has a maximum dimension D in the direction of the relative movement of the light beam and said scrap piece (101) at the location of the light spot on said scrap piece (101 of less than 5 mm; 15. performing a plurality of successive light intensity measurements of light reflected from the surface of said scrap piece (101) in time, the light being transmitted by distant different locations of said surface is reflected; 20. collecting data from said light intensity measurements, wherein the collected data from at least two light intensity measurements of light reflected by a piece of scrap (101) form a set of fingerprint data; - calculating the type of scrap piece (101) based on said set of fingerprint data; and moving the scrap piece (101) to one of a first location and a location other than said first location depending on the type of scrap as determined in the calculating step. 30 2, Werkwijze volgens conclusie 1, waarbij de stukken van het eerste type schroot (101) stukken schroot (101) omvat van de groep bestaande uit motoren en transformatoren.The method of claim 1, wherein the pieces of the first type of scrap (101) comprise pieces of scrap (101) from the group consisting of motors and transformers. 3. Werkwijze volgens conclusie 1 of 2, waarbij de lichtbundel een 35 maximale afmeting D heeft in de richting van de relatieve beweging van de lichtbundel en het stuk schroot (101) op de plaats van de lichtplek op het genoemde stuk schroot van minder dan 3 mm, bij voorkeur minder dan 1 mm. 1 0 3 9 2 4 73. Method according to claim 1 or 2, wherein the light beam has a maximum dimension D in the direction of the relative movement of the light beam and the scrap piece (101) at the location of the light spot on said scrap piece of less than 3 mm, preferably less than 1 mm. 1 0 3 9 2 4 7 4. Werkwijze volgens een der voorgaande conclusies, waarbij de lichtbundel een laserbundel is.A method according to any one of the preceding claims, wherein the light beam is a laser beam. 5. Werkwijze volgens een der voorgaande conclusies, waarbij de hoek tussen i) de lichtbundel en ii) de richting van de relatieve beweging van het stuk schroot (101) ten opzichte van de lichtbundel, vast is en ten minste 20° is.A method according to any one of the preceding claims, wherein the angle between i) the light beam and ii) the direction of the relative movement of the scrap piece (101) with respect to the light beam is fixed and is at least 20 °. 6. Werkwijze volgens een der voorgaande conclusies, waarbij de stukken schroot (101) langs een pad en op een afstand van elkaar worden aangevoerd en de lichtplek vervolgens over de genoemde uitgelijnde stukken schroot (101) wordt bewogen.A method according to any one of the preceding claims, wherein the scrap pieces (101) are supplied along a path and at a distance from each other and the light spot is subsequently moved over said aligned scrap pieces (101). 7. Werkwijze volgens een der voorgaande conclusies, waarbij voor de lichtintensiteit-metingen ten minste twee verschillende kleuren worden bemonsterd.A method according to any one of the preceding claims, wherein at least two different colors are sampled for the light intensity measurements. 8. Werkwijze volgens een der voorgaande conclusies, waarbij 20 lichtintensiteit-metingen voor twee verschillende lichtpolarisaties worden uitgevoerd.8. A method according to any one of the preceding claims, wherein light intensity measurements are carried out for two different light polarizations. 9. Werkwijze volgens een der voorgaande conclusies, waarbij de stukken schroot (101) zich op een drageroppervlak bevinden en de plaats waar de 25 lichtbundel het drageroppervlak raakt wanneer zich geen stuk schroot (101) in de lichtbundel bevindt, zich buiten het gezichtsveld van een lichtsensor voor het uitvoeren van lichtintensiteit-metingen bevindt.9. Method as claimed in any of the foregoing claims, wherein the scrap pieces (101) are located on a carrier surface and the place where the light beam touches the carrier surface when there is no scrap piece (101) in the light beam is outside the field of view of a light sensor for performing light intensity measurements. 10. Inrichting (100) voor het afscheiden van stukken schroot (101) uit 30 schroot dat stukken schroot (101) van een eerste type en van een tweede type omvat, waarbij ten minste een van de genoemde schroottypes metaal omvat, met het kenmerk, dat de inrichting (100) - een lichtbron (111) omvat die in staat is om een lichtbundel uit te zenden; 35. middelen (102) voor het ten opzichte van elkaar bewegen van de lichtbundel en een stuk schroot (101); - een sensor (121) voor het uitvoeren van lichtintensiteit-metingen in de tijd; - verzamelmiddelen (131) ingericht in communicatieve verbinding met de lichtintensiteit-sensor (121) en ingericht voor het creëren van een set vingerafdruk-gegevens uit ten minste twee achtereenvolgende lichtintensiteit-metingen die zijn verkregen wanneer de bundel op een l 5 stuk schroot (101) schijnt; - bereken-middelen (132) in communicatieve verbinding met de genoemde verzamelmiddelen (131), en ingericht voor het berekenen van het type van een stuk (101) uit een set vingerafdruk-gegevens, gerelateerd aan een stuk schroot (101), verkregen uit de verzamelmiddelen (121); en 10. een actuator-orgaan (142) dat in staat is om het stuk schroot (101) naar één van een eerste en een tweede plaats te laten bewegen, waarbij de tweede plaats anders is dan de eerste plaats, op basis van het berekende type schroot (101). 103924710. Device (100) for separating pieces of scrap (101) from scrap comprising pieces of scrap (101) of a first type and of a second type, wherein at least one of said scrap types comprises metal, characterized in that: that the device (100) - comprises a light source (111) capable of emitting a light beam; 35. means (102) for moving the light beam and a scrap piece (101) relative to each other; - a sensor (121) for taking light intensity measurements over time; - collecting means (131) arranged in communication with the light intensity sensor (121) and arranged for creating a set of fingerprint data from at least two consecutive light intensity measurements obtained when the bundle scrapes on a piece of scrap (101 ) appears; - calculating means (132) in communication with said collecting means (131), and adapted to calculate the type of a piece (101) from a set of fingerprint data related to a piece of scrap (101) obtained from the collection means (121); and 10. an actuator member (142) capable of moving the scrap piece (101) to one of a first and a second location, the second location being different from the first location, based on the calculated scrap type (101). 1039247