WO2023018336A1 - Procédé de détection de l'usure d'un filet - Google Patents

Procédé de détection de l'usure d'un filet Download PDF

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Publication number
WO2023018336A1
WO2023018336A1 PCT/NO2022/050192 NO2022050192W WO2023018336A1 WO 2023018336 A1 WO2023018336 A1 WO 2023018336A1 NO 2022050192 W NO2022050192 W NO 2022050192W WO 2023018336 A1 WO2023018336 A1 WO 2023018336A1
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WO
WIPO (PCT)
Prior art keywords
subsea
net
assembly
image
unit
Prior art date
Application number
PCT/NO2022/050192
Other languages
English (en)
Inventor
Hans Einar Jakobsen
Håvard LILLEBO
Original Assignee
Watbots As
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from NO20210975A external-priority patent/NO347478B1/en
Application filed by Watbots As filed Critical Watbots As
Priority to GB2401919.2A priority Critical patent/GB2624333A/en
Priority to CA3228647A priority patent/CA3228647A1/fr
Publication of WO2023018336A1 publication Critical patent/WO2023018336A1/fr
Priority to DKPA202430086A priority patent/DK202430086A1/en

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Classifications

    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/10—Segmentation; Edge detection
    • G06T7/13—Edge detection
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63C—LAUNCHING, HAULING-OUT, OR DRY-DOCKING OF VESSELS; LIFE-SAVING IN WATER; EQUIPMENT FOR DWELLING OR WORKING UNDER WATER; MEANS FOR SALVAGING OR SEARCHING FOR UNDERWATER OBJECTS
    • B63C11/00—Equipment for dwelling or working underwater; Means for searching for underwater objects
    • B63C11/52—Tools specially adapted for working underwater, not otherwise provided for
    • A—HUMAN NECESSITIES
    • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
    • A01K—ANIMAL HUSBANDRY; AVICULTURE; APICULTURE; PISCICULTURE; FISHING; REARING OR BREEDING ANIMALS, NOT OTHERWISE PROVIDED FOR; NEW BREEDS OF ANIMALS
    • A01K63/00—Receptacles for live fish, e.g. aquaria; Terraria
    • A01K63/10—Cleaning bottoms or walls of ponds or receptacles
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
    • G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/88—Investigating the presence of flaws or contamination
    • G01N21/94—Investigating contamination, e.g. dust
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/88—Investigating the presence of flaws or contamination
    • G01N21/95—Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
    • G01N21/9515—Objects of complex shape, e.g. examined with use of a surface follower device
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/88—Investigating the presence of flaws or contamination
    • G01N21/95—Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
    • G01N21/952—Inspecting the exterior surface of cylindrical bodies or wires
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/10—Segmentation; Edge detection
    • G06T7/136—Segmentation; Edge detection involving thresholding
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/10—Segmentation; Edge detection
    • G06T7/194—Segmentation; Edge detection involving foreground-background segmentation
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/60—Analysis of geometric attributes
    • G06T7/62—Analysis of geometric attributes of area, perimeter, diameter or volume
    • A—HUMAN NECESSITIES
    • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
    • A01K—ANIMAL HUSBANDRY; AVICULTURE; APICULTURE; PISCICULTURE; FISHING; REARING OR BREEDING ANIMALS, NOT OTHERWISE PROVIDED FOR; NEW BREEDS OF ANIMALS
    • A01K61/00—Culture of aquatic animals
    • A01K61/60—Floating cultivation devices, e.g. rafts or floating fish-farms
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D55/00—Endless track vehicles
    • B62D55/08—Endless track units; Parts thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D55/00—Endless track vehicles
    • B62D55/08—Endless track units; Parts thereof
    • B62D55/18—Tracks
    • B62D55/26—Ground engaging parts or elements
    • B62D55/265—Ground engaging parts or elements having magnetic or pneumatic adhesion

Definitions

  • the present disclosure relates to the field of maintenance of fish pens.
  • Biofouling of fish pens is a major issue in the fish farming industry. Algae and other biological compounds contaminate the nets of fish pens, which causes inter alia reduced health for the fish, reduced oxygen supply to the fish pen, and increased difficulty in inspecting wear of the fish pen.
  • Several approaches have been employed in order to address biofouling related issues, including hoisting and pressure cleaning the nets, as well as the employment of separate underwater remotely operated vehicles (ROVs) that clean the net while submerged.
  • ROVs underwater remotely operated vehicles
  • NO 20161708 describes an assembly for carrying out a cleaning operation on a net, where the assembly comprises a first unit and a second unit configured to be positioned on opposite sides of the net to be cleaned.
  • the first and second units of the assembly adhere to one another and to the net to be cleaned by magnetic attraction and move across the net while cleaning the net using a cleaning system, such as a steam unit, an ultrasound unit, a high-pressure washing unit, or a water suction unit.
  • a cleaning system such as a steam unit, an ultrasound unit, a high-pressure washing unit, or a water suction unit.
  • the assembly of NO 20161708 does, however, cause wear of the net of the pish pen, which may eventually cause a hole in the net to form and consequently allowing farmed fish escape into the wild. In order ensure that the net is intact and that the wear of the net is within acceptable levels, it is necessary to investigate the net regularly, for example by hoisting the net out of the sea for manual inspection.
  • a first aspect of the present disclosure provides a method for determining the strand thickness of at least one strand of a submerged net, the method comprising the steps of moving a subsea assembly across the submerged net while the subsea assembly adheres to the net, collecting image data from a line camera of the subsea assembly as the subsea assembly adheres to and moves across the submerged net, generating, by an on-board computer of the subsea assembly, a two-dimensional image of a portion of the submerged net based on the received image data, and determining, by the on-board computer of the subsea assembly, the strand thickness of the at least one strand of the submerged net based on the two-dimensional image.
  • a second aspect of the present disclosure provides a computer-implemented method for determining the strand thickness of at least one strand of a submerged net, the method comprising receiving image data from a line camera of a subsea assembly as the subsea assembly adheres to and moves across the submerged net, generating a two-dimensional image of a portion of the submerged net based on the received image data, and determining the strand thickness of the at least one strand of the submerged net based on the two- dimensional image.
  • determining the strand thickness of the strand of the submerged net comprises the step of converting the two- dimensional image into a first binary image, where Each pixel of the first binary image represents a corresponding pixel in the two-dimensional image, where Each pixel of the first binary image is assigned a first binary value if the brightness of the corresponding pixel in the two-dimensional image is above/below a first predetermined threshold, and where Each pixel of the first binary image is assigned a second binary value if the brightness of the corresponding pixel in the two-dimensional image is below/above a first predetermined threshold, converting the first binary image into a distance map image, where Each pixel of the distance map image represents a corresponding pixel in the first binary image, and where Each pixel of the distance map image is assigned a value that denotes the distance between the corresponding pixel in the first binary image and the most proximate pixel to the corresponding pixel in the first binary image having the second binary value, assigning a zero
  • the computer-implemented method further comprises generating a data file containing information on the thickness of the at least one strand of the submerged net and the position of the at least one strand in the two-dimensional image.
  • a third aspect of the present disclosure provides a data processing apparatus comprising means for carrying out the method according to the second aspect of the invention.
  • a fourth aspect of the present disclosure provides a computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method according to the second aspect of the invention.
  • a fifth aspect of the present disclosure provides a computer-readable medium having stored thereon the computer program according to the second aspect of the invention.
  • a sixth aspect of the present disclosure provides a subsea assembly for imaging and analysing a submerged net, the subsea assembly comprising a first subsea unit for being positioned on a first side of the net, the first subsea unit comprising at least two pa rallelly oriented belt assemblies, and a line camera, a second subsea unit for being positioned on a second side of the net opposite to the first subsea unit, the second subsea unit comprising at least two parallelly oriented belt assemblies, where at least one of the first subsea unit and the second subsea unit further comprises an on-board computer configured perform the method according to the first aspect of the invention, and where each belt assembly comprises a track provided with magnets for generating an attractive force between the belt assemblies of the first subsea unit and the belt assemblies of the second subsea unit such that the subsea assembly adhere to the net.
  • the second subsea unit further comprises a background element, and where the line camera and the background element are arranged such that they face each other when the subsea assembly adhere to the net.
  • the first subsea unit and/or second subsea unit further comprises a light source.
  • the light source is integrated in the background element.
  • the light source has an elongated shape or the light source comprises a plurality of LEDs arranged in a line.
  • the first subsea unit further comprises a filter arranged in front of the line camera.
  • At least one of the first subsea unit and the second subsea unit further comprises a cleaning means for cleaning the net.
  • a seventh aspect of the present disclosure provides use of the subsea assembly for imaging and analysing a net or a sheet of a fish pen.
  • Figure la is a schematic representation of a subsea assembly according to the present disclosure where the second subsea unit comprises a background element
  • Figure lb is a schematic representation of the subsea assembly where one subsea unit is illustrated as partly transparent in order to visualise belt assemblies of the two subsea units adjoining each other,
  • Figure 2 is a schematic representation of a subsea assembly according to the present disclosure where the first subsea unit comprises a line camera,
  • Figure 3 is a schematic representation of a subsea assembly according to the present disclosure where the first subsea unit comprises a light source
  • Figure 4 is a schematic representation of a subsea assembly according to the present disclosure where the second subsea unit comprises a background element having an integrated light source,
  • Figure 5a is a schematic representation of a subsea assembly according to the present disclosure where the first subsea comprises a line camera,
  • Figure 5b is a schematic representation of a subsea assembly according to the present disclosure where the background element comprises a plurality of LEDs arranged in a line,
  • Figure 6 is a schematic representation of a subsea assembly according to the present disclosure where the first subsea unit comprises a filter arranged in front of the line camera,
  • Figure 7 is a schematic representation of a belt assembly where each road wheel and at least one damper wheel are provided with suspension,
  • Figure 8 is a representation of an image on a net captured by a line camera of a subsea assembly according to the present disclosure
  • Figure 9a is a schematic representation of a subsea assembly according to the present disclosure where the first subsea unit comprises a line camera that spans the whole width of the first cleaning unit,
  • Figure 9b is a schematic representation of a subsea assembly according to the present disclosure where the background element comprises a plurality of LEDs arranged in a line that spans the whole width of the second cleaning unit,
  • Figure 10a illustrates an example of a first binary image
  • Figure 10b illustrates an example of a distance map image
  • Figure 10c illustrates an example of a second binary images where the knots of the net have been filtered out
  • Figure 10b illustrates an image of a portion of the net where values in millimetres have been added for a couple of strands for illustrative purposes
  • Figure 11 is a schematic illustration of a subsea unit, illustrated with a transparent base, where the subsea unit comprises a driving unit and an onboard computer.
  • the present disclosure provides a subsea assembly 100 for imaging and analysing a submerged net 130, e.g. that of a fish pen.
  • the subsea assembly 100 according to the present disclosure comprises a first subsea unit 110 for being positioned on a first side of the net 130 and a second subsea unit 120 for being positioned on a second side of the net 130, opposite to the first subsea unit 110.
  • the first subsea unit 110 and second subsea unit 120 are, as schematically illustrated in figures la and lb, each provided with at least two parallelly oriented belt assemblies 150.
  • the first subsea unit 110 and second subsea unit 120 may according to any embodiment of the invention each be provided with two parallelly oriented belt assemblies 150.
  • first subsea unit 110 and second subsea unit 120 are each provided with two parallelly oriented belt assemblies 150.
  • a person skilled in the art with knowledge of the present disclosure will appreciate, however, that each embodiment of the present disclosure may be generalized such that at least one of the first subsea unit 110 and the second subsea unit 120 is/are provided with more than two parallelly oriented belt assemblies 150.
  • a belt assembly 150 may in the context of the present disclosure be understood by a person skilled in the art as the collection of wheels, track 160, bearings, supports, etc. necessary to enable continuous track propulsion of the subsea units, and hence the subsea assembly 100.
  • Each belt assembly 150 may as schematically illustrated in figures la and lb for example comprise a rear road wheel 170, optionally one or more middle road wheels 180, a front road wheel 190 and a track 160. Additional elements such as bearings, fastening mechanisms etc., may be provided in a variety of ways as will be appreciated by a person skilled in the art with knowledge of the present disclosure.
  • a belt assembly 150 or more generally a subsea unit 110,120, may further be considered as comprising a driving unit 380 for enabling the belt assembly to provide continuous track propulsion for the subsea unit 110,120 to which it belongs.
  • a driving unit 380 may for example comprise a battery, and a conventional motor, or alternatively a motor in the hub of any one or more wheel of the belt assembly 150.
  • Figure 11 schematically illustrates a subsea unit 110,120, illustrated with a transparent base, where the subsea unit 110,120 comprises a driving unit 380 and an on-board computer 382.
  • Each belt assembly 150 of the subsea units 110,120 may, as illustrated in figures la and lb, be arranged such that the ground pad 165 of the track 160 of each belt assembly 150 protrudes a non-zero distance from the underside of the relevant subsea unit 110,120.
  • each belt assembly 150 of the first subsea unit 110 may thus in other words be said to protrude a nonzero distance from the underside of the first subsea unit 110, while the ground pad 165 of each belt assembly 150 of the second subsea unit 120 may be said to protrude a nonzero distance from the underside of the second subsea unit 120.
  • the ground pad 165 of any belt assembly 150 may be interpreted as the part of a track 160 that lies between any two road wheels.
  • a ground pad 165 may thus be considered as a part of a track 160.
  • ground pad 165 of any track 160 may according to the present disclosure be considered as planar, or at least essentially planar, where "essentially planar" may be interpreted as meaning for example that the ground pad 165 of any belt assembly 150 may be tilted by ⁇ 10 degrees, or be at least in part wavy, e.g. due to the track 160 not being completely tight.
  • the first subsea unit 110 and second subsea unit 120 may, as schematically illustrated in figures la and lb, be arranged on opposite sides of the net 130.
  • the first subsea unit 110 and second subsea unit 120 may be aligned relative to one another such that the at least two belt assemblies 150 of the first cleaning 110 unit are aligned with and adjoin separate belt assemblies 150 of the second subsea unit 120.
  • the ground pad 165 of each respective track 160 of each belt assembly 150 of the first subsea unit 110 may, as schematically illustrated in figure lb, be positioned such that each said ground pad 165 adjoins the ground pad 165 of the track 130 of separate belt assemblies 150 of the second subsea unit 120.
  • FIG. lb one of the subsea units 110,120 of the subsea assembly 100 is schematically illustrated as partly transparent for illustrative purposes.
  • a net 130 may be present between any two ground pads 165 described as adjoining in the above context.
  • Figures la and lb illustrate an example where the first subsea unit 110 and second subsea unit 120 are positioned on opposite sides of a net 130 such that the ground pad 165 of the track 160 of each belt assembly 150 of the first cleaning 110 unit adjoins, via the net 130, a ground pad 165 of the track 160 of a belt assembly 150 of the second subsea unit 120.
  • the track 160 of each belt assembly 150 is, as schematically illustrated in figure lb, provided with magnets 210.
  • the magnets 210 are provided in order to generate an attractive force between the belt assemblies 150 of the first subsea unit 110 and the belt assemblies 150 of the second subsea unit 120 such that the subsea assembly 100 may adhere to a net 130.
  • a track 160 of a belt assembly 150 of the first subsea unit 110 may as a way of example comprise magnets 210 with a first polarity, while a track 160 of a belt assembly 150 of the second subsea unit 120 may comprise magnets 210 with a second polarity, opposite to the first polarity.
  • the magnets 210 in two, first and second, adjoining tracks 160 may, as a way of example, be such that all the magnets 210 of the first track 160 have the same polarity, while all the magnets 210 in the second track 160, adjoining the first track 160, have the opposite polarity of those in the first track 160.
  • Another example is that the magnets 210 in two adjoining tracks 160 may be such that any two adjacent magnets 210 in any one track 160 have opposite polarities, but where the tracks 160 of the two subsea units are adjoining each other with a relative shift such that magnets 210 of opposite polarities are adjoining/attracting one another.
  • the latter configuration may be utilized in order to counteract skidding of the tracks 160.
  • the subsea assembly may according to the present disclosure move across a net by means of the belt assemblies of the first subsea unit and the second subsea unit.
  • the adhesion to the net obtained by the magnetic attraction between adjoining tracks of the two subsea units will result in a grip for the subsea assembly such that movement is enabled.
  • Said grip may thus be termed a magnetically induced grip.
  • each belt assembly of the subsea assembly may operate as a continuous track vehicle propulsion system that is configured to operate under water, i.e. where each belt assembly is provided with one or more of a motor, gear system, water tight gaskets, power supply, etc.
  • the subsea units may generally be provided with other parts necessary for allowing the subsea assembly to move across a net.
  • parts may comprise e.g. watertight housing, transmitter, receiver, lighting device, battery, etc.
  • At least one of the first subsea unit and the second subsea unit may as a way of example comprise a driving unit, where the driving unit comprises at least one electric motor and a battery.
  • the electric motor may here be connected to one or more of the wheels of a belt assembly of the first subsea unit and/or the second subsea unit via for example a shaft or another suitable power transfer mechanism.
  • the first subsea unit and the second subsea unit may each comprise a driving unit as described above.
  • the subsea assembly 100 may, as illustrated in figures la and lb be provided with cleaning means 140 for cleaning a submerged net 130. Both or either of the first subsea unit 110 and the second subsea unit 120 may be provided with cleaning means 140.
  • Cleaning means 140 may according to the present disclosure be any suitable means for cleaning a net 130.
  • the subsea assembly 100 may be provided with one or more brushes, e.g. a rotating brush.
  • the one or more brushes may be provided on only one of the subsea units 110,120 or alternatively be distributed between the two subsea units 110,120.
  • a brush may brush against the net in order to clean the net of unwanted substances such a biofouling.
  • the cleaning means 140 may comprise a water-based cleaning means 140, such as a pressure cleaner.
  • the cleaning means 140 may comprise one or more friction surfaces, such as a scrub or stationary brush, suitable for cleaning a net by being moved across the net 130.
  • the first subsea unit 110 is according to the present disclosure provided with a line camera 230.
  • the line camera 230 may be considered as arranged on the side of the first subsea unit 110 that faces the net 130 under operation of the subsea assembly 100.
  • the line camera 230 may as a way of example span between two parallelly oriented belt assemblies 150 of the first subsea unit 110, and optionally be arranged perpendicularly to two parallelly oriented belt assemblies 150 of the first subsea unit 110.
  • a line camera 230 may generally be arranged perpendicularly to the driving direction of the subsea assembly 100, which may be beneficial in order to optimize how much of the net that is captured per pass of the subsea assembly 100.
  • a line camera 230 may be configured to span the full width of the first subsea unit 110. The latter may be obtained by placing the line camera in front of, or behind, the parallelly oriented belt assemblies 150 of the first subsea unit 110.
  • Figure 9a schematically illustrates a first subsea unit provided with a line camera 230, where the line camera is configured to span the full width of the first subsea unit 110.
  • the line camera may according to the disclosure be used to capture image data in the form of line images of the net as the subsea assembly adheres to and moves across the net.
  • the image data may be captured continuously, and the capture rate may for example be set according to a desired resolution and the speed in which the subsea assembly moves across the net.
  • the image data captured by the line camera may further be communicated to an onboard computer of the subsea assembly that is configured to generate a two- dimensional image of a portion of the submerged net based on the received image data.
  • the portion of the net imaged in the two-dimensional image may generally be any portion of the net, for example 0.5 square meter or the whole net.
  • Figure 8 shows an example of a two-dimensional image of a fish pen obtained using a line camera configured to capture images with a resolution of 300 DPI.
  • the two-dimensional image may generally contain information about the net, such as information on biofouling and information regarding the state of the net, i.e. signs of wear, holes, etc.
  • the two-dimensional image may for example be communicated to an operator or onshore computer, or alternatively be processed on bord the subsea assembly, for example by an onboard computer.
  • the two-dimensional image may be used in order to determine the strand thickness of at least one strand of the submerged net.
  • the two-dimensional image will have a resolution where each pixel may be converted to a spatial distance.
  • said conversion also known as a calibration, will be dependent on parameters such as the distance between the net and the line camera, the type of line camera used, the capture rate of the line camera and the speed in which the subsea assembly moves across the net.
  • Said calibration may for example be performed by capturing a reference image of a known object with a known size, e.g.
  • the two-dimensional image may then be analysed, either manually or digitally to obtain information regarding the strand thickness of one or more strands of the net. It will be appreciated by a person skilled in the art with knowledge of the present invention that once the two-dimensional image has been obtained according to this disclosure, the two-dimensional image may be digitally analysed using a wide range of existing analytic tools, e.g. commercially available software tools, in order to determine the strand thickness of one or more strands of the net. Said digital analysis may according to any embodiment of the invention be performed by an on-board computer of the subsea assembly.
  • At least parts of the above method may be executed for example by an on-board computer of the subsea device or a separate multi-purpose computer.
  • Said method may be summarized as comprising initially receiving by said computer, image data from a line camera of a subsea assembly as the subsea assembly adheres to and moves across the submerged net.
  • the computer may then, subsequently generate a two- dimensional image of a portion of the submerged net based on the received image data, before determining the strand thickness of the at least one strand of the submerged net based on the two-dimensional image.
  • Parts of the method described herein may generally be considered as a computer-implemented method, particularly the steps of the method that may be performed by a computer, e.g., an on-board computer of the subsea device.
  • determining the strand thickness of the at least one strand of the submerged net based on the two-dimensional image may vary and said process may be implemented in a variety of ways. However, there are certain process steps that may be implemented in the method in order to for example filter or modify the two-dimensional image in order to ease later analysis.
  • determining the strand thickness of the strand of the submerged net may comprise a step of converting the two- dimensional image into a first binary image.
  • An example of a first binary image is show in figure 10a. Converting the two-dimensional image into a first binary image has the benefit that that the net may be made to appear more distinctly outlined than in the two-dimensional image.
  • Each pixel of the first binary image may in the process of converting the two-dimensional image into a first binary image be made to represent a corresponding pixel in the two-dimensional image.
  • Each pixel of the first binary image may then be assigned a first binary value if the brightness of the corresponding pixel in the two-dimensional image is above/below a first predetermined threshold.
  • each pixel of the first binary image may assigned a second binary value if the brightness of the corresponding pixel in the two-dimensional image is below/above a first predetermined threshold.
  • Each pixel of the first binary image may in a first example be assigned a first binary value if the brightness of the corresponding pixel in the two-dimensional image is above a first predetermined threshold if the strands of the net appear bright in the two-dimensional image. The latter may occur if the images taken by the line camera are taken using a front light, i.e. using a light source in front of the net relative to the line camera.
  • each pixel of the first binary image may assigned a second binary value if the brightness of the corresponding pixel in the two-dimensional image is below a first predetermined threshold.
  • Each pixel of the first binary image may in a second example be assigned a first binary value if the brightness of the corresponding pixel in the two-dimensional image is below a first predetermined threshold if the strands of the net appear as dark in the two-dimensional image. The latter may occur if the images taken by the line camera are taken using a backlight, i.e. using a light source behind the net relative to the line camera.
  • each pixel of the first binary image may assigned a second binary value if the brightness of the corresponding pixel in the two-dimensional image is above a first predetermined threshold.
  • the first predetermined threshold may be chosen for example based on the contrast level in the two-dimensional image.
  • the latter may be beneficial as the knots do not represent a true thickness of any strand of the submerged net.
  • Said filtering of knots may be performed by initially converting the first binary image into a distance map image as shown in figure 10b.
  • Each pixel of the distance map image may be made to represent a corresponding pixel in the first binary image, and each pixel of the distance map image may be assigned a value that denotes the distance between the corresponding pixel in the first binary image and the most proximate pixel to that corresponding pixel in the first binary image having the second binary value. Any pixel in the distance map image corresponding to a pixel in the first binary image having the second binary value, may be assigned a zero value in the distance map image.
  • the resulting distance map image will consequently be a map that illustrates the density of the net in the two-dimensional image, where the knots will appear with a high value relative to a single strand.
  • the knots may consequently be filtered out of the distance map image by assigning a zero value to each pixel of the distance map image having a value above a second predetermined threshold value.
  • Said second predetermined threshold value may for example be chosen based on a known size of said knots, which for example may be manually measured.
  • the distance map image may subsequently be converted into a second binary image, where each pixel of the second binary image represents a corresponding pixel in the distance map image.
  • Each pixel of the second binary image may then be assigned the first binary value if the brightness of the corresponding pixel in the distance map image is non-zero and be assigned the second binary value if the brightness of the corresponding pixel in the distance map image is zero.
  • the resulting second binary image may thus take the form as shown in figure 10c, i.e. be a black and white image showing only free-standing strands of the submerged net.
  • the second binary image may then be used to determine the strand thickness of the at least one strand of the submerged net based on the second binary image. It will be appreciated that the above process may be used to filter out visible intact knots in the first binary image. A hole in the net, for example due to a loosened or missing knot, will appear in the two- dimensional image, the first binary image, the distance map image and the second binary image.
  • the strand thickness of the at least one strand of the submerged net may be found based on the second binary image in a variety of ways.
  • the strand thickness of the at least one strand of the submerged net may be found by initially defining a virtual rectangle around each of the free-standing strands of the submerged net, where the sides of each rectangle are adjoining the outer contour of one of the free-standing strands.
  • lines may then be drawn that cross each free-standing strand.
  • Each of the said lines may then be used to find the thickness of each free-standing strand, for example by counting the number of pixels of each line that overlap a pixel having the first binary value.
  • Figure lOd shows an image where the resulting strand thicknesses of some strands of the net are shown.
  • the above method may according to the present disclosure further comprise a step of generating a data file containing information on the thickness of the at least one strand of the submerged net and the position of the at least one strand in the two-dimensional image.
  • Performing such a step at an onboard computer of the subsea assembly has an advantage as said data file will be smaller in size, i.e. kB, MB, GB, ..., than the two dimensional image, hence reducing the need for bandwidth between the subsea assembly and any onshore server, controller or similar, with which the subsea assembly may communicate.
  • the presence of an onboard computer of the subsea assembly generally has the advantage that the subsea assembly may in itself perform pre-processing of the two-dimensional image and send the results of this pre-processing to any onshore server, controller or similar rather than to send the full two-dimensional image.
  • the requirements for bandwidth between the subsea assembly and server, controller or similar is then reduced.
  • the first subsea unit 110 may as schematically illustrated in figure 2 be provided with a line camera 230, while the second subsea 120 unit may, as schematically illustrated in figure la be provided with a background element 240.
  • the line camera 230 and the background element 240 may be arranged such that they face each other when the subsea assembly 100 adhere to the net 130.
  • the line camera 230 and background element 240 may thus respectively be considered as arranged on the side of the first subsea unit 110 and second subsea unit 120 that face the net 130 under operation of the subsea assembly 100.
  • the line camera 230 and background element 240 may as a way of example be positioned between two parallelly oriented belt assemblies 150 of the first subsea unit 110 and second subsea unit 120 respectively.
  • the line camera 230 may more specifically be positioned between two parallelly oriented belt assemblies 150 of the first subsea unit 110, while the background element 240 may cover at least a part of the area between the two parallelly oriented belt assemblies 150 of the second subsea unit 120.
  • the first subsea unit 110 may be provided with a line camera 230 and a background element 240
  • the second subsea 120 unit may be provided with a line camera 230 and a background element 240.
  • a background element may generally in the context of the present invention be considered as an element shaped to provide a fixed homogeneous background for the line camera when the latter captures an image.
  • the background element may be shaped according to the type of camera used such that an image of the background element results in an image with no or at least limited contrast.
  • the use of a background element in the second subsea unit has been found to be beneficial as the background element provides a fixed background for the line camera of the first subsea unit.
  • the net to be imaged by the line camera will during operation of the subsea assembly be present between the line camera and the background element, thus enabling the line camera to image the net using the background element as a fixed background.
  • Multiple images of the net may thus be compared without having to consider various lighting conditions that for example may occur if one where to image a net using the open sea as a background.
  • the open sea will for example give a lighting effect in a captured image dependent on the depth of the subsea assembly during the capture of the image.
  • the fixed background provided by the background element has further been found to enable high resolution images to be captured by the line camera.
  • the latter is useful for detecting holes in the net, wear of the net, and particularly early signs of wear of the net. Early signs of wear allow for example maintenance to be conducted prior to a hole developing in the net, thereby hindering for example the fish escaping the fish pen.
  • Figure 8 shows an example of an image of a fish pen obtained using a line camera configured to capture images with a resolution of 300 DPI and using a plane surface as a background element.
  • the background element 240 may as schematically illustrated in figure la comprise a plane surface, which may as a way of example be oriented in parallel with the ground pad 165 of the tracks 160 of the belt assemblies 150 of the second subsea unit 120.
  • a plane background element 240 may generally be arranged such that it is parallel with the net 130 during operation of the subsea assembly. It will be appreciated by a person skilled in the art with knowledge of the present disclosure that the background element 240 in this embodiment doesn't have to be perfectly in parallel with the net 130 during operation of the subsea assembly 100.
  • a plane background element 240 may generally be arranged such that it is within 10 degrees or 5 degrees of being in parallel with the net 130 during operation of the subsea assembly.
  • a background element 240 comprising a plane surface may as a way of example be a plate, for example a metal plate, a plastic plate, polymer plate or a composite plate.
  • the first subsea unit 110 and/or the second subsea unit 120 may as schematically illustrated in figure 3 further comprises one or more light sources 250.
  • the presence of a light source 250 in at least one of the first subsea unit 110 and the second subsea unit 120 has/have been found to be beneficial in order to illuminate the net 130 to be imaged by the line camera 250.
  • a light source 250 may be present for example next to the line camera 230 on the first subsea unit 110 in order to illuminate the net 130 to be imaged.
  • a light source 250 may additionally or alternatively be provided on the second subsea unit 120, for example facing the line camera 230 of the first subsea unit 110 when the subsea assembly 100 adhere to the net 130.
  • the light source may in any embodiment of the present disclosure be a light source configured to radiate white light. Other colours may alternatively be used, for example in order to enhance contrast between the net to be imaged and any biofouling, or other substances of interest that may be present on the net.
  • the light source may in any embodiment of the present disclosure comprise at least one LED.
  • the light source 250 may as schematically illustrated in figure 4 be integrated in the background element 240. Integration in the background element 240 enables for example bright field images to be captured by the line camera 230, allowing for a high contrast of the net.
  • the background element 240 may as a way of example comprise an array of light sources 250 such as LEDs 270.
  • the background element 240 may in a particular embodiment be configured to generate Kohler illumination, i.e. even illumination, ensuring that the light source 250 does not appear in images captured by the line camera 230. Kohler illumination may for example be achieved at least in part by providing a diffuse transmitter in front of an array of light sources 250 such as LEDs 270.
  • FIG. 5b schematically illustrates an embodiment of the present disclosure where the light source 250 has an elongated shape, or where the light source 250 comprises a plurality of LEDs 270 arranged in a line. Either configuration may optionally be arranged perpendicularly to the driving direction of the subsea assembly 100.
  • the elongate shape may in other words be elongate in the direction perpendicularly to the driving direction of the subsea assembly 100, or the line of LEDs may be arranged in the direction perpendicularly to the driving direction of the subsea assembly 100.
  • An elongate light source 250 and/or a light source 250 comprising a plurality of LEDs 270 arranged in a line has been found to be beneficial in order to save power in the subsea assembly 100.
  • Such a light source 250 may be used to selectively illuminate a section of the net 130, hence allowing for sampling of a linear segment of the net 130 per time.
  • An elongate light source 250 and/or a light source 250 comprising a plurality of LEDs 270 arranged in a line may for example be combined with the use of a line camera 230 where the elongate light source 250 and/or the light source 250 comprising a plurality of LEDs 270 arranged in a line may be aligned with the line camera 230, e.g. such that any part of the elongate light source 250 and/or the light source 250 comprising a plurality of LEDs 270 arranged in a line is arranged facing into the line camera 230 when the subsea assembly 100 is being operated.
  • an elongate light source 250 and/or a light source 250 comprising a plurality of LEDs 270 arranged in a line may in the latter case optimize power consumption, as a limited amount of light will be wasted for illuminating parts of the net 130 not being imaged by the line camera 230.
  • An elongate light source 250 and/or a light source 250 comprising a plurality of LEDs 270 arranged in a line may as schematically illustrated in figure 5 and 9 be integrated in the background element 240.
  • the light source may according to any embodiment of the present disclosure be configured to flash or alternatively be configured to pulsate.
  • a light source configured to flash or configured to pulsate may be used to reduce the power consumption of the subsea assembly, as the light source may be synchronized with the capture rate of the line camera.
  • a camera having a capture rate of 1 fps may thus only need illumination once per second, allowing the light source to be off or idle for the rest of the time.
  • the light source, or a control unit for the light source may for example be provided with necessary capacitors sufficiently sized in order to power the light source.
  • FIG. 6 schematically illustrates an embodiment of the present disclosure where the second subsea unit 120 further comprises a filter 280 arranged in front of the line camera 230.
  • a filter 280 may for example be used in order to filter out the colour of any biofouling on the net 130 in order to enhance contrast with the net 130.
  • a filter 280 may alternatively be used in order to filter out the colour of the surrounding water.
  • the filter 280 may be a band-stop filter or a band pass filter.
  • the line camera may comprise a spectrometer.
  • a spectrometer may here be used in order to obtain images of the net based on selected wavelengths of interest.
  • the effects of using a spectrometer may be considered similar to using a filter but has the additional advantage that more information may be obtained by any one image relative to what may be obtained using for example a normal image sensor like a charge- coupled device in combination with a filter.
  • the first subsea unit When used to clean the net of a fish pen, the first subsea unit may in a particular embodiment of the present disclosure be positioned on the side of the net facing into the fish pen, while the second subsea unit may be positioned on the side of the net facing out from the fish pen.
  • obstacles such as ropes and rope knots are typically positioned on the outer surface of the fish pen, it is beneficial to image the net of the fish pen from the inside of the fish pen.
  • the line camera may thus in this embodiment be positioned on the side of the net facing into the fish pen, thus allowing for a shorter and more permanent distance between the line camera and the net relative to what would have been possible if the line camera was provided on the subsea unit positioned on the side of the net facing out from the fish pen.
  • the subsea assembly may according to the present disclosure be dimensioned according to the net.
  • a typical extension of the subsea assembly is between 80 cm and 200 cm.
  • the extension of the subsea assembly is according to a specific embodiment of the present disclosure less than 150 cm.
  • Each road wheel 170,180,190 of the subsea assembly may, as schematically illustrated in figure 7, be provided with a suspension 200.
  • the suspension 200 for each road wheel 170,180,190 may be configured for shifting the position of said road wheel 170,180,190 in a direction at least in part perpendicular to a driving direction 220 of the subsea assembly.
  • An example of such a distance is less than 10 centimetres, or more specifically a distance of between 3 and 5 centimetres.
  • the suspension 200 of the road wheels 170,180,190 aims inter alia to enable the subsea assembly to traverse obstacles of the net, such as ropes, knots or similar.
  • any two adjoining tracks 160 may retain magnetic attraction even when the subsea assembly is traversing an obstacle.
  • a subsea assembly according to the present disclosure traversing a rope of the net.
  • the front road wheels 190 of each pair of adjoining tracks 160 will be displaced away from one another and the magnetic attraction between the part of the ground pad 165 between the front road wheel 190 and middle road wheel 180 of the pair of adjoining tracks 160 will be strongly reduced.
  • a subsea assembly having only two road wheels would in such an instance likely lose its magnet-induced grip on the net and consequently fall of the net.
  • the subsea assembly according to the present disclosure would on the contrary maintain its magnet induced grip on the net, as the part of the ground pad 165 between the middle road wheel 180 and read road wheel 170 would still be adjoining, such that sufficient magnetic attraction may be maintained.
  • the subsea assembly will upon continuing its traversing of said rope move relative to the rope such that the front road wheels 190 once again are brought in contact with each other, but where the middle road wheels 180 subsequently are displaced from their default position using their respective suspension 200.
  • the subsea assembly according to the present disclosure may maintain its adhesion to the net due to the magnet attraction between the ground pad 165 around the front road wheels 190 and the rear road wheels 170.
  • the subsea assembly will upon continuing its traversing of said rope, move relative to the rope such that the middle road wheels 180 once again are brought in contact with each other, but where the rear road wheels 170 subsequently are displaced from their default position using their respective suspension 200.
  • the latter situation is equivalent to the situation where the front road wheels 190 were displaced.
  • each belt assembly 150 further comprises a damper wheel 225.
  • Said damper wheel 225 may typically be positioned at a non-zero distance from the ground pad 165 of the belt assembly 150 to which it belongs. The latter location may here be in a direction perpendicular to the driving direction 220 of said belt assembly 150.
  • a damper wheel 225 may be utilized in order to compensate for any strain in a track 160 caused when the subsea assembly traverses an obstacle that causes one of its road wheels 170,180,190 to be displaced from their nondamped position.
  • a road wheel 170,180,190 being displaced as a consequence of the subsea assembly traversing an obstacle will result in the relevant track 160 having to conform to the shape of the object that is being traversed. Instead of the track 160 becoming strained due to the displacement of a road wheel
  • the damper wheel 225 may instead compensate for the shift in position of the road wheel 170,180,190, i.e. compensate for the resulting strain in the track 160 by being itself displaced.
  • Each damper wheel 225 may thus in other words be provided with a suspension 200 for shifting the position of said damper wheel 225 in order to compensate for a shift in position of a road wheel
  • a damper wheel 225 of that belt assembly may be displaced in the opposite direction of the displaced road wheel 170,180,190 in order to compensate for the increased length requirement on the track 160 due to the belt having to conform to the shape of the object that is being traversed.
  • a typical object that needs to be traversed may as previously mentioned be a rope or a knot, which for example could have a diameter or extension of 3-5 centimetres.
  • Each road wheel 170,180,190 may thus be provided with a suspension 200 for shifting the position of said road wheel 170,180,190 a distance of at least 3-5 centimetres in a direction at least in part perpendicular to a driving direction 220 of the subsea assembly.
  • Each damper wheel 225 may consequently be provided with a suspension 200 for shifting the position of said damper wheel 225 a distance of 3-5 centimetres.
  • any road wheel 170,180,190 may be provided with a suspension 200 for shifting the position of said road wheel 170,180,190 a distance of up to 10 centimetres in a direction at least in part perpendicular to a driving direction 220 of the subsea assembly.
  • a suspension 200 may generally be any suitable suspension 200. Examples of suitable suspensions 200 are spring-based suspension and hydraulic suspension.
  • the subsea assembly may according to any embodiment of the present disclosure be configured to traverse obstacles of a given size.
  • the subsea assembly may be configured to traverse an obstacle such as a rope or a rope knot.
  • the road wheels of each belt assembly may be spaced apart depending on the dimension of the obstacle to be traversed.
  • the road wheels of each individual belt assembly may be separated by a distance of at least 3-5 centimetres. The latter distance is here measured between the surface of two adjacent road wheels.
  • the road wheels of each individual belt assembly may generally be separated by a distance longer than 5 centimetres.
  • the upper limit for the spacing between two adjacent road wheels of the same belt assembly is determined by for example the obstacle that it is desirable to traverse, and/or for example the dimension and weight of the subsea assembly.
  • Any belt assembly 150 may, as illustrated in figure lb and 7, further comprise any number of drive wheels 320, damping wheels 225, road wheels, idlers and/or tightener wheels 340.
  • any belt assembly may be provided by a driving wheel 320, i.e. a wheel that supplies driving power to the track 160.
  • Any road wheel or damper wheel 225 may in any relevant embodiments of the present disclosure be a driving wheel 320.
  • a person skilled in the art would appreciate that the subsea assembly according to the present disclosure may comprise any number of additional wheels, e.g. dependent on the exact size and shape of the belt assemblies 150.
  • a tightener wheel 340 may for example be provided to form the previously described driving edge 245 or trailing edge 255.
  • each belt assembly 150 may further comprise an additional middle road wheel 180.
  • An additional middle road wheel 180 may contribute to increase the attraction between two adjoining belt assemblies 150 when the subsea assembly traverses an obstacle.
  • An additional middle road wheel 180 may contribute to ensuring a plane surface of the ground pad 165 of two adjoining tracks 160 being in contact during the traversing of said obstacle.
  • the size of each wheel of the subsea assembly will generally depend on the size of each subsea unit. The size of each wheel may typically be dimensioned according to the type of track used, for example such that the track may run across the wheels without experiencing too great a curvature.
  • each wheel of each belt assembly has a diameter in the range of 60 mm to 120 mm.
  • any wheel of a belt assembly that is positioned farthest to the front or back along the driving direction of a belt assembly will typically inflict the largest curvature on the track.
  • These farthermost wheels may thus have a diameter that is larger than that of any road wheels appurtenant to the same belt assembly, e.g. in the range from 10% - 250% larger, in particularly in the range from 50% - 100 % larger. Any one or both of the farthermost wheels may for example be a driving wheel 320.
  • the track of any belt assembly of the subsea assembly may according to any embodiment of the present disclosure be made at least in part from rubber, plastic or silicone.
  • a person skilled in the art will appreciate that the track may be made from other materials than those listed explicitly herein.
  • the track may for example be made from a combination of materials, e.g. a combination of those mentioned above.
  • the subsea assembly according to any embodiment of the present disclosure is not limited to cleaning a net.
  • the subsea assembly may according to any embodiment of the present disclosure alternatively be used in order to clean a seine, net cage, a water permeable sheet, water impermeable sheet or similar.
  • Other examples are watertight tarpaulin, perforated tarpaulin, or similar.

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Abstract

La présente invention concerne un procédé de détermination de l'épaisseur de brin d'au moins un brin d'un filet immergé, le procédé comprenant les étapes consistant à déplacer un ensemble sous-marin sur le filet submergé tandis que l'ensemble sous-marin adhère au filet, collecter des données d'image à partir d'une caméra barrette de l'ensemble sous-marin lorsque l'ensemble sous-marin adhère au filet immergé et se déplace sur celui-ci, générer, par un ordinateur embarqué de l'ensemble sous-marin, une image bidimensionnelle d'une partie du filet submergé sur la base des données d'image reçues, et déterminer, par l'ordinateur embarqué de l'ensemble sous-marin, l'épaisseur de brin dudit brin du filet submergé sur la base de l'image bidimensionnelle.
PCT/NO2022/050192 2021-08-11 2022-08-11 Procédé de détection de l'usure d'un filet WO2023018336A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
GB2401919.2A GB2624333A (en) 2021-08-11 2022-08-11 Method for detecting wear of a net
CA3228647A CA3228647A1 (fr) 2021-08-11 2022-08-11 Procede de detection de l'usure d'un filet
DKPA202430086A DK202430086A1 (en) 2021-08-11 2024-02-20 Method for detecting wear of a net

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
NO20210975 2021-08-11
NO20210975A NO347478B1 (en) 2021-08-11 2021-08-11 An analysing device and method for analysing a submerged net
NO20211001 2021-08-20
NO20211001A NO20211001A1 (en) 2021-08-11 2021-08-20 Method for detecting wear of a net

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015110791A1 (fr) * 2014-01-21 2015-07-30 Parkburn Precision Handling Systems Limited Système de surveillance
NO20161708A1 (en) * 2016-10-28 2018-04-30 Haukaas John Kristian Assembly for carrying out an operation on a net
EP3617124A1 (fr) * 2018-08-29 2020-03-04 Otis Elevator Company Dispositif de mesure de l'allongement d'un câble d'ascenseur
EP3617123A1 (fr) * 2018-08-29 2020-03-04 Otis Elevator Company Dispositif et procédé d'inspection d'un câble d'ascenseur

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015110791A1 (fr) * 2014-01-21 2015-07-30 Parkburn Precision Handling Systems Limited Système de surveillance
NO20161708A1 (en) * 2016-10-28 2018-04-30 Haukaas John Kristian Assembly for carrying out an operation on a net
EP3617124A1 (fr) * 2018-08-29 2020-03-04 Otis Elevator Company Dispositif de mesure de l'allongement d'un câble d'ascenseur
EP3617123A1 (fr) * 2018-08-29 2020-03-04 Otis Elevator Company Dispositif et procédé d'inspection d'un câble d'ascenseur

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Title
PASPALAKIS ET AL.: "Automated fish cage net inspection using image processing techniques", IET IMAGE PROCESSING, vol. 14, no. 10, 6 July 2020 (2020-07-06), pages 2028 - 2034, XP006093000, DOI: 10.1049/iet-ipr.2019.1667 *

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