EP4175468A1

EP4175468A1 - Autonomous vessel, system and method for performing an operation in an aquatic organism containing structure

Info

Publication number: EP4175468A1
Application number: EP21735692.2A
Authority: EP
Inventors: Mikkel PEDERSEN; Rune Andre Hansen
Original assignee: Probotic AS
Current assignee: Probotic AS
Priority date: 2020-07-03
Filing date: 2021-06-24
Publication date: 2023-05-10
Also published as: NO20200782A1; NO346573B1; WO2022002746A1

Abstract

The present invention relates to a system (10) for performing an operation in an aquatic organism containing structure (3) of an aquatic organism breeding farm (1), wherein the system (10) comprises an autonomous vessel (50) and a vessel station (20). The vessel (50) comprises a body (51) and a propulsion system (60) for moving the vessel (50) relative to, and in physical contact with, the structure (3). The vessel (50) further comprises a navigation system (70) for controlling the propulsion system (60). The navigation system (70) comprises an orientation sensor (71) for measuring a parameter representative of the current orientation of the vessel (50), a depth sensor (72) for measuring a parameter representative of the current depth (D) of the vessel (50) and a route planner (75), wherein a central processing unit (73) is configured to control the propulsion system (60) based on information from the orientation sensor (71), the depth sensor (72) and the route planner (75).

Description

AUTONOMOUS VESSEL, SYSTEM AND METHOD FOR PERFORMING AN OPERATION IN AN AQUATIC ORGANISM CONTAINING STRUCTURE

FIELD OF THE INVENTION

The present invention relates to an autonomous vessel for performing an operation in an aquatic organism containing structure of an aquatic organism breeding farm. The present invention also relates to a system for performing an operation in an aquatic organism containing structure of an aquatic organism breeding farm. The present invention relates to a method for performing an operation in an aquatic organism containing structure of an aquatic organism breeding farm.

BACKGROUND OF THE INVENTION

Fish and other aquatic organisms may be farmed in so-called fish farms. A fish farm typically comprises a floating element (typically one or more air-filled plastic rings) and a net suspended below the floating element. Several such floating elements and nets are typically assembled into one structure. Sea currents are causing fresh water to be supplied to the fish via openings in the net.

Over time, marine fouling will reduce the waterflow through the net. Marine fouling will also increase the weight on the net, which may damage the net. Some types of marine fouling (algae) may impact the fish health negatively. Consequently, the net must be cleaned periodically to remove marine fouling. In prior art, there are many examples of cleaning systems for cleaning nets of fish farms.

Land-based fish-farms comprises tanks filled with water, in which fish or other aquatic organisms are bred. Fresh water is here supplied to the tank, or the water are circulated via a cleaning system. Such cleaning systems are referred to as recirculating aquaculture systems (RAS). Also here, marine fouling will form on the inside of the tank.

Some cleaning systems focus on cleaning efficiency, where a ROV (remotely operated vehicle) with powerful jet nozzles and powerful rotating disks with jet nozzles are used to clean the net efficiently over a relatively short period of time. With this type of cleaning system, the net must be cleaned every third or fourth week. Even though effective, such powerful jet nozzles and powerful rotating brushes will increase the risk of damaging the net, which again may cause evacuation of fish from the net.

NO 343736 describes a cleaning system where a vessel is cleaning the net gently, but frequently. The cleaning system is installed on the fish farm, and is cleaning the net typically 1 - 2 times per 24 hours. Some of the cleaning systems have cleaning vessels that are remotely controlled by means of a handheld mobile console or from a control station. The ROV here comprises different types of sensors for helping the operator of the ROV. In WO2019134055 it is described a camera equipped with compass, depth and temperature sensors. Other cleaning vessels are autonomous. In NO 20161949 one such autonomous vessel is described as a free-swimming, autonomous cleaning and inspection robot, which are using a hydro-acoustic positioning system, a compass, a gyro, a depth sensor, a temperature sensor, oxygen sensor, turbidity sensor, cameras with machine vision etc.

One object of the present invention is to provide a vessel with a simple and robust navigation system for an autonomous cleaning vessel for cleaning the net of a fish farm and/or an autonomous inspection vessel for inspection of the net of a fish farm. In particular, the object of the present invention is to avoid using a hydro acoustic positioning system, as such a system is expensive and prone to faults.

Another object of the invention is to provide an alternative vessel for cleaning the net gently, but frequently.

SUMMARY OF THE INVENTION

The present invention relates to an autonomous vessel for performing an operation in an aquatic organism containing structure of an aquatic organism breeding farm, where the autonomous vessel comprises:

- a body;

- a propulsion system for moving the vessel relative to, and in physical contact with, the structure;

- a navigation system for controlling the propulsion system; wherein the navigation system comprises:

- a orientation sensor for measuring a parameter representative of the current orientation of the vessel;

- a depth sensor for measuring a parameter representative of the current depth of the vessel;

- a route planner;

- a central processing unit configured to control the propulsion system based on information from the orientation sensor, the depth sensor and the route planner.

Such autonomous vessels are often referred to as an AUV, an autonomous underwater vehicle.

In one aspect, the central processing unit configured to control the propulsion system based on information from the orientation sensor, the depth sensor and the route planner only. In one aspect, the autonomous vessel comprises a communication system, wherein the communication system is configured to send status information from the navigation system.

In one aspect, the route planner comprises a parameter representative of a maximum depth.

In one aspect, the route planner comprises a predefined route for the vessel along the structure.

In one aspect, the route planner comprises a speed reference parameter. In one aspect, the route planner comprises a scheduler.

In one aspect, the autonomous vessel has positive or neutral buoyancy.

In one aspect, the central processing unit is configured to control the propulsion system to keep the vessel in physical contact with the structure.

In one aspect, the route planner comprises a predefined route for keeping the vessel in physical contact with the structure.

In one aspect, the orientation sensor comprises a magnetic compass.

In one aspect, the orientation sensor comprises a gyroscope.

In one aspect, the orientation sensor comprises a gyrocompass.

In one aspect, the orientation sensor may comprise one or more of the above sensor types.

In one aspect, the orientation sensor is measuring a parameter representative of the current horizontal orientation of the body.

In one aspect, the orientation sensor is tilt-compensated.

In one aspect, a horizontal vessel position is represented as an angle between a vessel orientation and a reference orientation in the navigation system.

Alternatively, the horizontal vessel position may be expressed with other parameters, for example as a position in the horizontal plane, as polar coordinates, etc.

In one aspect, the entire vessel is located on the inside of the structure.

In one aspect, the navigation system is configured to check physical contact between the vessel and the structure by:

- sending a control signal to the propulsion system for moving the vessel towards an assumed location of the structure; - confirming physical contact if the movement of the vessel is less than a threshold value based on the control signal;

- not confirming physical contact if the movement of the vessel is above the threshold value based on the control signal.

In one aspect, the movement of the vessel towards the assumed location of the structure is measured by the orientation sensor.

In one aspect, the control signal sent to the propulsion system is a signal for pivoting the vessel towards the assumed location of the structure. This may be the case when the structure comprises a planar surface. It may also be used when the structure comprises a curved surface.

In one aspect, the control signal sent to the propulsion system is a signal for moving the vessel towards an assumed location of the structure and relative to, and in physical contact with, the structure. Hence, the vessel is moved towards the assumed location of the structure during the movement of the vessel relative to, and in physical contact with, the structure.

When the structure is a curved surface, the vessel will be pivoted by the contact with the surface. Hence, the orientation sensor will measure a continuous change in the orientation of the vessel as long as the vessel is moving relative to, and in contact with, the curved surface of the structure. By sending a control signal to the propulsion system for moving the vessel along the structure, it is also sending a control signal to the propulsion system for moving the vessel along the assumed location of the structure.

In one aspect, the central processing unit is configured to determine a position for the vessel based on the current orientation, the current depth and the confirmed physical contact between the vessel and the structure.

In one aspect, the navigation system comprises a rotation sensor rotated by the movement of the vessel as it is moving along the structure, wherein the rotation sensor is measuring a parameter representative of a travel distance.

In one aspect, the autonomous vessel is an autonomous cleaning vessel comprising:

- a cleaning system provided at least partially outside of the body.

In one aspect, central processing unit is configured to control the propulsion system to keep at least parts of the cleaning system in physical contact with the structure during movement of the vessel along the structure. In one aspect, the autonomous vessel is an autonomous inspection vessel comprising:

- an inspection system comprising a camera secured to the body.

In one aspect, the inspection system is connected to the navigation system, wherein the navigation system is configured to check physical contact between the vessel and the structure by:

- analysing images captured by the camera.

In one aspect, a mesh size of the structure is analysed.

In one aspect, the maximum depth is a maximum cleaning depth. In one aspect, the maximum depth is a maximum inspection depth.

In one aspect, the movement is measured by the navigation system.

In one aspect, the navigation system comprises a timer for measuring time. The timer may be integrated as part of the central processing unit. The route planner may comprise an estimated time of arrival for different points along the route.

In one aspect, the central processing unit configured to control the propulsion system based on information from the orientation sensor, the depth sensor, the route planner and the timer only.

The present invention also relates to a system performing an operation in an aquatic organism containing structure of an aquatic organism breeding farm, wherein the system comprises:

- an autonomous vessel according to the above;

- a vessel station provided at sea level.

In one aspect, the autonomous vessel comprises a rechargeable battery system for powering the navigation system and the propulsion system, wherein the rechargeable battery system is charged at the vessel station.

In one aspect, the rechargeable battery system is powering the communication system.

The present invention relates to a method for performing an operation in an aquatic organism containing structure of an aquatic organism breeding farm, wherein the method comprises the steps of: a) providing a vessel comprising a body; b) moving the vessel relative to, and in physical contact with, the structure; wherein the method further comprises the steps of: c) measuring a parameter representative of the current orientation of the vessel; d) measuring a parameter representative of the current depth of the vessel; e) providing a route plan for the vessel; f) controlling the movement of the vessel by means of the route plan, the parameter representative of the current orientation of the vessel and the parameter representative of the current depth of the vessel.

In one aspect, the method step f) comprises:

- controlling the movement of the vessel only by means of the route plan, the parameter representative of the current orientation of the vessel and the parameter representative of the current depth of the vessel.

In one aspect, the method further comprises controlling the movement of the vessel to a maximum depth.

In one aspect, the method step e) comprises the step of:

- determining a predetermined route for the vessel along the structure (3).

In one aspect, the method step f) comprises the step of:

- controlling the movement of the vessel to keep the vessel in physical contact with the structure.

In one aspect, the method comprises the step of:

- representing a horizontal vessel position as an angle between the vessel orientation and a reference orientation.

In one aspect, the method comprises the step of:

- sending a control signal to move the vessel towards an assumed location of the structure;

- confirming physical contact if the movement of the vessel is less than a threshold value based on the control signal;

In one aspect, the method comprises the step of controlling the movement of the vessel by moving the vessel towards an assumed location of the structure and to move the vessel relative to, and in physical contact with, the structure.

The term “aquatic organism containing structure” is used herein for a container which can contain aquatic organisms. The structure may be a net allowing water to flow through or it may comprise a wall, for example the wall of a tank.

In one aspect, the “aquatic organism containing structure” is a closed structure filled with, or partially submerged in, a water body. The structure is considered to be a “closed” structure as its sides and bottom will prevent aquatic organisms to escape from the structure. It should be noted that even if the structure is considered to be a closed structure, the top of the structure may be open. When the structure projects up a distance from the surface of the water body, it is considered sufficient to prevent aquatic organisms from escaping via the surface of the water inside the structure to the outside of the structure. The “aquatic organism containing structure” may also be entirely submerged in a water body. In such a case, the closed structure will also have a top to prevent aquatic organisms from escaping up from the structure.

In one aspect, the structure “aquatic organism containing structure” is a cylindrical or conical structure, or a combination thereof. In one aspect, the “aquatic organism containing structure” is a pyramidical, a triangular prism, a rectangular prism or a polygonal prism. In one aspect, at least one surface of the structure is curved. In one aspect, at least one surface of the structure is planar. In one aspect, the vessel is operating on the inside of the structure. A curved surface of the structure is here a concave surface when observed from the vessel.

The term “cleaning” is used herein as a term for removing marine fouling.

The term “inspection” is used herein as a term for capturing images or a series of images of the structure for manual or automatic evaluation of the status of the structure, for example whether the structure is damaged or not.

The term “route” is used herein to describe a continuous path or pattern a vessel is intended to move along. A “route” can also be represented as a number of intermediate points (often referred to as “way points”) a vessel is indented to move between in a desired sequence. The route as defined by the continuous path, pattern or intermediate points is herein defined relative to a point, typically the vessel station or another point of the fish farm.

The term “navigate” (and the noun “navigation”) is used herein as a method for moving a vessel along a route in a space below sea level. To navigate along this route, parameters representative of a current location is used to calculate how the propulsion system should be operated to follow the route. It should be noted that the current location does not need to be known at all times. It should further be noted that the position can be expressed as a relative position, for example relative to the structure.

According to the above, it is achieved an autonomous vessel with a simple and robust navigation system. No hydro-acoustic positioning system are needed.

According to the above, it is achieved an autonomous vessel which is gentle with respect to fish. When the autonomous vessel is an autonomous cleaning vessel comprising a cleaning system provided at least partially outside of the body, brushes are used, but no powerful jet nozzles are used. DETAILED DESCRIPTION

Embodiments of the invention will now be described in detail with reference to the enclosed drawings, where: Fig. 1 illustrates a fish farm with a vessel station and autonomous vessel;

Fig. 2 illustrates a first embodiment of the vessel, a cleaning vessel, schematically from a first side;

Fig. 3 illustrates the cleaning vessel schematically from a second side;

Fig. 4 is a block diagram of the cleaning vessel; Fig. 5 illustrates orientation parameters of the navigation system;

Fig. 6 illustrates alternative orientation parameters;

Fig. 7 illustrates a land-based fish farm with an autonomous cleaning vessel.

Fig. 8 illustrates an alternative embodiment of the block diagram shown in fig. 4; Fig. 9a illustrates a fish farm with the vessel station and autonomous vessel, wherein the fish farm has a rectangular floating element;

Fig. 9b illustrates different positions for the vessel in the deeper parts of a fish farm;

Fig. 10 illustrates a second embodiment of the vessel, an inspection vessel, schematically from a first side; Fig. 11 illustrates the inspection vessel schematically from a second side;

Fig. 12 is a block diagram of the inspection vessel;

Fig. 13 illustrates a third embodiment, a cleaning and inspection vessel, schematically from a first side;

Fig. 14 illustrates the cleaning and inspection vessel schematically from a second side.

It is now referred to fig. 1, where a seabased farm 1 is shown schematically, comprising a floating element 2a floating at sea level SL and where a net 3a is suspended in the seawater below the floating element 2.

In the present embodiment, the seabased farm 1 is used to breed salmon. However, the present invention may also be used for farms breeding other aquatic organisms.

The floating element 2a typically circular, and the net 3a suspended below the floating element 2a is typically cylindrical and/or conical, as shown in fig. 1. However, both the floating element 2a and net 3a are somewhat flexible and will to some extent change shape under influence of waves, sea currents etc. It is now referred to fig. 7. where a landbased farm 1 is shown to comprise a cylindrical tank 2b. Smolt, fish or other aquatic organisms may be bred inside the tank.

Both the net 3a and the inner surface 3b will be exposed to marine fouling, and must be cleaned. The net 3 a and the inner surface 3b will hereinafter be commonly referred to as a structure 3.

In the description below, two embodiments of a system for performing an operation in the structure 3 will be described, a first embodiment in the form of a system for cleaning of the structure 3 and a second embodiment in the form of a system for inspecting the structure 3. The systems can be combined, forming a system for cleaning and inspecting the structure 3.

System for cleaning the structure 3

In fig. 1 and fig. 7, a system 10 for cleaning of the structure 3 is shown. The system 10 comprises an autonomous cleaning vessel 50 (indicated by a solid-line rectangle) and a vessel station 20 (indicated as a dashed-line rectangle) provided at sea level SL.

It is now referred to fig. 2 and fig. 3, where the vessel 50 is shown schematically.

The vessel 50 comprises a body 51, which typically will be a housing or “hull” protecting elements within the body 51 from the water outside the body 51. Fig. 3 shows the net-facing side SFS of the body 51, i.e. the side of the body 51 being faced towards the structure 3. Fig. 2 shows the opposite side of the net-facing side 3.

Visible on the outside of the body 51, the vessel 50 comprises one or more thrusters 61, which are part of a propulsion system 60. It should be noted that the thrusters 61 are here drawn very schematically as two circles each having a rotor. The location of the thrusters, the direction of the thrusters and the relative size of the thrusters are drawn schematically for illustrative purposes, and are not representative of how the propulsion system 60 may be designed to move the vessel 50 as desired.

Also visible on the outside of the body 51 is one or more brushes 81, which are part of a cleaning system 80. As shown, the brushes 81 are provided on the net-facing side of the body 51.

On the upper part of the body 51, the vessel 50 comprises a connection interface 52 for connection to a connection interface (not shown) of the vessel station 20. The connection interface 52 may be a mechanical connection interface, an electrical power connection interface and/or a communication interface. Not visible on the outside of the body 51 (i.e. provided on the inside of the body 51), the vessel 50 comprises a navigation system 70, a communication system 90 and a rechargeable battery system 95. These systems 70, 90, 95 are indicated as dashed boxes in fig. 2.

Preferably, the rechargeable battery system 95 is used as ballast for the vessel 50 and is therefore located in the lower part of the vessel 50. The vessel 50 may further comprise a buoyancy system 53, such as a gas filled container, or buoyant foam, subsea foam ( etc. However, such a gas-filled container is not essential, as an air- filled space within the body 51 itself may function as such a buoyancy system 53. Consequently, it is achieved that the vessel 50 is standing up-right in the orientation shown in fig. 2 and 3 by itself when submerged in water.

In one aspect, the autonomous cleaning vessel 50 has positive buoyancy. Hence, should there be a failure causing a stop of the propulsion system, the vessel 50 itself will float to the surface level.

It should be noted that the cleaning vessel 50 of the present invention have the same purpose as described in prior art NO 343736 where the structure 3 is cleaned gently, but frequently. Preferably, the brushes 81 of the cleaning system 80 are passive brushes, i.e. they are stationary relative to the vessel body 51. In an alternative embodiment, it is possible to provide the cleaning system 80 with active brushes, for example rotatable brushes. In such a case, the cleaning system 80 may be powered by the rechargeable battery unit 95, as shown in fig. 8. However, the cleaning system does not comprise jet nozzles, as such nozzles are not considered to be gentle.

It is well known how marine fouling is developed over time. Initially, a structure submerged in water will be covered with a conditioning film of organic polymers in relatively short time. After a while (ca 24 hours), this conditioning film allows the process of bacterial adhesion to occur, initiating the formation of a biofilm. After ca a week, the rich nutrients and ease of attachment into the biofilm allow secondary colonizers to attach themselves. Within two - three weeks, tertiary colonizers have attached. The main purpose of the gently, frequent cleaning is to remove the biofilm before secondary colonizers are allowed to attach to the structure. Hence, the present cleaning process also has the purpose of preventing severe marine fouling to develop.

According to the above, the brushes 81 must be in contact with the structure 3 for the purpose of removing early stage marine fouling from the structure and hence to prevent development of later stages of marine fouling to form on the structure 3. Hence, the propulsion system 60 is controlled to move the vessel 50 relative to, and in physical contact with, the structure 3. Hence, the brushes 81 will be moved along the structure 3. When this is performed frequently, marine fouling will not be able to grow, since the biofilm gets brushed so often that the next stages of fouling do not occur. By frequent cleaning the net is kept clean and less power is needed to remove marine fouling at early stages in development.

It is now referred to fig. 4. Here, solid lines show power flow and dashed lines show signal flow schematically.

As is shown, the rechargeable battery unit 95 supplies power to the navigation system 70, the propulsion system 60 and the communication system 90. The rechargeable battery unit 95 is also connected to the connection interface 52 to enable recharging of the unit 95 when connected to the vessel station 20.

In fig. 4, it is also shown that the navigation system 70 is sending a control signal to the propulsion system 60. The navigation system 70 comprises two sensors, an orientation sensor 71 and a depth sensor 72.

The orientation sensor 71 may comprise a magnetic compass which are sensing the orientation of the magnetic field of the earth. Alternatively, the orientation sensor 71 may comprise a gyrocompass which are sensing the rotation of the earth. Yet an alternative is to use a gyroscope which are sensing orientation relative to a reference point. Such a reference point may be the vessel station 20.

The orientation sensor 71 is configured to measure a parameter representative of the current horizontal orientation of the vessel 50. In the prototype of the present invention, the sensor LSM9DS1 from STMicroelectronics is used as orientation sensor.

The depth sensor 72 comprises a sensor for measuring a parameter representative of the depth D below sea level SL. The depth sensor 72 may for example be a pressure sensor. In the prototype of the present invention, the Bar30 sensor from BlueRobotics is used as depth sensor.

The orientation sensor 71 and the depth sensor 72 may together be referred to as a position determination system, as the relative position of the vessel can be determined from these sensors 71, 72 alone, under the assumption that the vessel is in physical contact with the structure 3 during its movement. This will be described further in detail below.

The navigation system 70 further comprises a route planner 75. The route planner comprises information about the route the vessel 50 is to move along the structure 3, in order to ensure that all desired areas of the structure 3 becomes cleaned. The route planner also comprises a schedule for how often the vessel 50 is to be used.

In the present embodiment, the vessel 50 is initially moving from the vessel station 20 and then moves a 360° lap (i.e. one entire lap around the net) back to the initial position. Then, the vessel 50 moves one level deeper, and then a further 360° lap is performed. This continues until the entire area of the structure has been covered. Then, the vessel 50 moves back to the vessel station 20 for recharging of its battery unit 95.

The navigation system 70 further comprises a central processing unit 73 configured to control the propulsion system 60 based on information from the orientation sensor 71, the depth sensor 72 and the route planner 75.

Some parameters may also be stored in either the route planner or in the central processing unit. These parameters may be:

1) structure-specific parameters, for example as diameter or circumference of structure, shape of structure, maximum cleaning depth CDmax, other geometry parameters such as transitions between a cylindrical part of the structure and a conical part of the structure etc

2) vessel-specific parameters, for example size, cleaning depth CD (fig. 3) for the brushes 81 indicating the height the vessel may clean during horizontal movement, which may be used to determine how much deeper the vessel should be moved after each 360° lap, etc

3) system specific parameters, for example position of the vessel station 20.

It should be noted that the technical function of the route planner 75 may be integrated as a part of the central processing unit 73 (as indicated in fig. 8). It should further be noted that the route planner 75 does not need to specify the exact route for the vessel. As an example, only a cleaning depth CD indicated in fig. 1 together with the time for starting each cleaning operation may be specified in the route planner. Based on this, the central processing unit 73 may contain software and/or hardware to control the propulsion system 60 to move one round until the orientation is the same as the initial orientation, and then move the vessel down, etc.

Preferably, the central processing unit 73 may control the propulsion system 60 based on information from the orientation sensor 71, the depth sensor 72 and the route planner 75 only. Consequently, complex and expensive hydro-acoustic positioning systems can be avoided.

It is now referred to fig. 5. Here, three different horizontal positions for the vessel 50 is indicated as PI, P2 and P3.

The first position PI corresponds to the position of the vessel when the vessel is in the vessel station 20. This is used as a base reference for the orientation of the vessel 50. Here, a vessel orientation is indicated by a vector VO and a reference orientation is indicated by a vector N. When using a magnetic compass, the reference orientation may point to the magnetic north pole. When using a gyrocompass, the reference orientation may point to the axis of the rotation of earth. By definition, an angle al between the vessel orientation VO and the reference orientation N is set to 0°. Also when using the vessel station 20 as a sole reference point, an angle al is set to 0°.

When the vessel 50 is in the second position P2, it can be seen that the reference orientation N is still pointing in the same direction as in the first position. An angle a2 between the vessel orientation VO and the reference orientation N is now measured to be 45° by means of the orientation sensor 71.

When the vessel 50 is in the third position P2, it can be seen that the reference orientation N is still pointing in the same direction as in the first and second positions. An angle a3 between the vessel orientation VO and the reference orientation N is now measured to be 225° by means of the orientation sensor 71.

Hence, the horizontal position P for the vessel 50 may be expressed solely by means of the angle a in the range [0°, 360°), when assuming that the vessel 50 is in contact with the structure 3 during its movement. The vertical position is, as described above, represented by the depth D.

It is now referred to fig. 4 again. Here it is shown that the vessel 50 comprises a communication system 90. The communication system 90 is configured to send status information from the navigation system 70. In the prototype, the Waterlinked Modem M64 is used as communication system 90. The communication system 90 is preferably communicating wirelessly with the vessel station 20. Alternatively, status information is stored in the vessel 50 until the vessel 50 returns to the station 20, where status information is transferred wirelessly or via a wire to the station 20.

It should be noted that the navigation system 70 may be configured to check if there is physical contact between the vessel 50 and the structure 3. This may be needed if strong sea currents have pushed the vessel 50 away from the net, etc.

In such a situation, the navigation system 70 may send a control signal to the propulsion system 60 for moving the vessel 50 towards an assumed location of the structure 3. Physical contact is confirmed if the movement of the vessel 50 is less than a threshold value based on the control signal, i.e. that the vessel 50 is not allowed to move as far as expected based on the control signal. The threshold value will typically be set based on how far the vessel would move in water with no obstacles present. On the contrary, physical contact is not confirmed if the movement of the vessel 50 is above the threshold value based on the control signal.

There are many ways to obtain this function. If thrusters on one side is used only, movement can be measured as a change in orientation by means of the orientation sensor 71. In the same way, both thrusters may be used alternatingly, and again, movement can be measured by means of the orientation sensor 71. Change in movement may also be measured as acceleration/retardation. The sensor LSM9DS1 used as orientation sensor 71 comprises acceleration sensors which may be used for this purpose.

The control signal sent to the propulsion system 60 may also be a signal for moving the vessel 50 towards an assumed location of the structure 3 and at the same time relative to, and in physical contact with, the structure 3. Hence, the vessel is moved towards the assumed location of the structure during the movement of the vessel relative to, and in physical contact with, the structure 3.

When the structure 3 is a curved surface, the vessel 50 will be pivoted by the contact with the surface 3. Hence, the orientation sensor 71 will measure a continuous change in the orientation of the vessel as long as the vessel is moving relative to, and in contact with, the curved surface of the structure 3. By sending a control signal to the propulsion system 60 for moving the vessel 50 in a tangential direction along the structure, it is also sending a control signal to the propulsion system for moving the vessel along the assumed location of the structure 3.

The navigation system 70 may further comprise a timer. This timer will typically be a part of the central processing unit 73.

It is now referred to fig. 9a. Here it is shown a fish farm with a rectangular or square floating element 3 having four sides 4a, 4b, 4c and 4d. The net (not shown in fig. 9a) is suspended vertically below the floating element and hence has a rectangular prism shape.

The system 10 can be used to clean also this type of net. The station 20 and the different positions for the vessel are shown in fig. 9a.

The first position PI corresponds to the position of the vessel when the vessel is in the vessel station 20, similar to the first position PI of fig. 5. The vessel station is here provided centrally on the first side 4a. Also here, this is used as a base reference for the orientation of the vessel 50, where the vessel orientation is indicated by a vector VO and a reference orientation is indicated by a vector N and where the angle al is set to 0°.

The vessel 50 is now moved along side 4a towards side 4b, i.e. downwardly in fig. 9a. Here, the orientation does not change until the vessel 50 meets the second side 4b. It should be noted that during this movement, the exact position of the vessel may not be known, as the orientation does not change. It should be noted that this may be acceptable for the purpose of cleaning the net - the central processing unit 73 will also here be considered to control the propulsion system 60 based on information from the orientation sensor 71, the depth sensor 72 and the route planner. The corners between the sides may be used as reference locations or so-called way points, where the vessel is considered to be on route as long as the vessel arrives to the corners in a predetermined sequence defined by the route planner.

As mentioned above, the vessel 50 may also check if there is physical contact between the vessel 50 and the structure 3 during its straight-lined movement along the sides 4a, 4b, 4c, 4d.

When arriving to the corner between sides 4a and 4b, the vessel will detect that the movement along side 4a is obstructed, and the central processing unit 73 may control the propulsion system 60 to rotate the vessel 90°, until the correct orientation is achieved by measuring the angle a2.

In the second position P2, the vessel 50 will be in contact with either one of the first side 4a or the second side 4b or the vessel 50 will be in contact with both sides 4a, 4b.

In the third position P3, the angle a2 is 90° and the vessel 50 continues its straight- line movement along the second side 4b towards the third side 4c.

It is now referred to fig. 9b. Here, three positions P10, P 11 , P12 are indicated, to illustrate that the orientation sensor 71 is both able to measure horizontal orientation (represented by the angle a between the horizontal vessel orientation V0 and the reference vector N as shown in fig. 5 and 9a) and vertical orientation represented by the angle b between the vertical vessel orientation and the reference vector N.

System for inspecting the structure 3

The system for inspecting the structure 3 has many similarities with the above system for cleaning the structure 3, and only differences between the two embodiments will be described herein.

It is now referred to fig. 10 and 11. A first difference is that the autonomous vessel 50 for inspecting the structure 3 is an autonomous inspection vessel, not an autonomous cleaning vessel. The autonomous inspection vessel comprises an inspection system 85 comprising a camera 86 secured to the body 51. The autonomous inspection vessel does not comprise a cleaning system 80 with brushes 81.

The inspection system may comprise one or several cameras. If one or a few cameras are used, the camera or cameras may be wide-angle cameras to be able to inspect a larger area of the structure 3. The above maximum cleaning depth CDmax may here be a maximum inspection depth. In fig. 12, it is shown that the inspection system 85 is connected to the navigation system via the communication system 90. Here, images from the camera 86 is sent to the navigation system 70, which is configured to check physical contact between the vessel 50 and the structure 3 by analysing images captured by the camera 86. As an example, if the structure is a net, the mesh size of the net will appear smaller in an image if there is an increase of the distance between the vessel and the net. Hence, by comparing the mesh size in the images with a threshold value, it is possible to detect whether or not the vessel is in physical contact with the net or not. If it is detected that the vessel is no longer in contact with the net as the mesh size in the images appear to be smaller, then the navigation system controls the propulsion system to move towards the net again.

Other alternative embodiments

In the present embodiment, the vessel 50 is located on the inside of the structure 3. This is of course a requirement when the structure 3 is an inner surface 3b of a tank. It is also an advantage when the structure 3 is a net 3a, as if a failure occurs, it will be easier to find and retrieve the vessel 50 again. In addition, there are typically fewer obstacles inside the net than outside of the net. However, when the structure 3 is a net, it would be possible to utilize the principles of the present invention to move the vessel 50 along the outside of the net. It should further be noted that the principles of the present invention may be utilized with the principles of NO 343736 in that the body 51 may be separated into two sections, a first section provided on the inside of the net and a second section provided on the outside of the net, where the two sections are magnetically connected to each other.

It should be noted that there are a number of various routes the vessel may move to cover the area of the net 3. As a further example, the vessel may move vertically up and down and then move horizontally at the top and at the bottom. In such a case, a cleaning width CW should be stored in either the route planner or in the central processing unit. A spiral-shaped route is also possible.

It is now referred to fig. 6. Here, it is illustrated that the horizontal vessel position P may be expressed with other parameters, for example as a position X, Y in the horizontal plane (for example with the center of the floating element as origo), as polar coordinates r, Q, etc. However, these alternative ways of expressing the horizontal vessel position P is still achieved by using information from the orientation sensor 71 alone.

The navigation system may comprise a rotation sensor rotated by the movement of the vessel as it is moving along the structure. The rotation sensor may be one of the brushes 81 of the cleaning system 80, or it may be a dedicated rotation sensor. The rotation sensor is measuring a parameter representative of a travel distance, which may increase the accuracy of the position of the vessel, in particular in structures having planar surfaces.

In fig. 13 and 14, it is shown that the vessel 50 is an autonomous cleaning and inspection vessel, comprising both a cleaning system 80 with brushes 81 and an inspection system 85 with cameras 86.

Claims

1. Autonomous vessel (50) for performing an operation in an aquatic organism containing structure (3) of an aquatic organism breeding farm (1), where the autonomous vessel (50) comprises: - a body (51);

- a propulsion system (60) for moving the vessel (50) relative to, and in physical contact with, the structure (3);

- a navigation system (70) for controlling the propulsion system (60); wherein the navigation system (70) comprises: - a orientation sensor (71) for measuring a parameter representative of the current orientation (V0) of the vessel (50);

- a depth sensor (72) for measuring a parameter representative of the current depth (D) of the vessel (50);

- a route planner (75); - a central processing unit (73) configured to control the propulsion system (60) based on information from the orientation sensor (71), the depth sensor (72) and the route planner (75).

2. Autonomous vessel (50) according to claim 1, wherein the route planner (75) comprises a parameter representative of a maximum depth (CDmax).

3. Autonomous vessel (50) according to claim 1 or 2, wherein the route planner (75) comprises a predefined route for the vessel (50) along the structure (3).

4. Autonomous vessel (50) according to any one of the above claims, wherein the central processing unit (73) is configured to control the propulsion system (60) to keep the vessel (50) in physical contact with the structure (3).

5. Autonomous vessel (50) according to any one of the above claims, wherein the orientation sensor (71) comprises a magnetic compass.

6. Autonomous vessel (50) according to any one of the above claims, wherein the orientation sensor (71) comprises a gyroscope.

7. Autonomous vessel (50) according to any one of the above claims, wherein a horizontal vessel position (P) is represented as an angle (a) between the vessel orientation (VO) and a reference orientation (N) in the navigation system (70).

8. Autonomous vessel (50) according to any one of the above claims, wherein the navigation system (70) is configured to check physical contact between the vessel (50) and the structure (3) by: - sending a control signal to the propulsion system (60) for moving the vessel (50) towards an assumed location of the structure (3);

- confirming physical contact if the movement of the vessel (50) is less than a threshold value based on the control signal;

- not confirming physical contact if the movement of the vessel (50) is above the threshold value based on the control signal.

9. Autonomous vessel (50) according to claim 8, wherein the central processing unit (73) is configured to determine a position for the vessel (50) based on the current orientation (V0), the current depth (D) and the confirmed physical contact between the vessel (50) and the structure (3).

10. Autonomous vessel (50) according to any one of the above claims, wherein the navigation system (70) comprises a timer for measuring time.

11. Autonomous vessel (50) according to any one of the above claims, wherein the navigation system (70) comprises a rotation sensor rotated by the movement of the vessel as it is moving along the structure (3), wherein the rotation sensor is measuring a parameter representative of a travel distance.

12. Autonomous vessel (50) according to any one of the above claims, wherein the autonomous vessel (50) is an autonomous cleaning vessel comprising:

- a cleaning system (80) provided at least partially outside of the body (51).

13. Autonomous vessel (50) according to any one of the above claims, wherein the autonomous vessel (50) is an autonomous inspection vessel comprising:

- an inspection system (85) comprising a camera (86) secured to the body (51).

14. System (10) for performing an operation in an aquatic organism containing structure (3) of an aquatic organism breeding farm (1), wherein the system (10) comprises:

- an autonomous vessel (50) according to any one of claims 1 - 13;

- a vessel station (20) provided preferably at sea level (SL).

15. System (10) according to claim 14, wherein the autonomous vessel (50) comprises a rechargeable battery system (95) for powering the navigation system (70) and the propulsion system (80), wherein the rechargeable battery system (95) is charged at the vessel station (20).

16. Method for performing an operation in an aquatic organism containing structure (3) of an aquatic organism breeding farm (1), wherein the method comprises the steps of: a) providing a vessel (50) comprising a body (51) within the structure (3) ; b) moving the vessel (50) relative to, and in physical contact with, the structure (3); c) measuring a parameter representative of the current orientation (V0) of the vessel (50); d) measuring a parameter representative of the current depth (D) of the vessel (50); e) providing a route plan for the vessel (50); f) controlling the movement of the vessel (50) by means of the route plan, the parameter representative of the current orientation of the vessel (50) and the parameter representative of the current depth (D) of the vessel (50).

17. Method according to claim 16, wherein the method further comprises controlling the movement of the vessel (50) to a maximum depth (CDmax).

18. Method according to claim 16 or 17, wherein the method step e) comprises the step of:

- determining a predetermined route for the vessel (50) along the structure (3).

19. Method according to any one of claims 16 - 18, wherein the method step f) comprises the step of:

- controlling the movement of the vessel (50) to keep the vessel (50) in physical contact with the structure (3).

20. Method according to any one of claims 16 - 19, wherein the method comprises the step of:

- representing a horizontal vessel position (P) as an angle (a) between the vessel orientation (VO) and a reference orientation (N).

21. Method according to any one of claims 16 - 20, wherein the method comprises the step of:

- sending a control signal to move the vessel (50) towards an assumed location of the structure (3);

22. Method according to any one of claims 16 - 21, wherein the step controlling the movement of the vessel comprises controlling the movement of the vessel by moving the vessel towards an assumed location of the structure and to move the vessel relative to, and in physical contact with, the structure.