Patent Description:
Known trawling systems are based on controlling a vessel where an operator measures the position of a target volume as well as the position of the trawl and steers the vessel in so as to move the trawl through the measured moving target volume. Norwegian patent NO120174/<CIT> describes a well-known solution for locating a shoal of fish and thereafter aiming a trawl at said shoal of fish. Two sonar transducers with overlapping radiation fields in the horizontal plane, and two sonar transducers with overlapping radiation fields in the vertical plane, are used to aim the trawl at the shoal of fish. When the aiming operation is accomplished, the trawl is dragged along a straight line, behind the vessel, towards the shoal.

<CIT> describes a system for using the vessel steering system to control the trawl movements, while at the same time optimizing trawl symmetry. Norwegian patent <CIT>/<CIT>also discuss a system related to trawl symmetry. This is a complex operation and requires continuous monitoring of both trawl and target as well as environmental conditions such as wind and current. In addition, the trawl has to be controlled individually in order to
maintain the wanted shape and orientation of the trawl and to avoid damage to the trawl. Other uses of sensors for monitoring fish and trawl positions are also discussed in <CIT>, <CIT> and <CIT>.

Automatic systems have been suggested but are mainly aimed at controlling the vessel movements using traditional rudders, propulsion power and/or steerable propellers, and through this the following trawl, according to the target position. They are, however, as discussed above still based on the vessel steering as the main means to steer the trawl, including frequent course and velocity adjustments which increases energy consumption up to <NUM>% and wear on the equipment. It is an object of the present invention to provide a flexible and more efficient system, thus also reducing the fuel consumption and, hence reducing the environmental footprint. This is obtained by the invention defined in claim <NUM>.

The present invention is based on the realization that the vessel is only one of several components in a system for reaching the target volume, as for example the movement of the vessel may diverge in one direction due to wind while current as well as the target movement may require another type of movement for the trawl.

The present invention thus provide a means for automatic steering of the trawl toward the target area while taking into account such parameters as wind, current, vessel and trawl characteristics, and may also take into account bottom topography, other fishing equipment and floating or fixed objects etc. for calculating the trawl movements and steering the trawl. The trawl movements are prioritized while the vessel movements are only one of many possibilities to achieve this with as low power consumption as possible.

The system utilizes several steering methods, including the potential use of movements in three dimensions of the trawl by actively adjusting length and position of towing wires/leads, but also potentially actively using individually steerable and/or synchronized doors, deflectors and/or weights, the system utilizes in addition the steering effects of the vessel movements by moving towing points at the vessel, and adjusting length of towing wires/leads, as discussed in Norwegian Patent Application <CIT>/international application <CIT>, the system utilizes in addition the potential use of traditional vessel steering using rudders and propulsion. The individual steering methods are individually known but the present invention provides a system utilizing them to provide an improved system.

The present invention will be described more in detail below with reference to the accompanying drawings, illustrating the invention by way of examples.

<FIG> illustrates a vessel <NUM> having a path of movement 27a while towing a trawl <NUM> to be moved in a path 28a toward a target volume <NUM> e.g. containing fish or shrimps. Depending on the environmental conditions such as drag, current and wind, the trawl path of movement 28a may differ from the vessel path 27a and the relationship between these paths may be complex.

In addition there may be limitations to the freedom of maneuvering the vessel, and/or there might be limitations to the freedom of maneuvering the towed equipment due to for example other vessels, other fishing equipment and subsea topographical restrictions, these factors will potentially be taken into consideration when the system calculates the actual modus operandi from case to case ensuring the minimum use of energy, and thus increasing effectivity in the fisheries and reducing negative environmental impact.

The vessel path 27a is determined by the sum of forces over time.

The trawl path is determined by the sum of forces over time.

Disturbance in the form of e. g sub surface current will also affect the trawl vector over time.

The forces discussed above regarding control of both the trawl and vessel path by adjusting the tension and momentum of the wire drag from the trawl to the vessel is also discussed in Norwegian Patent Application <CIT>.

The forces affecting the vessel and trawl provide a number of variables that may be measured and used to move the trawl along an optimal and efficient path toward the target area. In addition, realizing that the main purpose of the movement is not the vessel path 27a but finding the optimal trawl path 28a when considering the minimum power consumption during the operation.

<FIG> illustrates an embodiment of a trawl having a number of sensors, where.

All of these measurements may be included in the calculation of the optimal trawl path along with the measurements of the target position and position of the trawl relative to the target as well as the vessel.

When a target volume is detected, e.g. using a sonar or echosounder system, the calculation means estimates an optimal path based on - fully or partly, but not limited to - the following:.

Based on these signals the system decides how the different alternatives may be used to steer the trawl in the optimal way toward the target volume. This may be performed dynamically depending on the movements of the target volume and how the trawl will meet it.

This is illustrated in the system shown in <FIG> where a trawl pilot <NUM> with a trawl pilot control <NUM> receives a number of data <NUM> such as, but not limited to the target volume fish school position, depth, size etc., as well as vessel parameters such as position, speed, rate of turn etc., current and wind data and other operational parameters. The trawl pilot <NUM> includes a route estimator <NUM> proposing a towed path <NUM>, e.g. based on economic priorities and based on this provides
necessary commands <NUM> to the trawl controller <NUM> including a trawl control unit <NUM> for adjusting parameters like angle of attach, trawl shape and trawl position.

These trawl movements are then achieved by providing suitable control signals <NUM> to the relevant steering means. This is done primarily by adjusting the weights and doors Ref <FIG>; <NUM> of the trawl as is well known in the art. Secondarily to adjust trawl gallows and blocks and winches <NUM> on the vessel, and finally to sending signals <NUM> to the vessel <NUM> engaging changes to the rudder and propulsion power <NUM> on the vessel (ref <FIG>). In order to obtain this the trawl controller <NUM> may also utilize measured or known information <NUM> about wire tension, doors positions and the symmetry of the system in order to optimize the trawl control. In order to maintain a degree of symmetry while using the doors to contribute to the steering, the individual doors may be synchronized in the control system.

The range of priority of above actions might vary in order to obtain the sum of actions ensuring the least use of energy and most effective route optimization. All of above while also taking into consideration the optimum shape of the complete trawl systems and the safest route regarding other vessels and other fishing equipment or other objects.

In this operation there is also a feedback where the effects on the trawl movements are predicted by a trawl predictor <NUM> (ref <FIG>) in the trawl controller and fed back to the route estimator <NUM> so as to provide a continuous adjustment of the trawl being added to the estimation model and thus influencing the estimated trawl trajectory.

In estimating the trawl trajectory some variations are allowed within an acceptable window of movements, so as to limit the need for fast and power consuming changes. This is illustrated in <FIG> where a safe envelop boundary <NUM> enclosing a safety margin is defined and within this an estimated boundary of controllability <NUM> of the trawl. As a safety precaution the operating boundary 42b is defined within this, wherein the route estimator and trawl control allow same variations in the trawl movements over a span of time <NUM>.

The acceptable window may thus be based on a model involving the following calculations:.

This may be achieved based on different estimator models such as, but not limited to:.

The precise nature of the models and calculations used by the route estimator will depend on the different types of trawls and vessels as well as the measurements provided by related sensors and instruments, as well as environmental conditions, e.g. variations in sea floor, depth, currents, trawl size, vessel maneuverability, and safe vessel routes avoiding dangerous or unwanted contacts with other vessels and other fixed or floating objects.

To summarize the present invention thus relates to a trawl steering system comprising a sea vessel and a trawl system, the system including a measuring unit such as a sonar or echosounder system for detecting and monitoring the position and movements of a target volume in the sea where the target volume may be constituted by a school, veil or haze of fish or shrimps to be caught in the trawl. The vessel also includes means for monitoring the position of the trawl relative to said target volume. The system comprising sampling means for sampling information including wind, current, and vessel and trawl characteristics and a route estimator for estimating the optimal route or path of the trawl. The system also comprises a trawl controller for adjusting vessel and trawl parameters so as to provide a movement for the trawl toward the target volume along said optimal path thus increasing the catch and reducing the bunker consumption and associated environmental impact.

The control means may include a vessel control unit calculating the vessel movements necessary to steer the trawl along the estimated route toward the target volume. The trawl also comprises steering means that are adapted to move the trawl relative to the vessel so as to move toward the target area, wherein the steering means include doors, deflectors or weights positioned at the trawl for adjusting the position in the lateral and/or vertical direction relative to said path along said trajectory.

The route estimator may include interfaces for receiving measurements from the environment, e.g. wind or current, measurements from the vessel and the trawl, as well as the measured movement of the target area and to calculate the trawl trajectory based on said measurements.

The system may also include a navigation unit monitoring the global position of the vessel, the system being adapted to measure the position of the target volume and the trawl relative to the vessel.

The system might also include signals from one or several radar units onboard the vessel, and/or other navigational systems giving information about fixed or floating objects to be avoided.

The steering means may include interactive use of moving the trawl towing points on the vessel laterally and/or vertically, and in addition possibly also by adjusting length of towing wires.

Claim 1:
Trawl steering system comprising a sea vessel (<NUM>) and a trawl system having a trawl (<NUM>), the trawl steering system including:
- a measuring unit adapted to detect and monitor the position and movements of a target volume (<NUM>) in the sea, the target volume (<NUM>) constituted by a school, veil or haze of fish or shrimps to be caught in the trawl (<NUM>), and to monitor the position of the trawl (<NUM>) relative to said target volume (<NUM>);
- sampling means adapted to sample information including wind, current, and vessel and trawl characteristics;
- a trawl pilot (<NUM>) comprising a route estimator (<NUM>) adapted to calculate an optimal trawl path (28a) and a trawl pilot control (<NUM>) adapted to send signals (<NUM>) to the vessel (<NUM>); and
- controller means (<NUM>) adapted to adjust vessel and trawl parameters so as to provide a movement for the trawl (<NUM>) toward the target volume (<NUM>) along said optimal path (28a), and to receive commands (<NUM>) from the trawl pilot (<NUM>);
- steering means comprising:
- weights, doors (<NUM>) or deflectors arranged on the trawl (<NUM>), and wherein the weights doors (<NUM>) or deflectors are adapted to receive control signals (<NUM>) from the controller means (<NUM>) and to adjust the position of the trawl (<NUM>) relative to the sea vessel (<NUM>);
- trawl towing points on the vessel (<NUM>), wherein the trawl towing points are movable laterally and/or vertically on the vessel (<NUM>), and towing wire being adjustable in length; and
- automation systems, hardware and software systems, which are based on artificial intelligence to provide a hierarchical list of actions comprising a priority of navigational means to ensure the safest trawl path using the least amount of energy, said hierarchical list of actions including one or more of:
- adjustment of the weights, doors (<NUM>) or deflectors,
- lateral and/or vertical movement of the trawl towing points on the vessel (<NUM>), possibly including length adjustment of the towing wires, and
- use of the vessel's rudder and propulsion power (<NUM>).