WO2006011807A1

WO2006011807A1 - Method and device for position monitoring

Info

Publication number: WO2006011807A1
Application number: PCT/NO2005/000279
Authority: WO
Inventors: Henning Skjold-Larsen
Original assignee: Henning Skjold-Larsen
Priority date: 2004-07-29
Filing date: 2005-07-27
Publication date: 2006-02-02
Also published as: CA2575434A1; GB2431084A; GB2431084B; IS8605A; GB0703768D0; NO321070B1; NO20043222D0

Abstract

The invention relates to a method for monitoring the position of plate gear (30, 31) for fishing gear, comprising measuring at least one angle (ALPHA 30, ALPHA 31) for at least a part of the plate gear, and based on the measurement providing a position indication for the plate gear with regard to bottom contact. The invention also relates to an apparatus for performing the method.

Description

Method and apparatus for position monitoring

The present invention relates to a method and an apparatus for monitoring the position of plate gear for fishing gear. The invention is a further development of the method and apparatus described in NO 20040464, the content of which is hereby incorporated in its entirety in the present application.

The object of such monitoring is to enable the position of the fishing gear in the water to be charted in an optimal manner.

During trawling operations it is important to know whether the trawl or associated equipment is in contact with the bottom. In bottom trawls, for example, it is desirable to have bottom contact for most of the time in order to ensure that fish swimming close to the bottom are caught, or to establish a dust cloud near the bottom which scares the fish into the gear.

At other times it is desirable to maintain a certain distance from the bottom (pelagic trawl), in order, for example, to protect coral and other plants and animals. Not least it is important to keep a certain distance from the bottom or maintain a contact with the bottom that is limited to the surface of the bottom, in order to prevent the fishing gear from digging into the bottom.

The position of the trawl will of course also depend on the type of fish that is to be caught. According to the prior art, bottom contact sensors are used to establish whether the trawl is moving along the bottom or not. A bottom contact sensor is a tubular body fastened to the trawl at one end with the other end hanging freely. The bottom contact sensor will indicate "bottom contact" / "no bottom contact" depending on the angle between the longitudinal direction of the tubular body and the horizontal direction. When the bottom gear moves freely, the longitudinal direction of the tubular body will form a larger angle with the horizontal than when there is bottom contact. However, if there are large irregularities on the bottom, i.e. depressions and elevations, the bottom contact sensor will not be capable of providing reliable information. Measurement of the angular position of a part of a trawl is known from, for example, GB 1 221 276, relating to an apparatus with a measuring unit for measuring two angles for the said part. The publication discloses spherical elements attached to the lower part of the trawl.

Large fishing gear such as trawls comprises modules which ensure that a certain position of the trawl is maintained during the fishing process. One example of such a module is so-called plate gear, one of whose functions is to ensure that the trawl moves along the bottom with the trawl in an open position.

The plate gear is an apparatus with several plates attached to one another by means of wire, rope and/or other attachment devices. The term plate in the present description refers to relatively flat bodies. Each plate normally has four attachment points, where the plates together with the attachment devices form a flexible device. The apparatus in turn is attached to the lower part of the trawl at individual points. During trawling the apparatus will be bent with the result that some plates will remain located in a plane substantially perpendicular to the trawl's towing direction (the middle part of the apparatus) while others will be in a plane substantially parallel to the trawl's direction of travel (the sides of the apparatus).

The plates mounted in the middle part of the trawl can assume a tilted position relative to the vertical plane. If the plates tilt forwards (i.e. in the direction towards the boat) the plate gear will partly lose contact with the bottom. The fish will therefore be able to swim under and out of the trawl. If the plates tilt backwards, they will dig down into the bottom, resulting in an undesirable accumulation of material in the trawl.

For this reason it is important to be able to monitor the position of the plates at least with regard to the vertical plane. The angular position of the plates can be described by means of three angles: a) Orientation angle: this is the angle that the plates' plane forms with the trawl's direction of travel. As mentioned earlier, with regard to the plates in the middle of the apparatus, the plates' plane will form an angle of around 90 degrees with the trawler's direction of travel, while the plates on the sides will form an angle of around 0 degrees. b) Angle of tilt: this is the angle that the plates' plane forms with a horizontal plane. This angle must be as close to 90 degrees as possible in order for the plate gear to function as efficiently as possible. In the following description "positive" angles will be defined as angles where the plate tilts towards the trawler (i.e. leading to poor bottom contact if a certain threshold is exceeded), "negative" angles are those that will lead to the plate digging into the bottom. c) Angle of pitch: this is the angle that the plates' upper and lower edges form with a horizontal plane.

As mentioned earlier the plates' angular position will vary depending on the plates' position along the apparatus. For the plates on the side portions of the apparatus it will be more important to measure the angle of pitch than the angle of tilt, while the angle of pitch will not be important for the plates in the middle of the apparatus (the angle of tilt will be the important one in this case). Thus it is an object of the invention to provide a method and an apparatus that permit monitoring of the position of plate gear comprising at least one plate, where measurements may be made of the angular position of either a single plate or of one or more groups of plate elements. It is also an object of the invention to provide a method for automatic selection of the most appropriate plate/group for measuring the angular position.

The choice of plate/group for measurement can be undertaken on the basis of the plate's/group's fixed position in the plate gear, i.e. whether the plate is located in the middle of the plate gear, on the sides or in an area between these positions. It will also be possible to select plate/group on the basis of the plate's/group's orientation angle, since it will be possible to measure the relevant angle for a plate and/or a group with the orientation angle located within a specific range of values. The orientation angle can also be measured for a single plate and the same value assigned to other plates in the same group, in order thereby to provide a position indication of the whole plate gear based on only a few measurements.

The method according to the invention comprises taking measurements of at least one angle for at least a part of the plate gear and providing a position indication for the plate gear based on the measurement. The plate gear comprises several plates and the measurement is carried out for individual plates and/or for groups of plates. The groups can be defined on the basis of the position of the plates in the plate gear and/or on the basis of the orientation angle. In the latter case, values for the orientation angle will be defined that provide limits for the groups.

The method according to the invention therefore comprises:

- measuring at least one angle for at least a part of the plate gear, where the said part of the plate gear may comprise one single plate or at least one group of plates,

- based on the measurement providing a position indication for the plate gear.

In an embodiment the method comprises measuring the angle of tilt or the angle of pitch depending on the plates'/group's position in the plate gear or the plates'/group's orientation angle. The first alternative will lead to a measurement which, for example, is based on the plate gear being in a symmetrical position relative to the vessel's direction of travel, while the second alternative opens up the possibility that the most appropriate plate/group for measurement varies during the trawling operation.

The position indication could consist of individual angular values provided by the measurement. Such a position indication will show whether the plates are tilting towards/away from the vessel and will be able to be used for controlling the plate gear's position. The position indication may also comprise an indication of the "bottom contact/no bottom contact" type, or a graphic presentation showing the angular variation and/or position relative to the bottom in time. In the same way as described in NO 20040464, moreover, it will be possible by means of the invention to know whether the gear is in the process of coming into contact with the bottom or in the process of leaving it. This will be implemented by means of average/standard deviation calculations for groups with angular measurements.

The measurement may comprise measuring the angle of tilt, the orientation angle and/or the angle of pitch. Where the angle of tilt and orientation angle are measured, the method may comprise providing position indication based on the values of the orientation angle and the angle of tilt.

The angular measurement is preferably performed by means of an inclinometer.

The method will advantageously comprise display of the position indication, where this comprises the value of at least one angle. It is possible, of course, to provide the position indication and not display it directly, but to give a message as to whether a threshold is exceeded or not, or to employ the position indication for controlling the plate gear with or without display. The control will comprise regulation of the tightening on the wires connected to the plate gear.

In this connection, the method may comprise comparing the value of at least one angle with a first threshold value and providing position indication based on the result of the comparison. The position indication may also be associated with the triggering of an alarm.

In an embodiment the method according to the invention comprises calculating average and standard deviation for the measurements, and providing a position indication for the plate gear with regard to the transition bottom contact/no bottom contact based on average/standard deviation for a collection of angular measurements.

The position indication in the form of a position indication signal can be transmitted acoustically to a receiver on the surface by means of a cable connection by radio signals or wirelessly or in some other way. It may also be stored in a memory unit on a module in the plate gear or in another location in the vessel.

The invention also comprises controlling the plate gear's position based on the indication signal(s) and desired values.

The invention also comprises an apparatus for monitoring the position of plate gear for fishing gear, where the plate gear comprises at least one plate, comprising: - a measuring unit for measuring at least one angle for at least a part of the plate gear, the said part of the plate gear comprising a single plate and/or at least a group of plates,

- a processing unit for providing, based on the measured value, a position indication for the plate gear,

- a memory unit. Advantageous embodiments of the apparatus are indicated in the attached dependent claims.

The invention will permit the position of the different plates in the plate gear to be controlled, thereby initiating measures for obtaining a fishing operation that is as efficient as possible. Any errors will be able to be detected and remedied quickly by means of the invention.

List of figures

Fig. 1 is a front view of a plate gear. Fig. 2 illustrates a plate gear viewed from above.

Fig 3 is a view like that in fig. 2, illustrating the angles for the plate gear. Fig. 4 illustrates a plate viewed from in front and from the side. Fig. 5 illustrates an inclinometer 50 placed on a plate 2. Fig. 6 illustrates an embodiment of an apparatus according to the invention. Fig. 7 illustrates an embodiment of a plate gear. Fig. 8 illustrates a plate gear in use. Fig. 9 is a screen image illustrating a position indication provided by means of the invention for fishing gear during use.

Fig. 10 is a screen image similar to that in fig. 9, during lowering of the fishing gear.

Detailed description Fig. 1 is a front view of a plate gear. The plate gear 1 comprises several plates 2 attached to one another by means of attachment devices 4 (wires, ropes, etc.). Each plate has several attachment points 3 against the attachment devices 4. The figure also illustrates an attachment point 6 for attaching the apparatus 1 to the lower part of the trawl by means of a rope 5. Fig. 2 illustrates a plate gear viewed from above. In the figure the trawl has reference numeral 20 and a part of the bottom gear reference numeral 1 1. B indicates the vessel's direction of travel. As can be seen, the plate gear 1 will be bent during trawling and some plates 2 remain located in a plane substantially perpendicular to the direction of travel while others are located in a plane substantially comprising the direction of travel.

Some of the angles defined for the plate gear are illustrated in figure 3. The orientation angle is the angle that the plates' 2 plane forms with the direction of travel. The figure illustrates orientation angles α30 and α31 for two plates. It can be seen that the nearer the middle of the plate gear 2 a plate is located, the smaller the orientation angle α will be.

Figure 4 illustrates angle of pitch γ and the angle of tilt β for an individual plate 2. The directions towards the surface and towards the bottom are illustrated by the arrows 42 and 43 respectively. Figure 4a illustrates the plate 2 viewed from in front, and the edges 40 and 41 which will define the angle of pitch with the horizontal. Figure 4b illustrates the angle of pitch γ. Figure 4c illustrates the direction of travel B and angle of tilt β. Positive angles are defined as angles where the plate's upper edge 40 approaches the trawl as illustrated in the figure.

Fig. 5 illustrates an inclinometer 50 placed on a plate 2. As mentioned earlier, this may involve an inclinometer with one, two or three axes, permitting measurement of the angles of orientation, tilt and pitch respectively.

In an embodiment of the invention it will be possible to choose to provide a position indication for a specific group of plates, and another position indication for another group of plates. Based on the position of the plates relative to the vessel's direction of travel (orientation angle), it will therefore be possible to decide whether the angle of tilt or the angle of pitch will be taken into account for the position indication. Figure 6 illustrates an embodiment of an apparatus according to the invention. This comprises a measuring unit 50 (advantageously an inclinometer) that measures one or more angles for at least a part of the plate gear 2. The angles are orientation angle O, angle of tilt V and angle of pitch S. Even though the figure only shows one measuring unit 50, it will be obvious that as many measuring units may be employed as there are plates 2. The measurements are transmitted to a processing unit 60, which can either handle the measurements for all the plates or include individual processing units for each plate connected to a central processing unit. In the processing unit a position indication is provided with regard to bottom contact. The position indication may be provided, for example, by comparing the measured angles O, V and/or S with threshold values 63 (in this case the position indication will be associated with the difference between measured and threshold values), or it may consist of values for specific angles (i.e. in the form of O=40 degrees, V=O degrees), or values derived therefrom. In the same way as with the measurements, a position indication will be able to be provided for each individual plate, for groups of plates or for the whole plate gear as a single element.

The apparatus may comprise a display unit 62 for displaying the position indication, and/or an alarm 64 which is triggered when a specific threshold is exceeded. The apparatus may also include a transmitter unit 65 for transmitting the position indication to a receiver 66. The apparatus may also include a memory 67 for storing the position indication.

Finally, the apparatus may comprise a control unit connected to the processing unit for controlling the plate gear's position based on the position indication and desired values.

Figure 7 illustrates an embodiment of a plate gear 1. The reference numerals refer to parts corresponding to the description of figure 1. Reference numeral 70 refers to a load, here in the form of a chain, for increasing the weight of the plates.

Figure 8 shows a plate gear in use. Figure 9 shows a screen image with an indication of different parameters associated with a trawling operation. The fields on the image will be described from the top and downwards and from left to right. A first field DP illustrates the depth of the trawl in metres (130m), two TSP fields illustrate the trawl's speed and also the angle between water flow and the trawl's direction of travel. The DST field shows distance between the doors. The following TLT fields show angular values, where the last field, TLT with value R -91, illustrates the orientation angle for the middle plate in a plate gear. This angle is 91 degrees and the plates' lower edge is located closer to the towing vessel than the plates' upper edge. The figure 0 shows standard deviation for the angle. The field at the bottom right shows amongst other things the distance between the trawl's lower edge and the bottom, C: 0.1m.

Figure 10 illustrates a similar screen image but indicating different parameters obtained while the fishing gear is being lowered. It can be seen that the orientation angle TLT is -1 1 degrees with a standard deviation of 2. The distance C between the trawl's lower edge and the bottom is 5.4m. Even though the invention is illustrated by means of an example where the plates comprise four attachment points, it is possible to measure the angular position of plates that are attached in another way, i.e. with more or less than four attachment points. It is also possible to provide a position indication for only one plate, for example the plate in the middle, and to employ the said position indication for controlling the tightening of the attachment devices.

Claims

1. A method for monitoring the position of a plate gear for fishing gear, where the plate gear comprises at least one plate, characterised by - measuring at least one angle for at least a part of the plate gear, where the said part of the plate gear comprises a single plate or at least a group of plates,

- based on the measurement, providing a position indication for the plate gear.

2. A method according to claim 1, comprising measuring the angle of tilt or the angle of pitch depending on the position of the plates/groups in the plate gear or on the orientation angle of the plates/groups.

3. A method according to claim 1 , characterised in that it comprises measuring the angle of tilt.

4. A method according to claim 1, characterised in that it comprises measuring the orientation angle.

5. A method according to claim 3 or 4, characterised in that it comprises providing position indication based on the values of the orientation angle and the angle of tilt.

6. A method according to one of the preceding claims, characterised in that it comprises displaying the position indication, and this includes the value of at least one angle.

7. A method according to one of the preceding claims, characterised in that it comprises comparing the value of at least one angle with a first threshold value and providing position indication based on the result of the comparison.

8. A method according to claim 7, characterised in that the position indication comprises triggering an alarm.

9. A method according to one of the preceding claims, characterised in that it comprises calculating average and standard deviation for the measurements, and providing a position indication for the plate gear with regard to bottom contact based on average/standard deviation.

10. A method according to one of the preceding claims, characterised by transmitting the position indication signal(s) to a receiver on the surface by means of a cable connection, acoustically, by radio signals or wirelessly in some other manner.

1 1. A method according to one of the preceding claims, characterised in that it comprises storing the position indication signal(s) in a memory unit on the module.

12. A method according to one of the preceding claims, characterised in that it comprises controlling the plate gear's position on the basis of the indication signal(s) and desired values.

13. A method according to one of the preceding claims, characterised in that the angular measurement is performed by means of an inclinometer.

14. An apparatus for monitoring the position of plate gear for fishing gear, where the plate gear comprises at least one plate, and the apparatus comprises a measuring unit for measuring at least one angle for at least a part of the plate gear, where the said part of the plate gear comprises a single plate or at least one group of plates, a processing unit for providing, based on the measured value, a position indication for the plate gear, and a memory unit.

15. An apparatus according to claim 14, characterised in that measuring unit is arranged to measure the angle of tilt or the angle of pitch depending on the position of the plates/groups in the plate gear or on the orientation angle of the plates/groups.

16. An apparatus according to claim 14, characterised in that the measuring unit is arranged for measuring the angle of tilt.

17. An apparatus according to claim 14, characterised in that the measuring unit is arranged for measuring the orientation angle.

18. An apparatus according to claims 16 and 17, characterised in that the processing unit is arranged for providing the position indication based on measurements of the angle of tilt and the orientation angle.

19. An apparatus according to one of the preceding claims 14-18, characterised in that it comprises a display unit for displaying the position indication.

20. An apparatus according to claim 19, characterised in that the position indication comprises the value of at least one angle.

21. An apparatus according to claim 14, characterised in that the processing unit is arranged for comparing the value of at least one angle with a first threshold value and providing the position indication based on the result of the comparison.

22. An apparatus according to claim 21, characterised in that it comprises an alarm arranged to be triggered if the threshold value is exceeded.

23. An apparatus according to claim 22, characterised in that the processing unit is arranged for calculating average and standard deviation for the measurements of at least a second angle, and providing a position indication based on average/standard deviation.

24. An apparatus according to claim 23, characterised in that it comprises a transmitter unit for transmitting the position indication to a receiver.

25. An apparatus according to claim 24, characterised in that the memory unit is arranged for storing the position indication signal.

26. An apparatus according to claim 14, characterised in that it comprises a control unit connected to the output unit for controlling the plate gear's position on the basis of the bottom contact indication signal and desired values.

27. An apparatus according to claim 26, characterised in that the measuring unit is a one, two or three-axis inclinometer.