KR102227893B1 - Supplementary Towing System for Enhancing Stability using Thrusters - Google Patents

Abstract

The present invention provides a system for adding stability in the process of towing an object, comprising: a thruster 20 installed on the object; Motion detection means (30) for detecting information related to the variation of the degree of freedom of the object; Environment sensing means (40) for detecting external force information acting on the object; And a control means (50) for varying the output applied to the thruster (20) in response to inputs of the motion detection means (30) and the environment detection means (40).
Accordingly, in the process of towing an offshore structure such as FPSO to a destination, it is effective to prevent transportation delays and maritime accidents by securing linear stability to maintain the position of the stern within a set range.

Description

Supplementary Towing System for Enhancing Stability using Thrusters}

The present invention relates to an apparatus for adding towing stability, and more particularly, to a towing stability adding system using a thruster for maintaining linear stability in a process of towing an offshore structure to a destination.

Since offshore structures such as FPSO/FSRU working at sea do not have their own propulsion capability, they are moved to the working sea area with the help of TUG ships. However, linear stability may be insufficient depending on the dynamic characteristics of the tugboat and the offshore structure itself. In this case, the towed FPSO/FSRU may cause periodic movement in the left and right directions based on the TUG line. This cyclical motion can cause problems such as input of additional TUG, increase in towing time, and excessive load on towing line.

Even in ships with self-navigation capability, problems related to linear stability may occur. In this case, the ship's linear stability has been improved by installing a skeg at the stern. However, in offshore structures such as FPSO/FSRU, if a skeg is installed, it may differ from the motion characteristics verified at the design stage, and it is very difficult to remove the skeg after the towing is finished. come. Or, by connecting the tail of the offshore structure to the additional structure, a method of reducing the sway of the ship by using the resistance of the additional structure has been studied. However, the auxiliary structure may collide with the offshore structure, and if the auxiliary structure is skewed to one side due to environmental loads such as wind and current, the linear safety of the towed offshore structure may be worse.

Prior Literature 1 below is an example system for offshore structures, comprising: a tugboat connected to the bow of the offshore structure; And a course stabilization unit connected to the stern of the offshore structure and unfolding in a parachute shape underwater to suppress hull agitation of the offshore structure. Accordingly, it is expected that course stability can be secured during towing and can be easily removed after towing.

Prior Literature 2 below is a frame formed to partially surround the stern of an object, which is an example; An additional body fixed to the rear of the frame; And reinforcing means installed to restrain the vertical motion of the frame. Accordingly, it is expected that it is easy to attach and detach without damaging the stern of the offshore structure, while reducing the fluctuation during the towing process to maintain the stability of the tugboat navigation.

However, the method of attaching a parachute or reinforcing means according to the preceding literature is insufficient to actively respond to changes in the environment, which is a variety of examples, so depending on the linearity of the object, it causes severe fish tailing, resulting in transport delays and marine There is a high risk of causing an accident.

1. Korean Laid-Open Patent Publication No. 2014-0065045 "Stable course towing system" (Publication date: May 29, 2014) 2. Korean Patent Application Publication No. 2015-0007610 "Removable towing stability additional device" (Publication date: 2015. 1. 21.)

It is an object of the present invention to improve the conventional problems as described above, adding towing stability using a thruster to secure linear stability by maintaining the position of the stern within a set range in the process of towing an offshore structure such as FPSO to a destination. It is in providing the system.

In order to achieve the above object, the present invention provides a system for adding stability in the process of towing an object, comprising: a thruster installed on the object; Motion sensing means for detecting information related to a change in the degree of freedom of the object; Environment sensing means for detecting external force information acting on the object; And a control means for varying an output applied to the thruster in response to inputs of the motion detection means and the environment detection means.

As a detailed configuration of the present invention, the object is characterized in that a plurality of thrusters having blades and actuators are provided at the stern.

At this time, the thruster is arranged by alternating the direction of the blades in the forward and reverse direction, but is characterized in that the thrust is generated in the same direction.

As a detailed configuration of the present invention, the motion detection means includes at least one of a posture sensor for detecting a posture of an object, a speed sensor for detecting a speed of the object, and a camera for detecting an operating state of the thruster.

As a detailed configuration of the present invention, the environmental sensing means includes at least one of a load sensor for detecting a change in towing force of an object, a wind speed sensor for detecting an effective wind speed acting on the object, and a current sensor for detecting an effective current speed acting on the object. It characterized in that it comprises a.

As a detailed configuration of the present invention, the control means includes a communication unit that transmits and receives information related to a towing of an object by wire or wireless, and a microcomputer unit that performs a set algorithm to change the rotational speed of the blades of the thruster.

At this time, the micom unit is characterized in that it stores and updates the appropriate rpm data of the blade corresponding to the towing speed of the object.

On the other hand, it is characterized in that the proper rpm data of the blade is accumulated by the occurrence of cavitation.

As described above, according to the present invention, in the process of towing an offshore structure such as FPSO to a destination, there is an effect of securing linear stability to maintain the position of the stern within a set range, thereby preventing transportation delays and maritime accidents.

1 is a schematic diagram showing the overall system according to the present invention
Figure 2 is a block diagram showing in more detail the system according to the present invention
3 is a graph showing the results of a model experiment of the system according to the present invention
4 is a photograph showing a cavitation phenomenon through the model experiment of FIG. 3
5 to 8 are graphs showing the stability range, which is an example derived from the model test of FIG. 3
9 is a graph showing the results of FIGS. 5 to 8 on the same coordinates

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The present invention proposes a system that adds stability in the process of towing an object. In the process of moving to the tugboat 10 using the FPSO as the object 15, fishtailing is reduced to improve the stability of the towing by maintaining the position (posture). This is based on the principle derived through model experiments that are partially explained throughout the specification, but is not limited thereto.

For reference, the model FPSO applied in the experiment was made in 1/64 scale, and the target towing speed was based on 6 knots. However, for comparison of the experimental results, the towing speed was divided into 0 knots, 4 knots, 6 knots, and 8 knots. Accordingly, it is revealed that Figs. 3 to 9 presented in the present invention are both results derived from the above-described model experiment.

According to the present invention, the thruster 20 is installed on the object. The thruster 20 is based on the principle of exerting a force in the opposite direction of the fishtailing of the object 15. The 6-degree-of-freedom (6-degree) motion of the tugboat, which is the object 15, is translational, rolling, and pitching of Surging, Swaying, and Heaving based on the orthogonal coordinate axis. It is composed of rotational motion components of (Pitching) and yawing. In the model experiment, fishtailing was monitored by the swaging of the object 15, but it can be configured to monitor further including other motion components in the actual ship.

As a detailed configuration of the present invention, the object is characterized in that a plurality of thrusters 20 having blades 22 and actuators 25 are provided at the stern. In FIG. 1, the driver 25 is illustrated at the center of the blade 22 only for convenience of understanding. The actuator 25 targets a motor having good rpm control responsiveness, but does not exclude other driving sources.

In the model experiment, several methods to improve the stability of FPSO's tow can be roughly divided into Bow Towing and Stern Towing. In the case of a bow towing, if one thruster (20) is used, the towing speed reaches 8 knots and the stability decreases, and the stern tow is practically inappropriate due to the absence of safety-related devices (Fore Peak, Collision Bulkhead, etc.). Accordingly, it was found that the use of a plurality of thrusters 20 while applying the bow towing was advantageous in terms of securing stability and realism.

At this time, the thruster 20 is arranged by alternating the directions of the blades 22 in the forward and reverse directions, but generates thrust in the same direction. The enlarged view of FIG. 1 illustrates a state in which three thrusters 20 are applied, and the fore side is denoted by 20F and the stern side is denoted by 20A and 20M in the middle. If the symbols 20F and 20A are installed to face the starboard side, the symbols 20M are installed to face the port side, so that the plurality of thrusters 20 form an arrangement structure in which the plurality of thrusters 20 are alternately arranged in the forward and reverse direction. This is advantageous in terms of stably generating thrust in the starboard and port directions than all the thrusters 20 are installed in the same direction. Of course, when 20F and 20A are driven in the forward direction (clockwise direction), the symbol 20M is driven in the reverse direction (counterclockwise direction) to generate thrust in the same direction.

Of course, the arrangement of the plurality of thrusters 20 can be variously changed as an optional design element. However, when the object is skewed in either direction of the left and right side due to lack of straight-line stability, it is necessary to generate thrust so that it can move in the opposite direction, so the arrangement of the alternating method is effective. Even in the case of the alternating method, the rotation direction of each blade 22 is adjusted so that the thrust direction of each thruster 20 is equally coincident in order to ensure straight-line stability.

Referring to FIG. 3, the result of observing the swinging motion of the object 15 in the model experiment can be seen. Fig. 3(a) shows that fishtailing intensifies over time in the case of a general method of towing, and particularly, an extreme swaging state at a towing speed of 8 knots. In the case of a towing using one thruster 20, FIG. 3(b) shows a severe swaging condition at a towing speed of 8 knots, although fishtailing is somewhat weaker than that of FIG. 3(a). Fig. 3(c) shows a relatively stable state even at a towing speed of 8 knots while the fishtailing is much weaker than that of Fig. 3(b) in the case of a towing using three thrusters 20.

On the other hand, as a result of the model experiment according to the present invention, an excerpt and exemplifies the swinging exercise, but shows similar characteristics to the yawing exercise.

In addition, according to the present invention, the motion detection means 30 is a structure for detecting information related to the variation of the degree of freedom of the object. The motion detection means 30 detects the swinging and yawing motions of the object as basic inputs, but may also detect other components including the surging motion. In addition, the motion detection means 30 also detects information related to internal factors that influence the variation of the degree of freedom of the object 15.

As a detailed configuration of the present invention, the motion detection means 30 includes a posture sensor 32 for detecting a posture of an object, a speed sensor 34 for detecting a speed of the object, and a thruster 20 for detecting an operating state. It characterized in that it comprises at least one of the cameras (36). The posture sensor 32 is composed of a gyro sensor, an acceleration sensor, a GPS sensor, etc. to detect the motion state of the tugboat 10. The speed sensor 34 may include an rpm detection of the blade 22 of the thruster 20 in addition to detecting the towing speed of the object. In addition to information for determining cavitation in the blade 22 of the thruster 20, the camera 36 generates information for determining the operating state of the main part as an image.

In addition, according to the present invention, the environment sensing means 40 is a structure for detecting external force information acting on the object. The environmental sensing means 40 detects information related to external factors that influence the variation of the degree of freedom of the object 15. Most of the motion sensing means 30 are temporarily mounted on the object 15, whereas the environmental sensing means 40 are preferably permanently mounted on the tugboat 10.

As a detailed configuration of the present invention, the environmental sensing means 40 includes a load sensor 42 that detects a change in towing force of an object, a wind speed sensor 44 that detects an effective wind speed acting on the object, and an effective current acting on the object. It characterized in that it comprises at least one of the tidal current sensor 46 for detecting the speed. The load sensor 42 is installed on a winch connected from the tugboat 10 to the object 15 to detect a signal according to a change in the towing force. The extreme fluctuations in the towing force can be used as direct and priority information for predicting fishtailing as a result. The wind speed sensor 44 is provided in plural so as to face in multiple directions to detect effective components related to fishtailing of an object. The tidal current sensor 46 may detect an effective component related to fishtailing by a Doppler effect of a signal generated from a multi-directional sound source. Of course, the wind speed and tide information may be referred to what is received from a remote base station server (not shown) through the communication unit 52 of the control means 50 to be described later.

In addition, according to the present invention, the control means 50 has a structure in which the output applied to the thruster 20 is varied in response to the inputs of the motion detection means 30 and the environment detection means 40. The control means 50 is installed on the tugboat 10 and corrects the signal generated by the moving tugboat 10 and the object 15, and calculates based on the detected signal, and the thruster 20 installed on the object 15 ) To perform output (thrust) control. The thrust force of the thruster 20 is proportional to the rpm of the actuator 25 connected to the blade 22.

Of course, the installation position of the control means 50 is not necessarily limited to the tugboat 10 and may be provided at least in part on the object 15.

As a detailed configuration of the present invention, the control means 50 is a communication unit 52 for transmitting/receiving information related to a towing of an object by wire or wireless, and a rotation speed of the blade 22 of the thruster 20 by performing a set algorithm. It is characterized in that it comprises a microcomputer unit 55 that changes. The communication unit 52 transmits and receives signals to and from the target 15 by wired or wirelessly, as well as wirelessly transmitting and receiving signals with a remote base station server. The server updates information on the tide direction, flow velocity, tidal difference, wave height, etc. of the water in connection with the Meteorological Agency. The microcomputer unit 55 is composed of a microprocessor, a memory, and an I/O interface. The set algorithm is stored and updated in memory. The output of the thruster 20 to the driver 25 is applied through an I/O interface.

At this time, the micom unit 55 is characterized in that it stores and updates the appropriate rpm data of the blade 22 corresponding to the towing speed of the object. As can be seen from the above experiment, fishtailing increases as the towing speed increases, but the driving of the thruster 20 to eliminate this must be performed within a set range. That is, when the rpm of the blade 22 exceeds an appropriate range, problems such as cavitation may occur. This is more clearly understood through the graphs of FIGS. 5 to 9.

Thus, the appropriate rpm data of the blade 22 is characterized in that it is accumulated by the occurrence of cavitation. Cavitation degrades the accuracy of thrust control for the thruster 20 and at the same time causes damage to the blades 22 and the like, and thus acts as an important design variable. In FIG. 4, reference numeral 27 denotes cavitation occurring at the outer end of the blade 22. Of course, when the three thrusters 20 are installed as shown in FIG. 1, cavitation is deepened at the stern side with the lowest depth.

In the experiment of the present invention, the towing speed of the object is set to 0, 2, 4, 6, 8 knots, and the rpm for one thruster 20 is changed stepwise from 130.4 to 228.4, while cavitation 27 is performed through the image. As a result of checking, the graphs of FIGS. 5 to 8 are completed. In the graph, the upper side of the red line indicates the area where cavitation occurs, and the lower side indicates the safe area without cavitation. Accordingly, in the present invention, the microcomputer unit 55 of the control means 50 stores this as an algorithm (table).

5 shows the case where the stern side thruster 20 is driven in the forward direction, FIG. 6 shows the case where the stern side thruster 20 is driven in the reverse direction, and FIG. 7 shows the case where the intermediate thruster 20 is driven in the forward direction. A case of driving is shown, and FIG. 8 shows a case of driving the intermediate thruster 20 in the reverse direction. Overall, it can be seen that the safety area is reduced in the stern side thruster with a low depth, and the safety area is reduced in the forward driving rather than the reverse driving. The black square point is the maximum rpm measured when driving the three thrusters, and is estimated as the thrust caused by one thruster. In other words, if the black point is below the red line, it means that a safe towing is possible.

However, in the case of 2 knots of tide, the ship's towing speed is 6 knots, but the incoming flow speed can be a maximum of 8 knots and a minimum of 4 knots. The red triangle reflects this and indicates the maximum and minimum estimated thrust, meaning that if the current occurs within 2 knots, there may be a thrust generated between them.

On the other hand, in the case of using the three thrusters 20 in FIG. 9, since the starboard direction and the port direction are mixed in different quantities, the thrust appears in an asymmetrical form according to the change in the forward and reverse rpm.

In conclusion, according to the calculated results, it seems that it can be safely used for a tide of about 2 knots in the case of 6 knots, but if the speed of the tide increases, it is better to secure an additional margin by lowering the limiting maximum rpm value. good.

As described above, in the present invention, when fishtailing occurs due to reduced stability in the process of towing the object 15 with the tugboat 10, the thruster ( The rpm of 20) is varied, thereby reducing unnecessary behavior of the object 15 to increase safety.

The present invention is not limited to the described embodiments, and it is apparent to those of ordinary skill in the art that various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, such variations or modifications will have to belong to the scope of the claims of the present invention.

10: tugboat 15: object
20: thruster 22: blade
25: actuator 30: motion detection means
32: attitude sensor 34: speed sensor
36: camera 40: environmental detection means
42: load sensor 44: wind speed sensor
46: tide sensor 50: control means
52: communication unit 55: microcomputer unit

Claims (8)

In a system that adds stability in the process of towing an object:
A thruster 20 installed on the object;
Motion detection means (30) for detecting information related to the variation of the degree of freedom of the object;
Environment sensing means (40) for detecting external force information acting on the object; And
Including; control means (50) for varying the output applied to the thruster (20) in response to the input of the motion detection means (30) and the environment detection means (40),
The control means 50 is a communication unit 52 for transmitting and receiving information related to the towing of an object by wire or wireless, a microcomputer unit 55 for varying the rotational speed of the blade 22 of the thruster 20 by performing a set algorithm. And,
The micom unit 55 stores and updates the appropriate rpm data of the blade 22 corresponding to the towing speed of the object. The method according to claim 1,
The object is a towing stability additional system using a thruster, characterized in that a plurality of thrusters (20) having a blade (22) and a driver (25) are provided at the stern. The method according to claim 2,
The thruster 20 is arranged by alternating the direction of the blade 22 in the forward and reverse direction, but generating a thrust in the same direction. The method according to claim 1,
The motion detection means 30 is at least one of a posture sensor 32 that detects the attitude of the object, a speed sensor 34 that detects the speed of the object, and a camera 36 that detects the operating state of the thruster 20 Towing stability additional system using a thruster, characterized in that it comprises a. The method according to claim 1,
The environmental sensing means 40 includes a load sensor 42 that detects a change in towing force of an object, a wind speed sensor 44 that detects an effective wind speed acting on the object, and a tidal current sensor that detects an effective current velocity acting on the object 46) towing stability additional system using a thruster, characterized in that it comprises at least one of. delete delete The method according to claim 1,
The proper rpm data of the blade (22) is an example stability addition system using a thruster, characterized in that it is accumulated by the occurrence of cavitation.

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