WATERCRAFT, IN PARTICULAR TUGBOAT

Abstract

A tugboat for assisting cargo vessels has the following features: at least one propelling unit and a tow line for establishing a pulling connection between the cargo vessel and the tugboat. A measuring device measures the bollard pull and a central processing unit records the measurement result and forms a control command relating to the propelling force and/or the propelling direction for propelling purposes.

Claims

1-17. (canceled)

18. A tugboat for assisting a cargo vessel, comprising: at least one drive and a control device controlling said at least one drive; at least one tow line for establishing a pulling connection between the cargo vessel and the tugboat; at least one detecting device for detecting at least one variable directly or indirectly characterizing a bollard pull between the cargo vessel and the tugboat, said at least one detecting device including a device for detecting a variable describing a change of an ambient condition of the tugboat causing the bollard pull; a controller connected to receive from said at least one detecting device the at least one variable characterizing the bollard pull, said controller being configured to form at least one control variable for activating said control device of said at least one drive for influencing one or both of a thrust force or a thrust direction of the tugboat; and said controller including an analyzer configured to derive a theoretical changing behavior of an actual value of the bollard pull over time from variables describing a motion of the tugboat and/or variables describing the ambient condition of the tugboat under the influence of said variables and to provide the theoretical changing behavior of the actual value of the bollard pull over time to a comparison between a target value and an actual value.

19. The tugboat according to claim 18, wherein said controller is a closed-loop controller.

20. The tugboat according to claim 18, wherein said detecting device is a device selected from the group consisting of a force sensor and a torque sensor, and said detecting device is disposed in a region of a cable device guiding the tow line.

21. The tugboat according to claim 18, which further comprises a target value specification device for specifying a target value for the bollard pull to be set, and wherein: said target value specification device is coupled to said controller; and said controller includes a comparator configured to compare the target value with the actual value and a control variable generator configured to generate a control variable for activating the control device for changing the direction of thrust and/or a thrust force of an individual said drive.

22. The tugboat according to claim 21, wherein said at least one drive is one of at least two drives each being a Voith Schneider propeller.

23. The tugboat according to claim 18, wherein said at least one drive is one of at least two drives each being a Voith Schneider propeller.

24. The tugboat according to claim 23, wherein said at least one detecting device for the detection of a variable describing the ambient condition of the tugboat causing a change of the bollard pull is configured to detect a variable describing a motion of the tugboat and to detect a variable describing the ambient conditions of the tugboat.

25. The tugboat according to claim 24, wherein said at least one detecting device comprises at least one device selected from the group of devices consisting of: a roll angle detecting device; a course angle detecting device; a course angle rate of change detecting device; a course angle acceleration detecting device; a roll angle acceleration detecting device; a pitch angle detecting device; a pitch angle acceleration detecting device; a wave height detecting device; a wave frequency detecting device; and wave direction detecting device.

26. The tugboat according to claim 18, which further comprises a target value specification device for specifying a target value for the bollard pull to be set, and wherein: said target value specification device is coupled to said controller; and said controller includes a comparator configured to compare the target value with the actual value and a control variable generator configured to generate a control variable for activating the control device for changing the direction of thrust and/or a thrust force of an individual said drive; and said at least one detecting device for the detection of a variable describing the ambient condition of the tugboat causing a change of the bollard pull is configured to detect a variable describing a motion of the tugboat and to detect a variable describing the ambient conditions of the tugboat.

27. The tugboat according to claim 18, wherein said controller is a controller for said at least one drive or is integrated therein.

28. A method for closed-loop control of a bollard pull between a cargo vessel and a tugboat, wherein the tugboat has at least one drive, a tow line for establishing a pulling connection to the cargo vessel and a controller or closed-loop controller, the method comprising: in a first control concept, detecting an actual value of a variable at least indirectly characterizing the bollard pull in the pulling connection and, if the actual value exceeds and/or deviates from a predefined target value, activating the at least one drive of the tugboat for influencing one or both of a thrust force or a thrust direction of the tugboat; and in a second control concept, detecting the actual value of the variable at least indirectly characterizing the bollard pull in the pulling connection and determining a change of the actual value occurring with a time lag, and, if the actual value deviates from the predefined target value, activating the at least one drive for influencing one or both of the thrust force or the thrust direction of the tugboat.

29. The method according to claim 28, wherein the second control concept is overlaid on the first control concept.

30. The method according to claim 29, which comprises predetermining the target value as a permissible maximum value for a line force on the tow line or a predefined average value that is to be achieved for the line force.

31. The method according to claim 29, which comprises determining at least one of the following variables: a variable at least indirectly describing a motion of the tugboat; a variable at least indirectly describing external ambient conditions of the tugboat; and determining the change of the actual value occurring with a time lag as a function of at least one of the variables or derived the change of the actual value occurring with a time lag from at least one of the variables.

32. The method according to claim 28, which comprises predetermining the target value as a permissible maximum value for a line force on the tow line or a predefined average value that is to be achieved for the line force.

33. The method according to claim 32, which comprises determining at least one of the following variables: a variable at least indirectly describing a motion of the tugboat; a variable at least indirectly describing external ambient conditions of the tugboat; and determining the change of the actual value occurring with a time lag as a function of at least one of the variables or derived the change of the actual value occurring with a time lag from at least one of the variables.

34. The method according to claim 33, which comprises detecting at least one variable selected from the following group of variables as a variable at least indirectly describing the motion of the tugboat: a roll angle; a course angle; a course angle rate of change; a course angle acceleration; a roll angle acceleration; a pitch angle; and a pitch angle acceleration.

35. The method according to claim 33, which comprises detecting at least one variable selected from the following group of variables as a variable at least indirectly describing the external ambient conditions of the tugboat: a wave height; a wave frequency; and a wave direction.

36. The method according to claim 28, wherein detecting the actual value of the variable at least indirectly characterizing the bollard pull in the pulling connection comprises detecting at least one of the variables: a pulling force or line force; and a torque on a winch of a cable device.

37. The method according to claim 28, which comprises detecting at least one of the following variables continuously or at predefined time intervals: the actual value of a variable at least indirectly characterizing the bollard pull in the pulling connection; a variable at least indirectly describing a motion of the tugboat; and a variable at least indirectly describing external ambient conditions of the tugboat.

Description

[0074] The invention is described using the figures. In the figures, the following are illustrated in detail:

[0075] FIG. 1 shows by way of example an escort situation of a tugboat with a cargo vessel;

[0076] FIG. 2a illustrates in a schematic simplified representation the basic configuration of a control and/or regulating device;

[0077] FIG. 2b illustrates in a schematic simplified representation the advantageous overlaying of the first and second regulation concepts;

[0078] FIGS. 3a and 3b show by way of example embodiments of escort tugboats with controllable drives.

[0079] FIG. 1 illustrates in a schematic simplified representation and by way of example a tugboat 1 designed according to the invention for assisting or escorting cargo vessels 2, for example a tanker vessel. The outlines of the individual watercraft are only indicated schematically here. The tugboat 1 comprises at least one drive 3, here by way of example two drives 3. Said drives are in the form of Voith-Schneider propellers in a particularly advantageous design, and in the illustrated case are disposed symmetrically relative to a central longitudinal axis LS lying in the longitudinal direction of the tugboat 1. For assisting, a pulling connection Z is provided between the tugboat 1 and the cargo vessel 2. The pulling connection Z is implemented by means of a tow line 4. Such tow lines 4also referred to as towing cablesare reeled on the tugboat 1 for example on winches or are hung on hooks. In the first case, the tugboat 1 comprises a suitable cable device 5 for this. Said cable device comprises by way of example at least one winch and a drive associated with the winch.

[0080] The force that can be transferred by means of the pulling connection Z between the tugboat 1 and the cargo vessel 2 is characterized by the connecting element that is implementing said force, in particular the tow line 4. The tow line 4 itself is configured for a certain predefined force to be transferred, which is also referred to as the line force regardless of the selected material of the tow line. The bollard pull present in the pulling connection Z is limited by the maximum permissible line force and the maximum permissible load on the attachment elements, in particular for attaching the bollard to the cargo vessel 2. Therefore, a target value specification X.sub.soll is carried out for the bollard pull on the tugboat 1 that is to be set in the pulling connection Z. Depending on the regulation concept and regulator version, the target value can be set as a permissible maximum value that may not be exceeded, and if the value is exceeded the drives 3 are activated such that the target value or a value below the target value is set. According to a second version, in the event of a deviation (exceeding or falling below) of the actual value X.sub.ist from the target value X.sub.soll, the drive or the drives 3 is/are activated such that the target value X.sub.soll is set. In this case the target value preferably describes and corresponds to a predefined average value for the line force.

[0081] The target value specification for the bollard pull X.sub.soll is preferably carried out as a target value specification directly for the line force to be set or to be applied. It is also conceivable to describe said target value by means of a variable at least indirectly characterizing the bollard pull. In this case, such variables at least indirectly characterizing the bollard pull have a functional or direct relationship to the bollard pull.

[0082] The specification of a target value X.sub.soll of a bollard pull to be set or of a line force to be set is carried out for example by means of a target value specification device 7, which can be implemented in various ways.

[0083] A defined length of the tow line 4 is provided on the cable device 5 itself by means of a control device 6 in the event of a pulling connection request. In FIG. 1, the cargo vessel 2 and the tugboat 1 are suitably positioned relative to each other. The two central longitudinal axes LS of the tugboat 1 and LT of the cargo vessel are oriented at an angle alpha relative to each other in the illustrated position.

[0084] The angle alpha corresponds in this case to the yaw angle of the tugboat 1.

[0085] External forces act on the tugboat 1, in particular wind and wave forces of considerable magnitude, which would temporarily massively increase the pull acting on the tow line 4 without countermeasures. This is prevented according to the invention by turning the tugboat 1 by acting on the drives 3, 3 in the sense of the arrow 14. According to the invention, an actual value X.sub.ist of a variable at least indirectly characterizing the bollard pull is detected preferably continuously or at predefined time intervals for this and is compared with the target value X.sub.soll. In the event of a deviation of the actual value X.sub.ist from the target value X.sub.soll, at least one control device 13 of the individual drive 3 is activated. At least one detecting device 8 for an actual value X.sub.ist of a variable at least indirectly characterizing the bollard pull X.sub.ist is provided for this. The detection of the bollard pull is preferably carried out directly and the detecting device is in the form of a detecting device for the currently existing line force. It is also conceivable to determine the actual value of the line force not directly but by means of the detection of the actual values of other variables that have a direct or functional relationship to the line force, wherein the actual value X.sub.ist is then formed from said variables.

[0086] The detecting device 8 is preferably disposed in or on the cable device 5. In the simplest case, the devices that are provided anyway for measuring the line force in the winch are used for this.

[0087] For the comparison of the actual value X.sub.ist with the target value X.sub.soll and for activating the individual drives 3, the control and/or regulating device 10 is configured and designed to carry out the functions of the comparison and the generation of the control variable. Said control and/or regulating device 10 comprises for example a comparator 12 and a control variable generator 15, which forms the control variable Y.sub.3 for activating the control device/control devices 13 of an individual drive 3 using the determined deviation X between the target value and the actual value.

[0088] According to the basic configuration of the regulator and hence a first regulation concept, an active correction is only carried out if there is a deviation X.

[0089] According to a particularly advantageous development, it is however provided to respond predictively to the factors influencing the line force. For this purpose, for a second regulation concept preferably overlaying the first regulation concept, the external variables causing a change in the behavior of the bollard pull, in particular an external variable at least indirectly influencing the motion of the tugboat 1, such as for example the swell, are detected in terms of the height and/or direction thereof. The external variables at least indirectly influencing the motion of the tugboat are variables selected from the group of variables mentioned below: [0090] the variables directly describing the motion of the tugboat 1, such as for example at least one of the variables mentioned below [0091] roll angle [0092] course angle [0093] course angle rate of change [0094] course angle acceleration [0095] roll angle acceleration [0096] pitch angle [0097] pitch angle rate
or variables with a functional or direct relationship thereto, such as wave frequency, wave height and wave direction. Said variables are fed as input signals to the control and/or regulating device 10. In said control and/or regulating device 10, a control variable Y.sub.3 for activating the individual drive 3 is formed from said input signals. Said control signal is for example for a change in the pitch of the propeller and/or a change in the revolution rate and/or a change in the azimuth angle.

[0098] It is understood that all input and output variables can be signals that can be transmitted in different ways. The individual detecting devices 8 and 11 are coupled to the control and/or regulating device 10 for communications for this purpose. The coupling can be carried out directly, i.e. by means of line connections, or wirelessly. This also applies by analogy to the control devices 13 and 6.

[0099] Sensors are used as detecting devices 8 and/or 10 for example. Acceleration sensors and wave wheel sensors are used as detecting devices.

[0100] The control and/or regulating device 10 can for example be implemented as a central control unit or even as a distributed control unit, wherein the individual components are coupled together by means of a bus. In one case the control and/or regulating device 10 may only be used for the functions of setting a bollard pull and can be subordinate to or associated with a central control and/or regulating device of the tugboat 1. In the other case, the functions of the control and/or regulating device 10 are undertaken by the central control and/or regulating device for the control of the tugboat 1, i.e. the central control and/or regulating device of the tugboat forms the control and/or regulating device 10.

[0101] FIG. 2a illustrates in a schematic simplified representation the control and/or regulating device 10 and the input and output variables as well as couplings of the same to the individual components. The detecting device 8 for the detection of at least one variable at least indirectly characterizing the bollard pull and the target value specification device 7 for specifying a target value X.sub.soll for the bollard pull can be seen. Said devices are coupled to the control and/or regulating device 10, in particular a central processing unit, in particular to the inputs thereof. Said control and/or regulating device 10 is preferably the control device for the drive 3 that is present anyway, in particular the controller of the Voith-Schneider propeller for the implementation according to FIG. 1.

[0102] The control variables Y.sub.3 for activating the drives 3 in the event of a deviation between the target value and the actual value of the bollard pull are formed by means of said central processing unit and the respective control devices 13 thereof are activated.

[0103] The variables S provided by means of the detecting device 11 are processed in an analyzer that is not illustrated here or within the control and/or regulating device 10 and the theoretical changing behavior of the actual value X.sub.ist(t) of the bollard pull against time is derived therefrom and fed into the target-actual value comparison, so that the activation is carried out depending on the previously determined theoretical changing behavior.

[0104] FIG. 2b shows the regulating loop. In this the line force and hence the bollard pull function as regulating variables. A control signal Y.sub.3 to the drives 3 is produced by means of the target-actual value comparison. The adjustment performed on said control signal causes a change of the actual value X.sub.ist that is currently to be detected of the line force and hence of the alignment with the target value X.sub.soll.

[0105] Predictively taking into account the influences of the ambient conditions on the motion of the tugboat 1, and hence also on the bollard pull, is additionally provided in FIGS. 2a and 2b.

[0106] The detecting device 11 for the detection of at least one variable at least indirectly influencing the motion of the ship and/or the bollard pull is provided for this. The device 11 is used for the detection of the wave height and/or wave direction for example. The device 11 is also coupled to the control and/or regulating device 10. The analysis of said variables is incorporated into the generation of the control variable Y.sub.3 or of the control signal for the drive 3, so that the actual value again tracks the target value by activating the drive 3 or an actual value change is prevented by suitably activating the drives 3. In particular, the control devices 13 for influencing the direction of thrust and/or thrust force of the individual drive 3 are activated.

[0107] I.e., the second regulation concept is specifically overlaid onto the basic regulation here, wherein additionally the change with time X.sub.ist(t) is determined from the variables S, which were determined by the device 11 for the detection of the ambient conditions causing the change of the bollard pull, and is fed into the target-actual value comparison.

[0108] FIGS. 3a and 3b show by way of example two embodiments of tugboats 1, in which the solution according to the invention is preferably used. The drive concepts described therein are particularly well suited to the method according to the invention owing to the rapid responsiveness thereof.

[0109] The tugboat 1 according to FIG. 3a comprises two controllable drives 3, 3. Said drives are disposed on both sides of the central longitudinal plane of the tugboat 1, and indeed in the region of one end thereof. A fin 17 is disposed on the opposite end. The fin 17 is provided with a roller 18. Said roller comprises a roller drive that is not illustrated here for rotating the roller about the longitudinal axis thereof.

[0110] In the present case, the two tugboat drives 3 are Voith-Schneider propellers. Instead of this, other types of drive would also be considered.

[0111] The watercraft 1 represented in FIG. 3b again comprises two controllable drives 3, 3. Said drives are implemented as rudder propellers in the present case.

[0112] Again a rotatable roller 18 according to the invention is provided at the end of the watercraft opposite the drives of the watercraft. As can be seen, said roller is disposed exactly vertically.

[0113] Said watercraft comprises a strong bar keel, on which the roller 18 is disposed on the incident flow end.

REFERENCE CHARACTER LIST

[0114] 1 tugboat [0115] 2 cargo vessel [0116] 3 drive [0117] 4 tow line [0118] 5 cable device [0119] 6 control device [0120] 7 bollard pull target value specification device [0121] 8 detecting device [0122] 9 external influencing factors; waves [0123] 10 control and/or regulating device [0124] 11 detecting device [0125] 12 comparator [0126] 13 control device drive [0127] 14 pivoting direction of the tugboat [0128] 15 control variable generator [0129] 17 fin [0130] 18 roller [0131] X.sub.ist actual value [0132] X.sub.soll target value [0133] X deviation [0134] Y.sub.3 control variable [0135] Z pulling connection [0136] S variable, detected with device 11