US20120160143A1

US20120160143A1 - Vessel with active mechanism for controlled towing

Info

Publication number: US20120160143A1
Application number: US12/710,732
Authority: US
Inventors: Stephen L. Bailey
Original assignee: Lockheed Martin Corp
Current assignee: Lockheed Martin Corp
Priority date: 2010-02-23
Filing date: 2010-02-23
Publication date: 2012-06-28

Abstract

A vessel for towing a towed body in or on a body of water is disclosed. The vessel includes a vessel, a tow arm mechanism carried by the vessel, a towed body linked to the tow arm mechanism, and at least one sensor carried by either the vessel or the towed body. The sensor generates sensor data, and a towing mechanism controller receives the sensor data and positionally adjusts the tow arm mechanism based on the data.

Description

TECHNICAL FIELD

Generally, the present invention relates to vessels that tow sensors. Specifically, the present invention is directed to vessels that tow sensors with a towing arm that has an end that is movable so as to minimally offset a towline force vector from the vessel's center of gravity. In particular, the present invention is directed to vessels that tow sensors wherein the vessel and/or towed body is provided with a motion and position sensor to detect changes in the towline force vector so as to actively move the towing arm to compensate for those changes.

BACKGROUND

Various types of sensors are utilized for evaluations of bodies of water. These sensors can be used for seismic surveys, sea floor mapping, and environmental and coastal surface surveys. These sensors can also be used to detect underwater conditions for military purposes such as for surveillance, the detection of mines and/or other submerged vehicles.
One method is to tow a sensor from an aircraft such as a helicopter or an appropriate vessel. Towing sensors from surface vessels provide a low cost advantage over an airborne-towed sensor. Vessels that tow sensors are fairly easily deployed, can be remotely controlled and are easily retrieved for review of the detected information.
Although use of towed sensors is advantageous, use of a vessel to tow a sensor has certain drawbacks. It is known that small craft used to tow sensors have difficulty in controlling the impact of the towing vessel's motions on a towed sensor and also conversely, the impact of the towed sensor's forces on the attitude of the towing craft are encountered. In prior art small craft monohull vessels, a transom winch on an A-frame mounted on the stern is used to place a tow point above and behind the vessel. This tow point location away from the vessel's center of gravity allows vessel pitch motion to be transmitted to the tow line tension and this results in unwanted sensor motion. And the distance of the tow point from the vessel's center of gravity and the resulting couple motions of pitch and heave, and towing from an A-frame also imposes higher forces on the towed body, thereby degrading its motion performance. Towing from an A-frame also creates a pitching motion or moment on the towing vessel, due to the towing force vector offset above the thrust line of the towing vessel's propulsors. It also generates a force vector significantly away from the towing vessel's center of gravity, thereby imposing moments that are deleterious to the vessel's performance. Moreover, the tension from the drag of the sensor and tow line, in turn, adds to the vessel trim and roll angles. Vessel maneuvering and the resulting off-axis forces also add a yaw moment. Adding trim to a vessel adds to its resistance. Adding roll and yaw moment to a vessel impacts on-board equipment performance and hinders the ability to control the vessel. Minimizing the towing forces on the towed body also becomes critical particularly as the size of the vessel becomes small relative to the size of the towed body. In addition, the sensor is exposed to transverse currents, waves and wind forces which further contribute to the deleterious forces imparted on the vessel. These forces also provide extra wear on the tether connecting the vessel to the towed sensor.
In summary, prior art small craft vessels that tow a sensor usually do so from a non-optimal fixed point and such small craft have no way of adjusting the fixed point to accommodate operational characteristic of the vessel or environmental characteristics that are encountered while towing the sensor. Indeed, a towed sensor that is exposed to extraneous forces interferes with the main purpose of the sensor in collecting data. In other words, if a sensor is not maintained in a steady and uniform path, its ability to collect data regarding mine positions or mapping of sea floor characteristics is significantly reduced.
Therefore, there is a need in the art for a vessel that tows a sensor or towed body wherein a tow arm mechanism is actively maintained to minimize deleterious forces on the vessel and the towed body. There is also a need to provide a tow arm mechanism that controls the tow line tensile vector by a mechanism that allows the vector to be directed through an optimum point in relation to the towing craft. Moreover, there is a need for vectoring the force through the center of gravity of the vessel so as to eliminate the induced trim, roll and yaw moments. By vectoring the force through the thrust line of the propulsion of the vessel, such a configuration eliminates the induced trim of the vessel and allows it to operate more efficiently. And there is a need in the art for controlling the tow line tensile vector when the ratio of tow force to vessel displacement becomes large. There is also a need to provide sensors on board the vessel and the towed body to provide positional and motion input that is processed and delivered to a controller for the tow arm mechanism.

SUMMARY OF THE INVENTION

In light of the foregoing, it is a first aspect of the present invention to provide a vessel with active mechanism for controlled towing.
It is another aspect of the present invention to provide a vessel for towing a towed body in or on a body of water, comprising a vessel, a tow arm mechanism carried by the vessel, a towed body linked to the tow arm mechanism, at least one sensor carried by either the vessel or the towed body, the at least one sensor generating sensor data, and a towing mechanism controller receiving the sensor data and positionally adjusting the tow arm mechanism based on the data.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings wherein:

FIG. 1 is a rear side perspective view of a vessel with an active mechanism for controlled towing according to the present invention showing a towed body in a retained position;

FIG. 2 is a rear perspective view of the vessel according to the present invention with the towed body shown in a deployed position;

FIG. 3 is an elevational view, partially broken away, of the vessel according to the present invention showing a tow arm mechanism in various operational positions; and

FIG. 4 is a schematic diagram of a tow arm control system employed by the vessel according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring now to the drawings and particularly to FIGS. 1-3, it can be seen that a vessel with an active mechanism and a controlled towing system is designated generally by the numeral 10. The system 10 includes a vessel 12 which may be any kind of water-borne craft. In most embodiments of the present invention the craft is a relatively small motorized craft, but the concepts of the present invention can be employed with any type of towing vessel. The vessel 12 carries a vessel position and motion sensor 14 which monitors the position speed, pitch, yaw, roll and other operational characteristics of the vessel. The data collected by the sensor 14 is transmitted via a data line 16. In some embodiments the sensor 14 may wirelessly transmit data associated with or collected by the sensor 14. The vessel 12 includes a cabin 18 which houses various instruments and control systems for operating the vessel 12. In some embodiments the cabin may accommodate personnel and in other embodiments the cabin may be configured for remote control from other ships, or land-based or air-based control systems.
A tow mechanism controller 20 is maintained by the vessel and most likely maintained within the cabin 18. Generally, the tow mechanism controller 20 receives data, such as sensor information from data line 16 and generates control signals 22. The control signals 22 may comprise any number of control signals needed to implement the objects of the invention.
The vessel 12 is a multi-hull vessel and, as such, provides a starboard hull 24 and a port hull 26. The spacing between the hulls 24, 26 form a moonpool-like opening 28 therebetween. Although the present invention can be employed with any type of water-borne craft as described above, it is believed that a dual hull configuration as shown and described herein provides a number of additional benefits that will be discussed. In any event, the starboard hull 24 maintains a starboard propulsor 30 and, in a similar manner, the port hull 26 maintains a port propulsor 32. In the alternative, the hulls may carry other means for propulsion, such as propellers and the like. Each propulsor 30/32 has associated therewith a thrust sensor 33. Each thrust sensor 33 measures the current propulsor thrust and generates propulsor data 34 that is sent or transmitted to the tow mechanism controller 20.
A tow arm mechanism is designated generally by the numeral 50 and mounted proximal the cabin 18 and fore of a cradle 51. The tow arm mechanism carries a towed body 52 such as SONAR or other type of sensor utilized to observe a phenomenon or feature maintained in the body of water under examination. The cradle 51, as shown in FIG. 1, carries the towed body 52 as the vessel moves to the area to be surveyed. As seen in FIG. 2, the cradle 51 is lowered at one end to deploy the towed body 52. Data collected by the towed body may be stored for later retrieval or transmitted to an appropriate receiver. The towed body 52 includes a towed body position and motion sensor 54 which generates motion data 56 that is transmitted to the tow mechanism controller 20. In much the same manner as the vessel position and motion sensor 14, the towed body position and motion sensor 54 generates information related to the forces applied to the towed body during deployment and operation of the vessel 12. In other words, as the towed body 52 is pulled by the vessel 12, the body 52 experiences any number of forces that are detected by the sensor 54 and transmitted to the controller 20 for processing.
The tow arm mechanism 50 includes a pair of opposed buttress plates 60 wherein each plate 60 is carried by the vessel on each side of the moonpool opening. The buttress plates 60 carry the tow arm mechanism 50 and related components as will be described below. Carried between the buttress plates 60 is a winch 62 which comprises a rotatable cylindrical drum. An arm 64, which is pivotable in various directions, is carried by the vessel and mounted between the buttress plates 60. A tow line 66 is carried by the winch and wound around its cylindrical drum. The tow line 66 interconnects the towed body 52 to the vessel 12. The tow line 66 is constructed of a strong flexible material which may simply carry the towed body or in some embodiments may incorporate communication cables to as to transmit information between the vessel and the towed body. In some embodiments, the data may be transmitted wirelessly from the towed body to the vessel or transmitted to other ships located in the area of the vessel 12. The tow line 66 may also be directly connected to the tow mechanism controller 20 such that information data 56 transmitted by the towed body position and motion sensor 54 provides real-time information to the controller 20.
A winch motor 68 is coupled to the winch 62 and reels the tow line 66 in and pays it out as needed. The winch motor 68 receives a winch motor control signal 70 from the tow mechanism controller 20. A winch motor sensor 72 is coupled to the winch motor 68 and detects torque forces applied to the tow line during deployment and operation. The sensor 72 generates winch motor data 74 which is transmitted to the tow mechanism controller 20. The tow line 66 is also monitored by a tow line quantity sensor 76 mounted proximally to the winch 62 so as to detect the length of the tow line deployed during operation. The quantity sensor generates a data signal 77 which is transmitted to the tow mechanism controller 20.
A tow arm axle 80 is mounted between the buttress plates 60 and is rotatable by a tow arm axis motor 82 which rotates the axle. The arm 64 is secured to the axle 80 and, as a result, the tow arm 64 is movable into the desired angular positions. In an alternative embodiment, the axle 80 could be fixed to the plates 60 and the arm 64 pivots with respect to the axis. Other interconnections between the tow arm 64 and the axle 80 and/or vessel 12 could be employed. Examples of the various positions can best be seen in FIG. 3. The tow arm axis motor 82 receives a tow arm control signal 84 from the tow mechanism controller so as to adjust the angular position of the tow arm as needed. A tow arm sensor 86 is coupled to the axle 80 so as to detect the rotational position of the axle and, as such, the angular position of the tow arm. The sensor 86 generates axis data 88 which is sent to the tow arm controller 20 for monitoring of the tow arm position and adjustments as needed.
Included in the tow arm mechanism 50 is a lateral mover 90 which may be mounted on the tow arm axle 80. The mover 90 moves the arm 64 side to side along the length of the axle 80 based upon a lateral mover control signal 92 generated by the tow mechanism controller 20. In order to ensure proper operation of the lateral mover 98, a lateral mover sensor 94 may be associated therewith and generates lateral mover data 96 that is transmitted to the controller 20. In some embodiments, lateral movement of the arm 64 may be obtained by moving the buttress plates 60 or some other mechanical configuration as deemed appropriate.
The arm 64 includes a pair of flanges 102 spaced apart from each other and are of a generally similar construction. The arm 64 includes an axle end 104 which is mounted upon the tow arm axle 80. At an end opposite the axle end 104, the flanges 102 provide an elbow 106. Angularly extending from the elbow 106 is a hook end 108 which terminates the flanges 102. The flanges 102 are separated but connected to one another by a number of sheaves. Specifically, an axle sheave 110 is maintained near or on the axle end 104. Indeed, the axle sheave 110 is mounted on the axle 80 and separates the flanges 102 from one another. An elbow sheave 112 is maintained at the elbow 106 and a hook sheave 114 is maintained at the hook end 108. As skilled artisans will appreciate, the sheaves 110/112/114 are rotatable members with a grooved central portion which accommodates the diameter of the tow line 66. Together, the elbow sheave 112, the hook sheave 114 and the flanges 102 form a tow line opening 116 such that the outer diameter of the tow line fits within and easily moves along the respective grooves and is routed or threaded between and through the opening 116 so as to direct movement of the tow line and the towed body. As best seen in FIG. 3, when the tow arm is in an upward angular position, such as when the towed body is in a retained position, the tow line is primarily supported by the elbow sheave 112. As the arm 64 is lowered into a position to deploy the towed body, the tow line is supported by the axle sheave 110, the elbow sheave 112 and hook sheave 114. In some instances the hook end 108 may be lowered beneath the water line supporting the vessel 12 and as a result the tow line is primarily directed by the hook sheave 114 and supported by the elbow sheave 112 and axle sheave 110.
In some embodiments, a hook sheave sensor 118 may be mounted to the hook sheave 114 and generates sensor data 120 that is transmitted to the tow mechanism controller 20. The hook sheave sensor determines a magnitude vector of the tow force and forces applied to the tow line 66.
As best seen in FIG. 3, the vessel provides a propulsor level base line 122 which is essentially the water line that supports the vessel 12. The vessel also provides a center of gravity 124 which is used to reference the position of the tow arm as will be described.
Overall operation of the tow arm mechanism 50 is maintained by a tow arm control system designated generally by the numeral 126 as shown in FIG. 4. User input 128 is provided to the control system 126 and specifically to the tow mechanism controller 20. User input 128 may also be provided to the propulsors 30/32 so as to control the speed of the vessel and, it will also be appreciated that user input is provided to a steering mechanism that controls the maneuverability and direction of the vessel. Along with receiving user input, the tow mechanism controller 20 receives position and motion data 16/56 from the sensors 14 and 54 which directly monitor the forces being applied to the towed body and the vessel. Other inputs received by the tow mechanism controller include the data related to the thrust sensors 33, the hook sheave sensor 118, the tow line quantity sensor 76, the tow arm sensor 86, the lateral sensor 94 and the winch sensor 72. Based upon these various inputs that the tow mechanism controller receives, which monitor the operation of the tow mechanism, the vessel 12 and the towed body, the tow mechanism generates control signals 22 -- such as the tow arm axis motor signal 84, the lateral mover motor signal 92, and the winch motor signal 70 -- so as to adjust the position of the tow arm and provide for improved operation of the towed body and the vessel. In other words, as various forces impact the towed body and the vessel, the controller selectively adjusts the angular position of the arm, the lateral position of the arm and/or the tension force applied by the winch motor to the tow line. For example, as the vessel begins a turning maneuver, the vessel sensor 14 and the towed body sensor 54 detect the various changes in forces applied to the towed body and the sensor. The controller 20 receives these changes and generates control signals 22 to adjust the component forces exerted on the tow line by the tow arm axis motor 82, the lateral mover motor 90 and/or the winch motor 68. Forces detected by the other sensors 118, 76, 86, 94, 72 and 33 can also be used to determine the extent and nature of the control signals generated. As the controller 20 and the system 126 gain experience, the control signals can be collectively generated to provide for optimum operation of the vessel 12 and/or optimum data collection for the towed body. As a result, the controller 20 provides enhanced control during normal running conditions including maneuvers.
By utilizing the control system 126, operation of the controller 20 actively controls the arm 64 in both the vertical and lateral planes relative to the vessel 12. For example, with the object being towed via the tow line, the end of the tow arm is controlled, which allows the vector of the towline tensile force to be controlled. Controlling the towline tensile vector allows the force to be extrapolated through the center of gravity of the vessel, the thrust vector or some other optimum point of the tow vessel. The tow point can be therefore controlled via the controller 20 or with the assistance of a human or automated control system, or remotely operated by a link associated with the vessel or some combination thereof to actively control the inter relationship between the towed object and the towing vessel.
Utilization of system 10 with the control system 126 which incorporates the controller 20 provides a number of advantages. First, towing a body from a multi hull vessel provides greater flexibility for controlling the tow point to reduce deleterious effects through the opening 28 between the multiple hulls both laterally and longitudinally on the craft. In other words, by utilizing an active mechanism for controlling the position of the tow vector, it will be appreciated that its path is positionable through or very close to the center of gravity of the vessel, or through the thrust vector of the propulsor or some optimal position of compromise between the two. Still other advantages are realized in that towing of a towed body 52 in areas of high sea states dictates a preference for the towing vessel to be a multi hull configuration due to its superior sea keeping and sea-kindliness. This improved sea keeping reduces the towing vessel's motion which, in turn, reduces the imposed motions on the towed body. Improved sea keeping also improves the effectiveness of the controlling and gathering of information from the towed body in the case of a manned vessel, or improves the ability to control through improved remote sensing capabilities in case of an unmanned tow vessel. Additionally, use of multi hulls allows for faster transit time to the area of interest for the sensor in tow.
Other advantages are realized by actively controlling the tow point position in space minimized the induced motion on the towed body and towing vessel. As a result, the tow line can be controlled at an elevation so that the tow line does not contact the hull or propulsors which in turn increases the life and reliability of the tow line. Still another advantage is that controlling the tow force vector through the towing vessel propulsor thrust line reduces induced hull drag and minimizes the size of the propulsion motors, particularly when the towing vessel size is smaller in proportion to the size of the towed objects.
Thus, it can be seen that the objects of the invention have been satisfied by the structure and its method for use presented above. While in accordance with the Patent Statutes, only the best mode and preferred embodiment has been presented and described in detail, it is to be understood that the invention is not limited thereto or thereby. Accordingly, for an appreciation of the true scope and breadth of the invention, reference should be made to the following claims.

Claims

1. A vessel for towing a towed body in or on a body of water, comprising:

a vessel;

a tow arm mechanism carried by said vessel;

a towed body linked to said tow arm mechanism;

at least one sensor carried by either said vessel or said towed body, said at least one sensor generating sensor data; and

a towing mechanism controller receiving said sensor data and positionally adjusting said tow arm mechanism based on said data.

2. The vessel according to claim 1, wherein said tow arm mechanism comprises:

a winch which carries a tow line, wherein one end of said tow line is connected to said towed body; and

an arm pivotably carried by said vessel, wherein said arm moves said tow line to a position proximal in line with said vessel's center of gravity.

3. The vessel according to claim 2, wherein said towing mechanism controller adjusts a position of said arm based on said sensor data.

4. The vessel according to claim 3, wherein said tow arm mechanism further comprises:

an opposed pair of buttress places, wherein said winch is mounted between said buttress plates;

a frame axle mounted between said buttress plates, wherein one end of said arm is mounted on said axle; and

an axle motor rotatably moving said frame axle so as to pivotably move said arm, said axle motor receiving an axle control signal from said towing mechanism controller to pivotably move said arm based on data from said at least one sensor received by said towing mechanism controller.

5. The vessel according to claim 4, further comprising:

an axle sensor coupled to said frame axle to detect an angular position and send said angular position to said towing mechanism controller.

6. The vessel according to claim 4, wherein said tow arm mechanism further comprises:

a lateral mover motor laterally moving said arm, said lateral mover motor receiving a lateral mover control signal from said towing mechanism controller to laterally move said arm in relation to said axle based on data from said at least one sensor received by said towing mechanism controller.

7. The vessel according to claim 4, wherein said tow arm mechanism further comprises:

a winch motor coupled to said winch to pay out and reel in said tow line, said winch motor receiving a winch control signal from said towing mechanism controller to adjust tension on said tow line based on data from said at least one sensor received by said towing mechanism controller.

8. The vessel according to claim 4, wherein said vessel comprises a starboard hull and a port hull spaced apart from one another and forming a moonpool opening therebetween, each said hull having a propulsor associated therewith, and wherein said arm has an end opposite said axle that is extendable into said moonpool opening.

9. The vessel according to claim 8, further comprising:

a thrust sensor associated with each said propulsor, said thrust sensor detecting thrust forces generated by said propulsors and sending propulsor data to said towing mechanism controller.

10. The vessel according to claim 4, wherein said towed body carries a motion and position sensor that sends motion data to said towing mechanism controller.

11. The vessel according to claim 10, wherein said motion and position data is sent along said tow line.

12. The vessel according to claim 4, wherein said arm comprises a pair of spaced apart flanges each having an axle end rotatably mounted on said frame axle, each said flange extending from said axle end to an elbow from which angularly extends a hook end.

13. The vessel according to claim 12, further comprising a plurality of sheaves disposed between said flanges at said axle end, said elbow and said hook end and guiding said tow line as said arm pivots to different angular positions.