Abstract:
An attitude and roll stabilizer for towed undersea vehicles includes a vertical joining rod having an upper end and a lower end, a roll control weight mounted to the lower end of the vertical joining rod, an attitude control surface mounted to the upper end of the vertical joining rod, a tow rod pivotally mounted transverse to the vertical joining rod, an actuator member connected to the vertical joining rod between the tow rod and the roll control weight, and a connecting bar connecting the actuator adjacent to the aft end of the tow rod. A change in tow speed of the towed vehicle selectively pivots the tow rod about the vertical joining rod, and is correspondingly compensated for with a counteractive pitching of the attitude control surface and the roll control weight, thereby maintaining the level of the towed vehicle at the altered speed.

Description:
STATEMENT OF GOVERNMENT INTEREST 
     The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor. 
     BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     This invention generally relates to an attitude and roll stabilizer for towed undersea devices. More particularly, the invention relates to an attitude and roll stabilizer for towed undersea devices in which the undersea devices may be towed at varying speeds. 
     (2) Description of the Prior Art 
     The current art for attitude and roll stabilization of underwater vehicles has not in the past been directed to towing of the underwater device at varying speeds while controlling roll and pitch in an economical manner. Thus, a problem exists in the art whereby there is a need to control the roll and pitch of underwater vehicles being towed at varying speeds. The following patents, for example, disclose various types of deflectors for underwater vehicle control, but do not disclose a complete similarity with either the hardware or function of the attitude and roll stabilizer for towed undersea devices as set forth in connection with the disclosure of the present invention. 
     U.S. Pat. No. 5,357,892 to Vatne et al.; 
     U.S. Pat. No. 4,991,534 to Warman et al.; 
     U.S. Pat. No. 4,843,996 to Darche; and 
     U.S. Pat. No. 3,460,384 to Fohl. 
     Vatne et al. disclose a deflector for installation in the tow line between a towing vessel and a tow which is located in the water. A cable with seismic sources, or a seismic source array, is suspended by a float and has a fitting therefrom having a tow-point near the front part of the deflector connected to the tow line, and an attachment point to the rear of the deflector-for further connection thereto for the rear part of the tow line connected to the two. In order to be able to locate the deflector in a desired position in relation to the towing vessel and compensate for alternations in the effects of forces from the tow or vessel in addition to movements in the water, the tow line which leads on to the actual tow from the deflector body is attached to the deflector via a pivotable lever which is situated at the same height as the lifting force center of the deflector body. The tow point of the tow line body is provided at one lateral surface of the deflector body in front of the vertical center line thereof. An additional deflector wing may be incorporated in the rear part of the tow line. Accordingly, Vatne et al. describe a deflective device with the primary function of avoiding towing an object or different types of equipment directly behind the towing vessel. This device is very different in both hardware and function and, unlike the attitude and roll stabilizer for towed undersea devices of the present invention, it appears to be limited to shallow depth applications. Also, unlike the attitude and roll stabilizer for towed undersea devices according to the present invention, this prior art has no opportunity for electronic control. 
     The patent to Warman et al. discloses a depressor designed to keep a fish, towed by a ship, submerged and includes a flat swept wing joined to the towing cable by means of three suspenders making it possible to set it as an optimal angle of incidence. This enables a fish to be towed at a high speed which may go up to 30 knots while, at the same time, keeping it at a substantially constant depth of submersion. Accordingly, the device of Warman et al. is very different in both design and function and, unlike the attitude and roll stabilizer for towed undersea devices, does not provide roll stability to the towed device. Also, there is no electronic control capability. 
     The patent to Darche discloses a system, which is of the type comprising at the end of a primary cable, a first fish to which is connected a secondary cable towed by a second fish. There are provided, in proximity to the first fish, apparatus for measuring the angle between the direction of the relative current and the vertical plane passing through the secondary cable, and apparatus for measuring the angle of inclination of the secondary cable to the horizontal, connected to apparatus for automatically steering the second fish so as to bring the angles to predetermined values. Accordingly, Darche is simply directed to a device that maintains depth control of submerged devices that principally deploy forward of the tow surface craft. This device employs a forward and aft fish. The stability of the forward fish is dependent upon a propulsive capability of such forward fish, which derives electronic control from the aft fish. This device is very different in both design and function and, unlike the attitude and roll stabilizer for towed undersea devices according to the present invention, does not couple roll stability to the device under tow. 
     Fohl describes a mechanical depth-controlling device that is towed by a surface ship. In particular, the depth control device includes an adjustable boundary layer control coating with a liquid contacting surface of the structure. This device is very different in both hardware and function and, unlike the attitude and roll stabilizer for towed undersea devices of the present invention, does not couple roll stability to the device under tow. Furthermore, maintaining depth with any degree of accuracy appears to be difficult as the speed varies. 
     Accordingly, this invention is the result of being posed with the problem of using a surface craft to tow an underwater device at varying speeds and to stabilize the device in roll and pitch by the most economical means. This invention replaces the need for a complex and expensive stabilization control system. 
     It should be understood that the present invention would in fact enhance the functionality of the above patents by providing pitch and roll stabilization for underwater vehicles towed at varying speeds in a manner not previously known in the art. 
     SUMMARY OF THE INVENTION 
     Therefore it is an object of this invention to provide an attitude and roll stabilizer for underwater vehicles. 
     Another object of this invention is to provide an attitude and roll stabilizer for underwater vehicles which is applicable to vehicles being towed at varying speeds. 
     Still another object of this invention is to provide an attitude and roll stabilizer for underwater vehicles which is an active attitude and roll stabilizer. 
     A still further object of the invention is to provide an attitude and roll stabilizer for underwater vehicles which is a passive attitude and roll stabilizer. 
     Yet another object of this invention is to provide an attitude and roll stabilizer for towed undersea devices which is simple to manufacture and easy to use. 
     In accordance with one aspect of this invention, there is provided an attitude and roll stabilizer for towed undersea vehicles which includes a vertical joining rod having an upper end and a lower end, a roll control weight mounted to the lower end of the vertical joining rod, an attitude control surface mounted to the upper end of the vertical joining rod, a tow rod pivotally mounted transverse to the vertical joining rod, an actuator member connected to the vertical joining rod between the tow rod and the roll control weight, and a connecting bar connecting the actuator adjacent to the aft end of the tow rod. A change in tow speed of the towed vehicle selectively pivots the tow rod about the vertical joining rod, and is correspondingly compensated for with a counteractive pitching of the attitude control surface and the roll control weight, thereby leveling the towed vehicle at the altered speed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The appended claims particularly point out and distinctly claim the subject matter of this invention. The various objects, advantages and novel features of this invention will be more fully apparent from a reading of the following detailed description in conjunction with the accompanying drawings in which like reference numerals refer to like parts, and in which: 
     FIG. 1 is a side plan view of a first preferred embodiment of the present invention having an active attitude and roll stabilizer for a towed undersea vehicle; 
     FIG. 2 is a side detailed view of the attitude and roll stabilizer per se of FIG. 1; 
     FIG. 3 is a side plan view of a second preferred embodiment of the present invention having a passive attitude and roll stabilizer for a towed undersea vehicle; 
     FIG. 4 is a detailed side view of the attitude and roll stabilizer per se of FIG. 3; and 
     FIGS. 5A,  5 B, and  5 C are side views of wing shapes for use in connection with either the first or second embodiments of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In general, the present invention is directed to an attitude and roll stabilization device for a towed undersea vehicle. 
     By way of explanation, the principle advantages of the following disclosure in connection with the inventive attitude and roll stabilizer of the present invention are simplicity and cost. The stabilizer has a broad range of applications for both military and commercial use. Also, the stabilizer can be configured to operate either passively or actively for attitude stabilization. 
     Referring first to FIGS. 1 and 2, there is shown an active attitude and roll stabilizer for a towed unmanned undersea vehicle with FIG. 1 illustrating the entire system and FIG. 2 illustrating the stabilizer per se. For the purposes of description and reference to the various parts of the figures, the towing vehicle is identified by reference number  10  and the towed vehicle is at  12 . An inventive stabilizer  14  is connected to the towed vehicle  12  and a tow cable  16  connects a fore end of the stabilizer  14  to an aft end of the towing vehicle  10 . It should be understood that towing occurs in the direction of the fore end of the towing vehicle  10 . 
     Turning now to the detail of FIG. 2, the details of the stabilizer  14  are shown. In particular, the stabilizer of FIG. 2 is an active attitude and roll stabilizer for towed undersea vehicles  12 . As shown, the undersea vehicle  12  is unmanned, but may be manned according to environment and necessity. The stabilizer is constructed of a vertical joining rod  18  having an upper end  18   a  and a lower end  18   b . At the upper end  18   a  of the stabilizer  18  is mounted an attitude control surface  20  formed in the shape of a foil. At the lower end  18   b  of the stabilizer  18  is a roll control weight  22 . Roll compensation is achieved by the roll control weight  22  being located below the unmanned undersea vehicle&#39;s  12  center of buoyancy and center of gravity. 
     Approximately one-third of the distance from the upper end  18   a  to the lower end  18   b  of the vertical joining rod  18  is a transverse tow rod  24 . The tow rod  24  is connected to the vertical joining rod  18  by a known connection  26  such as a bolt or the like which permits pivoting of the tow rod  24  with respect to the vertical joining rod  18 . A tow eye  28  is connected to a fore end  24   a  of the tow rod  24 . The tow eye  28  may be connected in a fixed manner by any suitable means such as welding or the like to the fore end  24   a  of the tow rod  24 . The tow cable  16  is looped through or connected to the tow eye  28  and connects to the towing vehicle in any suitable manner as described above. 
     At an aft end  24   b  of the tow rod  24 , a connector  30  is provided which connects the tow rod  24  and hence the stabilizer  14  to the towed vehicle  12 . The connector  30  may include an opening for a separate tow cable or may otherwise be securely fixed to the towed vehicle  12 . In any event the connection of the connector  30  to the towed vehicle  12  should be strain free so that the towed vehicle  12  is easily attached and detached, perhaps while in an underwater environment. 
     Below the tow rod  24  and on the vertical joining rod  18 , there is mounted an actuator member  32 . The actuator member  32  includes a fore end  32   a  and an aft end  32   b . The actuator member is pivotally connected at the fore end  32   a  thereof to the vertical joining rod  18 . The actuator  32  is connected to the tow rod  24  by a connecting bar  34  spanning the distance from the actuator  32  aft end  32   b  to the tow rod  24 . More specifically, the actuator  32  is electrically driven such that the actuator  32  automatically compensates for deviation of the stabilizer  14  from a programmed depth or from a distance from the bottom surface (not shown) of the body of water  36 . As a tow speed of the towed vehicle  12  increases, an upward force on the tow eye  28  will cause the towed vehicle  12  to climb, resulting in a variance from the programmed depth as described. A depth sensor. and controller  38  incorporated into the actuator  32  will respond by sending an appropriate signal voltage to the actuator  32 . In the event that the speed increases, causing a rise in the towed vehicle, the actuator  32  pulls on the vertical joining rod  18  causing the attitude control surface  20  to pitch forward resulting in a downward deflection force of the entire stabilizer  14 . With the attitude control surface  20  pitching forward as tow speed is increasing and thereby increasing the downward deflection force of the stabilizer  14 , a compensation of the increasing upward force at the tow eye  28  occurs. 
     It should be noted that the depth sensor and depth controller can be located in the unmanned undersea vehicle  12 . 
     Also, power for the actuator  32  and the depth sensor and controller  38  can be provided either from the unmanned undersea vehicle  12  or from the towing vehicle  10  via the tow cable  16 . 
     The stabilizer  14  is configured to match the requirements for the towing vehicle  10 , the towed vehicle  12  and the tow speed. 
     In particular, the roll control weight  22  is appropriately sized to the towed vehicle  12  to achieve the desired roll stability. Also, the attitude control plane  20  is appropriately sized to the towed vehicle  12  to achieve the desired attitude control. Furthermore, the location of the pivot point  26  on the vertical joining rod  18  and the length of the vertical joining rod  18  are appropriately sized to the towed vehicle  12  to achieve desired attitude control. In addition the attitude control plane&#39;s  20  shape is tailored to the buoyancy of the towed vehicle  12 . Possible configurations of the attitude and roll stabilizer  20  are shown in further detail in FIGS. 5A-5C and are applicable to either of the disclosed embodiments. This would include shapes such as a foil in FIG.  5 A and the embodiments of FIGS. 2 and 4, a wing in FIG. 5B, or an inverted wing in FIG. 5C depending on whether the towed vehicle is neutrally buoyant, negatively buoyant, or positively buoyant, respectively. 
     Turning now to the second embodiment shown in FIGS. 3 and 4, a passive attitude and roll stabilizer will be described. In general, the basic components of the passive attitude and roll stabilizer are the same as that shown in FIG. 1, but will be described with separate reference numerals to differentiate from the first embodiment. 
     Referring to FIGS. 3 and 4, there is shown a passive attitude and roll stabilizer for a towed unmanned undersea vehicle with FIG. 3 illustrating the entire system and FIG. 4 illustrating the stabilizer per se. For the purposes of description and reference to the various parts of the figures, the towing vehicle is identified by reference number  40  and the towed vehicle is at  42 . An inventive stabilizer  44  is connected to the towed vehicle  42  and a tow cable  46  connects a fore end of the stabilizer  44  to an aft end of the towing vehicle  40 . It should be understood that towing occurs in the direction of the fore end of the towing vehicle  40  through the water  66 . 
     Turning now to the detail of FIG. 4, the details of the stabilizer  44  are shown. In particular, the stabilizer of FIG. 4 is a passive attitude and roll stabilizer for towed undersea vehicles  42 . As shown, the undersea vehicle  42  is unmanned, but may be manned according to environment and necessity. The stabilizer  44  is constructed of a vertical joining rod  48  having an upper end  48   a  and a lower end  48   b . At the upper end  48   a  of the stabilizer  48  is mounted an attitude control surface  50  formed in the shape of a foil. At the lower end  48   b  of the stabilizer  48  is a roll control weight  52 . Roll compensation is achieved by the roll control weight  52  being located below the center of buoyancy and center of gravity of the towed vehicle  42 . 
     Approximately one-third of the distance from the upper end  48   a  to the lower end  48   b  of the vertical joining rod  48  is a transverse tow rod  54 . The tow rod  54  is connected to the vertical joining rod  48  by a known connection  56  such as a bolt or the like which permits pivoting of the tow rod  54  with respect to the vertical joining rod  48 . A tow eye  58  is connected to a fore end  54   a  of the tow rod  54 . The tow eye  58  may be connected in a fixed manner by any suitable means such as welding or the like to the fore end  54   a  of the tow rod  54 . The tow cable  46  is looped through or connected to the tow eye  58  and connects to the towing vehicle  40  in any suitable manner as described above. 
     At an aft end  54   b  of the tow rod  54 , a connector  60  is provided which connects the tow rod  54  and hence the stabilizer  44  to the towed vehicle  42 . The connector  60  may include an opening for a separate tow cable or may otherwise be securely fixed to the towed vehicle  42 . In any event, the connection of the connector  60  to the towed vehicle  42  should be strain free so that the towed vehicle  42  is easily attached and detached, perhaps even while in an underwater environment. 
     Below the tow rod  54  and on the vertical joining rod  48 , there is mounted an adjustable spring mechanism  62 . The adjustable spring mechanism  62  includes a fore end  62   a  and an aft end  62   b . The adjustable spring mechanism  62  is fixedly connected at the fore end  62   a  thereof to the vertical joining rod  48 . The adjustable spring mechanism  62  is connected to the tow rod  54  by a connecting bar  64  spanning the distance from the aft end  62   b  of the adjustable spring mechanism  62  to the tow rod  54 . More specifically, the adjustable spring mechanism  62  is mechanically actuated such that the adjustable spring mechanism  62  will automatically compensate for deviation of the stabilizer  44  from a linear tow path during a towing operation. As a tow speed of the towed vehicle  42  increases, an upward force on the tow eye  58  will cause the towed vehicle  42  to climb resulting in a variance from the linear tow path as described and causing the aft end  54   b  of the tow rod  54  to tilt upward relative to vertical joining rod  48 . In the event that tow speed of the towed vehicle  42  increases, causing a rise in the towed vehicle  42 , the adjustable spring mechanism  62  pulls on the vertical joining rod  48  causing the attitude control surface  50  to pitch forward resulting in a downward deflection force of the entire stabilizer  44 . With the attitude control surface  50  pitching forward as tow speed is increasing and thereby increasing the downward deflection force of the stabilizer  44 , a compensation of the increasing upward force at the tow eye  58  occurs. 
     Thus, for passive operation, as a towed speed of the towed vehicle  42  increases, the upward force at the tow eye  58  is counteracted by a downward force created by the attitude control plane  50 . 
     Once again, the roll control weight is appropriately sized to the towed vehicle  42  to achieve the desired roll stability. Also, the attitude control plane  50  is appropriately sized to the towed vehicle  42  to achieve the desired attitude control. Furthermore, the location of the pivot point  56  on the vertical joining rod  48  and the length of the vertical joining rod  48  are appropriately sized to the towed vehicle  42  to achieve desired attitude control. In addition the shape of the attitude control plane  50  is tailored to the buoyancy of the towed vehicle  42 , including the shapes in FIGS. 5A,  5 B and  5 C as noted previously. 
     It will be understood that alternatives to the described devices are inherent within the above descriptions. For example, the device can be configured to operate either passively or actively. Furthermore, the roll control weight is appropriately sized to the tow body to achieve the desired roll stability. Also, the attitude control plane is appropriately sized to the tow body to achieve desired attitude control. In addition, the attitude control plane&#39;s shape is tailored to the buoyancy of the tow vehicle. This would include shapes such as a foil, a wing, or an inverted wing depending on whether the tow body is neutrally buoyant, negatively buoyant, or positively buoyant, respectively. 
     The principal advantages are simplicity and costs. The stabilizer has a broad range of applications for both military and commercial use. Also, the stabilizer can be configured to operate either passively or actively for attitude stabilization. Further, it is anticipated that the invention herein will have far reaching applications other than those of underwater vehicles. 
     This invention has been disclosed in terms of certain embodiments. It will be apparent that many modifications can be made to the disclosed apparatus without departing from the invention. Therefore, it is the intent of the appended claims to cover all such variations and modifications as come within the true spirit and scope of this invention.