Patent Publication Number: US-2012042821-A1

Title: Underwater assemblies with flooded actuators and methods for using same

Description:
RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 12/348,956, filed Jan. 6, 2009, which claims priority from U.S. Provisional Patent Application Ser. No. 61/019,668, filed Jan. 8, 2009, the disclosure of which is hereby incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to underwater devices, and more specifically to underwater devices with movable members. 
     BACKGROUND OF THE INVENTION 
     Many submersible vehicles are constructed with actuators mounted inside the pressure hull of the vehicle because they are otherwise easily damaged by water. These existing actuators typically have a mechanical linkage, the motion of which imparts a force or torque on an externally mounted control fin or similar member as means of steering or propulsion. Except in critical cases, where oil-backed seals are used, water is typically excluded by a dynamic seal providing a friction fit against the linkage. “Friction fit” is defined herein as a linkage-seal interaction wherein motion of the linkage with respect to the seal causes friction owing to forceful contact between them. 
     A friction fit can cause problems, including abrasion, lockup and energy loss. “Abrasion” is defined herein as loss of material from the seal or shaft, producing a change in friction fit. “Lockup” is defined herein as link immobility with respect to the hull. “Energy loss” is defined herein as the energy required to combat friction or viscous or viscoelastic dissipation in the seal. Abrasion can degrade a seal in a matter of hours, forcing removal of the vehicle from service for seal replacement. Abrasion rate is a function of seal preload, or tightness, and the resulting friction force on the linkage. Abrasion is also proportional to operating depth because water pressure deforms the seal, pushing more tightly against the linkage. Preloading and seal deformation due to water pressure also determine the depth at which friction exceeds actuator strength and lockup occurs. 
     Leaks and lockup together determine the practical depth range of a submersible vehicle using dynamic seals for actuators that penetrate the pressure hull. These depths are typically shallow relative to those at which a submersible vehicle might otherwise easily operate. At the same time, friction loss consumes energy and, thereby, shortens the duration of submersible vehicle operation. Clearly, a reliable and affordable actuator that can reduce or eliminate friction loss and permit a greater range of operating depth for submersible vehicles would be desirable. 
     SUMMARY OF THE INVENTION 
     As a first aspect, embodiments of the present invention are directed to an underwater assembly. The underwater assembly comprises: a hull having an internal cavity that is in fluid communication with the external environment; an inductive actuator mounted within the cavity of the hull; a current source mounted in the hull and electrically connected to the actuator; and a movable member connected with the actuator and positioned external of the hull. Provision of current to the actuator causes the movable member to move relative to the hull. 
     In some embodiments, the assembly is an underwater vehicle, and the movable member assists in propelling and/or navigating the vehicle. In additional embodiments, the assembly includes a controller that controls the magnitude of current provided to the actuator. 
     As a second aspect, embodiments of the present invention are directed to an underwater vehicle comprising: a hull having an internal cavity that is in fluid communication with the external environment; an inductive actuator mounted within the cavity of the hull; a current source mounted in the hull and electrically connected to the actuator; a movable member connected with the actuator and positioned external of the hull; and a propeller mounted to the hull and configured to propel the vehicle. Provision of current to the actuator causes the movable member to move relative to the hull. 
     As a third aspect, embodiments of the present invention are directed to a method of controlling the orientation of a movable member on an underwater assembly, As a first step, the method comprises (a) providing an underwater assembly, comprising: a hull having an internal cavity that is in fluid communication with the external environment; an inductive actuator mounted within the cavity of the hull; a current source mounted in the hull and electrically connected to the actuator; and a movable member connected with the actuator and positioned external of the hull. The method further comprises (b) receiving instructions at a controller, the instructions providing information associated with the position of a movable member. The method also comprises (c) generating current in the actuator with the current source, wherein the magnitude of the current generated is determined by the instructions received at the controller, the current generated in the actuator causing the movable member to take a predetermined position relative to the hull. In some embodiments, the assembly is an underwater vehicle. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a partial perspective view of an unmanned underwater vehicle according to embodiments of the present invention. 
         FIG. 2  is an enlarged perspective view of an exemplary flooded actuator of the unmanned underwater vehicle of  FIG. 1 , with the connecting battery and controller shown schematically. 
         FIGS. 3-5  are cutaway side views of the vehicle of  FIG. 1 , showing one fin in a neutral position ( FIG. 3 ), an extreme counterclockwise position ( FIG. 4 ), and an extreme clockwise position ( FIG. 5 ). 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION 
     The present invention will now be described more fully hereinafter with reference to the drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, like numbers refer to like elements throughout. Thicknesses and dimensions of some components may be exaggerated for clarity. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein the expression “and/or” includes any and all combinations of one or more of the associated listed items. 
     In addition, spatially relative terms, such as “under”, “below”, “lower”, “over”, “upper” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “under” or “beneath” other elements or features would then be oriented “over” the other elements or features. Thus, the exemplary term “under” can encompass both an orientation of over and under. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     Well-known functions or constructions may not be described in detail for brevity and/or clarity. 
     Turning now to the drawings, an unmanned underwater vehicle (UUV), designated broadly at  10 , is shown in  FIG. 1 . The UUV  10  is a submersible vehicle. As used herein, a “submersible” vehicle is defined as any object operable in water that comprises a hull and at least one externally actuated component. The UUV  10  includes a hull  12  having an interior cavity  14 , a motor  16  attached to the hull  12  within the cavity  14 , a propeller  18  attached to a shaft  20  attached to the motor  16 , four fins  22  (only one of which is shown in  FIG. 1 ), and a respective actuator  24  attached to each fin  22  via a fin linkage  26 . These components are discussed in greater detail below. 
     Referring again to  FIG. 1 , the hull can be any type of housing or container having at least a portion into which water can flow (i.e., the cavity  14  is in fluid communication with the external environment). An example is a shell substantially open in design, although portions can be solid or closed to water intrusion. The hull  12  can be made of any material providing adequate mounting capability. In some case, the material is selected to prevent interaction with a field created by the inductive unit. Exemplary hull materials include polymeric materials, metals, and composite materials. 
     The motor  16 , propeller  18  and shaft  20  can be any components known to be suitable for the propulsion of a UUV. In some embodiments, the motor  16  may be a “flooded” motor, wherein “flooded” refers to a structure with at least one portion open to water and being operable for substantial periods in the presence of water; in other embodiments, the motor  16  may be encased in a watertight portion of the hull  12 . The motor  16  is typically powered by a battery  50  that is located aft of the motor  16 . An exemplary flooded motor is Model No. 136210, available from Maxon Precision Motors, Fall River, Mass. 
     Referring now to  FIG. 2 , an exemplary actuator  24  is shown therein. The actuator  24  is a flooded actuator that includes a coil section  28  and a magnet  32 . The coil section  28 , which comprises a material that can effect a desired electromagnetic interaction with the magnet  32 , includes a hollow central section  29  within which the magnet  30  resides. The coil section  28  is electrically connected to the battery  50  (or, in some embodiments, to a separate battery) that provides current thereto via a cable  30  or other electrical connector. The magnet  32  is pivotally interconnected with the coil section  28  at a pivot  34  for rotation about an axis A 1 . Thus, the coil section  28  acts as a stator, and the magnet  32  acts as a rotor. 
     In the illustrated embodiment, both the coil section  28  and the magnet  32  are covered with a coating that protects them from an underwater environment, although in some embodiments one or both of the coil section  28  and magnet  32  may lack a waterproofing coating. Such a coating is typically a polymeric material, such as a rubber or plastic material, and may be applied by dipping, spraying, molding, or the like. An exemplary material is polyxylylene coating, available from Kisco Conformal Coating, San Jose, Calif. under the trade name diX. 
     Referring now to  FIG. 3 , each actuator  24  is connected to its respective fin  22  via the fin linkage  26 . The fin linkage  26  includes a toggle link  38  that is attached to and pivots with the magnet  30  and a connecting link  40  that is pivotally attached to the upper end of the toggle link  38 . The connecting link  40  extends forwardly to attach to the fin  22  via a ball-and-socket joint with a projection  23  of the fin  22 . The fin  22  is then mounted to a front portion of the hull  12  for rotation about an axis A 2 . 
     The mounting of the fin  22  to the hull  12  need not comprise a dynamic seal; in some embodiments, it may comprise a low friction guide or the like that can maintain the fin  22  along the axis of rotation A 2  without substantially impeding its motion. The members comprising the fin linkage  26  are typically formed of materials that can resist and operate in an underwater environment. 
     Referring back to  FIG. 2 , a controller  60  is mounted in the hull  12  and associated with the battery  50 . The controller  60  controls the amount of current supplied to each of the actuators  24 . In some embodiments, the controller  60  may be directly connected to the battery  50  and to the actuators  24 ; in other embodiments the controller  60  may be connected to the battery  50 , which is in turn connected to the actuators  24 . The controller  60  is typically connected to an instruction source (not shown), which may be directly connected to the controller  60 , may be pre-programmed or programmable, and/or may be configured to receive instructions wirelessly from a remote source. In one embodiment, the controller  60  is configured to receive navigational instructions for piloting the UUV  10 . 
     The controller  60  may also include a sensor  62  (shown in  FIG. 1 ) that can provide feedback to the controller  60 . Feedback may be in the form of the position of the fin  22  or a component of the fin linkage  26 , the force exerted on the fin  22 , the orientation of the hull  12 , or a similar relationship. As examples, the sensor  62  may be attached to (a) the fin  22  to determine its angle relative to the hull  12 , a guide rod (as shown in  FIG. 1 ) that guides the fin linkage  26  to determine its movement, (c) the magnet  32  to determine its angle relative to the coil section  28 , or (d) the nose of the hull  12  to determine the direction of the UUV  10  compared to a desired compass heading. Those skilled in this art will recognize that other feedback mechanisms may also be suitable. 
     In operation, the controller  60  receives instructions from the instruction source, such as a guidance and control module, regarding the intended direction of the UUV  10 . The controller  60  and/or the battery  50  then provide current to the coil section  28 . Current in the coil section  28  produces an electromagnetic force on the magnet  32  that induces the magnet  32  to rotate relative to the coil section  28  at the pivot  34  and about the axis A 1 . 
     As can be seen in  FIGS. 3-5 , rotation of the magnet  32  in turn induces rotation in the fin  22  about the axis A 2 . The actuator  24  and fin  22  are shown in a neutral position in  FIG. 3 , with the fin  22  pointing essentially straight astern. As can be seen in  FIG. 4 , counterclockwise rotation of the magnet  32  rotates the toggle link  38  counterclockwise about the pivot  34 . This rotation draws the connecting link  40  rearwardly relative to the hull  12 . Rearward movement of the connecting link  40  in turn draws the projection  23  rearwardly, such that the fin  22  rotates counterclockwise about the axis A 1 . The fin  22  can also be rotated clockwise from the neutral position of  FIG. 3  by inducing the magnet  32  to rotate clockwise ( FIG. 5 ). 
     When the UUV  10  is moving underwater, such movement produces a force on the fin  22  in relation to angular position of the fin  22  relative to straight astern. If the fin  22  is to maintain its position, the magnitude of the current supplied to the coil section  28  should be sufficient to induce an equal and opposite counterforce in the fin  22 . The current level supplied to the coil section  28  is then maintained as long as the fin  22  is to maintain the desired position. The controller  60  receives feedback from the sensor  62  regarding the position of the fin  22  and adjusts the current magnitude accordingly. If the path of the UUV  10  is to be changed, the controller  60  receives instructions regarding the change in path and, again, adjusts accordingly the magnitude of the current supplied to the coil section  28  in order to adjust the position of the fin  22 . 
     It will be apparent to those versed in the art that the above-described flooded design and inductive coupling can eliminate primary shortcomings of dynamic seals used to operate external devices using an actuator mounted within the hull. The ability to eliminate dynamic seals can reduce the abrasion, lock-up and energy loss issues typically associated with dynamic seals. 
     Those skilled in this art will appreciate that the flooded design concept can be applied to other moveable members that are located underwater and mounted external to the hull. For example, rather than a directional fin, the actuator may be attached to a flapping or rotating fin for propulsion, a propeller, a grasping clamp, an articulated arm, a valve cover, or the like, to transmit force, torque or energy to the moveable member. 
     Also, although a relatively simple actuator linkage is shown herein, other embodiments may employ linkages having different configurations. Those skilled in this art will appreciate that the pivots between links or other components can take a variety of configurations, such as pivot pins, rivets, bolt and nut combinations, and the like, any of which may be suitable for use with the present invention. Also, the shapes and configurations of the links themselves may vary, as will be understood by those skilled in this art. Further, some links may be omitted entirely in some embodiments, and additional links may be included in some embodiments. Also, other mechanical joints, such as slider-crank mechanisms, rack-and-pinion mechanisms, gear- or cam-driven mechanisms, and the like, may also be employed. 
     It should also be noted that, although in the illustrated embodiment, the coil section  28  is fixed relative to the hull  12  and the magnet  32  rotates relative to the hull  12 , in other embodiments the coil section  28  may rotate relative to a stationary magnet, and in still further embodiments both the coil section and magnet  32  may rotate relative to the hull  12 . 
     Further, although a UUV particularly suited as a mobile countermeasure for torpedo defense is illustrated herein, other types of vehicles and structures may also be suitable use with embodiments of the present invention. For example, unmanned vehicles for mine countermeasures and manned vehicles for submerged object recovery may benefit from a flooded actuator. As another example, an articulated arm moveable via a flooded actuator may be mounted to a pier, buoy, mooring or the like. Those skilled in this art will understand that a flooded actuator may also be employed for other applications. 
     The foregoing is illustrative of the present invention and is not to be construed as limiting thereof. Although exemplary embodiments of this invention have been described, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the claims. The invention is defined by the following claims, with equivalents of the claims to be included therein.