Patent Document

BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to guided air vehicles with control surfaces, in general, and more particularly, to method and apparatus for stowing and deploying the control surfaces of the guided air vehicle.  
         [0002]     Guided air vehicles such as missiles, smart bombs, smart munitions, projectiles and bullets, for example, utilize control surfaces, such as fins, canards and wings, for example, to guide their trajectory along a desired flight path. Such air vehicles, especially those launched from manned or unmanned aircraft or ground craft, require that their control surfaces be stowed within or partially within the body of the air vehicle during storage and transportation, and also during launch in order to: (1) minimize potential damage; (2) allow the air vehicle to fit physically in the launch apparatus; and (3) minimize the effects of aerodynamic forces acting upon the control surfaces during launch. Once the air vehicle is in flight, the control surfaces may be deployed to their desired positions for guiding the vehicle. In many instances, control surface deployment is controlled by an on-board processor to allow completion of the air vehicle mission in accordance with a desired target strategy.  
         [0003]     Many different apparatus have been developed for stowing and deploying the control surfaces of an air vehicle including: electromechanical, solenoids, pyrotechnic gas generators and retractors, and mechanical apparatus such as no-backs and inefficient transmissions, for example. Depending upon the circumstances and operating environments, some apparatus were found to be inappropriate for the given task; others were found not to work; and still others were found to be too expensive to implement. In addition, deployment apparatus using pyrotechnic devices or other similar devices have significant drawbacks of: not being indestructibly testable since they operate on a single shot basis, and of inducing significant shock to the supporting structure.  
         [0004]     Accordingly, there is a need for method and apparatus for stowing and deploying control surfaces of a guided air vehicle that overcome the drawbacks and limitations of the conventional apparatus and are simpler and more cost effective. The present invention is intended to provide such apparatus and method that satisfy these needs.  
       SUMMARY OF THE INVENTION  
       [0005]     In accordance with one aspect of the present invention, apparatus for stowing and deploying a plurality of control surfaces of a guided air vehicle comprises: a housing including: a plurality of slotted openings along an outside surface thereof; and a corresponding plurality of cavities within the housing, each cavity extending to the outside surface of the housing through the slotted opening corresponding thereto and configured to accommodate span wise stowage of a corresponding control surface of the plurality, and each cavity having a section including an angled ledge and side wall support surface to accommodate stowage of the corresponding control surface in a span wise canted position with respect to the corresponding slotted opening.  
         [0006]     In accordance with another aspect of the present invention, a method of stowing and deploying a plurality of control surfaces of a guided air vehicle comprises the steps of: folding each control surface of the plurality edge wise through a corresponding slotted opening disposed along an outside surface of a housing and into a corresponding cavity within the housing; moving each folded control surface into a stowage section of the corresponding cavity to edge wise mis-align each folded control surface from the corresponding slotted opening; moving each control surface in the corresponding cavity from the corresponding stowage section into edge wise alignment with the corresponding slotted opening; and deploying each control surface edge wise aligned with the corresponding slotted opening from the cavity through the corresponding slotted opening to a deployed position. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]      FIGS. 1A and 1B  are side and sectional top views, respectively, of a control unit containing a plurality of control surfaces shown in a deployed state suitable for embodying the broad principles of the present invention.  
         [0008]      FIG. 2  is a block diagram functional schematic of an exemplary motor controller and control surface actuator motor assembly suitable for use in the embodiment of  FIGS. 1A and 1B .  
         [0009]      FIGS. 3A and 3B  are side and sectional top views, respectively, of the control unit showing the plurality of control surfaces in a folded and ready to deploy state.  
         [0010]      FIGS. 4A and 4B  are side and sectional top views, respectively, of the control unit showing the plurality of control surfaces in a folded and stowed state.  
         [0011]      FIG. 5  is a cut away isometric illustration of a portion of the control unit showing the plurality of control surfaces in a stowed state in greater detail.  
         [0012]      FIGS. 6A and 6B  are side and top view illustrations of the control unit showing forces exerted thereon during launch and flight. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]      FIGS. 1A and 1B  are side and sectional top views, respectively, of a control unit  10  containing a plurality of control surfaces suitable for embodying the broad principles of the present invention. The control unit  10  may be disposed in a guided air vehicle (GAV) in such a manner that the plurality of control surfaces protrude through the outer shell of the GAV when deployed in order to guide the GAV during flight as will be better understood from the description found herein below. In the exemplary embodiment depicted in  FIGS. 1A and 1B , there are four control surfaces  12 ,  14 ,  16  and  18  which are shown in their deployed positions. In this embodiment, the four control surfaces are disposed about the circumference of a cylindrically shaped metal housing  20 , approximately 90° apart. Each of the control surfaces  12 ,  14 ,  16  and  18  which may be made of Titanium or steel, for example, are beveled width wise at an angle away from a center line along the span thereof to render knifed leading and trailing span edges. Thus, each control surface appears sideways in the shape of an elongated diamond as shown by the side view of surface  14  in  FIG. 1A . Note that the material and shape of the control surfaces  12 ,  14 ,  16  and  18  are described herein by way of example and that other materials and shapes may be used just as well without deviating from the broad principles of the present invention.  
         [0014]     The metallic housing  20  includes vertical slotted openings  22 ,  24 ,  26  and  28  through which the control surfaces  12 ,  14 ,  16  and  18 , respectively, may be folded into cavities of the housing  20  and stowed away as will become more evident from the description found herein below. In the present embodiment, the housing  20  may be made of Titanium, steel, aluminum or high performance plastics and may be partitioned into two stages—a bottom stage  30  and a top stage  32 , for ease in the assembly of parts. For example, electrical actuating motors for each of the control surfaces may be seated in cavities on the top surface of the bottom stage  30  and protrude upward beyond the top surface. In addition, the bottom stage  30  contains in cut out cavities thereof drive gear trains and shafts mechanically coupling the actuator motors to their respective control surfaces. Exemplary shafts  34  and  36  are shown coupled to control surfaces  12  and  16 , respectively, in  FIG. 1A . An assembly of motor controller electronics and one or more power sources, such as batteries, for example, may be also disposed in cut out cavities of the bottom stage  30  and connected through wiring to power and control the actuator motors.  
         [0015]     Once the motors, gear trains, shafts, batteries and electronic assembly are secured in place in and on the bottom stage  30 , then the top stage  32  may be placed on top of the bottom stage  30  in a position which aligns the respective slotted openings of the two stages  30  and  32 . The top stage  32  has cavities cut from the bottom surface thereof which match the configurations of the control surface actuator motors which protrude up from the bottom stage  30  so as to fit over and cover them. The top stage  32  sits on and around a circumferential edge seal  40  of the bottom stage  30 . A long screw  42  may be disposed up through stage  30 , screwed into a threaded metal hole in stage  32  and tightened to secure the two stages  30  and  32  together around the edge seal  40 . An electrical connector  44  may be secured to an aperture at the bottom of the bottom stage  30  to permit electrical connections of command signals from a command processor of the GAV to couple to the motor controller electronics of the unit  10 .  
         [0016]     Disposed on top of the top stage  32  is a circular retaining cap or disk  50  which may be made of a plastic material, for example. The disk  50  includes slots  52 ,  54 ,  56  and  58  around the circumference of its side surface, approximately 90° apart. In a zero degrees (0°) position state, the disk  50  is positioned with respect to the top stage  32  so that the slots  52 ,  54 ,  56  and  58  align respectively with the slotted openings  22 ,  24 ,  26  and  28 . A screw  60  secures the disk  50  to the top stage  32  and acts as a pivot point for a rotation of the disk  50 . Grooves corresponding to the control surfaces  12 ,  14 ,  16  and  18  are cut into the bottom of the retaining disk  50 . These groves extend radially from around the pivot point out to the slots  52 ,  54 ,  56  and  58  to accommodate the tips of the control surfaces when folded into the housing  20 . Clearance is retained between the retaining disk  50  and top stage  32  circumferentially along a circular edge  62  to permit a substantially free rotation of disk  50  with respect to the top stage  32 , the effects of such rotation being explained in greater detail in the description below.  
         [0017]     In the present embodiment, the control surfaces  12 ,  14 ,  16 , and  18  may be folded manually through their respective slotted openings  22 ,  24 ,  26  and  28  into the housing  20 . Generally, when deployed, each of the control surfaces are locked into their deployed positions by a latch mechanism, for example. So, when it is time to rotate each control surface into the housing  20 , the latch mechanism is unlatched and each control surface is rotated about an axis  70  into the housing  20  to the 0° position or ready to deploy state (see  FIGS. 3A and 3B ). Alternatively, the motor controller of the electronics assembly in the bottom stage  30  may be pre-programmed to operate the control surface actuator motors through a sequence of operations to fold the control surfaces into the housing  20 .  
         [0018]     In either case, the motor controller is pre-programmed to operate the actuator motors through a sequence of operations to simultaneously stow them in place from the 0° position. The motor controller is also pre-programmed to operate the actuator motors through a sequence of operations, as directed by commands from the command processor of the GAV, for example, to move the control surfaces from the stowed state to the ready to deploy state, and then, to deploy the control surfaces from the housing  20 . In the present embodiment, the operations of the plurality of motor actuators are synchronized substantially. However, it is understood that this need not be the case. Generally, during testing of the unit  10 , the control surfaces  12 ,  14 ,  16  and  18  are controlled through various operations. Once successful testing is completed, the control surfaces are folded up into the housing  20  and stowed away therein for storage, transportation and launch. Generally, thereafter, the control surfaces will not be deployed again until commanded to do so after launch and during flight of the GAV.  
         [0019]     Once the control surfaces are stowed away in the housing  20 , the unit  10  may be disposed within a guided air vehicle (GAV) at a position along the length thereof dependent on whether the control surfaces are to be applied as fins, wings or canards. For example, if the control surfaces are to act as fins, then the unit  10  is disposed at the rear end of the GAV in such a manner to align the slots  22 ,  24 ,  26  and  28  with corresponding slots in the skin or shell of the GAV so that when deployed the control surfaces will protrude through the skin at the rear end of the GAV and act as guiding fins thereof. Accordingly, if the control surfaces are to act as canards, then the unit  10  is disposed at the front end of the GAV in such a manner to align the slots  22 ,  24 ,  26  and  28  with corresponding slots in the skin or shell of the GAV so that when deployed the control surfaces will protrude through the skin at the front end of the GAV and act as guiding canards thereof.  
         [0020]     A block diagram functional schematic of the motor controller, control surface actuator motors and corresponding gear trains suitable for use in the embodiment of  FIGS. 1A and 1B  is shown in  FIG. 2 . Referring to  FIG. 2 , a common motor controller  80  is electrically coupled to actuator motors  82 ,  84 ,  86  and  88  which respectively correspond to control surfaces  12 ,  14 ,  16  and  18 . Each of the motors  82 ,  84 ,  86  and  88  are mechanically coupled to its respective control surface shaft through a corresponding gear train  92 ,  94 ,  96  and  98 . In the present embodiment, the motors and associated gear trains may be made intentionally inefficient to reduce movement of the control surfaces when in a static position. One or more batteries  100  may be coupled to the electrical motors  82 ,  84 ,  86  and  88  and electronic controller  80  to provide operational electric power thereto.  
         [0021]     As noted above, when the controller  80  receives a command via connector  44 , it responds by controlling the motors  82 ,  84 ,  86  and  88  through the proper sequence of operations. The motors  82 ,  84 ,  86  and  88 , in turn, move the corresponding control surfaces  12 ,  14 ,  16  and  18  to their desired positions simultaneously via the respectively corresponding gear train and shaft mechanically linked thereto. For example, if the motor controller  80  is commanded to fold the control surfaces into the housing  20 , it controls the motors  82 ,  84 ,  86  and  88  to rotate the control surfaces about their respective axes  70  until each control surface  12 ,  14 ,  16  and  18  passes through its corresponding slotted opening  22 ,  24 ,  26  and  28  and is contained within their respective cavities of the housing  20  as shown in the  FIGS. 3A and 3B  which are side and sectional top views of unit  10 .  
         [0022]     Referring to  FIGS. 3A and 3B , the control surfaces  12 ,  14 ,  16  and  18  are folded respectively through slotted openings  22 ,  24 ,  26  and  28  into cavities  102 ,  104 ,  106  and  108  cut into the housing  20 . During folding of the control surfaces, the retaining disk  50  is in the 0° position and the tips of the control surfaces pass through retainer slots  52 ,  54 ,  56  and  58  and into the corresponding grooves thereof. Once the step of folding the control surfaces  12 ,  14 ,  16  and  18  into their respective housing cavities  102 ,  104 ,  106  and  108  is complete, the motor controller  80  may be commanded to execute a sequence of pre-programmed operations to control the motors  82 ,  84 ,  86  and  88  to simultaneously rotate and cant the control surfaces  12 ,  14 ,  16  and  18  into a stowed position as shown in  FIGS. 4A and 4B  which are side and sectional top views of unit  10 .  
         [0023]     Referring to  FIGS. 4A and 4B , the cavities  102 ,  104 ,  106  and  108  are cut out from the housing  20  to each include an angled ledge  112 ,  114 ,  116  and  118 , respectively, and an angled side wall support surface  122 ,  124 ,  126  and  128 , respectively, to accommodate stowage of the respectively corresponding control surfaces  12 ,  14 ,  16  and  18 .  FIG. 5  is a cut-away illustration of the housing  20  showing the stowed control surfaces  12 ,  14 ,  16  and  18  in their cavities  102 ,  104 ,  106  and  108  resting behind their respective angled ledges  112 ,  114 ,  116  and  118  and along their angled side wall support surfaces  122 ,  124 ,  126  and  128 . In the present embodiment, the control surfaces  12 ,  14 ,  16  and  18  are controlled simultaneously to their stowed positions by rotating their respective shafts counterclockwise approximately 2.5°, for example, from the 0° position around an axis  130  perpendicular to the page as shown in  FIG. 4A .  
         [0024]     The rotational motion of a control surface about axis  130  to and from a stowed position is achieved in the present embodiment by a pinion gear, which is part of the corresponding actuator motor, driving a spur gear that is part of a ball screw or lead screw. A nut of the ball screw or lead screw has a link attached to it via a pin configuration. An opposite end of the link is attached to an arm using the pin configuration. The arm is integral to an output shaft to which the control surface is assembled using a pin that permits the control surface to pivot about axis  70  from the ready to deploy position (see  FIGS. 3A and 3B ) to the deployed position (see  FIGS. 1A and 1B ).  
         [0025]     Note that as the control surfaces are simultaneously rotated about their respective axes  130  to their canted or stowed positions behind their respective angled ledges and against their respective angled sidewall supports, the tips of the control surfaces which are disposed into grooves of the retaining disk  50  cause the retaining disk  50  along with the slots  52 ,  54 ,  56  and  58  to rotate along with them. Accordingly, when in the control surfaces  12 ,  14 ,  16  and  18  are in their stowed positions, the corresponding slots  52 ,  54 ,  56  and  58  are offset from their 0° position and no longer aligned with their corresponding slotted openings  22 ,  24 ,  26  and  28  as shown in  FIGS. 4A and 4B . The combination of the offset slots  52 ,  54 ,  56  and  58 , the angled ledges  112 ,  114 ,  116  and  118  and the angled supporting sidewalls  122 ,  124 ,  126  and  128  prevent the control surfaces  12 ,  14 ,  16  and  18  from being unintentionally forced out from the housing  20  as will become better understood from the following description.  
         [0026]     During the control surface stowage and launch, the control surfaces are folded within the structure  10  and are canted or stowed over to their respective control surface side-wall supports. In this stowed position, the control surfaces are located behind their respective angled ledges. Upon launch of the GAV, forces act on the control surfaces to force them against their respective control-surface side-wall supports. If the launch produces a GAV spin, the spin acts to force the control surfaces against their respective control-surface side-wall supports, and in addition, acts to force the trailing edge of the control surface against their respective angled ledges caused by a radial centripetal force. The angled ledges prevent the control surfaces from backdriving or rotating toward their respective control surface slotted opening.  
         [0027]     In high-g applications of a GAV such as a cannon or gun launch, special considerations have to be given to the balloting (side-slap) and set-back (primary launch thrust) forces exerted on the control surfaces of unit  10 . The forces developed during high-g acceleration are such that prior anti-backdrive features may be overcome, possibly resulting in a premature deployment. As shown in the illustration of the present embodiment in  FIGS. 6A and 6B , when a balloting force or load is present, a force shown by the arrowed line  142  acting on the control surface  14 , for example, is reacted by an equal force shown by the arrowed line  144  acting on the diametrically opposed control surface  18  resulting in a zero rotational force. The same action occurs for control surfaces  12  and  16  as shown by force arrowed lines  146  and  148 , respectively. Under such conditions in the present embodiment, the control surfaces  12 ,  14 ,  16  and  18  will not backdrive and will not cause premature deployment.  
         [0028]     Also, during set-back force conditions, the control surfaces (which are canted over to the control surface side-wall support) are forced onto their respective side-wall supports. Thus, the side-wall supports absorb some of the set-back load into the housing structure  20 . In addition, the control surface retainer disk  50  is forced downwards onto the control surfaces which aids to prevent control surface rotation toward the slot. During set-forward or muzzle exit conditions, a force is exerted on the control surfaces which tries to move the control surfaces off the side-wall support toward the zero degrees or deployment position. In the present embodiment, control surface rotation is limited by a balanced actuation output, inefficiency in the drive mechanism, gear ratio (higher is better), anti-backdrive features of the cavity and slot wall, some resolved force into the control surface retainer disk and short set-forward time duration in which the control surface has too much inertia to move significantly.  
         [0029]     Once the GAV is launched and in flight, the motor controller of the unit  10  is operative to receive a deployment command via connector  44 . Upon receipt of the control surface deployment command, the control surface motor actuators are controlled by the motor controller  80  to move their respective control surfaces from their stowed positions (see  FIGS. 4A and 4B ) to the zero degrees or ready for deployment positions (see  FIGS. 3A and 3B ). During the movement from the stowed to zero degree positions, the control surfaces are forced against their respective angled ledges due to the radial centripetal forces exerted thereon. Thus, the control surfaces tend to resist movement while in their stowed positions due to friction imposed by their respective ledges. In the present embodiment, the respective motor actuators are designed to be capable of overcoming control surface frictional forces caused by the control surface rubbing against its respective angled ledge. The actuator motors are also designed to be capable of overcoming the force exerted by the sloping feature of the angled ledge.  
         [0030]     As each control surface moves towards its zero degree position in the same rotational sense as described herein above, the control surface retainer disk  50  rotates about its pivot point  60  in the direction of the control surface movement. Accordingly, once the control surfaces are at their respective zero degree positions, they are aligned in their respective slotted openings and are free to be deployed. When the control surfaces are in the ready to be deployed position (see  FIGS. 3A and 3B ), the motor controller  80  is operational to control the actuator motors to cause a simultaneous rotation of the control surfaces  12 ,  14 ,  16  and  18  about their respective axis  70  until the control surfaces are in their deployed positions (see  FIGS. 1A and 1B ). As noted above, during deployment, the control surfaces  12 ,  14 ,  16  and  18  are aligned with and pass through openings in the outer shell of the GAV so that when deployed, the control surfaces protrude out from the shell in the air stream of the GAV to guide the flight thereof.  
         [0031]     It is understood that for standard ground, ship, underwater or air launched applications of a GAV, the slotted control surface retainer disk  50  may not be needed. However, for certain environment conditions, such as extreme vibration, high shock or very high acceleration such as in a gun launch application of a GAV, the slotted control surface retainer disk  50  is desirable to prevent the control surface backdriving of the actuator motor during set-back and balloting conditions.  
         [0032]     In spin applications of the GAV, the centrifugal force exerted radially on the control surfaces by the spin of the GAV will cause the control surfaces to be forced away from the housing  20  as they become aligned with their respective slotted openings. Thus, the deployment movement may be initiated by these radial centrifugal forces. However, in those GAV applications in which no spin of the GAV is anticipated, some additional apparatus may be desirable to momentarily force the control surfaces away from their static ready for deployment positions (see  FIGS. 3A and 3B ) to start the deployment movement thereof. In these instances, a spring like member, like a torsional spring, for example, may be disposed at the pivot pin of each control surface or in each control surface cavity to momentarily apply a force radially outward on the corresponding control surface as it is aligned with its slotted opening of the housing  20 . It is understood that in this embodiment, each actuator motor and associated gear train will have to be designed to be capable of compressing the corresponding spring like member when folding the corresponding control surface into its cavity.  
         [0033]     While the present invention has been described herein above in connection with one or more embodiments, it is understood that this was done by way of example with no intention of limiting the present invention in any way. Accordingly, the present invention should not be limited by the foregoing described embodiments, but rather, construed in breadth and broad scope in accordance with the recitation of the claims appended hereto.

Technology Category: 2