Patent Publication Number: US-8993948-B2

Title: Rolling vehicle having collar with passively controlled ailerons

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention is in the field of control systems for spinning, rolling, or roll stabilized vehicles, such as spinning or rolling projectiles/missiles. 
     2. Description of the Related Art 
     In certain military applications, there is a significant need for “smart” projectiles wherein the operator can effectively control the course the projectile takes and the target location that is impacted. Such navigational control requires the ability to impart precise forces to a rapidly spinning projectile with respect to the Earth inertial frame to achieve a desired directional course. Some past devices have used arrays of propulsive outlets, fuels and pyrotechnics to produce the necessary forces for the desired two-dimensional course correction. However, these devices suffer from significant disadvantages, such as the danger of premature explosion, and the shock caused by these devices often leads to imprecise course corrections. 
     Part of such past projectiles have been guidance kits with steering mechanisms for steering the spinning or rolling projectiles. There is a need for improvement of such kits and steering mechanisms. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the invention, a steering mechanism includes a rolling collar having ailerons that passively change angle of attack as a function of dynamic pressure. 
     According to another aspect of the invention, an air vehicle includes: a fuselage that rolls about a longitudinal axis of the fuselage; and a collar that is positionable relative to the fuselage. The collar includes ailerons that passively change angle of attack as a function of dynamic pressure of the projectile. 
     According to yet another aspect of the invention, an air vehicle includes: a fuselage that rolls about a longitudinal axis of the fuselage; and a collar that is positionable relative to the fuselage. The collar includes ailerons that provide a circumferential force on the collar during flight of the projectile. The ailerons resiliently change angle of attack as a function of dynamic pressure of the projectile. 
     According to still another aspect of the invention, a fuzewell guidance kit includes: a guidance kit fuselage; and a collar that is rotatable relative to the fuselage. The collar includes ailerons that passively change angle of attack as a function of dynamic pressure. 
     To the accomplishment of the foregoing and related ends, the invention comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The annexed drawings, which are not necessarily to scale, show various aspects of the invention. 
         FIG. 1  is an oblique view of a projectile in accordance with an embodiment of the present invention. 
         FIG. 2  is an oblique view of a guidance kit that is part of the projectile of  FIG. 1 . 
         FIG. 3  is a cross-sectional view of a collar according to an embodiment of the invention. 
         FIG. 4  is a detailed view of part of the collar of  FIG. 3 . 
         FIG. 5  is a cross-sectional view of a collar according to another embodiment of the invention. 
         FIG. 6  is a detailed view of part of the collar of  FIG. 5 . 
         FIG. 7  is a plan view of an aileron of the collar of  FIG. 5  in a first configuration. 
         FIG. 8  is a plan view of the aileron of  FIG. 7  in a second configuration. 
         FIG. 9  is a side view of a fuzewell guidance kit in accordance with yet another embodiment of the invention. 
         FIG. 10  is a cross-sectional view of a collar of the fuzewell guidance kit of  FIG. 9 . 
         FIG. 11  is a view schematically showing the operation of the aileron adjustment mechanism of the guidance kit of  FIG. 9 . 
         FIG. 12  is an oblique view of a collar in accordance with still another embodiment of the present invention. 
         FIG. 13  is a side cross-sectional view of a portion of the collar of  FIG. 12 . 
         FIG. 14  is a view along section  14 - 14  of  FIG. 13 . 
     
    
    
     DETAILED DESCRIPTION 
     A spinning, rolling, or roll-stabilized object or vehicle, such as a projectile, includes a fuselage that rotates about its longitudinal axis (spins) during flight. A collar is positionable relative to the fuselage to steer the projectile, with the collar having ailerons to provide a roll force to position the collar. The collar also has elevators to provide lateral force to steer the projectile. The positioning of the collar may be accomplished by moderating the roll force of the ailerons with a constraining force, such as a braking force, to hold the position of the collar substantially constant with regard to a longitudinal axis of the projectile. The ailerons passively change effective angle of attack with changes in the dynamic pressure of the projectile. At low speeds the passive ailerons have a relatively large angle of attack, in order to provide a sufficient roll force to counter-rotate the collar in the opposite direction from the spin (roll) direction of the projectile. At high speeds, when roll forces are easier to generate with the ailerons, the ailerons resiliently reduce their angles of attack, avoiding large rolling forces on the collar. By limiting the rolling forces on the collar, the amount of counter braking or other restraining force used in positioning the collar is limited. This allows more efficiency in use of energy during flight of the projectile. The passive change of aileron angle of attack may be accomplished through any of a variety of mechanism, such as torsion bars, leaf springs, or torsion springs. 
       FIG. 1  shows a vehicle or projectile  10  that has a spinning or rolling fuselage  12 . The fuselage  12  rotates about a longitudinal axis  14  of the fuselage  12 . The projectile  10  may be spun as part of a launching process, and/or may have a spin or roll moment imparted to it during flight, for example using moment-producing surfaces in the airstream, such as angled or otherwise lift-producing tail fins  18 , canards, or wings, or by using thrust mechanisms. 
     In the illustrated embodiment, the projectile  10  also includes a fuzewell guidance kit  20  that is coupled to a front end of the fuselage  12 . A “fuzewell guidance kit” is used herein to refer to a device that combines guidance and fuzing in one device that is installed in a fuze well. The guidance kit  20  fits into a fuze well for receiving a fuze, as part of a projectile  10 . The guidance kit  20  may include a fuse for detonating a warhead or other explosive of the projectile  10  (not shown), perhaps when the projectile  10  is in proximity to a target. 
     The guidance kit  20  also performs a guidance function used in steering the spin-stabilized projectile  10 . With reference in addition to  FIG. 2 , the guidance kit  20  includes a collar  24  that is rotatable relative to the spinning or rolling fuselage  12 , as well as relative to a guidance kit fuselage  22  that rolls along with the fuselage  12 . The collar  24  can be positioned relative to the fuselage  12  to position lift-producing aerodynamic surfaces (elevators)  26  to provide lateral forces to steer the projectile  10  using bank-to-turn steering. The collar  24  also includes ailerons  28  that provide a rotational (circumferential) force that is used to position the collar  24 . The aerodynamic force from the ailerons  28  cause the collar  24  to rotate relative to the fuselage  12 , for example causing the collar  24  to rotate in a direction opposite to that of the fuselage  12 . This counter-rotation of the collar  24  may be modulated by use of a brake  30 . This allows the collar  24  to be positioned so as to be maintained in a substantially-constant position relative to a coordinate system that moves with translation of the projectile  10 , but does not rotate with spinning or rolling of the fuselage  12 . Thus the collar  24  may be positioned relative to the longitudinal axis  14  to allow the lateral force from the elevators  24  to be applied in the right direction in order to achieve the desired bank-to-turn steering of the projectile  10 . 
     The brake  30  may use any of a variety of suitable known mechanisms for slowing the relative rotation between the collar  24  and the fuselage  12 . The brake  30  may utilize frictional forces, electrical forces (as in an electric motor), or magnetic forces to slow the relative rotation between the collar  24  and the fuselage  12 . This allows positioning of the collar  24  to be obtained and maintained as desired. 
     With increasing dynamic pressure (speed) of the projectile  10 , ailerons that have a fixed angle of attack provide increasing aerodynamic force to counter-rotate the collar  24  relative to the fuselage  12 . An increase in the counter-rotation aerodynamic force would require use of more braking force to position the collar  24 . This would require the brake  30  to be able to exert more force, and/or may require more energy to be expended in applying braking force to position the collar  24 . 
     In order to reduce the amount of braking required at high projectile dynamic pressures, the ailerons  28  passively alter their angles of attack as a function of the dynamic pressure of the projectile  10 . The alteration of angle of attack is passive in that there is no directed input force or commanded action that causes the change of angle of attack. The change of angle of attack is a result of the configuration of a mechanism that allows change of the aileron angle of attack, with aerodynamic forces being balanced against resilient forces. Some sort of resilient force balances against the aerodynamic forces on the ailerons  28  to put the ailerons  28  at different angles of attack for different levels of different aerodynamic force (different dynamic pressures of the projectile  10 ). 
     The vehicle is described herein in terms of a projectile that travels through air. However aileron positioning system may be used in a variety of air vehicles, whether powered missiles, unpowered projectiles, or other sorts of air vehicles. 
     The resilient force for positioning the ailerons  28  may be from any of a variety of mechanisms, such as leaf springs, torsion bars, torsion springs, and elastic bands. A few of these resilient mechanisms are shown in the illustrative embodiments described below. 
       FIGS. 3 and 4  illustrate a collar  44  having a mechanism  46  that allows ailerons  48  to passively change angle of attack. The mechanism  46  includes, for each of the ailerons  48 , a torsion bar  50  that is coupled at one end to a shaft  54  of the aileron  48 , for example using corresponding keys on the end of the torsion bar  50  and the aileron  48 . The opposite end of the torsion bar  50  is fixed relative to a collar housing  58 , such as by use of a key (not shown) on the torsion bar  50  that fits into a corresponding keyed surface of the collar housing  50 . The torsion bar  50  thus resiliently provides resistance for rotation of the shaft  54  relative to the collar housing  58 . A bearing  60  is coupled to the shaft  54  and the collar housing  58  to provide support to the aileron  48  as the aileron  48  experiences aerodynamic forces on a blade  62  of the aileron  48  during projectile flight. The bearing  60  may be a journal bearing with a rounded shaft end  64  movable within the bearing  60  to allow the aileron  48 , to shift position relative to the collar housing  58 , for example shifting angle of attack, while still being able to transmit aerodynamic loads from the blade  62  to the collar housing  58 . 
     The torsion bar  50  may be a piece of metal of any of a variety of shapes. The torsion bar  50  may be configured so that it is unloaded when there are no aerodynamic forces on the aileron  48 , with the aileron  48  at a maximum angle of attack. Aerodynamic forces put a torque on the aileron  48 , and the torsion bar  50  provides a resistance to the change of angle of attack of the aileron  48 . The balance between the aerodynamic forces on the aileron blade  62  and the forces from the twisting of the torsion bar  50  establishes the aileron position (angle of attack) for any given dynamic pressure (speed). The ailerons  48  thus passively change angle of attack as a function of projectile dynamic pressure, reducing the angle of attack as the projectile dynamic pressure increases. 
     The collar  44  includes other parts that are not described further. For example the collar  44  (and the collars of the other embodiments described below) includes fixed-angle-of-attack elevators  68 . 
       FIGS. 5-8  show another embodiment, a collar  84  has a mechanism  86  for passively changing the angle of attack of ailerons  88 . The mechanism  86  is located within blisters  90  on the outside of a collar housing  98 . The ailerons  88  each have a blade  82  and a shaft  84 , with a tab  86  extending from the shaft  84  within the blister  90 . Also within each of the blisters  90  is a resilient device  94 , such as a leaf spring, that is in contact with the tab  86 . The spring  94  biases the aileron  88  to a certain low-speed angle of attack, for example 10 degrees ( FIG. 7 ). The spring  94  also provides resistance to changes in angle of attack as the projectile increases its dynamic pressure, with the angle of attack decreasing with increasing dynamic pressure, for example to a high-speed angle of attack of 3 degrees ( FIG. 8 ). A bearing  100  may be used to allow the aileron  88  to shift position (angle of attack), while still mechanically supporting the aileron  88 . The bearing  100  may be a journal bearing that functions in a manner similar to that of the bearing  60  ( FIG. 3 ). 
     The blisters  90  may have a streamlined shape that provides low drag. The use of the blisters  90  prevents the mechanism  86  from intruding into an interior space  104  surrounded by the collar  84 . This allows for the same interior space configuration as for a projectile that does not have the passively-movable ailerons  88  such as described above. 
       FIGS. 9-11  shows a further embodiment, a fuzewell guidance kit  120  with a collar  124  that has a mechanism  126  to allow ailerons  128  to passively change angle of attack. The ailerons  128  each have a blade  132  that is attached to a shaft  134 . The blade  132  and the shaft  134  may even be portions of a single continuous unitary part. 
     The shaft  134  passes through a hole  136  in a collar housing  138 . The hole  136  may have a bearing around it to aid in allowing the aileron  128  to shift position (angle of attack). The shaft  134  has a threaded shaft end  142 . A spring washer (Belleville washer)  144  is held onto the shaft end  142  by a nut  148  that is threaded onto the shaft end  142 . The spring washer  144  is used to keep the aileron  128  pulled in against the collar housing  138 . 
     A pin  152  is used to connect a crank  154  rigidly to the shaft end  142 . A distal end  156  of the crank  154  is connected to a tension spring  158  that is used to bias the aileron to a maximum angle of attack, and to provide resistance against passive reduction of the angle of attack by aerodynamic forces on the aileron  128 . The tension spring  158  may be any of a variety of suitable springs. Stops  160  and  162  may be provided to limit the travel of the crank  154 , providing limits to the maximum and/or minimum angle(s) of attack obtainable by the ailerons  128 .  FIG. 11  shows the two extreme positions of the crank  154 , against the stops  160  and  162 . 
       FIGS. 12-14  show still another embodiment, a collar  184  in which a mechanism  186  is used to allow ailerons  188  to passively change their angles of attack. Each aileron  188  is coupled to a collar housing  198  by use of a pivot pin  200  that threads into an aileron blade  202 , and passes through a hole in the collar housing  198 . A bearing  204 , retained by a bearing retainer  206 , is used to allow the pivot pin  200 , and thus the aileron  188 , to swivel relative to the collar housing  198 . An elastic band  208 , located in an outward protrusion  210  from the collar housing  198 , is attached at one end to the pivot pin  200 , and at an opposite end to a second pin  212  that extends between opposite walls of the protrusion  210 . The elastic band  208  wraps around the pivot pin  200 . Stretching of the elastic band  208  provides resistance to reductions in angle of attack from an initial maximum value that occurs when the projectile is not moving. The balance between the aerodynamic forces on the blade  202 , and the restorative elastic force from the stretched elastic band  208 , positions the ailerons  188 , with the ailerons  188  passively reducing their angles of attack as the dynamic pressure of the projectile increases. One or more travel limit pins  216  may be used as mechanical stops to limit the angle of attack of the ailerons  188 . 
     In the foregoing embodiments the ailerons are able to change angle of attack independently of one another. This may improve performance at high angles of attack, by allowing each aileron to relax to the local angle of attack determined by the restoring force. For fixed projectiles collar spin reversal may be possible for some combinations of dynamic pressure and high projectile angle of attack. Slightly different angles of attack for the different ailerons may aid in avoiding this collar spin reversal. As an alternative, however, the angles of attack of the two ailerons may be linked, for example by mechanically linking the ailerons. 
     By varying the aileron incidence angle inversely with dynamic pressure, single collar configuration can accommodate a large combination of projectiles, projectile charges, and gun elevation angles. Other advantages for the collars described above are that their configurations are mechanically simple and self adjusting, they provide only a minimal increase in collar inertia, and they are inexpensive, gun hardenable, and do not require external power or sensors. 
     Many of the features described above with regard to one or more of the embodiments may be combined with features of the other embodiments. Examples of features that may be used with other embodiments include use of blisters, mechanical stops, pivot bearings or other bearings, having aileron adjustment mechanisms located in whole or in part within a collar housing, alternating adjustable ailerons with elevators around the perimeter of a collar housing, inclusion of elevators for bank-to-turn steering, and the collars being parts of a fuzewell guidance kit. 
     Although the invention has been shown and described with respect to a certain preferred embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described elements (components, assemblies, devices, compositions, etc.), the terms (including a reference to a “means”) used to describe such elements are intended to correspond, unless otherwise indicated, to any element which performs the specified function of the described element (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiment or embodiments of the invention. In addition, while a particular feature of the invention may have been described above with respect to only one or more of several illustrated embodiments, such feature may be combined with one or more other features of the other embodiments, as may be desired and advantageous for any given or particular application.