Patent Application
20140312162
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.
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.
The annexed drawings, which are not necessarily to scale, show various aspects of the invention.
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.
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
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.
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.
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.
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.
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.
