Patent Application
20080308671
A typical conventional guided projectile includes a nose cone and a main casing (e.g., an artillery shell casing). The nose cone is capable of moving relative to the main casing and is thus capable of changing the direction of the projectile's trajectory while the projectile is in flight.
To effectuate movement of the nose cone relative to the main casing, the conventional guided projectile further includes a nose cone actuator having an actuator mount and a movable (or actuated) part which moves relative to the actuator mount. The actuator mount of the actuator connects to the main casing and the movable part of the actuator connects to the nose cone to enable pointing or articulating the nose cone relative to the main casing.
In some conventional guided projectile designs, the main casing and the nose cone are required rotate relative to each other. For such designs, the entire nose cone actuator (i.e., the actuator mount and the movable part) rotates relative to the main casing so that the nose cone actuator can continue to point the nose cone in a particular targeted direction. That is, while the main casing rotates around both the actuator mount and the movable part of the nose cone actuator during flight, the actuator extends or retracts the movable part to properly articulate the nose cone at a particular angle relative to a center axis of the main casing thus controlling the direction of the guided projectile.
Unfortunately, there are deficiencies to certain conventional guided artillery shell designs due to demands placed on various components of these designs. In particular, if the control circuitry and the power source for the nose cone actuator reside at fixed locations within the main casing, specialized connecting devices are required to transmit electrical power and electrical control signals from the control circuitry and the power source within the main casing to the nose cone actuator while the main casing rotates relative to the nose cone actuator.
An example of such a specialized connecting device is a slip ring, i.e., a rotary electrical joint. Unfortunately, slip rings provide potential points of failure particularly in view of various extreme environmental conditions that may exist within the guided projectile (e.g., high G-forces, high temperatures, etc.). That is, it is extremely difficult for slip rings to survive the high acceleration of the guided projectile during launch, and then to withstand extremely high operating temperatures while the guided projectile is in flight. Without reliable performance, the guided projectile may inadvertently damage or destroy an unintended target. Furthermore, slip rings are costly and their use in a weapon system may impact the affordability of a weapon system's controller.
In contrast to the above-described conventional guided projectile designs which place the control circuitry and the power source for a nose cone actuator at fixed locations within the main casing, improved techniques involve utilization of a stator (of a brushless electric motor) which attaches to a nose member (e.g., a nose cone of a guidable projectile) and a rotor (of a brushless electric motor) which attaches to a projectile body (e.g., a main casing of the guidable projectile). Accordingly, the stator and the rotor form a motor/generator which is capable of (i) controlling rotation of the projectile body relative to the nose member as well as (ii) generating power. Moreover, electrical control of the stator and other electrical or electromechanical components (e.g., a nose cone actuator) are capable of residing at fixed locations relative to the stator (e.g., on the stator spindle) thus alleviating any need to convey electrical power and electrical control signals from the projectile body to the stator or to the nose member through slip rings.
One embodiment is directed to a guidable projectile having a nose member, a projectile body, and a nose member articulation assembly which couples the nose member to the projectile body. The nose member articulation assembly includes a stator attached to the nose member, a rotor attached to the projectile body, and rotational support hardware interconnecting the stator to the rotor. The stator defines a central axis. The rotational support hardware is constructed and arranged to guide rotation of the rotor around the central axis defined by the stator. Such a guidable projectile enables circuitry such as the driver of the stator and the power source to reside at fixed locations relative to the stator thus alleviating the need for slip rings which would otherwise present potential points of failure.
The foregoing and other objects, features and advantages will be apparent from the following description of particular embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of various embodiments of the invention.
Improved nose articulation techniques involve utilization of (i) a stator which attaches to a nose member (e.g., a nose cone of a guidable projectile) and (ii) a rotor which attaches to a projectile body (e.g., a main casing of the guidable projectile). Accordingly, the stator and the rotor form a motor/generator which is capable of (i) controlling rotation of the projectile body relative to the nose member as well as (ii) generating electrical power. Moreover, electrical control of the stator and other electrical or electromechanical components (e.g., a nose cone actuator) are capable of residing at fixed locations relative to the stator (e.g., on the stator spindle) thus alleviating any need to convey electrical power and electrical control signals from the projectile body to the stator or to the nose member through slip rings.
As shown in
As will be explained in further detail shortly, the rotational support hardware 36 includes bearings and specialized components and geometries which cooperatively unload extreme G-force stresses (e.g., high-G shock pulses encountered during a cannon launch condition) from the bearings. These specialized components and geometries nevertheless provide collapsible energy absorbing interfaces under lower G-force stresses.
As further shown in
The nose member articulation assembly 22 further includes a nose member actuator 50 having a base 52, an arm 54 and a motor 56 (shown generally by the arrow 56 in
During operation, a launch system (e.g., a cannon) is capable of firing the guidable projectile 20 in the positive Z-direction. In this situation, the entire guidable projectile 20 spins or rifles in a particular rotational direction around the Z-axis (e.g., clockwise when viewed facing the nose member 24 of the guidable projectile 20). The control circuitry 38 is then capable of operating the motor/generator 42 in the opposite direction to that of the guidable projectile 20 (e.g., in the counterclockwise direction when viewed facing the nose member 24 of the guidable projectile 20) to slow (i.e., “de-spin”) and eventually stop the stator 32 and the nose member 24 from rotation relative to the earth. In particular, an inertial guidance system is capable of providing input to the control circuitry 38 to direct the motor 42 to provide a proper amount of rotation in the opposite direction so that the stator 32 and the nose member 24 are no longer substantially rotating relative to points on the ground.
Once the motor/generator 42 has de-spun the stator 32 and the nose member 24 relative to the ground, the stator 32 and the nose member 24 are essentially in a geostatic orientation in terms of rotation. In this situation, the inertial guidance system is capable of directing the control circuitry 38 to modify the angular displacement (or tilt) of the nose member 24 and is thus capable of controlling the trajectory of the guidable projectile 20 while the guidable projectile 20 is in flight.
For example, suppose that the guidable projectile 20 is in substantially horizontal flight and that the stator 32 is in the orientation shown in
It should be understood that the above-described guidable projectile 20 is suitable for a variety of applications including guided rockets, guided missiles, guided torpedoes, and similar guidable objects. In some arrangements, the nose member 24 defines a space 60 which is capable of supporting a payload (e.g., an inertial guidance system, sensors, other electronics, an explosive charge, etc.). Similarly, in some arrangements, the projectile body 26 defines a space 62 which is capable of supporting another payload (e.g., a propulsion system, an explosive charge, etc.).
It should be further understood that containment of the motor stator 32, control circuitry 38 and other control electronics (e.g., batteries, an inertial guidance system in the space 60 defined by the nose member 24, etc.) is capable of occurring exclusively on the stator 32 and/or the nose member 24. Accordingly, there is no need to convey electrical signals from the rotor 34 or the projectile body 26. As a result, no slip rings are required to power or control the motor/generator 42. Further details will now be provided with reference to
Additionally, the stator shaft 102 is rotationally static with respect to the nose member 24. That is, the stator shaft 102 is capable of rotating relative to the rotor 34 about the central axis 40 in unison with the nose member 24. Furthermore, the nose member 24 is capable of pivoting relative to the stator shaft 102 about a hinge 106 which extends along the X-axis in
The rotor 34 of the motor/generator 42 includes a rotor housing 108 and a set of magnets 110. The rotor housing 108 rigidly supports the magnets 110. The rotor housing material is composed of a soft magnetic material (i.e., material with low magnetic permeability), such as iron or steel to close the electromagnetic flux path between the opposite poles of the magnet. Alternatively, the magnets are supported within the inside diameter of a ring of soft magnetic material which is secured to the rotor housing. In some arrangements, the material of the rotor housing 108 has soft magnetic properties so that the rotor housing 108 acts as the back iron for the magnets 110. Alternatively, rare earth magnets, ring magnets, Samarium-Cobalt magnets, and so on are capable of being used.
It should be understood that there is a motor/generator relationship between the windings 104 of the stator 32 and the magnets 110 of the rotor 34. Along these lines, during operation, the control circuitry 38 of the motor/generator 42 is constructed and arranged to control electric current through the windings 104 of the stator 32 (e.g., commutation) and thus control rotation of the rotor 34 around the stator 32. Such motorized operation enables the stator 32 and the nose member 24 to remain stationary from a rotational standpoint relative to the ground during flight, while the rotor 34 and the projectile body continue to rotate around the central axis 40 (e.g., at several thousands of rotations per minute).
Although power cells have been omitted from
As further shown in
It should be understood that the nose member actuator 50 is capable of being implemented as a drive screw actuator 120 and a crank arm 122. In this situation, the nose member 24 preferably can rotate up to 12 degrees from the central axis 40 in any direction due to operation of the drive screw actuator 120 (for tilting about the hinge 106) and further due to operation of the motor/generator 42 (for orientation of the stator shaft 102 around the central axis 40).
In some arrangements, the control circuitry 38 includes a two-channel drive circuit 124 having a first channel to drive the motor/generator 42, and a second channel to drive the nose member actuator 50. In these arrangements, the control circuitry 38 preferably receives signals from position sensors (e.g., Hall effect sensors) for feedback control. Since the control circuitry 38 resides at a fixed mounting location on the stator shaft 102 and electrically connects to both the motor/generator 42 and the nose member actuator 50 which are also at fixed mounting locations on the stator shaft 102, there is no need for any slip rings to convey electrical signals there between.
As further shown in
The rotation support hardware 36 further includes a set of energy absorbing interfaces 146 (e.g., Belleville springs, tolerance rings, etc.) which provide dampening and cushioning between the stator shaft 102 and the rotor housing 108. As will be discussed in further detail shortly, the stator shaft 102 defines a set of unloading surfaces 148. These unloading surfaces 148 are arranged to make contact with the rotor housing 108 to prevent overloading of the bearings 140 and the energy absorbing springs 146 when the guidable projectile 20 undergoes extreme acceleration (e.g., acceleration above a predefined threshold) in various directions such as in the positive Z-direction when the guidable projectile 20 is launched from a cannon. Further details will now be provided with reference to
As further shown in
By way of example only, the power cells 208, which provides power to operate the motor/generator 42 and the nose member actuator 50, is shown as being contained within a hollow but enclosed cavity 210 defined by the stator shaft 102. Since the power cells 208 in combination with the motor/generator 42 are constructed and arranged to provide ample power to control rotation of the motor/generator 42 and operation of the nose member actuator 50 during flight of the guidable projectile 20, there no need for slip rings to convey electrical signals. Further details will now be provided with reference to
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It should be understood that balancing between the axial displacement loading springs 400, 500 maintains both the axial gap 404 (
In contrast, when the guidable projectile 20 undergoes extreme high G-force acceleration in the positive Z-direction, the unloading surface 402 defined by the stator shaft 102 contacts the corresponding surface 406 defined by the rotor housing 108. Such a situation may exist during launching of the guidable projectile 20 from a cannon. During such a situation, the axial displacement loading springs 400 deform to allow direct contact between the stator shaft 102 and the rotor housing 108. As a result, the bearings 104(R) are protected against overloading and damage.
It should be understood that additional axial gaps, which are similar to the axial gap 404, may be distributed between the stator shaft 102 and the rotor housing 108. Such distributed placement of these additional axial gaps spreads out the contact surface area between the stator shaft 102 and the rotor housing 108 to reduce stresses at any particular point. By way of example,
It should be further understood that, when the guidable projectile 20 undergoes extreme high G-force acceleration in the negative Z-direction, the unloading surface 502 defined by the stator shaft 102 contacts the corresponding surface 506 defined by the rotor housing 108. Here, the axial displacement loading springs 500 again deform to allow direct contact between the stator shaft 102 and the rotor housing 108. Accordingly, the bearings 104(F) are protected against overloading and damage.
Additionally, and as shown in
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It should be understood that the radial displacement loading springs 420, 520 maintain the radial gap 424 (
In contrast, during situations of substantial radial acceleration which causes significant radial displacement, one or more of the unloading surfaces 422, 522 defined by the stator shaft 102 contact the corresponding one or more surfaces 426, 526 defined by the rotor housing 108. That is, the radial displacement loading springs 420, 520 deform to allow direct contact between the stator shaft 102 and the rotor housing 108. As a result, the bearings 104(R), 104(F) are protected against damage. Such operation prevents overloading of the bearings 104(R), 104(F) when radial acceleration exceeds a predetermined threshold.
Based on the above, it should be understood that an example set of predefined thresholds is that set of thresholds which enables the various load bearing elements (e.g., the bearings 140) to survive the extreme loading encountered during a cannon launch of a guided missile. Such an extreme loading condition may last only for a split second but provide many thousands of pounds of force. For example, in the context of 20,000 to 30,000 G's on a four pound component, there could otherwise be 80,000 pounds of force on the load bearing elements without protection. To prevent such force from destroying the load bearing elements, the collapsible energy absorbing interfaces of the rotational support hardware 36 and the gaps between the unloading surfaces and corresponding surfaces are such that the load bearing elements (i) operate by bearing the load in normal conditions (i.e., G-forces well under 20,000 to 30,000 G's) but (ii) are shielded from damage during the extreme loading conditions.
As mentioned above, improved nose articulation techniques involve utilization of (i) a stator 32 which attaches to a nose member 24 (e.g., a nose cone of a guidable projectile) and (ii) a rotor 34 which attaches to a projectile body 26 (e.g., a main casing of the guidable projectile). Accordingly, the stator 32 and the rotor 34 form a motor/generator 42 which is capable of (i) controlling rotation of the projectile body 26 relative to the nose member 24 as well as (ii) generating electrical power. Moreover, electrical control of the stator 32 and other electrical or electromechanical components (e.g., a nose cone actuator) are capable of residing at fixed locations 206 relative to the stator 32 (e.g., on the stator shaft 102) thus alleviating any need to convey electrical power and electrical control signals from the projectile body 26 to the stator 32 or to the nose member 24 through slip rings.
It should be understood that the above-described nose articulation techniques are well suited for a variety of applications such as one that involves maneuvering a body using a motor rotational in one direction to move an aerodynamic device in an oscillating motion. A similar application is described in U.S. application Ser. No. 11/651,864, entitled “ECCENTRIC DRIVE CONTROL ACTUATION SYSTEM”, the teachings of which are hereby incorporated by reference in their entirety.
While various embodiments of the invention have been particularly shown and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
For example, the nose member articulation assembly 22 was described above as being well-suited for guided missile applications. It should be understood that the nose member articulation assembly 22 is a mechanism that enables conversion of an existing “dumb” artillery round or a legacy dumb round design into a “smart” round. In particular, one is capable of making a dumb round smart by attaching the nose member articulation assembly 22 to the front of the dumb round. Alternatively, one is capable of making a smart round by interconnecting the nose member articulation assembly 22 between (i) the nose, or fuse, of the dumb round and (ii) the following body which carries the explosive charge or other payload of the dumb round.
Additionally, it should be understood that the axial displacement loading springs were described above as Belleville springs by way of example only. Other loading springs are suitable for use as well such as finger springs, wave spring washers, curved springs, tab washers, notch washers, and the like.
Similarly, it should be understood that the radial displacement loading springs were described above as tolerance rings by way of example only. Other loading springs are suitable for use as well such as washers, leaf springs, circular suspensions, and the like.
