Abstract:
A missile nose is tiltable and rotatable relative to a missile body through the action of an actuator system. In an exemplary embodiment, the actuator systems uses two electro-mechanical actuators mounted co-axially and having the output shaft of one actuator fed through the shaft of the other. One of the actuators controls a tilt angle between a longitudinal axis of the body and a longitudinal axis of the nose. The other actuator rotates the nose about the longitudinal axis of the body. A method of steering a missile includes using the actuator system to maintain the missile nose pointed at a target or other desired destination.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field of the Invention 
     The invention relates to directional control systems and methods for missiles. 
     2. Description of the Related Art 
     Steering control of missiles may be achieved by deflecting a set of control surfaces attached to the rear of the missile body, each control surface having its own respective control actuator to provide the necessary deflection torque. However, a class of missiles and projectiles exists for which this approach is inadequate, due to the relatively large volume and increased package size for separate deflectable control surfaces. In the past, canards, jet plume diverters, and articulated nose controls have been used as alternatives to rear-body control surface steering. However, canards may have the disadvantage of requiring unacceptable amounts of external volume, thereby creating difficulties for missile storage and/or launch. In some such cases, the canards may be designed as folding or “pop-out” control surfaces; however, this often adds significant complexity, cost, and missile volume. 
     Jet divert mechanisms may have the disadvantages of being able to provide only a discrete nature of control, of inducing increased drag, and/or of inducing oscillations in the missile. 
     In many applications, nose control may provide significant advantages over either rear steering, canard, or jet divert designs. The articulated nose may provide steering with minimal effect on the external missile/projectile packaging, minimum drag characteristics, and smooth, continuous steering. It is understood that a simple steering mechanism can be achieved by always pointing the nose toward the target, therefore allowing resulting aerodynamic forces to fly the missile toward the target. 
     Prior actuation implementation systems to effect nose deflection or articulation have generally utilized pyrotechnic, piezo-electric, or electro-magnetic actuators. An exemplary prior art pyrotechnic nose cone actuation system contains two banks of pyrotechnic actuating cylinders, each of the cylinders attached to an individual ignitor. Actuation is achieved by firing the cylinders to extend and lock a corresponding piston, thereby causing angular deflection of a pivot-mounted nose cone. Pyrotechnic systems have the disadvantage of being discrete by nature, since they typically require the firing of a piston to full stroke. Therefore, changes in the nose cone deflection are discrete and sudden. Small trajectory errors are therefore more difficult to correct and accuracy is correspondingly diminished. 
     An exemplary piezo-electric actuated nose cone contains a pair of piezo-actuators for each desired axis of nose deflection or articulation. Such piezo-actuators are relatively fragile and are typically limited to providing small displacements. Therefore, such actuation systems are typically restricted to applications where small nose deflections are acceptable. 
     It will be appreciated from the foregoing that improved mechanisms and methods for steering a missile are needed. 
     SUMMARY OF THE INVENTION 
     A missile nose is tiltable and rotatable relative to a missile body through the action of an actuator system. In an exemplary embodiment, the actuator system uses two electromechanical actuators mounted co-axially and having the output shaft of one actuator fed through the shaft of the other. One of the actuators controls a tilt angle between a longitudinal axis of the body and a longitudinal axis of the nose. The other actuator rotates the nose about the longitudinal axis of the body. A method of steering a missile includes using the actuator system to maintain the missile nose pointed at a target or other desired destination. 
     According to an aspect of the invention, a missile includes a pair of rotary actuation devices for positioning a missile nose relative to a missile body. 
     According to another aspect of the invention, a missile includes a pair of actuators for positioning a missile nose relative to a missile body, at least part of one of the actuators being co-axial with at least part of the other actuator. 
     According to yet another aspect of the invention, a missile includes a pair of actuators for positioning a missile nose relative to a missile body, at least part of one of the actuators nested in at least part of the other actuator. 
     According to still another aspect of the invention, a missile includes a tilt actuator for tilting a nose of the missile relative to a body of the missile, the tilt actuator including a rotary actuation device operatively coupled to a translatable member. 
     According to a further aspect of the invention, a missile includes an actuator system for articulating a nose of the missile relative to a body of the missile, at least part of the actuator system being located in a nose cavity of the nose. 
     According to a still further aspect of the invention, a missile includes an a pair of actuators for articulating a nose of the missile relative to a body of the missile, at least part of each of the actuators being located in a nose cavity of the nose. 
     According to another aspect of the invention, a missile includes a missile nose having a longitudinal nose axis; and a missile body having a longitudinal body axis, the body including an actuator system hingedly coupled to the nose at a central connection on the nose which is at an intersection between the longitudinal nose axis and the longitudinal body axis. The actuator system is operationally configured to rotate the nose about the longitudinal body axis relative to the body. 
     According to yet another aspect of the invention, a missile includes means for tilting a missile nose relative to a missile body in a fixed plane relative to the body, and means for rolling or spinning the missile. 
     According to still another aspect of the invention, a missile includes a missile nose and a missile body which includes a tilt actuator with a translatable member mechanically linked to an offset connection point on the nose. The offset connection point is offset from a longitudinal body axis. 
     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 
     According to annexed drawings: 
     FIG. 1 is a partial-section perspective view of a missile embodying the present invention; 
     FIG. 2 is a side sectional view of the missile of FIG. 1; 
     FIG. 3 is a schematic view of the control system of the missile of FIG. 1; and 
     FIG. 4 is a schematic view of an alternate missile which embodies the present invention. 
    
    
     DETAILED DESCRIPTION 
     Referring to FIGS. 1 and 2, a missile  10  has a missile body  12  and a missile nose  14 . The body  12  includes an actuator system  18  for articulating the nose  14  relative to the body. As described in greater detail below, the actuator system  18  includes a pair of actuators co-axial with one another, at least part of one of the actuators being nested within at least part of the other actuator. The actuator system  18  includes a tilt or deflection actuator  20  and a rotation actuator  22 . 
     The tilt actuator  20  operates to control an angle of deflection a between a nose longitudinal axis  26  of the nose  14  and a body longitudinal axis  28  of the body  12 . The rotation actuator  22  is operable to rotate the nose  14  relative to the body  12 . For example, the rotation actuator  22  may control rotation of the nose  14  about the longitudinal body axis  28 . 
     The tilt actuator  20  includes a rotary actuation device such as a motor  30 . The motor  30  or a shaft of the motor is coupled to rotate a lead screw  32  having a threaded exterior surface  36 . A translatable member such as a lead nut  38  is operatively coupled to the lead screw  32 , the lead nut  38  having a threaded interior surface  40 . Rotation of the lead screw  32  therefore results in translation of the lead nut  38  along the lead screw  32 . The lead screw  32  and the lead nut  38  are for the most part located in a central cavity such as a central bore  44  of a hinge mount shaft  46 . However, a protruding portion  50  of the lead nut  38  protrudes through a slot  52  in the hinge mount shaft  46 . A nut-nose link  54  is hingedly coupled, at a first end  56 , to the protruding portion  50  at a hinged nut connection  58 . The link  54  is hingedly connected at its opposite end  59  to an L-shaped member  60  of the nose  14 . The hinged coupling between the nut-nose link  54  and a short arm  62  of the L-shaped member  60  occurs via a hinged nose connection  66  at an offset connection point  68  on the L-shaped member which is offset from the longitudinal body axis  28 . The hinged connections  58  and  66  may include suitable well-known connecting devices, for example, rivets, nut-and-bolt connections, or pins. 
     At the junction of the short arm  62  and a long arm  70  of the L-shaped member is a central connection point  72 , where the L-shaped member  60  is hingedly coupled to the hinge mount shaft  46  via a hinge pin  74 . The central connection point  72  and the hinge pin  74  are located at the junction of the longitudinal axes  26  and  28 . However, it will be appreciated that alternatively the central connection point  72  and the hinge pin  74  may be located other than at the juncture of the axes  26  and  28 , if desired. The long arm  70  attaches the L-shaped member  60  to a nose shell  78 . As illustrated, the long arm  70  is along the nose longitudinal axis  26 . However, it will be appreciated that other couplings may alternatively be used between connection points of the nose and an outer body or nose shell of the nose. 
     The tilt actuator  20  operates as follows to control the angle α of deflection between the longitudinal axes  26  and  28 . Operation of the motor  30  causes rotation of the lead screw  32 , which in turn causes translation of the lead nut  38  along the lead screw. Translation of the lead nut  38  causes corresponding movement of the end  56  of the nut-nose link  54 , via their coupling at the hinged nut connection  58 . This in turn initiates movement of one end of the short arm  62  of the L-shaped member  60 , the link  54  and the short arm being coupled at the offset connection point  68  of the short arm  62  via the hinged nose connection  66 . The hinge mount shaft  46  is unmoved by the above actions, the lead nut  38  slidably moving along the surface of the central bore  44  of the hinge mount shaft. Since the hinge mount shaft  46  is unmoved by actuation of the tilt actuator  20 , the hinge pin  74  likewise does not move, and the central connection point  72  therefore acts as a pivot point for rotation of the nose  14  relative to the body  12 . Movement of the offset connection point  68  thereby changes the angle a between the longitudinal axes  26  and  28 , effecting tilting or deflecting of the nose  14  relative to the body  12 . 
     A stop  80  is provided on the lead screw  32  opposite the motor  30 . The stop  80  limits travel of the lead nut  38 , and may be fixedly attached to the lead screw or may alternatively be otherwise suitably coupled to the lead screw. 
     It will be appreciated that many variants of the above-described design may alternatively be employed. For example, as noted above, the central connection point  72  may be other than at the junction of the longitudinal axes  26  and  28 , if desired. The central connection point  72  and the offset connection point  68  may be parts of separate structures attached to the nose shell  78 , rather than being holes in a single member such as the L-shaped member  60 . A variety of suitable rotary actuation devices may be employed in place of the motor  30 , and the motor  30  may have any of a wide variety of suitable, well-known designs and/or configurations. The linkage between the motor  30  and the connection points  68  and  72  of the nose  14  may alternatively be other than as shown. It will further be appreciated that the translatable member may be translated by other suitable means, for example by coupling the translatable member to a fluid actuator. It will be appreciated as well that many alternative types of linkages may be provided between the translatable member and the nose for deflecting the nose longitudinal axis  26  relative to the body longitudinal axis  28 . For example, the linkages may involve couplings utilizing various suitable combinations of gears, belts, translating members, and/or rotating members. 
     The rotation actuator  22  includes a rotary actuation device such as a rotary motor  84 . The rotary motor  84  controls rotary movement of extensions  86  which are a part of, or are coupled to, the hinge mount shaft  46 . The rotary motor  84  is thus able to control rotation of the hinge mount shaft  46 . Rotating the hinge mount shaft  46  causes rotation of the hinge pin  74 , and thus rotation of the nose  14 . Since the hinge mount shaft  46  is centered on the body longitudinal axis  28 , the rotation of the nose  14  by movement of the extensions  86  is also rotation about the body longitudinal axis  28 . 
     It will be appreciated that the rotary motor  84  may be operatively coupled to the motor  30  to allow compensation for translation of the lead nut  38  resulting from rotation of the lead nut caused by the rotation actuator  22 . 
     It will further be appreciated that the motor  30  and the rotary motor  84  may be operatively coupled to any of a variety of well-known encoders to facilitate determination of nose position. One such encoder may be placed between the lead screw  32  and the hinge mount shaft  46  to measure differential rotation, thereby providing nose angular position with respect to the missile body axis. Alternatively or in addition, an encoder may be placed between the hinge mount shaft  46  and the missile body  12 , providing nose roll angle position with respect to the missile body. 
     It will be appreciated that many variations to the above-described rotation actuator  22  will occur to one skilled in the art. It will further be appreciated that parts of the actuators  20  and  22  may be made of well-known materials, for example metallic materials such as steel. 
     As shown in FIGS. 1 and 2, all or portions of the tilt actuator  20  and/or the rotation actuator  22  may be within a nose cavity  88  in the nose  14 , thus providing for better utilization of the interior volume of the missile  10 . 
     It will be appreciated that the rotation actuator  22  may be used to maintain the nose  14  of the missile  10  in a constant direction, compensating for rotation of the missile body  12 . Alternatively or in addition, the rotation actuator  22  may be used to change and/or control the orientation of the plane defined by the longitudinal axes  26  and  28 . 
     Referring now to FIG. 3, a schematic diagram is shown of one possible control system for the missile  10 . A controller  90  is operatively coupled to the motor  30 , the rotary motor  84 , a target tracking device  92  for tracking a target or desired course of the missile  10 , and a roll-rate sensor  94  for sensing roll of the missile body  12 . 
     The motor  30  and the rotary motor  84  are used as described above in the operation of the tilt actuator  20  and the rotation actuator  22 , respectively. The target tracking device  92  may be one of a variety of well-known suitable devices for acquiring and/or tracking a target, and/or for analyzing the position, orientation, and/or the speed of the missile  10  to determine its course relative to the location of a target or other destination. The roll-rate sensor  94  is one of a variety of well-known devices for determining the roll rate of the missile  10 . The controller  90  is a suitable device for receiving and processing data, and for sending control signals, for example including a microprocessor. 
     It will be appreciated that alternatively some or all of the controller  90 , the target tracking device  92 , and the roll-rate sensor  94  may be located outside the body  12 . For example, one or more may be located in the missile nose  14 . Alternatively, one or more may be located external to the missile, operative coupling of the control system in such a case being made by suitable means, for example, by use of a signal propagating along a wire, or by signals such as radio waves which do not require a solid connection for propagation. 
     The actuator system  18  of the missile  10  described above may be used to articulate the nose  14  of the missile toward a designated target or along a designated course. This simple nose control or articulation steering mechanism results in appropriate aerodynamic forces to fly the missile toward the target. The actuator system  18  described above provides advantages over prior art systems in that it requires only a small diameter because the tilt actuator  20  and the rotation actuator  22  are coaxial, one being in part nested in part of the other. Moreover, the actuator system  18  described above provides simple means for compensating for rotation of the missile body. 
     What follows now is an alternate embodiment of the invention. The details of certain common similar features between the alternate embodiment and the embodiment or embodiments described above are omitted in the description of the alternate embodiments for the sake of brevity. It will be appreciated that features of the alternate embodiment may be combined with features of the embodiment or embodiments described above. 
     Turning now to FIG. 4, a missile  210  is shown which has a simplified actuator system  218  for articulating a missile nose  214  relative to a missile body  212 . The actuator system  218  includes a tilt actuator  220  for tilting the nose  214  relative to the missile body  212 . The tilt actuator  220  may be similar to the tilt actuator  20 , and may include a motor  230  which is similar to the motor  30  described above, as well as including other components similar to those described above. 
     The missile  210  may contain a control system to control actuation of the actuator system  218 , for example having a controller  290 , a target tracking device  292 , and a roll-rate sensor  294 . 
     The missile  210 , lacking a rotation actuator corresponding to the rotation actuator  22  of the missile  10 , is only able to articulate the nose  214  relative to the missile body  212  in a single, fixed plane. However, for a missile that is undergoing roll, either a steady roll or variable-speed roll, articulation of the nose in a single plane may provide adequate steering control. The controller  290  may be configured to move the nose  214  relative to the body  212  at a rate corresponding to the roll rate of the missile  210 , thereby maintaining the nose approximately pointed in the direction of a target for the missile. It will be appreciated that the controller  290  may be configured to move the nose  214  in synchronization with a predetermined roll rate, or that alternatively the controller  290  may move the nose  214  in response to signals from the roll-rate sensor  294 . 
     Many well-known means exist for imparting a spin or roll rate to a missile, for example by use of canted fins, spiral grooves in a launch tube, and/or turning vanes in a nozzle of a rocket motor. 
     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.