Three Axis Aerodynamic Control of Guided Munitions

Abstract

An apparatus for 3-axis aerodynamic control of multi-caliber bodies comprising three shafts each having at least one canard; bevel gears attached to said shafts; and a set of three miniature stepper motors, each driving a zero backlash spur assembly attached to the drive bevel gears.

1 . An apparatus for three axis aerodynamic control of a body while in flight, said apparatus comprising: 
 first, second and third shafts;    a canard attached to spaced ends of the first shaft;    a canard attached to one end of each of the second and third shafts,    a gear assembly operatively connected to each of the shafts;    a drive motor for driving each of the shafts through the gear assemblies; and    a controller operatively connected to each of the drive motors for integration of guidance controls to the canards to steer the body.    
   
   
       2 . The apparatus defined in  claim 1  wherein the gear assembly includes a planetary gear, a worm gear and a pitch gear.  
   
   
       3 . The apparatus defined in  claim 2  wherein the planetary gear is connected between the drive motor and the worm gear; and in which the pitch gear is connected between the worm gear and the canard shaft.  
   
   
       4 . The apparatus defined in  claim 2  wherein the planetary gear has a gear ratio of approximately 256/1.  
   
   
       5 . The apparatus defined in  claim 4  wherein the planetary gear has an output torque of approximately 1.77 in/lb.  
   
   
       6 . The apparatus defined in  claim 1  wherein each of the drive motors is a high torque two phase stepper motor.  
   
   
       7 . The apparatus defined in  claim 6  wherein the stepper motors have a generally 18 degree step size; and in which the gear assembly is a generally 30/1 zero backlash spur reduction gear assembly.  
   
   
       8 . The apparatus defined in  claim 2  wherein a fold pivot and a pivot lock is located between the gear assembly and canard when the canard is a retractable canard.  
   
   
       9 . The apparatus defined in  claim 1  wherein each of the canards have a double wedge configuration consisting of first and second wedges with symmetrical surfaces and with a pivot located at a junction of said wedges, said junction being the longitudinal center of pressure of the canard providing torque balanced aerodynamic surfaces for said canards.  
   
   
       10 . The apparatus defined in  claim 9  wherein the junction of the canard is the thickest portion of the canard; and in which the first and second wedges taper inwardly outwardly from said junction.  
   
   
       11 . The apparatus defined in  claim 1  wherein a Ram Air Turbine (RAT) and a safe/arm rotor assembly are mounted in the body to prevent errant rounds from exploding.  
   
   
       12 . The apparatus defined in  claim 1  wherein the gear assembly includes a spur gear operatively connected to the drive motor and a bevel gear operatively connected between the spur gear and each of the shafts.  
   
   
       13 . The apparatus defined in  claim 12  wherein the spur gear is a zero backlash reduction assembly.  
   
   
       14 . A guided munition comprising: 
 a projectile body;    a stabilizing fin assembly mounted at the rear of the projectile body;    a guidance assembly mounted in a forward end of the projectile body, said guidance assembly including: 
 a) at least four canards movably mounted with respect to the projectile body,  
 b) a first shaft having first and second of said canards mounted on respective ends of said first shaft,  
 c) a second shaft having a third of said canards mounted thereon,  
 d) a third shaft having a fourth of said canards mounted thereon;  
 e) an optical sensor mounted in the projectile body; and  
 f) a controller operatively connected to each of the three shafts for independently rotating said shafts to move said canards to change the ballistic path of said projectile body in response to guidance signals received from the optical sensor.  
   
   
   
       15 . The guided munition defined in  claim 14  wherein the controller is a Proportional-Integral-Derivative (PID) controller.  
   
   
       16 . The guided munition defined in  claim 14  wherein the optical sensor is an array of optical detectors located in a forward part of the projectile body.  
   
   
       17 . The guided munition defined in  claim 14  wherein the controller is connected to each of the shafts by a stepper motor and a gear assembly.  
   
   
       18 . The guided munition defined in  claim 19  wherein each of the gear assemblies includes a planetary gear connected to the stepper motor, and a worm gear located between and operatively connected to the planetary gear and a pitch gear, said pitch gear being attached to the shaft.  
   
   
       19 . The guided munition defined in  claim 17  wherein each of the gear assemblies includes a spur gear operatively connected to the drive motor and a bevel gear operatively connected between the spur gear and each of the shafts.  
   
   
       20 . The guided munition defined in  claim 14  wherein the front end of the projectile body is a conical nose; in which the four canards are rotationally non-foldably mounted on the nose and are located within an imaginary cylinder defined by the projectile body.