Virtual Roll Gyro for Spin-Stabilized Projectiles

Abstract

A method is described for determining roll rate for a spin-stabilized projectile. A yaw signal and a pitch signal are measured for the projectile, wherein: (i) for a trajectory path being travelled by the projectile over the Earth's surface, projectile stability is created by spinning of the projectile about a longitudinal spin axis oriented tangent to the projectile trajectory, (ii) the yaw signal represents yaw motion of the projectile about a yaw axis oriented along a line through the Earth's center and orthogonal to the spin axis, and (iii) the pitch signal represents pitch motion of the projectile about a pitch axis orthogonal to the spin axis and the yaw axis, and wherein the yaw signal and the pitch signal are modulated by spin rate of the projectile spinning about the spin axis. A roll rate signal is extracted from one of the yaw signal and the pitch signal.

What is claimed is: 
     
         1 . A computer-implemented method employing at least one hardware implemented computer processor for determining roll rate for a spin-stabilized projectile, the method comprising:
 operating the at least one hardware processor to execute program instructions to: measure a yaw signal and a pitch signal for the projectile, wherein:
 (i) for a trajectory path being travelled by the projectile over the Earth's surface, projectile stability is created by spinning of the projectile about a longitudinal spin axis oriented tangent to the projectile trajectory, 
 (ii) the yaw signal represents yaw motion of the projectile about a yaw axis oriented along a line through the Earth's center and orthogonal to the spin axis, 
 (iii) the pitch signal represents pitch motion of the projectile about a pitch axis orthogonal to the spin axis and the yaw axis, and
 wherein the yaw signal and the pitch signal are modulated by spin rate of the projectile spinning about the spin axis; 
 
   extract a roll rate signal from one of the yaw signal and the pitch signal; and   provide the yaw signal, the pitch signal, and the roll rate signal to an inertial measurement unit (IMU) configured to control orientation of the projectile with respect to the trajectory path.   
     
     
         2 . The method according to  claim 1 , wherein the yaw signal is measured by a yaw gyroscopic sensor within the projectile. 
     
     
         3 . The method according to  claim 1 , wherein the pitch signal is measured by a pitch gyroscopic sensor within the projectile. 
     
     
         4 . The method according to  claim 1 , wherein the roll rate signal is extracted by detecting zero crossings of one of the yaw signal and the pitch signal. 
     
     
         5 . The method according to  claim 1 , wherein the roll rate signal is extracted by deconvolving one of the yaw signal and the pitch signal. 
     
     
         6 . The method according to  claim 1 , wherein the IMU is configured to measure the yaw signal and the pitch signal. 
     
     
         7 . The method according to  claim 1 , wherein the IMU is configured to extract the roll rate signal. 
     
     
         8 . A non-transitory tangible computer-readable medium having instructions thereon for determining roll rate for a spin-stabilized projectile, the instructions comprising:
 program code for measuring a yaw signal and a pitch signal for the projectile, wherein:
 i. for a trajectory path being travelled by the projectile over the Earth's surface, projectile stability is created by spinning of the projectile about a longitudinal spin axis oriented tangent to the projectile trajectory, 
 ii. the yaw signal represents yaw motion of the projectile about a yaw axis oriented along a line through the Earth's center and orthogonal to the spin axis, 
 iii. the pitch signal represents pitch motion of the projectile about a pitch axis orthogonal to the spin axis and the yaw axis, and 
 wherein the yaw signal and the pitch signal are modulated by spin rate of the projectile spinning about the spin axis; 
   program code for extracting a roll rate signal from one of the yaw signal and the pitch signal; and   program code for providing the yaw signal, the pitch signal, and the roll rate signal to an inertial measurement unit (IMU) configured to control orientation of the projectile with respect to the trajectory path.   
     
     
         9 . The computer-readable medium according to  claim 8 , wherein the yaw signal is measured by a yaw gyroscopic sensor within the projectile. 
     
     
         10 . The computer-readable medium according to  claim 8 , wherein the pitch signal is measured by a pitch gyroscopic sensor within the projectile. 
     
     
         11 . The computer-readable medium according to  claim 8 , wherein the roll rate signal is extracted by detecting zero crossings of one of the yaw signal and the pitch signal. 
     
     
         12 . The computer-readable medium according to  claim 8 , wherein the roll rate signal is extracted by deconvolving one of the yaw signal and the pitch signal. 
     
     
         13 . The computer-readable medium according to  claim 8 , wherein the IMU is configured to measure the yaw signal and the pitch signal. 
     
     
         14 . The computer-readable medium according to  claim 8 , wherein the IMU is configured to extract the roll rate signal.