In-flight programming of trigger time of a projectile
The present invention describes methods for programming trigger time of a projectile ( 60 ) based on remaining flight time to a target (P) after the projectile ( 60 ) is airborne. The actual muzzle (Vo) and flight speeds (V 1 , V 2 , etc.) are independently determined and compared to those used by the ballistic computer ( 30 ), and a better estimate of trigger time is accordingly used to activate detonation of the projectile ( 60 ). In one embodiment, a Kalman algorithm is used to provide a better estimate of the projectile's flight speeds obtained by independent methods to provide the better estimate of the trigger time.
1. A method of programming a trigger time of a projectile, the method comprising:
determining a muzzle velocity of a projectile after said projectile exits from an associated gun barrel;
determining an flight speed of the projectile a predetermined time after said projectile has been fired; and
accounting for the deviation of the projectile's muzzle velocity and flight speed from those determined by an associated ballistic computer and programming the trigger time during the remaining flight time as the projectile is reaching its target, thereby optimizing the effectiveness of the projectile;
wherein determining said projectile's muzzle velocity and flight speed comprises emitting a signal from said projectile at relevant predetermined time after said projectile is fired and determining strength of said signal received by an antenna connected to said ballistic computer, and calculating said projectile's speeds from signal strength-distance data stored in said ballistic computer.
2. A method according to claim 1 , further comprising determining the projectile's muzzle velocity and flight speed by a flow sensor at relevant predetermined time after the projectile is fired.
3. A method according to claim 2 further comprising determining the projectile's muzzle velocity and flight speed by integrating the projectile's acceleration with time of flight by a MEMs accelerometer.
4. A method according to claim 2 or 3 , wherein results of determining the projectile's muzzle velocity and flight speed are transmitted back to said ballistic computer.
5. A method according to claim 4 , wherein the projectile's muzzle velocity and flight speed determined by independent processes are combined with reliability weighting factors.
6. A method according to claim 4 , wherein the projectile's muzzle velocity and flight speed determined by independent processes are recursively obtained by employing a Kalman filtering algorithm.