Sensor fusion for low cost small caliper ammunition guidance

 

FotoDAFORNO 1Roberto Da Forno, Ph.D

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ABSTRACT

The trajectory control for small caliber projectiles (mortars, RPGs, grenades 40) are taking an increasingly important role in the reduction of collateral effects, by reducing the CEP (Circular Error Probable).
The cost reduction is the main objective given the large numbers that characterize the small-caliber ammunition.
The state of the art shows applications where the navigation system is integrated in the projectile body. In this paper we present an "add-on" solution where the guidance system is fixed to the ogive, using four canard as aerodynamic surfaces, therefore the proposed solution is independent on the manufacturer of the projectile with great advantage regarding the flexibility.
The sensors are sampled with variable frequency: 10 Hz GPS, barometric altimeter, accelerometers, gyroscope are sampled at 100 Hz. The attitude of the rigid body is determined by complementary filter which combines the measurement of acceleration and angular velocity. The advantage over the Kalman filter is the so-called "cold start" the complementary filter immediately provides the measure, while the Kalman filter requires a start-up period to identify the state of the system. For tactical applications the fast cold start is undoubtedly very important.
The measurement / control hw (CPU, 3 acc., 3 gyro, altimeter) consists of a board 28x28x8 mm, weight 10 g, 24 MHz clock, the guidance system is PN type in cartesian form.
In the figure some examples of controlled trajectories.

 

img daforno