Fast response projectile roll estimator

An apparatus for estimating a roll angle of a projectile, comprising:

• a measurement unit disposed within the projectile, the measurement unit outputting roll rate, yaw rate, and pitch rate signals indicative of rotation rates about substantially orthogonal roll, yaw, and pitch axes, the roll axis substantially aligned with a longitudinal axis of the projectile;
• and
• a controller disposed within the projectile, the controller for estimating the roll angle by:
• sampling the roll rate, yaw rate, and pitch rate signals to obtain time sequential roll rate, yaw rate, and pitch rate samples,
• calculating time sequential cumulative roll estimates by summing the roll rate samples,
• calculating time sequential gravity vector estimates from the corresponding yaw rate and pitch rate samples,
• de-rolling each gravity vector estimate based on the corresponding cumulative roll estimate,
• filtering the de-rolled gravity vector estimates to determine a filtered initial roll estimate, and
• adding the filtered initial roll estimate to a current cumulative roll estimate to provide a current roll angle estimate.