Gimbal angle rate feedback by cage coil demodulation

Claim 1

In an automatic guidance system for projectiles or missiles including a guidance gyro having a rotating magnetic mass, a cage coil, pitch and yaw hall effect elements and precession coils, and means for providing guidance commands to pitch and yaw canards, the improvement comprising: a synchronous demodulator for receiving the cage coil output and for providing a sinusoidal output signal representative of the airframe position relative to the gyro axis, said cage coil output during guidance being a signal with a carrier at the gyro spin frequency and a modulation at the airframe natural frequency; a differentiator for converting the output of said synchronous demodulator into a signal representative of the rate of airframe movement; a pair of phase--frequency detectors for sampling the pitch and yaw hall effect element outputs with the cage signal carrier as a sample to provide phase references for the circuit; a pair of multipliers for multiplying the rate amplitude from said differentiator by the phase references from said phase detectors to resolve the rate into pitch and yaw command components; and a pair of summation circuits for scaling and subtracting the rate commands provided by said multipliers from the guidance commands to the pitch and yaw canards whereby negative rate feedback is obtained.