Analog torque rebalance loop for a tuned rotor gyroscope

A rebalance loop for a dry tuned rotor gyroscope having a rotor moveable about two orthogonal axes, means associated with one of said axes for producing an electrical error signal when a rate is applied to said one of said axes, means associated with the other of said axes for producing an electrical error signal when a rate is applied to said other of said axes, a first torquer coil responsive to a first torque control signal for applying a torque to said rotor about one of said axes for restoring said rotor to a null position about said one of said axes and a second torquer coil responsive to a second torque control signal for applying a torque to said rotor about the other of said axes for restoring said rotor to a null position about said other of said axes, said rebalance loop comprising;

• first front-end circuit means for demodulating one of said error signals, filtering any residual carrier signal and spin noise from said one error signal, introducing a first predetermined amount of phase lag into said one error signal, and integrating said one error signal whereby to produce a first filtered and integrated signal;
• second front-end circuit means for demodulating the other of said error signals, filtering any residual carrier signal and spin noise from said other of said error signal, introducing a first predetermined amount of phase lag into said other error signal, and integrating said other error signal whereby to produce a second filtered and integrated signal;
• first cross-axis circuit means for filtering from said second filtered and integrated signal a predetermined band of frequencies centered on the nutation frequency of said gyroscope and differentiating sad signal whereby to produce a first acceleration proportional torque signal;
• second cross-axis circuit means for filtering from said first filtered and integrated signal a predetermined band of frequencies centered on the nutation frequency of said gyroscope and differentiating said signal whereby to produce a second acceleration proportional torque signal;
• first direct-axis circuit means responsive to said first filtered and integrated signal for adding thereto a second predetermined amount of phase lag by a first nutation low-pass filter whereby to produce a first rate proportional torque signal and responsive to said first acceleration proportional torque signal to combine said first rate proportional torque signal and said first acceleration proportional torque signal to produce a first torque control signal and convert said first torque control signal in a first torquer driver to a form capable of driving said first torquer coil;
• second direct-axis circuit means responsive to said second filtered and integrated signal for adding thereto a second predetermined amount of phase lag by a second nutation low-pass filter whereby to produce a second rate proportional torque signal and responsive to said second acceleration proportional torque signal to combine said second rate proportional torque signal and said second acceleration proportional torque signal o produce a second torque control signal and convert said second torque control signal in a second torquer driver to a form capable of driving said second torquer coil;
• said first torquer driver including an operational amplifier and an inverting push-pull amplifier for amplifying the output of said operational amplifier, said operational amplifier being adapted to received, at its inverting input, an output of said first nutation low-pass filter and, at its non-inverting input, the signal received at a return line from an output terminal of said first torquer coil to which output a signal from the second cross-axis circuit means is applied;
• and
• said second torquer driver including a further operational amplifier and a further inverting push-pull amplifier for amplifying the output of said further operational amplifier, said further operation amplifier being adapted to receive, at its inverting input, an output of said second nutation low-pass filter and, at its noninverting input, the signal received at a return line from an output terminal of said second torquer coil, to which output a signal from the first cross-axis circuit means is applied.