Automatic gain control for fiber optic gyroscope deterministic control loops

• US 7,859,678 B2
• Filed: 12/09/2008
• Issued: 12/28/2010
• Est. Priority Date: 12/09/2008
• Status: Active Grant

• Current Assignee: Nothrop Grumman Guidance and Electronics Co., Inc.
• Original Assignee: Northrop Grumman Guidance & Electronics Co., Inc. (Northrop Grumman Corporation)
• Inventors: Pavlath, George A., Tazartes, Daniel A.
• Primary Examiner(s): Lyons; Michael A
• Application Number:
  US12/316,060
• Publication Number:
  US 20100141953A1
• Time in Patent Office: 749 Days
• Field of Search: 356/459, 356/460, 356/464
• US Class Current: 356/464
• CPC Class Codes: G01C 19/726 Phase nulling gyrometers, i.e. compensating the Sagnac phase shift in a closed loop system

Abstract

An automatic gain control system for a fiber optic gyroscope control loop includes an adjustable gain applied to the gyro output signal. A pilot signal is injected into the fiber optic gyroscope control loop. A compensation loop receives signals output from the control loop and also receives pilot signals. The compensation loop processes the pilot signal to produce a compensation signal that is combined with signals output from the control loop to provide a compensated fiber optic gyroscope output signal. An automatic gain control loop is connected between the compensation loop and the adjustable gain applied to the fiber optic gyroscope output signal. The automatic gain control loop includes a gain error demodulator that multiplies the compensated fiber optic gyroscope output signal and the compensation signal together to produce a gain error signal used to control the adjustable gain in order to stabilize the gain of the gyro control loop.

Claims

1. An automatic gain control for a fiber optic gyroscope system that includes a fiber optic gyroscope control loop arranged to process signals output from the fiber optic gyroscope, comprising:

an adjustable gain applied to the signal output from the fiber optic gyroscope;

a pilot signal generator arranged to inject a pilot signal into the fiber optic gyroscope control loop which results in an output signal from the fiber optic gyroscope;

a compensation loop arranged to receive signals output from the fiber optic gyroscope control loop and to receive pilot signals from the pilot signal generator, the compensation loop being arranged to process the pilot signal to produce a compensation signal that is combined with signals output from the fiber optic gyroscope control loop to provide a compensated fiber optic gyroscope output signal; and

an automatic gain control loop connected between the compensation loop and the adjustable gain applied to the fiber optic gyroscope output signal, the automatic gain control loop including a gain error demodulator arranged to multiply the compensated fiber optic gyroscope output signal and the compensation signal together to produce a gain error signal used to control the adjustable gain in order to stabilize the gain of the fiber optic gyroscope control loop.

2. The automatic gain control of claim 1, wherein the fiber optic gyroscope control loop comprises:

an analog to digital converter arranged to digitize the signal output of the fiber optic gyroscope, the adjustable gain being an adjustable digital gain;

a control loop adder connected between the pilot signal generator and the adjustable digital gain; and

a control loop integrator connected to receive an output from the control loop adder that is the sum of the pilot signal and the digital gain.

3. The automatic gain control of claim 2 wherein the compensation loop comprises:

a compensation loop adder connected to the pilot signal generator;

a compensation loop integrator connected to an output of the compensation loop adder; and

a compensation loop gain connected to an output of the compensation loop integrator, the compensation loop gain having an output connected to an input of the compensation loop adder to provide negative feedback.

4. The automatic gain control of claim 3, further comprising an adder arranged to add fiber optic gyroscope output signals from the control loop integrator to the compensation signal output from the compensation loop integrator to produce the compensated fiber optic gyroscope output signal.

5. The automatic gain control of claim 2 wherein the automatic gain control loop comprises:

an automatic gain control error integrator connected to an output of the gain error demodulator;

an automatic gain control loop amplifier arranged to amplify signals output from the automatic gain control error integrator; and

an automatic gain control loop filter connected between the automatic gain control loop amplifier and the adjustable digital gain.

6. The automatic gain control of claim 5, further comprising a first filter connected between the output of the compensation loop integrator and a first input of the gain error demodulator.

7. The automatic gain control of claim 5, further comprising:

a reference loop having an input connected to the pilot signal generator; and

a second filter connected between an output of the reference loop and a second input of the gain error demodulator to provide a reference signal to the automatic gain control loop.

8. The automatic gain control of claim 7 wherein the reference loop comprises:

a reference loop adder connected to the pilot signal generator;

a reference loop integrator connected to an output of the reference loop adder; and

a reference gain connected to an output of the reference loop adder, the reference loop gain having an output connected to an input of the reference loop adder to provide negative feedback.

9. The automatic gain control of claim 1, further comprising a reference loop connected between the pilot signal generator and the automatic gain control loop to provide a gain reference signal to the automatic gain control loop.

10. The automatic gain control of claim 9, further comprising:

an adder having a first input connected to the pilot signal; and

a dither signal generator connected to a second input of the adder, the adder having an output connected to an input of the control loop adder to inject the pilot signal and the dither signal into the fiber optic gyroscope control loop.

11. The automatic gain control of claim 1 wherein the control loop comprises:

a variable gain analog amplifier arranged amplify analog signals output from the fiber optic gyroscope;

an analog to digital converter connected to an output of the variable gain analog amplifier

a control loop adder having a first input connected to receive digital signals from the analog to digital converter and a second input arranged to receive signals from the pilot signal generator; and

an integrator connected to receive an output from the control loop adder that is the sum of the pilot signal and the digital gain.

12. The automatic gain control of 11, further comprising a gain control digital to analog converter in the gain control loop connected to the variable gain analog amplifier.

13. The automatic gain control of claim 12 wherein the compensation loop comprises:

a compensation loop adder connected to the pilot signal generator;

a compensation loop integrator connected to an output of the compensation loop adder; and

a compensation loop gain connected to an output of the compensation loop integrator, the compensation loop gain having an output connected to an input of the compensation loop adder to provide negative feedback.

14. The automatic gain control of claim 13, further comprising an adder arranged to add fiber optic gyroscope output signals from the control loop integrator to the compensation signal output from the compensation loop integrator to produce the compensated fiber optic gyroscope output signal.

15. The automatic gain control of claim 12 wherein the automatic gain control loop comprises:

an automatic gain control error integrator connected to an output of the gain error demodulator;

an automatic gain control loop amplifier arranged to amplify signals output from the automatic gain control error integrator; and

an automatic gain control loop filter connected between the automatic gain control loop amplifier and the adjustable digital gain.

16. The automatic gain control of claim 15, further comprising a first filter connected between the output of the compensation loop integrator and the gain error demodulator.

17. The automatic gain control of claim 15, further comprising:

a reference loop having an input connected to the pilot signal generator; and

a second filter connected between an output of the reference loop and a second input of the gain error demodulator to provide a reference signal to the automatic gain control loop.

18. The automatic gain control of claim 17 wherein the reference loop comprises:

a reference loop adder connected to the pilot signal generator;

an reference loop integrator connected to an output of the reference loop adder; and

a reference gain connected to an output of the reference loop adder, the reference loop gain having an output connected to an input of the reference loop adder to provide negative feedback.