Simulator for simulating the operation of a fiber optic gyroscope

• US 9,157,741 B2
• Filed: 03/14/2013
• Issued: 10/13/2015
• Est. Priority Date: 03/14/2013
• Status: Active Grant

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Bielas, Michael S.
• Primary Examiner(s): Jacob, Mary C
• Application Number:
  US13/829,370
• Publication Number:
  US 20150025856A1
• Time in Patent Office: 943 Days
• US Class Current: 1/1
• CPC Class Codes: G01C 19/66 Ring laser gyrometers
• CPC Class Codes: G01C 19/726 Phase nulling gyrometers, i.e. compensating the Sagnac phase shift in a closed loop system
• CPC Class Codes: G01J 1/42 using electric radiation detectors optical or mechanical part G01J1/04; by comparison with a reference light or electric value G01J1/10
• CPC Class Codes: G06F 30/20 Design optimisation, verification or simulation optimisation, verification or simulation of circuit designs G06F30/30

Abstract

A method includes simulating operation of a fiber optic gyroscope during a digital simulation. The simulation includes performing an iterative loop that includes simulating an intensity of light from a fiber coil of the fiber optic gyroscope and simulating operation of one or more control loops within the fiber optic gyroscope using the simulated intensity of the light. The intensity of the light is simulated using a sine/cosine function based on at least one angular rate-related effect injected into the simulation as a Sagnac phase shift. The simulated operation of a first of the one or more control loops attempts to reduce or eliminate the Sagnac phase shift. The method also includes storing, outputting, and/or using results of the simulation. The at least one angular rate-related effect could include rotation of the fiber coil and/or mechanical vibration of the fiber coil.

Claims

1. A method comprising:

simulating operation of a fiber optic gyroscope during a digital simulation, wherein the simulation comprises performing an iterative loop at an eigenfrequency of the fiber optic gyroscope, the iterative loop including;

simulating an intensity of light from a fiber coil of the fiber optic gyroscope, wherein the intensity of the light is simulated using a sine or cosine function based on at least one angular rate-related effect injected into the simulation as a Sagnac phase shift; and

simulating operation of one or more control loops within the fiber optic gyroscope using the simulated intensity of the light, wherein the simulated operation of a first of the one or more control loops attempts to reduce or eliminate the Sagnac phase shift; and

at least one of;

storing, outputting, and using results of the simulation.

2. The method of claim 1, wherein simulating the intensity of the light comprises:

determining a phase difference between (i) a combination of a simulated serrodyne signal and a bias modulation in the fiber optic gyroscope and (ii) an echo of the combination of the simulated serrodyne signal and the bias modulation; and

determining the intensity of the light using the phase difference.

3. The method of claim 2, wherein determining the intensity of the light using the phase difference comprises using a formula of:

I(t)=(I₀(t)/2)×

(1+cos(Δ

φ

(t)+Δ

φ

_s))−

DC

wherein I(t) represents the intensity of the light at time t, I₀(t) represents a maximum intensity of light from the fiber coil, Δ

φ

(t) represents the phase difference, Δ

φ

_s represents the Sagnac phase shift, and DC is optional and represents an offset of an analog-to-digital converter in the fiber optic gyroscope.

4. The method of claim 2, wherein simulating the operation of the one or more control loops comprises generating an updated combination of the simulated serrodyne signal and the bias modulation.

5. The method of claim 1, wherein simulating the operation of the one or more control loops comprises:

using a first accumulator to simulate generation of rotation rate values in the first control loop of the fiber optic gyroscope; and

using a second accumulator to simulate generation of rotation angle values using the rotation rate values in the first control loop of the fiber optic gyroscope.

6. The method of claim 5, wherein simulating the operation of the one or more control loops further comprises:

adding noise to the simulated intensity of the light;

simulating measurements of the simulated intensity of the light; and

simulating demodulation of the measurements to generate demodulated values;

wherein the rotation rate values are based on the demodulated values.

7. The method of claim 6, wherein simulating the operation of the one or more control loops further comprises:

simulating operation of a second of the control loops using the demodulated values.

8. The method of claim 6, wherein at least one of:

storing, outputting, and using the results of the simulation comprises;

generating a graphical display illustrating the demodulated values, the rotation rate values, the rotation angle values, and the Sagnac phase shift over time.

9. The method of claim 1, wherein each iteration of the iterative loop is performed using an updated value of a simulated serrodyne signal.

10. The method of claim 1, wherein the at least one angular rate-related effect comprises at least one of:

rotation of the fiber coil and mechanical vibration of the fiber coil.

11. An apparatus comprising:

at least one processing device configured to simulate operation of a fiber optic gyroscope during a digital simulation, wherein the simulation comprises an iterative loop performed at an eigenfrequency of the fiber optic gyroscope, wherein during the iterative loop the at least one processing device is configured to;

simulate an intensity of light from a fiber coil of the fiber optic gyroscope, wherein the at least one processing device is configured to simulate the intensity of the light using a sine or cosine function based on at least one angular rate-related effect injected into the simulation as a Sagnac phase shift; and

simulate operation of one or more control loops within the fiber optic gyroscope using the simulated intensity of the light, wherein the at least one processing device is configured to simulate operation of a first of the one or more control loops in order to reduce or eliminate the Sagnac phase shift; and

at least one memory configured to store results of the simulation.

12. The apparatus of claim 11, wherein the at least one processing device is configured to:

determine a phase difference between (i) a combination of a simulated serrodyne signal and a bias modulation in the fiber optic gyroscope and (ii) an echo of the combination of the simulated serrodyne signal and the bias modulation; and

determine the intensity of the light using the phase difference.

13. The apparatus of claim 12, wherein the at least one processing device is configured to determine the intensity of the light using a formula of:

I(t)=(I₀(t)/2)×

(1+cos(Δ

φ

(t)+Δ

φ

_s))−

DC

wherein I(t) represents the intensity of the light at time t, I₀(t) represents a maximum intensity of light from the fiber coil, Δ

φ

(t) represents the phase difference, Δ

φ

_s represents the Sagnac phase shift, and DC is optional and represents an offset of an analog-to-digital converter in the fiber optic gyroscope.

14. The apparatus of claim 11, wherein the at least one processing device is configured to:

use a first accumulator to simulate generation of rotation rate values in the first control loop of the fiber optic gyroscope; and

use a second accumulator to simulate generation of rotation angle values using the rotation rate values in the first control loop of the fiber optic gyroscope.

15. The apparatus of claim 14, wherein the at least one processing device is configured to:

add noise to the simulated intensity of the light;

simulate measurements of the simulated intensity of the light; and

simulate demodulation of the measurements to generate demodulated values;

wherein the rotation rate values are based on the demodulated values.

16. The apparatus of claim 15, wherein the at least one processing device is configured to simulate operation of a second of the control loops using the demodulated values.

17. The apparatus of claim 11, wherein the at least one processing device is configured to perform each iteration of the iterative loop using an updated value of a simulated serrodyne signal.

18. A non-transitory computer readable medium embodying a computer program, the computer program comprising computer readable program code for simulating operation of a fiber optic gyroscope during a digital simulation, wherein the computer readable program code for simulating comprises computer readable program code for, in an iterative loop:

simulating an intensity of light from a fiber coil of the fiber optic gyroscope, wherein the intensity of the light is simulated using a sine or cosine function based on at least one angular rate-related effect injected into the simulation as a Sagnac phase shift; and

simulating operation of one or more control loops within the fiber optic gyroscope using the simulated intensity of the light, wherein the simulated operation of a first of the one or more control loops attempts to reduce or eliminate the Sagnac phase shift;

wherein the iterative loop is performed at an eigenfrequency of the fiber optic gyroscope.

19. The computer readable medium of claim 18, wherein the computer readable program code for simulating the intensity of the light comprises:

computer readable program code for determining a phase difference between (i) a combination of a simulated serrodyne signal and a bias modulation in the fiber optic gyroscope and (ii) an echo of the combination of the simulated serrodyne signal and the bias modulation; and

computer readable program code for determining the intensity of the light using a formula of;

I(t)=(I₀(t)/2)×

(1+cos(Δ

φ

(t)+Δ

φ

_s))−

DC

wherein I(t) represents the intensity of the light at time t, I₀(t) represents a maximum intensity of light from the fiber coil, Δ

φ

(t) represents the phase difference, Δ

φ

_s represents the Sagnac phase shift, and DC is optional and represents an offset of an analog-to-digital converter in the fiber optic gyroscope.

20. The computer readable medium of claim 18, wherein the computer readable program code for simulating the operation of the one or more control loops comprises:

computer readable program code for using a first accumulator to simulate generation of rotation rate values in the first control loop of the fiber optic gyroscope; and

computer readable program code for using a second accumulator to simulate generation of rotation angle values using the rotation rate values in the first control loop of the fiber optic gyroscope.

21. The computer readable medium of claim 20, wherein the computer readable program code for simulating the operation of the one or more control loops further comprises:

computer readable program code for simulating measurements of the simulated intensity of the light;

computer readable program code for simulating demodulation of the measurements to generate demodulated values, wherein the rotation rate values are based on the demodulated values; and

computer readable program code for simulating operation of a second of the control loops using the demodulated values.