Calibration Of Vibratory Gyroscope

• US 20110232359A1
• Filed: 11/27/2009
• Published: 09/29/2011
• Est. Priority Date: 11/28/2008
• Status: Active Grant

• Current Assignee: Safran Electronics & Defense
• Original Assignee: Sagem Defense Securite (Safran SA)
• Inventors: Caron, Jean-Michel
• Granted Patent: US 8,424,363 B2
• Time in Patent Office: Days
• US Class Current: 73/1.77
• CPC Class Codes: G01C 19/56 Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces
• CPC Class Codes: G01C 19/567 using the phase shift of a vibration node or antinode
• CPC Class Codes: G01C 25/005 initial alignment, calibration or starting-up of inertial devices

Abstract

A gyroscopic system comprises at least four vibratory gyroscopes capable of changing vibration position. A first measurement is provided by a gyroscope to be calibrated and a second measurement is provided by a combination of the respective measurements from the other gyroscopes of the system, these first and second measurements being carried out along the same measurement axis. The determination (12) of a measurement drift value between the first measurement and the second measurement is followed by a command (13) to change the vibration position of the gyroscope to be calibrated to another vibration position and a drift value is again determined. The vibration position change command and the determination of a drift value are repeated (14) K times, K being a positive integer. Then, a drift model is generated (15) as a function of the vibration position of the gyroscope to be calibrated on the basis of the drift values obtained.

Claims

1. Method of calibrating a gyroscope to be calibrated in a gyroscopic system comprising at least four vibratory gyroscopes capable of changing vibration position among a plurality of vibration positions;

a first measurement being provided by said gyroscope to be calibrated and a second measurement being provided by a combination of the respective measurements from the other gyroscopes of said system, said first and second measurements being carried out along the same measurement axis;

said calibration method comprising the following steps, for the gyroscope to be calibrated which vibrates in one of the vibration positions;

/1/ determining (12) a measurement drift value between said first measurement and said second measurement;

/2/ commanding (13) the change in vibration position of the gyroscope to be calibrated to another vibration position of said plurality of vibration positions and iterating step /1/;

/3/ iterating (14) step /2/ K times, K being a positive integer; and

/4/ generating (15) a drift model as a function of the vibration position of the gyroscope to be calibrated on the basis of the drift values obtained in the iterations of step /1/.

2. Calibration method according to claim 1, wherein, the gyroscopic system comprising four vibratory gyroscopes, three vibratory gyroscopes are arranged along three orthogonal axes respectively and the fourth vibratory gyroscope is arranged along the trisectrix of said three orthogonal axes.

3. Calibration method according to claim 1 or 2, wherein, after step /4/, the measurements provided by the vibratory gyroscope, for which a drift model has been generated in step /4/, are corrected on the basis of said drift model.

4. Calibration method according to any one of the previous claims, wherein a specific drift value is obtained by also carrying out step /1/ over a period of time corresponding to the change in vibration position of the gyroscope to be calibrated, said specific drift value being used in order to calibrate a scale factor of the gyroscope to be calibrated.

5. Calibration method according to any one of the previous claims, wherein, the gyroscopic system providing navigation information on the basis of respective measurements from a set of at least three determined vibratory gyroscopes,

during the implementation of steps /1/ to /4/ on a gyroscope to be calibrated among said set, the measurement from the gyroscope to be calibrated, on the basis of which the navigation information is provided, is replaced by a measurement along the same measurement axis as said gyroscope to be calibrated, obtained by combining the respective measurements from the other two vibratory gyroscopes of said set and from at least one fourth vibratory gyroscope.

6. Calibration method according to any one of claims 1 to 4, wherein, the gyroscopic system providing navigation information on the basis of respective measurements from a set of at least three specific vibratory gyroscopes,

during the implementation of steps /1/ to /4/ on a gyroscope to be calibrated among said set, the measurement from the gyroscope to be calibrated, on the basis of which the navigation information is provided, is corrected on the basis of a combination of the measurements provided by the gyroscopes of said system other than the gyroscope to be calibrated.

7. Calibration method according to any one of the previous claims, wherein the at least three gyroscopes in the set are calibrated by generation of a drift model by applying steps /1/ to /4/ consecutively to each one.

8. Calibration method according to any one of the previous claims, wherein the at least three gyroscopes in the set are calibrated by generation of a drift model by applying step /1/ to each of the gyroscopes successively, then step /2/ to each of the gyroscopes successively, then step /3/ to each of the gyroscopes successively and finally step /4/ to each of the gyroscopes successively.

9. Calibration method according to any one of the previous claims, wherein the drift model as a function of the vibration positions is obtained by one of the means of determination among an interpolation of the drift values obtained in the iterations of step /1/, a harmonic analysis of the drift values obtained in the iterations of step /1/ and a polynomial analysis of the drift values obtained in the iterations of step /1/.

10. Calibration method according to any one of the previous claims, wherein the measurement values relate to one measurement among the set of measurements comprising an angle measurement and an angular rate measurement.

12. Gyroscopic system according to claim 10, comprising four vibratory gyroscopes, wherein three vibratory gyroscopes are arranged respectively along three orthogonal axes and the fourth vibratory gyroscope is arranged along the trisectrix of said three orthogonal axes.

11. Gyroscopic system (40) comprising at least four vibratory gyroscopes (41) capable of changing vibration position among a plurality of vibration positions;

a first measurement being provided by a gyroscope to be calibrated and a second measurement being provided by a combination of the respective measurements from the other gyroscopes of said system, said first and second measurements being carried out along the same measurement axis;

said gyroscopic system comprising, in order to calibrate the gyroscope to be calibrated;

a determination unit (42) capable of determining a measurement drift value between said first measurement and said second measurement;

a command unit (43) capable of commanding the change in vibration position of the gyroscope to be calibrated to another vibration position of said plurality of vibration positions and requiring the determination of a drift value by the determination unit; and

a generation unit (44) capable of generating a drift model as a function of the vibration position of the gyroscope to be calibrated on the basis of the drift values provided by the determination unit.

13. Gyroscopic system according to claim 11 or 12, wherein measurements provided by a vibratory gyroscope, for which a drift model has been generated by the generation unit, are corrected on the basis of said drift model.

14. Gyroscopic system according to any one of claims 11 to 13, providing navigation information on the basis of respective measurements from a set of at least three specific vibratory gyroscopes,

wherein the measurement from the gyroscope to be calibrated, on the basis of which the navigation information is provided, is replaced by a measurement along the same measurement axis as said gyroscope to be calibrated, obtained by combining the respective measurements from the other two vibratory gyroscopes in said set and from at least one fourth vibratory gyroscope.

15. Gyroscopic system according to any one of claims 11 to 13, providing navigation information on the basis of respective measurements from a set of at least three specific vibratory gyroscopes,

wherein the measurement from the gyroscope to be calibrated, on the basis of which the navigation information is provided, is corrected on the basis of a combination of the measurements provided by the gyroscopes of said system other than the gyroscope to be calibrated.