Calibration of gyroscopic systems with vibratory gyroscopes

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

said calibration method comprising the following steps at the level of the vibratory gyroscope to be calibrated:

/1/ applying, to the gyroscope to be calibrated, over a period of time, an initial command for a change in vibration position from a first vibration position (θ 1 ) to a second vibration position (θ 2 ); and

/2/ determining a calibrated scale factor value of the vibratory gyroscope to be calibrated, on the basis of a value calculated in relation to step /1/, based on the period of time during which the initial command is applied, the initial command, an angular difference between the first and second vibration positions measured according to the first measurement and an angular difference between the first and second vibration positions measured according to the second measurement.

2. The calibration method according to claim 1 , also comprising the following step, between step /1/and step /2/:

/1-a/ applying, over a period of time, a second command capable of commanding a change in vibration position from the second vibration position to the first vibration position; and

in which, in step /2/, a calibrated scale factor value of the vibratory gyroscope to be calibrated is determined by calculating the average between, on the one hand, the value calculated in relation to step /1/and, on the other hand, a value calculated in relation to step /1-a/ based on the period of time during which the second command is applied, the second command, an angular difference between the second and first vibration positions measured according to the first measurement and an angular difference between the second and first vibration positions measured according to the second measurement.

3. The calibration method according to claim 1 , also comprising the following steps, between step /1/and step /2/:

/1-a/ applying, over a period of time, a second command capable of commanding a change in vibration position from the second vibration position to the first vibration position; and

/1-b/ applying, over a period of time, a third command capable of commanding a change in vibration position from the first vibration position to a third vibration position; and in which, in step /2/, a calibrated scale factor value of the vibratory gyroscope to be calibrated is determined by calculating the average between, on the one hand, the value calculated in relation to step /1/and, on the other hand, a value calculated in relation to step /1-b/ based on the period of time during which the third command is applied, the third command, an angular difference between the first and third vibration positions measured according to the first measurement and an angular difference between the first and third vibration positions measured according to the second measurement.

4. A method of calibrating a gyroscopic system according to claim 3 , in which the second and third vibration positions are situated 90 degrees on either side of the first vibration position respectively.

5. A method of calibrating a gyroscopic system according to claim 3 , also comprising the following step:

reiterating K times steps /1/, /1-a/ and /1-b/, during each reiteration the second and third vibration positions being respectively different from the second and third vibration positions of the steps previously iterated, K being an integer;

in which a calibrated scale factor value is determined for each reiteration respectively, by calculating the average of the values calculated in relation to steps /1/and /1-b/ of each iteration.

6. A method of calibrating a gyroscopic system according to claim 1 , in which, during the implementation of the steps, the gyroscopic system provides gyroscopic measurements on the basis of measurement values provided by the second means of measurement.

7. The 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 a vibratory gyroscope to be calibrated, among the at least four vibratory gyroscopes of the gyroscopic system, and a second measurement being provided by a combination of the respective measurements from the other vibratory gyroscopes of the system, said first and second measurements being carried out along a same measurement axis;

said gyroscopic system comprising:

a command unit for applying, over a period of time, an initial command for a change in vibration position from a first vibration position (θ 1 ) to a second vibration position (θ 2 ); and

a determination unit capable of determining a calibrated scale factor value of the vibratory gyroscope to be calibrated on the basis of a value calculated in relation to the initial command based on the period of time during which the command is applied, the command, an angular difference between the first and second vibration positions measured according to the first measurement and an angular difference between the first and second vibration positions measured according to the second measurement.

8. The gyroscopic system according to claim 7 , in which the command unit is moreover capable of applying, over a period of time, a second command capable of commanding a change in vibration position from the second vibration position to the first vibration position; and

in which the determination unit is moreover capable of determining a calibrated scale factor value by calculating the average between, on the one hand, the value calculated in relation to the initial command and, on the other hand, a value calculated in relation to the second command based on the period of time during which the second command is applied, the second command, an angular difference between the second and first vibration positions measured according to the first measurement and an angular difference between the second and first vibration positions measured according to the second measurement.

9. The gyroscopic system according to claim 7 , in which the command unit is capable of applying, over a period of time, a second command capable of commanding a change in vibration position from the second vibration position to the first vibration position; and of applying, over a period of time, a third command capable of commanding a change in vibration position from the first vibration position to a third vibration position; and

in which the determination unit is moreover capable of determining a calibrated scale factor value by calculating the average between, on the one hand, the value calculated in relation to the initial command and, on the other hand, a value calculated in relation to the third command based on the period of time during which the third command is applied, the third command, an angular difference between the first and third vibration positions measured according to the first measurement and an angular difference between the first and third vibration positions measured according to the second measurement.

10. The gyroscopic system according to claim 7 , in which the second and third vibration positions are situated 90 degrees on either side of the first vibration position respectively.