Gyroscopic measurement by a vibratory gyroscope

1. A method of gyroscopic measurements supplied by a gyroscopic system including a vibratory gyroscope;

said gyroscope vibrating in an initial first vibration geometrical position and supplying a measurement signal;

wherein there is applied to the vibratory gyroscope over a period of time a periodic command signal adapted:

to cause the vibration geometrical position to turn a first way, during one part of the time period, causing a change, in accordance with a first speed profile, of the position of the vibration of said gyroscope from the first vibration geometrical position to a second vibration geometrical position; and

to cause the vibration geometrical position to turn a second way opposite the first way during the other part of the time period, causing a change in accordance with a second speed profile of the position of the vibration of said gyroscope from the second vibration geometrical position to the first vibration geometrical position;

said command signal having a zero average over said time period, and the first and second speed profiles indicating a speed variation of the change of vibration geometrical position as a function of time; and

wherein the measurements supplied by the gyroscopic system are based on a corrected signal representing a variation of vibration geometrical position values and obtained by subtracting the command signal from the measurement signal supplied by the gyroscope.

2. The method according to claim 1 , wherein the second speed profile is the reverse of the first speed profile as a function of time.

3. The method according to claim 1 , wherein the two parts of the time period are identical.

4. The method according to any of claim 1 , wherein the measurement signal from the gyroscope and the command signal are expressed like the measurements supplied by the gyroscopic system either in angle values or in angular speed values.

5. The gyroscopic measurement method according to any of claim 1 , wherein the measurements supplied by the gyroscopic system correspond to angular speed values, each angular speed value resulting from the division of a difference between two vibration geometrical position values of the corrected signal separated by an integer number of time periods by a time value corresponding to the integer number of time periods.

6. The gyroscopic measurement method according to any of claim 1 , wherein the measurements supplied by the gyroscopic system are obtained by low-pass filtering of the corrected signal.

7. The gyroscopic measurement method according to claim 6 , wherein, before supplying measurements effected by the gyroscopic system, the periodic signal is applied during a time interval sufficiently long to be able to consider the command signal as a high-frequency signal relative to the measurement signal from the vibratory gyroscope.

8. The gyroscopic measurement method according to claim 1 the time period and the first and second speed profiles of the command signal are determined so that the first and second vibration geometrical positions of the vibratory gyroscope are separated by 2π/kN radians,

where N is a frequency mode of vibration of the vibratory gyroscope; and

where k is a positive integer number determined as a function of the order of the errors to be corrected.

9. A gyroscopic system including:

a vibratory gyroscope, said gyroscope vibrating in an initial first vibration geometrical position and supplying a measurement signal;

a command unit adapted to apply a periodic command signal over a time period adapted:

to cause the vibration geometrical position to turn a first way, during one part of the time period, causing a change in accordance with a first speed profile of the position of the vibration of said gyroscope from the first vibration geometrical position to a second vibration geometrical position; and

to cause the vibration geometrical position to turn a second way opposite the first way during the other part of the time period, causing a change in accordance with a second speed profile of the position of the vibration of said gyroscope from the second vibration geometrical position to the first vibration geometrical position;

said command signal having a zero average over said time period and the first and second speed profiles indicating a speed variation of the change of vibration geometrical position as a function of time; and

a processing unit adapted to supply a corrected signal representing a variation of vibration geometrical position values obtained by subtracting the command signal from the measurement signal supplied by the vibratory gyroscope.

10. The gyroscopic system according to claim 9 , wherein the second speed profile is the reverse of the first speed profile as a function of time.

11. The gyroscopic system according to claim 9 , further including a calculation unit at the output of the processing unit adapted to supply gyroscopic measurements corresponding to angular speed values, each angular speed value resulting from the division of a difference between two vibration geometrical position values of the corrected signal separated by an integer number of time periods by a time value corresponding to the integer number of time periods.

12. The gyroscopic system according to claim 9 , further including a low-pass filter at the output of the processing unit adapted to filter high-frequency components of the corrected signal.

13. The gyroscopic system according to any of claim 9 , wherein the time period and the first and second speed profiles of the command signal are determined so that the first and second vibration geometrical positions of the vibratory gyroscope are separated by 2π/kN radians,

where N is a frequency mode of vibration of the vibratory gyroscope, and

where k is a positive integer number determined as a function of the order of the errors to be corrected.