Device for measuring rotation, associated method and inertial navigation unit

Patent metadata

Field	Value
Publication number	US-10690501-B2
Application number	US-201716089688-A
Country	US
Kind code	B2
Filing date	Mar 28, 2017
Priority date	Mar 31, 2016
Publication date	Jun 23, 2020
Grant date	Jun 23, 2020

Abstract

A device for measuring rotation including an NMR gyroscope having a sensing axis, a computer, a generating member configured to generate a magnetic field directed along the sensing axis, and a MEMS gyroscope rigidly connected to the NMR gyroscope, the MEMS gyroscope having a sensing axis aligned with the sensing axis of the NMR gyroscope, the MEMS gyroscope being suitable for delivering a MEMS signal representing a rotation about the sensing axis, the computer being configured to calculate, from an NMR signal output by the NMR gyroscope, information relating to a rotation about the sensing axis, and to analyse the MEMS signal over time in order to determine a current cut-off frequency, the computer also being configured to control the generating member in order to generate, over time, a magnetic field of which the amplitude is a function of the current cut-off frequency.

First claim

What is claimed is:

1. A measuring device for measuring rotation including an NMR gyroscope having a predetermined sensitive axis and a computer, the NMR gyroscope further comprising a generation member configured to generate a magnetic field directed along the sensitive axis,
the computer being configured to compute, based on an NMR signal output by the NMR gyroscope, a data item relating to a rotation about the sensitive axis,
wherein the measuring device further comprises a MEMS gyroscope rigidly connected to the NMR gyroscope, the MEMS gyroscope having a sensitive axis merged with the sensitive axis of the NMR gyroscope, and suitable for outputting a MEMS signal representative of a rotation about the sensitive axis,
the computer being also configured to analyze, over time, the MEMS signal, and to determine a present cutoff frequency equal to a frequency value from which an amplitude of a present spectrum of the MEMS signal is less than or equal to a predetermined threshold,
the computer being further configured to control the generation member so as to generate, over time, the magnetic field with an amplitude that is dependent on the present cutoff frequency determined by the computer.

2. The measuring device according to claim 1 , wherein the NMR gyroscope includes a cell comprising a single gas having a nuclear spin different from zero, the gas having a gyromagnetic ratio, the generation member being configured to generate, over time, the magnetic field with an amplitude that is greater than or equal to a result of a division of the present cutoff frequency by the gyromagnetic ratio of the gas.

3. The measuring device according to claim 1 , wherein the NMR gyroscope includes a cell comprising N gases each having a nuclear spin different from zero, N being a natural integer strictly greater than 1, each gas having a specific gyromagnetic ratio, the absolute values of the gyromagnetic ratios being distinct in pairs, the generation member being configured to generate, over time, the magnetic field with an amplitude that is greater than or equal to a maximum among a result of a division of the current cutoff frequency by the smallest of the absolute values of the gyromagnetic ratios, and a result of each division of double the present cutoff frequency by each of the differences between the absolute value of a gyromagnetic ratio and the absolute value of a gyromagnetic ratio which is immediately lower.

4. The measuring device according to claim 3 , wherein the cell comprises a first gas and a second gas, the first gas being xenon 131 and the second gas being xenon 129.

5. The measuring device according to claim 1 , wherein the computer is configured to detect a present stage among a start-up stage and a navigation stage, the computer being further configured to control, in the case where the present stage is a start-up stage, the generation member so as to generate the magnetic field with a predetermined set-point amplitude.

6. Inertial navigation unit including a first and a second measuring device according to claim 1 , the first and the second measuring device having non-parallel sensitive axes.

7. Inertial navigation unit including a first, a second and a third measuring device according claim 1 , the first and the second measuring device having non-parallel sensitive axes and the third measuring device having a sensitive axis non-parallel to each of the sensitive axes of the first and the second measuring device.

8. A method for measuring rotation including computing of a data item relating to a rotation about a predetermined sensitive axis, based on an NMR signal output by an NMR gyroscope having the predetermined sensitive axis and comprising a generation member configured to generate a magnetic field directed along the sensitive axis,
wherein the method further includes steps for:
analyzing, over time, a MEMS signal emitted by a MEMS gyroscope rigidly connected to the NMR gyroscope and having a sensitive axis merged with the sensitive axis of the NMR gyroscope, the MEMS signal being representative of a rotation about the sensitive axis, and determining a present cutoff frequency equal to the frequency value from which the amplitude of a present spectrum of the MEMS signal is less than or equal to a predetermined threshold;
commanding the generation member of the NMR gyroscope to generate, over time, the magnetic field with an amplitude that is dependent on the present cutoff frequency.

9. The method according to claim 8 , further including steps for:
detecting a present stage among a start-up stage and a navigation stage;
in the case where the present stage is a start-up stage, commanding the generation member to generate the magnetic field with a predetermined set-point amplitude.

10. Computer program product comprising program code instructions which, when run by a computer, implement the method according to claim 8 .

Assignees

• Commissariat Energie Atomique
• Safran

Inventors

• Palacios Laloy Augustin
• Brunstein Etienne
• Gramlich Marc
• Morales Sophie

Classifications

• G01C19/60 Primary

  Electronic or nuclear magnetic resonance gyrometers · CPC title

• G01C19/5776

  Signal processing not specific to any of the devices covered by groups G01C19/5607 - G01C19/5719 · CPC title