• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The invention relates to a method for detecting a rotation of a carrier by means of a device embedded in the carrier and comprising an enclosure containing a gaseous mixture of an alkali metal and a noble gas. The method comprises a step of starting (DEM-MEOP) the device during which the noble gas is polarized by means of optical pumping by metastability exchange. The start step is followed by a step of acquisition (MES-SEOP) by the device of a signal representative of said rotation during which the noble gas is kept polarized by means of optical pumping by exchange of spin. The invention extends to the device as well as to an inertial navigation unit integrating this device and to an inertial navigation method implementing the method of detecting rotation of the carrier.
    公开号:FR3068461A1
    申请号:FR1755969
    申请日:2017-06-28
    公开日:2019-01-04
    发明作者:Augustin Palacios Laloy
    申请人:Commissariat a lEnergie Atomique CEA；Safran SA；Commissariat a lEnergie Atomique et aux Energies Alternatives CEA；
    IPC主号:
    专利说明:

    METHOD FOR DETECTION OF A ROTATION WITH QUICK START OF A
    SEOP PUMPED ATOMIC GYROSCOPE
    DESCRIPTION
    TECHNICAL AREA
    The field of the invention is that of gyroscopes used to allow inertial navigation, namely navigation in the absence of any external reference point by the integration of the equations of motion. The invention relates to atomic spin gyroscopes which use the magnetic properties of atoms to carry out rotation measurements, and more particularly those of the spin pump optical exchange pumping type (SEOP).
    PRIOR STATE OF THE ART
    The most commonly used gyroscopes currently used in inertial navigation are Sagnac effect optical gyroscopes, which however have the drawback of being relatively bulky. This is not the case with atomic spin gyroscopes which can be miniaturized and could be used in many innovative applications, for example to supplement GPS data in urban areas for motorists or pedestrians , to help locate rescue teams in an underground environment, to increase the autonomy of drones in hostile environments, etc.
    Atomic gyroscopes use the magnetic properties of atoms (their spin) to measure rotation. From the measurement of the evolution of the magnetic moments of noble gas atoms, it is possible to calculate the rotation of the gyroscope and therefore that of the carrier to which it is attached. This measurement is marred by a number of imperfections, the drift of bias being the most significant of them. When this drift is of the order of 0.01 degree / hour, the gyroscope is sufficiently precise to be used for inertial navigation, that is to say, for navigation independent of any external reference, carried out by double integration of the measured accelerations. on the carrier.
    To produce hyperpolarized noble gas atoms, atomic spin gyroscopes use the SEOP spin exchange optical pumping method. This method is based on the transfer of the angular momentum of photons to the electronic spins of alkaline atoms followed by the transfer, by collision, of the angular momentum of these electronic spins from alkaline atoms to the nuclear spins of noble gas atoms.
    The first atomic spin gyroscopes developed in the late 1960s used Nuclear Magnetic Resonance (NMR). For this, one or more sensitive species contained in a cell are continuously subjected to a static magnetic field, which induces a precession of their magnetic moments at a characteristic frequency, called the Larmor frequency. A variation in the value of the Larmor frequency is the sign of a rotation, and the magnitude of this variation makes it possible to measure the speed of rotation of the gyroscope with respect to the inertial frame of reference.
    Another type of atomic spin gyroscope has been developed since the 2000s. These are co-magnetometers which are based on a mixture between a noble gas and one or more alkali metals, and which unlike NMR gyroscopes operate in a regime where the alkali is subjected to a magnetic field very close to zero (any external magnetic fields being canceled by creating opposite compensation fields). This efficient architecture, particularly in the article by T.W. Kornack et al. entitled "Nuclear Spin Gyroscope Based on an Atomic Comagnetometer", Phys. Rev. Lett., Vol. 95, no. 23, p. 230801, Nov. 2005.
    However, a major drawback of this device is its start-up time which, physically limited by the slowness of the spin exchange process between the alkali metal (potassium for example) and the noble gas (helium for example), is l 'order of ten hours, while use in a real situation typically requires a start-up time and a positioning of the north of less than five minutes.
    This start-up time is linked to the time constant
    T ^ 1 of exchange of spin between the alkali metal and the noble gas, because the polarization of the latter evolves as: P = P alk Γεχ (1 - e _t ( r i + r ex)) ; where p alk es t | has polarization the ex + l'l v of the alkali metal and T x the relaxation rate of the noble gas by phenomena other than exchange.
    This drawback was identified in particular by the group of Professor Fang (University of Beihang, China) which set up a research program consisting in replacing helium 3 by another noble gas, in this case xenon 129, for reduce the start-up time to around thirty minutes as for example described in the article by J. Fang et al. entitled A novel Cs-129Xe atomic spin gyroscope with closed-loop Faraday modulation, Review of Scientific Instruments, vol. 84, no. 8, p. 083108, Aug. 2013. However, the replacement of helium 3 by xenon 129 leads to a significant deterioration in the performance of the gyroscope. However, to allow inertial navigation, we aim for a drift of the order of 0.01 ° / h and a random walking angle ("angle of random-walk", ARW) of the order of 0.002 ° / V / i.
    STATEMENT OF THE INVENTION
    The object of the invention is to reduce the start-up time of an atomic spin atomic gyroscope based on pumping of the SEOP type, in order to offer a start-up time compatible with use in a real inertial navigation situation without degrading the performance.
    To this end, it proposes a method for detecting a rotation of a carrier by means of a device on board the carrier and which comprises an enclosure containing a gaseous mixture of an alkali metal and a noble gas. The method comprises a step of starting the device during which the noble gas is polarized by means of optical pumping by metastability exchange. Following the start-up step, the method comprises a step of acquisition by the device of a signal representative of said rotation during which the noble gas is kept polarized by means of optical pumping by spin exchange.
    Some preferred but non-limiting aspects of this process are as follows:
    the start-up step is completed when the polarization imparted to the noble gas by means of optical pumping by metastability exchange corresponds to a stationary polarization imparted to the noble gas by means of optical pumping by spin exchange;
    - the optical pumping by metastability exchange comprises an excitation of the noble gas by means of a first laser pump whose power is controlled so that the polarization imparted to the noble gas by means of the optical pumping by metastability exchange reaches the polarization stationary;
    the start-up step comprises a polarization test sub-step comprising:
    o stopping optical pumping by metastability exchange;
    o starting optical pumping by spin exchange, carrying out a first measurement of the polarization of the noble gas followed subsequently by carrying out a second measurement of the polarization of the noble gas;
    o if the result of the second measurement is greater than the result of the first measurement, stopping the optical pumping by spin exchange and restarting the optical pumping by metastability exchange; and o if the result of the second measurement is less than the result of the first measurement, the start-up step is completed.
    - during the start-up step, the optical pumping by metastability exchange is carried out in an auxiliary cell of the enclosure connected to a main cell of the enclosure by a connection for diffusing the gas mixture;
    - the start-up stage includes:
    o the closure of a first valve arranged between the main cell and an intermediate cell arranged in the diffusion connection of the gas mixture; and o the opening of a second valve arranged between the intermediate cell and the auxiliary cell.
    The invention extends to an inertial navigation method implementing the method of detecting a rotation of the carrier.
    The invention also relates to a rotation detection device, comprising an enclosure containing a gaseous mixture of an alkali metal and a noble gas, and a first noble gas polarization system configured to perform optical pumping by spin exchange. The device also includes a second noble gas polarization system configured to perform optical pumping by metastability exchange, and a controller configured to implement the start-up and acquisition steps by selectively activating the second and the first respectively. polarization system.
    The alkali metal can be potassium and the noble gas is helium 3.
    The enclosure may include a main cell and an auxiliary cell connected to the main cell by a gas mixture diffusion connection, the second polarization system being configured to increase the polarization of the noble gas in the auxiliary enclosure and the first polarization being configured to maintain the polarization of the noble gas in the main enclosure.
    The enclosure can also include an intermediate cell arranged in the diffusion connection of the gas mixture, a first valve arranged between the main cell and the intermediate cell and a second valve arranged between the intermediate cell and the auxiliary cell, the controller being configured to , during the start-up step, close the first valve and open the second valve.
    BRIEF DESCRIPTION OF THE DRAWINGS
    Other aspects, aims, advantages and characteristics of the invention will appear better on reading the following detailed description of preferred embodiments thereof, given by way of nonlimiting example, and made with reference to the accompanying drawings. on which ones :
    - Figure 1 is a flowchart illustrating the main steps of the method according to the invention;
    - Figure 2 is a diagram of a cell that can be used in the device according to the invention.
    DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS
    The invention relates to a method for detecting a rotation of a carrier by means of a device on board the carrier. The on-board device, typically an atomic spin gyroscope, comprises an enclosure containing a gaseous mixture of an alkali metal and a noble gas. This device is configured to acquire a signal representative of the rotation of the carrier, and more precisely a signal representative of a shift in the precession of the noble gas nuclei under the effect of the rotation.
    In order to acquire such a signal, the noble gas is kept polarized at an equilibrium polarization by means of optical SEOP pumping by spin exchange. However, to quickly reach the equilibrium polarization of the SEOP pumping and thus have a brief start-up time of the device, rapid pumping is carried out by another technique, namely the so-called MEOP metastability exchange method (for “ Metastability Exchange Optical Pumping ”). According to this method, which does not require the use of an alkali metal as a pumping intermediate, some noble gas atoms are excited by an electrical discharge (plasma) to a metastable energy state where they can absorb light and be optically polarized. The spin exchange then takes place between the excited metastable state and the ground state of the noble gas. This method is currently used for the production of large volumes of hyperpolarized helium for medical imaging applications. On the other hand, its use in atomic gyroscopes has not been envisaged since in the presence of plasma numerous undesirable effects occur, in particular significant drifts linked to the interaction of the different species excited by the plasma with those which are used for the rotation measurement.
    Thus, and with reference to FIG. 1, the invention proposes a method for detecting a rotation of a carrier which comprises a step of starting "DEMMEOP" of the on-board device during which the noble gas is polarized by means of '' optical pumping by MEOP metastability exchange followed by a “MES-SEOP” acquisition step by the on-board device of a signal representative of said rotation during which the noble gas is kept polarized by means of pumping optical by SEOP spin exchange.
    In this process, we typically end the “DEM-MEOP” start-up step and start the “MES-SEOP” measurement step when the polarization imparted to the noble gas during the start-up step by means of pumping optical by metastability exchange corresponds to the stationary polarization imparted to the noble gas by means of optical pumping by p spin exchange, namely alk, · By doing so, transients are avoided during the ex + l 'i of which the measurement would not be optimal.
    The invention thus defines a start-up step where rapid polarization is carried out by MEOP pumping and a measurement step which does not undergo the imperfections induced by the plasma of a MEOP pumping since it is carried out by maintaining a stationary polarization by SEOP pumping.
    To do this, the device has a first noble gas polarization system configured to perform optical pumping by spin exchange and a second noble gas polarization system configured to perform optical pumping by metastability exchange. The device is also equipped with a controller configured to implement the method of the invention, in particular by coming from:
    - selectively activate the second polarization system (MEOP pumping) and control it in order to increase the polarization of the noble gas during the device start-up stage; and
    - selectively activate the first polarization system (SEOP pumping) and control it in order to maintain the polarization of the noble gas during the step of acquiring the signal representative of the rotation consecutive to the starting step.
    The enclosure typically contains potassium as the alkali metal and helium 3 as the noble gas.
    The first polarization system SEOP notably comprises a first laser pump, a laser probe and a photodetector delivering the signal representative of the rotation of the carrier.
    The second MEOP polarization system comprises coils wound on the wall of the enclosure which, supplied by a radio frequency signal, make it possible to inductively couple this radio frequency and from there to induce ionization of the gas mixture and therefore generating a plasma discharge capable of populating the metastable state of helium 3 (denoted 2 3 Si). This second polarization system further comprises a second pump laser capable of emitting an optical beam in the direction of the enclosure to excite helium 3. This second pump laser is tuned to the transition between the metastable state 2 3 Siet l excited state 2 3 P of helium 3, this transition corresponding to a wavelength of 1083 nm. The controller controls the power of the second pump laser so that the polarization imparted to the noble gas by means of the MEOP pump reaches the stationary polarization of the SEOP pumping. This control can be achieved by continuously measuring the polarization of the noble gas (for example using a coil) and by feedback on the power of the MEOP pumping laser so that the polarization of the noble gas at the end of the start-up step corresponds to the stationary polarization of the SEOP pumping.
    The time required to reach this stationary polarization value (duration of the start-up step) depends on many parameters (pressure in the enclosure, power of the second laser probe, external magnetic field, etc.). For a typical speaker, the duration of the start-up step is in is in the range 10-300s.
    It may not be easy to give a reliable analytical expression of this start-up time and therefore to define a priori and precisely when to switch from the start-up stage to the measurement stage. To get around this difficulty, it is possible during the start-up step to reiterate a “TST” polarization test sub-step to verify whether the stationary polarization value has been reached or not. This sub-step can include stopping the MEOP pumping, starting the SEOP pumping, carrying out a first measurement of the polarization of the noble gas followed subsequently, for example a few seconds later, by carrying out a second measurement of the polarization of the noble gas.
    If the result of the second measurement is greater than the result of the first measurement, the SEOP pumping increased the polarization. It had therefore not reached its stationary value, and MEOP pumping must be continued. Thus, in such a scenario, the polarization test sub-step includes stopping SEOP pumping and restarting MEOP pumping.
    If the result of the second measurement is less than the result of the first measurement, the stationary value is reached or even exceeded. In such a case, the start-up step is completed and the measurement step begins while keeping the SEOP pumping on.
    The measurements of the polarization of the noble gas can be carried out by detecting the magnetic field created by the polarization of the noble gas. To do this, the device can be used as a magnetometer exploiting the resonances of the alkali metal when its optical pumping is carried out in an amplitude modulated magnetic field. Such a procedure is for example described in CohenTannoudji et al. Journal of Applied Physics, vol. 5, no. 1, pp. 102-108, 1970.
    In such a case, each of the two polarization measurements takes place over a few characterization periods, the characterization period corresponding to the square of the product of the target stationary polarization multiplied by the magnetic moment of the helium 3 contained in the enclosure divided by the noise of the magnetometer into units of power spectral density.
    In an alternative embodiment, the switching instant between the start-up and measurement steps may not be detected by means of polarization measurements but may be predetermined, for example being the result of learning based on recordings of switching parameters supplying a statistical algorithm.
    It is known that the regimes for which MEOP pumping are most effective correspond to high radio frequency intensities and low helium pressures.
    In a possible embodiment shown in FIG. 2, the enclosure comprises a main cell 1 and an auxiliary cell 2 connected to the main cell by a connection for diffusing the gas mixture 2 and in which part of the helium 3 is transferred. The first polarization system (SEOP) is configured to maintain the polarization of the noble gas in the main enclosure 1, in particular by means of a first LSEOP probe laser arranged so as to illuminate the main cell 1. The second polarization system (MEOP) is configured to increase the polarization of the noble gas in the auxiliary cell 2, in particular by means of a second laser probe MSEOP arranged so as to illuminate the auxiliary cell 2 and coils (not shown) surrounding the auxiliary cell. Due in particular to the absence of alkali metal on the walls of the auxiliary cell, it is possible to generate a high intensity plasma there, which shortens the time required to reach the desired level of polarization.
    In a variant of this embodiment, an intermediate cell 4 is arranged in the connection for diffusing the gas mixture 3. This intermediate cell 4 has a volume less than that of the auxiliary cell 2, for example a volume corresponding to 5-10 % of that of the main cell.
    The enclosure also includes a first valve 5 arranged between the main cell 1 and the intermediate cell 2 and a second valve 6 arranged between the intermediate cell 5 and the auxiliary cell 2. The controller of the device is also configured for, during the 'start-up step, close the first valve 5 and open the second valve 3. Thus by closing the connection to the main cell and by opening the one to the larger auxiliary cell, gas expansion occurs which makes it possible to lower the pressure in proportion to the respective volumes of the intermediate cell and the auxiliary cell to reach the ideal pressure regime.
    The invention is not limited to the method and device described above but also extends to an inertial navigation unit incorporating such a device, as well as to an inertial navigation method implemented by such a unit and comprising the implementation of the method for detecting a rotation of the carrier previously described.
    权利要求:
    Claims (12)
    [1" id="c-fr-0001]
    1. A method of detecting a rotation of a carrier by means of a device on board the carrier and which comprises an enclosure containing a gaseous mixture of an alkali metal and a noble gas, the method comprising:
    - a start-up step (DEM-MEOP) of the device during which the noble gas is polarized by means of optical pumping by metastability exchange; and
    - following the start-up step, an acquisition step (MES-SEOP) by the device of a signal representative of said rotation during which the noble gas is kept polarized by means of optical pumping by exchange of spin.
    [2" id="c-fr-0002]
    2. Method according to claim 1, in which the starting step is completed when the polarization imparted to the noble gas by means of optical pumping by metastability exchange corresponds to a stationary polarization imparted to the noble gas by means of optical pumping by exchange of spin.
    [3" id="c-fr-0003]
    3. Method according to claim 2, in which the optical pumping by metastability exchange comprises an excitation of the noble gas by means of a first pump laser whose power is controlled so that the polarization imparted to the noble gas by means of the optical pumping by metastability exchange reaches stationary polarization.
    [4" id="c-fr-0004]
    4. Method according to claim 2, in which the start-up step comprises a polarization test sub-step (TST) comprising:
    - stopping the optical pumping by metastability exchange;
    - starting optical pumping by spin exchange, carrying out a first measurement of the polarization of the noble gas followed subsequently by carrying out a second measurement of the polarization of the noble gas;
    - if the result of the second measurement is greater than the result of the first measurement, stopping the optical pumping by spin exchange and restarting the optical pumping by metastability exchange; and
    - if the result of the second measurement is lower than the result of the first measurement, the start-up step is completed.
    [5" id="c-fr-0005]
    5. Method according to one of claims 1 to 4, in which, during the start-up step, the optical pumping by metastability exchange is carried out in an auxiliary cell (2) of the enclosure connected to a main cell ( 1) of the enclosure by a connection for diffusing the gas mixture (3).
    [6" id="c-fr-0006]
    6. Method according to claim 5, in which the starting step comprises:
    - Closing a first valve (5) arranged between the main cell (1) and an intermediate cell (4) arranged in the connection for diffusing the gas mixture; and
    - The opening of a second valve (6) arranged between the intermediate cell (4) and the auxiliary cell (2).
    [7" id="c-fr-0007]
    7. A device for detecting a rotation, comprising an enclosure containing a gaseous mixture of an alkali metal and a noble gas, and a first polarization system of the noble gas configured to perform optical pumping by spin exchange, characterized in that it further comprises a second noble gas polarization system configured to perform optical pumping by metastability exchange, and a controller configured to:
    - during a device start-up step, selectively activate the second polarization system and control it in order to increase the polarization of the noble gas; and
    - During a step of acquisition by the device of a signal representative of said rotation, consecutive to the start-up step, selectively activate the first polarization system and control it in order to maintain the polarization of the noble gas.
    [8" id="c-fr-0008]
    8. Device according to claim 7, in which the alkali metal is potassium and the noble gas is helium 3.
    [9" id="c-fr-0009]
    9. Device according to one of claims 7 and 8, wherein the enclosure comprises a main cell and an auxiliary cell connected to the main cell by a diffusion connection of the gas mixture, and in which the second polarization system is configured to increase the polarization of the noble gas in the auxiliary enclosure and the first polarization system is configured to maintain the polarization of the noble gas in the main enclosure.
    [10" id="c-fr-0010]
    10. Device according to claim 9, further comprising an intermediate cell arranged in the connection for diffusing the gas mixture, a first valve arranged between the main cell and the intermediate cell and a second valve arranged between the intermediate cell and the auxiliary cell, and wherein the controller is further configured to, during the start-up step, close the first valve and open the second valve.
    [11" id="c-fr-0011]
    11. Inertial navigation unit comprising a device according to one of claims 7 to 10.
    [12" id="c-fr-0012]
    12. A method of inertial navigation comprising the detection of a rotation of a carrier in accordance with the method according to one of claims 1 to 6.
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    同族专利:
    公开号 | 公开日
    US20190003833A1|2019-01-03|
    FR3068461B1|2019-08-30|
    US10684130B2|2020-06-16|
    EP3421933A1|2019-01-02|
    EP3421933B1|2020-08-19|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    WO2012099819A1|2011-01-21|2012-07-26|Northrop Grumman Guidance and Electronics Company Inc.|Gyroscope system magnetic field error compensation|
    WO2017042544A1|2015-09-07|2017-03-16|The University Of Nottingham|Production of hyperpolarized gas|
    FR2924826B1|2007-12-11|2010-03-05|Commissariat Energie Atomique|ATOMIC CLOCK WITH CORRECTION OF THE AMBIENT MAGNETIC FIELD|
    US9618362B2|2014-06-03|2017-04-11|Northrop Grumman Systems Corporation|Self-calibrating nuclear magnetic resonance gyroscope system|FR3077884B1|2018-02-12|2021-01-01|Commissariat Energie Atomique|ELLIPTICAL POLARIZATION VECTOR MAGNETOMETER|
    FR3083876B1|2018-07-16|2020-10-16|Commissariat Energie Atomique|ALIGNMENT VECTOR MAGNETOMETER WITH TWO DIFFERENTLY POLARIZED PROBE BEAMS|
    FR3093360B1|2019-02-28|2021-03-19|Commissariat Energie Atomique|Isotropic and all-optical scalar magnetometer|
    FR3093816B1|2019-03-12|2021-04-16|Commissariat Energie Atomique|Zero-field slave magnetometer with low-frequency filtering of the compensation field|
    CN110631580B|2019-08-22|2021-10-01|北京航天控制仪器研究所|Uniaxial inertial platform system based on atomic spin gyroscope|
    CN110672083B|2019-10-17|2021-05-14|北京航空航天大学|Single-axis modulation type magnetic compensation method of SERFatomic spin gyroscope|
    法律状态:
    2019-01-04| PLSC| Search report ready|Effective date: 20190104 |
    2019-05-22| PLFP| Fee payment|Year of fee payment: 3 |
    2020-05-20| PLFP| Fee payment|Year of fee payment: 4 |
    2021-06-30| PLFP| Fee payment|Year of fee payment: 5 |
    优先权:
    申请号 | 申请日 | 专利标题
    FR1755969|2017-06-28|
    FR1755969A|FR3068461B1|2017-06-28|2017-06-28|METHOD FOR DETECTING A ROTATION WITH QUICK STARTING OF A SEOP PUMP ATOMIC GYROSCOPE|FR1755969A| FR3068461B1|2017-06-28|2017-06-28|METHOD FOR DETECTING A ROTATION WITH QUICK STARTING OF A SEOP PUMP ATOMIC GYROSCOPE|
    US16/015,691| US10684130B2|2017-06-28|2018-06-22|Method for detecting rotation with rapid start-up of an atomic gyroscope with SEOP|
    EP18179826.5A| EP3421933B1|2017-06-28|2018-06-26|Method for detecting rotation with quick starting of a seop pumped atomic gyroscope|
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