METHOD FOR ESTIMATING THE MOVEMENT OF AN OBJECT MOVING IN A MAGNETIC FIELD

• US 20200132464A1
• Filed: 07/13/2018
• Published: 04/30/2020
• Est. Priority Date: 07/13/2017
• Status: Active Grant

• Current Assignee: SYSNAV Company
• Original Assignee: SYSNAV Company
• Inventors: VISSIERE, David, HILLION, Mathieu
• Granted Patent: US 11,988,512 B2
• Time in Patent Office: Days
• CPC Class Codes: G01C 21/08 involving use of the magnetic field of the earth
• CPC Class Codes: G01C 21/1654 with electromagnetic compass

Abstract

The present invention relates to a method for estimating the movement of an object (1) moving in an ambient magnetic field, the method being characterised in that it comprises the steps of:

• • (a) Acquiring by magnetic measurement means (20) integral with said object
    • (1) at least one component:
      • of the magnetic field and/or
      • of at least one i-th derivative of the magnetic field, with n+1≥i≥1,

n≥1,

• •  at the level of the magnetic measurement means (20);
  • (b) Estimating by the data processing means (21, 31, 41) at least one component of the movement of said object (1) using at least one component of the equation ∇_{{dot over (n)}}B=f_n(Ω)·∇_nB+g_n(∇_n+1B)·V, where ∇_nB is an n-th derivative of the magnetic field, Ω the instantaneous angular velocity, V the instantaneous linear velocity, and f_n and g_n predetermined functions.

Claims

1. Method for estimating the movement of an object (1) moving in an ambient magnetic field, the method being characterised in that it comprises the steps of:

(a) Acquiring by magnetic measurement means (20) integral with said object (1) at least one component;

of the magnetic field and/or

of at least one i-th derivative of the magnetic field, with n+1≥

i≥

1 and n≥

1,

at the level of the magnetic measurement means (20);

(b) Estimating by the data processing means (21, 31, 41) at least one component of the movement of said object (1) using at least one component of the equation ∇

_{{dot over (n)}}B=f_n(Ω

)·

∇

_nB+g_n(∇

_n+1B)·

V, where ∇

_nB is an n-th derivative of the magnetic field, Ω

the instantaneous angular velocity, V the instantaneous linear velocity, and f_n and g_n predetermined functions.

2. Method according to claim 1, in which the magnetic measurement means (20) include at least one gradiometer, such that step (a) includes the acquisition by each gradiometer integral with said object (1) of a component of at least one i-th derivative of the magnetic field at the level of the gradiometer.

3. Method according to one of claims 1 and 2, in which the magnetic measurement means (20) include at least one magnetometer, such that step (a) includes the acquisition by said magnetometer integral with said object (1) of a component of the magnetic field at the level of the magnetometer.

4. Method according to one of claim 2 or 3, in which the magnetic measurement means (20) only include gradiometers or only magnetometers.

5. Method according to one of claims 2 to 4, in which the magnetic measurement means (20) are constituted of a plurality of gradiometers or magnetometers organised into triaxes, each triaxis being associated with a spatial position.

6. Method according to one of claims 2 to 5, in which i∈

{n;

n+1}, such that step (a) includes the acquisition by each gradiometer integral with said object (1) of a component of the n-th derivative of the magnetic field at the level of the gradiometer.

7. Method according to claim 6, in which at least 4n+8 components of the n-th derivative of the magnetic field are acquired at step (a), and 3ⁿ⁺¹ components of the equation ∇

_{{dot over (n)}}B=f_n(Ω

)·

∇

_nB+g_n(∇

_n+1B)·

V are used at step (b).

8. Method according to one of claims 1 to 7, in which at least (n+2)(n+4) components of the magnetic field and/or at least one i-th derivative of the magnetic field are acquired at step (a), and 3ⁿ⁺¹ components of the equation ∇

_{{dot over (n)}}B=f_n(Ω

)·

∇

_nB+g_n(∇

_n+1B)·

V are used at step (b).

9. Method according to one of claims 7 and 8, in which at least one relationship between components of the equation ∇

_{{dot over (n)}}B=f_n(Ω

)·

∇

_nB+g_n(∇

_n+1B)·

V is determined at step (b) by application of the local version of at least one Maxwell equation to the components of the n-th derivative of the magnetic field ∇

_nB.

10. Method according to one of claims 1 to 9, in which n=1.

11. Method according to one of claims 1 to 10, in which is also used at step (b) at least one component of at least one supplementary equation ∇

_{{dot over (k)}}B=f_k(Ω

)·

∇

_kB+g_n(∇

_k+1B)·

V, with k∈

0;

n−

1.

12. Method according to claim 11, in which k=0, f₀=skew, g₀=id such that the supplementary equation is {dot over (B)}=−

Ω

×

B+∇

B·

V.

13. Method according to one of claims 1 to 12, in which step (a) further includes the acquisition by inertial measurement means (24) integral with said object (1) at least one component of the angular velocity

18. Computer programme product including code instructions for the execution of a method for estimating the movement of an object (1) moving in an ambient magnetic field according to one of claims 1 to 13, when said programme is executed on a computer.

19. Storage means readable by a computer equipment on which a computer programme product includes code instructions for the execution of a method for estimating the movement of an object (1) moving in an ambient magnetic field according to one of claims 1 to 13.

14. Equipment (2, 3, 4) for estimating the movement of an object (1) moving in an ambient magnetic field, characterised in that it includes data processing means (21, 31, 41) configured to implement:

the reception of at least one component;

of the magnetic field and/or

of at least one i-th derivative of the magnetic field, with n+1≥

i≥

1 and n≥

1,

acquired by magnetic measurement means (20) integral with said object (1);

the estimation of at least one component of the movement of said object (1) using at least one component of the equation ∇

_{{dot over (n)}}B=f_n(Ω

)·

∇

_nB+g_n(∇

_n+1B)·

V, where ∇

_nB is an n-th derivative of the magnetic field, Ω

the instantaneous angular velocity, V the instantaneous linear velocity, and f_n and g_n predetermined functions.

15. Equipment according to claim 14, being a case (2) including the magnetic measurement means (20).

16. Equipment according to claim 14, being a mobile terminal (3) or a server (4), suited for communicating with a case (2) including the magnetic measurement means (20).

17. System including the equipment (3, 4) according to claim 16 and at least one connected case (2).