Electromechanical magnetometer and applications thereof

• US 9,383,208 B2
• Filed: 10/12/2012
• Issued: 07/05/2016
• Est. Priority Date: 10/13/2011
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Mohanty, Pritiraj
• Primary Examiner(s): KINKEAD, ARNOLD M
• Application Number:
  US13/650,442
• Publication Number:
  US 20130096825A1
• Time in Patent Office: 1,362 Days
• Field of Search: 324/207.15, 324/300, 324/318, 324/228, 333/65, 331/116.M, 331/116.R, 331/116.FE, 331/154, 735/04, 73/12, 735/041.2, 600/409
• US Class Current: 1/1
• CPC Class Codes: G01C 17/28 Electromagnetic compasses with north seeking magnetic elements and having electric pick-offs G01C17/26
• CPC Class Codes: G01C 21/1654 with electromagnetic compass
• CPC Class Codes: G01P 15/097 by vibratory elements
• CPC Class Codes: G01R 33/0286 comprising microelectromechanical systems [MEMS] MEMS devices in general B81B
• CPC Class Codes: G01R 33/072 Constructional adaptation of the sensor to specific applications
• CPC Class Codes: H01J 37/147 Arrangements for directing or deflecting the discharge along a desired path H01J37/045 take precedence; lenses H01J37/10
• CPC Class Codes: H01J 37/243 Beam current control or regulation circuits H01J37/241 takes precedence
• CPC Class Codes: H03B 5/30 with frequency-determining element being electromechanical resonator

Abstract

A system that incorporates the subject disclosure may include, for example, a method for producing an electrical signal from an apparatus comprising an induction coil coupled to a mechanical resonator, wherein the electrical signal has an operating frequency proportional to a mechanical resonating frequency of the mechanical resonator and proportional to a change in a magnetic flux resulting from a change in orientation in the apparatus, detecting with a detection circuit a change in the electrical signal resulting from a change in the magnetic flux caused by the change in orientation in the apparatus, and determining a direction of the apparatus according to the change in the electrical signal. Other embodiments are disclosed.

Claims

1. An apparatus, comprising:

a magnetic core;

a mechanical resonator comprising an active layer on a compensating structure; and

an induction coil formed on the mechanical resonator and arranged to produce an electrical signal having an operating frequency proportional to a mechanical resonating frequency of the mechanical resonator and proportional to a change in a magnetic flux in the magnetic core resulting from a change in orientation of the apparatus.

2. The apparatus of claim 1, wherein the active layer is a piezoelectric material.

3. The apparatus of claim 1, wherein the compensating structure comprises one or more materials having an adaptive stiffness that reduces a variance in the mechanical resonating frequency of the mechanical resonator.

4. The apparatus of claim 1, wherein the compensating structure comprises:

a first layer having a stiffness that adapts to a change in temperature over a first temperature range;

a third layer having a stiffness that adapts to a change in temperature over a second temperature range; and

a second layer between the first layer and the third layer.

5. The apparatus of claim 4, wherein the first and third layers are formed of silicon dioxide, and wherein the second layer is formed of silicon.

6. The apparatus of claim 1, wherein the magnetic core is a ferromagnetic material.

7. The apparatus of claim 1, wherein the induction coil comprises at least one conductive loop extending around the magnetic core and integrated on the mechanical resonator.

8. An apparatus, comprising:

a magnetic core;

a mechanical resonator having an annular geometry with an opening, wherein the magnetic core is at least partially located within the opening, and wherein the mechanical resonator is coupled to two or more anchors; and

an induction coil formed on the mechanical resonator, comprising a conductor having at least one loop, and arranged to produce an electrical signal having an operating frequency proportional to a mechanical resonating frequency of the mechanical resonator and proportional to a change in a magnetic flux in the magnetic core resulting from a change in orientation of the apparatus.

9. The apparatus of claim 8, wherein the magnetic core is a first magnetic core, the mechanical resonator is a first mechanical resonator, and the induction coil is a first induction coil, the apparatus further comprising a second magnetic core, a second mechanical resonator, and a second induction coil arranged to produce a signal representing a two-dimensional or greater dimensional magnetic field vector.

10. A navigation system, comprising:

a global positioning system receiver;

a gyroscope;

an accelerometer;

an orientation sensor, comprising;

a mechanical resonator; and

an induction coil formed on the mechanical resonator and arranged to produce an electrical signal having an operating frequency proportional to a mechanical resonating frequency of the mechanical resonator and proportional to a change in a magnetic flux resulting from a change in orientation of the orientation sensor;

a memory to store instructions; and

a controller coupled to the memory, the global positioning system receiver, the gyroscope, the accelerometer and the orientation sensor, wherein responsive to executing the instructions, the controller performs operations comprising;

detecting a failure of the global positioning system receiver to provide a reliable location coordinate; and

determining a position and orientation of the navigation system according to a last known location coordinate supplied by the global positioning system receiver and position information obtained from at least one of the gyroscope, the accelerometer, the orientation sensor, or a combination thereof.

11. The navigation system of claim 10, wherein the orientation sensor further comprises a magnetic core, wherein the operating frequency of the electrical signal is proportional to the mechanical resonating frequency of the mechanical resonator and proportional to the change in the magnetic flux in the magnetic core resulting from the change in orientation of the orientation sensor.

12. The navigation system of claim 10, wherein the gyroscope comprises a three-axis gyroscope, and wherein the accelerometer comprises a three-axis accelerometer.

13. The navigation system of claim 10, wherein the global positioning system receiver comprises a second mechanical resonator.

14. The navigation system of claim 10, wherein the gyroscope comprises a second mechanical resonator.

15. The navigation system of claim 10, wherein the accelerometer comprises a second mechanical resonator.

16. The navigation system of claim 10, wherein the mechanical resonator comprises an active layer on a compensating structure, and wherein the active layer is a piezoelectric material, and wherein the compensating structure comprises one or more materials having a stiffness that adapts to a change in temperature for reducing a variance in a mechanical resonating frequency of the mechanical resonator.

17. The navigation system of claim 10, wherein two or more of the global positioning system receiver, the gyroscope, the accelerometer, and the orientation sensor are formed on the same substrate to form a first component.

18. The navigation system of claim 10, comprising at least one more instance of the orientation sensor resulting in a plurality of orientation sensors, wherein the controller, responsive to executing the instructions, further performs operations comprising:

detecting a plurality of signals from the plurality of orientation sensors; and

determining from the plurality of signals a two-dimensional or greater dimensional magnetic field vector for determining the orientation of the navigation system.

19. The navigation system of claim 10, comprising a timing reference supplied to the global positioning system receiver, wherein the timing reference is received from a second mechanical resonator.

20. A method, comprising:

producing an electrical signal from an apparatus comprising an induction coil formed on a mechanical resonator, the mechanical resonator comprising an active layer on a compensating structure, wherein the electrical signal has an operating frequency proportional to a mechanical resonating frequency of the mechanical resonator and proportional to a change in a magnetic flux resulting from a change in orientation in the apparatus;

detecting with a detection circuit a change in the electrical signal resulting from a change in the magnetic flux caused by the change in orientation in the apparatus; and

determining a direction of the apparatus according to the change in the electrical signal.

21. The method of claim 20, wherein the active layer is a piezoelectric material, and wherein the compensating structure comprises one or more materials having a stiffness that adapts to a change in temperature for reducing a variance in the mechanical resonating frequency of the mechanical resonator.

23. The method of claim 20, comprising supplying the direction to one of a medical device, a geological measurement device, or planetary measurement device.

24. The method of claim 20, wherein the apparatus comprises a magnetic core, and wherein the operating frequency of the electrical signal is proportional to the mechanical resonating frequency of the mechanical resonator and proportional to the change in the magnetic flux in the magnetic core resulting from a change in orientation of the apparatus.

22. A method, comprising:

producing an electrical signal from an apparatus comprising an induction coil formed on a mechanical resonator, wherein the electrical signal has an operating frequency proportional to a mechanical resonating frequency of the mechanical resonator and proportional to a change in a magnetic flux resulting from a change in orientation in the apparatus;

detecting with a detection circuit a change in the electrical signal resulting from a change in the magnetic flux caused by the change in orientation in the apparatus;

determining a direction of the apparatus according to the change in the electrical signal; and

supplying the direction to a navigation system, wherein the direction enables the navigation system to determine a position and orientation of the navigation system based on a last known reliable location coordinate of a global positioning system receiver.