Magnetic field detector system

• US 10,585,150 B2
• Filed: 10/05/2016
• Issued: 03/10/2020
• Est. Priority Date: 10/06/2015
• Status: Active Grant

• Current Assignee: Charles Stark Draper Laboratory Incorporated
• Original Assignee: Charles Stark Draper Laboratory Incorporated
• Inventors: Bickford, James A., Weinberg, Marc S., Bernstein, Jonathan J., Le Blanc, John, Cook, Eugene H.
• Primary Examiner(s): Phan, Huy Q
• Assistant Examiner(s): Ferdous, Zannatul
• Application Number:
  US15/286,251
• Publication Number:
  US 20170097394A1
• Time in Patent Office: 1,252 Days
• CPC Class Codes: G01K 7/32 using change of resonant frequency of a crystal
• CPC Class Codes: G01K 7/36 using magnetic elements, e.g. magnets, coils magnetic elements per se H01F
• CPC Class Codes: G01L 1/12 by measuring variations in the magnetic properties of materials resulting from the application of stress
• CPC Class Codes: G01L 3/00 Measuring torque, work, mechanical power, or mechanical efficiency, in general
• CPC Class Codes: G01R 33/0011 comprising means, e.g. flux concentrators, flux guides, for guiding or concentrating the magnetic flux, e.g. to the magnetic sensor
• CPC Class Codes: G01R 33/0286 comprising microelectromechanical systems [MEMS] MEMS devices in general B81B
• CPC Class Codes: G01R 33/038 using permanent magnets, e.g. balances, torsion devices

Abstract

Aspects and embodiments are generally directed to magnetic field detector systems and methods. In one example, a magnetic field detector system includes a proof-mass including a magnetic dipole source, a plurality of supports, each individual support of the plurality supports being coupled to the proof-mass, a plurality of sensors, each individual sensor of the plurality of sensors positioned to measure a resonant frequency of a corresponding support of the plurality of supports, and a controller coupled to each individual sensor of the plurality of sensors, the controller configured to measure a characteristic of a magnetic field imparted on the proof-mass based on at least a first resonant frequency of the measured resonant frequencies.

Claims

1. A magnetic field detector system comprising:

a proof-mass including a magnetic dipole source that produces a torque on the proof-mass in response to interaction with a received magnetic field;

a plurality of supports, each individual support of the plurality supports being coupled to the proof-mass and having a resonant frequency affected by the torque;

a plurality of sensors, each individual sensor of the plurality of sensors positioned to measure the resonant frequency of a corresponding support of the plurality of supports; and

a controller coupled to each individual sensor of the plurality of sensors, the controller configured to measure a magnetic field strength of the received magnetic field by comparing a first resonant frequency of the measured resonant frequencies to a first frequency reference to measure the torque on the proof-mass.

2. The magnetic field detector system of claim 1, wherein the controller is further configured to determine a temperature based on a common mode signal generated from a comparison of each of the measured resonant frequencies to one another.

3. The magnetic field detector system of claim 1, wherein the measured resonant frequency of each individual support includes a natural frequency.

4. The magnetic field detector system of claim 1, wherein the plurality of supports includes a first support coupled to a first side of the proof-mass and having the first resonant frequency, a second support coupled to a second side of the proof-mass and having a second resonant frequency, a third support coupled to the first side of the proof-mass and having a third resonant frequency, and a fourth support coupled to the second side of the proof-mass and having a fourth resonant frequency.

5. The magnetic field detector system of claim 4, wherein the controller is further configured to determine a first linear force imparted on the proof-mass in a first direction and a second linear force imparted on the proof-mass in a second direction based on the first resonant frequency, the second resonant frequency, the third resonant frequency, and the fourth resonant frequency, and determine a temperature based on a common mode signal generated from a comparison of each of the first resonant frequency, the second resonant frequency, the third resonant frequency, and the fourth resonant frequency.

6. The magnetic field detector system of claim 1, wherein the magnetic dipole source is a permanent magnetic material.

7. The magnetic field detector system of claim 6, wherein the permanent magnetic material is at least one of a Neodymium Iron Boron (NdFeB) magnet, a Samarium Cobalt (SmCo) magnet, and an Alnico (AlNiCo) magnet.

8. The magnetic field detector system of claim 1, wherein the magnetic dipole source includes a plurality of permanent magnetic materials magnetized in a common direction.

9. The magnetic field detector system of claim 1, wherein the magnetic dipole source is a time-varying magnetic material.

10. The magnetic field detector system of claim 9, wherein the time-varying magnetic material is a soft magnetic material configured to receive an excitation signal of a predetermined frequency.

11. The magnetic field detector system of claim 10, wherein the soft magnetic material is Magnesium Zinc Ferrite.

12. The magnetic field detector system of claim 1, wherein each sensor of the plurality of sensors includes a comb drive including a first electrode configured to apply a voltage to a comb positioned on the corresponding support, and a second electrode configured to measure a change in a capacitance between the first electrode and the second electrode, wherein the controller is further configured to infer the resonant frequency of the corresponding support based at least in part on the change in the capacitance.

13. The magnetic field detector system of claim 1, further comprising a field concentrator located adjacent a side of the proof-mass, the field concentrator positioned so as to focus the received magnetic field on the proof-mass.

14. The magnetic field detector system of claim 1, further comprising a plurality geometric isolation structures interposed between the proof-mass and each of the plurality of supports, each geometric isolation structure being positioned to isolate a respective support from a differential thermal strain between the proof-mass and the respective support.

15. The magnetic field detector system of claim 1, further comprising an internal isolation structure extending through the proof-mass and configured to suspend the proof-mass relative to a system substrate, the internal isolation structure being positioned to isolate the plurality of supports from a differential thermal strain between the proof-mass and the plurality of supports.

16. A magnetic field transduction method comprising:

generating a magnetic dipole at a proof-mass coupled to a plurality of supports;

receiving a magnetic field at the proof-mass, the received magnetic field producing a torque on the proof-mass that alters a resonant frequency of each individual support of the plurality of supports;

measuring the resonant frequency of each individual support of the plurality of supports; and

determining a magnetic field strength of the received magnetic field based on at least one measured resonant frequency of the measured resonant frequencies of the individual supports by comparing the at least one measured resonant frequency to a frequency reference and determining the torque imparted on the proof-mass.

17. The method according to claim 16, wherein determining the magnetic field strength of the magnetic field further includes determining a variability of the magnetic field strength of the magnetic field.

18. The method according to claim 16, further comprising determining a linear force imparted on the proof-mass in a first direction by the received magnetic field based on the at least one measured resonant frequency of the measured resonant frequencies of the individual supports.

19. The method according to claim 16, further comprising determining a temperature based on a common mode signal generated by comparing the measured resonant frequencies of the plurality of supports to one another.

20. The method according to claim 16, further comprising determining a force of acceleration imparted on the proof-mass by the received magnetic field based on the at least one measured resonant frequency of the measured resonant frequencies of the individual supports.

21. The method according to claim 16, wherein the measured resonant frequency of each individual support of the plurality of supports includes a natural frequency.

22. The method according to claim 16, wherein the plurality of supports includes a first support having a first resonant frequency, a second support having a second resonant frequency, a third support having a third resonant frequency, and a fourth support having a fourth resonant frequency, and wherein the method further comprises:

determining a first linear force imparted on the proof-mass, in a first direction, based on the first resonant frequency, the second resonant frequency, the third resonant frequency, and the fourth resonant frequency;

determining a second linear force imparted on the proof-mass, in a second direction, based on the first resonant frequency, the second resonant frequency, the third resonant frequency, and the fourth resonant frequency; and

determining a temperature based on a common mode signal generated from a comparison of each of the first resonant frequency, the second resonant frequency, the third resonant frequency, and the fourth resonant frequency.

23. A magnetic field transduction method comprising:

generating a magnetic dipole at a proof-mass coupled to a plurality of supports;

receiving a magnetic field at the proof-mass;

optically measuring a displacement of the proof-mass caused in response to a torque produced on the proof-mass by the magnetic dipole in response to receiving the magnetic field; and

determining a magnetic field strength of the magnetic field based on at least the displacement of the proof-mass.