Optimal methods to feedback control and estimate magnetic fields to enable a neural detection system to measure magnetic fields from the brain

Patent metadata

Field	Value
Publication number	US-11604236-B2
Application number	US-202117160195-A
Country	US
Kind code	B2
Filing date	Jan 27, 2021
Priority date	Feb 12, 2020
Publication date	Mar 14, 2023
Grant date	Mar 14, 2023

Abstract

An active shield magnetometry system comprises at least one magnetic field actuator configured for generating an actuated magnetic field that at least partially cancels an outside magnetic field, thereby yielding a total residual magnetic field. The active shield magnetometry system further comprises a plurality of magnetometers respectively configured for measuring the total residual magnetic field and outputting a plurality of total residual magnetic field measurements. The active shield magnetometry system further comprises at least one feedback control loop comprising at least one optimal linear controller configured for controlling the actuated magnetic field at least partially based on at least one of the plurality of total residual magnetic field measurements respectively output by at least one of the plurality of magnetometers.

First claim

What is claimed is:

1. An active shield magnetometry system, comprising:
at least one magnetic field actuator configured for generating an actuated magnetic field that at least partially cancels an outside magnetic field, thereby yielding a total residual magnetic field;
a plurality of magnetometers respectively configured for measuring the total residual magnetic field and outputting a plurality of total residual magnetic field measurements;
at least one feedback control loop comprising at least one optimal linear controller configured for controlling the actuated magnetic field at least partially based on at least one of the plurality of total residual magnetic field measurements respectively output by at least one of the plurality of magnetometers.

2. The active shield magnetometry system of claim 1 , wherein each of the at least one optimal linear controller comprises one of a linear quadratic regulator (LQR) controller, an H2 controller, and an Hinfinity controller.

3. The active shield magnetometry system of claim 1 , wherein each of the at least one optimal linear controller is configured for controlling the actuated magnetic field in a manner that suppresses the total residual magnetic field at at least one of the plurality of magnetometers.

4. The active shield magnetometry system of claim 3 , wherein each of the at least one optimal linear controller is configured for controlling the actuated magnetic field in a manner that minimizes a performance metric that includes a magnitude of the suppressed total residual magnetic field at the at least one magnetometer and a magnitude of the control effort of the at least one optimal linear controller.

5. The active shield magnetometry system of claim 4 , wherein the total performance metric further includes a magnitude of a time-integral of the suppressed total residual magnetic field at the at least one magnetometer.

6. The active shield magnetometry system of claim 1 ,
wherein the plurality of magnetometers comprises a plurality of coarse magnetometers respectively configured for coarsely measuring the total residual magnetic field and outputting a plurality of coarse total residual magnetic field measurements, and a plurality of fine magnetometers respectively configured for finely measuring the total residual magnetic field and outputting a plurality of fine total residual magnetic field measurements;
wherein the at least one feedback control loop comprises a coarse feedback control loop, such that the at least one optimal linear controller is configured for coarsely controlling the actuated magnetic field at least partially based on at least one of the plurality of coarse total residual magnetic field measurements respectively output by at least one of the plurality of coarse magnetometers; and
wherein the at least one feedback control loop further comprises a fine feedback control loop, such that the optimal linear controller is configured for finely controlling the actuated magnetic field at least partially based on at least one of the plurality of fine total residual magnetic field measurements respectively output by at least one of the plurality of fine magnetometers.

7. The active shield magnetometry system of claim 6 ,
wherein the plurality of coarse feedback control loops are configured for coarsely controlling the actuated magnetic field respectively in a manner that suppresses the total residual magnetic field at the at least one fine magnetometer to a baseline level, such that the at least one fine magnetometer comes in-range; and
wherein the plurality of fine feedback control loops are configured finely controlling the actuated magnetic field in a manner that further suppresses the total residual magnetic field at the at least one fine magnetometer to a lower level.

8. The active shield magnetometry system of claim 6 , wherein the coarse feedback control loop is configured for estimating the total residual magnetic field at at least one of the plurality of fine magnetometers based on the plurality of coarse total residual magnetic field measurements, and wherein the optimal linear controller of the coarse feedback control loop is configured for coarsely controlling the actuated magnetic field at least partially based on the estimated total residual magnetic field at the at least one fine magnetometer.

9. The active shield magnetometry system of claim 6 , wherein each of the plurality of coarse magnetometers is a flux gate magnetometer, and each of the plurality of fine magnetometers is an optically pumped magnetometer (OPM).

10. The active shield magnetometry system of claim 1 ,
wherein the at least one magnetic field actuator is configured for generating an actuated magnetic field at a plurality of distinct frequencies that at least partially cancels an outside magnetic field at the plurality of distinct frequencies, thereby yielding the total residual magnetic field; and
wherein the at least one feedback control loop comprises a plurality of feedback control loops, and wherein the at least one optimal linear controller comprises a plurality of optimal linear controllers configured for controlling the actuated magnetic field respectively at the plurality of distinct frequencies at least partially based on at least one of the plurality of total residual magnetic field measurements respectively output by the at least one magnetometer.

11. The active shield magnetometry system of claim 10 , wherein one of the plurality of distinct frequencies comprises a frequency in the range of 0 Hz-5 Hz.

12. The active shield magnetometry system of claim 10 , wherein the plurality of distinct frequencies comprises a plurality of harmonic frequencies.

13. The active shield magnetometry system of claim 12 , wherein the harmonic frequencies are 60 Hz harmonic frequencies.

14. The active shield magnetometry system of claim 1 , further comprising a processor containing the at least one feedback control loop.

15. The active shield magnetometry system of claim 1 , further comprising:
a signal acquisition unit configured for being worn on a head of a user, the signal acquisition unit comprising a support structure, the at least one magnetic field actuator affixed to the support structure, the plurality of magnetometers affixed to the support structure, the signal acquisition unit configured for deriving at least one magnetoencephalography (MEG) signal respectively from at least one of the plurality of total residual magnetic field measurements; and
a signal processing unit configured for determining an existence of neural activity in the brain of the user based on the at least one MEG signal.

16. An active shield magnetometry method, comprising:
generating an actuated magnetic field that at least partially cancels an outside magnetic field, thereby yielding a total residual magnetic field at a plurality of measurement locations;
measuring the total residual magnetic field at the plurality of measurement locations and outputting a plurality of total residual magnetic field measurements;
controlling the actuated magnetic field with at least one optimal linear controller at least partially based on at least one of the plurality of total residual magnetic field measurements.

17. The active shield magnetometry method of claim 16 , wherein each of the at least one optimal linear controller comprises one of a linear quadratic regulator (LQR) controller, an H2 controller, and an Hinfinity controller.

18. The active shield magnetometry method of claim 16 , wherein the actuated magnetic field is controlled by the at

Assignees

• Hi Llc

Inventors

• Shapiro Benjamin
• Jimenez-Martinez Ricardo
• Kates-Harbeck Julian

Classifications

• G01R33/0005

  Geometrical arrangement of magnetic sensor elements; Apparatus combining different magnetic sensor types (G01R33/0206 takes precedence) · CPC title

• G01R33/26 Primary

  using optical pumping · CPC title

• G01R33/04

  using the flux-gate principle · CPC title

• A61B5/245 Primary

  specially adapted for magnetoencephalographic [MEG] signals · CPC title

• G01R33/0017

  Means for compensating offset magnetic fields or the magnetic flux to be measured; Means for generating calibration magnetic fields · CPC title