Magnetofluidic accelerometer with active suspension

• US 7,296,469 B2
• Filed: 11/04/2004
• Issued: 11/20/2007
• Est. Priority Date: 02/24/2000
• Status: Expired due to Fees

• Current Assignee: InnaLabs Technologies, Inc.
• Original Assignee: InnaLabs Technologies, Inc.
• Inventors: Suprun, Anton E., Romanov, Yuri I., Simonenko, Dmitri V.
• Primary Examiner(s): Williams; Hezron
• Assistant Examiner(s): Shah; Samir M.
• Application Number:
  US10/980,791
• Publication Number:
  US 20060059990A1
• Time in Patent Office: 1,111 Days
• Field of Search: 735/140.8, 735/141.6, 735/141.7
• US Class Current: 73/514.16
• CPC Class Codes: G01C 21/166 Mechanical, construction or arrangement details of inertial navigation systems
• CPC Class Codes: G01P 15/0888 for indicating angular acceleration
• CPC Class Codes: G01P 15/105 by magnetically sensitive devices
• CPC Class Codes: G01P 15/11 by inductive pick-up
• CPC Class Codes: G01P 15/132 with electromagnetic counterbalancing means
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 7/00 Measuring speed by integrating acceleration measuring travelled distance by double integration of acceleration G01C21/16

Abstract

A method of measuring acceleration includes suspending an inertial body using a magnetic fluid; generating a magnetic field within the magnetic fluid; modulating the magnetic field to counteract a change in position of the inertial body relative to sources of the magnetic field due to acceleration; and calculating the acceleration based on the modulation. The calculating step derives the acceleration based on an amount of current through drive coils required for the modulation. The acceleration includes linear acceleration and/or angular acceleration. The drive coils include permanent magnets, electromagnets, or a combination of a permanent magnet and an electromagnet. Sensing coils can be used for detecting the displacement of the inertial body. Each sensing coil can be positioned substantially within a corresponding drive coil. The inertial body can be non-magnetic, weakly magnetic, or have a ferromagnetic coating.

Claims

1. A method of measuring acceleration comprising:

suspending a non-magnetic inertial body using a magnetic fluid;

generating a magnetic field within the magnetic fluid;

modulating the magnetic field to counteract and minimize a displacement of the inertial body due to acceleration; and

calculating the acceleration based on the modulation,

wherein the change in the position of the inertial body is calculated based on changes of magnetic flux line distribution within the magnetic fluid.

2. The method of claim 1, wherein the calculating step derives the acceleration based on an amount of current required for the modulating using electromagnets.

3. The method of claim 1, wherein the acceleration includes linear acceleration.

4. The method of claim 1, wherein the acceleration includes angular acceleration.

5. The method of claim 1, further comprising driving current through a plurality of magnets for generating the magnetic field.

6. The method of claim 5, further comprising using sensing coils for detecting the displacement of the inertial body.

7. The method of claim 1, wherein the inertial body has a ferromagnetic coating on portions of its surface.

8. A method for measuring acceleration comprising:

suspending a non-magnetic inertial body in a magnetic fluid;

measuring behavior of the inertial body in response to acceleration;

applying a force to the inertial body to counteract the acceleration and minimize a displacement of the inertial body; and

calculating the acceleration as a function of the applied force,

wherein the displacement of the inertial body is calculated based on changes of magnetic flux line distribution within the magnetic fluid.

9. A method of measuring acceleration comprising:

suspending a non-magnetic object using a fluid;

generating a magnetic field within the fluid;

detecting a change in position of the object due to acceleration;

controlling the magnetic field to counteract and minimize the change in position of the object; and

calculating the acceleration as a function of the control of the magnetic field,

wherein the change in the position of the inertial body is calculated based on changes of magnetic flux line distribution within the magnetic fluid.

10. An A sensing element of an accelerometer comprising:

a non-magnetic inertial body;

a plurality of separate drops of magnetic fluid holding the inertial body in suspension;

a plurality of magnetic poles maintaining the drops in contact with the inertial body;

a controller that modulates magnetic fields generated by the magnetic poles to counteract and minimize a displacement of the inertial body due to acceleration;

a sensor that detects changes in the magnetic flux distribution due to the change in position of the inertial body,

wherein the change of the magnetic flux line distribution is indicative of the acceleration.

11. The sensing element of claim 10, wherein the controller derives the acceleration as a function of a current required by the magnetic poles to modulate the magnetic fields.

12. The sensing element of claim 10, wherein the acceleration comprises linear acceleration.

13. The sensing element of claim 10, wherein the acceleration comprises angular acceleration.

14. The sensing element of claim 10, wherein the angular acceleration comprises three components of angular acceleration.

15. The sensing element of claim 10, wherein the sensor fUrther comprises sensing coils for detecting the displacement of the inertial body.

16. The sensing element of claim 10, wherein the sensor further comprises Hall sensors for detecting the displacement of the inertial body.

17. The sensing element of claim 10, wherein the sensor further comprises acoustic sensors for detecting the displacement of the inertial body.

18. The sensing element of claim 10, further comprising a ferromagnetic coating on portions of the inertial body.

19. A sensing element of an accelerometer compnsing:

a non-magnetic inertial body;

a plurality of magnets located in proximity to the inertial body and on opposing sides of the inertial body;

a magnetic fluid between the magnets and the inertial body; and

a circuit that modulates magnetic fields generated by the magnets to counteract and minimize a displacement of the inertial body due to acceleration; and

a sensor that detects changes in the magnetic flux distribution due to the displacement of the inertial body,

wherein the change of the magnetic flux line distribution is indicative of the acceleration.

20. The sensing element of an accelerometer of claim 19, further comprising a second circuit that derives the acceleration based on an amount of current through the magnets required to counteract the displacement.

21. The sensing element of an accelerometer of claim 19, wherein the acceleration includes linear acceleration.

22. The sensing element of an accelerometer of claim 19, wherein the acceleration includes angular acceleration.

23. The sensing element of an accelerometer of claim 19, wherein the magnets further comprise permanent magnets.

24. The sensing element of an accelerometer of claim 19, further comprising sensing coils for detecting the displacement of the inertial body.

25. The sensing element of an accelerometer of claim 19, further comprising Hall sensors for detecting the displacement of the inertial body.

26. The sensing element of an accelerometer of claim 19, further comprising acoustic sensors for detecting displacement of the inertial body.

27. The sensing element of an accelerometer of claim 19, further comprising a ferromagnetic coating on portions of the inertial body.

28. The sensing element of an accelerometer of claim 19, further comprising:

a housing enclosing the inertial body and the magnetic fluid; and

a plurality of casings each having a magnet mounted therein, the casings being coupled to the housing and projecting into the housing.

29. A sensing element of an accelerometer comprising:

a non-magnetic inertial body;

a plurality of magnets generating a repulsive force acting on the inertial body;

a circuit that modulates magnetic fields generated by the magnets so as to counteract and minimize a displacement of the inertial body due to acceleration; and

a sensor that detects changes in the magnetic flux distribution due to the displacement of the inertial body,

wherein the change of the magnetic flux line distribution is indicative of the acceleration.

30. A sensor comprising:

a non-magnetic inertial body;

a magnetic fluid exerting a force on the inertial body;

a plurality of magnets generating magnetic fields within the magnetic fluid,

wherein a position of the inertial body relative to the magnets is maintained by modulation of the magnetic fields by minimizing a displacement of the inertial body;

a circuit that derives acceleration based on the modulation; and

a sensor that detects changes in the magnetic flux distribution due to the displacement of the inertial body,

wherein the change of the magnetic flux line distribution is indicative of the acceleration.

31. A sensor comprising:

a non-magnetic inertial body;

a fluid exerting a force on the inertial body;

a plurality of magnets generating magnetic fields within the fluid,

a position sensor detecting a change in position of the inertial body due to acceleration;

a controller that drives the magnets in response to the change so as to minimize the change in position of the inertial body; and

a sensor that detects changes in the magnetic flux distribution due to displacement of the inertial body,

wherein the change of the magnetic flux line distribution is indicative of acceleration of the sensor, and

wherein the acceleration is derived from current required by the magnets.