Magnetofluidic accelerometer with active suspension

• US 20060059990A1
• Filed: 11/04/2004
• Published: 03/23/2006
• Est. Priority Date: 02/24/2000
• Status: Active Grant

• Current Assignee: InnaLabs Technologies, Inc.
• Original Assignee: InnaLabs Technologies, Inc.
• Inventors: Simonenko, Dmitri V., Suprun, Anton E., Romanov, Yuri I.
• Granted Patent: US 7,296,469 B2
• Time in Patent Office: Days
• US Class Current: 73/514.160
• 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 an inertial body using a magnetic fluid;

generating a magnetic field within the magnetic fluid;

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

calculating the acceleration based on the modulation.

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 is non-magnetic.

8. The method of claim 1, wherein the inertial body is weakly magnetic.

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

10. A method for measuring acceleration comprising:

suspending an 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

calculating the acceleration as a function of the applied force.

11. A method of measuring acceleration comprising:

suspending an 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 the change; and

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

12. An accelerometer comprising:

an inertial body;

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

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

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

13. The accelerometer of claim 12, wherein the controller derives the acceleration as a function of a current required by the magnetic poles to modulate the magnetic fields.

14. The accelerometer of claim 12, wherein the acceleration comprises linear acceleration.

15. The accelerometer of claim 12, wherein the acceleration comprises angular acceleration.

16. The accelerometer of claim 12, wherein the angular acceleration comprises three components of angular acceleration.

17. The accelerometer of claim 12, further comprising sensing coils for detecting the displacement of the inertial body.

18. The accelerometer of claim 12, wherein the inertial body is non-magnetic.

19. The accelerometer of claim 12, wherein the inertial body is weakly magnetic.

20. The accelerometer of claim 12, further comprising Hall sensors for detecting the displacement of the inertial body.

21. The accelerometer of claim 12, further comprising acoustic sensors for detecting the displacement of the inertial body.

22. The accelerometer of claim 12, further comprising a ferromagnetic coating on portions of the inertial body.

23. A sensor comprising:

an inertial body;

a plurality of magnets located generally around 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 a displacement of the inertial body due to acceleration.

24. The sensor of claim 23, further comprising a second circuit that derives the acceleration based on an amount of current through the magnets required to counteract the displacement.

25. The sensor of claim 23, wherein the acceleration includes linear acceleration.

26. The sensor of claim 23, wherein the acceleration includes angular acceleration.

27. The sensor of claim 23, wherein the magnets further comprise permanent magnets.

28. The sensor of claim 23, further comprising sensing coils for detecting the displacement of the inertial body.

29. The sensor of claim 28, wherein each sensing coil is positioned substantially within a corresponding magnet.

30. The sensor of claim 23, further comprising Hall sensors for detecting the displacement of the inertial body.

31. The sensor of claim 23, further comprising acoustic sensors for detecting displacement of the inertial body.

32. The sensor of claim 23, wherein the magnets are located substantially inside the inertial body.

33. The sensor of claim 23, wherein the magnets are located partially inside the inertial body.

34. The sensor of claim 23, further comprising a ferromagnetic coating on portions of the inertial body.

35. The sensor of claim 23, further comprising:

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

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

36. A sensor comprising:

an inertial body;

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

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

37. A sensor comprising:

an 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; and

a circuit that derives acceleration based on the modulation.

38. A sensor comprising:

an 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; and

a controller that drives the magnets in response to the change,

wherein acceleration is derived from current required by the magnets.