Measuring linear velocity

• US 8,183,854 B2
• Filed: 11/07/2008
• Issued: 05/22/2012
• Est. Priority Date: 11/07/2008
• Status: Active Grant

• Current Assignee: Calnetix Technologies, LLC (General Electric Company)
• Original Assignee: Calnetix Technologies, LLC (General Electric Company)
• Inventors: Filatov, Alexei V.
• Primary Examiner(s): Hollington, Jermele M
• Assistant Examiner(s): Nguyen, Trung Q
• Application Number:
  US12/267,517
• Publication Number:
  US 20100117627A1
• Time in Patent Office: 1,292 Days
• Field of Search: None
• US Class Current: 324/163
• CPC Class Codes: F16C 32/0446 Determination of the actual position of the moving member, e.g. details of sensors
• CPC Class Codes: F16C 32/0476 with active support of one degree of freedom, e.g. axial magnetic bearings
• CPC Class Codes: G01P 3/52 by measuring amplitude of generated current or voltage
• CPC Class Codes: H02K 11/225 Detecting coils
• CPC Class Codes: H02K 41/02 Linear motors; Sectional motors

Abstract

An apparatus for measuring linear velocity of a movable element relative to a stationary element includes a magnetic element fixed in relation to the stationary element. A soft-magnetic yoke is fixed in relation to the movable element to move with the movable element and is in non-contact relation with the magnetic element. A yoke pole is positioned proximate to the magnetic element and spaced therefrom by an air gap. The pole is magnetically coupled to the magnetic element so that a magnetic flux is generated in the air gap substantially orthogonal to the axis of motion. A conductive coil is coiled around a coil axis and is fixed in relation to the stationary element with the coil axis substantially parallel to the axis of movement. The coil is in non-contact relation with the yoke and resides between the magnetic element and the pole of the yoke in the magnetic flux.

Claims

1. An apparatus for measuring linear velocity of a movable element relative to a stationary element along an axis of movement, the apparatus comprising:

a magnetic element fixed in relation to the stationary element, the magnetic element having a permanent magnet;

a soft-magnetic yoke fixed in relation to the movable element to move with the movable element relative to the stationary element, the soft-magnetic yoke being in non-contact relation with the magnetic element and having a pole positioned proximate to the magnetic element and spaced from the magnetic element by an air gap, the pole magnetically coupled to the magnetic element so that a magnetic flux is generated in the air gap substantially orthogonal to the axis of movement; and

a conductive coil coiled around a coil axis, the conductive coil fixed in relation to the stationary element with the coil axis substantially parallel to the axis of movement, in non-contact relation with the soft-magnetic yoke and residing between the magnetic element and the pole of the soft-magnetic yoke in the magnetic flux.

2. The apparatus of claim 1, wherein:

the magnetic element further comprises a first soft-magnetic pole element and a second soft-magnetic pole element; and

the permanent magnet has a pole axis extending through its north and south poles and the pole axis is oriented substantially parallel to axis of movement, the first soft-magnetic pole element magnetically coupled with the north pole of the permanent magnet and the second soft-magnetic pole element magnetically coupled with the south pole of the magnet.

3. The apparatus of claim 2, wherein the first soft-magnetic pole element and the second soft-magnetic pole element are cylindrical and substantially concentrically received within a cylindrical opening defined by the poles of the soft-magnetic yoke.

4. The apparatus of claim 2, wherein the first soft-magnetic pole element and the second soft-magnetic pole element define cylindrical openings within which the soft-magnetic yoke is received.

5. The apparatus of claim 1, wherein the conductive coil comprises a plurality of turns.

6. The apparatus of claim 1, wherein:

the conductive coil is a first conductive coil;

the soft-magnetic yoke further comprises a second pole positioned proximate to the magnetic element and spaced from the magnetic element by an air gap, the second pole magnetically coupled to the magnetic element so that a magnetic flux is generated in the air gap substantially orthogonal to the axis of movement; and

the apparatus further comprises a second conductive coil coiled around the coil axis, the second conductive coil fixed in relation to the stationary element being in non-contact relation with the soft-magnetic yoke and residing between the magnetic element and the second pole of the soft-magnetic yoke in the magnetic flux.

7. The apparatus of claim 6, wherein the first conductive coil is coupled to the second conductive coil in series so that a voltage induced in the first and second conductive coils by movement of the yoke is additive.

8. The apparatus of claim 1, wherein the movable element rotates about the axis of movement and the soft-magnetic yoke is fixed in relation to the movable element to move with the movable element along the axis of movement and rotate with the movable element about the axis of movement.

9. The apparatus of claim 1, further comprising an electronics module electrically coupled to the conductive coil, wherein the conductive coil is fixed in relation to the electronics module.

10. The apparatus of claim 9, wherein the magnet is fixed in relation to the electronics module.

11. A method of measuring linear velocity, the method comprising:

communicating magnetic flux between a magnet fixed in relation to a stationary element and a soft-magnetic structure fixed in relation to a movable element;

conducting the magnetic flux through a magnetic circuit, the magnetic circuit including the magnet, the soft-magnetic structure, and a conductive coil; and

generating a linear velocity measurement as a voltage proportional to a linear velocity of the movable element in relation to the stationary element on the conductive coil, the conductive coil fixed in relation to the magnet and residing between the magnet and the soft-magnetic structure.

12. The method of claim 11, further comprising communicating the voltage in the conductive coil to a current amplifier and communicating current from the current amplifier to an actuator to generate a force on the movable element proportional to the velocity of the movable element.

13. The method of claim 11, wherein the movable element rotates about an axis of movement, and the soft-magnetic structure is fixed in relation to the movable element to move with the movable element along the axis of movement and rotate with the movable element about the axis of movement.

14. An electric machine system, the system comprising:

a first assembly that moves in relation to a second assembly along an axis of movement,

a magnet fixed in relation to the second assembly;

a coil wound around a coil axis, the coil fixed in relation to the second assembly with the axis substantially parallel to the axis of movement;

a soft-magnetic structure fixed in relation to the first assembly to move with the first assembly in relation to the second assembly;

the magnet and the soft-magnetic structure cooperating to define a magnetic circuit conducting magnetic flux from the magnet through the coil substantially perpendicular to the coil axis and into the soft-magnetic structure; and

an electronics module in electrical communication with the coil and fixed in relation to the second assembly.

15. The system of claim 14, wherein the magnet has a pole axis extending through its north and south poles and the pole axis is oriented substantially parallel to axis of movement, and wherein the system further comprises a first soft-magnetic pole element in magnetic communication with the north pole of the magnet and a second soft-magnetic pole element in magnetic communication with the south pole of the magnet.

16. The system of claim 14, wherein the first assembly is a rotor that rotates about the axis of movement and the second assembly is a stator.

17. The system of claim 14, further comprising a damper actuator in communication with the electronics module, the damper actuator being fixed in relation to the second assembly;

and

wherein the electronics module is adapted to power the damper actuator to apply a force on the first assembly along the axis of movement, the force being determined as a function of a linear velocity of the first assembly.

18. The system of claim 17, wherein the electronics module comprises a current amplifier adapted to output a current that is proportional to a voltage on the coil, and the force is proportional to the linear velocity of the first assembly.

19. A method comprising:

communicating magnetic flux between a magnet fixed in relation to a stationary element and a soft-magnetic structure fixed in relation to a movable element;

conducting the magnetic flux through a magnetic circuit, the magnetic circuit including the magnet, the soft-magnetic structure, and a conductive coil;

generating a voltage proportional to a linear velocity of the movable element in relation to the stationary element on the conductive coil, the conductive coil fixed in relation to the magnet and residing between the magnet and the soft-magnetic structure;

communicating the voltage in the conductive coil to a current amplifier; and

communicating current from the current amplifier to an actuator to generate a force on the movable element proportional to the velocity of the movable element.

20. A method comprising:

communicating magnetic flux between a magnet fixed in relation to a stationary element and a soft-magnetic structure fixed in relation to a movable element, the movable element configured to rotate about an axis of movement, the soft-magnetic structure fixed in relation to the movable element to move with the movable element along the axis of movement and to rotate with the movable element about the axis of movement;

conducting the magnetic flux through a magnetic circuit, the magnetic circuit including the magnet, the soft-magnetic structure, and a conductive coil; and

generating a voltage proportional to a linear velocity of the movable element in relation to the stationary element on the conductive coil, the conductive coil fixed in relation to the magnet and residing between the magnet and the soft-magnetic structure.