Position sensing transducer

• US 9,410,791 B2
• Filed: 12/21/2011
• Issued: 08/09/2016
• Est. Priority Date: 12/24/2010
• Status: Active Grant

• Current Assignee: Cambridge Integrated Circuits Limited
• Original Assignee: Cambridge Integrated Circuits Limited
• Inventors: Ely, David
• Primary Examiner(s): Koval, Melissa
• Assistant Examiner(s): Monsur, Nasima
• Application Number:
  US13/989,776
• Publication Number:
  US 20130257417A1
• Time in Patent Office: 1,693 Days
• Field of Search: 324/207.22, 324/207.15, 324/207.25, 324/633, 324/207.12, 324/207.18, 324/242, 324/257, 324/652, 324/654, 324/655, 324/207.17, 324/207.24, 324/207.16, 324/202, 324/207.2, 324/225, 345/158, 345/153, 702/145, 702/150, 702/151, 702/65, 384/448, 738/620.46, 463/39, 463/43
• US Class Current: 1/1
• CPC Class Codes: G01B 7/30 for measuring angles or tapers; for testing the alignment of axes
• CPC Class Codes: G01D 5/2013 by a movable ferromagnetic element, e.g. a core G01D5/2033 takes precedence

Abstract

Position sensors to inductively sense a position of a target relative to a number of sensor coils are described. In one embodiment, the target comprises first, second, and third portions positioned on either side of an axis of rotation, such that lateral misalignment between the target and the sensors is compensated between the interaction of the different portions and the sensor coils. In another embodiment, the target comprises first and second portions that are separated along the measurement path such that in a first range of relative positions, the first portion is adjacent to the sensor coils and in a second range of relative positions, the second portion is adjacent to the sensor coils. The first and second portions are asymmetrically arranged relative to the sensor coils such that when each portion is adjacent the same portion of the sensor coils, different signals are induced in the sensor coils.

Claims

1. A transducer for a rotary position sensor comprising:

one or more coils;

i) each arranged along and defining a circular measurement path having an inner radius and an outer radius centered about a sensor axis; and

ii) each coil extending between the inner radius and the outer radius;

a target having first, second, and third portions adjacent to the one or more coils;

the first, second and third portions being circumferentially spaced apart from each other around the circular measurement path and arranged relative to a target axis;

i) so that, during relative rotation of the target and the one or more coils around the circular measurement path, the first portion is always positioned between the inner radius and the outer radius; and

ii) so that, during relative rotation of the target and the one or more coils around the circular measurement path, the second and third portions are always positioned adjacent to the inner radius or the outer radius; and

iii) so that the first, second and third portions each lie on a respective different diameter that passes through the target axis;

wherein the target is arranged to magnetically couple with the one or more coils so that signals are generated that depend on the relative rotational position of the target and the one or more coils; and

wherein the second and third portions of the target are arranged on either side of the target axis to compensate for misalignments between the target axis and the sensor axis.

2. A transducer according to claim 1, wherein the one or more coils are arranged relative to the sensor axis so that the signals that are generated vary sinusoidally with the relative rotational position.

3. A transducer according to claim 1, wherein the target comprises one or more of:

i) a plurality of windings arranged on either side of the target axis;

ii) a plurality of wound magnetic members arranged on either side of the target axis;

iii) a banana shaped coil; and

iv) air cored coils arranged on either side of the target axis.

4. A transducer according to claim 1, wherein the target is asymmetric relative to the one or more coils.

5. A transducer according to claim 4, wherein the target comprises asymmetric windings that have an oval or an egg shape.

6. A transducer according to claim 1, wherein the target comprises a resonator and wherein the transducer comprises one or more excitation coils for energizing the resonator and one or more sensor coils in which the signals are generated.

7. A transducer according to claim 6, wherein the one or more coils arranged relative to the sensor axis between the inner radius and the outer radius are at least one of:

the one or more excitation coils and the one or more sensor coils.

8. A transducer according to claim 6, wherein at least one of:

i) the one or more excitation coils; and

ii) the one or more sensor coils;

is patterned so that the magnetic coupling between the target and the at least one of the one or more excitation coils and the one or more sensor coils varies sinusoidally with the relative rotational position.

9. A transducer according to claim 1, wherein the coils lie in a plane and the target is arranged to rotate in a plane that is parallel to the planar coils.

10. A transducer according to claim 1, wherein the target comprises first and second elongate field concentrating members having a winding thereon, wherein the winding on each field concentrating member is offset from a central position of the corresponding field concentrating member.

11. A transducer for a position sensor comprising:

first and second coils arranged along at least a portion of a measurement path; and

a target having first and second target portions that are separated along the measurement path and each target portion having a winding and first and second sub-portions that are separated in a direction perpendicular to the measurement path, the winding of the first target portion being electrically connected to the winding of the second target portion such that current can flow between the winding of the first target portion and the winding of the second target portion;

wherein the target and the first and second coils are relatively moveable;

wherein the magnetic coupling between the first coil and the second coil is modulated by the presence of the target to generate signals that depend on the relative position between the target and the first and second coils; and

wherein the first and second target portions are asymmetrically arranged relative to the first and second coils such that the magnetic coupling between the first coil and the second coil, when the first sub-portion of the first target portion is adjacent a location of the first coil, is opposite to the magnetic coupling between the first coil and the second coil, when the first sub-portion of the second target portion is adjacent the same location of the first coil.

12. A position sensor comprising a transducer comprising:

one or more coils;

i) each arranged along and defining a circular measurement path having an inner radius and an outer radius centered about a sensor axis; and

ii) each coil extending between the inner radius and the outer radius of the measurement path;

a target having first, second, and third portions adjacent to the one or more coils;

the first, the second and the third portions being circumferentially spaced apart from each other around the circular measurement path and arranged relative to a target axis;

i) so that, during relative rotation of the target and the one or more coils around the circular measurement path, the first portion is always positioned between the inner radius and the outer radius; and

ii) so that, during relative rotation of the target and the one or more coils around the circular measurement path, the second and the third portions are always positioned adjacent to the inner radius or the outer radius and iii) so that the first, second and third portions each lie on a respective different diameter that passes through the target axis;

wherein the target is arranged to magnetically couple with the one or more coils so that signals are generated that depend on the relative rotational position of the target and the one or more coils; and

wherein the second and the third portions of the target are arranged on either side of the target axis to compensate for misalignments between the target axis and the sensor axis, wherein the position sensor generates signals that vary with the relative position of the target and the first and second coils and the position sensor includes processing circuitry that processes the signals to determine the relative position.

13. A method of determining rotary position comprising:

providing one or more coils;

i) each arranged along and defining a circular measurement path having an inner radius and an outer radius centered about a sensor axis; and

ii) each coil extending between the inner radius and the outer radius of the measurement path;

providing a target having first, second and third portions adjacent to the one or more coils;

the first, second, and third portions being circumferentially spaced apart from each other around the circular measurement path and being arranged relative to a target axis;

i) so that, during relative rotation of the target and the one or more coils around the circular measurement path, the first portion is always positioned between the inner radius and the outer radius; and

ii) so that, during relative rotation of the target and the one or more coils around the circular measurement path, the second and third portions are always positioned adjacent the inner radius or the outer radius; and

iii) so that the first, second and third portions each lie on a respective different diameter that passes through the target axis;

causing the target to magnetically couple with the one or more coils to generate signals that depend on the relative rotational position between the target and the sensor coils;

processing the generated signals to determine the relative rotational position; and

compensating for misalignments between the target axis and the sensor axis by arranging the second and third portions of the target on either side of the target axis.

14. A position sensing method comprising:

arranging first and second coils along at least a portion of a measurement path;

providing a target having first and second target portions that are separated along the measurement path and each target portion having a winding and first and second sub-portions that are separated in a direction perpendicular to the measurement path, the winding of the first target portion being electrically connected to the winding of the second target portion such that current can flow between the winding of the first target portion and the winding of the second target portion;

arranging the target and the one or more sensor coils so that they are relatively moveable and so that the magnetic coupling between the first coil and the second coil is modulated by the presence of the target to generate signals that depend on the relative position between the target and the first and second coils;

arranging the first and second target portions asymmetrically relative to the first and second coils such that the magnetic coupling between the first coil and the second coil, when the first sub-portion of the first target portion is adjacent a location of the first coil, is opposite to the magnetic coupling between the first coil and the second coil, when the first sub-portion of the second target portion is adjacent the same location of the first coil; and

processing the generated signals to determine the relative position of the target and the one or more sensor coils.