SENSOR ARRANGEMENT FOR POSITION SENSING

• US 20160265939A1
• Filed: 08/13/2015
• Published: 09/15/2016
• Est. Priority Date: 03/12/2015
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Tomas, Tuma, Haeberle, Walter, Pantazi, Angeliki, Sebastian, Abu
• Granted Patent: US 9,945,693 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01B 7/14 for measuring distance or clearance between spaced objects or spaced apertures G01B7/30 takes precedence
• CPC Class Codes: G01D 5/16 by varying resistance
• CPC Class Codes: G01R 33/09 Magnetoresistive devices
• CPC Class Codes: G01V 3/081 the magnetic field is produced by the objects or geological structures characterised by the method of magnetic field measurement G01R33/00

Abstract

A method for determining of a position of an object using a sensor arrangement that includes a first magnetoresistive element and a second magnetoresistive element. A source provides a magnetic field with first and second magnetic poles. The source is arranged between the first magnetoresistive element and the second magnetoresistive element with the first magnetic pole facing the first magnetoresistive element and the second magnetic pole facing the second magnetoresistive element. The first magnetoresistive element is arranged in the magnetic field and provides a first output signal dependent on a position of the first magnetoresistive element relative to the magnetic field source. The second magnetoresistive element is arranged in the magnetic field and provides a second output signal dependent on a position of the second magnetoresistive element relative to the magnetic field source. A measurement unit determines a position of the magnetic field source relative to the first and the second magnetoresistive elements dependent on the first output signal and the second output signal.

Claims

1. A method for determining the position of an object, comprising:

coupling one of

a magnetic field source (3) providing a magnetic field with a first magnetic pole (N) and a second magnetic pole (S) and

a first and a second magnetoresistive element (1, 2) with the object (5),

arranging the magnetic field source (3) between the first magnetoresistive element (1) and the second magnetoresistive element (2) with the first magnetic pole (N) facing the first magnetoresistive element (1) and the second magnetic pole (S) facing the second magnetoresistive element (2) to form a sensor arrangement,

receiving, at a measurement unit, output signals (R1, R2) from the first and the second magnetoresistive elements (1, 2) dependent on their position (x) relative to the magnetic field source (3), and

determining, by the measurement unit, a position of the object (5) dependent on the first output signal (R1) and the second output signal (R2).

2. The method as claimed in claim 1, wherein each of the magnetoresistive elements (1, 2) comprises a stack (11) of layers including at least a conductive layer (112) in between two magnetic layers (111, 113) which layers have a longitudinal extension (L) along a longitudinal axis (X) and a lateral extension along a transverse axis (Y), said method comprising:

defining a dipole axis (DA) of the magnetic field source by the first and the second magnetic pole (N, S) extending along a vertical axis (Z) orthogonal to a plane defined by the longitudinal axis (X) and the transverse axis (Y).

3. The method as claimed in claim 2, further comprising:

moving the magnetic field source (3) relative to the first and second magnetoresistive element (1, 2) along the longitudinal axis (X), a position (x) thereof along the longitudinal axis (X) is to be sensed by the sensor arrangement, and

determining, by the measurement unit, the position (x) along the longitudinal axis (X) by adding the first output signal (R1) and the second output signal (R2).

4. The method as claimed in claim 2, further comprising:

moving the magnetic field source (3) relative to the first and second magnetoresistive element (1, 2) along the vertical axis (Z), a position (z) thereof along the vertical axis (Z) is to be sensed by the sensor arrangement, and

determining, by the measurement unit, the position (z) along the vertical axis (Z) by computing a difference between the first output signal (R1) and the second output signal (R2).

5. The method as claimed in claim 2, further comprising:

arranging multiple first magnetoresistive elements (1) in the magnetic field in a row along the longitudinal axis (X) and facing the first magnetic pole (N), and

arranging additional multiple second magnetoresistive elements (2) in the magnetic field in a row along the longitudinal axis (X) and facing the second magnetic pole (S).

6. The method as claimed in claim 5, wherein the magnetic field source (3) is dimensioned relative to the multiple first magnetoresistive elements (1) such that the magnetic field only affects a single (1a) of the multiple first magnetoresistive elements (1) at a time but not adjacent first magnetoresistive elements (1b, 1c), and

wherein the magnetic field source (3) is a permanent magnet which has a width (W) less than the longitudinal extension (L) of the first magnetoresistive elements (1).

7. The method as claimed in claim 6, further comprising:

identifying, by the measurement unit, the single first magnetoresistive element (1a) out of the multiple magnetoresistive elements (1) that shows a change in its first output signal (R1) which change results from the magnetic field source (3) passing by the single first magnetoresistive element (1a), and

deriving, by the measurement unit, the position (x) along the longitudinal axis (X) from a known position of the single first magnetoresistive element (1a) within the row of the multiple first magnetoresistive elements (1).

8. The method as claimed in claim 5, wherein the magnetic field source (3) is dimensioned relative to the multiple first magnetoresistive elements (1) such that the magnetic field not only affects a single (1a) of the multiple first magnetoresistive elements (1) but also adjacent first magnetoresistive elements (1b, 1c), and

wherein the magnetic field source (3) is a permanent magnet which has a width (W) along the longitudinal axis (X) exceeding the longitudinal extension (L) of the first magnetoresistive element (1).

9. The method as claimed in claim 8, wherein a magnetization orientation of both of the magnetic layers (111, 113) of the multiple first magnetoresistive elements (1) is unpinned, said method further comprising:

subtracting, by the measurement unit, first output signals (R1) of adjacent first magnetoresistive elements (1) from each other, and

determining, by the measurement unit, the position (x) along the longitudinal axis (X) dependent on a resulting difference signal.

10. The method as claimed in claim 8, wherein a magnetization orientation of one of the magnetic layers (111, 113) of the multiple first magnetoresistive elements (1) is pinned, said method further comprising:

adding, by the measurement unit, the first output signals (R1) of adjacent first magnetoresistive elements (1), and

determining, by the measurement unit, the position (x) along the longitudinal axis (X) dependent on a resulting sum signal.

11. The method as claimed in claim 5, further comprising:

arranging the multiple first magnetoresistive elements (1) in the row offset from each other along the vertical axis (Z).

12. The method as claimed in claim 6, further comprising:

arranging a middle first magnetoresistive element (1m) at a closest vertical distance from the magnetic field source (3) amongst the multiple first magnetoresistive elements (1) of the row, and

arranging outmost first magnetoresistive elements (1) at a farthest vertical distance from the magnetic field source (3) amongst the multiple first magnetoresistive elements (1) of the row.

13. The method of claim 1, further comprising:

coupling one of the magnetoresistive elements (1, 2) and the magnetic field source (3) to an object (5), the position of which object (5) is to be sensed by the sensor arrangement.