Systems and methods for providing signal encoding representative of a signature region in a target

Patent metadata

Field	Value
Publication number	US-9664748-B2
Application number	US-201414306722-A
Country	US
Kind code	B2
Filing date	Jun 17, 2014
Priority date	Jun 20, 2013
Publication date	May 30, 2017
Grant date	May 30, 2017

Abstract

A magnetic field sensor and associated method provide an output signal with first and second different pulses with first and second different pulse widths indicative of first and second different directions of rotation of a moving target. The magnetic field sensor also includes third pulses with an identifiable encoding to indicate when a signature region in the moving target proximate to the magnetic field sensor passes by the magnetic field sensor. The third pulses each comprise respective state transitions and each comprise respective pulse widths with respective fixed predetermined time durations.

First claim

What is clamed is:

1. A magnetic field sensor, comprising:
two or more magnetic field sensing elements responsive to a target capable of moving, the target having a signature region, wherein the two or more magnetic field sensing elements are configured to generate at least two magnetic field signals;
at least two detector circuits coupled to the two or more magnetic field sensing elements, wherein the at least two detector circuits are configured to generate a respective at least two detector signals, wherein each detector signal has respective state transitions with respective rates which identify a rate of movement of the target, and wherein the state transitions of the at least two detector signals have first and second different relative phases, wherein the first and second different relative phases identify respective first and second different directions of movement of the target; and
an output protocol processor coupled to the at least two detector circuits and configured to generate a magnetic field sensor output signal, wherein the magnetic field sensor output signal has a plurality of pulses with respective pulse widths, wherein first pulses with first pulse widths with a first time duration identify that the target is moving in the first direction, wherein second pulses with second pulse widths with a second different time duration identify that the target is moving in the second different direction, wherein third pulses with identifiable encoding identify that the signature region is passing by the magnetic field sensor, wherein the third pulses each comprise respective state transitions and each comprise respective pulse widths with respective fixed predetermined time durations, wherein the fixed predetermined time durations are not affected by a size of the signature region, and wherein the first and second pulse widths of the first and second pulses that identify the first and second different directions do not depend upon respective duty cycles of the at least two magnetic field signals or upon respective duty cycles of the at least two detector signals.

2. The magnetic field sensor of claim 1 , wherein the third pulses have third pulse widths with a third different time duration that are indicative of the signature region passing by the magnetic field sensor.

3. The magnetic field sensor of claim 1 , wherein the target has at least one of a plurality of ferromagnetic teeth and a plurality of valleys, each with a respective width, or a plurality of north pole magnetic regions and a plurality of south pole magnetic regions, each with a respective width, and wherein the signature region comprises a signature structure comprised of at least one signature ferromagnetic tooth, at least one valley, at least one north pole magnetic region, or at least one south pole magnetic region, with a width different than the widths of the plurality of ferromagnetic teeth, or the widths of plurality of valleys, or the widths of the plurality of north pole magnetic regions, or the widths of the plurality of south pole magnetic regions.

4. The magnetic field sensor of claim 1 , wherein positions of the third pulses within the plurality of pulses are determined according to threshold crossings of at least one of the magnetic field signals.

5. The magnetic field sensor of claim 1 , wherein positions of the third pulses within the plurality of pulses are determined according to a time prediction of where one of the first pulses or one of the second pulses would occur if the signature region were not provided.

6. The magnetic field sensor of claim 1 , wherein positions of the third pulses within the plurality of pulses are determined according to a position of a next one of the first pulses or a next one of the second pulses that would occur after the signature region passes by the magnetic field sensor.

7. The magnetic field sensor of claim 1 , wherein the third pulses are spaced an equal distance in time between the first pulses or the second pulses and are substantially centered with respect to the signature region.

8. The magnetic field sensor of claim 1 , wherein the third pulses are spaced an unequal distance in time between the first pulses or the second pulses and are not centered with respect to the signature region.

9. The magnetic field sensor of claim 1 , wherein positions of the third pulses within the plurality of pulses are determined according to phase differences between two of the at least two magnetic field signals.

10. The magnetic field sensor of claim 1 , further comprising a counter for counting a quantity of the first pulses or a quantity of the second pulses between two or more of the third pulses to identify a passing or a failing condition.

11. The magnetic field sensor of claim 1 , wherein two of more of the third pulses are generated each time that the signature region passes by the magnetic field sensor.

12. A method used in a magnetic field sensor, comprising:
generating at least two magnetic field signals with two or more magnetic field sensing elements responsive to a target capable of moving, the target having a signature region;
generating a respective at least two detector signals with at least two detector circuits coupled to the two or more magnetic field sensing elements, wherein each detector signal has respective state transitions with respective rates that identify a rate of movement of the target, and wherein the state transitions of the at least two detector signals have first and second different relative phases, wherein the first and second different relative phases identify respective first and second different directions of movement of the target;
identifying the rate of movement;
identifying the first and second different directions of movement; and
generating a magnetic field sensor output signal, wherein the magnetic field sensor output signal has a plurality of pulses with respective pulse widths, wherein first pulses with first pulse widths with a first time duration are indicative of the target moving in the first direction, wherein second pulses with second pulse widths with a second different time duration identify that the target is moving in the second different direction, wherein third pulses with identifiable encoding identify that the signature region is passing by the magnetic field sensor, wherein the third pulses each comprise respective state transitions and each comprise respective pulse widths with respective fixed predetermined time durations, wherein the fixed predetermined time durations are not affected by a size of the signature region, and wherein the first and second pulse widths of the first and second pulses that identify the first and second different directions do not depend upon respective duty cycles of the at least two magnetic field signals or upon respective duty cycles of the at least two detector signals.

13. The method of claim 12 , wherein the third pulses have third pulse widths with a third different time duration that are indicative of the signature region passing by the magnetic field sensor.

14. The method of claim 12 , wherein the target has at least one of a plurality of ferromagnetic teeth and a plurality of valleys, each with a respective width, or a plurality of north pole magnetic regions and a plurality of south pole magnetic regions, each with a respective width, and wherein the signature region comprises a signature structure comprised of at least one signature ferromagnetic tooth, at least one valley, at least one north pole magnetic region, or at least one south pole magnetic region, with a width different than widths of the plurality of ferromagnetic teet

Assignees

• Allegro Microsystems Llc

Inventors

• Friedrich Andreas P
• Foletto Andrea
• Towne Jay M
• Morris Michael
• Shoemaker Eric

Classifications

• G01P3/487

  delivered by rotating magnets · CPC title

• G01R33/09

  Magnetoresistive devices · CPC title

• G01P3/488

  delivered by variable reluctance detectors · CPC title

• G01D5/24461

  by redundancy or plausibility · CPC title

• G01P13/045

  with speed indication · CPC title