Reduced offset high accuracy induced current absolute position transducer

• US 6,329,813 B1
• Filed: 12/17/1998
• Issued: 12/11/2001
• Est. Priority Date: 12/17/1998
• Status: Expired due to Term

• Current Assignee: Mitutoyo Corporation
• Original Assignee: Mitutoyo Corporation
• Inventors: Andermo, Nils Ingvar
• Primary Examiner(s): PATIDAR, JAY M
• Application Number:
  US09/213,268
• Time in Patent Office: 1,090 Days
• Field of Search: 324/207.12, 324/207.17-207.19, 324/207.24, 324/207.25, 307/116-118, 341/15, 340/870.32, 340/870.34-870.36, 318/653, 318/657, 318/661, 336/45, 336/75, 336/77, 336/79, 336/115, 336/129
• US Class Current: 324/207.17
• CPC Class Codes: G01B 3/205 provided with a counter for digital indication of the measured dimension
• CPC Class Codes: G01D 5/2086 by movement of two or more coils with respect to two or more other coils

Abstract

An inductive absolute position sensor has at least one magnetic field generator that generates a first changing magnetic flux in a first flux region. A plurality of coupling loops have a first plurality of coupling loop portions spaced at an interval related to a first wavelength along a measuring axis and a second plurality of coupling loop portions spaced at an interval related to a second wavelength along a measuring axis. One of the first plurality of coupling loop portions and the second plurality of coupling loop portions are inductively coupled to a first changing magnetic flux from a transmitter winding in a first flux region to generate a second changing magnetic flux outside the first flux region in the other of the first plurality of coupling loop portions and the second plurality of coupling loop portions. A magnetic flux sensor is positioned outside the first flux region and is responsive to the second changing magnetic flux to generate a position-dependent output signal. The output signal varies at the first or second wavelength of the corresponding other of the first plurality of coupling loop portions and the second plurality of coupling loop portions that generates the second changing magnetic flux.

Claims

1. An inductive absolute position sensor, comprising:

a first readhead member;

a second scale member having a measuring axis, the first readhead member and second scale member movable relative to each other along the measuring axis;

at least one magnetic field generator on the first readhead member, each at least one magnetic field generator responsive to a drive signal to generate a first changing magnetic flux in a first flux region;

a plurality of flux coupling loops on the second scale member, each having at least a first coupling loop portion and a second coupling loop portion connected to the first coupling loop portion by connecting conductors, the first plurality of coupling loop portions spaced at an interval related to a first wavelength along the measuring axis and the second plurality of coupling loop portions spaced at an interval related to a second wavelength along the measuring axis, the plurality of flux coupling loops responsive to the first changing magnetic flux in the first plurality of coupling loop portions to generate at least a second changing magnetic flux outside the first flux region in the second plurality of coupling loop portions; and

at least one magnetic flux sensor positioned outside the first flux region and responsive to the second changing magnetic flux to generate an output signal that is a function of the relative position between the at least one magnetic flux sensor, and the plurality of flux coupling loops, the output signal of the at least one magnetic flux sensor varying at the second wavelength.

2. The inductive absolute position sensor of claim 1, the at least one magnetic field generator comprising a first magnetic field generator and a second magnetic field generator.

3. The inductive absolute position sensor of claim 2, further comprising a second magnetic flux sensor, the first coupling loop portions having a polarity and every other one of the second coupling loop portions having a polarity opposite to the polarity of the corresponding first coupling loop portions.

4. The inductive absolute position sensor of claim 1, further comprising a second magnetic flux sensor.

5. The inductive absolute position sensor of claim 4, further comprising a third magnetic flux sensor.

6. The inductive absolute position sensor of claim 5, further comprising:

a fourth magnetic flux sensor;

a second magnetic field generator, the first magnetic field generator having a first portion and a second portion;

a third magnetic field generator;

a second plurality of flux coupling loops, each having a first coupling loop portion and a second coupling loop portion; and

a third plurality of flux coupling loops, each having a first coupling loop portion and a second coupling loop portion;

the first loop portions of the first plurality of coupling loops positioned to inductively couple to the first portion of the first magnetic field generator and the third magnetic flux sensor, the first loop portions of the second plurality of coupling loops positioned to inductively couple to the second portion of the first magnetic field generator and the second magnetic flux sensor, the second loop portions of the first plurality of coupling loops and the second plurality of coupling loops positioned to inductively couple to the second magnetic field generator and the first magnetic flux sensor, the second loop portions of the first plurality of coupling loops alternating along the measuring axis with the second loop portions of the second plurality of coupling loops, the first plurality of coupling loop portions of the third plurality of coupling loops positioned to inductively couple to the third magnetic field generator, and the fourth magnetic flux sensor positioned to inductively couple to the second plurality of coupling loop portions of the third plurality of coupling loops.

7. The inductive absolute position sensor of claim 4, further comprising:

a first connecting conductor; and

a second connecting conductor, the at least one magnetic field generator comprising a single magnetic field generator, the plurality of flux coupling loops further comprising a third coupling loop portion, the first connecting conductors connecting the first coupling loop portion to the third coupling loop portion, the second connecting conductors connecting the second coupling loop portions to the first coupling loop portions, the second coupling loop portions positioned to inductively couple to the first magnetic flux sensor along the measuring axis, the third coupling loop portions positioned to inductively couple to the second magnetic flux sensor, and the first coupling loop portions positioned to inductively couple to the magnetic field generator.

8. The inductive absolute position sensor of claim 7, every other one of the first connecting conductors being twisted and every other one of the second connecting conductors being twisted.

9. The inductive absolute position sensor of claim 1, the first magnetic field generator comprising a first transmitter winding portion and a second transmitter winding portion.

10. The inductive absolute position sensor of claim 1, further comprising a second plurality of flux coupling loops, each of the second plurality of flux coupling loops having a first loop portion and a second loop portion.

11. The inductive absolute position sensor of claim 10, further comprising:

a second magnetic flux generator;

a first connecting conductor connecting the first coupling loop portion and the second coupling loop portion of the first plurality of flux coupling loops; and

a second connecting conductor connecting the first coupling loop portion and the second coupling loop portion of the second plurality of flux coupling loops, the first magnetic flux generator positioned to inductively couple to the first coupling loop portions of the first plurality of flux coupling loops, the magnetic flux sensor positioned to inductively couple to the second coupling loop portions of the first plurality of flux coupling loops and the second coupling loop portions of the second plurality of flux coupling loops, and the second magnetic flux generator positioned to inductively couple to the first coupling loop portions of the second plurality of flux coupling loops.

12. The inductive absolute position sensor of claim 11, every other one of the first connecting conductors being twisted and every other one of the second connecting conductors being twisted.

13. The inductive absolute position sensor of claim 10, further comprising:

a second magnetic flux generator having a first portion and a second portion, the first magnetic flux generator having a first portion and a second portion;

a second magnetic flux sensor; and

a third magnetic flux sensor, the first coupling loop portions of the first plurality of flux coupling loops positioned to inductively couple to the first portion of the first magnetic flux generator and the second magnetic flux sensor, the first coupling loop portions of the second plurality of flux coupling loops positioned to inductively couple to the second portion of the first magnetic flux generator and the third magnetic flux sensor, the second coupling loop portions of both the first plurality of coupling loops and the second plurality of coupling loops being interleaved along the measuring axis and alternately positioned to inductively couple to the first portion and the second portion of the first magnetic flux generator and positioned to inductively couple to both the first magnetic flux sensor and the second magnetic flux generator.

14. The inductive absolute position sensor of claim 10, each magnetic flux sensor comprising at least one receiver winding and each magnetic field generator comprising at least one transmitter winding portion, wherein:

the first coupling loop portions of the first plurality of coupling loops is positioned to inductively couple to at least a first receiver winding and a first transmitter winding portion of the first magnetic field generator, the second coupling loop portions of both the first and second pluralities of coupling loops is positioned to inductively couple to at least a second receiver winding and the second magnetic field generator, and the first coupling loop portions of the second plurality of coupling loops is positioned to inductively couple to at least a third receiver winding and a second transmitter winding portion of the first magnetic field generator.

15. The inductive absolute position sensor of claim 14, further comprising connecting conductors connecting the first coupling loop portion and second coupling loop portion of each flux coupling loop, the connecting conductors being twisted for every other one of the flux coupling loops in each of the first and second pluralities of coupling loops.

16. The inductive absolute position sensor of claim 1, further comprising connecting conductors connecting the first coupling loop portion and the second coupling loop portion, every other one of the connecting conductors being twisted.

17. An inductive absolute position sensor, comprising:

a first readhead member;

a second scale member having a measuring axis, the first readhead member and second scale member movable relative to each other along the measuring axis;

at least one magnetic field generator on the first readhead member, each at least one magnetic field generator responsive to a drive signal to generate a first changing magnetic flux in a first flux region;

a plurality of flux coupling loops on the second scale member, each having at least a first coupling loop portion and a second coupling loop portion, the first plurality of coupling loop portions spaced at an interval related to a first wavelength along the measuring axis and the second plurality of coupling loop portions spaced at an interval related to a second wavelength along the measuring axis, the plurality of flux coupling loops responsive to the first changing magnetic flux in the first plurality of coupling loop portions to generate at least a second changing magnetic flux outside the first flux region in the second plurality of coupling loop portions;

at least one magnetic flux sensor positioned outside the first flux region and responsive to the second changing magnetic flux to generate an output signal that is a function of the relative position between the at least one magnetic flux sensor, and the plurality of flux coupling loops, the output signal of the at least one magnetic flux sensor varying at the second wavelength;

a second magnetic flux sensor;

first connecting conductors; and

second connecting conductors, the at least one magnetic field generator comprising a single magnetic field generator, the plurality of flux coupling loops further comprising a third coupling loop portion, the first connecting conductors connecting the first coupling loop portion to the third coupling loop portion, the second connecting conductors connecting the second coupling loop portions to the first coupling loop portions, the second coupling loop portions positioned to inductively couple to the first magnetic flux sensor along the measuring axis, the third coupling loop portions positioned to inductively couple to the second magnetic flux sensor, and the first coupling loop portions positioned to inductively couple to the magnetic field generator.

18. The inductive absolute position sensor of claim 17, every other one of the first connecting conductors being twisted and every other one of the second connecting conductors being twisted.

19. An inductive absolute position sensor, comprising:

a first readhead member;

a second scale member having a measuring axis, the first readhead member and second scale member movable relative to each other along the measuring axis;

at least one magnetic field generator on the first readhead member, each at least one magnetic field generator responsive to a drive signal to generate a first changing magnetic flux in a first flux region;

a plurality of flux coupling loops on the second scale member, each having at least a first coupling loop portion and a second coupling loop portion, the first plurality of coupling loop portions spaced at an interval related to a first wavelength along the measuring axis and the second plurality of coupling loop portions spaced at an interval related to a second wavelength along the measuring axis, the plurality of flux coupling loops responsive to the first changing magnetic flux in the first plurality of coupling loop portions to generate at least a second changing magnetic flux outside the first flux region in the second plurality of coupling loop portions,

at least one magnetic flux sensor positioned outside the first flux region and responsive to the second changing magnetic flux to generate an output signal that is a function of the relative position between the at least one magnetic flux sensor, and the plurality of flux coupling loops, the output signal of the at least one magnetic flux sensor varying at the second wavelength;

a second magnetic flux sensor;

a third magnetic flux sensor;

a fourth magnetic flux sensor;

a second magnetic field generator, the first magnetic field generator having a first portion and a second portion;

a third magnetic field generator;

a second plurality of flux coupling loops, each having a first coupling loop portion and a second coupling loop portion; and

a third plurality of flux coupling loops, each having a first coupling loop portion and a second coupling loop portion;

the first loop portions of the first plurality of coupling loops positioned to inductively couple to the first portion of the first magnetic field generator and the third magnetic flux sensor, the first loop portions of the second plurality of coupling loops positioned to inductively couple to the second portion of the first magnetic field generator and the second magnetic flux sensor, the second loop portions of the first plurality of coupling loops and the second plurality of coupling loops positioned to inductively couple to the second magnetic field generator and the first magnetic flux sensor, the second loop portions of the first plurality of coupling loops alternating along the measuring axis with the second loop portions of the second plurality of coupling loops, the first plurality of coupling loop portions of the third plurality of coupling loops positioned to inductively couple to the third magnetic field generator, and the fourth magnetic flux sensor positioned to inductively couple to the second plurality of coupling loop portions of the third plurality of coupling loops.

20. An inductive absolute position sensor, comprising:

a first readhead member;

a second scale member having a measuring axis, the first readhead member and second scale member movable relative to each other along the measuring axis;

at least one magnetic field generator on the first readhead member, each at least one magnetic field generator responsive to a drive signal to generate a first changing magnetic flux in a first flux region;

second wavelength along the measuring axis, connecting conductors connecting the first coupling loop portion and the second coupling loop portion, every other one of the connecting conductors being twisted, the plurality of flux coupling loops responsive to the first changing magnetic flux in the first plurality of coupling loop portions to generate at least a second changing magnetic flux outside the first flux region in the second plurality of coupling loop portions;

at least one magnetic flux sensor positioned outside the first flux region and responsive to the second changing magnetic flux to generate an output signal that is a function of the relative position between the at least one magnetic flux sensor, and the plurality of flux coupling loops, the output signal of the at least one magnetic flux sensor varying at the second wavelength.

21. An inductive absolute position sensor, comprising:

a first readhead member;

a second scale member having a measuring axis, the first readhead member and second scale member movable relative to each other along the measuring axis;

at least one magnetic field generator on the first readhead member, each at least one magnetic field generator responsive to a drive signal to generate a first changing magnetic flux in a first flux region;

a first plurality of flux coupling loops and a second plurality of flux coupling loops on the second scale member, each having at least a first coupling loop portion and a second coupling loop portion, the first plurality of coupling loop portions spaced at an interval related to a first wavelength along the measuring axis and the second plurality of coupling loop portions spaced at an interval related to a second wavelength along the measuring axis, the plurality of flux coupling loops responsive to the first changing magnetic second coupling loop portion, the first plurality of coupling loop portions spaced at an interval related to a first wavelength along the measuring axis and the second plurality of coupling loop portions spaced at an interval related to a second wavelength along the measuring axis, the plurality of flux coupling loops responsive to the first changing magnetic flux in the first plurality of coupling loop portions to generate at least a second changing magnetic flux outside the first flux region in the second plurality of coupling loop portions;

at least one magnetic flux sensor positioned outside the first flux region and responsive to the second changing magnetic flux to generate an output signal that is a function of the relative position between the at least one magnetic flux sensor, and the plurality of flux coupling loops, the output signal of the at least one magnetic flux sensor varying at the second wavelength;

a second magnetic field generator;

first connecting conductors connecting the first coupling loop portion and the second coupling loop portion of the first plurality of flux coupling loops; and

second connecting conductors connecting the first coupling loop portion and the second coupling loop portion of the second plurality of flux coupling loops, every other one of the first connecting conductors being twisted and every other one of the second connecting conductors being twisted;

wherein the first magnetic flux generator is positioned to inductively couple to the first coupling loop portions of the first plurality of flux coupling loops, the magnetic flux sensor is positioned to inductively couple to the second coupling loop portions of the first plurality of flux coupling loops and the second coupling loop portions of the second plurality of flux coupling loops, and the second magnetic flux generator is positioned to inductively couple to the first coupling loop portions of the second plurality of flux coupling loops.